~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/kernel/sched/core.c

Version: ~ [ linux-4.20-rc6 ] ~ [ linux-4.19.8 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.87 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.144 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.166 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.128 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.61 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.31.14 ] ~ [ linux-2.6.30.10 ] ~ [ linux-2.6.29.6 ] ~ [ linux-2.6.28.10 ] ~ [ linux-2.6.27.62 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /*
  2  *  kernel/sched/core.c
  3  *
  4  *  Core kernel scheduler code and related syscalls
  5  *
  6  *  Copyright (C) 1991-2002  Linus Torvalds
  7  */
  8 #include "sched.h"
  9 
 10 #include <linux/nospec.h>
 11 
 12 #include <linux/kcov.h>
 13 
 14 #include <asm/switch_to.h>
 15 #include <asm/tlb.h>
 16 
 17 #include "../workqueue_internal.h"
 18 #include "../smpboot.h"
 19 
 20 #include "pelt.h"
 21 
 22 #define CREATE_TRACE_POINTS
 23 #include <trace/events/sched.h>
 24 
 25 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
 26 
 27 #if defined(CONFIG_SCHED_DEBUG) && defined(HAVE_JUMP_LABEL)
 28 /*
 29  * Debugging: various feature bits
 30  *
 31  * If SCHED_DEBUG is disabled, each compilation unit has its own copy of
 32  * sysctl_sched_features, defined in sched.h, to allow constants propagation
 33  * at compile time and compiler optimization based on features default.
 34  */
 35 #define SCHED_FEAT(name, enabled)       \
 36         (1UL << __SCHED_FEAT_##name) * enabled |
 37 const_debug unsigned int sysctl_sched_features =
 38 #include "features.h"
 39         0;
 40 #undef SCHED_FEAT
 41 #endif
 42 
 43 /*
 44  * Number of tasks to iterate in a single balance run.
 45  * Limited because this is done with IRQs disabled.
 46  */
 47 const_debug unsigned int sysctl_sched_nr_migrate = 32;
 48 
 49 /*
 50  * period over which we measure -rt task CPU usage in us.
 51  * default: 1s
 52  */
 53 unsigned int sysctl_sched_rt_period = 1000000;
 54 
 55 __read_mostly int scheduler_running;
 56 
 57 /*
 58  * part of the period that we allow rt tasks to run in us.
 59  * default: 0.95s
 60  */
 61 int sysctl_sched_rt_runtime = 950000;
 62 
 63 /*
 64  * __task_rq_lock - lock the rq @p resides on.
 65  */
 66 struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
 67         __acquires(rq->lock)
 68 {
 69         struct rq *rq;
 70 
 71         lockdep_assert_held(&p->pi_lock);
 72 
 73         for (;;) {
 74                 rq = task_rq(p);
 75                 raw_spin_lock(&rq->lock);
 76                 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
 77                         rq_pin_lock(rq, rf);
 78                         return rq;
 79                 }
 80                 raw_spin_unlock(&rq->lock);
 81 
 82                 while (unlikely(task_on_rq_migrating(p)))
 83                         cpu_relax();
 84         }
 85 }
 86 
 87 /*
 88  * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
 89  */
 90 struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
 91         __acquires(p->pi_lock)
 92         __acquires(rq->lock)
 93 {
 94         struct rq *rq;
 95 
 96         for (;;) {
 97                 raw_spin_lock_irqsave(&p->pi_lock, rf->flags);
 98                 rq = task_rq(p);
 99                 raw_spin_lock(&rq->lock);
100                 /*
101                  *      move_queued_task()              task_rq_lock()
102                  *
103                  *      ACQUIRE (rq->lock)
104                  *      [S] ->on_rq = MIGRATING         [L] rq = task_rq()
105                  *      WMB (__set_task_cpu())          ACQUIRE (rq->lock);
106                  *      [S] ->cpu = new_cpu             [L] task_rq()
107                  *                                      [L] ->on_rq
108                  *      RELEASE (rq->lock)
109                  *
110                  * If we observe the old CPU in task_rq_lock, the acquire of
111                  * the old rq->lock will fully serialize against the stores.
112                  *
113                  * If we observe the new CPU in task_rq_lock, the acquire will
114                  * pair with the WMB to ensure we must then also see migrating.
115                  */
116                 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
117                         rq_pin_lock(rq, rf);
118                         return rq;
119                 }
120                 raw_spin_unlock(&rq->lock);
121                 raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
122 
123                 while (unlikely(task_on_rq_migrating(p)))
124                         cpu_relax();
125         }
126 }
127 
128 /*
129  * RQ-clock updating methods:
130  */
131 
132 static void update_rq_clock_task(struct rq *rq, s64 delta)
133 {
134 /*
135  * In theory, the compile should just see 0 here, and optimize out the call
136  * to sched_rt_avg_update. But I don't trust it...
137  */
138         s64 __maybe_unused steal = 0, irq_delta = 0;
139 
140 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
141         irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
142 
143         /*
144          * Since irq_time is only updated on {soft,}irq_exit, we might run into
145          * this case when a previous update_rq_clock() happened inside a
146          * {soft,}irq region.
147          *
148          * When this happens, we stop ->clock_task and only update the
149          * prev_irq_time stamp to account for the part that fit, so that a next
150          * update will consume the rest. This ensures ->clock_task is
151          * monotonic.
152          *
153          * It does however cause some slight miss-attribution of {soft,}irq
154          * time, a more accurate solution would be to update the irq_time using
155          * the current rq->clock timestamp, except that would require using
156          * atomic ops.
157          */
158         if (irq_delta > delta)
159                 irq_delta = delta;
160 
161         rq->prev_irq_time += irq_delta;
162         delta -= irq_delta;
163 #endif
164 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
165         if (static_key_false((&paravirt_steal_rq_enabled))) {
166                 steal = paravirt_steal_clock(cpu_of(rq));
167                 steal -= rq->prev_steal_time_rq;
168 
169                 if (unlikely(steal > delta))
170                         steal = delta;
171 
172                 rq->prev_steal_time_rq += steal;
173                 delta -= steal;
174         }
175 #endif
176 
177         rq->clock_task += delta;
178 
179 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
180         if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY))
181                 update_irq_load_avg(rq, irq_delta + steal);
182 #endif
183 }
184 
185 void update_rq_clock(struct rq *rq)
186 {
187         s64 delta;
188 
189         lockdep_assert_held(&rq->lock);
190 
191         if (rq->clock_update_flags & RQCF_ACT_SKIP)
192                 return;
193 
194 #ifdef CONFIG_SCHED_DEBUG
195         if (sched_feat(WARN_DOUBLE_CLOCK))
196                 SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED);
197         rq->clock_update_flags |= RQCF_UPDATED;
198 #endif
199 
200         delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
201         if (delta < 0)
202                 return;
203         rq->clock += delta;
204         update_rq_clock_task(rq, delta);
205 }
206 
207 
208 #ifdef CONFIG_SCHED_HRTICK
209 /*
210  * Use HR-timers to deliver accurate preemption points.
211  */
212 
213 static void hrtick_clear(struct rq *rq)
214 {
215         if (hrtimer_active(&rq->hrtick_timer))
216                 hrtimer_cancel(&rq->hrtick_timer);
217 }
218 
219 /*
220  * High-resolution timer tick.
221  * Runs from hardirq context with interrupts disabled.
222  */
223 static enum hrtimer_restart hrtick(struct hrtimer *timer)
224 {
225         struct rq *rq = container_of(timer, struct rq, hrtick_timer);
226         struct rq_flags rf;
227 
228         WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
229 
230         rq_lock(rq, &rf);
231         update_rq_clock(rq);
232         rq->curr->sched_class->task_tick(rq, rq->curr, 1);
233         rq_unlock(rq, &rf);
234 
235         return HRTIMER_NORESTART;
236 }
237 
238 #ifdef CONFIG_SMP
239 
240 static void __hrtick_restart(struct rq *rq)
241 {
242         struct hrtimer *timer = &rq->hrtick_timer;
243 
244         hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED);
245 }
246 
247 /*
248  * called from hardirq (IPI) context
249  */
250 static void __hrtick_start(void *arg)
251 {
252         struct rq *rq = arg;
253         struct rq_flags rf;
254 
255         rq_lock(rq, &rf);
256         __hrtick_restart(rq);
257         rq->hrtick_csd_pending = 0;
258         rq_unlock(rq, &rf);
259 }
260 
261 /*
262  * Called to set the hrtick timer state.
263  *
264  * called with rq->lock held and irqs disabled
265  */
266 void hrtick_start(struct rq *rq, u64 delay)
267 {
268         struct hrtimer *timer = &rq->hrtick_timer;
269         ktime_t time;
270         s64 delta;
271 
272         /*
273          * Don't schedule slices shorter than 10000ns, that just
274          * doesn't make sense and can cause timer DoS.
275          */
276         delta = max_t(s64, delay, 10000LL);
277         time = ktime_add_ns(timer->base->get_time(), delta);
278 
279         hrtimer_set_expires(timer, time);
280 
281         if (rq == this_rq()) {
282                 __hrtick_restart(rq);
283         } else if (!rq->hrtick_csd_pending) {
284                 smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
285                 rq->hrtick_csd_pending = 1;
286         }
287 }
288 
289 #else
290 /*
291  * Called to set the hrtick timer state.
292  *
293  * called with rq->lock held and irqs disabled
294  */
295 void hrtick_start(struct rq *rq, u64 delay)
296 {
297         /*
298          * Don't schedule slices shorter than 10000ns, that just
299          * doesn't make sense. Rely on vruntime for fairness.
300          */
301         delay = max_t(u64, delay, 10000LL);
302         hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay),
303                       HRTIMER_MODE_REL_PINNED);
304 }
305 #endif /* CONFIG_SMP */
306 
307 static void hrtick_rq_init(struct rq *rq)
308 {
309 #ifdef CONFIG_SMP
310         rq->hrtick_csd_pending = 0;
311 
312         rq->hrtick_csd.flags = 0;
313         rq->hrtick_csd.func = __hrtick_start;
314         rq->hrtick_csd.info = rq;
315 #endif
316 
317         hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
318         rq->hrtick_timer.function = hrtick;
319 }
320 #else   /* CONFIG_SCHED_HRTICK */
321 static inline void hrtick_clear(struct rq *rq)
322 {
323 }
324 
325 static inline void hrtick_rq_init(struct rq *rq)
326 {
327 }
328 #endif  /* CONFIG_SCHED_HRTICK */
329 
330 /*
331  * cmpxchg based fetch_or, macro so it works for different integer types
332  */
333 #define fetch_or(ptr, mask)                                             \
334         ({                                                              \
335                 typeof(ptr) _ptr = (ptr);                               \
336                 typeof(mask) _mask = (mask);                            \
337                 typeof(*_ptr) _old, _val = *_ptr;                       \
338                                                                         \
339                 for (;;) {                                              \
340                         _old = cmpxchg(_ptr, _val, _val | _mask);       \
341                         if (_old == _val)                               \
342                                 break;                                  \
343                         _val = _old;                                    \
344                 }                                                       \
345         _old;                                                           \
346 })
347 
348 #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
349 /*
350  * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
351  * this avoids any races wrt polling state changes and thereby avoids
352  * spurious IPIs.
353  */
354 static bool set_nr_and_not_polling(struct task_struct *p)
355 {
356         struct thread_info *ti = task_thread_info(p);
357         return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
358 }
359 
360 /*
361  * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
362  *
363  * If this returns true, then the idle task promises to call
364  * sched_ttwu_pending() and reschedule soon.
365  */
366 static bool set_nr_if_polling(struct task_struct *p)
367 {
368         struct thread_info *ti = task_thread_info(p);
369         typeof(ti->flags) old, val = READ_ONCE(ti->flags);
370 
371         for (;;) {
372                 if (!(val & _TIF_POLLING_NRFLAG))
373                         return false;
374                 if (val & _TIF_NEED_RESCHED)
375                         return true;
376                 old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED);
377                 if (old == val)
378                         break;
379                 val = old;
380         }
381         return true;
382 }
383 
384 #else
385 static bool set_nr_and_not_polling(struct task_struct *p)
386 {
387         set_tsk_need_resched(p);
388         return true;
389 }
390 
391 #ifdef CONFIG_SMP
392 static bool set_nr_if_polling(struct task_struct *p)
393 {
394         return false;
395 }
396 #endif
397 #endif
398 
399 void wake_q_add(struct wake_q_head *head, struct task_struct *task)
400 {
401         struct wake_q_node *node = &task->wake_q;
402 
403         /*
404          * Atomically grab the task, if ->wake_q is !nil already it means
405          * its already queued (either by us or someone else) and will get the
406          * wakeup due to that.
407          *
408          * This cmpxchg() executes a full barrier, which pairs with the full
409          * barrier executed by the wakeup in wake_up_q().
410          */
411         if (cmpxchg(&node->next, NULL, WAKE_Q_TAIL))
412                 return;
413 
414         get_task_struct(task);
415 
416         /*
417          * The head is context local, there can be no concurrency.
418          */
419         *head->lastp = node;
420         head->lastp = &node->next;
421 }
422 
423 void wake_up_q(struct wake_q_head *head)
424 {
425         struct wake_q_node *node = head->first;
426 
427         while (node != WAKE_Q_TAIL) {
428                 struct task_struct *task;
429 
430                 task = container_of(node, struct task_struct, wake_q);
431                 BUG_ON(!task);
432                 /* Task can safely be re-inserted now: */
433                 node = node->next;
434                 task->wake_q.next = NULL;
435 
436                 /*
437                  * wake_up_process() executes a full barrier, which pairs with
438                  * the queueing in wake_q_add() so as not to miss wakeups.
439                  */
440                 wake_up_process(task);
441                 put_task_struct(task);
442         }
443 }
444 
445 /*
446  * resched_curr - mark rq's current task 'to be rescheduled now'.
447  *
448  * On UP this means the setting of the need_resched flag, on SMP it
449  * might also involve a cross-CPU call to trigger the scheduler on
450  * the target CPU.
451  */
452 void resched_curr(struct rq *rq)
453 {
454         struct task_struct *curr = rq->curr;
455         int cpu;
456 
457         lockdep_assert_held(&rq->lock);
458 
459         if (test_tsk_need_resched(curr))
460                 return;
461 
462         cpu = cpu_of(rq);
463 
464         if (cpu == smp_processor_id()) {
465                 set_tsk_need_resched(curr);
466                 set_preempt_need_resched();
467                 return;
468         }
469 
470         if (set_nr_and_not_polling(curr))
471                 smp_send_reschedule(cpu);
472         else
473                 trace_sched_wake_idle_without_ipi(cpu);
474 }
475 
476 void resched_cpu(int cpu)
477 {
478         struct rq *rq = cpu_rq(cpu);
479         unsigned long flags;
480 
481         raw_spin_lock_irqsave(&rq->lock, flags);
482         if (cpu_online(cpu) || cpu == smp_processor_id())
483                 resched_curr(rq);
484         raw_spin_unlock_irqrestore(&rq->lock, flags);
485 }
486 
487 #ifdef CONFIG_SMP
488 #ifdef CONFIG_NO_HZ_COMMON
489 /*
490  * In the semi idle case, use the nearest busy CPU for migrating timers
491  * from an idle CPU.  This is good for power-savings.
492  *
493  * We don't do similar optimization for completely idle system, as
494  * selecting an idle CPU will add more delays to the timers than intended
495  * (as that CPU's timer base may not be uptodate wrt jiffies etc).
496  */
497 int get_nohz_timer_target(void)
498 {
499         int i, cpu = smp_processor_id();
500         struct sched_domain *sd;
501 
502         if (!idle_cpu(cpu) && housekeeping_cpu(cpu, HK_FLAG_TIMER))
503                 return cpu;
504 
505         rcu_read_lock();
506         for_each_domain(cpu, sd) {
507                 for_each_cpu(i, sched_domain_span(sd)) {
508                         if (cpu == i)
509                                 continue;
510 
511                         if (!idle_cpu(i) && housekeeping_cpu(i, HK_FLAG_TIMER)) {
512                                 cpu = i;
513                                 goto unlock;
514                         }
515                 }
516         }
517 
518         if (!housekeeping_cpu(cpu, HK_FLAG_TIMER))
519                 cpu = housekeeping_any_cpu(HK_FLAG_TIMER);
520 unlock:
521         rcu_read_unlock();
522         return cpu;
523 }
524 
525 /*
526  * When add_timer_on() enqueues a timer into the timer wheel of an
527  * idle CPU then this timer might expire before the next timer event
528  * which is scheduled to wake up that CPU. In case of a completely
529  * idle system the next event might even be infinite time into the
530  * future. wake_up_idle_cpu() ensures that the CPU is woken up and
531  * leaves the inner idle loop so the newly added timer is taken into
532  * account when the CPU goes back to idle and evaluates the timer
533  * wheel for the next timer event.
534  */
535 static void wake_up_idle_cpu(int cpu)
536 {
537         struct rq *rq = cpu_rq(cpu);
538 
539         if (cpu == smp_processor_id())
540                 return;
541 
542         if (set_nr_and_not_polling(rq->idle))
543                 smp_send_reschedule(cpu);
544         else
545                 trace_sched_wake_idle_without_ipi(cpu);
546 }
547 
548 static bool wake_up_full_nohz_cpu(int cpu)
549 {
550         /*
551          * We just need the target to call irq_exit() and re-evaluate
552          * the next tick. The nohz full kick at least implies that.
553          * If needed we can still optimize that later with an
554          * empty IRQ.
555          */
556         if (cpu_is_offline(cpu))
557                 return true;  /* Don't try to wake offline CPUs. */
558         if (tick_nohz_full_cpu(cpu)) {
559                 if (cpu != smp_processor_id() ||
560                     tick_nohz_tick_stopped())
561                         tick_nohz_full_kick_cpu(cpu);
562                 return true;
563         }
564 
565         return false;
566 }
567 
568 /*
569  * Wake up the specified CPU.  If the CPU is going offline, it is the
570  * caller's responsibility to deal with the lost wakeup, for example,
571  * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
572  */
573 void wake_up_nohz_cpu(int cpu)
574 {
575         if (!wake_up_full_nohz_cpu(cpu))
576                 wake_up_idle_cpu(cpu);
577 }
578 
579 static inline bool got_nohz_idle_kick(void)
580 {
581         int cpu = smp_processor_id();
582 
583         if (!(atomic_read(nohz_flags(cpu)) & NOHZ_KICK_MASK))
584                 return false;
585 
586         if (idle_cpu(cpu) && !need_resched())
587                 return true;
588 
589         /*
590          * We can't run Idle Load Balance on this CPU for this time so we
591          * cancel it and clear NOHZ_BALANCE_KICK
592          */
593         atomic_andnot(NOHZ_KICK_MASK, nohz_flags(cpu));
594         return false;
595 }
596 
597 #else /* CONFIG_NO_HZ_COMMON */
598 
599 static inline bool got_nohz_idle_kick(void)
600 {
601         return false;
602 }
603 
604 #endif /* CONFIG_NO_HZ_COMMON */
605 
606 #ifdef CONFIG_NO_HZ_FULL
607 bool sched_can_stop_tick(struct rq *rq)
608 {
609         int fifo_nr_running;
610 
611         /* Deadline tasks, even if single, need the tick */
612         if (rq->dl.dl_nr_running)
613                 return false;
614 
615         /*
616          * If there are more than one RR tasks, we need the tick to effect the
617          * actual RR behaviour.
618          */
619         if (rq->rt.rr_nr_running) {
620                 if (rq->rt.rr_nr_running == 1)
621                         return true;
622                 else
623                         return false;
624         }
625 
626         /*
627          * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
628          * forced preemption between FIFO tasks.
629          */
630         fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;
631         if (fifo_nr_running)
632                 return true;
633 
634         /*
635          * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
636          * if there's more than one we need the tick for involuntary
637          * preemption.
638          */
639         if (rq->nr_running > 1)
640                 return false;
641 
642         return true;
643 }
644 #endif /* CONFIG_NO_HZ_FULL */
645 #endif /* CONFIG_SMP */
646 
647 #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
648                         (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
649 /*
650  * Iterate task_group tree rooted at *from, calling @down when first entering a
651  * node and @up when leaving it for the final time.
652  *
653  * Caller must hold rcu_lock or sufficient equivalent.
654  */
655 int walk_tg_tree_from(struct task_group *from,
656                              tg_visitor down, tg_visitor up, void *data)
657 {
658         struct task_group *parent, *child;
659         int ret;
660 
661         parent = from;
662 
663 down:
664         ret = (*down)(parent, data);
665         if (ret)
666                 goto out;
667         list_for_each_entry_rcu(child, &parent->children, siblings) {
668                 parent = child;
669                 goto down;
670 
671 up:
672                 continue;
673         }
674         ret = (*up)(parent, data);
675         if (ret || parent == from)
676                 goto out;
677 
678         child = parent;
679         parent = parent->parent;
680         if (parent)
681                 goto up;
682 out:
683         return ret;
684 }
685 
686 int tg_nop(struct task_group *tg, void *data)
687 {
688         return 0;
689 }
690 #endif
691 
692 static void set_load_weight(struct task_struct *p, bool update_load)
693 {
694         int prio = p->static_prio - MAX_RT_PRIO;
695         struct load_weight *load = &p->se.load;
696 
697         /*
698          * SCHED_IDLE tasks get minimal weight:
699          */
700         if (idle_policy(p->policy)) {
701                 load->weight = scale_load(WEIGHT_IDLEPRIO);
702                 load->inv_weight = WMULT_IDLEPRIO;
703                 p->se.runnable_weight = load->weight;
704                 return;
705         }
706 
707         /*
708          * SCHED_OTHER tasks have to update their load when changing their
709          * weight
710          */
711         if (update_load && p->sched_class == &fair_sched_class) {
712                 reweight_task(p, prio);
713         } else {
714                 load->weight = scale_load(sched_prio_to_weight[prio]);
715                 load->inv_weight = sched_prio_to_wmult[prio];
716                 p->se.runnable_weight = load->weight;
717         }
718 }
719 
720 static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
721 {
722         if (!(flags & ENQUEUE_NOCLOCK))
723                 update_rq_clock(rq);
724 
725         if (!(flags & ENQUEUE_RESTORE)) {
726                 sched_info_queued(rq, p);
727                 psi_enqueue(p, flags & ENQUEUE_WAKEUP);
728         }
729 
730         p->sched_class->enqueue_task(rq, p, flags);
731 }
732 
733 static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
734 {
735         if (!(flags & DEQUEUE_NOCLOCK))
736                 update_rq_clock(rq);
737 
738         if (!(flags & DEQUEUE_SAVE)) {
739                 sched_info_dequeued(rq, p);
740                 psi_dequeue(p, flags & DEQUEUE_SLEEP);
741         }
742 
743         p->sched_class->dequeue_task(rq, p, flags);
744 }
745 
746 void activate_task(struct rq *rq, struct task_struct *p, int flags)
747 {
748         if (task_contributes_to_load(p))
749                 rq->nr_uninterruptible--;
750 
751         enqueue_task(rq, p, flags);
752 }
753 
754 void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
755 {
756         if (task_contributes_to_load(p))
757                 rq->nr_uninterruptible++;
758 
759         dequeue_task(rq, p, flags);
760 }
761 
762 /*
763  * __normal_prio - return the priority that is based on the static prio
764  */
765 static inline int __normal_prio(struct task_struct *p)
766 {
767         return p->static_prio;
768 }
769 
770 /*
771  * Calculate the expected normal priority: i.e. priority
772  * without taking RT-inheritance into account. Might be
773  * boosted by interactivity modifiers. Changes upon fork,
774  * setprio syscalls, and whenever the interactivity
775  * estimator recalculates.
776  */
777 static inline int normal_prio(struct task_struct *p)
778 {
779         int prio;
780 
781         if (task_has_dl_policy(p))
782                 prio = MAX_DL_PRIO-1;
783         else if (task_has_rt_policy(p))
784                 prio = MAX_RT_PRIO-1 - p->rt_priority;
785         else
786                 prio = __normal_prio(p);
787         return prio;
788 }
789 
790 /*
791  * Calculate the current priority, i.e. the priority
792  * taken into account by the scheduler. This value might
793  * be boosted by RT tasks, or might be boosted by
794  * interactivity modifiers. Will be RT if the task got
795  * RT-boosted. If not then it returns p->normal_prio.
796  */
797 static int effective_prio(struct task_struct *p)
798 {
799         p->normal_prio = normal_prio(p);
800         /*
801          * If we are RT tasks or we were boosted to RT priority,
802          * keep the priority unchanged. Otherwise, update priority
803          * to the normal priority:
804          */
805         if (!rt_prio(p->prio))
806                 return p->normal_prio;
807         return p->prio;
808 }
809 
810 /**
811  * task_curr - is this task currently executing on a CPU?
812  * @p: the task in question.
813  *
814  * Return: 1 if the task is currently executing. 0 otherwise.
815  */
816 inline int task_curr(const struct task_struct *p)
817 {
818         return cpu_curr(task_cpu(p)) == p;
819 }
820 
821 /*
822  * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
823  * use the balance_callback list if you want balancing.
824  *
825  * this means any call to check_class_changed() must be followed by a call to
826  * balance_callback().
827  */
828 static inline void check_class_changed(struct rq *rq, struct task_struct *p,
829                                        const struct sched_class *prev_class,
830                                        int oldprio)
831 {
832         if (prev_class != p->sched_class) {
833                 if (prev_class->switched_from)
834                         prev_class->switched_from(rq, p);
835 
836                 p->sched_class->switched_to(rq, p);
837         } else if (oldprio != p->prio || dl_task(p))
838                 p->sched_class->prio_changed(rq, p, oldprio);
839 }
840 
841 void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
842 {
843         const struct sched_class *class;
844 
845         if (p->sched_class == rq->curr->sched_class) {
846                 rq->curr->sched_class->check_preempt_curr(rq, p, flags);
847         } else {
848                 for_each_class(class) {
849                         if (class == rq->curr->sched_class)
850                                 break;
851                         if (class == p->sched_class) {
852                                 resched_curr(rq);
853                                 break;
854                         }
855                 }
856         }
857 
858         /*
859          * A queue event has occurred, and we're going to schedule.  In
860          * this case, we can save a useless back to back clock update.
861          */
862         if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
863                 rq_clock_skip_update(rq);
864 }
865 
866 #ifdef CONFIG_SMP
867 
868 static inline bool is_per_cpu_kthread(struct task_struct *p)
869 {
870         if (!(p->flags & PF_KTHREAD))
871                 return false;
872 
873         if (p->nr_cpus_allowed != 1)
874                 return false;
875 
876         return true;
877 }
878 
879 /*
880  * Per-CPU kthreads are allowed to run on !actie && online CPUs, see
881  * __set_cpus_allowed_ptr() and select_fallback_rq().
882  */
883 static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
884 {
885         if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
886                 return false;
887 
888         if (is_per_cpu_kthread(p))
889                 return cpu_online(cpu);
890 
891         return cpu_active(cpu);
892 }
893 
894 /*
895  * This is how migration works:
896  *
897  * 1) we invoke migration_cpu_stop() on the target CPU using
898  *    stop_one_cpu().
899  * 2) stopper starts to run (implicitly forcing the migrated thread
900  *    off the CPU)
901  * 3) it checks whether the migrated task is still in the wrong runqueue.
902  * 4) if it's in the wrong runqueue then the migration thread removes
903  *    it and puts it into the right queue.
904  * 5) stopper completes and stop_one_cpu() returns and the migration
905  *    is done.
906  */
907 
908 /*
909  * move_queued_task - move a queued task to new rq.
910  *
911  * Returns (locked) new rq. Old rq's lock is released.
912  */
913 static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf,
914                                    struct task_struct *p, int new_cpu)
915 {
916         lockdep_assert_held(&rq->lock);
917 
918         p->on_rq = TASK_ON_RQ_MIGRATING;
919         dequeue_task(rq, p, DEQUEUE_NOCLOCK);
920         set_task_cpu(p, new_cpu);
921         rq_unlock(rq, rf);
922 
923         rq = cpu_rq(new_cpu);
924 
925         rq_lock(rq, rf);
926         BUG_ON(task_cpu(p) != new_cpu);
927         enqueue_task(rq, p, 0);
928         p->on_rq = TASK_ON_RQ_QUEUED;
929         check_preempt_curr(rq, p, 0);
930 
931         return rq;
932 }
933 
934 struct migration_arg {
935         struct task_struct *task;
936         int dest_cpu;
937 };
938 
939 /*
940  * Move (not current) task off this CPU, onto the destination CPU. We're doing
941  * this because either it can't run here any more (set_cpus_allowed()
942  * away from this CPU, or CPU going down), or because we're
943  * attempting to rebalance this task on exec (sched_exec).
944  *
945  * So we race with normal scheduler movements, but that's OK, as long
946  * as the task is no longer on this CPU.
947  */
948 static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf,
949                                  struct task_struct *p, int dest_cpu)
950 {
951         /* Affinity changed (again). */
952         if (!is_cpu_allowed(p, dest_cpu))
953                 return rq;
954 
955         update_rq_clock(rq);
956         rq = move_queued_task(rq, rf, p, dest_cpu);
957 
958         return rq;
959 }
960 
961 /*
962  * migration_cpu_stop - this will be executed by a highprio stopper thread
963  * and performs thread migration by bumping thread off CPU then
964  * 'pushing' onto another runqueue.
965  */
966 static int migration_cpu_stop(void *data)
967 {
968         struct migration_arg *arg = data;
969         struct task_struct *p = arg->task;
970         struct rq *rq = this_rq();
971         struct rq_flags rf;
972 
973         /*
974          * The original target CPU might have gone down and we might
975          * be on another CPU but it doesn't matter.
976          */
977         local_irq_disable();
978         /*
979          * We need to explicitly wake pending tasks before running
980          * __migrate_task() such that we will not miss enforcing cpus_allowed
981          * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
982          */
983         sched_ttwu_pending();
984 
985         raw_spin_lock(&p->pi_lock);
986         rq_lock(rq, &rf);
987         /*
988          * If task_rq(p) != rq, it cannot be migrated here, because we're
989          * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
990          * we're holding p->pi_lock.
991          */
992         if (task_rq(p) == rq) {
993                 if (task_on_rq_queued(p))
994                         rq = __migrate_task(rq, &rf, p, arg->dest_cpu);
995                 else
996                         p->wake_cpu = arg->dest_cpu;
997         }
998         rq_unlock(rq, &rf);
999         raw_spin_unlock(&p->pi_lock);
1000 
1001         local_irq_enable();
1002         return 0;
1003 }
1004 
1005 /*
1006  * sched_class::set_cpus_allowed must do the below, but is not required to
1007  * actually call this function.
1008  */
1009 void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask)
1010 {
1011         cpumask_copy(&p->cpus_allowed, new_mask);
1012         p->nr_cpus_allowed = cpumask_weight(new_mask);
1013 }
1014 
1015 void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
1016 {
1017         struct rq *rq = task_rq(p);
1018         bool queued, running;
1019 
1020         lockdep_assert_held(&p->pi_lock);
1021 
1022         queued = task_on_rq_queued(p);
1023         running = task_current(rq, p);
1024 
1025         if (queued) {
1026                 /*
1027                  * Because __kthread_bind() calls this on blocked tasks without
1028                  * holding rq->lock.
1029                  */
1030                 lockdep_assert_held(&rq->lock);
1031                 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
1032         }
1033         if (running)
1034                 put_prev_task(rq, p);
1035 
1036         p->sched_class->set_cpus_allowed(p, new_mask);
1037 
1038         if (queued)
1039                 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
1040         if (running)
1041                 set_curr_task(rq, p);
1042 }
1043 
1044 /*
1045  * Change a given task's CPU affinity. Migrate the thread to a
1046  * proper CPU and schedule it away if the CPU it's executing on
1047  * is removed from the allowed bitmask.
1048  *
1049  * NOTE: the caller must have a valid reference to the task, the
1050  * task must not exit() & deallocate itself prematurely. The
1051  * call is not atomic; no spinlocks may be held.
1052  */
1053 static int __set_cpus_allowed_ptr(struct task_struct *p,
1054                                   const struct cpumask *new_mask, bool check)
1055 {
1056         const struct cpumask *cpu_valid_mask = cpu_active_mask;
1057         unsigned int dest_cpu;
1058         struct rq_flags rf;
1059         struct rq *rq;
1060         int ret = 0;
1061 
1062         rq = task_rq_lock(p, &rf);
1063         update_rq_clock(rq);
1064 
1065         if (p->flags & PF_KTHREAD) {
1066                 /*
1067                  * Kernel threads are allowed on online && !active CPUs
1068                  */
1069                 cpu_valid_mask = cpu_online_mask;
1070         }
1071 
1072         /*
1073          * Must re-check here, to close a race against __kthread_bind(),
1074          * sched_setaffinity() is not guaranteed to observe the flag.
1075          */
1076         if (check && (p->flags & PF_NO_SETAFFINITY)) {
1077                 ret = -EINVAL;
1078                 goto out;
1079         }
1080 
1081         if (cpumask_equal(&p->cpus_allowed, new_mask))
1082                 goto out;
1083 
1084         if (!cpumask_intersects(new_mask, cpu_valid_mask)) {
1085                 ret = -EINVAL;
1086                 goto out;
1087         }
1088 
1089         do_set_cpus_allowed(p, new_mask);
1090 
1091         if (p->flags & PF_KTHREAD) {
1092                 /*
1093                  * For kernel threads that do indeed end up on online &&
1094                  * !active we want to ensure they are strict per-CPU threads.
1095                  */
1096                 WARN_ON(cpumask_intersects(new_mask, cpu_online_mask) &&
1097                         !cpumask_intersects(new_mask, cpu_active_mask) &&
1098                         p->nr_cpus_allowed != 1);
1099         }
1100 
1101         /* Can the task run on the task's current CPU? If so, we're done */
1102         if (cpumask_test_cpu(task_cpu(p), new_mask))
1103                 goto out;
1104 
1105         dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask);
1106         if (task_running(rq, p) || p->state == TASK_WAKING) {
1107                 struct migration_arg arg = { p, dest_cpu };
1108                 /* Need help from migration thread: drop lock and wait. */
1109                 task_rq_unlock(rq, p, &rf);
1110                 stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
1111                 tlb_migrate_finish(p->mm);
1112                 return 0;
1113         } else if (task_on_rq_queued(p)) {
1114                 /*
1115                  * OK, since we're going to drop the lock immediately
1116                  * afterwards anyway.
1117                  */
1118                 rq = move_queued_task(rq, &rf, p, dest_cpu);
1119         }
1120 out:
1121         task_rq_unlock(rq, p, &rf);
1122 
1123         return ret;
1124 }
1125 
1126 int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
1127 {
1128         return __set_cpus_allowed_ptr(p, new_mask, false);
1129 }
1130 EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
1131 
1132 void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
1133 {
1134 #ifdef CONFIG_SCHED_DEBUG
1135         /*
1136          * We should never call set_task_cpu() on a blocked task,
1137          * ttwu() will sort out the placement.
1138          */
1139         WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
1140                         !p->on_rq);
1141 
1142         /*
1143          * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
1144          * because schedstat_wait_{start,end} rebase migrating task's wait_start
1145          * time relying on p->on_rq.
1146          */
1147         WARN_ON_ONCE(p->state == TASK_RUNNING &&
1148                      p->sched_class == &fair_sched_class &&
1149                      (p->on_rq && !task_on_rq_migrating(p)));
1150 
1151 #ifdef CONFIG_LOCKDEP
1152         /*
1153          * The caller should hold either p->pi_lock or rq->lock, when changing
1154          * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
1155          *
1156          * sched_move_task() holds both and thus holding either pins the cgroup,
1157          * see task_group().
1158          *
1159          * Furthermore, all task_rq users should acquire both locks, see
1160          * task_rq_lock().
1161          */
1162         WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
1163                                       lockdep_is_held(&task_rq(p)->lock)));
1164 #endif
1165         /*
1166          * Clearly, migrating tasks to offline CPUs is a fairly daft thing.
1167          */
1168         WARN_ON_ONCE(!cpu_online(new_cpu));
1169 #endif
1170 
1171         trace_sched_migrate_task(p, new_cpu);
1172 
1173         if (task_cpu(p) != new_cpu) {
1174                 if (p->sched_class->migrate_task_rq)
1175                         p->sched_class->migrate_task_rq(p, new_cpu);
1176                 p->se.nr_migrations++;
1177                 rseq_migrate(p);
1178                 perf_event_task_migrate(p);
1179         }
1180 
1181         __set_task_cpu(p, new_cpu);
1182 }
1183 
1184 #ifdef CONFIG_NUMA_BALANCING
1185 static void __migrate_swap_task(struct task_struct *p, int cpu)
1186 {
1187         if (task_on_rq_queued(p)) {
1188                 struct rq *src_rq, *dst_rq;
1189                 struct rq_flags srf, drf;
1190 
1191                 src_rq = task_rq(p);
1192                 dst_rq = cpu_rq(cpu);
1193 
1194                 rq_pin_lock(src_rq, &srf);
1195                 rq_pin_lock(dst_rq, &drf);
1196 
1197                 p->on_rq = TASK_ON_RQ_MIGRATING;
1198                 deactivate_task(src_rq, p, 0);
1199                 set_task_cpu(p, cpu);
1200                 activate_task(dst_rq, p, 0);
1201                 p->on_rq = TASK_ON_RQ_QUEUED;
1202                 check_preempt_curr(dst_rq, p, 0);
1203 
1204                 rq_unpin_lock(dst_rq, &drf);
1205                 rq_unpin_lock(src_rq, &srf);
1206 
1207         } else {
1208                 /*
1209                  * Task isn't running anymore; make it appear like we migrated
1210                  * it before it went to sleep. This means on wakeup we make the
1211                  * previous CPU our target instead of where it really is.
1212                  */
1213                 p->wake_cpu = cpu;
1214         }
1215 }
1216 
1217 struct migration_swap_arg {
1218         struct task_struct *src_task, *dst_task;
1219         int src_cpu, dst_cpu;
1220 };
1221 
1222 static int migrate_swap_stop(void *data)
1223 {
1224         struct migration_swap_arg *arg = data;
1225         struct rq *src_rq, *dst_rq;
1226         int ret = -EAGAIN;
1227 
1228         if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu))
1229                 return -EAGAIN;
1230 
1231         src_rq = cpu_rq(arg->src_cpu);
1232         dst_rq = cpu_rq(arg->dst_cpu);
1233 
1234         double_raw_lock(&arg->src_task->pi_lock,
1235                         &arg->dst_task->pi_lock);
1236         double_rq_lock(src_rq, dst_rq);
1237 
1238         if (task_cpu(arg->dst_task) != arg->dst_cpu)
1239                 goto unlock;
1240 
1241         if (task_cpu(arg->src_task) != arg->src_cpu)
1242                 goto unlock;
1243 
1244         if (!cpumask_test_cpu(arg->dst_cpu, &arg->src_task->cpus_allowed))
1245                 goto unlock;
1246 
1247         if (!cpumask_test_cpu(arg->src_cpu, &arg->dst_task->cpus_allowed))
1248                 goto unlock;
1249 
1250         __migrate_swap_task(arg->src_task, arg->dst_cpu);
1251         __migrate_swap_task(arg->dst_task, arg->src_cpu);
1252 
1253         ret = 0;
1254 
1255 unlock:
1256         double_rq_unlock(src_rq, dst_rq);
1257         raw_spin_unlock(&arg->dst_task->pi_lock);
1258         raw_spin_unlock(&arg->src_task->pi_lock);
1259 
1260         return ret;
1261 }
1262 
1263 /*
1264  * Cross migrate two tasks
1265  */
1266 int migrate_swap(struct task_struct *cur, struct task_struct *p,
1267                 int target_cpu, int curr_cpu)
1268 {
1269         struct migration_swap_arg arg;
1270         int ret = -EINVAL;
1271 
1272         arg = (struct migration_swap_arg){
1273                 .src_task = cur,
1274                 .src_cpu = curr_cpu,
1275                 .dst_task = p,
1276                 .dst_cpu = target_cpu,
1277         };
1278 
1279         if (arg.src_cpu == arg.dst_cpu)
1280                 goto out;
1281 
1282         /*
1283          * These three tests are all lockless; this is OK since all of them
1284          * will be re-checked with proper locks held further down the line.
1285          */
1286         if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu))
1287                 goto out;
1288 
1289         if (!cpumask_test_cpu(arg.dst_cpu, &arg.src_task->cpus_allowed))
1290                 goto out;
1291 
1292         if (!cpumask_test_cpu(arg.src_cpu, &arg.dst_task->cpus_allowed))
1293                 goto out;
1294 
1295         trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
1296         ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);
1297 
1298 out:
1299         return ret;
1300 }
1301 #endif /* CONFIG_NUMA_BALANCING */
1302 
1303 /*
1304  * wait_task_inactive - wait for a thread to unschedule.
1305  *
1306  * If @match_state is nonzero, it's the @p->state value just checked and
1307  * not expected to change.  If it changes, i.e. @p might have woken up,
1308  * then return zero.  When we succeed in waiting for @p to be off its CPU,
1309  * we return a positive number (its total switch count).  If a second call
1310  * a short while later returns the same number, the caller can be sure that
1311  * @p has remained unscheduled the whole time.
1312  *
1313  * The caller must ensure that the task *will* unschedule sometime soon,
1314  * else this function might spin for a *long* time. This function can't
1315  * be called with interrupts off, or it may introduce deadlock with
1316  * smp_call_function() if an IPI is sent by the same process we are
1317  * waiting to become inactive.
1318  */
1319 unsigned long wait_task_inactive(struct task_struct *p, long match_state)
1320 {
1321         int running, queued;
1322         struct rq_flags rf;
1323         unsigned long ncsw;
1324         struct rq *rq;
1325 
1326         for (;;) {
1327                 /*
1328                  * We do the initial early heuristics without holding
1329                  * any task-queue locks at all. We'll only try to get
1330                  * the runqueue lock when things look like they will
1331                  * work out!
1332                  */
1333                 rq = task_rq(p);
1334 
1335                 /*
1336                  * If the task is actively running on another CPU
1337                  * still, just relax and busy-wait without holding
1338                  * any locks.
1339                  *
1340                  * NOTE! Since we don't hold any locks, it's not
1341                  * even sure that "rq" stays as the right runqueue!
1342                  * But we don't care, since "task_running()" will
1343                  * return false if the runqueue has changed and p
1344                  * is actually now running somewhere else!
1345                  */
1346                 while (task_running(rq, p)) {
1347                         if (match_state && unlikely(p->state != match_state))
1348                                 return 0;
1349                         cpu_relax();
1350                 }
1351 
1352                 /*
1353                  * Ok, time to look more closely! We need the rq
1354                  * lock now, to be *sure*. If we're wrong, we'll
1355                  * just go back and repeat.
1356                  */
1357                 rq = task_rq_lock(p, &rf);
1358                 trace_sched_wait_task(p);
1359                 running = task_running(rq, p);
1360                 queued = task_on_rq_queued(p);
1361                 ncsw = 0;
1362                 if (!match_state || p->state == match_state)
1363                         ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
1364                 task_rq_unlock(rq, p, &rf);
1365 
1366                 /*
1367                  * If it changed from the expected state, bail out now.
1368                  */
1369                 if (unlikely(!ncsw))
1370                         break;
1371 
1372                 /*
1373                  * Was it really running after all now that we
1374                  * checked with the proper locks actually held?
1375                  *
1376                  * Oops. Go back and try again..
1377                  */
1378                 if (unlikely(running)) {
1379                         cpu_relax();
1380                         continue;
1381                 }
1382 
1383                 /*
1384                  * It's not enough that it's not actively running,
1385                  * it must be off the runqueue _entirely_, and not
1386                  * preempted!
1387                  *
1388                  * So if it was still runnable (but just not actively
1389                  * running right now), it's preempted, and we should
1390                  * yield - it could be a while.
1391                  */
1392                 if (unlikely(queued)) {
1393                         ktime_t to = NSEC_PER_SEC / HZ;
1394 
1395                         set_current_state(TASK_UNINTERRUPTIBLE);
1396                         schedule_hrtimeout(&to, HRTIMER_MODE_REL);
1397                         continue;
1398                 }
1399 
1400                 /*
1401                  * Ahh, all good. It wasn't running, and it wasn't
1402                  * runnable, which means that it will never become
1403                  * running in the future either. We're all done!
1404                  */
1405                 break;
1406         }
1407 
1408         return ncsw;
1409 }
1410 
1411 /***
1412  * kick_process - kick a running thread to enter/exit the kernel
1413  * @p: the to-be-kicked thread
1414  *
1415  * Cause a process which is running on another CPU to enter
1416  * kernel-mode, without any delay. (to get signals handled.)
1417  *
1418  * NOTE: this function doesn't have to take the runqueue lock,
1419  * because all it wants to ensure is that the remote task enters
1420  * the kernel. If the IPI races and the task has been migrated
1421  * to another CPU then no harm is done and the purpose has been
1422  * achieved as well.
1423  */
1424 void kick_process(struct task_struct *p)
1425 {
1426         int cpu;
1427 
1428         preempt_disable();
1429         cpu = task_cpu(p);
1430         if ((cpu != smp_processor_id()) && task_curr(p))
1431                 smp_send_reschedule(cpu);
1432         preempt_enable();
1433 }
1434 EXPORT_SYMBOL_GPL(kick_process);
1435 
1436 /*
1437  * ->cpus_allowed is protected by both rq->lock and p->pi_lock
1438  *
1439  * A few notes on cpu_active vs cpu_online:
1440  *
1441  *  - cpu_active must be a subset of cpu_online
1442  *
1443  *  - on CPU-up we allow per-CPU kthreads on the online && !active CPU,
1444  *    see __set_cpus_allowed_ptr(). At this point the newly online
1445  *    CPU isn't yet part of the sched domains, and balancing will not
1446  *    see it.
1447  *
1448  *  - on CPU-down we clear cpu_active() to mask the sched domains and
1449  *    avoid the load balancer to place new tasks on the to be removed
1450  *    CPU. Existing tasks will remain running there and will be taken
1451  *    off.
1452  *
1453  * This means that fallback selection must not select !active CPUs.
1454  * And can assume that any active CPU must be online. Conversely
1455  * select_task_rq() below may allow selection of !active CPUs in order
1456  * to satisfy the above rules.
1457  */
1458 static int select_fallback_rq(int cpu, struct task_struct *p)
1459 {
1460         int nid = cpu_to_node(cpu);
1461         const struct cpumask *nodemask = NULL;
1462         enum { cpuset, possible, fail } state = cpuset;
1463         int dest_cpu;
1464 
1465         /*
1466          * If the node that the CPU is on has been offlined, cpu_to_node()
1467          * will return -1. There is no CPU on the node, and we should
1468          * select the CPU on the other node.
1469          */
1470         if (nid != -1) {
1471                 nodemask = cpumask_of_node(nid);
1472 
1473                 /* Look for allowed, online CPU in same node. */
1474                 for_each_cpu(dest_cpu, nodemask) {
1475                         if (!cpu_active(dest_cpu))
1476                                 continue;
1477                         if (cpumask_test_cpu(dest_cpu, &p->cpus_allowed))
1478                                 return dest_cpu;
1479                 }
1480         }
1481 
1482         for (;;) {
1483                 /* Any allowed, online CPU? */
1484                 for_each_cpu(dest_cpu, &p->cpus_allowed) {
1485                         if (!is_cpu_allowed(p, dest_cpu))
1486                                 continue;
1487 
1488                         goto out;
1489                 }
1490 
1491                 /* No more Mr. Nice Guy. */
1492                 switch (state) {
1493                 case cpuset:
1494                         if (IS_ENABLED(CONFIG_CPUSETS)) {
1495                                 cpuset_cpus_allowed_fallback(p);
1496                                 state = possible;
1497                                 break;
1498                         }
1499                         /* Fall-through */
1500                 case possible:
1501                         do_set_cpus_allowed(p, cpu_possible_mask);
1502                         state = fail;
1503                         break;
1504 
1505                 case fail:
1506                         BUG();
1507                         break;
1508                 }
1509         }
1510 
1511 out:
1512         if (state != cpuset) {
1513                 /*
1514                  * Don't tell them about moving exiting tasks or
1515                  * kernel threads (both mm NULL), since they never
1516                  * leave kernel.
1517                  */
1518                 if (p->mm && printk_ratelimit()) {
1519                         printk_deferred("process %d (%s) no longer affine to cpu%d\n",
1520                                         task_pid_nr(p), p->comm, cpu);
1521                 }
1522         }
1523 
1524         return dest_cpu;
1525 }
1526 
1527 /*
1528  * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable.
1529  */
1530 static inline
1531 int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags)
1532 {
1533         lockdep_assert_held(&p->pi_lock);
1534 
1535         if (p->nr_cpus_allowed > 1)
1536                 cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags);
1537         else
1538                 cpu = cpumask_any(&p->cpus_allowed);
1539 
1540         /*
1541          * In order not to call set_task_cpu() on a blocking task we need
1542          * to rely on ttwu() to place the task on a valid ->cpus_allowed
1543          * CPU.
1544          *
1545          * Since this is common to all placement strategies, this lives here.
1546          *
1547          * [ this allows ->select_task() to simply return task_cpu(p) and
1548          *   not worry about this generic constraint ]
1549          */
1550         if (unlikely(!is_cpu_allowed(p, cpu)))
1551                 cpu = select_fallback_rq(task_cpu(p), p);
1552 
1553         return cpu;
1554 }
1555 
1556 static void update_avg(u64 *avg, u64 sample)
1557 {
1558         s64 diff = sample - *avg;
1559         *avg += diff >> 3;
1560 }
1561 
1562 void sched_set_stop_task(int cpu, struct task_struct *stop)
1563 {
1564         struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
1565         struct task_struct *old_stop = cpu_rq(cpu)->stop;
1566 
1567         if (stop) {
1568                 /*
1569                  * Make it appear like a SCHED_FIFO task, its something
1570                  * userspace knows about and won't get confused about.
1571                  *
1572                  * Also, it will make PI more or less work without too
1573                  * much confusion -- but then, stop work should not
1574                  * rely on PI working anyway.
1575                  */
1576                 sched_setscheduler_nocheck(stop, SCHED_FIFO, &param);
1577 
1578                 stop->sched_class = &stop_sched_class;
1579         }
1580 
1581         cpu_rq(cpu)->stop = stop;
1582 
1583         if (old_stop) {
1584                 /*
1585                  * Reset it back to a normal scheduling class so that
1586                  * it can die in pieces.
1587                  */
1588                 old_stop->sched_class = &rt_sched_class;
1589         }
1590 }
1591 
1592 #else
1593 
1594 static inline int __set_cpus_allowed_ptr(struct task_struct *p,
1595                                          const struct cpumask *new_mask, bool check)
1596 {
1597         return set_cpus_allowed_ptr(p, new_mask);
1598 }
1599 
1600 #endif /* CONFIG_SMP */
1601 
1602 static void
1603 ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
1604 {
1605         struct rq *rq;
1606 
1607         if (!schedstat_enabled())
1608                 return;
1609 
1610         rq = this_rq();
1611 
1612 #ifdef CONFIG_SMP
1613         if (cpu == rq->cpu) {
1614                 __schedstat_inc(rq->ttwu_local);
1615                 __schedstat_inc(p->se.statistics.nr_wakeups_local);
1616         } else {
1617                 struct sched_domain *sd;
1618 
1619                 __schedstat_inc(p->se.statistics.nr_wakeups_remote);
1620                 rcu_read_lock();
1621                 for_each_domain(rq->cpu, sd) {
1622                         if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
1623                                 __schedstat_inc(sd->ttwu_wake_remote);
1624                                 break;
1625                         }
1626                 }
1627                 rcu_read_unlock();
1628         }
1629 
1630         if (wake_flags & WF_MIGRATED)
1631                 __schedstat_inc(p->se.statistics.nr_wakeups_migrate);
1632 #endif /* CONFIG_SMP */
1633 
1634         __schedstat_inc(rq->ttwu_count);
1635         __schedstat_inc(p->se.statistics.nr_wakeups);
1636 
1637         if (wake_flags & WF_SYNC)
1638                 __schedstat_inc(p->se.statistics.nr_wakeups_sync);
1639 }
1640 
1641 static inline void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
1642 {
1643         activate_task(rq, p, en_flags);
1644         p->on_rq = TASK_ON_RQ_QUEUED;
1645 
1646         /* If a worker is waking up, notify the workqueue: */
1647         if (p->flags & PF_WQ_WORKER)
1648                 wq_worker_waking_up(p, cpu_of(rq));
1649 }
1650 
1651 /*
1652  * Mark the task runnable and perform wakeup-preemption.
1653  */
1654 static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags,
1655                            struct rq_flags *rf)
1656 {
1657         check_preempt_curr(rq, p, wake_flags);
1658         p->state = TASK_RUNNING;
1659         trace_sched_wakeup(p);
1660 
1661 #ifdef CONFIG_SMP
1662         if (p->sched_class->task_woken) {
1663                 /*
1664                  * Our task @p is fully woken up and running; so its safe to
1665                  * drop the rq->lock, hereafter rq is only used for statistics.
1666                  */
1667                 rq_unpin_lock(rq, rf);
1668                 p->sched_class->task_woken(rq, p);
1669                 rq_repin_lock(rq, rf);
1670         }
1671 
1672         if (rq->idle_stamp) {
1673                 u64 delta = rq_clock(rq) - rq->idle_stamp;
1674                 u64 max = 2*rq->max_idle_balance_cost;
1675 
1676                 update_avg(&rq->avg_idle, delta);
1677 
1678                 if (rq->avg_idle > max)
1679                         rq->avg_idle = max;
1680 
1681                 rq->idle_stamp = 0;
1682         }
1683 #endif
1684 }
1685 
1686 static void
1687 ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
1688                  struct rq_flags *rf)
1689 {
1690         int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK;
1691 
1692         lockdep_assert_held(&rq->lock);
1693 
1694 #ifdef CONFIG_SMP
1695         if (p->sched_contributes_to_load)
1696                 rq->nr_uninterruptible--;
1697 
1698         if (wake_flags & WF_MIGRATED)
1699                 en_flags |= ENQUEUE_MIGRATED;
1700 #endif
1701 
1702         ttwu_activate(rq, p, en_flags);
1703         ttwu_do_wakeup(rq, p, wake_flags, rf);
1704 }
1705 
1706 /*
1707  * Called in case the task @p isn't fully descheduled from its runqueue,
1708  * in this case we must do a remote wakeup. Its a 'light' wakeup though,
1709  * since all we need to do is flip p->state to TASK_RUNNING, since
1710  * the task is still ->on_rq.
1711  */
1712 static int ttwu_remote(struct task_struct *p, int wake_flags)
1713 {
1714         struct rq_flags rf;
1715         struct rq *rq;
1716         int ret = 0;
1717 
1718         rq = __task_rq_lock(p, &rf);
1719         if (task_on_rq_queued(p)) {
1720                 /* check_preempt_curr() may use rq clock */
1721                 update_rq_clock(rq);
1722                 ttwu_do_wakeup(rq, p, wake_flags, &rf);
1723                 ret = 1;
1724         }
1725         __task_rq_unlock(rq, &rf);
1726 
1727         return ret;
1728 }
1729 
1730 #ifdef CONFIG_SMP
1731 void sched_ttwu_pending(void)
1732 {
1733         struct rq *rq = this_rq();
1734         struct llist_node *llist = llist_del_all(&rq->wake_list);
1735         struct task_struct *p, *t;
1736         struct rq_flags rf;
1737 
1738         if (!llist)
1739                 return;
1740 
1741         rq_lock_irqsave(rq, &rf);
1742         update_rq_clock(rq);
1743 
1744         llist_for_each_entry_safe(p, t, llist, wake_entry)
1745                 ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf);
1746 
1747         rq_unlock_irqrestore(rq, &rf);
1748 }
1749 
1750 void scheduler_ipi(void)
1751 {
1752         /*
1753          * Fold TIF_NEED_RESCHED into the preempt_count; anybody setting
1754          * TIF_NEED_RESCHED remotely (for the first time) will also send
1755          * this IPI.
1756          */
1757         preempt_fold_need_resched();
1758 
1759         if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick())
1760                 return;
1761 
1762         /*
1763          * Not all reschedule IPI handlers call irq_enter/irq_exit, since
1764          * traditionally all their work was done from the interrupt return
1765          * path. Now that we actually do some work, we need to make sure
1766          * we do call them.
1767          *
1768          * Some archs already do call them, luckily irq_enter/exit nest
1769          * properly.
1770          *
1771          * Arguably we should visit all archs and update all handlers,
1772          * however a fair share of IPIs are still resched only so this would
1773          * somewhat pessimize the simple resched case.
1774          */
1775         irq_enter();
1776         sched_ttwu_pending();
1777 
1778         /*
1779          * Check if someone kicked us for doing the nohz idle load balance.
1780          */
1781         if (unlikely(got_nohz_idle_kick())) {
1782                 this_rq()->idle_balance = 1;
1783                 raise_softirq_irqoff(SCHED_SOFTIRQ);
1784         }
1785         irq_exit();
1786 }
1787 
1788 static void ttwu_queue_remote(struct task_struct *p, int cpu, int wake_flags)
1789 {
1790         struct rq *rq = cpu_rq(cpu);
1791 
1792         p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED);
1793 
1794         if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) {
1795                 if (!set_nr_if_polling(rq->idle))
1796                         smp_send_reschedule(cpu);
1797                 else
1798                         trace_sched_wake_idle_without_ipi(cpu);
1799         }
1800 }
1801 
1802 void wake_up_if_idle(int cpu)
1803 {
1804         struct rq *rq = cpu_rq(cpu);
1805         struct rq_flags rf;
1806 
1807         rcu_read_lock();
1808 
1809         if (!is_idle_task(rcu_dereference(rq->curr)))
1810                 goto out;
1811 
1812         if (set_nr_if_polling(rq->idle)) {
1813                 trace_sched_wake_idle_without_ipi(cpu);
1814         } else {
1815                 rq_lock_irqsave(rq, &rf);
1816                 if (is_idle_task(rq->curr))
1817                         smp_send_reschedule(cpu);
1818                 /* Else CPU is not idle, do nothing here: */
1819                 rq_unlock_irqrestore(rq, &rf);
1820         }
1821 
1822 out:
1823         rcu_read_unlock();
1824 }
1825 
1826 bool cpus_share_cache(int this_cpu, int that_cpu)
1827 {
1828         return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
1829 }
1830 #endif /* CONFIG_SMP */
1831 
1832 static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
1833 {
1834         struct rq *rq = cpu_rq(cpu);
1835         struct rq_flags rf;
1836 
1837 #if defined(CONFIG_SMP)
1838         if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) {
1839                 sched_clock_cpu(cpu); /* Sync clocks across CPUs */
1840                 ttwu_queue_remote(p, cpu, wake_flags);
1841                 return;
1842         }
1843 #endif
1844 
1845         rq_lock(rq, &rf);
1846         update_rq_clock(rq);
1847         ttwu_do_activate(rq, p, wake_flags, &rf);
1848         rq_unlock(rq, &rf);
1849 }
1850 
1851 /*
1852  * Notes on Program-Order guarantees on SMP systems.
1853  *
1854  *  MIGRATION
1855  *
1856  * The basic program-order guarantee on SMP systems is that when a task [t]
1857  * migrates, all its activity on its old CPU [c0] happens-before any subsequent
1858  * execution on its new CPU [c1].
1859  *
1860  * For migration (of runnable tasks) this is provided by the following means:
1861  *
1862  *  A) UNLOCK of the rq(c0)->lock scheduling out task t
1863  *  B) migration for t is required to synchronize *both* rq(c0)->lock and
1864  *     rq(c1)->lock (if not at the same time, then in that order).
1865  *  C) LOCK of the rq(c1)->lock scheduling in task
1866  *
1867  * Release/acquire chaining guarantees that B happens after A and C after B.
1868  * Note: the CPU doing B need not be c0 or c1
1869  *
1870  * Example:
1871  *
1872  *   CPU0            CPU1            CPU2
1873  *
1874  *   LOCK rq(0)->lock
1875  *   sched-out X
1876  *   sched-in Y
1877  *   UNLOCK rq(0)->lock
1878  *
1879  *                                   LOCK rq(0)->lock // orders against CPU0
1880  *                                   dequeue X
1881  *                                   UNLOCK rq(0)->lock
1882  *
1883  *                                   LOCK rq(1)->lock
1884  *                                   enqueue X
1885  *                                   UNLOCK rq(1)->lock
1886  *
1887  *                   LOCK rq(1)->lock // orders against CPU2
1888  *                   sched-out Z
1889  *                   sched-in X
1890  *                   UNLOCK rq(1)->lock
1891  *
1892  *
1893  *  BLOCKING -- aka. SLEEP + WAKEUP
1894  *
1895  * For blocking we (obviously) need to provide the same guarantee as for
1896  * migration. However the means are completely different as there is no lock
1897  * chain to provide order. Instead we do:
1898  *
1899  *   1) smp_store_release(X->on_cpu, 0)
1900  *   2) smp_cond_load_acquire(!X->on_cpu)
1901  *
1902  * Example:
1903  *
1904  *   CPU0 (schedule)  CPU1 (try_to_wake_up) CPU2 (schedule)
1905  *
1906  *   LOCK rq(0)->lock LOCK X->pi_lock
1907  *   dequeue X
1908  *   sched-out X
1909  *   smp_store_release(X->on_cpu, 0);
1910  *
1911  *                    smp_cond_load_acquire(&X->on_cpu, !VAL);
1912  *                    X->state = WAKING
1913  *                    set_task_cpu(X,2)
1914  *
1915  *                    LOCK rq(2)->lock
1916  *                    enqueue X
1917  *                    X->state = RUNNING
1918  *                    UNLOCK rq(2)->lock
1919  *
1920  *                                          LOCK rq(2)->lock // orders against CPU1
1921  *                                          sched-out Z
1922  *                                          sched-in X
1923  *                                          UNLOCK rq(2)->lock
1924  *
1925  *                    UNLOCK X->pi_lock
1926  *   UNLOCK rq(0)->lock
1927  *
1928  *
1929  * However, for wakeups there is a second guarantee we must provide, namely we
1930  * must ensure that CONDITION=1 done by the caller can not be reordered with
1931  * accesses to the task state; see try_to_wake_up() and set_current_state().
1932  */
1933 
1934 /**
1935  * try_to_wake_up - wake up a thread
1936  * @p: the thread to be awakened
1937  * @state: the mask of task states that can be woken
1938  * @wake_flags: wake modifier flags (WF_*)
1939  *
1940  * If (@state & @p->state) @p->state = TASK_RUNNING.
1941  *
1942  * If the task was not queued/runnable, also place it back on a runqueue.
1943  *
1944  * Atomic against schedule() which would dequeue a task, also see
1945  * set_current_state().
1946  *
1947  * This function executes a full memory barrier before accessing the task
1948  * state; see set_current_state().
1949  *
1950  * Return: %true if @p->state changes (an actual wakeup was done),
1951  *         %false otherwise.
1952  */
1953 static int
1954 try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
1955 {
1956         unsigned long flags;
1957         int cpu, success = 0;
1958 
1959         /*
1960          * If we are going to wake up a thread waiting for CONDITION we
1961          * need to ensure that CONDITION=1 done by the caller can not be
1962          * reordered with p->state check below. This pairs with mb() in
1963          * set_current_state() the waiting thread does.
1964          */
1965         raw_spin_lock_irqsave(&p->pi_lock, flags);
1966         smp_mb__after_spinlock();
1967         if (!(p->state & state))
1968                 goto out;
1969 
1970         trace_sched_waking(p);
1971 
1972         /* We're going to change ->state: */
1973         success = 1;
1974         cpu = task_cpu(p);
1975 
1976         /*
1977          * Ensure we load p->on_rq _after_ p->state, otherwise it would
1978          * be possible to, falsely, observe p->on_rq == 0 and get stuck
1979          * in smp_cond_load_acquire() below.
1980          *
1981          * sched_ttwu_pending()                 try_to_wake_up()
1982          *   STORE p->on_rq = 1                   LOAD p->state
1983          *   UNLOCK rq->lock
1984          *
1985          * __schedule() (switch to task 'p')
1986          *   LOCK rq->lock                        smp_rmb();
1987          *   smp_mb__after_spinlock();
1988          *   UNLOCK rq->lock
1989          *
1990          * [task p]
1991          *   STORE p->state = UNINTERRUPTIBLE     LOAD p->on_rq
1992          *
1993          * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
1994          * __schedule().  See the comment for smp_mb__after_spinlock().
1995          */
1996         smp_rmb();
1997         if (p->on_rq && ttwu_remote(p, wake_flags))
1998                 goto stat;
1999 
2000 #ifdef CONFIG_SMP
2001         /*
2002          * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
2003          * possible to, falsely, observe p->on_cpu == 0.
2004          *
2005          * One must be running (->on_cpu == 1) in order to remove oneself
2006          * from the runqueue.
2007          *
2008          * __schedule() (switch to task 'p')    try_to_wake_up()
2009          *   STORE p->on_cpu = 1                  LOAD p->on_rq
2010          *   UNLOCK rq->lock
2011          *
2012          * __schedule() (put 'p' to sleep)
2013          *   LOCK rq->lock                        smp_rmb();
2014          *   smp_mb__after_spinlock();
2015          *   STORE p->on_rq = 0                   LOAD p->on_cpu
2016          *
2017          * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
2018          * __schedule().  See the comment for smp_mb__after_spinlock().
2019          */
2020         smp_rmb();
2021 
2022         /*
2023          * If the owning (remote) CPU is still in the middle of schedule() with
2024          * this task as prev, wait until its done referencing the task.
2025          *
2026          * Pairs with the smp_store_release() in finish_task().
2027          *
2028          * This ensures that tasks getting woken will be fully ordered against
2029          * their previous state and preserve Program Order.
2030          */
2031         smp_cond_load_acquire(&p->on_cpu, !VAL);
2032 
2033         p->sched_contributes_to_load = !!task_contributes_to_load(p);
2034         p->state = TASK_WAKING;
2035 
2036         if (p->in_iowait) {
2037                 delayacct_blkio_end(p);
2038                 atomic_dec(&task_rq(p)->nr_iowait);
2039         }
2040 
2041         cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags);
2042         if (task_cpu(p) != cpu) {
2043                 wake_flags |= WF_MIGRATED;
2044                 psi_ttwu_dequeue(p);
2045                 set_task_cpu(p, cpu);
2046         }
2047 
2048 #else /* CONFIG_SMP */
2049 
2050         if (p->in_iowait) {
2051                 delayacct_blkio_end(p);
2052                 atomic_dec(&task_rq(p)->nr_iowait);
2053         }
2054 
2055 #endif /* CONFIG_SMP */
2056 
2057         ttwu_queue(p, cpu, wake_flags);
2058 stat:
2059         ttwu_stat(p, cpu, wake_flags);
2060 out:
2061         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2062 
2063         return success;
2064 }
2065 
2066 /**
2067  * try_to_wake_up_local - try to wake up a local task with rq lock held
2068  * @p: the thread to be awakened
2069  * @rf: request-queue flags for pinning
2070  *
2071  * Put @p on the run-queue if it's not already there. The caller must
2072  * ensure that this_rq() is locked, @p is bound to this_rq() and not
2073  * the current task.
2074  */
2075 static void try_to_wake_up_local(struct task_struct *p, struct rq_flags *rf)
2076 {
2077         struct rq *rq = task_rq(p);
2078 
2079         if (WARN_ON_ONCE(rq != this_rq()) ||
2080             WARN_ON_ONCE(p == current))
2081                 return;
2082 
2083         lockdep_assert_held(&rq->lock);
2084 
2085         if (!raw_spin_trylock(&p->pi_lock)) {
2086                 /*
2087                  * This is OK, because current is on_cpu, which avoids it being
2088                  * picked for load-balance and preemption/IRQs are still
2089                  * disabled avoiding further scheduler activity on it and we've
2090                  * not yet picked a replacement task.
2091                  */
2092                 rq_unlock(rq, rf);
2093                 raw_spin_lock(&p->pi_lock);
2094                 rq_relock(rq, rf);
2095         }
2096 
2097         if (!(p->state & TASK_NORMAL))
2098                 goto out;
2099 
2100         trace_sched_waking(p);
2101 
2102         if (!task_on_rq_queued(p)) {
2103                 if (p->in_iowait) {
2104                         delayacct_blkio_end(p);
2105                         atomic_dec(&rq->nr_iowait);
2106                 }
2107                 ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK);
2108         }
2109 
2110         ttwu_do_wakeup(rq, p, 0, rf);
2111         ttwu_stat(p, smp_processor_id(), 0);
2112 out:
2113         raw_spin_unlock(&p->pi_lock);
2114 }
2115 
2116 /**
2117  * wake_up_process - Wake up a specific process
2118  * @p: The process to be woken up.
2119  *
2120  * Attempt to wake up the nominated process and move it to the set of runnable
2121  * processes.
2122  *
2123  * Return: 1 if the process was woken up, 0 if it was already running.
2124  *
2125  * This function executes a full memory barrier before accessing the task state.
2126  */
2127 int wake_up_process(struct task_struct *p)
2128 {
2129         return try_to_wake_up(p, TASK_NORMAL, 0);
2130 }
2131 EXPORT_SYMBOL(wake_up_process);
2132 
2133 int wake_up_state(struct task_struct *p, unsigned int state)
2134 {
2135         return try_to_wake_up(p, state, 0);
2136 }
2137 
2138 /*
2139  * Perform scheduler related setup for a newly forked process p.
2140  * p is forked by current.
2141  *
2142  * __sched_fork() is basic setup used by init_idle() too:
2143  */
2144 static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
2145 {
2146         p->on_rq                        = 0;
2147 
2148         p->se.on_rq                     = 0;
2149         p->se.exec_start                = 0;
2150         p->se.sum_exec_runtime          = 0;
2151         p->se.prev_sum_exec_runtime     = 0;
2152         p->se.nr_migrations             = 0;
2153         p->se.vruntime                  = 0;
2154         INIT_LIST_HEAD(&p->se.group_node);
2155 
2156 #ifdef CONFIG_FAIR_GROUP_SCHED
2157         p->se.cfs_rq                    = NULL;
2158 #endif
2159 
2160 #ifdef CONFIG_SCHEDSTATS
2161         /* Even if schedstat is disabled, there should not be garbage */
2162         memset(&p->se.statistics, 0, sizeof(p->se.statistics));
2163 #endif
2164 
2165         RB_CLEAR_NODE(&p->dl.rb_node);
2166         init_dl_task_timer(&p->dl);
2167         init_dl_inactive_task_timer(&p->dl);
2168         __dl_clear_params(p);
2169 
2170         INIT_LIST_HEAD(&p->rt.run_list);
2171         p->rt.timeout           = 0;
2172         p->rt.time_slice        = sched_rr_timeslice;
2173         p->rt.on_rq             = 0;
2174         p->rt.on_list           = 0;
2175 
2176 #ifdef CONFIG_PREEMPT_NOTIFIERS
2177         INIT_HLIST_HEAD(&p->preempt_notifiers);
2178 #endif
2179 
2180         init_numa_balancing(clone_flags, p);
2181 }
2182 
2183 DEFINE_STATIC_KEY_FALSE(sched_numa_balancing);
2184 
2185 #ifdef CONFIG_NUMA_BALANCING
2186 
2187 void set_numabalancing_state(bool enabled)
2188 {
2189         if (enabled)
2190                 static_branch_enable(&sched_numa_balancing);
2191         else
2192                 static_branch_disable(&sched_numa_balancing);
2193 }
2194 
2195 #ifdef CONFIG_PROC_SYSCTL
2196 int sysctl_numa_balancing(struct ctl_table *table, int write,
2197                          void __user *buffer, size_t *lenp, loff_t *ppos)
2198 {
2199         struct ctl_table t;
2200         int err;
2201         int state = static_branch_likely(&sched_numa_balancing);
2202 
2203         if (write && !capable(CAP_SYS_ADMIN))
2204                 return -EPERM;
2205 
2206         t = *table;
2207         t.data = &state;
2208         err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2209         if (err < 0)
2210                 return err;
2211         if (write)
2212                 set_numabalancing_state(state);
2213         return err;
2214 }
2215 #endif
2216 #endif
2217 
2218 #ifdef CONFIG_SCHEDSTATS
2219 
2220 DEFINE_STATIC_KEY_FALSE(sched_schedstats);
2221 static bool __initdata __sched_schedstats = false;
2222 
2223 static void set_schedstats(bool enabled)
2224 {
2225         if (enabled)
2226                 static_branch_enable(&sched_schedstats);
2227         else
2228                 static_branch_disable(&sched_schedstats);
2229 }
2230 
2231 void force_schedstat_enabled(void)
2232 {
2233         if (!schedstat_enabled()) {
2234                 pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
2235                 static_branch_enable(&sched_schedstats);
2236         }
2237 }
2238 
2239 static int __init setup_schedstats(char *str)
2240 {
2241         int ret = 0;
2242         if (!str)
2243                 goto out;
2244 
2245         /*
2246          * This code is called before jump labels have been set up, so we can't
2247          * change the static branch directly just yet.  Instead set a temporary
2248          * variable so init_schedstats() can do it later.
2249          */
2250         if (!strcmp(str, "enable")) {
2251                 __sched_schedstats = true;
2252                 ret = 1;
2253         } else if (!strcmp(str, "disable")) {
2254                 __sched_schedstats = false;
2255                 ret = 1;
2256         }
2257 out:
2258         if (!ret)
2259                 pr_warn("Unable to parse schedstats=\n");
2260 
2261         return ret;
2262 }
2263 __setup("schedstats=", setup_schedstats);
2264 
2265 static void __init init_schedstats(void)
2266 {
2267         set_schedstats(__sched_schedstats);
2268 }
2269 
2270 #ifdef CONFIG_PROC_SYSCTL
2271 int sysctl_schedstats(struct ctl_table *table, int write,
2272                          void __user *buffer, size_t *lenp, loff_t *ppos)
2273 {
2274         struct ctl_table t;
2275         int err;
2276         int state = static_branch_likely(&sched_schedstats);
2277 
2278         if (write && !capable(CAP_SYS_ADMIN))
2279                 return -EPERM;
2280 
2281         t = *table;
2282         t.data = &state;
2283         err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2284         if (err < 0)
2285                 return err;
2286         if (write)
2287                 set_schedstats(state);
2288         return err;
2289 }
2290 #endif /* CONFIG_PROC_SYSCTL */
2291 #else  /* !CONFIG_SCHEDSTATS */
2292 static inline void init_schedstats(void) {}
2293 #endif /* CONFIG_SCHEDSTATS */
2294 
2295 /*
2296  * fork()/clone()-time setup:
2297  */
2298 int sched_fork(unsigned long clone_flags, struct task_struct *p)
2299 {
2300         unsigned long flags;
2301 
2302         __sched_fork(clone_flags, p);
2303         /*
2304          * We mark the process as NEW here. This guarantees that
2305          * nobody will actually run it, and a signal or other external
2306          * event cannot wake it up and insert it on the runqueue either.
2307          */
2308         p->state = TASK_NEW;
2309 
2310         /*
2311          * Make sure we do not leak PI boosting priority to the child.
2312          */
2313         p->prio = current->normal_prio;
2314 
2315         /*
2316          * Revert to default priority/policy on fork if requested.
2317          */
2318         if (unlikely(p->sched_reset_on_fork)) {
2319                 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
2320                         p->policy = SCHED_NORMAL;
2321                         p->static_prio = NICE_TO_PRIO(0);
2322                         p->rt_priority = 0;
2323                 } else if (PRIO_TO_NICE(p->static_prio) < 0)
2324                         p->static_prio = NICE_TO_PRIO(0);
2325 
2326                 p->prio = p->normal_prio = __normal_prio(p);
2327                 set_load_weight(p, false);
2328 
2329                 /*
2330                  * We don't need the reset flag anymore after the fork. It has
2331                  * fulfilled its duty:
2332                  */
2333                 p->sched_reset_on_fork = 0;
2334         }
2335 
2336         if (dl_prio(p->prio))
2337                 return -EAGAIN;
2338         else if (rt_prio(p->prio))
2339                 p->sched_class = &rt_sched_class;
2340         else
2341                 p->sched_class = &fair_sched_class;
2342 
2343         init_entity_runnable_average(&p->se);
2344 
2345         /*
2346          * The child is not yet in the pid-hash so no cgroup attach races,
2347          * and the cgroup is pinned to this child due to cgroup_fork()
2348          * is ran before sched_fork().
2349          *
2350          * Silence PROVE_RCU.
2351          */
2352         raw_spin_lock_irqsave(&p->pi_lock, flags);
2353         /*
2354          * We're setting the CPU for the first time, we don't migrate,
2355          * so use __set_task_cpu().
2356          */
2357         __set_task_cpu(p, smp_processor_id());
2358         if (p->sched_class->task_fork)
2359                 p->sched_class->task_fork(p);
2360         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2361 
2362 #ifdef CONFIG_SCHED_INFO
2363         if (likely(sched_info_on()))
2364                 memset(&p->sched_info, 0, sizeof(p->sched_info));
2365 #endif
2366 #if defined(CONFIG_SMP)
2367         p->on_cpu = 0;
2368 #endif
2369         init_task_preempt_count(p);
2370 #ifdef CONFIG_SMP
2371         plist_node_init(&p->pushable_tasks, MAX_PRIO);
2372         RB_CLEAR_NODE(&p->pushable_dl_tasks);
2373 #endif
2374         return 0;
2375 }
2376 
2377 unsigned long to_ratio(u64 period, u64 runtime)
2378 {
2379         if (runtime == RUNTIME_INF)
2380                 return BW_UNIT;
2381 
2382         /*
2383          * Doing this here saves a lot of checks in all
2384          * the calling paths, and returning zero seems
2385          * safe for them anyway.
2386          */
2387         if (period == 0)
2388                 return 0;
2389 
2390         return div64_u64(runtime << BW_SHIFT, period);
2391 }
2392 
2393 /*
2394  * wake_up_new_task - wake up a newly created task for the first time.
2395  *
2396  * This function will do some initial scheduler statistics housekeeping
2397  * that must be done for every newly created context, then puts the task
2398  * on the runqueue and wakes it.
2399  */
2400 void wake_up_new_task(struct task_struct *p)
2401 {
2402         struct rq_flags rf;
2403         struct rq *rq;
2404 
2405         raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
2406         p->state = TASK_RUNNING;
2407 #ifdef CONFIG_SMP
2408         /*
2409          * Fork balancing, do it here and not earlier because:
2410          *  - cpus_allowed can change in the fork path
2411          *  - any previously selected CPU might disappear through hotplug
2412          *
2413          * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
2414          * as we're not fully set-up yet.
2415          */
2416         p->recent_used_cpu = task_cpu(p);
2417         __set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
2418 #endif
2419         rq = __task_rq_lock(p, &rf);
2420         update_rq_clock(rq);
2421         post_init_entity_util_avg(&p->se);
2422 
2423         activate_task(rq, p, ENQUEUE_NOCLOCK);
2424         p->on_rq = TASK_ON_RQ_QUEUED;
2425         trace_sched_wakeup_new(p);
2426         check_preempt_curr(rq, p, WF_FORK);
2427 #ifdef CONFIG_SMP
2428         if (p->sched_class->task_woken) {
2429                 /*
2430                  * Nothing relies on rq->lock after this, so its fine to
2431                  * drop it.
2432                  */
2433                 rq_unpin_lock(rq, &rf);
2434                 p->sched_class->task_woken(rq, p);
2435                 rq_repin_lock(rq, &rf);
2436         }
2437 #endif
2438         task_rq_unlock(rq, p, &rf);
2439 }
2440 
2441 #ifdef CONFIG_PREEMPT_NOTIFIERS
2442 
2443 static DEFINE_STATIC_KEY_FALSE(preempt_notifier_key);
2444 
2445 void preempt_notifier_inc(void)
2446 {
2447         static_branch_inc(&preempt_notifier_key);
2448 }
2449 EXPORT_SYMBOL_GPL(preempt_notifier_inc);
2450 
2451 void preempt_notifier_dec(void)
2452 {
2453         static_branch_dec(&preempt_notifier_key);
2454 }
2455 EXPORT_SYMBOL_GPL(preempt_notifier_dec);
2456 
2457 /**
2458  * preempt_notifier_register - tell me when current is being preempted & rescheduled
2459  * @notifier: notifier struct to register
2460  */
2461 void preempt_notifier_register(struct preempt_notifier *notifier)
2462 {
2463         if (!static_branch_unlikely(&preempt_notifier_key))
2464                 WARN(1, "registering preempt_notifier while notifiers disabled\n");
2465 
2466         hlist_add_head(&notifier->link, &current->preempt_notifiers);
2467 }
2468 EXPORT_SYMBOL_GPL(preempt_notifier_register);
2469 
2470 /**
2471  * preempt_notifier_unregister - no longer interested in preemption notifications
2472  * @notifier: notifier struct to unregister
2473  *
2474  * This is *not* safe to call from within a preemption notifier.
2475  */
2476 void preempt_notifier_unregister(struct preempt_notifier *notifier)
2477 {
2478         hlist_del(&notifier->link);
2479 }
2480 EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
2481 
2482 static void __fire_sched_in_preempt_notifiers(struct task_struct *curr)
2483 {
2484         struct preempt_notifier *notifier;
2485 
2486         hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
2487                 notifier->ops->sched_in(notifier, raw_smp_processor_id());
2488 }
2489 
2490 static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
2491 {
2492         if (static_branch_unlikely(&preempt_notifier_key))
2493                 __fire_sched_in_preempt_notifiers(curr);
2494 }
2495 
2496 static void
2497 __fire_sched_out_preempt_notifiers(struct task_struct *curr,
2498                                    struct task_struct *next)
2499 {
2500         struct preempt_notifier *notifier;
2501 
2502         hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
2503                 notifier->ops->sched_out(notifier, next);
2504 }
2505 
2506 static __always_inline void
2507 fire_sched_out_preempt_notifiers(struct task_struct *curr,
2508                                  struct task_struct *next)
2509 {
2510         if (static_branch_unlikely(&preempt_notifier_key))
2511                 __fire_sched_out_preempt_notifiers(curr, next);
2512 }
2513 
2514 #else /* !CONFIG_PREEMPT_NOTIFIERS */
2515 
2516 static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
2517 {
2518 }
2519 
2520 static inline void
2521 fire_sched_out_preempt_notifiers(struct task_struct *curr,
2522                                  struct task_struct *next)
2523 {
2524 }
2525 
2526 #endif /* CONFIG_PREEMPT_NOTIFIERS */
2527 
2528 static inline void prepare_task(struct task_struct *next)
2529 {
2530 #ifdef CONFIG_SMP
2531         /*
2532          * Claim the task as running, we do this before switching to it
2533          * such that any running task will have this set.
2534          */
2535         next->on_cpu = 1;
2536 #endif
2537 }
2538 
2539 static inline void finish_task(struct task_struct *prev)
2540 {
2541 #ifdef CONFIG_SMP
2542         /*
2543          * After ->on_cpu is cleared, the task can be moved to a different CPU.
2544          * We must ensure this doesn't happen until the switch is completely
2545          * finished.
2546          *
2547          * In particular, the load of prev->state in finish_task_switch() must
2548          * happen before this.
2549          *
2550          * Pairs with the smp_cond_load_acquire() in try_to_wake_up().
2551          */
2552         smp_store_release(&prev->on_cpu, 0);
2553 #endif
2554 }
2555 
2556 static inline void
2557 prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf)
2558 {
2559         /*
2560          * Since the runqueue lock will be released by the next
2561          * task (which is an invalid locking op but in the case
2562          * of the scheduler it's an obvious special-case), so we
2563          * do an early lockdep release here:
2564          */
2565         rq_unpin_lock(rq, rf);
2566         spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
2567 #ifdef CONFIG_DEBUG_SPINLOCK
2568         /* this is a valid case when another task releases the spinlock */
2569         rq->lock.owner = next;
2570 #endif
2571 }
2572 
2573 static inline void finish_lock_switch(struct rq *rq)
2574 {
2575         /*
2576          * If we are tracking spinlock dependencies then we have to
2577          * fix up the runqueue lock - which gets 'carried over' from
2578          * prev into current:
2579          */
2580         spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_);
2581         raw_spin_unlock_irq(&rq->lock);
2582 }
2583 
2584 /*
2585  * NOP if the arch has not defined these:
2586  */
2587 
2588 #ifndef prepare_arch_switch
2589 # define prepare_arch_switch(next)      do { } while (0)
2590 #endif
2591 
2592 #ifndef finish_arch_post_lock_switch
2593 # define finish_arch_post_lock_switch() do { } while (0)
2594 #endif
2595 
2596 /**
2597  * prepare_task_switch - prepare to switch tasks
2598  * @rq: the runqueue preparing to switch
2599  * @prev: the current task that is being switched out
2600  * @next: the task we are going to switch to.
2601  *
2602  * This is called with the rq lock held and interrupts off. It must
2603  * be paired with a subsequent finish_task_switch after the context
2604  * switch.
2605  *
2606  * prepare_task_switch sets up locking and calls architecture specific
2607  * hooks.
2608  */
2609 static inline void
2610 prepare_task_switch(struct rq *rq, struct task_struct *prev,
2611                     struct task_struct *next)
2612 {
2613         kcov_prepare_switch(prev);
2614         sched_info_switch(rq, prev, next);
2615         perf_event_task_sched_out(prev, next);
2616         rseq_preempt(prev);
2617         fire_sched_out_preempt_notifiers(prev, next);
2618         prepare_task(next);
2619         prepare_arch_switch(next);
2620 }
2621 
2622 /**
2623  * finish_task_switch - clean up after a task-switch
2624  * @prev: the thread we just switched away from.
2625  *
2626  * finish_task_switch must be called after the context switch, paired
2627  * with a prepare_task_switch call before the context switch.
2628  * finish_task_switch will reconcile locking set up by prepare_task_switch,
2629  * and do any other architecture-specific cleanup actions.
2630  *
2631  * Note that we may have delayed dropping an mm in context_switch(). If
2632  * so, we finish that here outside of the runqueue lock. (Doing it
2633  * with the lock held can cause deadlocks; see schedule() for
2634  * details.)
2635  *
2636  * The context switch have flipped the stack from under us and restored the
2637  * local variables which were saved when this task called schedule() in the
2638  * past. prev == current is still correct but we need to recalculate this_rq
2639  * because prev may have moved to another CPU.
2640  */
2641 static struct rq *finish_task_switch(struct task_struct *prev)
2642         __releases(rq->lock)
2643 {
2644         struct rq *rq = this_rq();
2645         struct mm_struct *mm = rq->prev_mm;
2646         long prev_state;
2647 
2648         /*
2649          * The previous task will have left us with a preempt_count of 2
2650          * because it left us after:
2651          *
2652          *      schedule()
2653          *        preempt_disable();                    // 1
2654          *        __schedule()
2655          *          raw_spin_lock_irq(&rq->lock)        // 2
2656          *
2657          * Also, see FORK_PREEMPT_COUNT.
2658          */
2659         if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET,
2660                       "corrupted preempt_count: %s/%d/0x%x\n",
2661                       current->comm, current->pid, preempt_count()))
2662                 preempt_count_set(FORK_PREEMPT_COUNT);
2663 
2664         rq->prev_mm = NULL;
2665 
2666         /*
2667          * A task struct has one reference for the use as "current".
2668          * If a task dies, then it sets TASK_DEAD in tsk->state and calls
2669          * schedule one last time. The schedule call will never return, and
2670          * the scheduled task must drop that reference.
2671          *
2672          * We must observe prev->state before clearing prev->on_cpu (in
2673          * finish_task), otherwise a concurrent wakeup can get prev
2674          * running on another CPU and we could rave with its RUNNING -> DEAD
2675          * transition, resulting in a double drop.
2676          */
2677         prev_state = prev->state;
2678         vtime_task_switch(prev);
2679         perf_event_task_sched_in(prev, current);
2680         finish_task(prev);
2681         finish_lock_switch(rq);
2682         finish_arch_post_lock_switch();
2683         kcov_finish_switch(current);
2684 
2685         fire_sched_in_preempt_notifiers(current);
2686         /*
2687          * When switching through a kernel thread, the loop in
2688          * membarrier_{private,global}_expedited() may have observed that
2689          * kernel thread and not issued an IPI. It is therefore possible to
2690          * schedule between user->kernel->user threads without passing though
2691          * switch_mm(). Membarrier requires a barrier after storing to
2692          * rq->curr, before returning to userspace, so provide them here:
2693          *
2694          * - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly
2695          *   provided by mmdrop(),
2696          * - a sync_core for SYNC_CORE.
2697          */
2698         if (mm) {
2699                 membarrier_mm_sync_core_before_usermode(mm);
2700                 mmdrop(mm);
2701         }
2702         if (unlikely(prev_state == TASK_DEAD)) {
2703                 if (prev->sched_class->task_dead)
2704                         prev->sched_class->task_dead(prev);
2705 
2706                 /*
2707                  * Remove function-return probe instances associated with this
2708                  * task and put them back on the free list.
2709                  */
2710                 kprobe_flush_task(prev);
2711 
2712                 /* Task is done with its stack. */
2713                 put_task_stack(prev);
2714 
2715                 put_task_struct(prev);
2716         }
2717 
2718         tick_nohz_task_switch();
2719         return rq;
2720 }
2721 
2722 #ifdef CONFIG_SMP
2723 
2724 /* rq->lock is NOT held, but preemption is disabled */
2725 static void __balance_callback(struct rq *rq)
2726 {
2727         struct callback_head *head, *next;
2728         void (*func)(struct rq *rq);
2729         unsigned long flags;
2730 
2731         raw_spin_lock_irqsave(&rq->lock, flags);
2732         head = rq->balance_callback;
2733         rq->balance_callback = NULL;
2734         while (head) {
2735                 func = (void (*)(struct rq *))head->func;
2736                 next = head->next;
2737                 head->next = NULL;
2738                 head = next;
2739 
2740                 func(rq);
2741         }
2742         raw_spin_unlock_irqrestore(&rq->lock, flags);
2743 }
2744 
2745 static inline void balance_callback(struct rq *rq)
2746 {
2747         if (unlikely(rq->balance_callback))
2748                 __balance_callback(rq);
2749 }
2750 
2751 #else
2752 
2753 static inline void balance_callback(struct rq *rq)
2754 {
2755 }
2756 
2757 #endif
2758 
2759 /**
2760  * schedule_tail - first thing a freshly forked thread must call.
2761  * @prev: the thread we just switched away from.
2762  */
2763 asmlinkage __visible void schedule_tail(struct task_struct *prev)
2764         __releases(rq->lock)
2765 {
2766         struct rq *rq;
2767 
2768         /*
2769          * New tasks start with FORK_PREEMPT_COUNT, see there and
2770          * finish_task_switch() for details.
2771          *
2772          * finish_task_switch() will drop rq->lock() and lower preempt_count
2773          * and the preempt_enable() will end up enabling preemption (on
2774          * PREEMPT_COUNT kernels).
2775          */
2776 
2777         rq = finish_task_switch(prev);
2778         balance_callback(rq);
2779         preempt_enable();
2780 
2781         if (current->set_child_tid)
2782                 put_user(task_pid_vnr(current), current->set_child_tid);
2783 
2784         calculate_sigpending();
2785 }
2786 
2787 /*
2788  * context_switch - switch to the new MM and the new thread's register state.
2789  */
2790 static __always_inline struct rq *
2791 context_switch(struct rq *rq, struct task_struct *prev,
2792                struct task_struct *next, struct rq_flags *rf)
2793 {
2794         struct mm_struct *mm, *oldmm;
2795 
2796         prepare_task_switch(rq, prev, next);
2797 
2798         mm = next->mm;
2799         oldmm = prev->active_mm;
2800         /*
2801          * For paravirt, this is coupled with an exit in switch_to to
2802          * combine the page table reload and the switch backend into
2803          * one hypercall.
2804          */
2805         arch_start_context_switch(prev);
2806 
2807         /*
2808          * If mm is non-NULL, we pass through switch_mm(). If mm is
2809          * NULL, we will pass through mmdrop() in finish_task_switch().
2810          * Both of these contain the full memory barrier required by
2811          * membarrier after storing to rq->curr, before returning to
2812          * user-space.
2813          */
2814         if (!mm) {
2815                 next->active_mm = oldmm;
2816                 mmgrab(oldmm);
2817                 enter_lazy_tlb(oldmm, next);
2818         } else
2819                 switch_mm_irqs_off(oldmm, mm, next);
2820 
2821         if (!prev->mm) {
2822                 prev->active_mm = NULL;
2823                 rq->prev_mm = oldmm;
2824         }
2825 
2826         rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
2827 
2828         prepare_lock_switch(rq, next, rf);
2829 
2830         /* Here we just switch the register state and the stack. */
2831         switch_to(prev, next, prev);
2832         barrier();
2833 
2834         return finish_task_switch(prev);
2835 }
2836 
2837 /*
2838  * nr_running and nr_context_switches:
2839  *
2840  * externally visible scheduler statistics: current number of runnable
2841  * threads, total number of context switches performed since bootup.
2842  */
2843 unsigned long nr_running(void)
2844 {
2845         unsigned long i, sum = 0;
2846 
2847         for_each_online_cpu(i)
2848                 sum += cpu_rq(i)->nr_running;
2849 
2850         return sum;
2851 }
2852 
2853 /*
2854  * Check if only the current task is running on the CPU.
2855  *
2856  * Caution: this function does not check that the caller has disabled
2857  * preemption, thus the result might have a time-of-check-to-time-of-use
2858  * race.  The caller is responsible to use it correctly, for example:
2859  *
2860  * - from a non-preemptable section (of course)
2861  *
2862  * - from a thread that is bound to a single CPU
2863  *
2864  * - in a loop with very short iterations (e.g. a polling loop)
2865  */
2866 bool single_task_running(void)
2867 {
2868         return raw_rq()->nr_running == 1;
2869 }
2870 EXPORT_SYMBOL(single_task_running);
2871 
2872 unsigned long long nr_context_switches(void)
2873 {
2874         int i;
2875         unsigned long long sum = 0;
2876 
2877         for_each_possible_cpu(i)
2878                 sum += cpu_rq(i)->nr_switches;
2879 
2880         return sum;
2881 }
2882 
2883 /*
2884  * Consumers of these two interfaces, like for example the cpuidle menu
2885  * governor, are using nonsensical data. Preferring shallow idle state selection
2886  * for a CPU that has IO-wait which might not even end up running the task when
2887  * it does become runnable.
2888  */
2889 
2890 unsigned long nr_iowait_cpu(int cpu)
2891 {
2892         return atomic_read(&cpu_rq(cpu)->nr_iowait);
2893 }
2894 
2895 /*
2896  * IO-wait accounting, and how its mostly bollocks (on SMP).
2897  *
2898  * The idea behind IO-wait account is to account the idle time that we could
2899  * have spend running if it were not for IO. That is, if we were to improve the
2900  * storage performance, we'd have a proportional reduction in IO-wait time.
2901  *
2902  * This all works nicely on UP, where, when a task blocks on IO, we account
2903  * idle time as IO-wait, because if the storage were faster, it could've been
2904  * running and we'd not be idle.
2905  *
2906  * This has been extended to SMP, by doing the same for each CPU. This however
2907  * is broken.
2908  *
2909  * Imagine for instance the case where two tasks block on one CPU, only the one
2910  * CPU will have IO-wait accounted, while the other has regular idle. Even
2911  * though, if the storage were faster, both could've ran at the same time,
2912  * utilising both CPUs.
2913  *
2914  * This means, that when looking globally, the current IO-wait accounting on
2915  * SMP is a lower bound, by reason of under accounting.
2916  *
2917  * Worse, since the numbers are provided per CPU, they are sometimes
2918  * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly
2919  * associated with any one particular CPU, it can wake to another CPU than it
2920  * blocked on. This means the per CPU IO-wait number is meaningless.
2921  *
2922  * Task CPU affinities can make all that even more 'interesting'.
2923  */
2924 
2925 unsigned long nr_iowait(void)
2926 {
2927         unsigned long i, sum = 0;
2928 
2929         for_each_possible_cpu(i)
2930                 sum += nr_iowait_cpu(i);
2931 
2932         return sum;
2933 }
2934 
2935 #ifdef CONFIG_SMP
2936 
2937 /*
2938  * sched_exec - execve() is a valuable balancing opportunity, because at
2939  * this point the task has the smallest effective memory and cache footprint.
2940  */
2941 void sched_exec(void)
2942 {
2943         struct task_struct *p = current;
2944         unsigned long flags;
2945         int dest_cpu;
2946 
2947         raw_spin_lock_irqsave(&p->pi_lock, flags);
2948         dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), SD_BALANCE_EXEC, 0);
2949         if (dest_cpu == smp_processor_id())
2950                 goto unlock;
2951 
2952         if (likely(cpu_active(dest_cpu))) {
2953                 struct migration_arg arg = { p, dest_cpu };
2954 
2955                 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2956                 stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
2957                 return;
2958         }
2959 unlock:
2960         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2961 }
2962 
2963 #endif
2964 
2965 DEFINE_PER_CPU(struct kernel_stat, kstat);
2966 DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
2967 
2968 EXPORT_PER_CPU_SYMBOL(kstat);
2969 EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
2970 
2971 /*
2972  * The function fair_sched_class.update_curr accesses the struct curr
2973  * and its field curr->exec_start; when called from task_sched_runtime(),
2974  * we observe a high rate of cache misses in practice.
2975  * Prefetching this data results in improved performance.
2976  */
2977 static inline void prefetch_curr_exec_start(struct task_struct *p)
2978 {
2979 #ifdef CONFIG_FAIR_GROUP_SCHED
2980         struct sched_entity *curr = (&p->se)->cfs_rq->curr;
2981 #else
2982         struct sched_entity *curr = (&task_rq(p)->cfs)->curr;
2983 #endif
2984         prefetch(curr);
2985         prefetch(&curr->exec_start);
2986 }
2987 
2988 /*
2989  * Return accounted runtime for the task.
2990  * In case the task is currently running, return the runtime plus current's
2991  * pending runtime that have not been accounted yet.
2992  */
2993 unsigned long long task_sched_runtime(struct task_struct *p)
2994 {
2995         struct rq_flags rf;
2996         struct rq *rq;
2997         u64 ns;
2998 
2999 #if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
3000         /*
3001          * 64-bit doesn't need locks to atomically read a 64-bit value.
3002          * So we have a optimization chance when the task's delta_exec is 0.
3003          * Reading ->on_cpu is racy, but this is ok.
3004          *
3005          * If we race with it leaving CPU, we'll take a lock. So we're correct.
3006          * If we race with it entering CPU, unaccounted time is 0. This is
3007          * indistinguishable from the read occurring a few cycles earlier.
3008          * If we see ->on_cpu without ->on_rq, the task is leaving, and has
3009          * been accounted, so we're correct here as well.
3010          */
3011         if (!p->on_cpu || !task_on_rq_queued(p))
3012                 return p->se.sum_exec_runtime;
3013 #endif
3014 
3015         rq = task_rq_lock(p, &rf);
3016         /*
3017          * Must be ->curr _and_ ->on_rq.  If dequeued, we would
3018          * project cycles that may never be accounted to this
3019          * thread, breaking clock_gettime().
3020          */
3021         if (task_current(rq, p) && task_on_rq_queued(p)) {
3022                 prefetch_curr_exec_start(p);
3023                 update_rq_clock(rq);
3024                 p->sched_class->update_curr(rq);
3025         }
3026         ns = p->se.sum_exec_runtime;
3027         task_rq_unlock(rq, p, &rf);
3028 
3029         return ns;
3030 }
3031 
3032 /*
3033  * This function gets called by the timer code, with HZ frequency.
3034  * We call it with interrupts disabled.
3035  */
3036 void scheduler_tick(void)
3037 {
3038         int cpu = smp_processor_id();
3039         struct rq *rq = cpu_rq(cpu);
3040         struct task_struct *curr = rq->curr;
3041         struct rq_flags rf;
3042 
3043         sched_clock_tick();
3044 
3045         rq_lock(rq, &rf);
3046 
3047         update_rq_clock(rq);
3048         curr->sched_class->task_tick(rq, curr, 0);
3049         cpu_load_update_active(rq);
3050         calc_global_load_tick(rq);
3051         psi_task_tick(rq);
3052 
3053         rq_unlock(rq, &rf);
3054 
3055         perf_event_task_tick();
3056 
3057 #ifdef CONFIG_SMP
3058         rq->idle_balance = idle_cpu(cpu);
3059         trigger_load_balance(rq);
3060 #endif
3061 }
3062 
3063 #ifdef CONFIG_NO_HZ_FULL
3064 
3065 struct tick_work {
3066         int                     cpu;
3067         struct delayed_work     work;
3068 };
3069 
3070 static struct tick_work __percpu *tick_work_cpu;
3071 
3072 static void sched_tick_remote(struct work_struct *work)
3073 {
3074         struct delayed_work *dwork = to_delayed_work(work);
3075         struct tick_work *twork = container_of(dwork, struct tick_work, work);
3076         int cpu = twork->cpu;
3077         struct rq *rq = cpu_rq(cpu);
3078         struct task_struct *curr;
3079         struct rq_flags rf;
3080         u64 delta;
3081 
3082         /*
3083          * Handle the tick only if it appears the remote CPU is running in full
3084          * dynticks mode. The check is racy by nature, but missing a tick or
3085          * having one too much is no big deal because the scheduler tick updates
3086          * statistics and checks timeslices in a time-independent way, regardless
3087          * of when exactly it is running.
3088          */
3089         if (idle_cpu(cpu) || !tick_nohz_tick_stopped_cpu(cpu))
3090                 goto out_requeue;
3091 
3092         rq_lock_irq(rq, &rf);
3093         curr = rq->curr;
3094         if (is_idle_task(curr))
3095                 goto out_unlock;
3096 
3097         update_rq_clock(rq);
3098         delta = rq_clock_task(rq) - curr->se.exec_start;
3099 
3100         /*
3101          * Make sure the next tick runs within a reasonable
3102          * amount of time.
3103          */
3104         WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3);
3105         curr->sched_class->task_tick(rq, curr, 0);
3106 
3107 out_unlock:
3108         rq_unlock_irq(rq, &rf);
3109 
3110 out_requeue:
3111         /*
3112          * Run the remote tick once per second (1Hz). This arbitrary
3113          * frequency is large enough to avoid overload but short enough
3114          * to keep scheduler internal stats reasonably up to date.
3115          */
3116         queue_delayed_work(system_unbound_wq, dwork, HZ);
3117 }
3118 
3119 static void sched_tick_start(int cpu)
3120 {
3121         struct tick_work *twork;
3122 
3123         if (housekeeping_cpu(cpu, HK_FLAG_TICK))
3124                 return;
3125 
3126         WARN_ON_ONCE(!tick_work_cpu);
3127 
3128         twork = per_cpu_ptr(tick_work_cpu, cpu);
3129         twork->cpu = cpu;
3130         INIT_DELAYED_WORK(&twork->work, sched_tick_remote);
3131         queue_delayed_work(system_unbound_wq, &twork->work, HZ);
3132 }
3133 
3134 #ifdef CONFIG_HOTPLUG_CPU
3135 static void sched_tick_stop(int cpu)
3136 {
3137         struct tick_work *twork;
3138 
3139         if (housekeeping_cpu(cpu, HK_FLAG_TICK))
3140                 return;
3141 
3142         WARN_ON_ONCE(!tick_work_cpu);
3143 
3144         twork = per_cpu_ptr(tick_work_cpu, cpu);
3145         cancel_delayed_work_sync(&twork->work);
3146 }
3147 #endif /* CONFIG_HOTPLUG_CPU */
3148 
3149 int __init sched_tick_offload_init(void)
3150 {
3151         tick_work_cpu = alloc_percpu(struct tick_work);
3152         BUG_ON(!tick_work_cpu);
3153 
3154         return 0;
3155 }
3156 
3157 #else /* !CONFIG_NO_HZ_FULL */
3158 static inline void sched_tick_start(int cpu) { }
3159 static inline void sched_tick_stop(int cpu) { }
3160 #endif
3161 
3162 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
3163                                 defined(CONFIG_TRACE_PREEMPT_TOGGLE))
3164 /*
3165  * If the value passed in is equal to the current preempt count
3166  * then we just disabled preemption. Start timing the latency.
3167  */
3168 static inline void preempt_latency_start(int val)
3169 {
3170         if (preempt_count() == val) {
3171                 unsigned long ip = get_lock_parent_ip();
3172 #ifdef CONFIG_DEBUG_PREEMPT
3173                 current->preempt_disable_ip = ip;
3174 #endif
3175                 trace_preempt_off(CALLER_ADDR0, ip);
3176         }
3177 }
3178 
3179 void preempt_count_add(int val)
3180 {
3181 #ifdef CONFIG_DEBUG_PREEMPT
3182         /*
3183          * Underflow?
3184          */
3185         if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
3186                 return;
3187 #endif
3188         __preempt_count_add(val);
3189 #ifdef CONFIG_DEBUG_PREEMPT
3190         /*
3191          * Spinlock count overflowing soon?
3192          */
3193         DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
3194                                 PREEMPT_MASK - 10);
3195 #endif
3196         preempt_latency_start(val);
3197 }
3198 EXPORT_SYMBOL(preempt_count_add);
3199 NOKPROBE_SYMBOL(preempt_count_add);
3200 
3201 /*
3202  * If the value passed in equals to the current preempt count
3203  * then we just enabled preemption. Stop timing the latency.
3204  */
3205 static inline void preempt_latency_stop(int val)
3206 {
3207         if (preempt_count() == val)
3208                 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
3209 }
3210 
3211 void preempt_count_sub(int val)
3212 {
3213 #ifdef CONFIG_DEBUG_PREEMPT
3214         /*
3215          * Underflow?
3216          */
3217         if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
3218                 return;
3219         /*
3220          * Is the spinlock portion underflowing?
3221          */
3222         if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
3223                         !(preempt_count() & PREEMPT_MASK)))
3224                 return;
3225 #endif
3226 
3227         preempt_latency_stop(val);
3228         __preempt_count_sub(val);
3229 }
3230 EXPORT_SYMBOL(preempt_count_sub);
3231 NOKPROBE_SYMBOL(preempt_count_sub);
3232 
3233 #else
3234 static inline void preempt_latency_start(int val) { }
3235 static inline void preempt_latency_stop(int val) { }
3236 #endif
3237 
3238 static inline unsigned long get_preempt_disable_ip(struct task_struct *p)
3239 {
3240 #ifdef CONFIG_DEBUG_PREEMPT
3241         return p->preempt_disable_ip;
3242 #else
3243         return 0;
3244 #endif
3245 }
3246 
3247 /*
3248  * Print scheduling while atomic bug:
3249  */
3250 static noinline void __schedule_bug(struct task_struct *prev)
3251 {
3252         /* Save this before calling printk(), since that will clobber it */
3253         unsigned long preempt_disable_ip = get_preempt_disable_ip(current);
3254 
3255         if (oops_in_progress)
3256                 return;
3257 
3258         printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
3259                 prev->comm, prev->pid, preempt_count());
3260 
3261         debug_show_held_locks(prev);
3262         print_modules();
3263         if (irqs_disabled())
3264                 print_irqtrace_events(prev);
3265         if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
3266             && in_atomic_preempt_off()) {
3267                 pr_err("Preemption disabled at:");
3268                 print_ip_sym(preempt_disable_ip);
3269                 pr_cont("\n");
3270         }
3271         if (panic_on_warn)
3272                 panic("scheduling while atomic\n");
3273 
3274         dump_stack();
3275         add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
3276 }
3277 
3278 /*
3279  * Various schedule()-time debugging checks and statistics:
3280  */
3281 static inline void schedule_debug(struct task_struct *prev)
3282 {
3283 #ifdef CONFIG_SCHED_STACK_END_CHECK
3284         if (task_stack_end_corrupted(prev))
3285                 panic("corrupted stack end detected inside scheduler\n");
3286 #endif
3287 
3288         if (unlikely(in_atomic_preempt_off())) {
3289                 __schedule_bug(prev);
3290                 preempt_count_set(PREEMPT_DISABLED);
3291         }
3292         rcu_sleep_check();
3293 
3294         profile_hit(SCHED_PROFILING, __builtin_return_address(0));
3295 
3296         schedstat_inc(this_rq()->sched_count);
3297 }
3298 
3299 /*
3300  * Pick up the highest-prio task:
3301  */
3302 static inline struct task_struct *
3303 pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
3304 {
3305         const struct sched_class *class;
3306         struct task_struct *p;
3307 
3308         /*
3309          * Optimization: we know that if all tasks are in the fair class we can
3310          * call that function directly, but only if the @prev task wasn't of a
3311          * higher scheduling class, because otherwise those loose the
3312          * opportunity to pull in more work from other CPUs.
3313          */
3314         if (likely((prev->sched_class == &idle_sched_class ||
3315                     prev->sched_class == &fair_sched_class) &&
3316                    rq->nr_running == rq->cfs.h_nr_running)) {
3317 
3318                 p = fair_sched_class.pick_next_task(rq, prev, rf);
3319                 if (unlikely(p == RETRY_TASK))
3320                         goto again;
3321 
3322                 /* Assumes fair_sched_class->next == idle_sched_class */
3323                 if (unlikely(!p))
3324                         p = idle_sched_class.pick_next_task(rq, prev, rf);
3325 
3326                 return p;
3327         }
3328 
3329 again:
3330         for_each_class(class) {
3331                 p = class->pick_next_task(rq, prev, rf);
3332                 if (p) {
3333                         if (unlikely(p == RETRY_TASK))
3334                                 goto again;
3335                         return p;
3336                 }
3337         }
3338 
3339         /* The idle class should always have a runnable task: */
3340         BUG();
3341 }
3342 
3343 /*
3344  * __schedule() is the main scheduler function.
3345  *
3346  * The main means of driving the scheduler and thus entering this function are:
3347  *
3348  *   1. Explicit blocking: mutex, semaphore, waitqueue, etc.
3349  *
3350  *   2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
3351  *      paths. For example, see arch/x86/entry_64.S.
3352  *
3353  *      To drive preemption between tasks, the scheduler sets the flag in timer
3354  *      interrupt handler scheduler_tick().
3355  *
3356  *   3. Wakeups don't really cause entry into schedule(). They add a
3357  *      task to the run-queue and that's it.
3358  *
3359  *      Now, if the new task added to the run-queue preempts the current
3360  *      task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
3361  *      called on the nearest possible occasion:
3362  *
3363  *       - If the kernel is preemptible (CONFIG_PREEMPT=y):
3364  *
3365  *         - in syscall or exception context, at the next outmost
3366  *           preempt_enable(). (this might be as soon as the wake_up()'s
3367  *           spin_unlock()!)
3368  *
3369  *         - in IRQ context, return from interrupt-handler to
3370  *           preemptible context
3371  *
3372  *       - If the kernel is not preemptible (CONFIG_PREEMPT is not set)
3373  *         then at the next:
3374  *
3375  *          - cond_resched() call
3376  *          - explicit schedule() call
3377  *          - return from syscall or exception to user-space
3378  *          - return from interrupt-handler to user-space
3379  *
3380  * WARNING: must be called with preemption disabled!
3381  */
3382 static void __sched notrace __schedule(bool preempt)
3383 {
3384         struct task_struct *prev, *next;
3385         unsigned long *switch_count;
3386         struct rq_flags rf;
3387         struct rq *rq;
3388         int cpu;
3389 
3390         cpu = smp_processor_id();
3391         rq = cpu_rq(cpu);
3392         prev = rq->curr;
3393 
3394         schedule_debug(prev);
3395 
3396         if (sched_feat(HRTICK))
3397                 hrtick_clear(rq);
3398 
3399         local_irq_disable();
3400         rcu_note_context_switch(preempt);
3401 
3402         /*
3403          * Make sure that signal_pending_state()->signal_pending() below
3404          * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
3405          * done by the caller to avoid the race with signal_wake_up().
3406          *
3407          * The membarrier system call requires a full memory barrier
3408          * after coming from user-space, before storing to rq->curr.
3409          */
3410         rq_lock(rq, &rf);
3411         smp_mb__after_spinlock();
3412 
3413         /* Promote REQ to ACT */
3414         rq->clock_update_flags <<= 1;
3415         update_rq_clock(rq);
3416 
3417         switch_count = &prev->nivcsw;
3418         if (!preempt && prev->state) {
3419                 if (unlikely(signal_pending_state(prev->state, prev))) {
3420                         prev->state = TASK_RUNNING;
3421                 } else {
3422                         deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK);
3423                         prev->on_rq = 0;
3424 
3425                         if (prev->in_iowait) {
3426                                 atomic_inc(&rq->nr_iowait);
3427                                 delayacct_blkio_start();
3428                         }
3429 
3430                         /*
3431                          * If a worker went to sleep, notify and ask workqueue
3432                          * whether it wants to wake up a task to maintain
3433                          * concurrency.
3434                          */
3435                         if (prev->flags & PF_WQ_WORKER) {
3436                                 struct task_struct *to_wakeup;
3437 
3438                                 to_wakeup = wq_worker_sleeping(prev);
3439                                 if (to_wakeup)
3440                                         try_to_wake_up_local(to_wakeup, &rf);
3441                         }
3442                 }
3443                 switch_count = &prev->nvcsw;
3444         }
3445 
3446         next = pick_next_task(rq, prev, &rf);
3447         clear_tsk_need_resched(prev);
3448         clear_preempt_need_resched();
3449 
3450         if (likely(prev != next)) {
3451                 rq->nr_switches++;
3452                 rq->curr = next;
3453                 /*
3454                  * The membarrier system call requires each architecture
3455                  * to have a full memory barrier after updating
3456                  * rq->curr, before returning to user-space.
3457                  *
3458                  * Here are the schemes providing that barrier on the
3459                  * various architectures:
3460                  * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC.
3461                  *   switch_mm() rely on membarrier_arch_switch_mm() on PowerPC.
3462                  * - finish_lock_switch() for weakly-ordered
3463                  *   architectures where spin_unlock is a full barrier,
3464                  * - switch_to() for arm64 (weakly-ordered, spin_unlock
3465                  *   is a RELEASE barrier),
3466                  */
3467                 ++*switch_count;
3468 
3469                 trace_sched_switch(preempt, prev, next);
3470 
3471                 /* Also unlocks the rq: */
3472                 rq = context_switch(rq, prev, next, &rf);
3473         } else {
3474                 rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
3475                 rq_unlock_irq(rq, &rf);
3476         }
3477 
3478         balance_callback(rq);
3479 }
3480 
3481 void __noreturn do_task_dead(void)
3482 {
3483         /* Causes final put_task_struct in finish_task_switch(): */
3484         set_special_state(TASK_DEAD);
3485 
3486         /* Tell freezer to ignore us: */
3487         current->flags |= PF_NOFREEZE;
3488 
3489         __schedule(false);
3490         BUG();
3491 
3492         /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */
3493         for (;;)
3494                 cpu_relax();
3495 }
3496 
3497 static inline void sched_submit_work(struct task_struct *tsk)
3498 {
3499         if (!tsk->state || tsk_is_pi_blocked(tsk))
3500                 return;
3501         /*
3502          * If we are going to sleep and we have plugged IO queued,
3503          * make sure to submit it to avoid deadlocks.
3504          */
3505         if (blk_needs_flush_plug(tsk))
3506                 blk_schedule_flush_plug(tsk);
3507 }
3508 
3509 asmlinkage __visible void __sched schedule(void)
3510 {
3511         struct task_struct *tsk = current;
3512 
3513         sched_submit_work(tsk);
3514         do {
3515                 preempt_disable();
3516                 __schedule(false);
3517                 sched_preempt_enable_no_resched();
3518         } while (need_resched());
3519 }
3520 EXPORT_SYMBOL(schedule);
3521 
3522 /*
3523  * synchronize_rcu_tasks() makes sure that no task is stuck in preempted
3524  * state (have scheduled out non-voluntarily) by making sure that all
3525  * tasks have either left the run queue or have gone into user space.
3526  * As idle tasks do not do either, they must not ever be preempted
3527  * (schedule out non-voluntarily).
3528  *
3529  * schedule_idle() is similar to schedule_preempt_disable() except that it
3530  * never enables preemption because it does not call sched_submit_work().
3531  */
3532 void __sched schedule_idle(void)
3533 {
3534         /*
3535          * As this skips calling sched_submit_work(), which the idle task does
3536          * regardless because that function is a nop when the task is in a
3537          * TASK_RUNNING state, make sure this isn't used someplace that the
3538          * current task can be in any other state. Note, idle is always in the
3539          * TASK_RUNNING state.
3540          */
3541         WARN_ON_ONCE(current->state);
3542         do {
3543                 __schedule(false);
3544         } while (need_resched());
3545 }
3546 
3547 #ifdef CONFIG_CONTEXT_TRACKING
3548 asmlinkage __visible void __sched schedule_user(void)
3549 {
3550         /*
3551          * If we come here after a random call to set_need_resched(),
3552          * or we have been woken up remotely but the IPI has not yet arrived,
3553          * we haven't yet exited the RCU idle mode. Do it here manually until
3554          * we find a better solution.
3555          *
3556          * NB: There are buggy callers of this function.  Ideally we
3557          * should warn if prev_state != CONTEXT_USER, but that will trigger
3558          * too frequently to make sense yet.
3559          */
3560         enum ctx_state prev_state = exception_enter();
3561         schedule();
3562         exception_exit(prev_state);
3563 }
3564 #endif
3565 
3566 /**
3567  * schedule_preempt_disabled - called with preemption disabled
3568  *
3569  * Returns with preemption disabled. Note: preempt_count must be 1
3570  */
3571 void __sched schedule_preempt_disabled(void)
3572 {
3573         sched_preempt_enable_no_resched();
3574         schedule();
3575         preempt_disable();
3576 }
3577 
3578 static void __sched notrace preempt_schedule_common(void)
3579 {
3580         do {
3581                 /*
3582                  * Because the function tracer can trace preempt_count_sub()
3583                  * and it also uses preempt_enable/disable_notrace(), if
3584                  * NEED_RESCHED is set, the preempt_enable_notrace() called
3585                  * by the function tracer will call this function again and
3586                  * cause infinite recursion.
3587                  *
3588                  * Preemption must be disabled here before the function
3589                  * tracer can trace. Break up preempt_disable() into two
3590                  * calls. One to disable preemption without fear of being
3591                  * traced. The other to still record the preemption latency,
3592                  * which can also be traced by the function tracer.
3593                  */
3594                 preempt_disable_notrace();
3595                 preempt_latency_start(1);
3596                 __schedule(true);
3597                 preempt_latency_stop(1);
3598                 preempt_enable_no_resched_notrace();
3599 
3600                 /*
3601                  * Check again in case we missed a preemption opportunity
3602                  * between schedule and now.
3603                  */
3604         } while (need_resched());
3605 }
3606 
3607 #ifdef CONFIG_PREEMPT
3608 /*
3609  * this is the entry point to schedule() from in-kernel preemption
3610  * off of preempt_enable. Kernel preemptions off return from interrupt
3611  * occur there and call schedule directly.
3612  */
3613 asmlinkage __visible void __sched notrace preempt_schedule(void)
3614 {
3615         /*
3616          * If there is a non-zero preempt_count or interrupts are disabled,
3617          * we do not want to preempt the current task. Just return..
3618          */
3619         if (likely(!preemptible()))
3620                 return;
3621 
3622         preempt_schedule_common();
3623 }
3624 NOKPROBE_SYMBOL(preempt_schedule);
3625 EXPORT_SYMBOL(preempt_schedule);
3626 
3627 /**
3628  * preempt_schedule_notrace - preempt_schedule called by tracing
3629  *
3630  * The tracing infrastructure uses preempt_enable_notrace to prevent
3631  * recursion and tracing preempt enabling caused by the tracing
3632  * infrastructure itself. But as tracing can happen in areas coming
3633  * from userspace or just about to enter userspace, a preempt enable
3634  * can occur before user_exit() is called. This will cause the scheduler
3635  * to be called when the system is still in usermode.
3636  *
3637  * To prevent this, the preempt_enable_notrace will use this function
3638  * instead of preempt_schedule() to exit user context if needed before
3639  * calling the scheduler.
3640  */
3641 asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
3642 {
3643         enum ctx_state prev_ctx;
3644 
3645         if (likely(!preemptible()))
3646                 return;
3647 
3648         do {
3649                 /*
3650                  * Because the function tracer can trace preempt_count_sub()
3651                  * and it also uses preempt_enable/disable_notrace(), if
3652                  * NEED_RESCHED is set, the preempt_enable_notrace() called
3653                  * by the function tracer will call this function again and
3654                  * cause infinite recursion.
3655                  *
3656                  * Preemption must be disabled here before the function
3657                  * tracer can trace. Break up preempt_disable() into two
3658                  * calls. One to disable preemption without fear of being
3659                  * traced. The other to still record the preemption latency,
3660                  * which can also be traced by the function tracer.
3661                  */
3662                 preempt_disable_notrace();
3663                 preempt_latency_start(1);
3664                 /*
3665                  * Needs preempt disabled in case user_exit() is traced
3666                  * and the tracer calls preempt_enable_notrace() causing
3667                  * an infinite recursion.
3668                  */
3669                 prev_ctx = exception_enter();
3670                 __schedule(true);
3671                 exception_exit(prev_ctx);
3672 
3673                 preempt_latency_stop(1);
3674                 preempt_enable_no_resched_notrace();
3675         } while (need_resched());
3676 }
3677 EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
3678 
3679 #endif /* CONFIG_PREEMPT */
3680 
3681 /*
3682  * this is the entry point to schedule() from kernel preemption
3683  * off of irq context.
3684  * Note, that this is called and return with irqs disabled. This will
3685  * protect us against recursive calling from irq.
3686  */
3687 asmlinkage __visible void __sched preempt_schedule_irq(void)
3688 {
3689         enum ctx_state prev_state;
3690 
3691         /* Catch callers which need to be fixed */
3692         BUG_ON(preempt_count() || !irqs_disabled());
3693 
3694         prev_state = exception_enter();
3695 
3696         do {
3697                 preempt_disable();
3698                 local_irq_enable();
3699                 __schedule(true);
3700                 local_irq_disable();
3701                 sched_preempt_enable_no_resched();
3702         } while (need_resched());
3703 
3704         exception_exit(prev_state);
3705 }
3706 
3707 int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags,
3708                           void *key)
3709 {
3710         return try_to_wake_up(curr->private, mode, wake_flags);
3711 }
3712 EXPORT_SYMBOL(default_wake_function);
3713 
3714 #ifdef CONFIG_RT_MUTEXES
3715 
3716 static inline int __rt_effective_prio(struct task_struct *pi_task, int prio)
3717 {
3718         if (pi_task)
3719                 prio = min(prio, pi_task->prio);
3720 
3721         return prio;
3722 }
3723 
3724 static inline int rt_effective_prio(struct task_struct *p, int prio)
3725 {
3726         struct task_struct *pi_task = rt_mutex_get_top_task(p);
3727 
3728         return __rt_effective_prio(pi_task, prio);
3729 }
3730 
3731 /*
3732  * rt_mutex_setprio - set the current priority of a task
3733  * @p: task to boost
3734  * @pi_task: donor task
3735  *
3736  * This function changes the 'effective' priority of a task. It does
3737  * not touch ->normal_prio like __setscheduler().
3738  *
3739  * Used by the rt_mutex code to implement priority inheritance
3740  * logic. Call site only calls if the priority of the task changed.
3741  */
3742 void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
3743 {
3744         int prio, oldprio, queued, running, queue_flag =
3745                 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
3746         const struct sched_class *prev_class;
3747         struct rq_flags rf;
3748         struct rq *rq;
3749 
3750         /* XXX used to be waiter->prio, not waiter->task->prio */
3751         prio = __rt_effective_prio(pi_task, p->normal_prio);
3752 
3753         /*
3754          * If nothing changed; bail early.
3755          */
3756         if (p->pi_top_task == pi_task && prio == p->prio && !dl_prio(prio))
3757                 return;
3758 
3759         rq = __task_rq_lock(p, &rf);
3760         update_rq_clock(rq);
3761         /*
3762          * Set under pi_lock && rq->lock, such that the value can be used under
3763          * either lock.
3764          *
3765          * Note that there is loads of tricky to make this pointer cache work
3766          * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to
3767          * ensure a task is de-boosted (pi_task is set to NULL) before the
3768          * task is allowed to run again (and can exit). This ensures the pointer
3769          * points to a blocked task -- which guaratees the task is present.
3770          */
3771         p->pi_top_task = pi_task;
3772 
3773         /*
3774          * For FIFO/RR we only need to set prio, if that matches we're done.
3775          */
3776         if (prio == p->prio && !dl_prio(prio))
3777                 goto out_unlock;
3778 
3779         /*
3780          * Idle task boosting is a nono in general. There is one
3781          * exception, when PREEMPT_RT and NOHZ is active:
3782          *
3783          * The idle task calls get_next_timer_interrupt() and holds
3784          * the timer wheel base->lock on the CPU and another CPU wants
3785          * to access the timer (probably to cancel it). We can safely
3786          * ignore the boosting request, as the idle CPU runs this code
3787          * with interrupts disabled and will complete the lock
3788          * protected section without being interrupted. So there is no
3789          * real need to boost.
3790          */
3791         if (unlikely(p == rq->idle)) {
3792                 WARN_ON(p != rq->curr);
3793                 WARN_ON(p->pi_blocked_on);
3794                 goto out_unlock;
3795         }
3796 
3797         trace_sched_pi_setprio(p, pi_task);
3798         oldprio = p->prio;
3799 
3800         if (oldprio == prio)
3801                 queue_flag &= ~DEQUEUE_MOVE;
3802 
3803         prev_class = p->sched_class;
3804         queued = task_on_rq_queued(p);
3805         running = task_current(rq, p);
3806         if (queued)
3807                 dequeue_task(rq, p, queue_flag);
3808         if (running)
3809                 put_prev_task(rq, p);
3810 
3811         /*
3812          * Boosting condition are:
3813          * 1. -rt task is running and holds mutex A
3814          *      --> -dl task blocks on mutex A
3815          *
3816          * 2. -dl task is running and holds mutex A
3817          *      --> -dl task blocks on mutex A and could preempt the
3818          *          running task
3819          */
3820         if (dl_prio(prio)) {
3821                 if (!dl_prio(p->normal_prio) ||
3822                     (pi_task && dl_entity_preempt(&pi_task->dl, &p->dl))) {
3823                         p->dl.dl_boosted = 1;
3824                         queue_flag |= ENQUEUE_REPLENISH;
3825                 } else
3826                         p->dl.dl_boosted = 0;
3827                 p->sched_class = &dl_sched_class;
3828         } else if (rt_prio(prio)) {
3829                 if (dl_prio(oldprio))
3830                         p->dl.dl_boosted = 0;
3831                 if (oldprio < prio)
3832                         queue_flag |= ENQUEUE_HEAD;
3833                 p->sched_class = &rt_sched_class;
3834         } else {
3835                 if (dl_prio(oldprio))
3836                         p->dl.dl_boosted = 0;
3837                 if (rt_prio(oldprio))
3838                         p->rt.timeout = 0;
3839                 p->sched_class = &fair_sched_class;
3840         }
3841 
3842         p->prio = prio;
3843 
3844         if (queued)
3845                 enqueue_task(rq, p, queue_flag);
3846         if (running)
3847                 set_curr_task(rq, p);
3848 
3849         check_class_changed(rq, p, prev_class, oldprio);
3850 out_unlock:
3851         /* Avoid rq from going away on us: */
3852         preempt_disable();
3853         __task_rq_unlock(rq, &rf);
3854 
3855         balance_callback(rq);
3856         preempt_enable();
3857 }
3858 #else
3859 static inline int rt_effective_prio(struct task_struct *p, int prio)
3860 {
3861         return prio;
3862 }
3863 #endif
3864 
3865 void set_user_nice(struct task_struct *p, long nice)
3866 {
3867         bool queued, running;
3868         int old_prio, delta;
3869         struct rq_flags rf;
3870         struct rq *rq;
3871 
3872         if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
3873                 return;
3874         /*
3875          * We have to be careful, if called from sys_setpriority(),
3876          * the task might be in the middle of scheduling on another CPU.
3877          */
3878         rq = task_rq_lock(p, &rf);
3879         update_rq_clock(rq);
3880 
3881         /*
3882          * The RT priorities are set via sched_setscheduler(), but we still
3883          * allow the 'normal' nice value to be set - but as expected
3884          * it wont have any effect on scheduling until the task is
3885          * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
3886          */
3887         if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
3888                 p->static_prio = NICE_TO_PRIO(nice);
3889                 goto out_unlock;
3890         }
3891         queued = task_on_rq_queued(p);
3892         running = task_current(rq, p);
3893         if (queued)
3894                 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
3895         if (running)
3896                 put_prev_task(rq, p);
3897 
3898         p->static_prio = NICE_TO_PRIO(nice);
3899         set_load_weight(p, true);
3900         old_prio = p->prio;
3901         p->prio = effective_prio(p);
3902         delta = p->prio - old_prio;
3903 
3904         if (queued) {
3905                 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
3906                 /*
3907                  * If the task increased its priority or is running and
3908                  * lowered its priority, then reschedule its CPU:
3909                  */
3910                 if (delta < 0 || (delta > 0 && task_running(rq, p)))
3911                         resched_curr(rq);
3912         }
3913         if (running)
3914                 set_curr_task(rq, p);
3915 out_unlock:
3916         task_rq_unlock(rq, p, &rf);
3917 }
3918 EXPORT_SYMBOL(set_user_nice);
3919 
3920 /*
3921  * can_nice - check if a task can reduce its nice value
3922  * @p: task
3923  * @nice: nice value
3924  */
3925 int can_nice(const struct task_struct *p, const int nice)
3926 {
3927         /* Convert nice value [19,-20] to rlimit style value [1,40]: */
3928         int nice_rlim = nice_to_rlimit(nice);
3929 
3930         return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) ||
3931                 capable(CAP_SYS_NICE));
3932 }
3933 
3934 #ifdef __ARCH_WANT_SYS_NICE
3935 
3936 /*
3937  * sys_nice - change the priority of the current process.
3938  * @increment: priority increment
3939  *
3940  * sys_setpriority is a more generic, but much slower function that
3941  * does similar things.
3942  */
3943 SYSCALL_DEFINE1(nice, int, increment)
3944 {
3945         long nice, retval;
3946         if (!ccs_capable(CCS_SYS_NICE))
3947                 return -EPERM;
3948 
3949         /*
3950          * Setpriority might change our priority at the same moment.
3951          * We don't have to worry. Conceptually one call occurs first
3952          * and we have a single winner.
3953          */
3954         increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
3955         nice = task_nice(current) + increment;
3956 
3957         nice = clamp_val(nice, MIN_NICE, MAX_NICE);
3958         if (increment < 0 && !can_nice(current, nice))
3959                 return -EPERM;
3960 
3961         retval = security_task_setnice(current, nice);
3962         if (retval)
3963                 return retval;
3964 
3965         set_user_nice(current, nice);
3966         return 0;
3967 }
3968 
3969 #endif
3970 
3971 /**
3972  * task_prio - return the priority value of a given task.
3973  * @p: the task in question.
3974  *
3975  * Return: The priority value as seen by users in /proc.
3976  * RT tasks are offset by -200. Normal tasks are centered
3977  * around 0, value goes from -16 to +15.
3978  */
3979 int task_prio(const struct task_struct *p)
3980 {
3981         return p->prio - MAX_RT_PRIO;
3982 }
3983 
3984 /**
3985  * idle_cpu - is a given CPU idle currently?
3986  * @cpu: the processor in question.
3987  *
3988  * Return: 1 if the CPU is currently idle. 0 otherwise.
3989  */
3990 int idle_cpu(int cpu)
3991 {
3992         struct rq *rq = cpu_rq(cpu);
3993 
3994         if (rq->curr != rq->idle)
3995                 return 0;
3996 
3997         if (rq->nr_running)
3998                 return 0;
3999 
4000 #ifdef CONFIG_SMP
4001         if (!llist_empty(&rq->wake_list))
4002                 return 0;
4003 #endif
4004 
4005         return 1;
4006 }
4007 
4008 /**
4009  * available_idle_cpu - is a given CPU idle for enqueuing work.
4010  * @cpu: the CPU in question.
4011  *
4012  * Return: 1 if the CPU is currently idle. 0 otherwise.
4013  */
4014 int available_idle_cpu(int cpu)
4015 {
4016         if (!idle_cpu(cpu))
4017                 return 0;
4018 
4019         if (vcpu_is_preempted(cpu))
4020                 return 0;
4021 
4022         return 1;
4023 }
4024 
4025 /**
4026  * idle_task - return the idle task for a given CPU.
4027  * @cpu: the processor in question.
4028  *
4029  * Return: The idle task for the CPU @cpu.
4030  */
4031 struct task_struct *idle_task(int cpu)
4032 {
4033         return cpu_rq(cpu)->idle;
4034 }
4035 
4036 /**
4037  * find_process_by_pid - find a process with a matching PID value.
4038  * @pid: the pid in question.
4039  *
4040  * The task of @pid, if found. %NULL otherwise.
4041  */
4042 static struct task_struct *find_process_by_pid(pid_t pid)
4043 {
4044         return pid ? find_task_by_vpid(pid) : current;
4045 }
4046 
4047 /*
4048  * sched_setparam() passes in -1 for its policy, to let the functions
4049  * it calls know not to change it.
4050  */
4051 #define SETPARAM_POLICY -1
4052 
4053 static void __setscheduler_params(struct task_struct *p,
4054                 const struct sched_attr *attr)
4055 {
4056         int policy = attr->sched_policy;
4057 
4058         if (policy == SETPARAM_POLICY)
4059                 policy = p->policy;
4060 
4061         p->policy = policy;
4062 
4063         if (dl_policy(policy))
4064                 __setparam_dl(p, attr);
4065         else if (fair_policy(policy))
4066                 p->static_prio = NICE_TO_PRIO(attr->sched_nice);
4067 
4068         /*
4069          * __sched_setscheduler() ensures attr->sched_priority == 0 when
4070          * !rt_policy. Always setting this ensures that things like
4071          * getparam()/getattr() don't report silly values for !rt tasks.
4072          */
4073         p->rt_priority = attr->sched_priority;
4074         p->normal_prio = normal_prio(p);
4075         set_load_weight(p, true);
4076 }
4077 
4078 /* Actually do priority change: must hold pi & rq lock. */
4079 static void __setscheduler(struct rq *rq, struct task_struct *p,
4080                            const struct sched_attr *attr, bool keep_boost)
4081 {
4082         __setscheduler_params(p, attr);
4083 
4084         /*
4085          * Keep a potential priority boosting if called from
4086          * sched_setscheduler().
4087          */
4088         p->prio = normal_prio(p);
4089         if (keep_boost)
4090                 p->prio = rt_effective_prio(p, p->prio);
4091 
4092         if (dl_prio(p->prio))
4093                 p->sched_class = &dl_sched_class;
4094         else if (rt_prio(p->prio))
4095                 p->sched_class = &rt_sched_class;
4096         else
4097                 p->sched_class = &fair_sched_class;
4098 }
4099 
4100 /*
4101  * Check the target process has a UID that matches the current process's:
4102  */
4103 static bool check_same_owner(struct task_struct *p)
4104 {
4105         const struct cred *cred = current_cred(), *pcred;
4106         bool match;
4107 
4108         rcu_read_lock();
4109         pcred = __task_cred(p);
4110         match = (uid_eq(cred->euid, pcred->euid) ||
4111                  uid_eq(cred->euid, pcred->uid));
4112         rcu_read_unlock();
4113         return match;
4114 }
4115 
4116 static int __sched_setscheduler(struct task_struct *p,
4117                                 const struct sched_attr *attr,
4118                                 bool user, bool pi)
4119 {
4120         int newprio = dl_policy(attr->sched_policy) ? MAX_DL_PRIO - 1 :
4121                       MAX_RT_PRIO - 1 - attr->sched_priority;
4122         int retval, oldprio, oldpolicy = -1, queued, running;
4123         int new_effective_prio, policy = attr->sched_policy;
4124         const struct sched_class *prev_class;
4125         struct rq_flags rf;
4126         int reset_on_fork;
4127         int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
4128         struct rq *rq;
4129 
4130         /* The pi code expects interrupts enabled */
4131         BUG_ON(pi && in_interrupt());
4132 recheck:
4133         /* Double check policy once rq lock held: */
4134         if (policy < 0) {
4135                 reset_on_fork = p->sched_reset_on_fork;
4136                 policy = oldpolicy = p->policy;
4137         } else {
4138                 reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
4139 
4140                 if (!valid_policy(policy))
4141                         return -EINVAL;
4142         }
4143 
4144         if (attr->sched_flags & ~(SCHED_FLAG_ALL | SCHED_FLAG_SUGOV))
4145                 return -EINVAL;
4146 
4147         /*
4148          * Valid priorities for SCHED_FIFO and SCHED_RR are
4149          * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
4150          * SCHED_BATCH and SCHED_IDLE is 0.
4151          */
4152         if ((p->mm && attr->sched_priority > MAX_USER_RT_PRIO-1) ||
4153             (!p->mm && attr->sched_priority > MAX_RT_PRIO-1))
4154                 return -EINVAL;
4155         if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
4156             (rt_policy(policy) != (attr->sched_priority != 0)))
4157                 return -EINVAL;
4158 
4159         /*
4160          * Allow unprivileged RT tasks to decrease priority:
4161          */
4162         if (user && !capable(CAP_SYS_NICE)) {
4163                 if (fair_policy(policy)) {
4164                         if (attr->sched_nice < task_nice(p) &&
4165                             !can_nice(p, attr->sched_nice))
4166                                 return -EPERM;
4167                 }
4168 
4169                 if (rt_policy(policy)) {
4170                         unsigned long rlim_rtprio =
4171                                         task_rlimit(p, RLIMIT_RTPRIO);
4172 
4173                         /* Can't set/change the rt policy: */
4174                         if (policy != p->policy && !rlim_rtprio)
4175                                 return -EPERM;
4176 
4177                         /* Can't increase priority: */
4178                         if (attr->sched_priority > p->rt_priority &&
4179                             attr->sched_priority > rlim_rtprio)
4180                                 return -EPERM;
4181                 }
4182 
4183                  /*
4184                   * Can't set/change SCHED_DEADLINE policy at all for now
4185                   * (safest behavior); in the future we would like to allow
4186                   * unprivileged DL tasks to increase their relative deadline
4187                   * or reduce their runtime (both ways reducing utilization)
4188                   */
4189                 if (dl_policy(policy))
4190                         return -EPERM;
4191 
4192                 /*
4193                  * Treat SCHED_IDLE as nice 20. Only allow a switch to
4194                  * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
4195                  */
4196                 if (idle_policy(p->policy) && !idle_policy(policy)) {
4197                         if (!can_nice(p, task_nice(p)))
4198                                 return -EPERM;
4199                 }
4200 
4201                 /* Can't change other user's priorities: */
4202                 if (!check_same_owner(p))
4203                         return -EPERM;
4204 
4205                 /* Normal users shall not reset the sched_reset_on_fork flag: */
4206                 if (p->sched_reset_on_fork && !reset_on_fork)
4207                         return -EPERM;
4208         }
4209 
4210         if (user) {
4211                 if (attr->sched_flags & SCHED_FLAG_SUGOV)
4212                         return -EINVAL;
4213 
4214                 retval = security_task_setscheduler(p);
4215                 if (retval)
4216                         return retval;
4217         }
4218 
4219         /*
4220          * Make sure no PI-waiters arrive (or leave) while we are
4221          * changing the priority of the task:
4222          *
4223          * To be able to change p->policy safely, the appropriate
4224          * runqueue lock must be held.
4225          */
4226         rq = task_rq_lock(p, &rf);
4227         update_rq_clock(rq);
4228 
4229         /*
4230          * Changing the policy of the stop threads its a very bad idea:
4231          */
4232         if (p == rq->stop) {
4233                 task_rq_unlock(rq, p, &rf);
4234                 return -EINVAL;
4235         }
4236 
4237         /*
4238          * If not changing anything there's no need to proceed further,
4239          * but store a possible modification of reset_on_fork.
4240          */
4241         if (unlikely(policy == p->policy)) {
4242                 if (fair_policy(policy) && attr->sched_nice != task_nice(p))
4243                         goto change;
4244                 if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
4245                         goto change;
4246                 if (dl_policy(policy) && dl_param_changed(p, attr))
4247                         goto change;
4248 
4249                 p->sched_reset_on_fork = reset_on_fork;
4250                 task_rq_unlock(rq, p, &rf);
4251                 return 0;
4252         }
4253 change:
4254 
4255         if (user) {
4256 #ifdef CONFIG_RT_GROUP_SCHED
4257                 /*
4258                  * Do not allow realtime tasks into groups that have no runtime
4259                  * assigned.
4260                  */
4261                 if (rt_bandwidth_enabled() && rt_policy(policy) &&
4262                                 task_group(p)->rt_bandwidth.rt_runtime == 0 &&
4263                                 !task_group_is_autogroup(task_group(p))) {
4264                         task_rq_unlock(rq, p, &rf);
4265                         return -EPERM;
4266                 }
4267 #endif
4268 #ifdef CONFIG_SMP
4269                 if (dl_bandwidth_enabled() && dl_policy(policy) &&
4270                                 !(attr->sched_flags & SCHED_FLAG_SUGOV)) {
4271                         cpumask_t *span = rq->rd->span;
4272 
4273                         /*
4274                          * Don't allow tasks with an affinity mask smaller than
4275                          * the entire root_domain to become SCHED_DEADLINE. We
4276                          * will also fail if there's no bandwidth available.
4277                          */
4278                         if (!cpumask_subset(span, &p->cpus_allowed) ||
4279                             rq->rd->dl_bw.bw == 0) {
4280                                 task_rq_unlock(rq, p, &rf);
4281                                 return -EPERM;
4282                         }
4283                 }
4284 #endif
4285         }
4286 
4287         /* Re-check policy now with rq lock held: */
4288         if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
4289                 policy = oldpolicy = -1;
4290                 task_rq_unlock(rq, p, &rf);
4291                 goto recheck;
4292         }
4293 
4294         /*
4295          * If setscheduling to SCHED_DEADLINE (or changing the parameters
4296          * of a SCHED_DEADLINE task) we need to check if enough bandwidth
4297          * is available.
4298          */
4299         if ((dl_policy(policy) || dl_task(p)) && sched_dl_overflow(p, policy, attr)) {
4300                 task_rq_unlock(rq, p, &rf);
4301                 return -EBUSY;
4302         }
4303 
4304         p->sched_reset_on_fork = reset_on_fork;
4305         oldprio = p->prio;
4306 
4307         if (pi) {
4308                 /*
4309                  * Take priority boosted tasks into account. If the new
4310                  * effective priority is unchanged, we just store the new
4311                  * normal parameters and do not touch the scheduler class and
4312                  * the runqueue. This will be done when the task deboost
4313                  * itself.
4314                  */
4315                 new_effective_prio = rt_effective_prio(p, newprio);
4316                 if (new_effective_prio == oldprio)
4317                         queue_flags &= ~DEQUEUE_MOVE;
4318         }
4319 
4320         queued = task_on_rq_queued(p);
4321         running = task_current(rq, p);
4322         if (queued)
4323                 dequeue_task(rq, p, queue_flags);
4324         if (running)
4325                 put_prev_task(rq, p);
4326 
4327         prev_class = p->sched_class;
4328         __setscheduler(rq, p, attr, pi);
4329 
4330         if (queued) {
4331                 /*
4332                  * We enqueue to tail when the priority of a task is
4333                  * increased (user space view).
4334                  */
4335                 if (oldprio < p->prio)
4336                         queue_flags |= ENQUEUE_HEAD;
4337 
4338                 enqueue_task(rq, p, queue_flags);
4339         }
4340         if (running)
4341                 set_curr_task(rq, p);
4342 
4343         check_class_changed(rq, p, prev_class, oldprio);
4344 
4345         /* Avoid rq from going away on us: */
4346         preempt_disable();
4347         task_rq_unlock(rq, p, &rf);
4348 
4349         if (pi)
4350                 rt_mutex_adjust_pi(p);
4351 
4352         /* Run balance callbacks after we've adjusted the PI chain: */
4353         balance_callback(rq);
4354         preempt_enable();
4355 
4356         return 0;
4357 }
4358 
4359 static int _sched_setscheduler(struct task_struct *p, int policy,
4360                                const struct sched_param *param, bool check)
4361 {
4362         struct sched_attr attr = {
4363                 .sched_policy   = policy,
4364                 .sched_priority = param->sched_priority,
4365                 .sched_nice     = PRIO_TO_NICE(p->static_prio),
4366         };
4367 
4368         /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
4369         if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
4370                 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
4371                 policy &= ~SCHED_RESET_ON_FORK;
4372                 attr.sched_policy = policy;
4373         }
4374 
4375         return __sched_setscheduler(p, &attr, check, true);
4376 }
4377 /**
4378  * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
4379  * @p: the task in question.
4380  * @policy: new policy.
4381  * @param: structure containing the new RT priority.
4382  *
4383  * Return: 0 on success. An error code otherwise.
4384  *
4385  * NOTE that the task may be already dead.
4386  */
4387 int sched_setscheduler(struct task_struct *p, int policy,
4388                        const struct sched_param *param)
4389 {
4390         return _sched_setscheduler(p, policy, param, true);
4391 }
4392 EXPORT_SYMBOL_GPL(sched_setscheduler);
4393 
4394 int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
4395 {
4396         return __sched_setscheduler(p, attr, true, true);
4397 }
4398 EXPORT_SYMBOL_GPL(sched_setattr);
4399 
4400 int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr)
4401 {
4402         return __sched_setscheduler(p, attr, false, true);
4403 }
4404 
4405 /**
4406  * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
4407  * @p: the task in question.
4408  * @policy: new policy.
4409  * @param: structure containing the new RT priority.
4410  *
4411  * Just like sched_setscheduler, only don't bother checking if the
4412  * current context has permission.  For example, this is needed in
4413  * stop_machine(): we create temporary high priority worker threads,
4414  * but our caller might not have that capability.
4415  *
4416  * Return: 0 on success. An error code otherwise.
4417  */
4418 int sched_setscheduler_nocheck(struct task_struct *p, int policy,
4419                                const struct sched_param *param)
4420 {
4421         return _sched_setscheduler(p, policy, param, false);
4422 }
4423 EXPORT_SYMBOL_GPL(sched_setscheduler_nocheck);
4424 
4425 static int
4426 do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
4427 {
4428         struct sched_param lparam;
4429         struct task_struct *p;
4430         int retval;
4431 
4432         if (!param || pid < 0)
4433                 return -EINVAL;
4434         if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
4435                 return -EFAULT;
4436 
4437         rcu_read_lock();
4438         retval = -ESRCH;
4439         p = find_process_by_pid(pid);
4440         if (p != NULL)
4441                 retval = sched_setscheduler(p, policy, &lparam);
4442         rcu_read_unlock();
4443 
4444         return retval;
4445 }
4446 
4447 /*
4448  * Mimics kernel/events/core.c perf_copy_attr().
4449  */
4450 static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr)
4451 {
4452         u32 size;
4453         int ret;
4454 
4455         if (!access_ok(VERIFY_WRITE, uattr, SCHED_ATTR_SIZE_VER0))
4456                 return -EFAULT;
4457 
4458         /* Zero the full structure, so that a short copy will be nice: */
4459         memset(attr, 0, sizeof(*attr));
4460 
4461         ret = get_user(size, &uattr->size);
4462         if (ret)
4463                 return ret;
4464 
4465         /* Bail out on silly large: */
4466         if (size > PAGE_SIZE)
4467                 goto err_size;
4468 
4469         /* ABI compatibility quirk: */
4470         if (!size)
4471                 size = SCHED_ATTR_SIZE_VER0;
4472 
4473         if (size < SCHED_ATTR_SIZE_VER0)
4474                 goto err_size;
4475 
4476         /*
4477          * If we're handed a bigger struct than we know of,
4478          * ensure all the unknown bits are 0 - i.e. new
4479          * user-space does not rely on any kernel feature
4480          * extensions we dont know about yet.
4481          */
4482         if (size > sizeof(*attr)) {
4483                 unsigned char __user *addr;
4484                 unsigned char __user *end;
4485                 unsigned char val;
4486 
4487                 addr = (void __user *)uattr + sizeof(*attr);
4488                 end  = (void __user *)uattr + size;
4489 
4490                 for (; addr < end; addr++) {
4491                         ret = get_user(val, addr);
4492                         if (ret)
4493                                 return ret;
4494                         if (val)
4495                                 goto err_size;
4496                 }
4497                 size = sizeof(*attr);
4498         }
4499 
4500         ret = copy_from_user(attr, uattr, size);
4501         if (ret)
4502                 return -EFAULT;
4503 
4504         /*
4505          * XXX: Do we want to be lenient like existing syscalls; or do we want
4506          * to be strict and return an error on out-of-bounds values?
4507          */
4508         attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE);
4509 
4510         return 0;
4511 
4512 err_size:
4513         put_user(sizeof(*attr), &uattr->size);
4514         return -E2BIG;
4515 }
4516 
4517 /**
4518  * sys_sched_setscheduler - set/change the scheduler policy and RT priority
4519  * @pid: the pid in question.
4520  * @policy: new policy.
4521  * @param: structure containing the new RT priority.
4522  *
4523  * Return: 0 on success. An error code otherwise.
4524  */
4525 SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param)
4526 {
4527         if (policy < 0)
4528                 return -EINVAL;
4529 
4530         return do_sched_setscheduler(pid, policy, param);
4531 }
4532 
4533 /**
4534  * sys_sched_setparam - set/change the RT priority of a thread
4535  * @pid: the pid in question.
4536  * @param: structure containing the new RT priority.
4537  *
4538  * Return: 0 on success. An error code otherwise.
4539  */
4540 SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
4541 {
4542         return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
4543 }
4544 
4545 /**
4546  * sys_sched_setattr - same as above, but with extended sched_attr
4547  * @pid: the pid in question.
4548  * @uattr: structure containing the extended parameters.
4549  * @flags: for future extension.
4550  */
4551 SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
4552                                unsigned int, flags)
4553 {
4554         struct sched_attr attr;
4555         struct task_struct *p;
4556         int retval;
4557 
4558         if (!uattr || pid < 0 || flags)
4559                 return -EINVAL;
4560 
4561         retval = sched_copy_attr(uattr, &attr);
4562         if (retval)
4563                 return retval;
4564 
4565         if ((int)attr.sched_policy < 0)
4566                 return -EINVAL;
4567 
4568         rcu_read_lock();
4569         retval = -ESRCH;
4570         p = find_process_by_pid(pid);
4571         if (p != NULL)
4572                 retval = sched_setattr(p, &attr);
4573         rcu_read_unlock();
4574 
4575         return retval;
4576 }
4577 
4578 /**
4579  * sys_sched_getscheduler - get the policy (scheduling class) of a thread
4580  * @pid: the pid in question.
4581  *
4582  * Return: On success, the policy of the thread. Otherwise, a negative error
4583  * code.
4584  */
4585 SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
4586 {
4587         struct task_struct *p;
4588         int retval;
4589 
4590         if (pid < 0)
4591                 return -EINVAL;
4592 
4593         retval = -ESRCH;
4594         rcu_read_lock();
4595         p = find_process_by_pid(pid);
4596         if (p) {
4597                 retval = security_task_getscheduler(p);
4598                 if (!retval)
4599                         retval = p->policy
4600                                 | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
4601         }
4602         rcu_read_unlock();
4603         return retval;
4604 }
4605 
4606 /**
4607  * sys_sched_getparam - get the RT priority of a thread
4608  * @pid: the pid in question.
4609  * @param: structure containing the RT priority.
4610  *
4611  * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
4612  * code.
4613  */
4614 SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
4615 {
4616         struct sched_param lp = { .sched_priority = 0 };
4617         struct task_struct *p;
4618         int retval;
4619 
4620         if (!param || pid < 0)
4621                 return -EINVAL;
4622 
4623         rcu_read_lock();
4624         p = find_process_by_pid(pid);
4625         retval = -ESRCH;
4626         if (!p)
4627                 goto out_unlock;
4628 
4629         retval = security_task_getscheduler(p);
4630         if (retval)
4631                 goto out_unlock;
4632 
4633         if (task_has_rt_policy(p))
4634                 lp.sched_priority = p->rt_priority;
4635         rcu_read_unlock();
4636 
4637         /*
4638          * This one might sleep, we cannot do it with a spinlock held ...
4639          */
4640         retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
4641 
4642         return retval;
4643 
4644 out_unlock:
4645         rcu_read_unlock();
4646         return retval;
4647 }
4648 
4649 static int sched_read_attr(struct sched_attr __user *uattr,
4650                            struct sched_attr *attr,
4651                            unsigned int usize)
4652 {
4653         int ret;
4654 
4655         if (!access_ok(VERIFY_WRITE, uattr, usize))
4656                 return -EFAULT;
4657 
4658         /*
4659          * If we're handed a smaller struct than we know of,
4660          * ensure all the unknown bits are 0 - i.e. old
4661          * user-space does not get uncomplete information.
4662          */
4663         if (usize < sizeof(*attr)) {
4664                 unsigned char *addr;
4665                 unsigned char *end;
4666 
4667                 addr = (void *)attr + usize;
4668                 end  = (void *)attr + sizeof(*attr);
4669 
4670                 for (; addr < end; addr++) {
4671                         if (*addr)
4672                                 return -EFBIG;
4673                 }
4674 
4675                 attr->size = usize;
4676         }
4677 
4678         ret = copy_to_user(uattr, attr, attr->size);
4679         if (ret)
4680                 return -EFAULT;
4681 
4682         return 0;
4683 }
4684 
4685 /**
4686  * sys_sched_getattr - similar to sched_getparam, but with sched_attr
4687  * @pid: the pid in question.
4688  * @uattr: structure containing the extended parameters.
4689  * @size: sizeof(attr) for fwd/bwd comp.
4690  * @flags: for future extension.
4691  */
4692 SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
4693                 unsigned int, size, unsigned int, flags)
4694 {
4695         struct sched_attr attr = {
4696                 .size = sizeof(struct sched_attr),
4697         };
4698         struct task_struct *p;
4699         int retval;
4700 
4701         if (!uattr || pid < 0 || size > PAGE_SIZE ||
4702             size < SCHED_ATTR_SIZE_VER0 || flags)
4703                 return -EINVAL;
4704 
4705         rcu_read_lock();
4706         p = find_process_by_pid(pid);
4707         retval = -ESRCH;
4708         if (!p)
4709                 goto out_unlock;
4710 
4711         retval = security_task_getscheduler(p);
4712         if (retval)
4713                 goto out_unlock;
4714 
4715         attr.sched_policy = p->policy;
4716         if (p->sched_reset_on_fork)
4717                 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
4718         if (task_has_dl_policy(p))
4719                 __getparam_dl(p, &attr);
4720         else if (task_has_rt_policy(p))
4721                 attr.sched_priority = p->rt_priority;
4722         else
4723                 attr.sched_nice = task_nice(p);
4724 
4725         rcu_read_unlock();
4726 
4727         retval = sched_read_attr(uattr, &attr, size);
4728         return retval;
4729 
4730 out_unlock:
4731         rcu_read_unlock();
4732         return retval;
4733 }
4734 
4735 long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
4736 {
4737         cpumask_var_t cpus_allowed, new_mask;
4738         struct task_struct *p;
4739         int retval;
4740 
4741         rcu_read_lock();
4742 
4743         p = find_process_by_pid(pid);
4744         if (!p) {
4745                 rcu_read_unlock();
4746                 return -ESRCH;
4747         }
4748 
4749         /* Prevent p going away */
4750         get_task_struct(p);
4751         rcu_read_unlock();
4752 
4753         if (p->flags & PF_NO_SETAFFINITY) {
4754                 retval = -EINVAL;
4755                 goto out_put_task;
4756         }
4757         if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
4758                 retval = -ENOMEM;
4759                 goto out_put_task;
4760         }
4761         if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
4762                 retval = -ENOMEM;
4763                 goto out_free_cpus_allowed;
4764         }
4765         retval = -EPERM;
4766         if (!check_same_owner(p)) {
4767                 rcu_read_lock();
4768                 if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
4769                         rcu_read_unlock();
4770                         goto out_free_new_mask;
4771                 }
4772                 rcu_read_unlock();
4773         }
4774 
4775         retval = security_task_setscheduler(p);
4776         if (retval)
4777                 goto out_free_new_mask;
4778 
4779 
4780         cpuset_cpus_allowed(p, cpus_allowed);
4781         cpumask_and(new_mask, in_mask, cpus_allowed);
4782 
4783         /*
4784          * Since bandwidth control happens on root_domain basis,
4785          * if admission test is enabled, we only admit -deadline
4786          * tasks allowed to run on all the CPUs in the task's
4787          * root_domain.
4788          */
4789 #ifdef CONFIG_SMP
4790         if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
4791                 rcu_read_lock();
4792                 if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) {
4793                         retval = -EBUSY;
4794                         rcu_read_unlock();
4795                         goto out_free_new_mask;
4796                 }
4797                 rcu_read_unlock();
4798         }
4799 #endif
4800 again:
4801         retval = __set_cpus_allowed_ptr(p, new_mask, true);
4802 
4803         if (!retval) {
4804                 cpuset_cpus_allowed(p, cpus_allowed);
4805                 if (!cpumask_subset(new_mask, cpus_allowed)) {
4806                         /*
4807                          * We must have raced with a concurrent cpuset
4808                          * update. Just reset the cpus_allowed to the
4809                          * cpuset's cpus_allowed
4810                          */
4811                         cpumask_copy(new_mask, cpus_allowed);
4812                         goto again;
4813                 }
4814         }
4815 out_free_new_mask:
4816         free_cpumask_var(new_mask);
4817 out_free_cpus_allowed:
4818         free_cpumask_var(cpus_allowed);
4819 out_put_task:
4820         put_task_struct(p);
4821         return retval;
4822 }
4823 
4824 static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
4825                              struct cpumask *new_mask)
4826 {
4827         if (len < cpumask_size())
4828                 cpumask_clear(new_mask);
4829         else if (len > cpumask_size())
4830                 len = cpumask_size();
4831 
4832         return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
4833 }
4834 
4835 /**
4836  * sys_sched_setaffinity - set the CPU affinity of a process
4837  * @pid: pid of the process
4838  * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4839  * @user_mask_ptr: user-space pointer to the new CPU mask
4840  *
4841  * Return: 0 on success. An error code otherwise.
4842  */
4843 SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
4844                 unsigned long __user *, user_mask_ptr)
4845 {
4846         cpumask_var_t new_mask;
4847         int retval;
4848 
4849         if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
4850                 return -ENOMEM;
4851 
4852         retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
4853         if (retval == 0)
4854                 retval = sched_setaffinity(pid, new_mask);
4855         free_cpumask_var(new_mask);
4856         return retval;
4857 }
4858 
4859 long sched_getaffinity(pid_t pid, struct cpumask *mask)
4860 {
4861         struct task_struct *p;
4862         unsigned long flags;
4863         int retval;
4864 
4865         rcu_read_lock();
4866 
4867         retval = -ESRCH;
4868         p = find_process_by_pid(pid);
4869         if (!p)
4870                 goto out_unlock;
4871 
4872         retval = security_task_getscheduler(p);
4873         if (retval)
4874                 goto out_unlock;
4875 
4876         raw_spin_lock_irqsave(&p->pi_lock, flags);
4877         cpumask_and(mask, &p->cpus_allowed, cpu_active_mask);
4878         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
4879 
4880 out_unlock:
4881         rcu_read_unlock();
4882 
4883         return retval;
4884 }
4885 
4886 /**
4887  * sys_sched_getaffinity - get the CPU affinity of a process
4888  * @pid: pid of the process
4889  * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4890  * @user_mask_ptr: user-space pointer to hold the current CPU mask
4891  *
4892  * Return: size of CPU mask copied to user_mask_ptr on success. An
4893  * error code otherwise.
4894  */
4895 SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
4896                 unsigned long __user *, user_mask_ptr)
4897 {
4898         int ret;
4899         cpumask_var_t mask;
4900 
4901         if ((len * BITS_PER_BYTE) < nr_cpu_ids)
4902                 return -EINVAL;
4903         if (len & (sizeof(unsigned long)-1))
4904                 return -EINVAL;
4905 
4906         if (!alloc_cpumask_var(&mask, GFP_KERNEL))
4907                 return -ENOMEM;
4908 
4909         ret = sched_getaffinity(pid, mask);
4910         if (ret == 0) {
4911                 unsigned int retlen = min(len, cpumask_size());
4912 
4913                 if (copy_to_user(user_mask_ptr, mask, retlen))
4914                         ret = -EFAULT;
4915                 else
4916                         ret = retlen;
4917         }
4918         free_cpumask_var(mask);
4919 
4920         return ret;
4921 }
4922 
4923 /**
4924  * sys_sched_yield - yield the current processor to other threads.
4925  *
4926  * This function yields the current CPU to other tasks. If there are no
4927  * other threads running on this CPU then this function will return.
4928  *
4929  * Return: 0.
4930  */
4931 static void do_sched_yield(void)
4932 {
4933         struct rq_flags rf;
4934         struct rq *rq;
4935 
4936         rq = this_rq_lock_irq(&rf);
4937 
4938         schedstat_inc(rq->yld_count);
4939         current->sched_class->yield_task(rq);
4940 
4941         /*
4942          * Since we are going to call schedule() anyway, there's
4943          * no need to preempt or enable interrupts:
4944          */
4945         preempt_disable();
4946         rq_unlock(rq, &rf);
4947         sched_preempt_enable_no_resched();
4948 
4949         schedule();
4950 }
4951 
4952 SYSCALL_DEFINE0(sched_yield)
4953 {
4954         do_sched_yield();
4955         return 0;
4956 }
4957 
4958 #ifndef CONFIG_PREEMPT
4959 int __sched _cond_resched(void)
4960 {
4961         if (should_resched(0)) {
4962                 preempt_schedule_common();
4963                 return 1;
4964         }
4965         rcu_all_qs();
4966         return 0;
4967 }
4968 EXPORT_SYMBOL(_cond_resched);
4969 #endif
4970 
4971 /*
4972  * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
4973  * call schedule, and on return reacquire the lock.
4974  *
4975  * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
4976  * operations here to prevent schedule() from being called twice (once via
4977  * spin_unlock(), once by hand).
4978  */
4979 int __cond_resched_lock(spinlock_t *lock)
4980 {
4981         int resched = should_resched(PREEMPT_LOCK_OFFSET);
4982         int ret = 0;
4983 
4984         lockdep_assert_held(lock);
4985 
4986         if (spin_needbreak(lock) || resched) {
4987                 spin_unlock(lock);
4988                 if (resched)
4989                         preempt_schedule_common();
4990                 else
4991                         cpu_relax();
4992                 ret = 1;
4993                 spin_lock(lock);
4994         }
4995         return ret;
4996 }
4997 EXPORT_SYMBOL(__cond_resched_lock);
4998 
4999 /**
5000  * yield - yield the current processor to other threads.
5001  *
5002  * Do not ever use this function, there's a 99% chance you're doing it wrong.
5003  *
5004  * The scheduler is at all times free to pick the calling task as the most
5005  * eligible task to run, if removing the yield() call from your code breaks
5006  * it, its already broken.
5007  *
5008  * Typical broken usage is:
5009  *
5010  * while (!event)
5011  *      yield();
5012  *
5013  * where one assumes that yield() will let 'the other' process run that will
5014  * make event true. If the current task is a SCHED_FIFO task that will never
5015  * happen. Never use yield() as a progress guarantee!!
5016  *
5017  * If you want to use yield() to wait for something, use wait_event().
5018  * If you want to use yield() to be 'nice' for others, use cond_resched().
5019  * If you still want to use yield(), do not!
5020  */
5021 void __sched yield(void)
5022 {
5023         set_current_state(TASK_RUNNING);
5024         do_sched_yield();
5025 }
5026 EXPORT_SYMBOL(yield);
5027 
5028 /**
5029  * yield_to - yield the current processor to another thread in
5030  * your thread group, or accelerate that thread toward the
5031  * processor it's on.
5032  * @p: target task
5033  * @preempt: whether task preemption is allowed or not
5034  *
5035  * It's the caller's job to ensure that the target task struct
5036  * can't go away on us before we can do any checks.
5037  *
5038  * Return:
5039  *      true (>0) if we indeed boosted the target task.
5040  *      false (0) if we failed to boost the target.
5041  *      -ESRCH if there's no task to yield to.
5042  */
5043 int __sched yield_to(struct task_struct *p, bool preempt)
5044 {
5045         struct task_struct *curr = current;
5046         struct rq *rq, *p_rq;
5047         unsigned long flags;
5048         int yielded = 0;
5049 
5050         local_irq_save(flags);
5051         rq = this_rq();
5052 
5053 again:
5054         p_rq = task_rq(p);
5055         /*
5056          * If we're the only runnable task on the rq and target rq also
5057          * has only one task, there's absolutely no point in yielding.
5058          */
5059         if (rq->nr_running == 1 && p_rq->nr_running == 1) {
5060                 yielded = -ESRCH;
5061                 goto out_irq;
5062         }
5063 
5064         double_rq_lock(rq, p_rq);
5065         if (task_rq(p) != p_rq) {
5066                 double_rq_unlock(rq, p_rq);
5067                 goto again;
5068         }
5069 
5070         if (!curr->sched_class->yield_to_task)
5071                 goto out_unlock;
5072 
5073         if (curr->sched_class != p->sched_class)
5074                 goto out_unlock;
5075 
5076         if (task_running(p_rq, p) || p->state)
5077                 goto out_unlock;
5078 
5079         yielded = curr->sched_class->yield_to_task(rq, p, preempt);
5080         if (yielded) {
5081                 schedstat_inc(rq->yld_count);
5082                 /*
5083                  * Make p's CPU reschedule; pick_next_entity takes care of
5084                  * fairness.
5085                  */
5086                 if (preempt && rq != p_rq)
5087                         resched_curr(p_rq);
5088         }
5089 
5090 out_unlock:
5091         double_rq_unlock(rq, p_rq);
5092 out_irq:
5093         local_irq_restore(flags);
5094 
5095         if (yielded > 0)
5096                 schedule();
5097 
5098         return yielded;
5099 }
5100 EXPORT_SYMBOL_GPL(yield_to);
5101 
5102 int io_schedule_prepare(void)
5103 {
5104         int old_iowait = current->in_iowait;
5105 
5106         current->in_iowait = 1;
5107         blk_schedule_flush_plug(current);
5108 
5109         return old_iowait;
5110 }
5111 
5112 void io_schedule_finish(int token)
5113 {
5114         current->in_iowait = token;
5115 }
5116 
5117 /*
5118  * This task is about to go to sleep on IO. Increment rq->nr_iowait so
5119  * that process accounting knows that this is a task in IO wait state.
5120  */
5121 long __sched io_schedule_timeout(long timeout)
5122 {
5123         int token;
5124         long ret;
5125 
5126         token = io_schedule_prepare();
5127         ret = schedule_timeout(timeout);
5128         io_schedule_finish(token);
5129 
5130         return ret;
5131 }
5132 EXPORT_SYMBOL(io_schedule_timeout);
5133 
5134 void io_schedule(void)
5135 {
5136         int token;
5137 
5138         token = io_schedule_prepare();
5139         schedule();
5140         io_schedule_finish(token);
5141 }
5142 EXPORT_SYMBOL(io_schedule);
5143 
5144 /**
5145  * sys_sched_get_priority_max - return maximum RT priority.
5146  * @policy: scheduling class.
5147  *
5148  * Return: On success, this syscall returns the maximum
5149  * rt_priority that can be used by a given scheduling class.
5150  * On failure, a negative error code is returned.
5151  */
5152 SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
5153 {
5154         int ret = -EINVAL;
5155 
5156         switch (policy) {
5157         case SCHED_FIFO:
5158         case SCHED_RR:
5159                 ret = MAX_USER_RT_PRIO-1;
5160                 break;
5161         case SCHED_DEADLINE:
5162         case SCHED_NORMAL:
5163         case SCHED_BATCH:
5164         case SCHED_IDLE:
5165                 ret = 0;
5166                 break;
5167         }
5168         return ret;
5169 }
5170 
5171 /**
5172  * sys_sched_get_priority_min - return minimum RT priority.
5173  * @policy: scheduling class.
5174  *
5175  * Return: On success, this syscall returns the minimum
5176  * rt_priority that can be used by a given scheduling class.
5177  * On failure, a negative error code is returned.
5178  */
5179 SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
5180 {
5181         int ret = -EINVAL;
5182 
5183         switch (policy) {
5184         case SCHED_FIFO:
5185         case SCHED_RR:
5186                 ret = 1;
5187                 break;
5188         case SCHED_DEADLINE:
5189         case SCHED_NORMAL:
5190         case SCHED_BATCH:
5191         case SCHED_IDLE:
5192                 ret = 0;
5193         }
5194         return ret;
5195 }
5196 
5197 static int sched_rr_get_interval(pid_t pid, struct timespec64 *t)
5198 {
5199         struct task_struct *p;
5200         unsigned int time_slice;
5201         struct rq_flags rf;
5202         struct rq *rq;
5203         int retval;
5204 
5205         if (pid < 0)
5206                 return -EINVAL;
5207 
5208         retval = -ESRCH;
5209         rcu_read_lock();
5210         p = find_process_by_pid(pid);
5211         if (!p)
5212                 goto out_unlock;
5213 
5214         retval = security_task_getscheduler(p);
5215         if (retval)
5216                 goto out_unlock;
5217 
5218         rq = task_rq_lock(p, &rf);
5219         time_slice = 0;
5220         if (p->sched_class->get_rr_interval)
5221                 time_slice = p->sched_class->get_rr_interval(rq, p);
5222         task_rq_unlock(rq, p, &rf);
5223 
5224         rcu_read_unlock();
5225         jiffies_to_timespec64(time_slice, t);
5226         return 0;
5227 
5228 out_unlock:
5229         rcu_read_unlock();
5230         return retval;
5231 }
5232 
5233 /**
5234  * sys_sched_rr_get_interval - return the default timeslice of a process.
5235  * @pid: pid of the process.
5236  * @interval: userspace pointer to the timeslice value.
5237  *
5238  * this syscall writes the default timeslice value of a given process
5239  * into the user-space timespec buffer. A value of '' means infinity.
5240  *
5241  * Return: On success, 0 and the timeslice is in @interval. Otherwise,
5242  * an error code.
5243  */
5244 SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
5245                 struct __kernel_timespec __user *, interval)
5246 {
5247         struct timespec64 t;
5248         int retval = sched_rr_get_interval(pid, &t);
5249 
5250         if (retval == 0)
5251                 retval = put_timespec64(&t, interval);
5252 
5253         return retval;
5254 }
5255 
5256 #ifdef CONFIG_COMPAT_32BIT_TIME
5257 COMPAT_SYSCALL_DEFINE2(sched_rr_get_interval,
5258                        compat_pid_t, pid,
5259                        struct old_timespec32 __user *, interval)
5260 {
5261         struct timespec64 t;
5262         int retval = sched_rr_get_interval(pid, &t);
5263 
5264         if (retval == 0)
5265                 retval = put_old_timespec32(&t, interval);
5266         return retval;
5267 }
5268 #endif
5269 
5270 void sched_show_task(struct task_struct *p)
5271 {
5272         unsigned long free = 0;
5273         int ppid;
5274 
5275         if (!try_get_task_stack(p))
5276                 return;
5277 
5278         printk(KERN_INFO "%-15.15s %c", p->comm, task_state_to_char(p));
5279 
5280         if (p->state == TASK_RUNNING)
5281                 printk(KERN_CONT "  running task    ");
5282 #ifdef CONFIG_DEBUG_STACK_USAGE
5283         free = stack_not_used(p);
5284 #endif
5285         ppid = 0;
5286         rcu_read_lock();
5287         if (pid_alive(p))
5288                 ppid = task_pid_nr(rcu_dereference(p->real_parent));
5289         rcu_read_unlock();
5290         printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free,
5291                 task_pid_nr(p), ppid,
5292                 (unsigned long)task_thread_info(p)->flags);
5293 
5294         print_worker_info(KERN_INFO, p);
5295         show_stack(p, NULL);
5296         put_task_stack(p);
5297 }
5298 EXPORT_SYMBOL_GPL(sched_show_task);
5299 
5300 static inline bool
5301 state_filter_match(unsigned long state_filter, struct task_struct *p)
5302 {
5303         /* no filter, everything matches */
5304         if (!state_filter)
5305                 return true;
5306 
5307         /* filter, but doesn't match */
5308         if (!(p->state & state_filter))
5309                 return false;
5310 
5311         /*
5312          * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
5313          * TASK_KILLABLE).
5314          */
5315         if (state_filter == TASK_UNINTERRUPTIBLE && p->state == TASK_IDLE)
5316                 return false;
5317 
5318         return true;
5319 }
5320 
5321 
5322 void show_state_filter(unsigned long state_filter)
5323 {
5324         struct task_struct *g, *p;
5325 
5326 #if BITS_PER_LONG == 32
5327         printk(KERN_INFO
5328                 "  task                PC stack   pid father\n");
5329 #else
5330         printk(KERN_INFO
5331                 "  task                        PC stack   pid father\n");
5332 #endif
5333         rcu_read_lock();
5334         for_each_process_thread(g, p) {
5335                 /*
5336                  * reset the NMI-timeout, listing all files on a slow
5337                  * console might take a lot of time:
5338                  * Also, reset softlockup watchdogs on all CPUs, because
5339                  * another CPU might be blocked waiting for us to process
5340                  * an IPI.
5341                  */
5342                 touch_nmi_watchdog();
5343                 touch_all_softlockup_watchdogs();
5344                 if (state_filter_match(state_filter, p))
5345                         sched_show_task(p);
5346         }
5347 
5348 #ifdef CONFIG_SCHED_DEBUG
5349         if (!state_filter)
5350                 sysrq_sched_debug_show();
5351 #endif
5352         rcu_read_unlock();
5353         /*
5354          * Only show locks if all tasks are dumped:
5355          */
5356         if (!state_filter)
5357                 debug_show_all_locks();
5358 }
5359 
5360 /**
5361  * init_idle - set up an idle thread for a given CPU
5362  * @idle: task in question
5363  * @cpu: CPU the idle task belongs to
5364  *
5365  * NOTE: this function does not set the idle thread's NEED_RESCHED
5366  * flag, to make booting more robust.
5367  */
5368 void init_idle(struct task_struct *idle, int cpu)
5369 {
5370         struct rq *rq = cpu_rq(cpu);
5371         unsigned long flags;
5372 
5373         raw_spin_lock_irqsave(&idle->pi_lock, flags);
5374         raw_spin_lock(&rq->lock);
5375 
5376         __sched_fork(0, idle);
5377         idle->state = TASK_RUNNING;
5378         idle->se.exec_start = sched_clock();
5379         idle->flags |= PF_IDLE;
5380 
5381         kasan_unpoison_task_stack(idle);
5382 
5383 #ifdef CONFIG_SMP
5384         /*
5385          * Its possible that init_idle() gets called multiple times on a task,
5386          * in that case do_set_cpus_allowed() will not do the right thing.
5387          *
5388          * And since this is boot we can forgo the serialization.
5389          */
5390         set_cpus_allowed_common(idle, cpumask_of(cpu));
5391 #endif
5392         /*
5393          * We're having a chicken and egg problem, even though we are
5394          * holding rq->lock, the CPU isn't yet set to this CPU so the
5395          * lockdep check in task_group() will fail.
5396          *
5397          * Similar case to sched_fork(). / Alternatively we could
5398          * use task_rq_lock() here and obtain the other rq->lock.
5399          *
5400          * Silence PROVE_RCU
5401          */
5402         rcu_read_lock();
5403         __set_task_cpu(idle, cpu);
5404         rcu_read_unlock();
5405 
5406         rq->curr = rq->idle = idle;
5407         idle->on_rq = TASK_ON_RQ_QUEUED;
5408 #ifdef CONFIG_SMP
5409         idle->on_cpu = 1;
5410 #endif
5411         raw_spin_unlock(&rq->lock);
5412         raw_spin_unlock_irqrestore(&idle->pi_lock, flags);
5413 
5414         /* Set the preempt count _outside_ the spinlocks! */
5415         init_idle_preempt_count(idle, cpu);
5416 
5417         /*
5418          * The idle tasks have their own, simple scheduling class:
5419          */
5420         idle->sched_class = &idle_sched_class;
5421         ftrace_graph_init_idle_task(idle, cpu);
5422         vtime_init_idle(idle, cpu);
5423 #ifdef CONFIG_SMP
5424         sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
5425 #endif
5426 }
5427 
5428 #ifdef CONFIG_SMP
5429 
5430 int cpuset_cpumask_can_shrink(const struct cpumask *cur,
5431                               const struct cpumask *trial)
5432 {
5433         int ret = 1;
5434 
5435         if (!cpumask_weight(cur))
5436                 return ret;
5437 
5438         ret = dl_cpuset_cpumask_can_shrink(cur, trial);
5439 
5440         return ret;
5441 }
5442 
5443 int task_can_attach(struct task_struct *p,
5444                     const struct cpumask *cs_cpus_allowed)
5445 {
5446         int ret = 0;
5447 
5448         /*
5449          * Kthreads which disallow setaffinity shouldn't be moved
5450          * to a new cpuset; we don't want to change their CPU
5451          * affinity and isolating such threads by their set of
5452          * allowed nodes is unnecessary.  Thus, cpusets are not
5453          * applicable for such threads.  This prevents checking for
5454          * success of set_cpus_allowed_ptr() on all attached tasks
5455          * before cpus_allowed may be changed.
5456          */
5457         if (p->flags & PF_NO_SETAFFINITY) {
5458                 ret = -EINVAL;
5459                 goto out;
5460         }
5461 
5462         if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span,
5463                                               cs_cpus_allowed))
5464                 ret = dl_task_can_attach(p, cs_cpus_allowed);
5465 
5466 out:
5467         return ret;
5468 }
5469 
5470 bool sched_smp_initialized __read_mostly;
5471 
5472 #ifdef CONFIG_NUMA_BALANCING
5473 /* Migrate current task p to target_cpu */
5474 int migrate_task_to(struct task_struct *p, int target_cpu)
5475 {
5476         struct migration_arg arg = { p, target_cpu };
5477         int curr_cpu = task_cpu(p);
5478 
5479         if (curr_cpu == target_cpu)
5480                 return 0;
5481 
5482         if (!cpumask_test_cpu(target_cpu, &p->cpus_allowed))
5483                 return -EINVAL;
5484 
5485         /* TODO: This is not properly updating schedstats */
5486 
5487         trace_sched_move_numa(p, curr_cpu, target_cpu);
5488         return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
5489 }
5490 
5491 /*
5492  * Requeue a task on a given node and accurately track the number of NUMA
5493  * tasks on the runqueues
5494  */
5495 void sched_setnuma(struct task_struct *p, int nid)
5496 {
5497         bool queued, running;
5498         struct rq_flags rf;
5499         struct rq *rq;
5500 
5501         rq = task_rq_lock(p, &rf);
5502         queued = task_on_rq_queued(p);
5503         running = task_current(rq, p);
5504 
5505         if (queued)
5506                 dequeue_task(rq, p, DEQUEUE_SAVE);
5507         if (running)
5508                 put_prev_task(rq, p);
5509 
5510         p->numa_preferred_nid = nid;
5511 
5512         if (queued)
5513                 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
5514         if (running)
5515                 set_curr_task(rq, p);
5516         task_rq_unlock(rq, p, &rf);
5517 }
5518 #endif /* CONFIG_NUMA_BALANCING */
5519 
5520 #ifdef CONFIG_HOTPLUG_CPU
5521 /*
5522  * Ensure that the idle task is using init_mm right before its CPU goes
5523  * offline.
5524  */
5525 void idle_task_exit(void)
5526 {
5527         struct mm_struct *mm = current->active_mm;
5528 
5529         BUG_ON(cpu_online(smp_processor_id()));
5530 
5531         if (mm != &init_mm) {
5532                 switch_mm(mm, &init_mm, current);
5533                 current->active_mm = &init_mm;
5534                 finish_arch_post_lock_switch();
5535         }
5536         mmdrop(mm);
5537 }
5538 
5539 /*
5540  * Since this CPU is going 'away' for a while, fold any nr_active delta
5541  * we might have. Assumes we're called after migrate_tasks() so that the
5542  * nr_active count is stable. We need to take the teardown thread which
5543  * is calling this into account, so we hand in adjust = 1 to the load
5544  * calculation.
5545  *
5546  * Also see the comment "Global load-average calculations".
5547  */
5548 static void calc_load_migrate(struct rq *rq)
5549 {
5550         long delta = calc_load_fold_active(rq, 1);
5551         if (delta)
5552                 atomic_long_add(delta, &calc_load_tasks);
5553 }
5554 
5555 static void put_prev_task_fake(struct rq *rq, struct task_struct *prev)
5556 {
5557 }
5558 
5559 static const struct sched_class fake_sched_class = {
5560         .put_prev_task = put_prev_task_fake,
5561 };
5562 
5563 static struct task_struct fake_task = {
5564         /*
5565          * Avoid pull_{rt,dl}_task()
5566          */
5567         .prio = MAX_PRIO + 1,
5568         .sched_class = &fake_sched_class,
5569 };
5570 
5571 /*
5572  * Migrate all tasks from the rq, sleeping tasks will be migrated by
5573  * try_to_wake_up()->select_task_rq().
5574  *
5575  * Called with rq->lock held even though we'er in stop_machine() and
5576  * there's no concurrency possible, we hold the required locks anyway
5577  * because of lock validation efforts.
5578  */
5579 static void migrate_tasks(struct rq *dead_rq, struct rq_flags *rf)
5580 {
5581         struct rq *rq = dead_rq;
5582         struct task_struct *next, *stop = rq->stop;
5583         struct rq_flags orf = *rf;
5584         int dest_cpu;
5585 
5586         /*
5587          * Fudge the rq selection such that the below task selection loop
5588          * doesn't get stuck on the currently eligible stop task.
5589          *
5590          * We're currently inside stop_machine() and the rq is either stuck
5591          * in the stop_machine_cpu_stop() loop, or we're executing this code,
5592          * either way we should never end up calling schedule() until we're
5593          * done here.
5594          */
5595         rq->stop = NULL;
5596 
5597         /*
5598          * put_prev_task() and pick_next_task() sched
5599          * class method both need to have an up-to-date
5600          * value of rq->clock[_task]
5601          */
5602         update_rq_clock(rq);
5603 
5604         for (;;) {
5605                 /*
5606                  * There's this thread running, bail when that's the only
5607                  * remaining thread:
5608                  */
5609                 if (rq->nr_running == 1)
5610                         break;
5611 
5612                 /*
5613                  * pick_next_task() assumes pinned rq->lock:
5614                  */
5615                 next = pick_next_task(rq, &fake_task, rf);
5616                 BUG_ON(!next);
5617                 put_prev_task(rq, next);
5618 
5619                 /*
5620                  * Rules for changing task_struct::cpus_allowed are holding
5621                  * both pi_lock and rq->lock, such that holding either
5622                  * stabilizes the mask.
5623                  *
5624                  * Drop rq->lock is not quite as disastrous as it usually is
5625                  * because !cpu_active at this point, which means load-balance
5626                  * will not interfere. Also, stop-machine.
5627                  */
5628                 rq_unlock(rq, rf);
5629                 raw_spin_lock(&next->pi_lock);
5630                 rq_relock(rq, rf);
5631 
5632                 /*
5633                  * Since we're inside stop-machine, _nothing_ should have
5634                  * changed the task, WARN if weird stuff happened, because in
5635                  * that case the above rq->lock drop is a fail too.
5636                  */
5637                 if (WARN_ON(task_rq(next) != rq || !task_on_rq_queued(next))) {
5638                         raw_spin_unlock(&next->pi_lock);
5639                         continue;
5640                 }
5641 
5642                 /* Find suitable destination for @next, with force if needed. */
5643                 dest_cpu = select_fallback_rq(dead_rq->cpu, next);
5644                 rq = __migrate_task(rq, rf, next, dest_cpu);
5645                 if (rq != dead_rq) {
5646                         rq_unlock(rq, rf);
5647                         rq = dead_rq;
5648                         *rf = orf;
5649                         rq_relock(rq, rf);
5650                 }
5651                 raw_spin_unlock(&next->pi_lock);
5652         }
5653 
5654         rq->stop = stop;
5655 }
5656 #endif /* CONFIG_HOTPLUG_CPU */
5657 
5658 void set_rq_online(struct rq *rq)
5659 {
5660         if (!rq->online) {
5661                 const struct sched_class *class;
5662 
5663                 cpumask_set_cpu(rq->cpu, rq->rd->online);
5664                 rq->online = 1;
5665 
5666                 for_each_class(class) {
5667                         if (class->rq_online)
5668                                 class->rq_online(rq);
5669                 }
5670         }
5671 }
5672 
5673 void set_rq_offline(struct rq *rq)
5674 {
5675         if (rq->online) {
5676                 const struct sched_class *class;
5677 
5678                 for_each_class(class) {
5679                         if (class->rq_offline)
5680                                 class->rq_offline(rq);
5681                 }
5682 
5683                 cpumask_clear_cpu(rq->cpu, rq->rd->online);
5684                 rq->online = 0;
5685         }
5686 }
5687 
5688 /*
5689  * used to mark begin/end of suspend/resume:
5690  */
5691 static int num_cpus_frozen;
5692 
5693 /*
5694  * Update cpusets according to cpu_active mask.  If cpusets are
5695  * disabled, cpuset_update_active_cpus() becomes a simple wrapper
5696  * around partition_sched_domains().
5697  *
5698  * If we come here as part of a suspend/resume, don't touch cpusets because we
5699  * want to restore it back to its original state upon resume anyway.
5700  */
5701 static void cpuset_cpu_active(void)
5702 {
5703         if (cpuhp_tasks_frozen) {
5704                 /*
5705                  * num_cpus_frozen tracks how many CPUs are involved in suspend
5706                  * resume sequence. As long as this is not the last online
5707                  * operation in the resume sequence, just build a single sched
5708                  * domain, ignoring cpusets.
5709                  */
5710                 partition_sched_domains(1, NULL, NULL);
5711                 if (--num_cpus_frozen)
5712                         return;
5713                 /*
5714                  * This is the last CPU online operation. So fall through and
5715                  * restore the original sched domains by considering the
5716                  * cpuset configurations.
5717                  */
5718                 cpuset_force_rebuild();
5719         }
5720         cpuset_update_active_cpus();
5721 }
5722 
5723 static int cpuset_cpu_inactive(unsigned int cpu)
5724 {
5725         if (!cpuhp_tasks_frozen) {
5726                 if (dl_cpu_busy(cpu))
5727                         return -EBUSY;
5728                 cpuset_update_active_cpus();
5729         } else {
5730                 num_cpus_frozen++;
5731                 partition_sched_domains(1, NULL, NULL);
5732         }
5733         return 0;
5734 }
5735 
5736 int sched_cpu_activate(unsigned int cpu)
5737 {
5738         struct rq *rq = cpu_rq(cpu);
5739         struct rq_flags rf;
5740 
5741 #ifdef CONFIG_SCHED_SMT
5742         /*
5743          * When going up, increment the number of cores with SMT present.
5744          */
5745         if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
5746                 static_branch_inc_cpuslocked(&sched_smt_present);
5747 #endif
5748         set_cpu_active(cpu, true);
5749 
5750         if (sched_smp_initialized) {
5751                 sched_domains_numa_masks_set(cpu);
5752                 cpuset_cpu_active();
5753         }
5754 
5755         /*
5756          * Put the rq online, if not already. This happens:
5757          *
5758          * 1) In the early boot process, because we build the real domains
5759          *    after all CPUs have been brought up.
5760          *
5761          * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
5762          *    domains.
5763          */
5764         rq_lock_irqsave(rq, &rf);
5765         if (rq->rd) {
5766                 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
5767                 set_rq_online(rq);
5768         }
5769         rq_unlock_irqrestore(rq, &rf);
5770 
5771         update_max_interval();
5772 
5773         return 0;
5774 }
5775 
5776 int sched_cpu_deactivate(unsigned int cpu)
5777 {
5778         int ret;
5779 
5780         set_cpu_active(cpu, false);
5781         /*
5782          * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU
5783          * users of this state to go away such that all new such users will
5784          * observe it.
5785          *
5786          * Do sync before park smpboot threads to take care the rcu boost case.
5787          */
5788         synchronize_rcu_mult(call_rcu, call_rcu_sched);
5789 
5790 #ifdef CONFIG_SCHED_SMT
5791         /*
5792          * When going down, decrement the number of cores with SMT present.
5793          */
5794         if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
5795                 static_branch_dec_cpuslocked(&sched_smt_present);
5796 #endif
5797 
5798         if (!sched_smp_initialized)
5799                 return 0;
5800 
5801         ret = cpuset_cpu_inactive(cpu);
5802         if (ret) {
5803                 set_cpu_active(cpu, true);
5804                 return ret;
5805         }
5806         sched_domains_numa_masks_clear(cpu);
5807         return 0;
5808 }
5809 
5810 static void sched_rq_cpu_starting(unsigned int cpu)
5811 {
5812         struct rq *rq = cpu_rq(cpu);
5813 
5814         rq->calc_load_update = calc_load_update;
5815         update_max_interval();
5816 }
5817 
5818 int sched_cpu_starting(unsigned int cpu)
5819 {
5820         sched_rq_cpu_starting(cpu);
5821         sched_tick_start(cpu);
5822         return 0;
5823 }
5824 
5825 #ifdef CONFIG_HOTPLUG_CPU
5826 int sched_cpu_dying(unsigned int cpu)
5827 {
5828         struct rq *rq = cpu_rq(cpu);
5829         struct rq_flags rf;
5830 
5831         /* Handle pending wakeups and then migrate everything off */
5832         sched_ttwu_pending();
5833         sched_tick_stop(cpu);
5834 
5835         rq_lock_irqsave(rq, &rf);
5836         if (rq->rd) {
5837                 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
5838                 set_rq_offline(rq);
5839         }
5840         migrate_tasks(rq, &rf);
5841         BUG_ON(rq->nr_running != 1);
5842         rq_unlock_irqrestore(rq, &rf);
5843 
5844         calc_load_migrate(rq);
5845         update_max_interval();
5846         nohz_balance_exit_idle(rq);
5847         hrtick_clear(rq);
5848         return 0;
5849 }
5850 #endif
5851 
5852 void __init sched_init_smp(void)
5853 {
5854         sched_init_numa();
5855 
5856         /*
5857          * There's no userspace yet to cause hotplug operations; hence all the
5858          * CPU masks are stable and all blatant races in the below code cannot
5859          * happen. The hotplug lock is nevertheless taken to satisfy lockdep,
5860          * but there won't be any contention on it.
5861          */
5862         cpus_read_lock();
5863         mutex_lock(&sched_domains_mutex);
5864         sched_init_domains(cpu_active_mask);
5865         mutex_unlock(&sched_domains_mutex);
5866         cpus_read_unlock();
5867 
5868         /* Move init over to a non-isolated CPU */
5869         if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_FLAG_DOMAIN)) < 0)
5870                 BUG();
5871         sched_init_granularity();
5872 
5873         init_sched_rt_class();
5874         init_sched_dl_class();
5875 
5876         sched_smp_initialized = true;
5877 }
5878 
5879 static int __init migration_init(void)
5880 {
5881         sched_rq_cpu_starting(smp_processor_id());
5882         return 0;
5883 }
5884 early_initcall(migration_init);
5885 
5886 #else
5887 void __init sched_init_smp(void)
5888 {
5889         sched_init_granularity();
5890 }
5891 #endif /* CONFIG_SMP */
5892 
5893 int in_sched_functions(unsigned long addr)
5894 {
5895         return in_lock_functions(addr) ||
5896                 (addr >= (unsigned long)__sched_text_start
5897                 && addr < (unsigned long)__sched_text_end);
5898 }
5899 
5900 #ifdef CONFIG_CGROUP_SCHED
5901 /*
5902  * Default task group.
5903  * Every task in system belongs to this group at bootup.
5904  */
5905 struct task_group root_task_group;
5906 LIST_HEAD(task_groups);
5907 
5908 /* Cacheline aligned slab cache for task_group */
5909 static struct kmem_cache *task_group_cache __read_mostly;
5910 #endif
5911 
5912 DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
5913 DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
5914 
5915 void __init sched_init(void)
5916 {
5917         int i, j;
5918         unsigned long alloc_size = 0, ptr;
5919 
5920         wait_bit_init();
5921 
5922 #ifdef CONFIG_FAIR_GROUP_SCHED
5923         alloc_size += 2 * nr_cpu_ids * sizeof(void **);
5924 #endif
5925 #ifdef CONFIG_RT_GROUP_SCHED
5926         alloc_size += 2 * nr_cpu_ids * sizeof(void **);
5927 #endif
5928         if (alloc_size) {
5929                 ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT);
5930 
5931 #ifdef CONFIG_FAIR_GROUP_SCHED
5932                 root_task_group.se = (struct sched_entity **)ptr;
5933                 ptr += nr_cpu_ids * sizeof(void **);
5934 
5935                 root_task_group.cfs_rq = (struct cfs_rq **)ptr;
5936                 ptr += nr_cpu_ids * sizeof(void **);
5937 
5938 #endif /* CONFIG_FAIR_GROUP_SCHED */
5939 #ifdef CONFIG_RT_GROUP_SCHED
5940                 root_task_group.rt_se = (struct sched_rt_entity **)ptr;
5941                 ptr += nr_cpu_ids * sizeof(void **);
5942 
5943                 root_task_group.rt_rq = (struct rt_rq **)ptr;
5944                 ptr += nr_cpu_ids * sizeof(void **);
5945 
5946 #endif /* CONFIG_RT_GROUP_SCHED */
5947         }
5948 #ifdef CONFIG_CPUMASK_OFFSTACK
5949         for_each_possible_cpu(i) {
5950                 per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
5951                         cpumask_size(), GFP_KERNEL, cpu_to_node(i));
5952                 per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
5953                         cpumask_size(), GFP_KERNEL, cpu_to_node(i));
5954         }
5955 #endif /* CONFIG_CPUMASK_OFFSTACK */
5956 
5957         init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());
5958         init_dl_bandwidth(&def_dl_bandwidth, global_rt_period(), global_rt_runtime());
5959 
5960 #ifdef CONFIG_SMP
5961         init_defrootdomain();
5962 #endif
5963 
5964 #ifdef CONFIG_RT_GROUP_SCHED
5965         init_rt_bandwidth(&root_task_group.rt_bandwidth,
5966                         global_rt_period(), global_rt_runtime());
5967 #endif /* CONFIG_RT_GROUP_SCHED */
5968 
5969 #ifdef CONFIG_CGROUP_SCHED
5970         task_group_cache = KMEM_CACHE(task_group, 0);
5971 
5972         list_add(&root_task_group.list, &task_groups);
5973         INIT_LIST_HEAD(&root_task_group.children);
5974         INIT_LIST_HEAD(&root_task_group.siblings);
5975         autogroup_init(&init_task);
5976 #endif /* CONFIG_CGROUP_SCHED */
5977 
5978         for_each_possible_cpu(i) {
5979                 struct rq *rq;
5980 
5981                 rq = cpu_rq(i);
5982                 raw_spin_lock_init(&rq->lock);
5983                 rq->nr_running = 0;
5984                 rq->calc_load_active = 0;
5985                 rq->calc_load_update = jiffies + LOAD_FREQ;
5986                 init_cfs_rq(&rq->cfs);
5987                 init_rt_rq(&rq->rt);
5988                 init_dl_rq(&rq->dl);
5989 #ifdef CONFIG_FAIR_GROUP_SCHED
5990                 root_task_group.shares = ROOT_TASK_GROUP_LOAD;
5991                 INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
5992                 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
5993                 /*
5994                  * How much CPU bandwidth does root_task_group get?
5995                  *
5996                  * In case of task-groups formed thr' the cgroup filesystem, it
5997                  * gets 100% of the CPU resources in the system. This overall
5998                  * system CPU resource is divided among the tasks of
5999                  * root_task_group and its child task-groups in a fair manner,
6000                  * based on each entity's (task or task-group's) weight
6001                  * (se->load.weight).
6002                  *
6003                  * In other words, if root_task_group has 10 tasks of weight
6004                  * 1024) and two child groups A0 and A1 (of weight 1024 each),
6005                  * then A0's share of the CPU resource is:
6006                  *
6007                  *      A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
6008                  *
6009                  * We achieve this by letting root_task_group's tasks sit
6010                  * directly in rq->cfs (i.e root_task_group->se[] = NULL).
6011                  */
6012                 init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
6013                 init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
6014 #endif /* CONFIG_FAIR_GROUP_SCHED */
6015 
6016                 rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
6017 #ifdef CONFIG_RT_GROUP_SCHED
6018                 init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
6019 #endif
6020 
6021                 for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
6022                         rq->cpu_load[j] = 0;
6023 
6024 #ifdef CONFIG_SMP
6025                 rq->sd = NULL;
6026                 rq->rd = NULL;
6027                 rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE;
6028                 rq->balance_callback = NULL;
6029                 rq->active_balance = 0;
6030                 rq->next_balance = jiffies;
6031                 rq->push_cpu = 0;
6032                 rq->cpu = i;
6033                 rq->online = 0;
6034                 rq->idle_stamp = 0;
6035                 rq->avg_idle = 2*sysctl_sched_migration_cost;
6036                 rq->max_idle_balance_cost = sysctl_sched_migration_cost;
6037 
6038                 INIT_LIST_HEAD(&rq->cfs_tasks);
6039 
6040                 rq_attach_root(rq, &def_root_domain);
6041 #ifdef CONFIG_NO_HZ_COMMON
6042                 rq->last_load_update_tick = jiffies;
6043                 rq->last_blocked_load_update_tick = jiffies;
6044                 atomic_set(&rq->nohz_flags, 0);
6045 #endif
6046 #endif /* CONFIG_SMP */
6047                 hrtick_rq_init(rq);
6048                 atomic_set(&rq->nr_iowait, 0);
6049         }
6050 
6051         set_load_weight(&init_task, false);
6052 
6053         /*
6054          * The boot idle thread does lazy MMU switching as well:
6055          */
6056         mmgrab(&init_mm);
6057         enter_lazy_tlb(&init_mm, current);
6058 
6059         /*
6060          * Make us the idle thread. Technically, schedule() should not be
6061          * called from this thread, however somewhere below it might be,
6062          * but because we are the idle thread, we just pick up running again
6063          * when this runqueue becomes "idle".
6064          */
6065         init_idle(current, smp_processor_id());
6066 
6067         calc_load_update = jiffies + LOAD_FREQ;
6068 
6069 #ifdef CONFIG_SMP
6070         idle_thread_set_boot_cpu();
6071 #endif
6072         init_sched_fair_class();
6073 
6074         init_schedstats();
6075 
6076         psi_init();
6077 
6078         scheduler_running = 1;
6079 }
6080 
6081 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
6082 static inline int preempt_count_equals(int preempt_offset)
6083 {
6084         int nested = preempt_count() + rcu_preempt_depth();
6085 
6086         return (nested == preempt_offset);
6087 }
6088 
6089 void __might_sleep(const char *file, int line, int preempt_offset)
6090 {
6091         /*
6092          * Blocking primitives will set (and therefore destroy) current->state,
6093          * since we will exit with TASK_RUNNING make sure we enter with it,
6094          * otherwise we will destroy state.
6095          */
6096         WARN_ONCE(current->state != TASK_RUNNING && current->task_state_change,
6097                         "do not call blocking ops when !TASK_RUNNING; "
6098                         "state=%lx set at [<%p>] %pS\n",
6099                         current->state,
6100                         (void *)current->task_state_change,
6101                         (void *)current->task_state_change);
6102 
6103         ___might_sleep(file, line, preempt_offset);
6104 }
6105 EXPORT_SYMBOL(__might_sleep);
6106 
6107 void ___might_sleep(const char *file, int line, int preempt_offset)
6108 {
6109         /* Ratelimiting timestamp: */
6110         static unsigned long prev_jiffy;
6111 
6112         unsigned long preempt_disable_ip;
6113 
6114         /* WARN_ON_ONCE() by default, no rate limit required: */
6115         rcu_sleep_check();
6116 
6117         if ((preempt_count_equals(preempt_offset) && !irqs_disabled() &&
6118              !is_idle_task(current)) ||
6119             system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING ||
6120             oops_in_progress)
6121                 return;
6122 
6123         if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
6124                 return;
6125         prev_jiffy = jiffies;
6126 
6127         /* Save this before calling printk(), since that will clobber it: */
6128         preempt_disable_ip = get_preempt_disable_ip(current);
6129 
6130         printk(KERN_ERR
6131                 "BUG: sleeping function called from invalid context at %s:%d\n",
6132                         file, line);
6133         printk(KERN_ERR
6134                 "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
6135                         in_atomic(), irqs_disabled(),
6136                         current->pid, current->comm);
6137 
6138         if (task_stack_end_corrupted(current))
6139                 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
6140 
6141         debug_show_held_locks(current);
6142         if (irqs_disabled())
6143                 print_irqtrace_events(current);
6144         if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
6145             && !preempt_count_equals(preempt_offset)) {
6146                 pr_err("Preemption disabled at:");
6147                 print_ip_sym(preempt_disable_ip);
6148                 pr_cont("\n");
6149         }
6150         dump_stack();
6151         add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
6152 }
6153 EXPORT_SYMBOL(___might_sleep);
6154 #endif
6155 
6156 #ifdef CONFIG_MAGIC_SYSRQ
6157 void normalize_rt_tasks(void)
6158 {
6159         struct task_struct *g, *p;
6160         struct sched_attr attr = {
6161                 .sched_policy = SCHED_NORMAL,
6162         };
6163 
6164         read_lock(&tasklist_lock);
6165         for_each_process_thread(g, p) {
6166                 /*
6167                  * Only normalize user tasks:
6168                  */
6169                 if (p->flags & PF_KTHREAD)
6170                         continue;
6171 
6172                 p->se.exec_start = 0;
6173                 schedstat_set(p->se.statistics.wait_start,  0);
6174                 schedstat_set(p->se.statistics.sleep_start, 0);
6175                 schedstat_set(p->se.statistics.block_start, 0);
6176 
6177                 if (!dl_task(p) && !rt_task(p)) {
6178                         /*
6179                          * Renice negative nice level userspace
6180                          * tasks back to 0:
6181                          */
6182                         if (task_nice(p) < 0)
6183                                 set_user_nice(p, 0);
6184                         continue;
6185                 }
6186 
6187                 __sched_setscheduler(p, &attr, false, false);
6188         }
6189         read_unlock(&tasklist_lock);
6190 }
6191 
6192 #endif /* CONFIG_MAGIC_SYSRQ */
6193 
6194 #if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
6195 /*
6196  * These functions are only useful for the IA64 MCA handling, or kdb.
6197  *
6198  * They can only be called when the whole system has been
6199  * stopped - every CPU needs to be quiescent, and no scheduling
6200  * activity can take place. Using them for anything else would
6201  * be a serious bug, and as a result, they aren't even visible
6202  * under any other configuration.
6203  */
6204 
6205 /**
6206  * curr_task - return the current task for a given CPU.
6207  * @cpu: the processor in question.
6208  *
6209  * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
6210  *
6211  * Return: The current task for @cpu.
6212  */
6213 struct task_struct *curr_task(int cpu)
6214 {
6215         return cpu_curr(cpu);
6216 }
6217 
6218 #endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
6219 
6220 #ifdef CONFIG_IA64
6221 /**
6222  * set_curr_task - set the current task for a given CPU.
6223  * @cpu: the processor in question.
6224  * @p: the task pointer to set.
6225  *
6226  * Description: This function must only be used when non-maskable interrupts
6227  * are serviced on a separate stack. It allows the architecture to switch the
6228  * notion of the current task on a CPU in a non-blocking manner. This function
6229  * must be called with all CPU's synchronized, and interrupts disabled, the
6230  * and caller must save the original value of the current task (see
6231  * curr_task() above) and restore that value before reenabling interrupts and
6232  * re-starting the system.
6233  *
6234  * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
6235  */
6236 void ia64_set_curr_task(int cpu, struct task_struct *p)
6237 {
6238         cpu_curr(cpu) = p;
6239 }
6240 
6241 #endif
6242 
6243 #ifdef CONFIG_CGROUP_SCHED
6244 /* task_group_lock serializes the addition/removal of task groups */
6245 static DEFINE_SPINLOCK(task_group_lock);
6246 
6247 static void sched_free_group(struct task_group *tg)
6248 {
6249         free_fair_sched_group(tg);
6250         free_rt_sched_group(tg);
6251         autogroup_free(tg);
6252         kmem_cache_free(task_group_cache, tg);
6253 }
6254 
6255 /* allocate runqueue etc for a new task group */
6256 struct task_group *sched_create_group(struct task_group *parent)
6257 {
6258         struct task_group *tg;
6259 
6260         tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO);
6261         if (!tg)
6262                 return ERR_PTR(-ENOMEM);
6263 
6264         if (!alloc_fair_sched_group(tg, parent))
6265                 goto err;
6266 
6267         if (!alloc_rt_sched_group(tg, parent))
6268                 goto err;
6269 
6270         return tg;
6271 
6272 err:
6273         sched_free_group(tg);
6274         return ERR_PTR(-ENOMEM);
6275 }
6276 
6277 void sched_online_group(struct task_group *tg, struct task_group *parent)
6278 {
6279         unsigned long flags;
6280 
6281         spin_lock_irqsave(&task_group_lock, flags);
6282         list_add_rcu(&tg->list, &task_groups);
6283 
6284         /* Root should already exist: */
6285         WARN_ON(!parent);
6286 
6287         tg->parent = parent;
6288         INIT_LIST_HEAD(&tg->children);
6289         list_add_rcu(&tg->siblings, &parent->children);
6290         spin_unlock_irqrestore(&task_group_lock, flags);
6291 
6292         online_fair_sched_group(tg);
6293 }
6294 
6295 /* rcu callback to free various structures associated with a task group */
6296 static void sched_free_group_rcu(struct rcu_head *rhp)
6297 {
6298         /* Now it should be safe to free those cfs_rqs: */
6299         sched_free_group(container_of(rhp, struct task_group, rcu));
6300 }
6301 
6302 void sched_destroy_group(struct task_group *tg)
6303 {
6304         /* Wait for possible concurrent references to cfs_rqs complete: */
6305         call_rcu(&tg->rcu, sched_free_group_rcu);
6306 }
6307 
6308 void sched_offline_group(struct task_group *tg)
6309 {
6310         unsigned long flags;
6311 
6312         /* End participation in shares distribution: */
6313         unregister_fair_sched_group(tg);
6314 
6315         spin_lock_irqsave(&task_group_lock, flags);
6316         list_del_rcu(&tg->list);
6317         list_del_rcu(&tg->siblings);
6318         spin_unlock_irqrestore(&task_group_lock, flags);
6319 }
6320 
6321 static void sched_change_group(struct task_struct *tsk, int type)
6322 {
6323         struct task_group *tg;
6324 
6325         /*
6326          * All callers are synchronized by task_rq_lock(); we do not use RCU
6327          * which is pointless here. Thus, we pass "true" to task_css_check()
6328          * to prevent lockdep warnings.
6329          */
6330         tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
6331                           struct task_group, css);
6332         tg = autogroup_task_group(tsk, tg);
6333         tsk->sched_task_group = tg;
6334 
6335 #ifdef CONFIG_FAIR_GROUP_SCHED
6336         if (tsk->sched_class->task_change_group)
6337                 tsk->sched_class->task_change_group(tsk, type);
6338         else
6339 #endif
6340                 set_task_rq(tsk, task_cpu(tsk));
6341 }
6342 
6343 /*
6344  * Change task's runqueue when it moves between groups.
6345  *
6346  * The caller of this function should have put the task in its new group by
6347  * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect
6348  * its new group.
6349  */
6350 void sched_move_task(struct task_struct *tsk)
6351 {
6352         int queued, running, queue_flags =
6353                 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
6354         struct rq_flags rf;
6355         struct rq *rq;
6356 
6357         rq = task_rq_lock(tsk, &rf);
6358         update_rq_clock(rq);
6359 
6360         running = task_current(rq, tsk);
6361         queued = task_on_rq_queued(tsk);
6362 
6363         if (queued)
6364                 dequeue_task(rq, tsk, queue_flags);
6365         if (running)
6366                 put_prev_task(rq, tsk);
6367 
6368         sched_change_group(tsk, TASK_MOVE_GROUP);
6369 
6370         if (queued)
6371                 enqueue_task(rq, tsk, queue_flags);
6372         if (running)
6373                 set_curr_task(rq, tsk);
6374 
6375         task_rq_unlock(rq, tsk, &rf);
6376 }
6377 
6378 static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
6379 {
6380         return css ? container_of(css, struct task_group, css) : NULL;
6381 }
6382 
6383 static struct cgroup_subsys_state *
6384 cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
6385 {
6386         struct task_group *parent = css_tg(parent_css);
6387         struct task_group *tg;
6388 
6389         if (!parent) {
6390                 /* This is early initialization for the top cgroup */
6391                 return &root_task_group.css;
6392         }
6393 
6394         tg = sched_create_group(parent);
6395         if (IS_ERR(tg))
6396                 return ERR_PTR(-ENOMEM);
6397 
6398         return &tg->css;
6399 }
6400 
6401 /* Expose task group only after completing cgroup initialization */
6402 static int cpu_cgroup_css_online(struct cgroup_subsys_state *css)
6403 {
6404         struct task_group *tg = css_tg(css);
6405         struct task_group *parent = css_tg(css->parent);
6406 
6407         if (parent)
6408                 sched_online_group(tg, parent);
6409         return 0;
6410 }
6411 
6412 static void cpu_cgroup_css_released(struct cgroup_subsys_state *css)
6413 {
6414         struct task_group *tg = css_tg(css);
6415 
6416         sched_offline_group(tg);
6417 }
6418 
6419 static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
6420 {
6421         struct task_group *tg = css_tg(css);
6422 
6423         /*
6424          * Relies on the RCU grace period between css_released() and this.
6425          */
6426         sched_free_group(tg);
6427 }
6428 
6429 /*
6430  * This is called before wake_up_new_task(), therefore we really only
6431  * have to set its group bits, all the other stuff does not apply.
6432  */
6433 static void cpu_cgroup_fork(struct task_struct *task)
6434 {
6435         struct rq_flags rf;
6436         struct rq *rq;
6437 
6438         rq = task_rq_lock(task, &rf);
6439 
6440         update_rq_clock(rq);
6441         sched_change_group(task, TASK_SET_GROUP);
6442 
6443         task_rq_unlock(rq, task, &rf);
6444 }
6445 
6446 static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
6447 {
6448         struct task_struct *task;
6449         struct cgroup_subsys_state *css;
6450         int ret = 0;
6451 
6452         cgroup_taskset_for_each(task, css, tset) {
6453 #ifdef CONFIG_RT_GROUP_SCHED
6454                 if (!sched_rt_can_attach(css_tg(css), task))
6455                         return -EINVAL;
6456 #else
6457                 /* We don't support RT-tasks being in separate groups */
6458                 if (task->sched_class != &fair_sched_class)
6459                         return -EINVAL;
6460 #endif
6461                 /*
6462                  * Serialize against wake_up_new_task() such that if its
6463                  * running, we're sure to observe its full state.
6464                  */
6465                 raw_spin_lock_irq(&task->pi_lock);
6466                 /*
6467                  * Avoid calling sched_move_task() before wake_up_new_task()
6468                  * has happened. This would lead to problems with PELT, due to
6469                  * move wanting to detach+attach while we're not attached yet.
6470                  */
6471                 if (task->state == TASK_NEW)
6472                         ret = -EINVAL;
6473                 raw_spin_unlock_irq(&task->pi_lock);
6474 
6475                 if (ret)
6476                         break;
6477         }
6478         return ret;
6479 }
6480 
6481 static void cpu_cgroup_attach(struct cgroup_taskset *tset)
6482 {
6483         struct task_struct *task;
6484         struct cgroup_subsys_state *css;
6485 
6486         cgroup_taskset_for_each(task, css, tset)
6487                 sched_move_task(task);
6488 }
6489 
6490 #ifdef CONFIG_FAIR_GROUP_SCHED
6491 static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
6492                                 struct cftype *cftype, u64 shareval)
6493 {
6494         return sched_group_set_shares(css_tg(css), scale_load(shareval));
6495 }
6496 
6497 static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css,
6498                                struct cftype *cft)
6499 {
6500         struct task_group *tg = css_tg(css);
6501 
6502         return (u64) scale_load_down(tg->shares);
6503 }
6504 
6505 #ifdef CONFIG_CFS_BANDWIDTH
6506 static DEFINE_MUTEX(cfs_constraints_mutex);
6507 
6508 const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
6509 const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
6510 
6511 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
6512 
6513 static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
6514 {
6515         int i, ret = 0, runtime_enabled, runtime_was_enabled;
6516         struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
6517 
6518         if (tg == &root_task_group)
6519                 return -EINVAL;
6520 
6521         /*
6522          * Ensure we have at some amount of bandwidth every period.  This is
6523          * to prevent reaching a state of large arrears when throttled via
6524          * entity_tick() resulting in prolonged exit starvation.
6525          */
6526         if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
6527                 return -EINVAL;
6528 
6529         /*
6530          * Likewise, bound things on the otherside by preventing insane quota
6531          * periods.  This also allows us to normalize in computing quota
6532          * feasibility.
6533          */
6534         if (period > max_cfs_quota_period)
6535                 return -EINVAL;
6536 
6537         /*
6538          * Prevent race between setting of cfs_rq->runtime_enabled and
6539          * unthrottle_offline_cfs_rqs().
6540          */
6541         get_online_cpus();
6542         mutex_lock(&cfs_constraints_mutex);
6543         ret = __cfs_schedulable(tg, period, quota);
6544         if (ret)
6545                 goto out_unlock;
6546 
6547         runtime_enabled = quota != RUNTIME_INF;
6548         runtime_was_enabled = cfs_b->quota != RUNTIME_INF;
6549         /*
6550          * If we need to toggle cfs_bandwidth_used, off->on must occur
6551          * before making related changes, and on->off must occur afterwards
6552          */
6553         if (runtime_enabled && !runtime_was_enabled)
6554                 cfs_bandwidth_usage_inc();
6555         raw_spin_lock_irq(&cfs_b->lock);
6556         cfs_b->period = ns_to_ktime(period);
6557         cfs_b->quota = quota;
6558 
6559         __refill_cfs_bandwidth_runtime(cfs_b);
6560 
6561         /* Restart the period timer (if active) to handle new period expiry: */
6562         if (runtime_enabled)
6563                 start_cfs_bandwidth(cfs_b);
6564 
6565         raw_spin_unlock_irq(&cfs_b->lock);
6566 
6567         for_each_online_cpu(i) {
6568                 struct cfs_rq *cfs_rq = tg->cfs_rq[i];
6569                 struct rq *rq = cfs_rq->rq;
6570                 struct rq_flags rf;
6571 
6572                 rq_lock_irq(rq, &rf);
6573                 cfs_rq->runtime_enabled = runtime_enabled;
6574                 cfs_rq->runtime_remaining = 0;
6575 
6576                 if (cfs_rq->throttled)
6577                         unthrottle_cfs_rq(cfs_rq);
6578                 rq_unlock_irq(rq, &rf);
6579         }
6580         if (runtime_was_enabled && !runtime_enabled)
6581                 cfs_bandwidth_usage_dec();
6582 out_unlock:
6583         mutex_unlock(&cfs_constraints_mutex);
6584         put_online_cpus();
6585 
6586         return ret;
6587 }
6588 
6589 int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
6590 {
6591         u64 quota, period;
6592 
6593         period = ktime_to_ns(tg->cfs_bandwidth.period);
6594         if (cfs_quota_us < 0)
6595                 quota = RUNTIME_INF;
6596         else
6597                 quota = (u64)cfs_quota_us * NSEC_PER_USEC;
6598 
6599         return tg_set_cfs_bandwidth(tg, period, quota);
6600 }
6601 
6602 long tg_get_cfs_quota(struct task_group *tg)
6603 {
6604         u64 quota_us;
6605 
6606         if (tg->cfs_bandwidth.quota == RUNTIME_INF)
6607                 return -1;
6608 
6609         quota_us = tg->cfs_bandwidth.quota;
6610         do_div(quota_us, NSEC_PER_USEC);
6611 
6612         return quota_us;
6613 }
6614 
6615 int tg_set_cfs_period(struct task_group *tg, long cfs_period_us)
6616 {
6617         u64 quota, period;
6618 
6619         period = (u64)cfs_period_us * NSEC_PER_USEC;
6620         quota = tg->cfs_bandwidth.quota;
6621 
6622         return tg_set_cfs_bandwidth(tg, period, quota);
6623 }
6624 
6625 long tg_get_cfs_period(struct task_group *tg)
6626 {
6627         u64 cfs_period_us;
6628 
6629         cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period);
6630         do_div(cfs_period_us, NSEC_PER_USEC);
6631 
6632         return cfs_period_us;
6633 }
6634 
6635 static s64 cpu_cfs_quota_read_s64(struct cgroup_subsys_state *css,
6636                                   struct cftype *cft)
6637 {
6638         return tg_get_cfs_quota(css_tg(css));
6639 }
6640 
6641 static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state *css,
6642                                    struct cftype *cftype, s64 cfs_quota_us)
6643 {
6644         return tg_set_cfs_quota(css_tg(css), cfs_quota_us);
6645 }
6646 
6647 static u64 cpu_cfs_period_read_u64(struct cgroup_subsys_state *css,
6648                                    struct cftype *cft)
6649 {
6650         return tg_get_cfs_period(css_tg(css));
6651 }
6652 
6653 static int cpu_cfs_period_write_u64(struct cgroup_subsys_state *css,
6654                                     struct cftype *cftype, u64 cfs_period_us)
6655 {
6656         return tg_set_cfs_period(css_tg(css), cfs_period_us);
6657 }
6658 
6659 struct cfs_schedulable_data {
6660         struct task_group *tg;
6661         u64 period, quota;
6662 };
6663 
6664 /*
6665  * normalize group quota/period to be quota/max_period
6666  * note: units are usecs
6667  */
6668 static u64 normalize_cfs_quota(struct task_group *tg,
6669                                struct cfs_schedulable_data *d)
6670 {
6671         u64 quota, period;
6672 
6673         if (tg == d->tg) {
6674                 period = d->period;
6675                 quota = d->quota;
6676         } else {
6677                 period = tg_get_cfs_period(tg);
6678                 quota = tg_get_cfs_quota(tg);
6679         }
6680 
6681         /* note: these should typically be equivalent */
6682         if (quota == RUNTIME_INF || quota == -1)
6683                 return RUNTIME_INF;
6684 
6685         return to_ratio(period, quota);
6686 }
6687 
6688 static int tg_cfs_schedulable_down(struct task_group *tg, void *data)
6689 {
6690         struct cfs_schedulable_data *d = data;
6691         struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
6692         s64 quota = 0, parent_quota = -1;
6693 
6694         if (!tg->parent) {
6695                 quota = RUNTIME_INF;
6696         } else {
6697                 struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth;
6698 
6699                 quota = normalize_cfs_quota(tg, d);
6700                 parent_quota = parent_b->hierarchical_quota;
6701 
6702                 /*
6703                  * Ensure max(child_quota) <= parent_quota.  On cgroup2,
6704                  * always take the min.  On cgroup1, only inherit when no
6705                  * limit is set:
6706                  */
6707                 if (cgroup_subsys_on_dfl(cpu_cgrp_subsys)) {
6708                         quota = min(quota, parent_quota);
6709                 } else {
6710                         if (quota == RUNTIME_INF)
6711                                 quota = parent_quota;
6712                         else if (parent_quota != RUNTIME_INF && quota > parent_quota)
6713                                 return -EINVAL;
6714                 }
6715         }
6716         cfs_b->hierarchical_quota = quota;
6717 
6718         return 0;
6719 }
6720 
6721 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
6722 {
6723         int ret;
6724         struct cfs_schedulable_data data = {
6725                 .tg = tg,
6726                 .period = period,
6727                 .quota = quota,
6728         };
6729 
6730         if (quota != RUNTIME_INF) {
6731                 do_div(data.period, NSEC_PER_USEC);
6732                 do_div(data.quota, NSEC_PER_USEC);
6733         }
6734 
6735         rcu_read_lock();
6736         ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
6737         rcu_read_unlock();
6738 
6739         return ret;
6740 }
6741 
6742 static int cpu_cfs_stat_show(struct seq_file *sf, void *v)
6743 {
6744         struct task_group *tg = css_tg(seq_css(sf));
6745         struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
6746 
6747         seq_printf(sf, "nr_periods %d\n", cfs_b->nr_periods);
6748         seq_printf(sf, "nr_throttled %d\n", cfs_b->nr_throttled);
6749         seq_printf(sf, "throttled_time %llu\n", cfs_b->throttled_time);
6750 
6751         if (schedstat_enabled() && tg != &root_task_group) {
6752                 u64 ws = 0;
6753                 int i;
6754 
6755                 for_each_possible_cpu(i)
6756                         ws += schedstat_val(tg->se[i]->statistics.wait_sum);
6757 
6758                 seq_printf(sf, "wait_sum %llu\n", ws);
6759         }
6760 
6761         return 0;
6762 }
6763 #endif /* CONFIG_CFS_BANDWIDTH */
6764 #endif /* CONFIG_FAIR_GROUP_SCHED */
6765 
6766 #ifdef CONFIG_RT_GROUP_SCHED
6767 static int cpu_rt_runtime_write(struct cgroup_subsys_state *css,
6768                                 struct cftype *cft, s64 val)
6769 {
6770         return sched_group_set_rt_runtime(css_tg(css), val);
6771 }
6772 
6773 static s64 cpu_rt_runtime_read(struct cgroup_subsys_state *css,
6774                                struct cftype *cft)
6775 {
6776         return sched_group_rt_runtime(css_tg(css));
6777 }
6778 
6779 static int cpu_rt_period_write_uint(struct cgroup_subsys_state *css,
6780                                     struct cftype *cftype, u64 rt_period_us)
6781 {
6782         return sched_group_set_rt_period(css_tg(css), rt_period_us);
6783 }
6784 
6785 static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css,
6786                                    struct cftype *cft)
6787 {
6788         return sched_group_rt_period(css_tg(css));
6789 }
6790 #endif /* CONFIG_RT_GROUP_SCHED */
6791 
6792 static struct cftype cpu_legacy_files[] = {
6793 #ifdef CONFIG_FAIR_GROUP_SCHED
6794         {
6795                 .name = "shares",
6796                 .read_u64 = cpu_shares_read_u64,
6797                 .write_u64 = cpu_shares_write_u64,
6798         },
6799 #endif
6800 #ifdef CONFIG_CFS_BANDWIDTH
6801         {
6802                 .name = "cfs_quota_us",
6803                 .read_s64 = cpu_cfs_quota_read_s64,
6804                 .write_s64 = cpu_cfs_quota_write_s64,
6805         },
6806         {
6807                 .name = "cfs_period_us",
6808                 .read_u64 = cpu_cfs_period_read_u64,
6809                 .write_u64 = cpu_cfs_period_write_u64,
6810         },
6811         {
6812                 .name = "stat",
6813                 .seq_show = cpu_cfs_stat_show,
6814         },
6815 #endif
6816 #ifdef CONFIG_RT_GROUP_SCHED
6817         {
6818                 .name = "rt_runtime_us",
6819                 .read_s64 = cpu_rt_runtime_read,
6820                 .write_s64 = cpu_rt_runtime_write,
6821         },
6822         {
6823                 .name = "rt_period_us",
6824                 .read_u64 = cpu_rt_period_read_uint,
6825                 .write_u64 = cpu_rt_period_write_uint,
6826         },
6827 #endif
6828         { }     /* Terminate */
6829 };
6830 
6831 static int cpu_extra_stat_show(struct seq_file *sf,
6832                                struct cgroup_subsys_state *css)
6833 {
6834 #ifdef CONFIG_CFS_BANDWIDTH
6835         {
6836                 struct task_group *tg = css_tg(css);
6837                 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
6838                 u64 throttled_usec;
6839 
6840                 throttled_usec = cfs_b->throttled_time;
6841                 do_div(throttled_usec, NSEC_PER_USEC);
6842 
6843                 seq_printf(sf, "nr_periods %d\n"
6844                            "nr_throttled %d\n"
6845                            "throttled_usec %llu\n",
6846                            cfs_b->nr_periods, cfs_b->nr_throttled,
6847                            throttled_usec);
6848         }
6849 #endif
6850         return 0;
6851 }
6852 
6853 #ifdef CONFIG_FAIR_GROUP_SCHED
6854 static u64 cpu_weight_read_u64(struct cgroup_subsys_state *css,
6855                                struct cftype *cft)
6856 {
6857         struct task_group *tg = css_tg(css);
6858         u64 weight = scale_load_down(tg->shares);
6859 
6860         return DIV_ROUND_CLOSEST_ULL(weight * CGROUP_WEIGHT_DFL, 1024);
6861 }
6862 
6863 static int cpu_weight_write_u64(struct cgroup_subsys_state *css,
6864                                 struct cftype *cft, u64 weight)
6865 {
6866         /*
6867          * cgroup weight knobs should use the common MIN, DFL and MAX
6868          * values which are 1, 100 and 10000 respectively.  While it loses
6869          * a bit of range on both ends, it maps pretty well onto the shares
6870          * value used by scheduler and the round-trip conversions preserve
6871          * the original value over the entire range.
6872          */
6873         if (weight < CGROUP_WEIGHT_MIN || weight > CGROUP_WEIGHT_MAX)
6874                 return -ERANGE;
6875 
6876         weight = DIV_ROUND_CLOSEST_ULL(weight * 1024, CGROUP_WEIGHT_DFL);
6877 
6878         return sched_group_set_shares(css_tg(css), scale_load(weight));
6879 }
6880 
6881 static s64 cpu_weight_nice_read_s64(struct cgroup_subsys_state *css,
6882                                     struct cftype *cft)
6883 {
6884         unsigned long weight = scale_load_down(css_tg(css)->shares);
6885         int last_delta = INT_MAX;
6886         int prio, delta;
6887 
6888         /* find the closest nice value to the current weight */
6889         for (prio = 0; prio < ARRAY_SIZE(sched_prio_to_weight); prio++) {
6890                 delta = abs(sched_prio_to_weight[prio] - weight);
6891                 if (delta >= last_delta)
6892                         break;
6893                 last_delta = delta;
6894         }
6895 
6896         return PRIO_TO_NICE(prio - 1 + MAX_RT_PRIO);
6897 }
6898 
6899 static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css,
6900                                      struct cftype *cft, s64 nice)
6901 {
6902         unsigned long weight;
6903         int idx;
6904 
6905         if (nice < MIN_NICE || nice > MAX_NICE)
6906                 return -ERANGE;
6907 
6908         idx = NICE_TO_PRIO(nice) - MAX_RT_PRIO;
6909         idx = array_index_nospec(idx, 40);
6910         weight = sched_prio_to_weight[idx];
6911 
6912         return sched_group_set_shares(css_tg(css), scale_load(weight));
6913 }
6914 #endif
6915 
6916 static void __maybe_unused cpu_period_quota_print(struct seq_file *sf,
6917                                                   long period, long quota)
6918 {
6919         if (quota < 0)
6920                 seq_puts(sf, "max");
6921         else
6922                 seq_printf(sf, "%ld", quota);
6923 
6924         seq_printf(sf, " %ld\n", period);
6925 }
6926 
6927 /* caller should put the current value in *@periodp before calling */
6928 static int __maybe_unused cpu_period_quota_parse(char *buf,
6929                                                  u64 *periodp, u64 *quotap)
6930 {
6931         char tok[21];   /* U64_MAX */
6932 
6933         if (!sscanf(buf, "%s %llu", tok, periodp))
6934                 return -EINVAL;
6935 
6936         *periodp *= NSEC_PER_USEC;
6937 
6938         if (sscanf(tok, "%llu", quotap))
6939                 *quotap *= NSEC_PER_USEC;
6940         else if (!strcmp(tok, "max"))
6941                 *quotap = RUNTIME_INF;
6942         else
6943                 return -EINVAL;
6944 
6945         return 0;
6946 }
6947 
6948 #ifdef CONFIG_CFS_BANDWIDTH
6949 static int cpu_max_show(struct seq_file *sf, void *v)
6950 {
6951         struct task_group *tg = css_tg(seq_css(sf));
6952 
6953         cpu_period_quota_print(sf, tg_get_cfs_period(tg), tg_get_cfs_quota(tg));
6954         return 0;
6955 }
6956 
6957 static ssize_t cpu_max_write(struct kernfs_open_file *of,
6958                              char *buf, size_t nbytes, loff_t off)
6959 {
6960         struct task_group *tg = css_tg(of_css(of));
6961         u64 period = tg_get_cfs_period(tg);
6962         u64 quota;
6963         int ret;
6964 
6965         ret = cpu_period_quota_parse(buf, &period, &quota);
6966         if (!ret)
6967                 ret = tg_set_cfs_bandwidth(tg, period, quota);
6968         return ret ?: nbytes;
6969 }
6970 #endif
6971 
6972 static struct cftype cpu_files[] = {
6973 #ifdef CONFIG_FAIR_GROUP_SCHED
6974         {
6975                 .name = "weight",
6976                 .flags = CFTYPE_NOT_ON_ROOT,
6977                 .read_u64 = cpu_weight_read_u64,
6978                 .write_u64 = cpu_weight_write_u64,
6979         },
6980         {
6981                 .name = "weight.nice",
6982                 .flags = CFTYPE_NOT_ON_ROOT,
6983                 .read_s64 = cpu_weight_nice_read_s64,
6984                 .write_s64 = cpu_weight_nice_write_s64,
6985         },
6986 #endif
6987 #ifdef CONFIG_CFS_BANDWIDTH
6988         {
6989                 .name = "max",
6990                 .flags = CFTYPE_NOT_ON_ROOT,
6991                 .seq_show = cpu_max_show,
6992                 .write = cpu_max_write,
6993         },
6994 #endif
6995         { }     /* terminate */
6996 };
6997 
6998 struct cgroup_subsys cpu_cgrp_subsys = {
6999         .css_alloc      = cpu_cgroup_css_alloc,
7000         .css_online     = cpu_cgroup_css_online,
7001         .css_released   = cpu_cgroup_css_released,
7002         .css_free       = cpu_cgroup_css_free,
7003         .css_extra_stat_show = cpu_extra_stat_show,
7004         .fork           = cpu_cgroup_fork,
7005         .can_attach     = cpu_cgroup_can_attach,
7006         .attach         = cpu_cgroup_attach,
7007         .legacy_cftypes = cpu_legacy_files,
7008         .dfl_cftypes    = cpu_files,
7009         .early_init     = true,
7010         .threaded       = true,
7011 };
7012 
7013 #endif  /* CONFIG_CGROUP_SCHED */
7014 
7015 void dump_cpu_task(int cpu)
7016 {
7017         pr_info("Task dump for CPU %d:\n", cpu);
7018         sched_show_task(cpu_curr(cpu));
7019 }
7020 
7021 /*
7022  * Nice levels are multiplicative, with a gentle 10% change for every
7023  * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
7024  * nice 1, it will get ~10% less CPU time than another CPU-bound task
7025  * that remained on nice 0.
7026  *
7027  * The "10% effect" is relative and cumulative: from _any_ nice level,
7028  * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
7029  * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
7030  * If a task goes up by ~10% and another task goes down by ~10% then
7031  * the relative distance between them is ~25%.)
7032  */
7033 const int sched_prio_to_weight[40] = {
7034  /* -20 */     88761,     71755,     56483,     46273,     36291,
7035  /* -15 */     29154,     23254,     18705,     14949,     11916,
7036  /* -10 */      9548,      7620,      6100,      4904,      3906,
7037  /*  -5 */      3121,      2501,      1991,      1586,      1277,
7038  /*   0 */      1024,       820,       655,       526,       423,
7039  /*   5 */       335,       272,       215,       172,       137,
7040  /*  10 */       110,        87,        70,        56,        45,
7041  /*  15 */        36,        29,        23,        18,        15,
7042 };
7043 
7044 /*
7045  * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated.
7046  *
7047  * In cases where the weight does not change often, we can use the
7048  * precalculated inverse to speed up arithmetics by turning divisions
7049  * into multiplications:
7050  */
7051 const u32 sched_prio_to_wmult[40] = {
7052  /* -20 */     48388,     59856,     76040,     92818,    118348,
7053  /* -15 */    147320,    184698,    229616,    287308,    360437,
7054  /* -10 */    449829,    563644,    704093,    875809,   1099582,
7055  /*  -5 */   1376151,   1717300,   2157191,   2708050,   3363326,
7056  /*   0 */   4194304,   5237765,   6557202,   8165337,  10153587,
7057  /*   5 */  12820798,  15790321,  19976592,  24970740,  31350126,
7058  /*  10 */  39045157,  49367440,  61356676,  76695844,  95443717,
7059  /*  15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
7060 };
7061 
7062 #undef CREATE_TRACE_POINTS
7063 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp