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

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
  4  * policies)
  5  */
  6 #include "sched.h"
  7 
  8 #include "pelt.h"
  9 
 10 int sched_rr_timeslice = RR_TIMESLICE;
 11 int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;
 12 
 13 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);
 14 
 15 struct rt_bandwidth def_rt_bandwidth;
 16 
 17 static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer)
 18 {
 19         struct rt_bandwidth *rt_b =
 20                 container_of(timer, struct rt_bandwidth, rt_period_timer);
 21         int idle = 0;
 22         int overrun;
 23 
 24         raw_spin_lock(&rt_b->rt_runtime_lock);
 25         for (;;) {
 26                 overrun = hrtimer_forward_now(timer, rt_b->rt_period);
 27                 if (!overrun)
 28                         break;
 29 
 30                 raw_spin_unlock(&rt_b->rt_runtime_lock);
 31                 idle = do_sched_rt_period_timer(rt_b, overrun);
 32                 raw_spin_lock(&rt_b->rt_runtime_lock);
 33         }
 34         if (idle)
 35                 rt_b->rt_period_active = 0;
 36         raw_spin_unlock(&rt_b->rt_runtime_lock);
 37 
 38         return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
 39 }
 40 
 41 void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime)
 42 {
 43         rt_b->rt_period = ns_to_ktime(period);
 44         rt_b->rt_runtime = runtime;
 45 
 46         raw_spin_lock_init(&rt_b->rt_runtime_lock);
 47 
 48         hrtimer_init(&rt_b->rt_period_timer,
 49                         CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 50         rt_b->rt_period_timer.function = sched_rt_period_timer;
 51 }
 52 
 53 static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
 54 {
 55         if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
 56                 return;
 57 
 58         raw_spin_lock(&rt_b->rt_runtime_lock);
 59         if (!rt_b->rt_period_active) {
 60                 rt_b->rt_period_active = 1;
 61                 /*
 62                  * SCHED_DEADLINE updates the bandwidth, as a run away
 63                  * RT task with a DL task could hog a CPU. But DL does
 64                  * not reset the period. If a deadline task was running
 65                  * without an RT task running, it can cause RT tasks to
 66                  * throttle when they start up. Kick the timer right away
 67                  * to update the period.
 68                  */
 69                 hrtimer_forward_now(&rt_b->rt_period_timer, ns_to_ktime(0));
 70                 hrtimer_start_expires(&rt_b->rt_period_timer, HRTIMER_MODE_ABS_PINNED);
 71         }
 72         raw_spin_unlock(&rt_b->rt_runtime_lock);
 73 }
 74 
 75 void init_rt_rq(struct rt_rq *rt_rq)
 76 {
 77         struct rt_prio_array *array;
 78         int i;
 79 
 80         array = &rt_rq->active;
 81         for (i = 0; i < MAX_RT_PRIO; i++) {
 82                 INIT_LIST_HEAD(array->queue + i);
 83                 __clear_bit(i, array->bitmap);
 84         }
 85         /* delimiter for bitsearch: */
 86         __set_bit(MAX_RT_PRIO, array->bitmap);
 87 
 88 #if defined CONFIG_SMP
 89         rt_rq->highest_prio.curr = MAX_RT_PRIO;
 90         rt_rq->highest_prio.next = MAX_RT_PRIO;
 91         rt_rq->rt_nr_migratory = 0;
 92         rt_rq->overloaded = 0;
 93         plist_head_init(&rt_rq->pushable_tasks);
 94 #endif /* CONFIG_SMP */
 95         /* We start is dequeued state, because no RT tasks are queued */
 96         rt_rq->rt_queued = 0;
 97 
 98         rt_rq->rt_time = 0;
 99         rt_rq->rt_throttled = 0;
100         rt_rq->rt_runtime = 0;
101         raw_spin_lock_init(&rt_rq->rt_runtime_lock);
102 }
103 
104 #ifdef CONFIG_RT_GROUP_SCHED
105 static void destroy_rt_bandwidth(struct rt_bandwidth *rt_b)
106 {
107         hrtimer_cancel(&rt_b->rt_period_timer);
108 }
109 
110 #define rt_entity_is_task(rt_se) (!(rt_se)->my_q)
111 
112 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
113 {
114 #ifdef CONFIG_SCHED_DEBUG
115         WARN_ON_ONCE(!rt_entity_is_task(rt_se));
116 #endif
117         return container_of(rt_se, struct task_struct, rt);
118 }
119 
120 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
121 {
122         return rt_rq->rq;
123 }
124 
125 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
126 {
127         return rt_se->rt_rq;
128 }
129 
130 static inline struct rq *rq_of_rt_se(struct sched_rt_entity *rt_se)
131 {
132         struct rt_rq *rt_rq = rt_se->rt_rq;
133 
134         return rt_rq->rq;
135 }
136 
137 void free_rt_sched_group(struct task_group *tg)
138 {
139         int i;
140 
141         if (tg->rt_se)
142                 destroy_rt_bandwidth(&tg->rt_bandwidth);
143 
144         for_each_possible_cpu(i) {
145                 if (tg->rt_rq)
146                         kfree(tg->rt_rq[i]);
147                 if (tg->rt_se)
148                         kfree(tg->rt_se[i]);
149         }
150 
151         kfree(tg->rt_rq);
152         kfree(tg->rt_se);
153 }
154 
155 void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
156                 struct sched_rt_entity *rt_se, int cpu,
157                 struct sched_rt_entity *parent)
158 {
159         struct rq *rq = cpu_rq(cpu);
160 
161         rt_rq->highest_prio.curr = MAX_RT_PRIO;
162         rt_rq->rt_nr_boosted = 0;
163         rt_rq->rq = rq;
164         rt_rq->tg = tg;
165 
166         tg->rt_rq[cpu] = rt_rq;
167         tg->rt_se[cpu] = rt_se;
168 
169         if (!rt_se)
170                 return;
171 
172         if (!parent)
173                 rt_se->rt_rq = &rq->rt;
174         else
175                 rt_se->rt_rq = parent->my_q;
176 
177         rt_se->my_q = rt_rq;
178         rt_se->parent = parent;
179         INIT_LIST_HEAD(&rt_se->run_list);
180 }
181 
182 int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
183 {
184         struct rt_rq *rt_rq;
185         struct sched_rt_entity *rt_se;
186         int i;
187 
188         tg->rt_rq = kcalloc(nr_cpu_ids, sizeof(rt_rq), GFP_KERNEL);
189         if (!tg->rt_rq)
190                 goto err;
191         tg->rt_se = kcalloc(nr_cpu_ids, sizeof(rt_se), GFP_KERNEL);
192         if (!tg->rt_se)
193                 goto err;
194 
195         init_rt_bandwidth(&tg->rt_bandwidth,
196                         ktime_to_ns(def_rt_bandwidth.rt_period), 0);
197 
198         for_each_possible_cpu(i) {
199                 rt_rq = kzalloc_node(sizeof(struct rt_rq),
200                                      GFP_KERNEL, cpu_to_node(i));
201                 if (!rt_rq)
202                         goto err;
203 
204                 rt_se = kzalloc_node(sizeof(struct sched_rt_entity),
205                                      GFP_KERNEL, cpu_to_node(i));
206                 if (!rt_se)
207                         goto err_free_rq;
208 
209                 init_rt_rq(rt_rq);
210                 rt_rq->rt_runtime = tg->rt_bandwidth.rt_runtime;
211                 init_tg_rt_entry(tg, rt_rq, rt_se, i, parent->rt_se[i]);
212         }
213 
214         return 1;
215 
216 err_free_rq:
217         kfree(rt_rq);
218 err:
219         return 0;
220 }
221 
222 #else /* CONFIG_RT_GROUP_SCHED */
223 
224 #define rt_entity_is_task(rt_se) (1)
225 
226 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
227 {
228         return container_of(rt_se, struct task_struct, rt);
229 }
230 
231 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
232 {
233         return container_of(rt_rq, struct rq, rt);
234 }
235 
236 static inline struct rq *rq_of_rt_se(struct sched_rt_entity *rt_se)
237 {
238         struct task_struct *p = rt_task_of(rt_se);
239 
240         return task_rq(p);
241 }
242 
243 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
244 {
245         struct rq *rq = rq_of_rt_se(rt_se);
246 
247         return &rq->rt;
248 }
249 
250 void free_rt_sched_group(struct task_group *tg) { }
251 
252 int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
253 {
254         return 1;
255 }
256 #endif /* CONFIG_RT_GROUP_SCHED */
257 
258 #ifdef CONFIG_SMP
259 
260 static void pull_rt_task(struct rq *this_rq);
261 
262 static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
263 {
264         /* Try to pull RT tasks here if we lower this rq's prio */
265         return rq->rt.highest_prio.curr > prev->prio;
266 }
267 
268 static inline int rt_overloaded(struct rq *rq)
269 {
270         return atomic_read(&rq->rd->rto_count);
271 }
272 
273 static inline void rt_set_overload(struct rq *rq)
274 {
275         if (!rq->online)
276                 return;
277 
278         cpumask_set_cpu(rq->cpu, rq->rd->rto_mask);
279         /*
280          * Make sure the mask is visible before we set
281          * the overload count. That is checked to determine
282          * if we should look at the mask. It would be a shame
283          * if we looked at the mask, but the mask was not
284          * updated yet.
285          *
286          * Matched by the barrier in pull_rt_task().
287          */
288         smp_wmb();
289         atomic_inc(&rq->rd->rto_count);
290 }
291 
292 static inline void rt_clear_overload(struct rq *rq)
293 {
294         if (!rq->online)
295                 return;
296 
297         /* the order here really doesn't matter */
298         atomic_dec(&rq->rd->rto_count);
299         cpumask_clear_cpu(rq->cpu, rq->rd->rto_mask);
300 }
301 
302 static void update_rt_migration(struct rt_rq *rt_rq)
303 {
304         if (rt_rq->rt_nr_migratory && rt_rq->rt_nr_total > 1) {
305                 if (!rt_rq->overloaded) {
306                         rt_set_overload(rq_of_rt_rq(rt_rq));
307                         rt_rq->overloaded = 1;
308                 }
309         } else if (rt_rq->overloaded) {
310                 rt_clear_overload(rq_of_rt_rq(rt_rq));
311                 rt_rq->overloaded = 0;
312         }
313 }
314 
315 static void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
316 {
317         struct task_struct *p;
318 
319         if (!rt_entity_is_task(rt_se))
320                 return;
321 
322         p = rt_task_of(rt_se);
323         rt_rq = &rq_of_rt_rq(rt_rq)->rt;
324 
325         rt_rq->rt_nr_total++;
326         if (p->nr_cpus_allowed > 1)
327                 rt_rq->rt_nr_migratory++;
328 
329         update_rt_migration(rt_rq);
330 }
331 
332 static void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
333 {
334         struct task_struct *p;
335 
336         if (!rt_entity_is_task(rt_se))
337                 return;
338 
339         p = rt_task_of(rt_se);
340         rt_rq = &rq_of_rt_rq(rt_rq)->rt;
341 
342         rt_rq->rt_nr_total--;
343         if (p->nr_cpus_allowed > 1)
344                 rt_rq->rt_nr_migratory--;
345 
346         update_rt_migration(rt_rq);
347 }
348 
349 static inline int has_pushable_tasks(struct rq *rq)
350 {
351         return !plist_head_empty(&rq->rt.pushable_tasks);
352 }
353 
354 static DEFINE_PER_CPU(struct callback_head, rt_push_head);
355 static DEFINE_PER_CPU(struct callback_head, rt_pull_head);
356 
357 static void push_rt_tasks(struct rq *);
358 static void pull_rt_task(struct rq *);
359 
360 static inline void rt_queue_push_tasks(struct rq *rq)
361 {
362         if (!has_pushable_tasks(rq))
363                 return;
364 
365         queue_balance_callback(rq, &per_cpu(rt_push_head, rq->cpu), push_rt_tasks);
366 }
367 
368 static inline void rt_queue_pull_task(struct rq *rq)
369 {
370         queue_balance_callback(rq, &per_cpu(rt_pull_head, rq->cpu), pull_rt_task);
371 }
372 
373 static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
374 {
375         plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
376         plist_node_init(&p->pushable_tasks, p->prio);
377         plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks);
378 
379         /* Update the highest prio pushable task */
380         if (p->prio < rq->rt.highest_prio.next)
381                 rq->rt.highest_prio.next = p->prio;
382 }
383 
384 static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
385 {
386         plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
387 
388         /* Update the new highest prio pushable task */
389         if (has_pushable_tasks(rq)) {
390                 p = plist_first_entry(&rq->rt.pushable_tasks,
391                                       struct task_struct, pushable_tasks);
392                 rq->rt.highest_prio.next = p->prio;
393         } else
394                 rq->rt.highest_prio.next = MAX_RT_PRIO;
395 }
396 
397 #else
398 
399 static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
400 {
401 }
402 
403 static inline void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
404 {
405 }
406 
407 static inline
408 void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
409 {
410 }
411 
412 static inline
413 void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
414 {
415 }
416 
417 static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
418 {
419         return false;
420 }
421 
422 static inline void pull_rt_task(struct rq *this_rq)
423 {
424 }
425 
426 static inline void rt_queue_push_tasks(struct rq *rq)
427 {
428 }
429 #endif /* CONFIG_SMP */
430 
431 static void enqueue_top_rt_rq(struct rt_rq *rt_rq);
432 static void dequeue_top_rt_rq(struct rt_rq *rt_rq);
433 
434 static inline int on_rt_rq(struct sched_rt_entity *rt_se)
435 {
436         return rt_se->on_rq;
437 }
438 
439 #ifdef CONFIG_RT_GROUP_SCHED
440 
441 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
442 {
443         if (!rt_rq->tg)
444                 return RUNTIME_INF;
445 
446         return rt_rq->rt_runtime;
447 }
448 
449 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
450 {
451         return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
452 }
453 
454 typedef struct task_group *rt_rq_iter_t;
455 
456 static inline struct task_group *next_task_group(struct task_group *tg)
457 {
458         do {
459                 tg = list_entry_rcu(tg->list.next,
460                         typeof(struct task_group), list);
461         } while (&tg->list != &task_groups && task_group_is_autogroup(tg));
462 
463         if (&tg->list == &task_groups)
464                 tg = NULL;
465 
466         return tg;
467 }
468 
469 #define for_each_rt_rq(rt_rq, iter, rq)                                 \
470         for (iter = container_of(&task_groups, typeof(*iter), list);    \
471                 (iter = next_task_group(iter)) &&                       \
472                 (rt_rq = iter->rt_rq[cpu_of(rq)]);)
473 
474 #define for_each_sched_rt_entity(rt_se) \
475         for (; rt_se; rt_se = rt_se->parent)
476 
477 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
478 {
479         return rt_se->my_q;
480 }
481 
482 static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags);
483 static void dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags);
484 
485 static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
486 {
487         struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
488         struct rq *rq = rq_of_rt_rq(rt_rq);
489         struct sched_rt_entity *rt_se;
490 
491         int cpu = cpu_of(rq);
492 
493         rt_se = rt_rq->tg->rt_se[cpu];
494 
495         if (rt_rq->rt_nr_running) {
496                 if (!rt_se)
497                         enqueue_top_rt_rq(rt_rq);
498                 else if (!on_rt_rq(rt_se))
499                         enqueue_rt_entity(rt_se, 0);
500 
501                 if (rt_rq->highest_prio.curr < curr->prio)
502                         resched_curr(rq);
503         }
504 }
505 
506 static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
507 {
508         struct sched_rt_entity *rt_se;
509         int cpu = cpu_of(rq_of_rt_rq(rt_rq));
510 
511         rt_se = rt_rq->tg->rt_se[cpu];
512 
513         if (!rt_se) {
514                 dequeue_top_rt_rq(rt_rq);
515                 /* Kick cpufreq (see the comment in kernel/sched/sched.h). */
516                 cpufreq_update_util(rq_of_rt_rq(rt_rq), 0);
517         }
518         else if (on_rt_rq(rt_se))
519                 dequeue_rt_entity(rt_se, 0);
520 }
521 
522 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
523 {
524         return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
525 }
526 
527 static int rt_se_boosted(struct sched_rt_entity *rt_se)
528 {
529         struct rt_rq *rt_rq = group_rt_rq(rt_se);
530         struct task_struct *p;
531 
532         if (rt_rq)
533                 return !!rt_rq->rt_nr_boosted;
534 
535         p = rt_task_of(rt_se);
536         return p->prio != p->normal_prio;
537 }
538 
539 #ifdef CONFIG_SMP
540 static inline const struct cpumask *sched_rt_period_mask(void)
541 {
542         return this_rq()->rd->span;
543 }
544 #else
545 static inline const struct cpumask *sched_rt_period_mask(void)
546 {
547         return cpu_online_mask;
548 }
549 #endif
550 
551 static inline
552 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
553 {
554         return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
555 }
556 
557 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
558 {
559         return &rt_rq->tg->rt_bandwidth;
560 }
561 
562 #else /* !CONFIG_RT_GROUP_SCHED */
563 
564 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
565 {
566         return rt_rq->rt_runtime;
567 }
568 
569 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
570 {
571         return ktime_to_ns(def_rt_bandwidth.rt_period);
572 }
573 
574 typedef struct rt_rq *rt_rq_iter_t;
575 
576 #define for_each_rt_rq(rt_rq, iter, rq) \
577         for ((void) iter, rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
578 
579 #define for_each_sched_rt_entity(rt_se) \
580         for (; rt_se; rt_se = NULL)
581 
582 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
583 {
584         return NULL;
585 }
586 
587 static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
588 {
589         struct rq *rq = rq_of_rt_rq(rt_rq);
590 
591         if (!rt_rq->rt_nr_running)
592                 return;
593 
594         enqueue_top_rt_rq(rt_rq);
595         resched_curr(rq);
596 }
597 
598 static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
599 {
600         dequeue_top_rt_rq(rt_rq);
601 }
602 
603 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
604 {
605         return rt_rq->rt_throttled;
606 }
607 
608 static inline const struct cpumask *sched_rt_period_mask(void)
609 {
610         return cpu_online_mask;
611 }
612 
613 static inline
614 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
615 {
616         return &cpu_rq(cpu)->rt;
617 }
618 
619 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
620 {
621         return &def_rt_bandwidth;
622 }
623 
624 #endif /* CONFIG_RT_GROUP_SCHED */
625 
626 bool sched_rt_bandwidth_account(struct rt_rq *rt_rq)
627 {
628         struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
629 
630         return (hrtimer_active(&rt_b->rt_period_timer) ||
631                 rt_rq->rt_time < rt_b->rt_runtime);
632 }
633 
634 #ifdef CONFIG_SMP
635 /*
636  * We ran out of runtime, see if we can borrow some from our neighbours.
637  */
638 static void do_balance_runtime(struct rt_rq *rt_rq)
639 {
640         struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
641         struct root_domain *rd = rq_of_rt_rq(rt_rq)->rd;
642         int i, weight;
643         u64 rt_period;
644 
645         weight = cpumask_weight(rd->span);
646 
647         raw_spin_lock(&rt_b->rt_runtime_lock);
648         rt_period = ktime_to_ns(rt_b->rt_period);
649         for_each_cpu(i, rd->span) {
650                 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
651                 s64 diff;
652 
653                 if (iter == rt_rq)
654                         continue;
655 
656                 raw_spin_lock(&iter->rt_runtime_lock);
657                 /*
658                  * Either all rqs have inf runtime and there's nothing to steal
659                  * or __disable_runtime() below sets a specific rq to inf to
660                  * indicate its been disabled and disalow stealing.
661                  */
662                 if (iter->rt_runtime == RUNTIME_INF)
663                         goto next;
664 
665                 /*
666                  * From runqueues with spare time, take 1/n part of their
667                  * spare time, but no more than our period.
668                  */
669                 diff = iter->rt_runtime - iter->rt_time;
670                 if (diff > 0) {
671                         diff = div_u64((u64)diff, weight);
672                         if (rt_rq->rt_runtime + diff > rt_period)
673                                 diff = rt_period - rt_rq->rt_runtime;
674                         iter->rt_runtime -= diff;
675                         rt_rq->rt_runtime += diff;
676                         if (rt_rq->rt_runtime == rt_period) {
677                                 raw_spin_unlock(&iter->rt_runtime_lock);
678                                 break;
679                         }
680                 }
681 next:
682                 raw_spin_unlock(&iter->rt_runtime_lock);
683         }
684         raw_spin_unlock(&rt_b->rt_runtime_lock);
685 }
686 
687 /*
688  * Ensure this RQ takes back all the runtime it lend to its neighbours.
689  */
690 static void __disable_runtime(struct rq *rq)
691 {
692         struct root_domain *rd = rq->rd;
693         rt_rq_iter_t iter;
694         struct rt_rq *rt_rq;
695 
696         if (unlikely(!scheduler_running))
697                 return;
698 
699         for_each_rt_rq(rt_rq, iter, rq) {
700                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
701                 s64 want;
702                 int i;
703 
704                 raw_spin_lock(&rt_b->rt_runtime_lock);
705                 raw_spin_lock(&rt_rq->rt_runtime_lock);
706                 /*
707                  * Either we're all inf and nobody needs to borrow, or we're
708                  * already disabled and thus have nothing to do, or we have
709                  * exactly the right amount of runtime to take out.
710                  */
711                 if (rt_rq->rt_runtime == RUNTIME_INF ||
712                                 rt_rq->rt_runtime == rt_b->rt_runtime)
713                         goto balanced;
714                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
715 
716                 /*
717                  * Calculate the difference between what we started out with
718                  * and what we current have, that's the amount of runtime
719                  * we lend and now have to reclaim.
720                  */
721                 want = rt_b->rt_runtime - rt_rq->rt_runtime;
722 
723                 /*
724                  * Greedy reclaim, take back as much as we can.
725                  */
726                 for_each_cpu(i, rd->span) {
727                         struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
728                         s64 diff;
729 
730                         /*
731                          * Can't reclaim from ourselves or disabled runqueues.
732                          */
733                         if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
734                                 continue;
735 
736                         raw_spin_lock(&iter->rt_runtime_lock);
737                         if (want > 0) {
738                                 diff = min_t(s64, iter->rt_runtime, want);
739                                 iter->rt_runtime -= diff;
740                                 want -= diff;
741                         } else {
742                                 iter->rt_runtime -= want;
743                                 want -= want;
744                         }
745                         raw_spin_unlock(&iter->rt_runtime_lock);
746 
747                         if (!want)
748                                 break;
749                 }
750 
751                 raw_spin_lock(&rt_rq->rt_runtime_lock);
752                 /*
753                  * We cannot be left wanting - that would mean some runtime
754                  * leaked out of the system.
755                  */
756                 BUG_ON(want);
757 balanced:
758                 /*
759                  * Disable all the borrow logic by pretending we have inf
760                  * runtime - in which case borrowing doesn't make sense.
761                  */
762                 rt_rq->rt_runtime = RUNTIME_INF;
763                 rt_rq->rt_throttled = 0;
764                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
765                 raw_spin_unlock(&rt_b->rt_runtime_lock);
766 
767                 /* Make rt_rq available for pick_next_task() */
768                 sched_rt_rq_enqueue(rt_rq);
769         }
770 }
771 
772 static void __enable_runtime(struct rq *rq)
773 {
774         rt_rq_iter_t iter;
775         struct rt_rq *rt_rq;
776 
777         if (unlikely(!scheduler_running))
778                 return;
779 
780         /*
781          * Reset each runqueue's bandwidth settings
782          */
783         for_each_rt_rq(rt_rq, iter, rq) {
784                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
785 
786                 raw_spin_lock(&rt_b->rt_runtime_lock);
787                 raw_spin_lock(&rt_rq->rt_runtime_lock);
788                 rt_rq->rt_runtime = rt_b->rt_runtime;
789                 rt_rq->rt_time = 0;
790                 rt_rq->rt_throttled = 0;
791                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
792                 raw_spin_unlock(&rt_b->rt_runtime_lock);
793         }
794 }
795 
796 static void balance_runtime(struct rt_rq *rt_rq)
797 {
798         if (!sched_feat(RT_RUNTIME_SHARE))
799                 return;
800 
801         if (rt_rq->rt_time > rt_rq->rt_runtime) {
802                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
803                 do_balance_runtime(rt_rq);
804                 raw_spin_lock(&rt_rq->rt_runtime_lock);
805         }
806 }
807 #else /* !CONFIG_SMP */
808 static inline void balance_runtime(struct rt_rq *rt_rq) {}
809 #endif /* CONFIG_SMP */
810 
811 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
812 {
813         int i, idle = 1, throttled = 0;
814         const struct cpumask *span;
815 
816         span = sched_rt_period_mask();
817 #ifdef CONFIG_RT_GROUP_SCHED
818         /*
819          * FIXME: isolated CPUs should really leave the root task group,
820          * whether they are isolcpus or were isolated via cpusets, lest
821          * the timer run on a CPU which does not service all runqueues,
822          * potentially leaving other CPUs indefinitely throttled.  If
823          * isolation is really required, the user will turn the throttle
824          * off to kill the perturbations it causes anyway.  Meanwhile,
825          * this maintains functionality for boot and/or troubleshooting.
826          */
827         if (rt_b == &root_task_group.rt_bandwidth)
828                 span = cpu_online_mask;
829 #endif
830         for_each_cpu(i, span) {
831                 int enqueue = 0;
832                 struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
833                 struct rq *rq = rq_of_rt_rq(rt_rq);
834                 int skip;
835 
836                 /*
837                  * When span == cpu_online_mask, taking each rq->lock
838                  * can be time-consuming. Try to avoid it when possible.
839                  */
840                 raw_spin_lock(&rt_rq->rt_runtime_lock);
841                 if (!sched_feat(RT_RUNTIME_SHARE) && rt_rq->rt_runtime != RUNTIME_INF)
842                         rt_rq->rt_runtime = rt_b->rt_runtime;
843                 skip = !rt_rq->rt_time && !rt_rq->rt_nr_running;
844                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
845                 if (skip)
846                         continue;
847 
848                 raw_spin_lock(&rq->lock);
849                 update_rq_clock(rq);
850 
851                 if (rt_rq->rt_time) {
852                         u64 runtime;
853 
854                         raw_spin_lock(&rt_rq->rt_runtime_lock);
855                         if (rt_rq->rt_throttled)
856                                 balance_runtime(rt_rq);
857                         runtime = rt_rq->rt_runtime;
858                         rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
859                         if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
860                                 rt_rq->rt_throttled = 0;
861                                 enqueue = 1;
862 
863                                 /*
864                                  * When we're idle and a woken (rt) task is
865                                  * throttled check_preempt_curr() will set
866                                  * skip_update and the time between the wakeup
867                                  * and this unthrottle will get accounted as
868                                  * 'runtime'.
869                                  */
870                                 if (rt_rq->rt_nr_running && rq->curr == rq->idle)
871                                         rq_clock_cancel_skipupdate(rq);
872                         }
873                         if (rt_rq->rt_time || rt_rq->rt_nr_running)
874                                 idle = 0;
875                         raw_spin_unlock(&rt_rq->rt_runtime_lock);
876                 } else if (rt_rq->rt_nr_running) {
877                         idle = 0;
878                         if (!rt_rq_throttled(rt_rq))
879                                 enqueue = 1;
880                 }
881                 if (rt_rq->rt_throttled)
882                         throttled = 1;
883 
884                 if (enqueue)
885                         sched_rt_rq_enqueue(rt_rq);
886                 raw_spin_unlock(&rq->lock);
887         }
888 
889         if (!throttled && (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF))
890                 return 1;
891 
892         return idle;
893 }
894 
895 static inline int rt_se_prio(struct sched_rt_entity *rt_se)
896 {
897 #ifdef CONFIG_RT_GROUP_SCHED
898         struct rt_rq *rt_rq = group_rt_rq(rt_se);
899 
900         if (rt_rq)
901                 return rt_rq->highest_prio.curr;
902 #endif
903 
904         return rt_task_of(rt_se)->prio;
905 }
906 
907 static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
908 {
909         u64 runtime = sched_rt_runtime(rt_rq);
910 
911         if (rt_rq->rt_throttled)
912                 return rt_rq_throttled(rt_rq);
913 
914         if (runtime >= sched_rt_period(rt_rq))
915                 return 0;
916 
917         balance_runtime(rt_rq);
918         runtime = sched_rt_runtime(rt_rq);
919         if (runtime == RUNTIME_INF)
920                 return 0;
921 
922         if (rt_rq->rt_time > runtime) {
923                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
924 
925                 /*
926                  * Don't actually throttle groups that have no runtime assigned
927                  * but accrue some time due to boosting.
928                  */
929                 if (likely(rt_b->rt_runtime)) {
930                         rt_rq->rt_throttled = 1;
931                         printk_deferred_once("sched: RT throttling activated\n");
932                 } else {
933                         /*
934                          * In case we did anyway, make it go away,
935                          * replenishment is a joke, since it will replenish us
936                          * with exactly 0 ns.
937                          */
938                         rt_rq->rt_time = 0;
939                 }
940 
941                 if (rt_rq_throttled(rt_rq)) {
942                         sched_rt_rq_dequeue(rt_rq);
943                         return 1;
944                 }
945         }
946 
947         return 0;
948 }
949 
950 /*
951  * Update the current task's runtime statistics. Skip current tasks that
952  * are not in our scheduling class.
953  */
954 static void update_curr_rt(struct rq *rq)
955 {
956         struct task_struct *curr = rq->curr;
957         struct sched_rt_entity *rt_se = &curr->rt;
958         u64 delta_exec;
959         u64 now;
960 
961         if (curr->sched_class != &rt_sched_class)
962                 return;
963 
964         now = rq_clock_task(rq);
965         delta_exec = now - curr->se.exec_start;
966         if (unlikely((s64)delta_exec <= 0))
967                 return;
968 
969         schedstat_set(curr->se.statistics.exec_max,
970                       max(curr->se.statistics.exec_max, delta_exec));
971 
972         curr->se.sum_exec_runtime += delta_exec;
973         account_group_exec_runtime(curr, delta_exec);
974 
975         curr->se.exec_start = now;
976         cgroup_account_cputime(curr, delta_exec);
977 
978         if (!rt_bandwidth_enabled())
979                 return;
980 
981         for_each_sched_rt_entity(rt_se) {
982                 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
983 
984                 if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
985                         raw_spin_lock(&rt_rq->rt_runtime_lock);
986                         rt_rq->rt_time += delta_exec;
987                         if (sched_rt_runtime_exceeded(rt_rq))
988                                 resched_curr(rq);
989                         raw_spin_unlock(&rt_rq->rt_runtime_lock);
990                 }
991         }
992 }
993 
994 static void
995 dequeue_top_rt_rq(struct rt_rq *rt_rq)
996 {
997         struct rq *rq = rq_of_rt_rq(rt_rq);
998 
999         BUG_ON(&rq->rt != rt_rq);
1000 
1001         if (!rt_rq->rt_queued)
1002                 return;
1003 
1004         BUG_ON(!rq->nr_running);
1005 
1006         sub_nr_running(rq, rt_rq->rt_nr_running);
1007         rt_rq->rt_queued = 0;
1008 
1009 }
1010 
1011 static void
1012 enqueue_top_rt_rq(struct rt_rq *rt_rq)
1013 {
1014         struct rq *rq = rq_of_rt_rq(rt_rq);
1015 
1016         BUG_ON(&rq->rt != rt_rq);
1017 
1018         if (rt_rq->rt_queued)
1019                 return;
1020 
1021         if (rt_rq_throttled(rt_rq))
1022                 return;
1023 
1024         if (rt_rq->rt_nr_running) {
1025                 add_nr_running(rq, rt_rq->rt_nr_running);
1026                 rt_rq->rt_queued = 1;
1027         }
1028 
1029         /* Kick cpufreq (see the comment in kernel/sched/sched.h). */
1030         cpufreq_update_util(rq, 0);
1031 }
1032 
1033 #if defined CONFIG_SMP
1034 
1035 static void
1036 inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
1037 {
1038         struct rq *rq = rq_of_rt_rq(rt_rq);
1039 
1040 #ifdef CONFIG_RT_GROUP_SCHED
1041         /*
1042          * Change rq's cpupri only if rt_rq is the top queue.
1043          */
1044         if (&rq->rt != rt_rq)
1045                 return;
1046 #endif
1047         if (rq->online && prio < prev_prio)
1048                 cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
1049 }
1050 
1051 static void
1052 dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
1053 {
1054         struct rq *rq = rq_of_rt_rq(rt_rq);
1055 
1056 #ifdef CONFIG_RT_GROUP_SCHED
1057         /*
1058          * Change rq's cpupri only if rt_rq is the top queue.
1059          */
1060         if (&rq->rt != rt_rq)
1061                 return;
1062 #endif
1063         if (rq->online && rt_rq->highest_prio.curr != prev_prio)
1064                 cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
1065 }
1066 
1067 #else /* CONFIG_SMP */
1068 
1069 static inline
1070 void inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
1071 static inline
1072 void dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
1073 
1074 #endif /* CONFIG_SMP */
1075 
1076 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
1077 static void
1078 inc_rt_prio(struct rt_rq *rt_rq, int prio)
1079 {
1080         int prev_prio = rt_rq->highest_prio.curr;
1081 
1082         if (prio < prev_prio)
1083                 rt_rq->highest_prio.curr = prio;
1084 
1085         inc_rt_prio_smp(rt_rq, prio, prev_prio);
1086 }
1087 
1088 static void
1089 dec_rt_prio(struct rt_rq *rt_rq, int prio)
1090 {
1091         int prev_prio = rt_rq->highest_prio.curr;
1092 
1093         if (rt_rq->rt_nr_running) {
1094 
1095                 WARN_ON(prio < prev_prio);
1096 
1097                 /*
1098                  * This may have been our highest task, and therefore
1099                  * we may have some recomputation to do
1100                  */
1101                 if (prio == prev_prio) {
1102                         struct rt_prio_array *array = &rt_rq->active;
1103 
1104                         rt_rq->highest_prio.curr =
1105                                 sched_find_first_bit(array->bitmap);
1106                 }
1107 
1108         } else
1109                 rt_rq->highest_prio.curr = MAX_RT_PRIO;
1110 
1111         dec_rt_prio_smp(rt_rq, prio, prev_prio);
1112 }
1113 
1114 #else
1115 
1116 static inline void inc_rt_prio(struct rt_rq *rt_rq, int prio) {}
1117 static inline void dec_rt_prio(struct rt_rq *rt_rq, int prio) {}
1118 
1119 #endif /* CONFIG_SMP || CONFIG_RT_GROUP_SCHED */
1120 
1121 #ifdef CONFIG_RT_GROUP_SCHED
1122 
1123 static void
1124 inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1125 {
1126         if (rt_se_boosted(rt_se))
1127                 rt_rq->rt_nr_boosted++;
1128 
1129         if (rt_rq->tg)
1130                 start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
1131 }
1132 
1133 static void
1134 dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1135 {
1136         if (rt_se_boosted(rt_se))
1137                 rt_rq->rt_nr_boosted--;
1138 
1139         WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
1140 }
1141 
1142 #else /* CONFIG_RT_GROUP_SCHED */
1143 
1144 static void
1145 inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1146 {
1147         start_rt_bandwidth(&def_rt_bandwidth);
1148 }
1149 
1150 static inline
1151 void dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) {}
1152 
1153 #endif /* CONFIG_RT_GROUP_SCHED */
1154 
1155 static inline
1156 unsigned int rt_se_nr_running(struct sched_rt_entity *rt_se)
1157 {
1158         struct rt_rq *group_rq = group_rt_rq(rt_se);
1159 
1160         if (group_rq)
1161                 return group_rq->rt_nr_running;
1162         else
1163                 return 1;
1164 }
1165 
1166 static inline
1167 unsigned int rt_se_rr_nr_running(struct sched_rt_entity *rt_se)
1168 {
1169         struct rt_rq *group_rq = group_rt_rq(rt_se);
1170         struct task_struct *tsk;
1171 
1172         if (group_rq)
1173                 return group_rq->rr_nr_running;
1174 
1175         tsk = rt_task_of(rt_se);
1176 
1177         return (tsk->policy == SCHED_RR) ? 1 : 0;
1178 }
1179 
1180 static inline
1181 void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1182 {
1183         int prio = rt_se_prio(rt_se);
1184 
1185         WARN_ON(!rt_prio(prio));
1186         rt_rq->rt_nr_running += rt_se_nr_running(rt_se);
1187         rt_rq->rr_nr_running += rt_se_rr_nr_running(rt_se);
1188 
1189         inc_rt_prio(rt_rq, prio);
1190         inc_rt_migration(rt_se, rt_rq);
1191         inc_rt_group(rt_se, rt_rq);
1192 }
1193 
1194 static inline
1195 void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1196 {
1197         WARN_ON(!rt_prio(rt_se_prio(rt_se)));
1198         WARN_ON(!rt_rq->rt_nr_running);
1199         rt_rq->rt_nr_running -= rt_se_nr_running(rt_se);
1200         rt_rq->rr_nr_running -= rt_se_rr_nr_running(rt_se);
1201 
1202         dec_rt_prio(rt_rq, rt_se_prio(rt_se));
1203         dec_rt_migration(rt_se, rt_rq);
1204         dec_rt_group(rt_se, rt_rq);
1205 }
1206 
1207 /*
1208  * Change rt_se->run_list location unless SAVE && !MOVE
1209  *
1210  * assumes ENQUEUE/DEQUEUE flags match
1211  */
1212 static inline bool move_entity(unsigned int flags)
1213 {
1214         if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE)
1215                 return false;
1216 
1217         return true;
1218 }
1219 
1220 static void __delist_rt_entity(struct sched_rt_entity *rt_se, struct rt_prio_array *array)
1221 {
1222         list_del_init(&rt_se->run_list);
1223 
1224         if (list_empty(array->queue + rt_se_prio(rt_se)))
1225                 __clear_bit(rt_se_prio(rt_se), array->bitmap);
1226 
1227         rt_se->on_list = 0;
1228 }
1229 
1230 static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1231 {
1232         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
1233         struct rt_prio_array *array = &rt_rq->active;
1234         struct rt_rq *group_rq = group_rt_rq(rt_se);
1235         struct list_head *queue = array->queue + rt_se_prio(rt_se);
1236 
1237         /*
1238          * Don't enqueue the group if its throttled, or when empty.
1239          * The latter is a consequence of the former when a child group
1240          * get throttled and the current group doesn't have any other
1241          * active members.
1242          */
1243         if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running)) {
1244                 if (rt_se->on_list)
1245                         __delist_rt_entity(rt_se, array);
1246                 return;
1247         }
1248 
1249         if (move_entity(flags)) {
1250                 WARN_ON_ONCE(rt_se->on_list);
1251                 if (flags & ENQUEUE_HEAD)
1252                         list_add(&rt_se->run_list, queue);
1253                 else
1254                         list_add_tail(&rt_se->run_list, queue);
1255 
1256                 __set_bit(rt_se_prio(rt_se), array->bitmap);
1257                 rt_se->on_list = 1;
1258         }
1259         rt_se->on_rq = 1;
1260 
1261         inc_rt_tasks(rt_se, rt_rq);
1262 }
1263 
1264 static void __dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1265 {
1266         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
1267         struct rt_prio_array *array = &rt_rq->active;
1268 
1269         if (move_entity(flags)) {
1270                 WARN_ON_ONCE(!rt_se->on_list);
1271                 __delist_rt_entity(rt_se, array);
1272         }
1273         rt_se->on_rq = 0;
1274 
1275         dec_rt_tasks(rt_se, rt_rq);
1276 }
1277 
1278 /*
1279  * Because the prio of an upper entry depends on the lower
1280  * entries, we must remove entries top - down.
1281  */
1282 static void dequeue_rt_stack(struct sched_rt_entity *rt_se, unsigned int flags)
1283 {
1284         struct sched_rt_entity *back = NULL;
1285 
1286         for_each_sched_rt_entity(rt_se) {
1287                 rt_se->back = back;
1288                 back = rt_se;
1289         }
1290 
1291         dequeue_top_rt_rq(rt_rq_of_se(back));
1292 
1293         for (rt_se = back; rt_se; rt_se = rt_se->back) {
1294                 if (on_rt_rq(rt_se))
1295                         __dequeue_rt_entity(rt_se, flags);
1296         }
1297 }
1298 
1299 static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1300 {
1301         struct rq *rq = rq_of_rt_se(rt_se);
1302 
1303         dequeue_rt_stack(rt_se, flags);
1304         for_each_sched_rt_entity(rt_se)
1305                 __enqueue_rt_entity(rt_se, flags);
1306         enqueue_top_rt_rq(&rq->rt);
1307 }
1308 
1309 static void dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1310 {
1311         struct rq *rq = rq_of_rt_se(rt_se);
1312 
1313         dequeue_rt_stack(rt_se, flags);
1314 
1315         for_each_sched_rt_entity(rt_se) {
1316                 struct rt_rq *rt_rq = group_rt_rq(rt_se);
1317 
1318                 if (rt_rq && rt_rq->rt_nr_running)
1319                         __enqueue_rt_entity(rt_se, flags);
1320         }
1321         enqueue_top_rt_rq(&rq->rt);
1322 }
1323 
1324 /*
1325  * Adding/removing a task to/from a priority array:
1326  */
1327 static void
1328 enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
1329 {
1330         struct sched_rt_entity *rt_se = &p->rt;
1331 
1332         if (flags & ENQUEUE_WAKEUP)
1333                 rt_se->timeout = 0;
1334 
1335         enqueue_rt_entity(rt_se, flags);
1336 
1337         if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
1338                 enqueue_pushable_task(rq, p);
1339 }
1340 
1341 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
1342 {
1343         struct sched_rt_entity *rt_se = &p->rt;
1344 
1345         update_curr_rt(rq);
1346         dequeue_rt_entity(rt_se, flags);
1347 
1348         dequeue_pushable_task(rq, p);
1349 }
1350 
1351 /*
1352  * Put task to the head or the end of the run list without the overhead of
1353  * dequeue followed by enqueue.
1354  */
1355 static void
1356 requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
1357 {
1358         if (on_rt_rq(rt_se)) {
1359                 struct rt_prio_array *array = &rt_rq->active;
1360                 struct list_head *queue = array->queue + rt_se_prio(rt_se);
1361 
1362                 if (head)
1363                         list_move(&rt_se->run_list, queue);
1364                 else
1365                         list_move_tail(&rt_se->run_list, queue);
1366         }
1367 }
1368 
1369 static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
1370 {
1371         struct sched_rt_entity *rt_se = &p->rt;
1372         struct rt_rq *rt_rq;
1373 
1374         for_each_sched_rt_entity(rt_se) {
1375                 rt_rq = rt_rq_of_se(rt_se);
1376                 requeue_rt_entity(rt_rq, rt_se, head);
1377         }
1378 }
1379 
1380 static void yield_task_rt(struct rq *rq)
1381 {
1382         requeue_task_rt(rq, rq->curr, 0);
1383 }
1384 
1385 #ifdef CONFIG_SMP
1386 static int find_lowest_rq(struct task_struct *task);
1387 
1388 static int
1389 select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
1390 {
1391         struct task_struct *curr;
1392         struct rq *rq;
1393 
1394         /* For anything but wake ups, just return the task_cpu */
1395         if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
1396                 goto out;
1397 
1398         rq = cpu_rq(cpu);
1399 
1400         rcu_read_lock();
1401         curr = READ_ONCE(rq->curr); /* unlocked access */
1402 
1403         /*
1404          * If the current task on @p's runqueue is an RT task, then
1405          * try to see if we can wake this RT task up on another
1406          * runqueue. Otherwise simply start this RT task
1407          * on its current runqueue.
1408          *
1409          * We want to avoid overloading runqueues. If the woken
1410          * task is a higher priority, then it will stay on this CPU
1411          * and the lower prio task should be moved to another CPU.
1412          * Even though this will probably make the lower prio task
1413          * lose its cache, we do not want to bounce a higher task
1414          * around just because it gave up its CPU, perhaps for a
1415          * lock?
1416          *
1417          * For equal prio tasks, we just let the scheduler sort it out.
1418          *
1419          * Otherwise, just let it ride on the affined RQ and the
1420          * post-schedule router will push the preempted task away
1421          *
1422          * This test is optimistic, if we get it wrong the load-balancer
1423          * will have to sort it out.
1424          */
1425         if (curr && unlikely(rt_task(curr)) &&
1426             (curr->nr_cpus_allowed < 2 ||
1427              curr->prio <= p->prio)) {
1428                 int target = find_lowest_rq(p);
1429 
1430                 /*
1431                  * Don't bother moving it if the destination CPU is
1432                  * not running a lower priority task.
1433                  */
1434                 if (target != -1 &&
1435                     p->prio < cpu_rq(target)->rt.highest_prio.curr)
1436                         cpu = target;
1437         }
1438         rcu_read_unlock();
1439 
1440 out:
1441         return cpu;
1442 }
1443 
1444 static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
1445 {
1446         /*
1447          * Current can't be migrated, useless to reschedule,
1448          * let's hope p can move out.
1449          */
1450         if (rq->curr->nr_cpus_allowed == 1 ||
1451             !cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
1452                 return;
1453 
1454         /*
1455          * p is migratable, so let's not schedule it and
1456          * see if it is pushed or pulled somewhere else.
1457          */
1458         if (p->nr_cpus_allowed != 1
1459             && cpupri_find(&rq->rd->cpupri, p, NULL))
1460                 return;
1461 
1462         /*
1463          * There appear to be other CPUs that can accept
1464          * the current task but none can run 'p', so lets reschedule
1465          * to try and push the current task away:
1466          */
1467         requeue_task_rt(rq, p, 1);
1468         resched_curr(rq);
1469 }
1470 
1471 #endif /* CONFIG_SMP */
1472 
1473 /*
1474  * Preempt the current task with a newly woken task if needed:
1475  */
1476 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flags)
1477 {
1478         if (p->prio < rq->curr->prio) {
1479                 resched_curr(rq);
1480                 return;
1481         }
1482 
1483 #ifdef CONFIG_SMP
1484         /*
1485          * If:
1486          *
1487          * - the newly woken task is of equal priority to the current task
1488          * - the newly woken task is non-migratable while current is migratable
1489          * - current will be preempted on the next reschedule
1490          *
1491          * we should check to see if current can readily move to a different
1492          * cpu.  If so, we will reschedule to allow the push logic to try
1493          * to move current somewhere else, making room for our non-migratable
1494          * task.
1495          */
1496         if (p->prio == rq->curr->prio && !test_tsk_need_resched(rq->curr))
1497                 check_preempt_equal_prio(rq, p);
1498 #endif
1499 }
1500 
1501 static inline void set_next_task(struct rq *rq, struct task_struct *p)
1502 {
1503         p->se.exec_start = rq_clock_task(rq);
1504 
1505         /* The running task is never eligible for pushing */
1506         dequeue_pushable_task(rq, p);
1507 }
1508 
1509 static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
1510                                                    struct rt_rq *rt_rq)
1511 {
1512         struct rt_prio_array *array = &rt_rq->active;
1513         struct sched_rt_entity *next = NULL;
1514         struct list_head *queue;
1515         int idx;
1516 
1517         idx = sched_find_first_bit(array->bitmap);
1518         BUG_ON(idx >= MAX_RT_PRIO);
1519 
1520         queue = array->queue + idx;
1521         next = list_entry(queue->next, struct sched_rt_entity, run_list);
1522 
1523         return next;
1524 }
1525 
1526 static struct task_struct *_pick_next_task_rt(struct rq *rq)
1527 {
1528         struct sched_rt_entity *rt_se;
1529         struct rt_rq *rt_rq  = &rq->rt;
1530 
1531         do {
1532                 rt_se = pick_next_rt_entity(rq, rt_rq);
1533                 BUG_ON(!rt_se);
1534                 rt_rq = group_rt_rq(rt_se);
1535         } while (rt_rq);
1536 
1537         return rt_task_of(rt_se);
1538 }
1539 
1540 static struct task_struct *
1541 pick_next_task_rt(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
1542 {
1543         struct task_struct *p;
1544         struct rt_rq *rt_rq = &rq->rt;
1545 
1546         if (need_pull_rt_task(rq, prev)) {
1547                 /*
1548                  * This is OK, because current is on_cpu, which avoids it being
1549                  * picked for load-balance and preemption/IRQs are still
1550                  * disabled avoiding further scheduler activity on it and we're
1551                  * being very careful to re-start the picking loop.
1552                  */
1553                 rq_unpin_lock(rq, rf);
1554                 pull_rt_task(rq);
1555                 rq_repin_lock(rq, rf);
1556                 /*
1557                  * pull_rt_task() can drop (and re-acquire) rq->lock; this
1558                  * means a dl or stop task can slip in, in which case we need
1559                  * to re-start task selection.
1560                  */
1561                 if (unlikely((rq->stop && task_on_rq_queued(rq->stop)) ||
1562                              rq->dl.dl_nr_running))
1563                         return RETRY_TASK;
1564         }
1565 
1566         /*
1567          * We may dequeue prev's rt_rq in put_prev_task().
1568          * So, we update time before rt_queued check.
1569          */
1570         if (prev->sched_class == &rt_sched_class)
1571                 update_curr_rt(rq);
1572 
1573         if (!rt_rq->rt_queued)
1574                 return NULL;
1575 
1576         put_prev_task(rq, prev);
1577 
1578         p = _pick_next_task_rt(rq);
1579 
1580         set_next_task(rq, p);
1581 
1582         rt_queue_push_tasks(rq);
1583 
1584         /*
1585          * If prev task was rt, put_prev_task() has already updated the
1586          * utilization. We only care of the case where we start to schedule a
1587          * rt task
1588          */
1589         if (rq->curr->sched_class != &rt_sched_class)
1590                 update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0);
1591 
1592         return p;
1593 }
1594 
1595 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
1596 {
1597         update_curr_rt(rq);
1598 
1599         update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 1);
1600 
1601         /*
1602          * The previous task needs to be made eligible for pushing
1603          * if it is still active
1604          */
1605         if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1)
1606                 enqueue_pushable_task(rq, p);
1607 }
1608 
1609 #ifdef CONFIG_SMP
1610 
1611 /* Only try algorithms three times */
1612 #define RT_MAX_TRIES 3
1613 
1614 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
1615 {
1616         if (!task_running(rq, p) &&
1617             cpumask_test_cpu(cpu, p->cpus_ptr))
1618                 return 1;
1619 
1620         return 0;
1621 }
1622 
1623 /*
1624  * Return the highest pushable rq's task, which is suitable to be executed
1625  * on the CPU, NULL otherwise
1626  */
1627 static struct task_struct *pick_highest_pushable_task(struct rq *rq, int cpu)
1628 {
1629         struct plist_head *head = &rq->rt.pushable_tasks;
1630         struct task_struct *p;
1631 
1632         if (!has_pushable_tasks(rq))
1633                 return NULL;
1634 
1635         plist_for_each_entry(p, head, pushable_tasks) {
1636                 if (pick_rt_task(rq, p, cpu))
1637                         return p;
1638         }
1639 
1640         return NULL;
1641 }
1642 
1643 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
1644 
1645 static int find_lowest_rq(struct task_struct *task)
1646 {
1647         struct sched_domain *sd;
1648         struct cpumask *lowest_mask = this_cpu_cpumask_var_ptr(local_cpu_mask);
1649         int this_cpu = smp_processor_id();
1650         int cpu      = task_cpu(task);
1651 
1652         /* Make sure the mask is initialized first */
1653         if (unlikely(!lowest_mask))
1654                 return -1;
1655 
1656         if (task->nr_cpus_allowed == 1)
1657                 return -1; /* No other targets possible */
1658 
1659         if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
1660                 return -1; /* No targets found */
1661 
1662         /*
1663          * At this point we have built a mask of CPUs representing the
1664          * lowest priority tasks in the system.  Now we want to elect
1665          * the best one based on our affinity and topology.
1666          *
1667          * We prioritize the last CPU that the task executed on since
1668          * it is most likely cache-hot in that location.
1669          */
1670         if (cpumask_test_cpu(cpu, lowest_mask))
1671                 return cpu;
1672 
1673         /*
1674          * Otherwise, we consult the sched_domains span maps to figure
1675          * out which CPU is logically closest to our hot cache data.
1676          */
1677         if (!cpumask_test_cpu(this_cpu, lowest_mask))
1678                 this_cpu = -1; /* Skip this_cpu opt if not among lowest */
1679 
1680         rcu_read_lock();
1681         for_each_domain(cpu, sd) {
1682                 if (sd->flags & SD_WAKE_AFFINE) {
1683                         int best_cpu;
1684 
1685                         /*
1686                          * "this_cpu" is cheaper to preempt than a
1687                          * remote processor.
1688                          */
1689                         if (this_cpu != -1 &&
1690                             cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
1691                                 rcu_read_unlock();
1692                                 return this_cpu;
1693                         }
1694 
1695                         best_cpu = cpumask_first_and(lowest_mask,
1696                                                      sched_domain_span(sd));
1697                         if (best_cpu < nr_cpu_ids) {
1698                                 rcu_read_unlock();
1699                                 return best_cpu;
1700                         }
1701                 }
1702         }
1703         rcu_read_unlock();
1704 
1705         /*
1706          * And finally, if there were no matches within the domains
1707          * just give the caller *something* to work with from the compatible
1708          * locations.
1709          */
1710         if (this_cpu != -1)
1711                 return this_cpu;
1712 
1713         cpu = cpumask_any(lowest_mask);
1714         if (cpu < nr_cpu_ids)
1715                 return cpu;
1716 
1717         return -1;
1718 }
1719 
1720 /* Will lock the rq it finds */
1721 static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1722 {
1723         struct rq *lowest_rq = NULL;
1724         int tries;
1725         int cpu;
1726 
1727         for (tries = 0; tries < RT_MAX_TRIES; tries++) {
1728                 cpu = find_lowest_rq(task);
1729 
1730                 if ((cpu == -1) || (cpu == rq->cpu))
1731                         break;
1732 
1733                 lowest_rq = cpu_rq(cpu);
1734 
1735                 if (lowest_rq->rt.highest_prio.curr <= task->prio) {
1736                         /*
1737                          * Target rq has tasks of equal or higher priority,
1738                          * retrying does not release any lock and is unlikely
1739                          * to yield a different result.
1740                          */
1741                         lowest_rq = NULL;
1742                         break;
1743                 }
1744 
1745                 /* if the prio of this runqueue changed, try again */
1746                 if (double_lock_balance(rq, lowest_rq)) {
1747                         /*
1748                          * We had to unlock the run queue. In
1749                          * the mean time, task could have
1750                          * migrated already or had its affinity changed.
1751                          * Also make sure that it wasn't scheduled on its rq.
1752                          */
1753                         if (unlikely(task_rq(task) != rq ||
1754                                      !cpumask_test_cpu(lowest_rq->cpu, task->cpus_ptr) ||
1755                                      task_running(rq, task) ||
1756                                      !rt_task(task) ||
1757                                      !task_on_rq_queued(task))) {
1758 
1759                                 double_unlock_balance(rq, lowest_rq);
1760                                 lowest_rq = NULL;
1761                                 break;
1762                         }
1763                 }
1764 
1765                 /* If this rq is still suitable use it. */
1766                 if (lowest_rq->rt.highest_prio.curr > task->prio)
1767                         break;
1768 
1769                 /* try again */
1770                 double_unlock_balance(rq, lowest_rq);
1771                 lowest_rq = NULL;
1772         }
1773 
1774         return lowest_rq;
1775 }
1776 
1777 static struct task_struct *pick_next_pushable_task(struct rq *rq)
1778 {
1779         struct task_struct *p;
1780 
1781         if (!has_pushable_tasks(rq))
1782                 return NULL;
1783 
1784         p = plist_first_entry(&rq->rt.pushable_tasks,
1785                               struct task_struct, pushable_tasks);
1786 
1787         BUG_ON(rq->cpu != task_cpu(p));
1788         BUG_ON(task_current(rq, p));
1789         BUG_ON(p->nr_cpus_allowed <= 1);
1790 
1791         BUG_ON(!task_on_rq_queued(p));
1792         BUG_ON(!rt_task(p));
1793 
1794         return p;
1795 }
1796 
1797 /*
1798  * If the current CPU has more than one RT task, see if the non
1799  * running task can migrate over to a CPU that is running a task
1800  * of lesser priority.
1801  */
1802 static int push_rt_task(struct rq *rq)
1803 {
1804         struct task_struct *next_task;
1805         struct rq *lowest_rq;
1806         int ret = 0;
1807 
1808         if (!rq->rt.overloaded)
1809                 return 0;
1810 
1811         next_task = pick_next_pushable_task(rq);
1812         if (!next_task)
1813                 return 0;
1814 
1815 retry:
1816         if (WARN_ON(next_task == rq->curr))
1817                 return 0;
1818 
1819         /*
1820          * It's possible that the next_task slipped in of
1821          * higher priority than current. If that's the case
1822          * just reschedule current.
1823          */
1824         if (unlikely(next_task->prio < rq->curr->prio)) {
1825                 resched_curr(rq);
1826                 return 0;
1827         }
1828 
1829         /* We might release rq lock */
1830         get_task_struct(next_task);
1831 
1832         /* find_lock_lowest_rq locks the rq if found */
1833         lowest_rq = find_lock_lowest_rq(next_task, rq);
1834         if (!lowest_rq) {
1835                 struct task_struct *task;
1836                 /*
1837                  * find_lock_lowest_rq releases rq->lock
1838                  * so it is possible that next_task has migrated.
1839                  *
1840                  * We need to make sure that the task is still on the same
1841                  * run-queue and is also still the next task eligible for
1842                  * pushing.
1843                  */
1844                 task = pick_next_pushable_task(rq);
1845                 if (task == next_task) {
1846                         /*
1847                          * The task hasn't migrated, and is still the next
1848                          * eligible task, but we failed to find a run-queue
1849                          * to push it to.  Do not retry in this case, since
1850                          * other CPUs will pull from us when ready.
1851                          */
1852                         goto out;
1853                 }
1854 
1855                 if (!task)
1856                         /* No more tasks, just exit */
1857                         goto out;
1858 
1859                 /*
1860                  * Something has shifted, try again.
1861                  */
1862                 put_task_struct(next_task);
1863                 next_task = task;
1864                 goto retry;
1865         }
1866 
1867         deactivate_task(rq, next_task, 0);
1868         set_task_cpu(next_task, lowest_rq->cpu);
1869         activate_task(lowest_rq, next_task, 0);
1870         ret = 1;
1871 
1872         resched_curr(lowest_rq);
1873 
1874         double_unlock_balance(rq, lowest_rq);
1875 
1876 out:
1877         put_task_struct(next_task);
1878 
1879         return ret;
1880 }
1881 
1882 static void push_rt_tasks(struct rq *rq)
1883 {
1884         /* push_rt_task will return true if it moved an RT */
1885         while (push_rt_task(rq))
1886                 ;
1887 }
1888 
1889 #ifdef HAVE_RT_PUSH_IPI
1890 
1891 /*
1892  * When a high priority task schedules out from a CPU and a lower priority
1893  * task is scheduled in, a check is made to see if there's any RT tasks
1894  * on other CPUs that are waiting to run because a higher priority RT task
1895  * is currently running on its CPU. In this case, the CPU with multiple RT
1896  * tasks queued on it (overloaded) needs to be notified that a CPU has opened
1897  * up that may be able to run one of its non-running queued RT tasks.
1898  *
1899  * All CPUs with overloaded RT tasks need to be notified as there is currently
1900  * no way to know which of these CPUs have the highest priority task waiting
1901  * to run. Instead of trying to take a spinlock on each of these CPUs,
1902  * which has shown to cause large latency when done on machines with many
1903  * CPUs, sending an IPI to the CPUs to have them push off the overloaded
1904  * RT tasks waiting to run.
1905  *
1906  * Just sending an IPI to each of the CPUs is also an issue, as on large
1907  * count CPU machines, this can cause an IPI storm on a CPU, especially
1908  * if its the only CPU with multiple RT tasks queued, and a large number
1909  * of CPUs scheduling a lower priority task at the same time.
1910  *
1911  * Each root domain has its own irq work function that can iterate over
1912  * all CPUs with RT overloaded tasks. Since all CPUs with overloaded RT
1913  * tassk must be checked if there's one or many CPUs that are lowering
1914  * their priority, there's a single irq work iterator that will try to
1915  * push off RT tasks that are waiting to run.
1916  *
1917  * When a CPU schedules a lower priority task, it will kick off the
1918  * irq work iterator that will jump to each CPU with overloaded RT tasks.
1919  * As it only takes the first CPU that schedules a lower priority task
1920  * to start the process, the rto_start variable is incremented and if
1921  * the atomic result is one, then that CPU will try to take the rto_lock.
1922  * This prevents high contention on the lock as the process handles all
1923  * CPUs scheduling lower priority tasks.
1924  *
1925  * All CPUs that are scheduling a lower priority task will increment the
1926  * rt_loop_next variable. This will make sure that the irq work iterator
1927  * checks all RT overloaded CPUs whenever a CPU schedules a new lower
1928  * priority task, even if the iterator is in the middle of a scan. Incrementing
1929  * the rt_loop_next will cause the iterator to perform another scan.
1930  *
1931  */
1932 static int rto_next_cpu(struct root_domain *rd)
1933 {
1934         int next;
1935         int cpu;
1936 
1937         /*
1938          * When starting the IPI RT pushing, the rto_cpu is set to -1,
1939          * rt_next_cpu() will simply return the first CPU found in
1940          * the rto_mask.
1941          *
1942          * If rto_next_cpu() is called with rto_cpu is a valid CPU, it
1943          * will return the next CPU found in the rto_mask.
1944          *
1945          * If there are no more CPUs left in the rto_mask, then a check is made
1946          * against rto_loop and rto_loop_next. rto_loop is only updated with
1947          * the rto_lock held, but any CPU may increment the rto_loop_next
1948          * without any locking.
1949          */
1950         for (;;) {
1951 
1952                 /* When rto_cpu is -1 this acts like cpumask_first() */
1953                 cpu = cpumask_next(rd->rto_cpu, rd->rto_mask);
1954 
1955                 rd->rto_cpu = cpu;
1956 
1957                 if (cpu < nr_cpu_ids)
1958                         return cpu;
1959 
1960                 rd->rto_cpu = -1;
1961 
1962                 /*
1963                  * ACQUIRE ensures we see the @rto_mask changes
1964                  * made prior to the @next value observed.
1965                  *
1966                  * Matches WMB in rt_set_overload().
1967                  */
1968                 next = atomic_read_acquire(&rd->rto_loop_next);
1969 
1970                 if (rd->rto_loop == next)
1971                         break;
1972 
1973                 rd->rto_loop = next;
1974         }
1975 
1976         return -1;
1977 }
1978 
1979 static inline bool rto_start_trylock(atomic_t *v)
1980 {
1981         return !atomic_cmpxchg_acquire(v, 0, 1);
1982 }
1983 
1984 static inline void rto_start_unlock(atomic_t *v)
1985 {
1986         atomic_set_release(v, 0);
1987 }
1988 
1989 static void tell_cpu_to_push(struct rq *rq)
1990 {
1991         int cpu = -1;
1992 
1993         /* Keep the loop going if the IPI is currently active */
1994         atomic_inc(&rq->rd->rto_loop_next);
1995 
1996         /* Only one CPU can initiate a loop at a time */
1997         if (!rto_start_trylock(&rq->rd->rto_loop_start))
1998                 return;
1999 
2000         raw_spin_lock(&rq->rd->rto_lock);
2001 
2002         /*
2003          * The rto_cpu is updated under the lock, if it has a valid CPU
2004          * then the IPI is still running and will continue due to the
2005          * update to loop_next, and nothing needs to be done here.
2006          * Otherwise it is finishing up and an ipi needs to be sent.
2007          */
2008         if (rq->rd->rto_cpu < 0)
2009                 cpu = rto_next_cpu(rq->rd);
2010 
2011         raw_spin_unlock(&rq->rd->rto_lock);
2012 
2013         rto_start_unlock(&rq->rd->rto_loop_start);
2014 
2015         if (cpu >= 0) {
2016                 /* Make sure the rd does not get freed while pushing */
2017                 sched_get_rd(rq->rd);
2018                 irq_work_queue_on(&rq->rd->rto_push_work, cpu);
2019         }
2020 }
2021 
2022 /* Called from hardirq context */
2023 void rto_push_irq_work_func(struct irq_work *work)
2024 {
2025         struct root_domain *rd =
2026                 container_of(work, struct root_domain, rto_push_work);
2027         struct rq *rq;
2028         int cpu;
2029 
2030         rq = this_rq();
2031 
2032         /*
2033          * We do not need to grab the lock to check for has_pushable_tasks.
2034          * When it gets updated, a check is made if a push is possible.
2035          */
2036         if (has_pushable_tasks(rq)) {
2037                 raw_spin_lock(&rq->lock);
2038                 push_rt_tasks(rq);
2039                 raw_spin_unlock(&rq->lock);
2040         }
2041 
2042         raw_spin_lock(&rd->rto_lock);
2043 
2044         /* Pass the IPI to the next rt overloaded queue */
2045         cpu = rto_next_cpu(rd);
2046 
2047         raw_spin_unlock(&rd->rto_lock);
2048 
2049         if (cpu < 0) {
2050                 sched_put_rd(rd);
2051                 return;
2052         }
2053 
2054         /* Try the next RT overloaded CPU */
2055         irq_work_queue_on(&rd->rto_push_work, cpu);
2056 }
2057 #endif /* HAVE_RT_PUSH_IPI */
2058 
2059 static void pull_rt_task(struct rq *this_rq)
2060 {
2061         int this_cpu = this_rq->cpu, cpu;
2062         bool resched = false;
2063         struct task_struct *p;
2064         struct rq *src_rq;
2065         int rt_overload_count = rt_overloaded(this_rq);
2066 
2067         if (likely(!rt_overload_count))
2068                 return;
2069 
2070         /*
2071          * Match the barrier from rt_set_overloaded; this guarantees that if we
2072          * see overloaded we must also see the rto_mask bit.
2073          */
2074         smp_rmb();
2075 
2076         /* If we are the only overloaded CPU do nothing */
2077         if (rt_overload_count == 1 &&
2078             cpumask_test_cpu(this_rq->cpu, this_rq->rd->rto_mask))
2079                 return;
2080 
2081 #ifdef HAVE_RT_PUSH_IPI
2082         if (sched_feat(RT_PUSH_IPI)) {
2083                 tell_cpu_to_push(this_rq);
2084                 return;
2085         }
2086 #endif
2087 
2088         for_each_cpu(cpu, this_rq->rd->rto_mask) {
2089                 if (this_cpu == cpu)
2090                         continue;
2091 
2092                 src_rq = cpu_rq(cpu);
2093 
2094                 /*
2095                  * Don't bother taking the src_rq->lock if the next highest
2096                  * task is known to be lower-priority than our current task.
2097                  * This may look racy, but if this value is about to go
2098                  * logically higher, the src_rq will push this task away.
2099                  * And if its going logically lower, we do not care
2100                  */
2101                 if (src_rq->rt.highest_prio.next >=
2102                     this_rq->rt.highest_prio.curr)
2103                         continue;
2104 
2105                 /*
2106                  * We can potentially drop this_rq's lock in
2107                  * double_lock_balance, and another CPU could
2108                  * alter this_rq
2109                  */
2110                 double_lock_balance(this_rq, src_rq);
2111 
2112                 /*
2113                  * We can pull only a task, which is pushable
2114                  * on its rq, and no others.
2115                  */
2116                 p = pick_highest_pushable_task(src_rq, this_cpu);
2117 
2118                 /*
2119                  * Do we have an RT task that preempts
2120                  * the to-be-scheduled task?
2121                  */
2122                 if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
2123                         WARN_ON(p == src_rq->curr);
2124                         WARN_ON(!task_on_rq_queued(p));
2125 
2126                         /*
2127                          * There's a chance that p is higher in priority
2128                          * than what's currently running on its CPU.
2129                          * This is just that p is wakeing up and hasn't
2130                          * had a chance to schedule. We only pull
2131                          * p if it is lower in priority than the
2132                          * current task on the run queue
2133                          */
2134                         if (p->prio < src_rq->curr->prio)
2135                                 goto skip;
2136 
2137                         resched = true;
2138 
2139                         deactivate_task(src_rq, p, 0);
2140                         set_task_cpu(p, this_cpu);
2141                         activate_task(this_rq, p, 0);
2142                         /*
2143                          * We continue with the search, just in
2144                          * case there's an even higher prio task
2145                          * in another runqueue. (low likelihood
2146                          * but possible)
2147                          */
2148                 }
2149 skip:
2150                 double_unlock_balance(this_rq, src_rq);
2151         }
2152 
2153         if (resched)
2154                 resched_curr(this_rq);
2155 }
2156 
2157 /*
2158  * If we are not running and we are not going to reschedule soon, we should
2159  * try to push tasks away now
2160  */
2161 static void task_woken_rt(struct rq *rq, struct task_struct *p)
2162 {
2163         if (!task_running(rq, p) &&
2164             !test_tsk_need_resched(rq->curr) &&
2165             p->nr_cpus_allowed > 1 &&
2166             (dl_task(rq->curr) || rt_task(rq->curr)) &&
2167             (rq->curr->nr_cpus_allowed < 2 ||
2168              rq->curr->prio <= p->prio))
2169                 push_rt_tasks(rq);
2170 }
2171 
2172 /* Assumes rq->lock is held */
2173 static void rq_online_rt(struct rq *rq)
2174 {
2175         if (rq->rt.overloaded)
2176                 rt_set_overload(rq);
2177 
2178         __enable_runtime(rq);
2179 
2180         cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
2181 }
2182 
2183 /* Assumes rq->lock is held */
2184 static void rq_offline_rt(struct rq *rq)
2185 {
2186         if (rq->rt.overloaded)
2187                 rt_clear_overload(rq);
2188 
2189         __disable_runtime(rq);
2190 
2191         cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
2192 }
2193 
2194 /*
2195  * When switch from the rt queue, we bring ourselves to a position
2196  * that we might want to pull RT tasks from other runqueues.
2197  */
2198 static void switched_from_rt(struct rq *rq, struct task_struct *p)
2199 {
2200         /*
2201          * If there are other RT tasks then we will reschedule
2202          * and the scheduling of the other RT tasks will handle
2203          * the balancing. But if we are the last RT task
2204          * we may need to handle the pulling of RT tasks
2205          * now.
2206          */
2207         if (!task_on_rq_queued(p) || rq->rt.rt_nr_running)
2208                 return;
2209 
2210         rt_queue_pull_task(rq);
2211 }
2212 
2213 void __init init_sched_rt_class(void)
2214 {
2215         unsigned int i;
2216 
2217         for_each_possible_cpu(i) {
2218                 zalloc_cpumask_var_node(&per_cpu(local_cpu_mask, i),
2219                                         GFP_KERNEL, cpu_to_node(i));
2220         }
2221 }
2222 #endif /* CONFIG_SMP */
2223 
2224 /*
2225  * When switching a task to RT, we may overload the runqueue
2226  * with RT tasks. In this case we try to push them off to
2227  * other runqueues.
2228  */
2229 static void switched_to_rt(struct rq *rq, struct task_struct *p)
2230 {
2231         /*
2232          * If we are already running, then there's nothing
2233          * that needs to be done. But if we are not running
2234          * we may need to preempt the current running task.
2235          * If that current running task is also an RT task
2236          * then see if we can move to another run queue.
2237          */
2238         if (task_on_rq_queued(p) && rq->curr != p) {
2239 #ifdef CONFIG_SMP
2240                 if (p->nr_cpus_allowed > 1 && rq->rt.overloaded)
2241                         rt_queue_push_tasks(rq);
2242 #endif /* CONFIG_SMP */
2243                 if (p->prio < rq->curr->prio && cpu_online(cpu_of(rq)))
2244                         resched_curr(rq);
2245         }
2246 }
2247 
2248 /*
2249  * Priority of the task has changed. This may cause
2250  * us to initiate a push or pull.
2251  */
2252 static void
2253 prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
2254 {
2255         if (!task_on_rq_queued(p))
2256                 return;
2257 
2258         if (rq->curr == p) {
2259 #ifdef CONFIG_SMP
2260                 /*
2261                  * If our priority decreases while running, we
2262                  * may need to pull tasks to this runqueue.
2263                  */
2264                 if (oldprio < p->prio)
2265                         rt_queue_pull_task(rq);
2266 
2267                 /*
2268                  * If there's a higher priority task waiting to run
2269                  * then reschedule.
2270                  */
2271                 if (p->prio > rq->rt.highest_prio.curr)
2272                         resched_curr(rq);
2273 #else
2274                 /* For UP simply resched on drop of prio */
2275                 if (oldprio < p->prio)
2276                         resched_curr(rq);
2277 #endif /* CONFIG_SMP */
2278         } else {
2279                 /*
2280                  * This task is not running, but if it is
2281                  * greater than the current running task
2282                  * then reschedule.
2283                  */
2284                 if (p->prio < rq->curr->prio)
2285                         resched_curr(rq);
2286         }
2287 }
2288 
2289 #ifdef CONFIG_POSIX_TIMERS
2290 static void watchdog(struct rq *rq, struct task_struct *p)
2291 {
2292         unsigned long soft, hard;
2293 
2294         /* max may change after cur was read, this will be fixed next tick */
2295         soft = task_rlimit(p, RLIMIT_RTTIME);
2296         hard = task_rlimit_max(p, RLIMIT_RTTIME);
2297 
2298         if (soft != RLIM_INFINITY) {
2299                 unsigned long next;
2300 
2301                 if (p->rt.watchdog_stamp != jiffies) {
2302                         p->rt.timeout++;
2303                         p->rt.watchdog_stamp = jiffies;
2304                 }
2305 
2306                 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
2307                 if (p->rt.timeout > next)
2308                         p->cputime_expires.sched_exp = p->se.sum_exec_runtime;
2309         }
2310 }
2311 #else
2312 static inline void watchdog(struct rq *rq, struct task_struct *p) { }
2313 #endif
2314 
2315 /*
2316  * scheduler tick hitting a task of our scheduling class.
2317  *
2318  * NOTE: This function can be called remotely by the tick offload that
2319  * goes along full dynticks. Therefore no local assumption can be made
2320  * and everything must be accessed through the @rq and @curr passed in
2321  * parameters.
2322  */
2323 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
2324 {
2325         struct sched_rt_entity *rt_se = &p->rt;
2326 
2327         update_curr_rt(rq);
2328         update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 1);
2329 
2330         watchdog(rq, p);
2331 
2332         /*
2333          * RR tasks need a special form of timeslice management.
2334          * FIFO tasks have no timeslices.
2335          */
2336         if (p->policy != SCHED_RR)
2337                 return;
2338 
2339         if (--p->rt.time_slice)
2340                 return;
2341 
2342         p->rt.time_slice = sched_rr_timeslice;
2343 
2344         /*
2345          * Requeue to the end of queue if we (and all of our ancestors) are not
2346          * the only element on the queue
2347          */
2348         for_each_sched_rt_entity(rt_se) {
2349                 if (rt_se->run_list.prev != rt_se->run_list.next) {
2350                         requeue_task_rt(rq, p, 0);
2351                         resched_curr(rq);
2352                         return;
2353                 }
2354         }
2355 }
2356 
2357 static void set_curr_task_rt(struct rq *rq)
2358 {
2359         set_next_task(rq, rq->curr);
2360 }
2361 
2362 static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
2363 {
2364         /*
2365          * Time slice is 0 for SCHED_FIFO tasks
2366          */
2367         if (task->policy == SCHED_RR)
2368                 return sched_rr_timeslice;
2369         else
2370                 return 0;
2371 }
2372 
2373 const struct sched_class rt_sched_class = {
2374         .next                   = &fair_sched_class,
2375         .enqueue_task           = enqueue_task_rt,
2376         .dequeue_task           = dequeue_task_rt,
2377         .yield_task             = yield_task_rt,
2378 
2379         .check_preempt_curr     = check_preempt_curr_rt,
2380 
2381         .pick_next_task         = pick_next_task_rt,
2382         .put_prev_task          = put_prev_task_rt,
2383 
2384 #ifdef CONFIG_SMP
2385         .select_task_rq         = select_task_rq_rt,
2386 
2387         .set_cpus_allowed       = set_cpus_allowed_common,
2388         .rq_online              = rq_online_rt,
2389         .rq_offline             = rq_offline_rt,
2390         .task_woken             = task_woken_rt,
2391         .switched_from          = switched_from_rt,
2392 #endif
2393 
2394         .set_curr_task          = set_curr_task_rt,
2395         .task_tick              = task_tick_rt,
2396 
2397         .get_rr_interval        = get_rr_interval_rt,
2398 
2399         .prio_changed           = prio_changed_rt,
2400         .switched_to            = switched_to_rt,
2401 
2402         .update_curr            = update_curr_rt,
2403 
2404 #ifdef CONFIG_UCLAMP_TASK
2405         .uclamp_enabled         = 1,
2406 #endif
2407 };
2408 
2409 #ifdef CONFIG_RT_GROUP_SCHED
2410 /*
2411  * Ensure that the real time constraints are schedulable.
2412  */
2413 static DEFINE_MUTEX(rt_constraints_mutex);
2414 
2415 /* Must be called with tasklist_lock held */
2416 static inline int tg_has_rt_tasks(struct task_group *tg)
2417 {
2418         struct task_struct *g, *p;
2419 
2420         /*
2421          * Autogroups do not have RT tasks; see autogroup_create().
2422          */
2423         if (task_group_is_autogroup(tg))
2424                 return 0;
2425 
2426         for_each_process_thread(g, p) {
2427                 if (rt_task(p) && task_group(p) == tg)
2428                         return 1;
2429         }
2430 
2431         return 0;
2432 }
2433 
2434 struct rt_schedulable_data {
2435         struct task_group *tg;
2436         u64 rt_period;
2437         u64 rt_runtime;
2438 };
2439 
2440 static int tg_rt_schedulable(struct task_group *tg, void *data)
2441 {
2442         struct rt_schedulable_data *d = data;
2443         struct task_group *child;
2444         unsigned long total, sum = 0;
2445         u64 period, runtime;
2446 
2447         period = ktime_to_ns(tg->rt_bandwidth.rt_period);
2448         runtime = tg->rt_bandwidth.rt_runtime;
2449 
2450         if (tg == d->tg) {
2451                 period = d->rt_period;
2452                 runtime = d->rt_runtime;
2453         }
2454 
2455         /*
2456          * Cannot have more runtime than the period.
2457          */
2458         if (runtime > period && runtime != RUNTIME_INF)
2459                 return -EINVAL;
2460 
2461         /*
2462          * Ensure we don't starve existing RT tasks.
2463          */
2464         if (rt_bandwidth_enabled() && !runtime && tg_has_rt_tasks(tg))
2465                 return -EBUSY;
2466 
2467         total = to_ratio(period, runtime);
2468 
2469         /*
2470          * Nobody can have more than the global setting allows.
2471          */
2472         if (total > to_ratio(global_rt_period(), global_rt_runtime()))
2473                 return -EINVAL;
2474 
2475         /*
2476          * The sum of our children's runtime should not exceed our own.
2477          */
2478         list_for_each_entry_rcu(child, &tg->children, siblings) {
2479                 period = ktime_to_ns(child->rt_bandwidth.rt_period);
2480                 runtime = child->rt_bandwidth.rt_runtime;
2481 
2482                 if (child == d->tg) {
2483                         period = d->rt_period;
2484                         runtime = d->rt_runtime;
2485                 }
2486 
2487                 sum += to_ratio(period, runtime);
2488         }
2489 
2490         if (sum > total)
2491                 return -EINVAL;
2492 
2493         return 0;
2494 }
2495 
2496 static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
2497 {
2498         int ret;
2499 
2500         struct rt_schedulable_data data = {
2501                 .tg = tg,
2502                 .rt_period = period,
2503                 .rt_runtime = runtime,
2504         };
2505 
2506         rcu_read_lock();
2507         ret = walk_tg_tree(tg_rt_schedulable, tg_nop, &data);
2508         rcu_read_unlock();
2509 
2510         return ret;
2511 }
2512 
2513 static int tg_set_rt_bandwidth(struct task_group *tg,
2514                 u64 rt_period, u64 rt_runtime)
2515 {
2516         int i, err = 0;
2517 
2518         /*
2519          * Disallowing the root group RT runtime is BAD, it would disallow the
2520          * kernel creating (and or operating) RT threads.
2521          */
2522         if (tg == &root_task_group && rt_runtime == 0)
2523                 return -EINVAL;
2524 
2525         /* No period doesn't make any sense. */
2526         if (rt_period == 0)
2527                 return -EINVAL;
2528 
2529         mutex_lock(&rt_constraints_mutex);
2530         read_lock(&tasklist_lock);
2531         err = __rt_schedulable(tg, rt_period, rt_runtime);
2532         if (err)
2533                 goto unlock;
2534 
2535         raw_spin_lock_irq(&tg->rt_bandwidth.rt_runtime_lock);
2536         tg->rt_bandwidth.rt_period = ns_to_ktime(rt_period);
2537         tg->rt_bandwidth.rt_runtime = rt_runtime;
2538 
2539         for_each_possible_cpu(i) {
2540                 struct rt_rq *rt_rq = tg->rt_rq[i];
2541 
2542                 raw_spin_lock(&rt_rq->rt_runtime_lock);
2543                 rt_rq->rt_runtime = rt_runtime;
2544                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
2545         }
2546         raw_spin_unlock_irq(&tg->rt_bandwidth.rt_runtime_lock);
2547 unlock:
2548         read_unlock(&tasklist_lock);
2549         mutex_unlock(&rt_constraints_mutex);
2550 
2551         return err;
2552 }
2553 
2554 int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)
2555 {
2556         u64 rt_runtime, rt_period;
2557 
2558         rt_period = ktime_to_ns(tg->rt_bandwidth.rt_period);
2559         rt_runtime = (u64)rt_runtime_us * NSEC_PER_USEC;
2560         if (rt_runtime_us < 0)
2561                 rt_runtime = RUNTIME_INF;
2562         else if ((u64)rt_runtime_us > U64_MAX / NSEC_PER_USEC)
2563                 return -EINVAL;
2564 
2565         return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
2566 }
2567 
2568 long sched_group_rt_runtime(struct task_group *tg)
2569 {
2570         u64 rt_runtime_us;
2571 
2572         if (tg->rt_bandwidth.rt_runtime == RUNTIME_INF)
2573                 return -1;
2574 
2575         rt_runtime_us = tg->rt_bandwidth.rt_runtime;
2576         do_div(rt_runtime_us, NSEC_PER_USEC);
2577         return rt_runtime_us;
2578 }
2579 
2580 int sched_group_set_rt_period(struct task_group *tg, u64 rt_period_us)
2581 {
2582         u64 rt_runtime, rt_period;
2583 
2584         if (rt_period_us > U64_MAX / NSEC_PER_USEC)
2585                 return -EINVAL;
2586 
2587         rt_period = rt_period_us * NSEC_PER_USEC;
2588         rt_runtime = tg->rt_bandwidth.rt_runtime;
2589 
2590         return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
2591 }
2592 
2593 long sched_group_rt_period(struct task_group *tg)
2594 {
2595         u64 rt_period_us;
2596 
2597         rt_period_us = ktime_to_ns(tg->rt_bandwidth.rt_period);
2598         do_div(rt_period_us, NSEC_PER_USEC);
2599         return rt_period_us;
2600 }
2601 
2602 static int sched_rt_global_constraints(void)
2603 {
2604         int ret = 0;
2605 
2606         mutex_lock(&rt_constraints_mutex);
2607         read_lock(&tasklist_lock);
2608         ret = __rt_schedulable(NULL, 0, 0);
2609         read_unlock(&tasklist_lock);
2610         mutex_unlock(&rt_constraints_mutex);
2611 
2612         return ret;
2613 }
2614 
2615 int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
2616 {
2617         /* Don't accept realtime tasks when there is no way for them to run */
2618         if (rt_task(tsk) && tg->rt_bandwidth.rt_runtime == 0)
2619                 return 0;
2620 
2621         return 1;
2622 }
2623 
2624 #else /* !CONFIG_RT_GROUP_SCHED */
2625 static int sched_rt_global_constraints(void)
2626 {
2627         unsigned long flags;
2628         int i;
2629 
2630         raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
2631         for_each_possible_cpu(i) {
2632                 struct rt_rq *rt_rq = &cpu_rq(i)->rt;
2633 
2634                 raw_spin_lock(&rt_rq->rt_runtime_lock);
2635                 rt_rq->rt_runtime = global_rt_runtime();
2636                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
2637         }
2638         raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
2639 
2640         return 0;
2641 }
2642 #endif /* CONFIG_RT_GROUP_SCHED */
2643 
2644 static int sched_rt_global_validate(void)
2645 {
2646         if (sysctl_sched_rt_period <= 0)
2647                 return -EINVAL;
2648 
2649         if ((sysctl_sched_rt_runtime != RUNTIME_INF) &&
2650                 (sysctl_sched_rt_runtime > sysctl_sched_rt_period))
2651                 return -EINVAL;
2652 
2653         return 0;
2654 }
2655 
2656 static void sched_rt_do_global(void)
2657 {
2658         def_rt_bandwidth.rt_runtime = global_rt_runtime();
2659         def_rt_bandwidth.rt_period = ns_to_ktime(global_rt_period());
2660 }
2661 
2662 int sched_rt_handler(struct ctl_table *table, int write,
2663                 void __user *buffer, size_t *lenp,
2664                 loff_t *ppos)
2665 {
2666         int old_period, old_runtime;
2667         static DEFINE_MUTEX(mutex);
2668         int ret;
2669 
2670         mutex_lock(&mutex);
2671         old_period = sysctl_sched_rt_period;
2672         old_runtime = sysctl_sched_rt_runtime;
2673 
2674         ret = proc_dointvec(table, write, buffer, lenp, ppos);
2675 
2676         if (!ret && write) {
2677                 ret = sched_rt_global_validate();
2678                 if (ret)
2679                         goto undo;
2680 
2681                 ret = sched_dl_global_validate();
2682                 if (ret)
2683                         goto undo;
2684 
2685                 ret = sched_rt_global_constraints();
2686                 if (ret)
2687                         goto undo;
2688 
2689                 sched_rt_do_global();
2690                 sched_dl_do_global();
2691         }
2692         if (0) {
2693 undo:
2694                 sysctl_sched_rt_period = old_period;
2695                 sysctl_sched_rt_runtime = old_runtime;
2696         }
2697         mutex_unlock(&mutex);
2698 
2699         return ret;
2700 }
2701 
2702 int sched_rr_handler(struct ctl_table *table, int write,
2703                 void __user *buffer, size_t *lenp,
2704                 loff_t *ppos)
2705 {
2706         int ret;
2707         static DEFINE_MUTEX(mutex);
2708 
2709         mutex_lock(&mutex);
2710         ret = proc_dointvec(table, write, buffer, lenp, ppos);
2711         /*
2712          * Make sure that internally we keep jiffies.
2713          * Also, writing zero resets the timeslice to default:
2714          */
2715         if (!ret && write) {
2716                 sched_rr_timeslice =
2717                         sysctl_sched_rr_timeslice <= 0 ? RR_TIMESLICE :
2718                         msecs_to_jiffies(sysctl_sched_rr_timeslice);
2719         }
2720         mutex_unlock(&mutex);
2721 
2722         return ret;
2723 }
2724 
2725 #ifdef CONFIG_SCHED_DEBUG
2726 void print_rt_stats(struct seq_file *m, int cpu)
2727 {
2728         rt_rq_iter_t iter;
2729         struct rt_rq *rt_rq;
2730 
2731         rcu_read_lock();
2732         for_each_rt_rq(rt_rq, iter, cpu_rq(cpu))
2733                 print_rt_rq(m, cpu, rt_rq);
2734         rcu_read_unlock();
2735 }
2736 #endif /* CONFIG_SCHED_DEBUG */
2737 

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