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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
10int sched_rr_timeslice = RR_TIMESLICE;
11int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;
12
13static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);
14
15struct rt_bandwidth def_rt_bandwidth;
16
17static 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
41void 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
53static 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
76void 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
106static 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
113static 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
121static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
122{
123 return rt_rq->rq;
124}
125
126static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
127{
128 return rt_se->rt_rq;
129}
130
131static 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
138void 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
156void 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
183int 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
217err_free_rq:
218 kfree(rt_rq);
219err:
220 return 0;
221}
222
223#else /* CONFIG_RT_GROUP_SCHED */
224
225#define rt_entity_is_task(rt_se) (1)
226
227static 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
232static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
233{
234 return container_of(rt_rq, struct rq, rt);
235}
236
237static 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
244static 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
251void free_rt_sched_group(struct task_group *tg) { }
252
253int 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
261static void pull_rt_task(struct rq *this_rq);
262
263static 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
269static inline int rt_overloaded(struct rq *rq)
270{
271 return atomic_read(&rq->rd->rto_count);
272}
273
274static 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
293static 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
303static 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
316static 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
333static 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
350static inline int has_pushable_tasks(struct rq *rq)
351{
352 return !plist_head_empty(&rq->rt.pushable_tasks);
353}
354
355static DEFINE_PER_CPU(struct callback_head, rt_push_head);
356static DEFINE_PER_CPU(struct callback_head, rt_pull_head);
357
358static void push_rt_tasks(struct rq *);
359static void pull_rt_task(struct rq *);
360
361static 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
369static 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
374static 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
385static 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
400static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
401{
402}
403
404static inline void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
405{
406}
407
408static inline
409void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
410{
411}
412
413static inline
414void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
415{
416}
417
418static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
419{
420 return false;
421}
422
423static inline void pull_rt_task(struct rq *this_rq)
424{
425}
426
427static inline void rt_queue_push_tasks(struct rq *rq)
428{
429}
430#endif /* CONFIG_SMP */
431
432static void enqueue_top_rt_rq(struct rt_rq *rt_rq);
433static void dequeue_top_rt_rq(struct rt_rq *rt_rq);
434
435static 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
442static 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
450static 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
455typedef struct task_group *rt_rq_iter_t;
456
457static 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
478static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
479{
480 return rt_se->my_q;
481}
482
483static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags);
484static void dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags);
485
486static 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
507static 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
523static inline int rt_rq_throttled(struct rt_rq *rt_rq)
524{
525 return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
526}
527
528static 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
541static inline const struct cpumask *sched_rt_period_mask(void)
542{
543 return this_rq()->rd->span;
544}
545#else
546static inline const struct cpumask *sched_rt_period_mask(void)
547{
548 return cpu_online_mask;
549}
550#endif
551
552static inline
553struct 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
558static 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
565static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
566{
567 return rt_rq->rt_runtime;
568}
569
570static inline u64 sched_rt_period(struct rt_rq *rt_rq)
571{
572 return ktime_to_ns(def_rt_bandwidth.rt_period);
573}
574
575typedef 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
583static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
584{
585 return NULL;
586}
587
588static 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
599static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
600{
601 dequeue_top_rt_rq(rt_rq);
602}
603
604static inline int rt_rq_throttled(struct rt_rq *rt_rq)
605{
606 return rt_rq->rt_throttled;
607}
608
609static inline const struct cpumask *sched_rt_period_mask(void)
610{
611 return cpu_online_mask;
612}
613
614static inline
615struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
616{
617 return &cpu_rq(cpu)->rt;
618}
619
620static 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
627bool 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 */
639static 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 }
682next:
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 */
691static 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);
758balanced:
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
773static 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
797static 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 */
809static inline void balance_runtime(struct rt_rq *rt_rq) {}
810#endif /* CONFIG_SMP */
811
812static 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
896static 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
908static 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 */
955static 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
995static void
996dequeue_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
1012static void
1013enqueue_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
1036static void
1037inc_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
1052static void
1053dec_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
1070static inline
1071void inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
1072static inline
1073void 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
1078static void
1079inc_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
1089static void
1090dec_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
1117static inline void inc_rt_prio(struct rt_rq *rt_rq, int prio) {}
1118static 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
1124static void
1125inc_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
1134static void
1135dec_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
1145static void
1146inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1147{
1148 start_rt_bandwidth(&def_rt_bandwidth);
1149}
1150
1151static inline
1152void dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) {}
1153
1154#endif /* CONFIG_RT_GROUP_SCHED */
1155
1156static inline
1157unsigned 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
1167static inline
1168unsigned 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
1181static inline
1182void 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
1195static inline
1196void 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 */
1213static 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
1221static 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
1231static 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
1265static 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 */
1283static 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
1300static 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
1310static 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 */
1328static void
1329enqueue_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
1342static 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 */
1356static void
1357requeue_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
1370static 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
1381static void yield_task_rt(struct rq *rq)
1382{
1383 requeue_task_rt(rq, rq->curr, 0);
1384}
1385
1386#ifdef CONFIG_SMP
1387static int find_lowest_rq(struct task_struct *task);
1388
1389static int
1390select_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
1441out:
1442 return cpu;
1443}
1444
1445static 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
1472static 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 */
1493static 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
1518static inline void set_next_task_rt(struct rq *rq, struct task_struct *p)
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 /*
1526 * If prev task was rt, put_prev_task() has already updated the
1527 * utilization. We only care of the case where we start to schedule a
1528 * rt task
1529 */
1530 if (rq->curr->sched_class != &rt_sched_class)
1531 update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0);
1532
1533 rt_queue_push_tasks(rq);
1534}
1535
1536static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
1537 struct rt_rq *rt_rq)
1538{
1539 struct rt_prio_array *array = &rt_rq->active;
1540 struct sched_rt_entity *next = NULL;
1541 struct list_head *queue;
1542 int idx;
1543
1544 idx = sched_find_first_bit(array->bitmap);
1545 BUG_ON(idx >= MAX_RT_PRIO);
1546
1547 queue = array->queue + idx;
1548 next = list_entry(queue->next, struct sched_rt_entity, run_list);
1549
1550 return next;
1551}
1552
1553static struct task_struct *_pick_next_task_rt(struct rq *rq)
1554{
1555 struct sched_rt_entity *rt_se;
1556 struct rt_rq *rt_rq = &rq->rt;
1557
1558 do {
1559 rt_se = pick_next_rt_entity(rq, rt_rq);
1560 BUG_ON(!rt_se);
1561 rt_rq = group_rt_rq(rt_se);
1562 } while (rt_rq);
1563
1564 return rt_task_of(rt_se);
1565}
1566
1567static struct task_struct *
1568pick_next_task_rt(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
1569{
1570 struct task_struct *p;
1571
1572 WARN_ON_ONCE(prev || rf);
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);
1579 return p;
1580}
1581
1582static 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
1601static 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 */
1614static 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
1630static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
1631
1632static 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 */
1708static 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
1764static 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 */
1789static 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
1802retry:
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
1863out:
1864 put_task_struct(next_task);
1865
1866 return ret;
1867}
1868
1869static 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 */
1919static 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
1966static inline bool rto_start_trylock(atomic_t *v)
1967{
1968 return !atomic_cmpxchg_acquire(v, 0, 1);
1969}
1970
1971static inline void rto_start_unlock(atomic_t *v)
1972{
1973 atomic_set_release(v, 0);
1974}
1975
1976static 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 */
2010void 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
2046static 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 }
2136skip:
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 */
2148static 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 */
2160static 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 */
2171static 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 */
2185static 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
2200void __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 */
2216static 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 */
2239static void
2240prio_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
2277static 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
2301static 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 */
2312static 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
2346static 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
2357const 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 */
2397static DEFINE_MUTEX(rt_constraints_mutex);
2398
2399/* Must be called with tasklist_lock held */
2400static 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
2418struct rt_schedulable_data {
2419 struct task_group *tg;
2420 u64 rt_period;
2421 u64 rt_runtime;
2422};
2423
2424static 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
2480static 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
2497static 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);
2531unlock:
2532 read_unlock(&tasklist_lock);
2533 mutex_unlock(&rt_constraints_mutex);
2534
2535 return err;
2536}
2537
2538int 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
2552long 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
2564int 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
2577long 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
2586static 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
2599int 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 */
2609static 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
2628static 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
2640static 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
2646int 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) {
2677undo:
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
2686int 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
2710void 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 */