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