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

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