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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
7int sched_rr_timeslice = RR_TIMESLICE;
8/* More than 4 hours if BW_SHIFT equals 20. */
9static const u64 max_rt_runtime = MAX_BW;
10
11/*
12 * period over which we measure -rt task CPU usage in us.
13 * default: 1s
14 */
15int sysctl_sched_rt_period = 1000000;
16
17/*
18 * part of the period that we allow rt tasks to run in us.
19 * default: 0.95s
20 */
21int sysctl_sched_rt_runtime = 950000;
22
23#ifdef CONFIG_SYSCTL
24static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC * RR_TIMESLICE) / HZ;
25static int sched_rt_handler(const struct ctl_table *table, int write, void *buffer,
26 size_t *lenp, loff_t *ppos);
27static int sched_rr_handler(const struct ctl_table *table, int write, void *buffer,
28 size_t *lenp, loff_t *ppos);
29static struct ctl_table sched_rt_sysctls[] = {
30 {
31 .procname = "sched_rt_period_us",
32 .data = &sysctl_sched_rt_period,
33 .maxlen = sizeof(int),
34 .mode = 0644,
35 .proc_handler = sched_rt_handler,
36 .extra1 = SYSCTL_ONE,
37 .extra2 = SYSCTL_INT_MAX,
38 },
39 {
40 .procname = "sched_rt_runtime_us",
41 .data = &sysctl_sched_rt_runtime,
42 .maxlen = sizeof(int),
43 .mode = 0644,
44 .proc_handler = sched_rt_handler,
45 .extra1 = SYSCTL_NEG_ONE,
46 .extra2 = (void *)&sysctl_sched_rt_period,
47 },
48 {
49 .procname = "sched_rr_timeslice_ms",
50 .data = &sysctl_sched_rr_timeslice,
51 .maxlen = sizeof(int),
52 .mode = 0644,
53 .proc_handler = sched_rr_handler,
54 },
55};
56
57static int __init sched_rt_sysctl_init(void)
58{
59 register_sysctl_init("kernel", sched_rt_sysctls);
60 return 0;
61}
62late_initcall(sched_rt_sysctl_init);
63#endif
64
65void init_rt_rq(struct rt_rq *rt_rq)
66{
67 struct rt_prio_array *array;
68 int i;
69
70 array = &rt_rq->active;
71 for (i = 0; i < MAX_RT_PRIO; i++) {
72 INIT_LIST_HEAD(array->queue + i);
73 __clear_bit(i, array->bitmap);
74 }
75 /* delimiter for bitsearch: */
76 __set_bit(MAX_RT_PRIO, array->bitmap);
77
78#if defined CONFIG_SMP
79 rt_rq->highest_prio.curr = MAX_RT_PRIO-1;
80 rt_rq->highest_prio.next = MAX_RT_PRIO-1;
81 rt_rq->overloaded = 0;
82 plist_head_init(&rt_rq->pushable_tasks);
83#endif /* CONFIG_SMP */
84 /* We start is dequeued state, because no RT tasks are queued */
85 rt_rq->rt_queued = 0;
86
87#ifdef CONFIG_RT_GROUP_SCHED
88 rt_rq->rt_time = 0;
89 rt_rq->rt_throttled = 0;
90 rt_rq->rt_runtime = 0;
91 raw_spin_lock_init(&rt_rq->rt_runtime_lock);
92#endif
93}
94
95#ifdef CONFIG_RT_GROUP_SCHED
96
97static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);
98
99static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer)
100{
101 struct rt_bandwidth *rt_b =
102 container_of(timer, struct rt_bandwidth, rt_period_timer);
103 int idle = 0;
104 int overrun;
105
106 raw_spin_lock(&rt_b->rt_runtime_lock);
107 for (;;) {
108 overrun = hrtimer_forward_now(timer, rt_b->rt_period);
109 if (!overrun)
110 break;
111
112 raw_spin_unlock(&rt_b->rt_runtime_lock);
113 idle = do_sched_rt_period_timer(rt_b, overrun);
114 raw_spin_lock(&rt_b->rt_runtime_lock);
115 }
116 if (idle)
117 rt_b->rt_period_active = 0;
118 raw_spin_unlock(&rt_b->rt_runtime_lock);
119
120 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
121}
122
123void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime)
124{
125 rt_b->rt_period = ns_to_ktime(period);
126 rt_b->rt_runtime = runtime;
127
128 raw_spin_lock_init(&rt_b->rt_runtime_lock);
129
130 hrtimer_init(&rt_b->rt_period_timer, CLOCK_MONOTONIC,
131 HRTIMER_MODE_REL_HARD);
132 rt_b->rt_period_timer.function = sched_rt_period_timer;
133}
134
135static inline void do_start_rt_bandwidth(struct rt_bandwidth *rt_b)
136{
137 raw_spin_lock(&rt_b->rt_runtime_lock);
138 if (!rt_b->rt_period_active) {
139 rt_b->rt_period_active = 1;
140 /*
141 * SCHED_DEADLINE updates the bandwidth, as a run away
142 * RT task with a DL task could hog a CPU. But DL does
143 * not reset the period. If a deadline task was running
144 * without an RT task running, it can cause RT tasks to
145 * throttle when they start up. Kick the timer right away
146 * to update the period.
147 */
148 hrtimer_forward_now(&rt_b->rt_period_timer, ns_to_ktime(0));
149 hrtimer_start_expires(&rt_b->rt_period_timer,
150 HRTIMER_MODE_ABS_PINNED_HARD);
151 }
152 raw_spin_unlock(&rt_b->rt_runtime_lock);
153}
154
155static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
156{
157 if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
158 return;
159
160 do_start_rt_bandwidth(rt_b);
161}
162
163static void destroy_rt_bandwidth(struct rt_bandwidth *rt_b)
164{
165 hrtimer_cancel(&rt_b->rt_period_timer);
166}
167
168#define rt_entity_is_task(rt_se) (!(rt_se)->my_q)
169
170static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
171{
172#ifdef CONFIG_SCHED_DEBUG
173 WARN_ON_ONCE(!rt_entity_is_task(rt_se));
174#endif
175 return container_of(rt_se, struct task_struct, rt);
176}
177
178static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
179{
180 return rt_rq->rq;
181}
182
183static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
184{
185 return rt_se->rt_rq;
186}
187
188static inline struct rq *rq_of_rt_se(struct sched_rt_entity *rt_se)
189{
190 struct rt_rq *rt_rq = rt_se->rt_rq;
191
192 return rt_rq->rq;
193}
194
195void unregister_rt_sched_group(struct task_group *tg)
196{
197 if (tg->rt_se)
198 destroy_rt_bandwidth(&tg->rt_bandwidth);
199}
200
201void free_rt_sched_group(struct task_group *tg)
202{
203 int i;
204
205 for_each_possible_cpu(i) {
206 if (tg->rt_rq)
207 kfree(tg->rt_rq[i]);
208 if (tg->rt_se)
209 kfree(tg->rt_se[i]);
210 }
211
212 kfree(tg->rt_rq);
213 kfree(tg->rt_se);
214}
215
216void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
217 struct sched_rt_entity *rt_se, int cpu,
218 struct sched_rt_entity *parent)
219{
220 struct rq *rq = cpu_rq(cpu);
221
222 rt_rq->highest_prio.curr = MAX_RT_PRIO-1;
223 rt_rq->rt_nr_boosted = 0;
224 rt_rq->rq = rq;
225 rt_rq->tg = tg;
226
227 tg->rt_rq[cpu] = rt_rq;
228 tg->rt_se[cpu] = rt_se;
229
230 if (!rt_se)
231 return;
232
233 if (!parent)
234 rt_se->rt_rq = &rq->rt;
235 else
236 rt_se->rt_rq = parent->my_q;
237
238 rt_se->my_q = rt_rq;
239 rt_se->parent = parent;
240 INIT_LIST_HEAD(&rt_se->run_list);
241}
242
243int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
244{
245 struct rt_rq *rt_rq;
246 struct sched_rt_entity *rt_se;
247 int i;
248
249 tg->rt_rq = kcalloc(nr_cpu_ids, sizeof(rt_rq), GFP_KERNEL);
250 if (!tg->rt_rq)
251 goto err;
252 tg->rt_se = kcalloc(nr_cpu_ids, sizeof(rt_se), GFP_KERNEL);
253 if (!tg->rt_se)
254 goto err;
255
256 init_rt_bandwidth(&tg->rt_bandwidth, ktime_to_ns(global_rt_period()), 0);
257
258 for_each_possible_cpu(i) {
259 rt_rq = kzalloc_node(sizeof(struct rt_rq),
260 GFP_KERNEL, cpu_to_node(i));
261 if (!rt_rq)
262 goto err;
263
264 rt_se = kzalloc_node(sizeof(struct sched_rt_entity),
265 GFP_KERNEL, cpu_to_node(i));
266 if (!rt_se)
267 goto err_free_rq;
268
269 init_rt_rq(rt_rq);
270 rt_rq->rt_runtime = tg->rt_bandwidth.rt_runtime;
271 init_tg_rt_entry(tg, rt_rq, rt_se, i, parent->rt_se[i]);
272 }
273
274 return 1;
275
276err_free_rq:
277 kfree(rt_rq);
278err:
279 return 0;
280}
281
282#else /* CONFIG_RT_GROUP_SCHED */
283
284#define rt_entity_is_task(rt_se) (1)
285
286static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
287{
288 return container_of(rt_se, struct task_struct, rt);
289}
290
291static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
292{
293 return container_of(rt_rq, struct rq, rt);
294}
295
296static inline struct rq *rq_of_rt_se(struct sched_rt_entity *rt_se)
297{
298 struct task_struct *p = rt_task_of(rt_se);
299
300 return task_rq(p);
301}
302
303static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
304{
305 struct rq *rq = rq_of_rt_se(rt_se);
306
307 return &rq->rt;
308}
309
310void unregister_rt_sched_group(struct task_group *tg) { }
311
312void free_rt_sched_group(struct task_group *tg) { }
313
314int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
315{
316 return 1;
317}
318#endif /* CONFIG_RT_GROUP_SCHED */
319
320#ifdef CONFIG_SMP
321
322static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
323{
324 /* Try to pull RT tasks here if we lower this rq's prio */
325 return rq->online && rq->rt.highest_prio.curr > prev->prio;
326}
327
328static inline int rt_overloaded(struct rq *rq)
329{
330 return atomic_read(&rq->rd->rto_count);
331}
332
333static inline void rt_set_overload(struct rq *rq)
334{
335 if (!rq->online)
336 return;
337
338 cpumask_set_cpu(rq->cpu, rq->rd->rto_mask);
339 /*
340 * Make sure the mask is visible before we set
341 * the overload count. That is checked to determine
342 * if we should look at the mask. It would be a shame
343 * if we looked at the mask, but the mask was not
344 * updated yet.
345 *
346 * Matched by the barrier in pull_rt_task().
347 */
348 smp_wmb();
349 atomic_inc(&rq->rd->rto_count);
350}
351
352static inline void rt_clear_overload(struct rq *rq)
353{
354 if (!rq->online)
355 return;
356
357 /* the order here really doesn't matter */
358 atomic_dec(&rq->rd->rto_count);
359 cpumask_clear_cpu(rq->cpu, rq->rd->rto_mask);
360}
361
362static inline int has_pushable_tasks(struct rq *rq)
363{
364 return !plist_head_empty(&rq->rt.pushable_tasks);
365}
366
367static DEFINE_PER_CPU(struct balance_callback, rt_push_head);
368static DEFINE_PER_CPU(struct balance_callback, rt_pull_head);
369
370static void push_rt_tasks(struct rq *);
371static void pull_rt_task(struct rq *);
372
373static inline void rt_queue_push_tasks(struct rq *rq)
374{
375 if (!has_pushable_tasks(rq))
376 return;
377
378 queue_balance_callback(rq, &per_cpu(rt_push_head, rq->cpu), push_rt_tasks);
379}
380
381static inline void rt_queue_pull_task(struct rq *rq)
382{
383 queue_balance_callback(rq, &per_cpu(rt_pull_head, rq->cpu), pull_rt_task);
384}
385
386static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
387{
388 plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
389 plist_node_init(&p->pushable_tasks, p->prio);
390 plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks);
391
392 /* Update the highest prio pushable task */
393 if (p->prio < rq->rt.highest_prio.next)
394 rq->rt.highest_prio.next = p->prio;
395
396 if (!rq->rt.overloaded) {
397 rt_set_overload(rq);
398 rq->rt.overloaded = 1;
399 }
400}
401
402static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
403{
404 plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
405
406 /* Update the new highest prio pushable task */
407 if (has_pushable_tasks(rq)) {
408 p = plist_first_entry(&rq->rt.pushable_tasks,
409 struct task_struct, pushable_tasks);
410 rq->rt.highest_prio.next = p->prio;
411 } else {
412 rq->rt.highest_prio.next = MAX_RT_PRIO-1;
413
414 if (rq->rt.overloaded) {
415 rt_clear_overload(rq);
416 rq->rt.overloaded = 0;
417 }
418 }
419}
420
421#else
422
423static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
424{
425}
426
427static inline void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
428{
429}
430
431static inline void rt_queue_push_tasks(struct rq *rq)
432{
433}
434#endif /* CONFIG_SMP */
435
436static void enqueue_top_rt_rq(struct rt_rq *rt_rq);
437static void dequeue_top_rt_rq(struct rt_rq *rt_rq, unsigned int count);
438
439static inline int on_rt_rq(struct sched_rt_entity *rt_se)
440{
441 return rt_se->on_rq;
442}
443
444#ifdef CONFIG_UCLAMP_TASK
445/*
446 * Verify the fitness of task @p to run on @cpu taking into account the uclamp
447 * settings.
448 *
449 * This check is only important for heterogeneous systems where uclamp_min value
450 * is higher than the capacity of a @cpu. For non-heterogeneous system this
451 * function will always return true.
452 *
453 * The function will return true if the capacity of the @cpu is >= the
454 * uclamp_min and false otherwise.
455 *
456 * Note that uclamp_min will be clamped to uclamp_max if uclamp_min
457 * > uclamp_max.
458 */
459static inline bool rt_task_fits_capacity(struct task_struct *p, int cpu)
460{
461 unsigned int min_cap;
462 unsigned int max_cap;
463 unsigned int cpu_cap;
464
465 /* Only heterogeneous systems can benefit from this check */
466 if (!sched_asym_cpucap_active())
467 return true;
468
469 min_cap = uclamp_eff_value(p, UCLAMP_MIN);
470 max_cap = uclamp_eff_value(p, UCLAMP_MAX);
471
472 cpu_cap = arch_scale_cpu_capacity(cpu);
473
474 return cpu_cap >= min(min_cap, max_cap);
475}
476#else
477static inline bool rt_task_fits_capacity(struct task_struct *p, int cpu)
478{
479 return true;
480}
481#endif
482
483#ifdef CONFIG_RT_GROUP_SCHED
484
485static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
486{
487 if (!rt_rq->tg)
488 return RUNTIME_INF;
489
490 return rt_rq->rt_runtime;
491}
492
493static inline u64 sched_rt_period(struct rt_rq *rt_rq)
494{
495 return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
496}
497
498typedef struct task_group *rt_rq_iter_t;
499
500static inline struct task_group *next_task_group(struct task_group *tg)
501{
502 do {
503 tg = list_entry_rcu(tg->list.next,
504 typeof(struct task_group), list);
505 } while (&tg->list != &task_groups && task_group_is_autogroup(tg));
506
507 if (&tg->list == &task_groups)
508 tg = NULL;
509
510 return tg;
511}
512
513#define for_each_rt_rq(rt_rq, iter, rq) \
514 for (iter = container_of(&task_groups, typeof(*iter), list); \
515 (iter = next_task_group(iter)) && \
516 (rt_rq = iter->rt_rq[cpu_of(rq)]);)
517
518#define for_each_sched_rt_entity(rt_se) \
519 for (; rt_se; rt_se = rt_se->parent)
520
521static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
522{
523 return rt_se->my_q;
524}
525
526static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags);
527static void dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags);
528
529static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
530{
531 struct task_struct *donor = rq_of_rt_rq(rt_rq)->donor;
532 struct rq *rq = rq_of_rt_rq(rt_rq);
533 struct sched_rt_entity *rt_se;
534
535 int cpu = cpu_of(rq);
536
537 rt_se = rt_rq->tg->rt_se[cpu];
538
539 if (rt_rq->rt_nr_running) {
540 if (!rt_se)
541 enqueue_top_rt_rq(rt_rq);
542 else if (!on_rt_rq(rt_se))
543 enqueue_rt_entity(rt_se, 0);
544
545 if (rt_rq->highest_prio.curr < donor->prio)
546 resched_curr(rq);
547 }
548}
549
550static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
551{
552 struct sched_rt_entity *rt_se;
553 int cpu = cpu_of(rq_of_rt_rq(rt_rq));
554
555 rt_se = rt_rq->tg->rt_se[cpu];
556
557 if (!rt_se) {
558 dequeue_top_rt_rq(rt_rq, rt_rq->rt_nr_running);
559 /* Kick cpufreq (see the comment in kernel/sched/sched.h). */
560 cpufreq_update_util(rq_of_rt_rq(rt_rq), 0);
561 }
562 else if (on_rt_rq(rt_se))
563 dequeue_rt_entity(rt_se, 0);
564}
565
566static inline int rt_rq_throttled(struct rt_rq *rt_rq)
567{
568 return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
569}
570
571static int rt_se_boosted(struct sched_rt_entity *rt_se)
572{
573 struct rt_rq *rt_rq = group_rt_rq(rt_se);
574 struct task_struct *p;
575
576 if (rt_rq)
577 return !!rt_rq->rt_nr_boosted;
578
579 p = rt_task_of(rt_se);
580 return p->prio != p->normal_prio;
581}
582
583#ifdef CONFIG_SMP
584static inline const struct cpumask *sched_rt_period_mask(void)
585{
586 return this_rq()->rd->span;
587}
588#else
589static inline const struct cpumask *sched_rt_period_mask(void)
590{
591 return cpu_online_mask;
592}
593#endif
594
595static inline
596struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
597{
598 return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
599}
600
601static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
602{
603 return &rt_rq->tg->rt_bandwidth;
604}
605
606bool sched_rt_bandwidth_account(struct rt_rq *rt_rq)
607{
608 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
609
610 return (hrtimer_active(&rt_b->rt_period_timer) ||
611 rt_rq->rt_time < rt_b->rt_runtime);
612}
613
614#ifdef CONFIG_SMP
615/*
616 * We ran out of runtime, see if we can borrow some from our neighbours.
617 */
618static void do_balance_runtime(struct rt_rq *rt_rq)
619{
620 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
621 struct root_domain *rd = rq_of_rt_rq(rt_rq)->rd;
622 int i, weight;
623 u64 rt_period;
624
625 weight = cpumask_weight(rd->span);
626
627 raw_spin_lock(&rt_b->rt_runtime_lock);
628 rt_period = ktime_to_ns(rt_b->rt_period);
629 for_each_cpu(i, rd->span) {
630 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
631 s64 diff;
632
633 if (iter == rt_rq)
634 continue;
635
636 raw_spin_lock(&iter->rt_runtime_lock);
637 /*
638 * Either all rqs have inf runtime and there's nothing to steal
639 * or __disable_runtime() below sets a specific rq to inf to
640 * indicate its been disabled and disallow stealing.
641 */
642 if (iter->rt_runtime == RUNTIME_INF)
643 goto next;
644
645 /*
646 * From runqueues with spare time, take 1/n part of their
647 * spare time, but no more than our period.
648 */
649 diff = iter->rt_runtime - iter->rt_time;
650 if (diff > 0) {
651 diff = div_u64((u64)diff, weight);
652 if (rt_rq->rt_runtime + diff > rt_period)
653 diff = rt_period - rt_rq->rt_runtime;
654 iter->rt_runtime -= diff;
655 rt_rq->rt_runtime += diff;
656 if (rt_rq->rt_runtime == rt_period) {
657 raw_spin_unlock(&iter->rt_runtime_lock);
658 break;
659 }
660 }
661next:
662 raw_spin_unlock(&iter->rt_runtime_lock);
663 }
664 raw_spin_unlock(&rt_b->rt_runtime_lock);
665}
666
667/*
668 * Ensure this RQ takes back all the runtime it lend to its neighbours.
669 */
670static void __disable_runtime(struct rq *rq)
671{
672 struct root_domain *rd = rq->rd;
673 rt_rq_iter_t iter;
674 struct rt_rq *rt_rq;
675
676 if (unlikely(!scheduler_running))
677 return;
678
679 for_each_rt_rq(rt_rq, iter, rq) {
680 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
681 s64 want;
682 int i;
683
684 raw_spin_lock(&rt_b->rt_runtime_lock);
685 raw_spin_lock(&rt_rq->rt_runtime_lock);
686 /*
687 * Either we're all inf and nobody needs to borrow, or we're
688 * already disabled and thus have nothing to do, or we have
689 * exactly the right amount of runtime to take out.
690 */
691 if (rt_rq->rt_runtime == RUNTIME_INF ||
692 rt_rq->rt_runtime == rt_b->rt_runtime)
693 goto balanced;
694 raw_spin_unlock(&rt_rq->rt_runtime_lock);
695
696 /*
697 * Calculate the difference between what we started out with
698 * and what we current have, that's the amount of runtime
699 * we lend and now have to reclaim.
700 */
701 want = rt_b->rt_runtime - rt_rq->rt_runtime;
702
703 /*
704 * Greedy reclaim, take back as much as we can.
705 */
706 for_each_cpu(i, rd->span) {
707 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
708 s64 diff;
709
710 /*
711 * Can't reclaim from ourselves or disabled runqueues.
712 */
713 if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
714 continue;
715
716 raw_spin_lock(&iter->rt_runtime_lock);
717 if (want > 0) {
718 diff = min_t(s64, iter->rt_runtime, want);
719 iter->rt_runtime -= diff;
720 want -= diff;
721 } else {
722 iter->rt_runtime -= want;
723 want -= want;
724 }
725 raw_spin_unlock(&iter->rt_runtime_lock);
726
727 if (!want)
728 break;
729 }
730
731 raw_spin_lock(&rt_rq->rt_runtime_lock);
732 /*
733 * We cannot be left wanting - that would mean some runtime
734 * leaked out of the system.
735 */
736 WARN_ON_ONCE(want);
737balanced:
738 /*
739 * Disable all the borrow logic by pretending we have inf
740 * runtime - in which case borrowing doesn't make sense.
741 */
742 rt_rq->rt_runtime = RUNTIME_INF;
743 rt_rq->rt_throttled = 0;
744 raw_spin_unlock(&rt_rq->rt_runtime_lock);
745 raw_spin_unlock(&rt_b->rt_runtime_lock);
746
747 /* Make rt_rq available for pick_next_task() */
748 sched_rt_rq_enqueue(rt_rq);
749 }
750}
751
752static void __enable_runtime(struct rq *rq)
753{
754 rt_rq_iter_t iter;
755 struct rt_rq *rt_rq;
756
757 if (unlikely(!scheduler_running))
758 return;
759
760 /*
761 * Reset each runqueue's bandwidth settings
762 */
763 for_each_rt_rq(rt_rq, iter, rq) {
764 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
765
766 raw_spin_lock(&rt_b->rt_runtime_lock);
767 raw_spin_lock(&rt_rq->rt_runtime_lock);
768 rt_rq->rt_runtime = rt_b->rt_runtime;
769 rt_rq->rt_time = 0;
770 rt_rq->rt_throttled = 0;
771 raw_spin_unlock(&rt_rq->rt_runtime_lock);
772 raw_spin_unlock(&rt_b->rt_runtime_lock);
773 }
774}
775
776static void balance_runtime(struct rt_rq *rt_rq)
777{
778 if (!sched_feat(RT_RUNTIME_SHARE))
779 return;
780
781 if (rt_rq->rt_time > rt_rq->rt_runtime) {
782 raw_spin_unlock(&rt_rq->rt_runtime_lock);
783 do_balance_runtime(rt_rq);
784 raw_spin_lock(&rt_rq->rt_runtime_lock);
785 }
786}
787#else /* !CONFIG_SMP */
788static inline void balance_runtime(struct rt_rq *rt_rq) {}
789#endif /* CONFIG_SMP */
790
791static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
792{
793 int i, idle = 1, throttled = 0;
794 const struct cpumask *span;
795
796 span = sched_rt_period_mask();
797
798 /*
799 * FIXME: isolated CPUs should really leave the root task group,
800 * whether they are isolcpus or were isolated via cpusets, lest
801 * the timer run on a CPU which does not service all runqueues,
802 * potentially leaving other CPUs indefinitely throttled. If
803 * isolation is really required, the user will turn the throttle
804 * off to kill the perturbations it causes anyway. Meanwhile,
805 * this maintains functionality for boot and/or troubleshooting.
806 */
807 if (rt_b == &root_task_group.rt_bandwidth)
808 span = cpu_online_mask;
809
810 for_each_cpu(i, span) {
811 int enqueue = 0;
812 struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
813 struct rq *rq = rq_of_rt_rq(rt_rq);
814 struct rq_flags rf;
815 int skip;
816
817 /*
818 * When span == cpu_online_mask, taking each rq->lock
819 * can be time-consuming. Try to avoid it when possible.
820 */
821 raw_spin_lock(&rt_rq->rt_runtime_lock);
822 if (!sched_feat(RT_RUNTIME_SHARE) && rt_rq->rt_runtime != RUNTIME_INF)
823 rt_rq->rt_runtime = rt_b->rt_runtime;
824 skip = !rt_rq->rt_time && !rt_rq->rt_nr_running;
825 raw_spin_unlock(&rt_rq->rt_runtime_lock);
826 if (skip)
827 continue;
828
829 rq_lock(rq, &rf);
830 update_rq_clock(rq);
831
832 if (rt_rq->rt_time) {
833 u64 runtime;
834
835 raw_spin_lock(&rt_rq->rt_runtime_lock);
836 if (rt_rq->rt_throttled)
837 balance_runtime(rt_rq);
838 runtime = rt_rq->rt_runtime;
839 rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
840 if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
841 rt_rq->rt_throttled = 0;
842 enqueue = 1;
843
844 /*
845 * When we're idle and a woken (rt) task is
846 * throttled wakeup_preempt() will set
847 * skip_update and the time between the wakeup
848 * and this unthrottle will get accounted as
849 * 'runtime'.
850 */
851 if (rt_rq->rt_nr_running && rq->curr == rq->idle)
852 rq_clock_cancel_skipupdate(rq);
853 }
854 if (rt_rq->rt_time || rt_rq->rt_nr_running)
855 idle = 0;
856 raw_spin_unlock(&rt_rq->rt_runtime_lock);
857 } else if (rt_rq->rt_nr_running) {
858 idle = 0;
859 if (!rt_rq_throttled(rt_rq))
860 enqueue = 1;
861 }
862 if (rt_rq->rt_throttled)
863 throttled = 1;
864
865 if (enqueue)
866 sched_rt_rq_enqueue(rt_rq);
867 rq_unlock(rq, &rf);
868 }
869
870 if (!throttled && (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF))
871 return 1;
872
873 return idle;
874}
875
876static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
877{
878 u64 runtime = sched_rt_runtime(rt_rq);
879
880 if (rt_rq->rt_throttled)
881 return rt_rq_throttled(rt_rq);
882
883 if (runtime >= sched_rt_period(rt_rq))
884 return 0;
885
886 balance_runtime(rt_rq);
887 runtime = sched_rt_runtime(rt_rq);
888 if (runtime == RUNTIME_INF)
889 return 0;
890
891 if (rt_rq->rt_time > runtime) {
892 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
893
894 /*
895 * Don't actually throttle groups that have no runtime assigned
896 * but accrue some time due to boosting.
897 */
898 if (likely(rt_b->rt_runtime)) {
899 rt_rq->rt_throttled = 1;
900 printk_deferred_once("sched: RT throttling activated\n");
901 } else {
902 /*
903 * In case we did anyway, make it go away,
904 * replenishment is a joke, since it will replenish us
905 * with exactly 0 ns.
906 */
907 rt_rq->rt_time = 0;
908 }
909
910 if (rt_rq_throttled(rt_rq)) {
911 sched_rt_rq_dequeue(rt_rq);
912 return 1;
913 }
914 }
915
916 return 0;
917}
918
919#else /* !CONFIG_RT_GROUP_SCHED */
920
921typedef struct rt_rq *rt_rq_iter_t;
922
923#define for_each_rt_rq(rt_rq, iter, rq) \
924 for ((void) iter, rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
925
926#define for_each_sched_rt_entity(rt_se) \
927 for (; rt_se; rt_se = NULL)
928
929static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
930{
931 return NULL;
932}
933
934static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
935{
936 struct rq *rq = rq_of_rt_rq(rt_rq);
937
938 if (!rt_rq->rt_nr_running)
939 return;
940
941 enqueue_top_rt_rq(rt_rq);
942 resched_curr(rq);
943}
944
945static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
946{
947 dequeue_top_rt_rq(rt_rq, rt_rq->rt_nr_running);
948}
949
950static inline int rt_rq_throttled(struct rt_rq *rt_rq)
951{
952 return false;
953}
954
955static inline const struct cpumask *sched_rt_period_mask(void)
956{
957 return cpu_online_mask;
958}
959
960static inline
961struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
962{
963 return &cpu_rq(cpu)->rt;
964}
965
966#ifdef CONFIG_SMP
967static void __enable_runtime(struct rq *rq) { }
968static void __disable_runtime(struct rq *rq) { }
969#endif
970
971#endif /* CONFIG_RT_GROUP_SCHED */
972
973static inline int rt_se_prio(struct sched_rt_entity *rt_se)
974{
975#ifdef CONFIG_RT_GROUP_SCHED
976 struct rt_rq *rt_rq = group_rt_rq(rt_se);
977
978 if (rt_rq)
979 return rt_rq->highest_prio.curr;
980#endif
981
982 return rt_task_of(rt_se)->prio;
983}
984
985/*
986 * Update the current task's runtime statistics. Skip current tasks that
987 * are not in our scheduling class.
988 */
989static void update_curr_rt(struct rq *rq)
990{
991 struct task_struct *donor = rq->donor;
992 s64 delta_exec;
993
994 if (donor->sched_class != &rt_sched_class)
995 return;
996
997 delta_exec = update_curr_common(rq);
998 if (unlikely(delta_exec <= 0))
999 return;
1000
1001#ifdef CONFIG_RT_GROUP_SCHED
1002 struct sched_rt_entity *rt_se = &donor->rt;
1003
1004 if (!rt_bandwidth_enabled())
1005 return;
1006
1007 for_each_sched_rt_entity(rt_se) {
1008 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
1009 int exceeded;
1010
1011 if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
1012 raw_spin_lock(&rt_rq->rt_runtime_lock);
1013 rt_rq->rt_time += delta_exec;
1014 exceeded = sched_rt_runtime_exceeded(rt_rq);
1015 if (exceeded)
1016 resched_curr(rq);
1017 raw_spin_unlock(&rt_rq->rt_runtime_lock);
1018 if (exceeded)
1019 do_start_rt_bandwidth(sched_rt_bandwidth(rt_rq));
1020 }
1021 }
1022#endif
1023}
1024
1025static void
1026dequeue_top_rt_rq(struct rt_rq *rt_rq, unsigned int count)
1027{
1028 struct rq *rq = rq_of_rt_rq(rt_rq);
1029
1030 BUG_ON(&rq->rt != rt_rq);
1031
1032 if (!rt_rq->rt_queued)
1033 return;
1034
1035 BUG_ON(!rq->nr_running);
1036
1037 sub_nr_running(rq, count);
1038 rt_rq->rt_queued = 0;
1039
1040}
1041
1042static void
1043enqueue_top_rt_rq(struct rt_rq *rt_rq)
1044{
1045 struct rq *rq = rq_of_rt_rq(rt_rq);
1046
1047 BUG_ON(&rq->rt != rt_rq);
1048
1049 if (rt_rq->rt_queued)
1050 return;
1051
1052 if (rt_rq_throttled(rt_rq))
1053 return;
1054
1055 if (rt_rq->rt_nr_running) {
1056 add_nr_running(rq, rt_rq->rt_nr_running);
1057 rt_rq->rt_queued = 1;
1058 }
1059
1060 /* Kick cpufreq (see the comment in kernel/sched/sched.h). */
1061 cpufreq_update_util(rq, 0);
1062}
1063
1064#if defined CONFIG_SMP
1065
1066static void
1067inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
1068{
1069 struct rq *rq = rq_of_rt_rq(rt_rq);
1070
1071#ifdef CONFIG_RT_GROUP_SCHED
1072 /*
1073 * Change rq's cpupri only if rt_rq is the top queue.
1074 */
1075 if (&rq->rt != rt_rq)
1076 return;
1077#endif
1078 if (rq->online && prio < prev_prio)
1079 cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
1080}
1081
1082static void
1083dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
1084{
1085 struct rq *rq = rq_of_rt_rq(rt_rq);
1086
1087#ifdef CONFIG_RT_GROUP_SCHED
1088 /*
1089 * Change rq's cpupri only if rt_rq is the top queue.
1090 */
1091 if (&rq->rt != rt_rq)
1092 return;
1093#endif
1094 if (rq->online && rt_rq->highest_prio.curr != prev_prio)
1095 cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
1096}
1097
1098#else /* CONFIG_SMP */
1099
1100static inline
1101void inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
1102static inline
1103void dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
1104
1105#endif /* CONFIG_SMP */
1106
1107#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
1108static void
1109inc_rt_prio(struct rt_rq *rt_rq, int prio)
1110{
1111 int prev_prio = rt_rq->highest_prio.curr;
1112
1113 if (prio < prev_prio)
1114 rt_rq->highest_prio.curr = prio;
1115
1116 inc_rt_prio_smp(rt_rq, prio, prev_prio);
1117}
1118
1119static void
1120dec_rt_prio(struct rt_rq *rt_rq, int prio)
1121{
1122 int prev_prio = rt_rq->highest_prio.curr;
1123
1124 if (rt_rq->rt_nr_running) {
1125
1126 WARN_ON(prio < prev_prio);
1127
1128 /*
1129 * This may have been our highest task, and therefore
1130 * we may have some re-computation to do
1131 */
1132 if (prio == prev_prio) {
1133 struct rt_prio_array *array = &rt_rq->active;
1134
1135 rt_rq->highest_prio.curr =
1136 sched_find_first_bit(array->bitmap);
1137 }
1138
1139 } else {
1140 rt_rq->highest_prio.curr = MAX_RT_PRIO-1;
1141 }
1142
1143 dec_rt_prio_smp(rt_rq, prio, prev_prio);
1144}
1145
1146#else
1147
1148static inline void inc_rt_prio(struct rt_rq *rt_rq, int prio) {}
1149static inline void dec_rt_prio(struct rt_rq *rt_rq, int prio) {}
1150
1151#endif /* CONFIG_SMP || CONFIG_RT_GROUP_SCHED */
1152
1153#ifdef CONFIG_RT_GROUP_SCHED
1154
1155static void
1156inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1157{
1158 if (rt_se_boosted(rt_se))
1159 rt_rq->rt_nr_boosted++;
1160
1161 if (rt_rq->tg)
1162 start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
1163}
1164
1165static void
1166dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1167{
1168 if (rt_se_boosted(rt_se))
1169 rt_rq->rt_nr_boosted--;
1170
1171 WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
1172}
1173
1174#else /* CONFIG_RT_GROUP_SCHED */
1175
1176static void
1177inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1178{
1179}
1180
1181static inline
1182void dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) {}
1183
1184#endif /* CONFIG_RT_GROUP_SCHED */
1185
1186static inline
1187unsigned int rt_se_nr_running(struct sched_rt_entity *rt_se)
1188{
1189 struct rt_rq *group_rq = group_rt_rq(rt_se);
1190
1191 if (group_rq)
1192 return group_rq->rt_nr_running;
1193 else
1194 return 1;
1195}
1196
1197static inline
1198unsigned int rt_se_rr_nr_running(struct sched_rt_entity *rt_se)
1199{
1200 struct rt_rq *group_rq = group_rt_rq(rt_se);
1201 struct task_struct *tsk;
1202
1203 if (group_rq)
1204 return group_rq->rr_nr_running;
1205
1206 tsk = rt_task_of(rt_se);
1207
1208 return (tsk->policy == SCHED_RR) ? 1 : 0;
1209}
1210
1211static inline
1212void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1213{
1214 int prio = rt_se_prio(rt_se);
1215
1216 WARN_ON(!rt_prio(prio));
1217 rt_rq->rt_nr_running += rt_se_nr_running(rt_se);
1218 rt_rq->rr_nr_running += rt_se_rr_nr_running(rt_se);
1219
1220 inc_rt_prio(rt_rq, prio);
1221 inc_rt_group(rt_se, rt_rq);
1222}
1223
1224static inline
1225void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1226{
1227 WARN_ON(!rt_prio(rt_se_prio(rt_se)));
1228 WARN_ON(!rt_rq->rt_nr_running);
1229 rt_rq->rt_nr_running -= rt_se_nr_running(rt_se);
1230 rt_rq->rr_nr_running -= rt_se_rr_nr_running(rt_se);
1231
1232 dec_rt_prio(rt_rq, rt_se_prio(rt_se));
1233 dec_rt_group(rt_se, rt_rq);
1234}
1235
1236/*
1237 * Change rt_se->run_list location unless SAVE && !MOVE
1238 *
1239 * assumes ENQUEUE/DEQUEUE flags match
1240 */
1241static inline bool move_entity(unsigned int flags)
1242{
1243 if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE)
1244 return false;
1245
1246 return true;
1247}
1248
1249static void __delist_rt_entity(struct sched_rt_entity *rt_se, struct rt_prio_array *array)
1250{
1251 list_del_init(&rt_se->run_list);
1252
1253 if (list_empty(array->queue + rt_se_prio(rt_se)))
1254 __clear_bit(rt_se_prio(rt_se), array->bitmap);
1255
1256 rt_se->on_list = 0;
1257}
1258
1259static inline struct sched_statistics *
1260__schedstats_from_rt_se(struct sched_rt_entity *rt_se)
1261{
1262#ifdef CONFIG_RT_GROUP_SCHED
1263 /* schedstats is not supported for rt group. */
1264 if (!rt_entity_is_task(rt_se))
1265 return NULL;
1266#endif
1267
1268 return &rt_task_of(rt_se)->stats;
1269}
1270
1271static inline void
1272update_stats_wait_start_rt(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
1273{
1274 struct sched_statistics *stats;
1275 struct task_struct *p = NULL;
1276
1277 if (!schedstat_enabled())
1278 return;
1279
1280 if (rt_entity_is_task(rt_se))
1281 p = rt_task_of(rt_se);
1282
1283 stats = __schedstats_from_rt_se(rt_se);
1284 if (!stats)
1285 return;
1286
1287 __update_stats_wait_start(rq_of_rt_rq(rt_rq), p, stats);
1288}
1289
1290static inline void
1291update_stats_enqueue_sleeper_rt(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
1292{
1293 struct sched_statistics *stats;
1294 struct task_struct *p = NULL;
1295
1296 if (!schedstat_enabled())
1297 return;
1298
1299 if (rt_entity_is_task(rt_se))
1300 p = rt_task_of(rt_se);
1301
1302 stats = __schedstats_from_rt_se(rt_se);
1303 if (!stats)
1304 return;
1305
1306 __update_stats_enqueue_sleeper(rq_of_rt_rq(rt_rq), p, stats);
1307}
1308
1309static inline void
1310update_stats_enqueue_rt(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se,
1311 int flags)
1312{
1313 if (!schedstat_enabled())
1314 return;
1315
1316 if (flags & ENQUEUE_WAKEUP)
1317 update_stats_enqueue_sleeper_rt(rt_rq, rt_se);
1318}
1319
1320static inline void
1321update_stats_wait_end_rt(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
1322{
1323 struct sched_statistics *stats;
1324 struct task_struct *p = NULL;
1325
1326 if (!schedstat_enabled())
1327 return;
1328
1329 if (rt_entity_is_task(rt_se))
1330 p = rt_task_of(rt_se);
1331
1332 stats = __schedstats_from_rt_se(rt_se);
1333 if (!stats)
1334 return;
1335
1336 __update_stats_wait_end(rq_of_rt_rq(rt_rq), p, stats);
1337}
1338
1339static inline void
1340update_stats_dequeue_rt(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se,
1341 int flags)
1342{
1343 struct task_struct *p = NULL;
1344
1345 if (!schedstat_enabled())
1346 return;
1347
1348 if (rt_entity_is_task(rt_se))
1349 p = rt_task_of(rt_se);
1350
1351 if ((flags & DEQUEUE_SLEEP) && p) {
1352 unsigned int state;
1353
1354 state = READ_ONCE(p->__state);
1355 if (state & TASK_INTERRUPTIBLE)
1356 __schedstat_set(p->stats.sleep_start,
1357 rq_clock(rq_of_rt_rq(rt_rq)));
1358
1359 if (state & TASK_UNINTERRUPTIBLE)
1360 __schedstat_set(p->stats.block_start,
1361 rq_clock(rq_of_rt_rq(rt_rq)));
1362 }
1363}
1364
1365static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1366{
1367 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
1368 struct rt_prio_array *array = &rt_rq->active;
1369 struct rt_rq *group_rq = group_rt_rq(rt_se);
1370 struct list_head *queue = array->queue + rt_se_prio(rt_se);
1371
1372 /*
1373 * Don't enqueue the group if its throttled, or when empty.
1374 * The latter is a consequence of the former when a child group
1375 * get throttled and the current group doesn't have any other
1376 * active members.
1377 */
1378 if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running)) {
1379 if (rt_se->on_list)
1380 __delist_rt_entity(rt_se, array);
1381 return;
1382 }
1383
1384 if (move_entity(flags)) {
1385 WARN_ON_ONCE(rt_se->on_list);
1386 if (flags & ENQUEUE_HEAD)
1387 list_add(&rt_se->run_list, queue);
1388 else
1389 list_add_tail(&rt_se->run_list, queue);
1390
1391 __set_bit(rt_se_prio(rt_se), array->bitmap);
1392 rt_se->on_list = 1;
1393 }
1394 rt_se->on_rq = 1;
1395
1396 inc_rt_tasks(rt_se, rt_rq);
1397}
1398
1399static void __dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1400{
1401 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
1402 struct rt_prio_array *array = &rt_rq->active;
1403
1404 if (move_entity(flags)) {
1405 WARN_ON_ONCE(!rt_se->on_list);
1406 __delist_rt_entity(rt_se, array);
1407 }
1408 rt_se->on_rq = 0;
1409
1410 dec_rt_tasks(rt_se, rt_rq);
1411}
1412
1413/*
1414 * Because the prio of an upper entry depends on the lower
1415 * entries, we must remove entries top - down.
1416 */
1417static void dequeue_rt_stack(struct sched_rt_entity *rt_se, unsigned int flags)
1418{
1419 struct sched_rt_entity *back = NULL;
1420 unsigned int rt_nr_running;
1421
1422 for_each_sched_rt_entity(rt_se) {
1423 rt_se->back = back;
1424 back = rt_se;
1425 }
1426
1427 rt_nr_running = rt_rq_of_se(back)->rt_nr_running;
1428
1429 for (rt_se = back; rt_se; rt_se = rt_se->back) {
1430 if (on_rt_rq(rt_se))
1431 __dequeue_rt_entity(rt_se, flags);
1432 }
1433
1434 dequeue_top_rt_rq(rt_rq_of_se(back), rt_nr_running);
1435}
1436
1437static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1438{
1439 struct rq *rq = rq_of_rt_se(rt_se);
1440
1441 update_stats_enqueue_rt(rt_rq_of_se(rt_se), rt_se, flags);
1442
1443 dequeue_rt_stack(rt_se, flags);
1444 for_each_sched_rt_entity(rt_se)
1445 __enqueue_rt_entity(rt_se, flags);
1446 enqueue_top_rt_rq(&rq->rt);
1447}
1448
1449static void dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1450{
1451 struct rq *rq = rq_of_rt_se(rt_se);
1452
1453 update_stats_dequeue_rt(rt_rq_of_se(rt_se), rt_se, flags);
1454
1455 dequeue_rt_stack(rt_se, flags);
1456
1457 for_each_sched_rt_entity(rt_se) {
1458 struct rt_rq *rt_rq = group_rt_rq(rt_se);
1459
1460 if (rt_rq && rt_rq->rt_nr_running)
1461 __enqueue_rt_entity(rt_se, flags);
1462 }
1463 enqueue_top_rt_rq(&rq->rt);
1464}
1465
1466/*
1467 * Adding/removing a task to/from a priority array:
1468 */
1469static void
1470enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
1471{
1472 struct sched_rt_entity *rt_se = &p->rt;
1473
1474 if (flags & ENQUEUE_WAKEUP)
1475 rt_se->timeout = 0;
1476
1477 check_schedstat_required();
1478 update_stats_wait_start_rt(rt_rq_of_se(rt_se), rt_se);
1479
1480 enqueue_rt_entity(rt_se, flags);
1481
1482 if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
1483 enqueue_pushable_task(rq, p);
1484}
1485
1486static bool dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
1487{
1488 struct sched_rt_entity *rt_se = &p->rt;
1489
1490 update_curr_rt(rq);
1491 dequeue_rt_entity(rt_se, flags);
1492
1493 dequeue_pushable_task(rq, p);
1494
1495 return true;
1496}
1497
1498/*
1499 * Put task to the head or the end of the run list without the overhead of
1500 * dequeue followed by enqueue.
1501 */
1502static void
1503requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
1504{
1505 if (on_rt_rq(rt_se)) {
1506 struct rt_prio_array *array = &rt_rq->active;
1507 struct list_head *queue = array->queue + rt_se_prio(rt_se);
1508
1509 if (head)
1510 list_move(&rt_se->run_list, queue);
1511 else
1512 list_move_tail(&rt_se->run_list, queue);
1513 }
1514}
1515
1516static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
1517{
1518 struct sched_rt_entity *rt_se = &p->rt;
1519 struct rt_rq *rt_rq;
1520
1521 for_each_sched_rt_entity(rt_se) {
1522 rt_rq = rt_rq_of_se(rt_se);
1523 requeue_rt_entity(rt_rq, rt_se, head);
1524 }
1525}
1526
1527static void yield_task_rt(struct rq *rq)
1528{
1529 requeue_task_rt(rq, rq->curr, 0);
1530}
1531
1532#ifdef CONFIG_SMP
1533static int find_lowest_rq(struct task_struct *task);
1534
1535static int
1536select_task_rq_rt(struct task_struct *p, int cpu, int flags)
1537{
1538 struct task_struct *curr, *donor;
1539 struct rq *rq;
1540 bool test;
1541
1542 /* For anything but wake ups, just return the task_cpu */
1543 if (!(flags & (WF_TTWU | WF_FORK)))
1544 goto out;
1545
1546 rq = cpu_rq(cpu);
1547
1548 rcu_read_lock();
1549 curr = READ_ONCE(rq->curr); /* unlocked access */
1550 donor = READ_ONCE(rq->donor);
1551
1552 /*
1553 * If the current task on @p's runqueue is an RT task, then
1554 * try to see if we can wake this RT task up on another
1555 * runqueue. Otherwise simply start this RT task
1556 * on its current runqueue.
1557 *
1558 * We want to avoid overloading runqueues. If the woken
1559 * task is a higher priority, then it will stay on this CPU
1560 * and the lower prio task should be moved to another CPU.
1561 * Even though this will probably make the lower prio task
1562 * lose its cache, we do not want to bounce a higher task
1563 * around just because it gave up its CPU, perhaps for a
1564 * lock?
1565 *
1566 * For equal prio tasks, we just let the scheduler sort it out.
1567 *
1568 * Otherwise, just let it ride on the affine RQ and the
1569 * post-schedule router will push the preempted task away
1570 *
1571 * This test is optimistic, if we get it wrong the load-balancer
1572 * will have to sort it out.
1573 *
1574 * We take into account the capacity of the CPU to ensure it fits the
1575 * requirement of the task - which is only important on heterogeneous
1576 * systems like big.LITTLE.
1577 */
1578 test = curr &&
1579 unlikely(rt_task(donor)) &&
1580 (curr->nr_cpus_allowed < 2 || donor->prio <= p->prio);
1581
1582 if (test || !rt_task_fits_capacity(p, cpu)) {
1583 int target = find_lowest_rq(p);
1584
1585 /*
1586 * Bail out if we were forcing a migration to find a better
1587 * fitting CPU but our search failed.
1588 */
1589 if (!test && target != -1 && !rt_task_fits_capacity(p, target))
1590 goto out_unlock;
1591
1592 /*
1593 * Don't bother moving it if the destination CPU is
1594 * not running a lower priority task.
1595 */
1596 if (target != -1 &&
1597 p->prio < cpu_rq(target)->rt.highest_prio.curr)
1598 cpu = target;
1599 }
1600
1601out_unlock:
1602 rcu_read_unlock();
1603
1604out:
1605 return cpu;
1606}
1607
1608static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
1609{
1610 if (rq->curr->nr_cpus_allowed == 1 ||
1611 !cpupri_find(&rq->rd->cpupri, rq->donor, NULL))
1612 return;
1613
1614 /*
1615 * p is migratable, so let's not schedule it and
1616 * see if it is pushed or pulled somewhere else.
1617 */
1618 if (p->nr_cpus_allowed != 1 &&
1619 cpupri_find(&rq->rd->cpupri, p, NULL))
1620 return;
1621
1622 /*
1623 * There appear to be other CPUs that can accept
1624 * the current task but none can run 'p', so lets reschedule
1625 * to try and push the current task away:
1626 */
1627 requeue_task_rt(rq, p, 1);
1628 resched_curr(rq);
1629}
1630
1631static int balance_rt(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
1632{
1633 if (!on_rt_rq(&p->rt) && need_pull_rt_task(rq, p)) {
1634 /*
1635 * This is OK, because current is on_cpu, which avoids it being
1636 * picked for load-balance and preemption/IRQs are still
1637 * disabled avoiding further scheduler activity on it and we've
1638 * not yet started the picking loop.
1639 */
1640 rq_unpin_lock(rq, rf);
1641 pull_rt_task(rq);
1642 rq_repin_lock(rq, rf);
1643 }
1644
1645 return sched_stop_runnable(rq) || sched_dl_runnable(rq) || sched_rt_runnable(rq);
1646}
1647#endif /* CONFIG_SMP */
1648
1649/*
1650 * Preempt the current task with a newly woken task if needed:
1651 */
1652static void wakeup_preempt_rt(struct rq *rq, struct task_struct *p, int flags)
1653{
1654 struct task_struct *donor = rq->donor;
1655
1656 if (p->prio < donor->prio) {
1657 resched_curr(rq);
1658 return;
1659 }
1660
1661#ifdef CONFIG_SMP
1662 /*
1663 * If:
1664 *
1665 * - the newly woken task is of equal priority to the current task
1666 * - the newly woken task is non-migratable while current is migratable
1667 * - current will be preempted on the next reschedule
1668 *
1669 * we should check to see if current can readily move to a different
1670 * cpu. If so, we will reschedule to allow the push logic to try
1671 * to move current somewhere else, making room for our non-migratable
1672 * task.
1673 */
1674 if (p->prio == donor->prio && !test_tsk_need_resched(rq->curr))
1675 check_preempt_equal_prio(rq, p);
1676#endif
1677}
1678
1679static inline void set_next_task_rt(struct rq *rq, struct task_struct *p, bool first)
1680{
1681 struct sched_rt_entity *rt_se = &p->rt;
1682 struct rt_rq *rt_rq = &rq->rt;
1683
1684 p->se.exec_start = rq_clock_task(rq);
1685 if (on_rt_rq(&p->rt))
1686 update_stats_wait_end_rt(rt_rq, rt_se);
1687
1688 /* The running task is never eligible for pushing */
1689 dequeue_pushable_task(rq, p);
1690
1691 if (!first)
1692 return;
1693
1694 /*
1695 * If prev task was rt, put_prev_task() has already updated the
1696 * utilization. We only care of the case where we start to schedule a
1697 * rt task
1698 */
1699 if (rq->donor->sched_class != &rt_sched_class)
1700 update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0);
1701
1702 rt_queue_push_tasks(rq);
1703}
1704
1705static struct sched_rt_entity *pick_next_rt_entity(struct rt_rq *rt_rq)
1706{
1707 struct rt_prio_array *array = &rt_rq->active;
1708 struct sched_rt_entity *next = NULL;
1709 struct list_head *queue;
1710 int idx;
1711
1712 idx = sched_find_first_bit(array->bitmap);
1713 BUG_ON(idx >= MAX_RT_PRIO);
1714
1715 queue = array->queue + idx;
1716 if (SCHED_WARN_ON(list_empty(queue)))
1717 return NULL;
1718 next = list_entry(queue->next, struct sched_rt_entity, run_list);
1719
1720 return next;
1721}
1722
1723static struct task_struct *_pick_next_task_rt(struct rq *rq)
1724{
1725 struct sched_rt_entity *rt_se;
1726 struct rt_rq *rt_rq = &rq->rt;
1727
1728 do {
1729 rt_se = pick_next_rt_entity(rt_rq);
1730 if (unlikely(!rt_se))
1731 return NULL;
1732 rt_rq = group_rt_rq(rt_se);
1733 } while (rt_rq);
1734
1735 return rt_task_of(rt_se);
1736}
1737
1738static struct task_struct *pick_task_rt(struct rq *rq)
1739{
1740 struct task_struct *p;
1741
1742 if (!sched_rt_runnable(rq))
1743 return NULL;
1744
1745 p = _pick_next_task_rt(rq);
1746
1747 return p;
1748}
1749
1750static void put_prev_task_rt(struct rq *rq, struct task_struct *p, struct task_struct *next)
1751{
1752 struct sched_rt_entity *rt_se = &p->rt;
1753 struct rt_rq *rt_rq = &rq->rt;
1754
1755 if (on_rt_rq(&p->rt))
1756 update_stats_wait_start_rt(rt_rq, rt_se);
1757
1758 update_curr_rt(rq);
1759
1760 update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 1);
1761
1762 /*
1763 * The previous task needs to be made eligible for pushing
1764 * if it is still active
1765 */
1766 if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1)
1767 enqueue_pushable_task(rq, p);
1768}
1769
1770#ifdef CONFIG_SMP
1771
1772/* Only try algorithms three times */
1773#define RT_MAX_TRIES 3
1774
1775/*
1776 * Return the highest pushable rq's task, which is suitable to be executed
1777 * on the CPU, NULL otherwise
1778 */
1779static struct task_struct *pick_highest_pushable_task(struct rq *rq, int cpu)
1780{
1781 struct plist_head *head = &rq->rt.pushable_tasks;
1782 struct task_struct *p;
1783
1784 if (!has_pushable_tasks(rq))
1785 return NULL;
1786
1787 plist_for_each_entry(p, head, pushable_tasks) {
1788 if (task_is_pushable(rq, p, cpu))
1789 return p;
1790 }
1791
1792 return NULL;
1793}
1794
1795static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
1796
1797static int find_lowest_rq(struct task_struct *task)
1798{
1799 struct sched_domain *sd;
1800 struct cpumask *lowest_mask = this_cpu_cpumask_var_ptr(local_cpu_mask);
1801 int this_cpu = smp_processor_id();
1802 int cpu = task_cpu(task);
1803 int ret;
1804
1805 /* Make sure the mask is initialized first */
1806 if (unlikely(!lowest_mask))
1807 return -1;
1808
1809 if (task->nr_cpus_allowed == 1)
1810 return -1; /* No other targets possible */
1811
1812 /*
1813 * If we're on asym system ensure we consider the different capacities
1814 * of the CPUs when searching for the lowest_mask.
1815 */
1816 if (sched_asym_cpucap_active()) {
1817
1818 ret = cpupri_find_fitness(&task_rq(task)->rd->cpupri,
1819 task, lowest_mask,
1820 rt_task_fits_capacity);
1821 } else {
1822
1823 ret = cpupri_find(&task_rq(task)->rd->cpupri,
1824 task, lowest_mask);
1825 }
1826
1827 if (!ret)
1828 return -1; /* No targets found */
1829
1830 /*
1831 * At this point we have built a mask of CPUs representing the
1832 * lowest priority tasks in the system. Now we want to elect
1833 * the best one based on our affinity and topology.
1834 *
1835 * We prioritize the last CPU that the task executed on since
1836 * it is most likely cache-hot in that location.
1837 */
1838 if (cpumask_test_cpu(cpu, lowest_mask))
1839 return cpu;
1840
1841 /*
1842 * Otherwise, we consult the sched_domains span maps to figure
1843 * out which CPU is logically closest to our hot cache data.
1844 */
1845 if (!cpumask_test_cpu(this_cpu, lowest_mask))
1846 this_cpu = -1; /* Skip this_cpu opt if not among lowest */
1847
1848 rcu_read_lock();
1849 for_each_domain(cpu, sd) {
1850 if (sd->flags & SD_WAKE_AFFINE) {
1851 int best_cpu;
1852
1853 /*
1854 * "this_cpu" is cheaper to preempt than a
1855 * remote processor.
1856 */
1857 if (this_cpu != -1 &&
1858 cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
1859 rcu_read_unlock();
1860 return this_cpu;
1861 }
1862
1863 best_cpu = cpumask_any_and_distribute(lowest_mask,
1864 sched_domain_span(sd));
1865 if (best_cpu < nr_cpu_ids) {
1866 rcu_read_unlock();
1867 return best_cpu;
1868 }
1869 }
1870 }
1871 rcu_read_unlock();
1872
1873 /*
1874 * And finally, if there were no matches within the domains
1875 * just give the caller *something* to work with from the compatible
1876 * locations.
1877 */
1878 if (this_cpu != -1)
1879 return this_cpu;
1880
1881 cpu = cpumask_any_distribute(lowest_mask);
1882 if (cpu < nr_cpu_ids)
1883 return cpu;
1884
1885 return -1;
1886}
1887
1888/* Will lock the rq it finds */
1889static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1890{
1891 struct rq *lowest_rq = NULL;
1892 int tries;
1893 int cpu;
1894
1895 for (tries = 0; tries < RT_MAX_TRIES; tries++) {
1896 cpu = find_lowest_rq(task);
1897
1898 if ((cpu == -1) || (cpu == rq->cpu))
1899 break;
1900
1901 lowest_rq = cpu_rq(cpu);
1902
1903 if (lowest_rq->rt.highest_prio.curr <= task->prio) {
1904 /*
1905 * Target rq has tasks of equal or higher priority,
1906 * retrying does not release any lock and is unlikely
1907 * to yield a different result.
1908 */
1909 lowest_rq = NULL;
1910 break;
1911 }
1912
1913 /* if the prio of this runqueue changed, try again */
1914 if (double_lock_balance(rq, lowest_rq)) {
1915 /*
1916 * We had to unlock the run queue. In
1917 * the mean time, task could have
1918 * migrated already or had its affinity changed.
1919 * Also make sure that it wasn't scheduled on its rq.
1920 * It is possible the task was scheduled, set
1921 * "migrate_disabled" and then got preempted, so we must
1922 * check the task migration disable flag here too.
1923 */
1924 if (unlikely(task_rq(task) != rq ||
1925 !cpumask_test_cpu(lowest_rq->cpu, &task->cpus_mask) ||
1926 task_on_cpu(rq, task) ||
1927 !rt_task(task) ||
1928 is_migration_disabled(task) ||
1929 !task_on_rq_queued(task))) {
1930
1931 double_unlock_balance(rq, lowest_rq);
1932 lowest_rq = NULL;
1933 break;
1934 }
1935 }
1936
1937 /* If this rq is still suitable use it. */
1938 if (lowest_rq->rt.highest_prio.curr > task->prio)
1939 break;
1940
1941 /* try again */
1942 double_unlock_balance(rq, lowest_rq);
1943 lowest_rq = NULL;
1944 }
1945
1946 return lowest_rq;
1947}
1948
1949static struct task_struct *pick_next_pushable_task(struct rq *rq)
1950{
1951 struct task_struct *p;
1952
1953 if (!has_pushable_tasks(rq))
1954 return NULL;
1955
1956 p = plist_first_entry(&rq->rt.pushable_tasks,
1957 struct task_struct, pushable_tasks);
1958
1959 BUG_ON(rq->cpu != task_cpu(p));
1960 BUG_ON(task_current(rq, p));
1961 BUG_ON(task_current_donor(rq, p));
1962 BUG_ON(p->nr_cpus_allowed <= 1);
1963
1964 BUG_ON(!task_on_rq_queued(p));
1965 BUG_ON(!rt_task(p));
1966
1967 return p;
1968}
1969
1970/*
1971 * If the current CPU has more than one RT task, see if the non
1972 * running task can migrate over to a CPU that is running a task
1973 * of lesser priority.
1974 */
1975static int push_rt_task(struct rq *rq, bool pull)
1976{
1977 struct task_struct *next_task;
1978 struct rq *lowest_rq;
1979 int ret = 0;
1980
1981 if (!rq->rt.overloaded)
1982 return 0;
1983
1984 next_task = pick_next_pushable_task(rq);
1985 if (!next_task)
1986 return 0;
1987
1988retry:
1989 /*
1990 * It's possible that the next_task slipped in of
1991 * higher priority than current. If that's the case
1992 * just reschedule current.
1993 */
1994 if (unlikely(next_task->prio < rq->donor->prio)) {
1995 resched_curr(rq);
1996 return 0;
1997 }
1998
1999 if (is_migration_disabled(next_task)) {
2000 struct task_struct *push_task = NULL;
2001 int cpu;
2002
2003 if (!pull || rq->push_busy)
2004 return 0;
2005
2006 /*
2007 * Invoking find_lowest_rq() on anything but an RT task doesn't
2008 * make sense. Per the above priority check, curr has to
2009 * be of higher priority than next_task, so no need to
2010 * reschedule when bailing out.
2011 *
2012 * Note that the stoppers are masqueraded as SCHED_FIFO
2013 * (cf. sched_set_stop_task()), so we can't rely on rt_task().
2014 */
2015 if (rq->donor->sched_class != &rt_sched_class)
2016 return 0;
2017
2018 cpu = find_lowest_rq(rq->curr);
2019 if (cpu == -1 || cpu == rq->cpu)
2020 return 0;
2021
2022 /*
2023 * Given we found a CPU with lower priority than @next_task,
2024 * therefore it should be running. However we cannot migrate it
2025 * to this other CPU, instead attempt to push the current
2026 * running task on this CPU away.
2027 */
2028 push_task = get_push_task(rq);
2029 if (push_task) {
2030 preempt_disable();
2031 raw_spin_rq_unlock(rq);
2032 stop_one_cpu_nowait(rq->cpu, push_cpu_stop,
2033 push_task, &rq->push_work);
2034 preempt_enable();
2035 raw_spin_rq_lock(rq);
2036 }
2037
2038 return 0;
2039 }
2040
2041 if (WARN_ON(next_task == rq->curr))
2042 return 0;
2043
2044 /* We might release rq lock */
2045 get_task_struct(next_task);
2046
2047 /* find_lock_lowest_rq locks the rq if found */
2048 lowest_rq = find_lock_lowest_rq(next_task, rq);
2049 if (!lowest_rq) {
2050 struct task_struct *task;
2051 /*
2052 * find_lock_lowest_rq releases rq->lock
2053 * so it is possible that next_task has migrated.
2054 *
2055 * We need to make sure that the task is still on the same
2056 * run-queue and is also still the next task eligible for
2057 * pushing.
2058 */
2059 task = pick_next_pushable_task(rq);
2060 if (task == next_task) {
2061 /*
2062 * The task hasn't migrated, and is still the next
2063 * eligible task, but we failed to find a run-queue
2064 * to push it to. Do not retry in this case, since
2065 * other CPUs will pull from us when ready.
2066 */
2067 goto out;
2068 }
2069
2070 if (!task)
2071 /* No more tasks, just exit */
2072 goto out;
2073
2074 /*
2075 * Something has shifted, try again.
2076 */
2077 put_task_struct(next_task);
2078 next_task = task;
2079 goto retry;
2080 }
2081
2082 move_queued_task_locked(rq, lowest_rq, next_task);
2083 resched_curr(lowest_rq);
2084 ret = 1;
2085
2086 double_unlock_balance(rq, lowest_rq);
2087out:
2088 put_task_struct(next_task);
2089
2090 return ret;
2091}
2092
2093static void push_rt_tasks(struct rq *rq)
2094{
2095 /* push_rt_task will return true if it moved an RT */
2096 while (push_rt_task(rq, false))
2097 ;
2098}
2099
2100#ifdef HAVE_RT_PUSH_IPI
2101
2102/*
2103 * When a high priority task schedules out from a CPU and a lower priority
2104 * task is scheduled in, a check is made to see if there's any RT tasks
2105 * on other CPUs that are waiting to run because a higher priority RT task
2106 * is currently running on its CPU. In this case, the CPU with multiple RT
2107 * tasks queued on it (overloaded) needs to be notified that a CPU has opened
2108 * up that may be able to run one of its non-running queued RT tasks.
2109 *
2110 * All CPUs with overloaded RT tasks need to be notified as there is currently
2111 * no way to know which of these CPUs have the highest priority task waiting
2112 * to run. Instead of trying to take a spinlock on each of these CPUs,
2113 * which has shown to cause large latency when done on machines with many
2114 * CPUs, sending an IPI to the CPUs to have them push off the overloaded
2115 * RT tasks waiting to run.
2116 *
2117 * Just sending an IPI to each of the CPUs is also an issue, as on large
2118 * count CPU machines, this can cause an IPI storm on a CPU, especially
2119 * if its the only CPU with multiple RT tasks queued, and a large number
2120 * of CPUs scheduling a lower priority task at the same time.
2121 *
2122 * Each root domain has its own IRQ work function that can iterate over
2123 * all CPUs with RT overloaded tasks. Since all CPUs with overloaded RT
2124 * task must be checked if there's one or many CPUs that are lowering
2125 * their priority, there's a single IRQ work iterator that will try to
2126 * push off RT tasks that are waiting to run.
2127 *
2128 * When a CPU schedules a lower priority task, it will kick off the
2129 * IRQ work iterator that will jump to each CPU with overloaded RT tasks.
2130 * As it only takes the first CPU that schedules a lower priority task
2131 * to start the process, the rto_start variable is incremented and if
2132 * the atomic result is one, then that CPU will try to take the rto_lock.
2133 * This prevents high contention on the lock as the process handles all
2134 * CPUs scheduling lower priority tasks.
2135 *
2136 * All CPUs that are scheduling a lower priority task will increment the
2137 * rt_loop_next variable. This will make sure that the IRQ work iterator
2138 * checks all RT overloaded CPUs whenever a CPU schedules a new lower
2139 * priority task, even if the iterator is in the middle of a scan. Incrementing
2140 * the rt_loop_next will cause the iterator to perform another scan.
2141 *
2142 */
2143static int rto_next_cpu(struct root_domain *rd)
2144{
2145 int next;
2146 int cpu;
2147
2148 /*
2149 * When starting the IPI RT pushing, the rto_cpu is set to -1,
2150 * rt_next_cpu() will simply return the first CPU found in
2151 * the rto_mask.
2152 *
2153 * If rto_next_cpu() is called with rto_cpu is a valid CPU, it
2154 * will return the next CPU found in the rto_mask.
2155 *
2156 * If there are no more CPUs left in the rto_mask, then a check is made
2157 * against rto_loop and rto_loop_next. rto_loop is only updated with
2158 * the rto_lock held, but any CPU may increment the rto_loop_next
2159 * without any locking.
2160 */
2161 for (;;) {
2162
2163 /* When rto_cpu is -1 this acts like cpumask_first() */
2164 cpu = cpumask_next(rd->rto_cpu, rd->rto_mask);
2165
2166 rd->rto_cpu = cpu;
2167
2168 if (cpu < nr_cpu_ids)
2169 return cpu;
2170
2171 rd->rto_cpu = -1;
2172
2173 /*
2174 * ACQUIRE ensures we see the @rto_mask changes
2175 * made prior to the @next value observed.
2176 *
2177 * Matches WMB in rt_set_overload().
2178 */
2179 next = atomic_read_acquire(&rd->rto_loop_next);
2180
2181 if (rd->rto_loop == next)
2182 break;
2183
2184 rd->rto_loop = next;
2185 }
2186
2187 return -1;
2188}
2189
2190static inline bool rto_start_trylock(atomic_t *v)
2191{
2192 return !atomic_cmpxchg_acquire(v, 0, 1);
2193}
2194
2195static inline void rto_start_unlock(atomic_t *v)
2196{
2197 atomic_set_release(v, 0);
2198}
2199
2200static void tell_cpu_to_push(struct rq *rq)
2201{
2202 int cpu = -1;
2203
2204 /* Keep the loop going if the IPI is currently active */
2205 atomic_inc(&rq->rd->rto_loop_next);
2206
2207 /* Only one CPU can initiate a loop at a time */
2208 if (!rto_start_trylock(&rq->rd->rto_loop_start))
2209 return;
2210
2211 raw_spin_lock(&rq->rd->rto_lock);
2212
2213 /*
2214 * The rto_cpu is updated under the lock, if it has a valid CPU
2215 * then the IPI is still running and will continue due to the
2216 * update to loop_next, and nothing needs to be done here.
2217 * Otherwise it is finishing up and an IPI needs to be sent.
2218 */
2219 if (rq->rd->rto_cpu < 0)
2220 cpu = rto_next_cpu(rq->rd);
2221
2222 raw_spin_unlock(&rq->rd->rto_lock);
2223
2224 rto_start_unlock(&rq->rd->rto_loop_start);
2225
2226 if (cpu >= 0) {
2227 /* Make sure the rd does not get freed while pushing */
2228 sched_get_rd(rq->rd);
2229 irq_work_queue_on(&rq->rd->rto_push_work, cpu);
2230 }
2231}
2232
2233/* Called from hardirq context */
2234void rto_push_irq_work_func(struct irq_work *work)
2235{
2236 struct root_domain *rd =
2237 container_of(work, struct root_domain, rto_push_work);
2238 struct rq *rq;
2239 int cpu;
2240
2241 rq = this_rq();
2242
2243 /*
2244 * We do not need to grab the lock to check for has_pushable_tasks.
2245 * When it gets updated, a check is made if a push is possible.
2246 */
2247 if (has_pushable_tasks(rq)) {
2248 raw_spin_rq_lock(rq);
2249 while (push_rt_task(rq, true))
2250 ;
2251 raw_spin_rq_unlock(rq);
2252 }
2253
2254 raw_spin_lock(&rd->rto_lock);
2255
2256 /* Pass the IPI to the next rt overloaded queue */
2257 cpu = rto_next_cpu(rd);
2258
2259 raw_spin_unlock(&rd->rto_lock);
2260
2261 if (cpu < 0) {
2262 sched_put_rd(rd);
2263 return;
2264 }
2265
2266 /* Try the next RT overloaded CPU */
2267 irq_work_queue_on(&rd->rto_push_work, cpu);
2268}
2269#endif /* HAVE_RT_PUSH_IPI */
2270
2271static void pull_rt_task(struct rq *this_rq)
2272{
2273 int this_cpu = this_rq->cpu, cpu;
2274 bool resched = false;
2275 struct task_struct *p, *push_task;
2276 struct rq *src_rq;
2277 int rt_overload_count = rt_overloaded(this_rq);
2278
2279 if (likely(!rt_overload_count))
2280 return;
2281
2282 /*
2283 * Match the barrier from rt_set_overloaded; this guarantees that if we
2284 * see overloaded we must also see the rto_mask bit.
2285 */
2286 smp_rmb();
2287
2288 /* If we are the only overloaded CPU do nothing */
2289 if (rt_overload_count == 1 &&
2290 cpumask_test_cpu(this_rq->cpu, this_rq->rd->rto_mask))
2291 return;
2292
2293#ifdef HAVE_RT_PUSH_IPI
2294 if (sched_feat(RT_PUSH_IPI)) {
2295 tell_cpu_to_push(this_rq);
2296 return;
2297 }
2298#endif
2299
2300 for_each_cpu(cpu, this_rq->rd->rto_mask) {
2301 if (this_cpu == cpu)
2302 continue;
2303
2304 src_rq = cpu_rq(cpu);
2305
2306 /*
2307 * Don't bother taking the src_rq->lock if the next highest
2308 * task is known to be lower-priority than our current task.
2309 * This may look racy, but if this value is about to go
2310 * logically higher, the src_rq will push this task away.
2311 * And if its going logically lower, we do not care
2312 */
2313 if (src_rq->rt.highest_prio.next >=
2314 this_rq->rt.highest_prio.curr)
2315 continue;
2316
2317 /*
2318 * We can potentially drop this_rq's lock in
2319 * double_lock_balance, and another CPU could
2320 * alter this_rq
2321 */
2322 push_task = NULL;
2323 double_lock_balance(this_rq, src_rq);
2324
2325 /*
2326 * We can pull only a task, which is pushable
2327 * on its rq, and no others.
2328 */
2329 p = pick_highest_pushable_task(src_rq, this_cpu);
2330
2331 /*
2332 * Do we have an RT task that preempts
2333 * the to-be-scheduled task?
2334 */
2335 if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
2336 WARN_ON(p == src_rq->curr);
2337 WARN_ON(!task_on_rq_queued(p));
2338
2339 /*
2340 * There's a chance that p is higher in priority
2341 * than what's currently running on its CPU.
2342 * This is just that p is waking up and hasn't
2343 * had a chance to schedule. We only pull
2344 * p if it is lower in priority than the
2345 * current task on the run queue
2346 */
2347 if (p->prio < src_rq->donor->prio)
2348 goto skip;
2349
2350 if (is_migration_disabled(p)) {
2351 push_task = get_push_task(src_rq);
2352 } else {
2353 move_queued_task_locked(src_rq, this_rq, p);
2354 resched = true;
2355 }
2356 /*
2357 * We continue with the search, just in
2358 * case there's an even higher prio task
2359 * in another runqueue. (low likelihood
2360 * but possible)
2361 */
2362 }
2363skip:
2364 double_unlock_balance(this_rq, src_rq);
2365
2366 if (push_task) {
2367 preempt_disable();
2368 raw_spin_rq_unlock(this_rq);
2369 stop_one_cpu_nowait(src_rq->cpu, push_cpu_stop,
2370 push_task, &src_rq->push_work);
2371 preempt_enable();
2372 raw_spin_rq_lock(this_rq);
2373 }
2374 }
2375
2376 if (resched)
2377 resched_curr(this_rq);
2378}
2379
2380/*
2381 * If we are not running and we are not going to reschedule soon, we should
2382 * try to push tasks away now
2383 */
2384static void task_woken_rt(struct rq *rq, struct task_struct *p)
2385{
2386 bool need_to_push = !task_on_cpu(rq, p) &&
2387 !test_tsk_need_resched(rq->curr) &&
2388 p->nr_cpus_allowed > 1 &&
2389 (dl_task(rq->donor) || rt_task(rq->donor)) &&
2390 (rq->curr->nr_cpus_allowed < 2 ||
2391 rq->donor->prio <= p->prio);
2392
2393 if (need_to_push)
2394 push_rt_tasks(rq);
2395}
2396
2397/* Assumes rq->lock is held */
2398static void rq_online_rt(struct rq *rq)
2399{
2400 if (rq->rt.overloaded)
2401 rt_set_overload(rq);
2402
2403 __enable_runtime(rq);
2404
2405 cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
2406}
2407
2408/* Assumes rq->lock is held */
2409static void rq_offline_rt(struct rq *rq)
2410{
2411 if (rq->rt.overloaded)
2412 rt_clear_overload(rq);
2413
2414 __disable_runtime(rq);
2415
2416 cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
2417}
2418
2419/*
2420 * When switch from the rt queue, we bring ourselves to a position
2421 * that we might want to pull RT tasks from other runqueues.
2422 */
2423static void switched_from_rt(struct rq *rq, struct task_struct *p)
2424{
2425 /*
2426 * If there are other RT tasks then we will reschedule
2427 * and the scheduling of the other RT tasks will handle
2428 * the balancing. But if we are the last RT task
2429 * we may need to handle the pulling of RT tasks
2430 * now.
2431 */
2432 if (!task_on_rq_queued(p) || rq->rt.rt_nr_running)
2433 return;
2434
2435 rt_queue_pull_task(rq);
2436}
2437
2438void __init init_sched_rt_class(void)
2439{
2440 unsigned int i;
2441
2442 for_each_possible_cpu(i) {
2443 zalloc_cpumask_var_node(&per_cpu(local_cpu_mask, i),
2444 GFP_KERNEL, cpu_to_node(i));
2445 }
2446}
2447#endif /* CONFIG_SMP */
2448
2449/*
2450 * When switching a task to RT, we may overload the runqueue
2451 * with RT tasks. In this case we try to push them off to
2452 * other runqueues.
2453 */
2454static void switched_to_rt(struct rq *rq, struct task_struct *p)
2455{
2456 /*
2457 * If we are running, update the avg_rt tracking, as the running time
2458 * will now on be accounted into the latter.
2459 */
2460 if (task_current(rq, p)) {
2461 update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0);
2462 return;
2463 }
2464
2465 /*
2466 * If we are not running we may need to preempt the current
2467 * running task. If that current running task is also an RT task
2468 * then see if we can move to another run queue.
2469 */
2470 if (task_on_rq_queued(p)) {
2471#ifdef CONFIG_SMP
2472 if (p->nr_cpus_allowed > 1 && rq->rt.overloaded)
2473 rt_queue_push_tasks(rq);
2474#endif /* CONFIG_SMP */
2475 if (p->prio < rq->donor->prio && cpu_online(cpu_of(rq)))
2476 resched_curr(rq);
2477 }
2478}
2479
2480/*
2481 * Priority of the task has changed. This may cause
2482 * us to initiate a push or pull.
2483 */
2484static void
2485prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
2486{
2487 if (!task_on_rq_queued(p))
2488 return;
2489
2490 if (task_current_donor(rq, p)) {
2491#ifdef CONFIG_SMP
2492 /*
2493 * If our priority decreases while running, we
2494 * may need to pull tasks to this runqueue.
2495 */
2496 if (oldprio < p->prio)
2497 rt_queue_pull_task(rq);
2498
2499 /*
2500 * If there's a higher priority task waiting to run
2501 * then reschedule.
2502 */
2503 if (p->prio > rq->rt.highest_prio.curr)
2504 resched_curr(rq);
2505#else
2506 /* For UP simply resched on drop of prio */
2507 if (oldprio < p->prio)
2508 resched_curr(rq);
2509#endif /* CONFIG_SMP */
2510 } else {
2511 /*
2512 * This task is not running, but if it is
2513 * greater than the current running task
2514 * then reschedule.
2515 */
2516 if (p->prio < rq->donor->prio)
2517 resched_curr(rq);
2518 }
2519}
2520
2521#ifdef CONFIG_POSIX_TIMERS
2522static void watchdog(struct rq *rq, struct task_struct *p)
2523{
2524 unsigned long soft, hard;
2525
2526 /* max may change after cur was read, this will be fixed next tick */
2527 soft = task_rlimit(p, RLIMIT_RTTIME);
2528 hard = task_rlimit_max(p, RLIMIT_RTTIME);
2529
2530 if (soft != RLIM_INFINITY) {
2531 unsigned long next;
2532
2533 if (p->rt.watchdog_stamp != jiffies) {
2534 p->rt.timeout++;
2535 p->rt.watchdog_stamp = jiffies;
2536 }
2537
2538 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
2539 if (p->rt.timeout > next) {
2540 posix_cputimers_rt_watchdog(&p->posix_cputimers,
2541 p->se.sum_exec_runtime);
2542 }
2543 }
2544}
2545#else
2546static inline void watchdog(struct rq *rq, struct task_struct *p) { }
2547#endif
2548
2549/*
2550 * scheduler tick hitting a task of our scheduling class.
2551 *
2552 * NOTE: This function can be called remotely by the tick offload that
2553 * goes along full dynticks. Therefore no local assumption can be made
2554 * and everything must be accessed through the @rq and @curr passed in
2555 * parameters.
2556 */
2557static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
2558{
2559 struct sched_rt_entity *rt_se = &p->rt;
2560
2561 update_curr_rt(rq);
2562 update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 1);
2563
2564 watchdog(rq, p);
2565
2566 /*
2567 * RR tasks need a special form of time-slice management.
2568 * FIFO tasks have no timeslices.
2569 */
2570 if (p->policy != SCHED_RR)
2571 return;
2572
2573 if (--p->rt.time_slice)
2574 return;
2575
2576 p->rt.time_slice = sched_rr_timeslice;
2577
2578 /*
2579 * Requeue to the end of queue if we (and all of our ancestors) are not
2580 * the only element on the queue
2581 */
2582 for_each_sched_rt_entity(rt_se) {
2583 if (rt_se->run_list.prev != rt_se->run_list.next) {
2584 requeue_task_rt(rq, p, 0);
2585 resched_curr(rq);
2586 return;
2587 }
2588 }
2589}
2590
2591static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
2592{
2593 /*
2594 * Time slice is 0 for SCHED_FIFO tasks
2595 */
2596 if (task->policy == SCHED_RR)
2597 return sched_rr_timeslice;
2598 else
2599 return 0;
2600}
2601
2602#ifdef CONFIG_SCHED_CORE
2603static int task_is_throttled_rt(struct task_struct *p, int cpu)
2604{
2605 struct rt_rq *rt_rq;
2606
2607#ifdef CONFIG_RT_GROUP_SCHED
2608 rt_rq = task_group(p)->rt_rq[cpu];
2609#else
2610 rt_rq = &cpu_rq(cpu)->rt;
2611#endif
2612
2613 return rt_rq_throttled(rt_rq);
2614}
2615#endif
2616
2617DEFINE_SCHED_CLASS(rt) = {
2618
2619 .enqueue_task = enqueue_task_rt,
2620 .dequeue_task = dequeue_task_rt,
2621 .yield_task = yield_task_rt,
2622
2623 .wakeup_preempt = wakeup_preempt_rt,
2624
2625 .pick_task = pick_task_rt,
2626 .put_prev_task = put_prev_task_rt,
2627 .set_next_task = set_next_task_rt,
2628
2629#ifdef CONFIG_SMP
2630 .balance = balance_rt,
2631 .select_task_rq = select_task_rq_rt,
2632 .set_cpus_allowed = set_cpus_allowed_common,
2633 .rq_online = rq_online_rt,
2634 .rq_offline = rq_offline_rt,
2635 .task_woken = task_woken_rt,
2636 .switched_from = switched_from_rt,
2637 .find_lock_rq = find_lock_lowest_rq,
2638#endif
2639
2640 .task_tick = task_tick_rt,
2641
2642 .get_rr_interval = get_rr_interval_rt,
2643
2644 .prio_changed = prio_changed_rt,
2645 .switched_to = switched_to_rt,
2646
2647 .update_curr = update_curr_rt,
2648
2649#ifdef CONFIG_SCHED_CORE
2650 .task_is_throttled = task_is_throttled_rt,
2651#endif
2652
2653#ifdef CONFIG_UCLAMP_TASK
2654 .uclamp_enabled = 1,
2655#endif
2656};
2657
2658#ifdef CONFIG_RT_GROUP_SCHED
2659/*
2660 * Ensure that the real time constraints are schedulable.
2661 */
2662static DEFINE_MUTEX(rt_constraints_mutex);
2663
2664static inline int tg_has_rt_tasks(struct task_group *tg)
2665{
2666 struct task_struct *task;
2667 struct css_task_iter it;
2668 int ret = 0;
2669
2670 /*
2671 * Autogroups do not have RT tasks; see autogroup_create().
2672 */
2673 if (task_group_is_autogroup(tg))
2674 return 0;
2675
2676 css_task_iter_start(&tg->css, 0, &it);
2677 while (!ret && (task = css_task_iter_next(&it)))
2678 ret |= rt_task(task);
2679 css_task_iter_end(&it);
2680
2681 return ret;
2682}
2683
2684struct rt_schedulable_data {
2685 struct task_group *tg;
2686 u64 rt_period;
2687 u64 rt_runtime;
2688};
2689
2690static int tg_rt_schedulable(struct task_group *tg, void *data)
2691{
2692 struct rt_schedulable_data *d = data;
2693 struct task_group *child;
2694 unsigned long total, sum = 0;
2695 u64 period, runtime;
2696
2697 period = ktime_to_ns(tg->rt_bandwidth.rt_period);
2698 runtime = tg->rt_bandwidth.rt_runtime;
2699
2700 if (tg == d->tg) {
2701 period = d->rt_period;
2702 runtime = d->rt_runtime;
2703 }
2704
2705 /*
2706 * Cannot have more runtime than the period.
2707 */
2708 if (runtime > period && runtime != RUNTIME_INF)
2709 return -EINVAL;
2710
2711 /*
2712 * Ensure we don't starve existing RT tasks if runtime turns zero.
2713 */
2714 if (rt_bandwidth_enabled() && !runtime &&
2715 tg->rt_bandwidth.rt_runtime && tg_has_rt_tasks(tg))
2716 return -EBUSY;
2717
2718 total = to_ratio(period, runtime);
2719
2720 /*
2721 * Nobody can have more than the global setting allows.
2722 */
2723 if (total > to_ratio(global_rt_period(), global_rt_runtime()))
2724 return -EINVAL;
2725
2726 /*
2727 * The sum of our children's runtime should not exceed our own.
2728 */
2729 list_for_each_entry_rcu(child, &tg->children, siblings) {
2730 period = ktime_to_ns(child->rt_bandwidth.rt_period);
2731 runtime = child->rt_bandwidth.rt_runtime;
2732
2733 if (child == d->tg) {
2734 period = d->rt_period;
2735 runtime = d->rt_runtime;
2736 }
2737
2738 sum += to_ratio(period, runtime);
2739 }
2740
2741 if (sum > total)
2742 return -EINVAL;
2743
2744 return 0;
2745}
2746
2747static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
2748{
2749 int ret;
2750
2751 struct rt_schedulable_data data = {
2752 .tg = tg,
2753 .rt_period = period,
2754 .rt_runtime = runtime,
2755 };
2756
2757 rcu_read_lock();
2758 ret = walk_tg_tree(tg_rt_schedulable, tg_nop, &data);
2759 rcu_read_unlock();
2760
2761 return ret;
2762}
2763
2764static int tg_set_rt_bandwidth(struct task_group *tg,
2765 u64 rt_period, u64 rt_runtime)
2766{
2767 int i, err = 0;
2768
2769 /*
2770 * Disallowing the root group RT runtime is BAD, it would disallow the
2771 * kernel creating (and or operating) RT threads.
2772 */
2773 if (tg == &root_task_group && rt_runtime == 0)
2774 return -EINVAL;
2775
2776 /* No period doesn't make any sense. */
2777 if (rt_period == 0)
2778 return -EINVAL;
2779
2780 /*
2781 * Bound quota to defend quota against overflow during bandwidth shift.
2782 */
2783 if (rt_runtime != RUNTIME_INF && rt_runtime > max_rt_runtime)
2784 return -EINVAL;
2785
2786 mutex_lock(&rt_constraints_mutex);
2787 err = __rt_schedulable(tg, rt_period, rt_runtime);
2788 if (err)
2789 goto unlock;
2790
2791 raw_spin_lock_irq(&tg->rt_bandwidth.rt_runtime_lock);
2792 tg->rt_bandwidth.rt_period = ns_to_ktime(rt_period);
2793 tg->rt_bandwidth.rt_runtime = rt_runtime;
2794
2795 for_each_possible_cpu(i) {
2796 struct rt_rq *rt_rq = tg->rt_rq[i];
2797
2798 raw_spin_lock(&rt_rq->rt_runtime_lock);
2799 rt_rq->rt_runtime = rt_runtime;
2800 raw_spin_unlock(&rt_rq->rt_runtime_lock);
2801 }
2802 raw_spin_unlock_irq(&tg->rt_bandwidth.rt_runtime_lock);
2803unlock:
2804 mutex_unlock(&rt_constraints_mutex);
2805
2806 return err;
2807}
2808
2809int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)
2810{
2811 u64 rt_runtime, rt_period;
2812
2813 rt_period = ktime_to_ns(tg->rt_bandwidth.rt_period);
2814 rt_runtime = (u64)rt_runtime_us * NSEC_PER_USEC;
2815 if (rt_runtime_us < 0)
2816 rt_runtime = RUNTIME_INF;
2817 else if ((u64)rt_runtime_us > U64_MAX / NSEC_PER_USEC)
2818 return -EINVAL;
2819
2820 return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
2821}
2822
2823long sched_group_rt_runtime(struct task_group *tg)
2824{
2825 u64 rt_runtime_us;
2826
2827 if (tg->rt_bandwidth.rt_runtime == RUNTIME_INF)
2828 return -1;
2829
2830 rt_runtime_us = tg->rt_bandwidth.rt_runtime;
2831 do_div(rt_runtime_us, NSEC_PER_USEC);
2832 return rt_runtime_us;
2833}
2834
2835int sched_group_set_rt_period(struct task_group *tg, u64 rt_period_us)
2836{
2837 u64 rt_runtime, rt_period;
2838
2839 if (rt_period_us > U64_MAX / NSEC_PER_USEC)
2840 return -EINVAL;
2841
2842 rt_period = rt_period_us * NSEC_PER_USEC;
2843 rt_runtime = tg->rt_bandwidth.rt_runtime;
2844
2845 return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
2846}
2847
2848long sched_group_rt_period(struct task_group *tg)
2849{
2850 u64 rt_period_us;
2851
2852 rt_period_us = ktime_to_ns(tg->rt_bandwidth.rt_period);
2853 do_div(rt_period_us, NSEC_PER_USEC);
2854 return rt_period_us;
2855}
2856
2857#ifdef CONFIG_SYSCTL
2858static int sched_rt_global_constraints(void)
2859{
2860 int ret = 0;
2861
2862 mutex_lock(&rt_constraints_mutex);
2863 ret = __rt_schedulable(NULL, 0, 0);
2864 mutex_unlock(&rt_constraints_mutex);
2865
2866 return ret;
2867}
2868#endif /* CONFIG_SYSCTL */
2869
2870int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
2871{
2872 /* Don't accept real-time tasks when there is no way for them to run */
2873 if (rt_task(tsk) && tg->rt_bandwidth.rt_runtime == 0)
2874 return 0;
2875
2876 return 1;
2877}
2878
2879#else /* !CONFIG_RT_GROUP_SCHED */
2880
2881#ifdef CONFIG_SYSCTL
2882static int sched_rt_global_constraints(void)
2883{
2884 return 0;
2885}
2886#endif /* CONFIG_SYSCTL */
2887#endif /* CONFIG_RT_GROUP_SCHED */
2888
2889#ifdef CONFIG_SYSCTL
2890static int sched_rt_global_validate(void)
2891{
2892 if ((sysctl_sched_rt_runtime != RUNTIME_INF) &&
2893 ((sysctl_sched_rt_runtime > sysctl_sched_rt_period) ||
2894 ((u64)sysctl_sched_rt_runtime *
2895 NSEC_PER_USEC > max_rt_runtime)))
2896 return -EINVAL;
2897
2898 return 0;
2899}
2900
2901static void sched_rt_do_global(void)
2902{
2903}
2904
2905static int sched_rt_handler(const struct ctl_table *table, int write, void *buffer,
2906 size_t *lenp, loff_t *ppos)
2907{
2908 int old_period, old_runtime;
2909 static DEFINE_MUTEX(mutex);
2910 int ret;
2911
2912 mutex_lock(&mutex);
2913 old_period = sysctl_sched_rt_period;
2914 old_runtime = sysctl_sched_rt_runtime;
2915
2916 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
2917
2918 if (!ret && write) {
2919 ret = sched_rt_global_validate();
2920 if (ret)
2921 goto undo;
2922
2923 ret = sched_dl_global_validate();
2924 if (ret)
2925 goto undo;
2926
2927 ret = sched_rt_global_constraints();
2928 if (ret)
2929 goto undo;
2930
2931 sched_rt_do_global();
2932 sched_dl_do_global();
2933 }
2934 if (0) {
2935undo:
2936 sysctl_sched_rt_period = old_period;
2937 sysctl_sched_rt_runtime = old_runtime;
2938 }
2939 mutex_unlock(&mutex);
2940
2941 return ret;
2942}
2943
2944static int sched_rr_handler(const struct ctl_table *table, int write, void *buffer,
2945 size_t *lenp, loff_t *ppos)
2946{
2947 int ret;
2948 static DEFINE_MUTEX(mutex);
2949
2950 mutex_lock(&mutex);
2951 ret = proc_dointvec(table, write, buffer, lenp, ppos);
2952 /*
2953 * Make sure that internally we keep jiffies.
2954 * Also, writing zero resets the time-slice to default:
2955 */
2956 if (!ret && write) {
2957 sched_rr_timeslice =
2958 sysctl_sched_rr_timeslice <= 0 ? RR_TIMESLICE :
2959 msecs_to_jiffies(sysctl_sched_rr_timeslice);
2960
2961 if (sysctl_sched_rr_timeslice <= 0)
2962 sysctl_sched_rr_timeslice = jiffies_to_msecs(RR_TIMESLICE);
2963 }
2964 mutex_unlock(&mutex);
2965
2966 return ret;
2967}
2968#endif /* CONFIG_SYSCTL */
2969
2970#ifdef CONFIG_SCHED_DEBUG
2971void print_rt_stats(struct seq_file *m, int cpu)
2972{
2973 rt_rq_iter_t iter;
2974 struct rt_rq *rt_rq;
2975
2976 rcu_read_lock();
2977 for_each_rt_rq(rt_rq, iter, cpu_rq(cpu))
2978 print_rt_rq(m, cpu, rt_rq);
2979 rcu_read_unlock();
2980}
2981#endif /* CONFIG_SCHED_DEBUG */
1/*
2 * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
3 * policies)
4 */
5
6#include "sched.h"
7
8#include <linux/slab.h>
9
10int sched_rr_timeslice = RR_TIMESLICE;
11
12static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);
13
14struct rt_bandwidth def_rt_bandwidth;
15
16static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer)
17{
18 struct rt_bandwidth *rt_b =
19 container_of(timer, struct rt_bandwidth, rt_period_timer);
20 ktime_t now;
21 int overrun;
22 int idle = 0;
23
24 for (;;) {
25 now = hrtimer_cb_get_time(timer);
26 overrun = hrtimer_forward(timer, now, rt_b->rt_period);
27
28 if (!overrun)
29 break;
30
31 idle = do_sched_rt_period_timer(rt_b, overrun);
32 }
33
34 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
35}
36
37void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime)
38{
39 rt_b->rt_period = ns_to_ktime(period);
40 rt_b->rt_runtime = runtime;
41
42 raw_spin_lock_init(&rt_b->rt_runtime_lock);
43
44 hrtimer_init(&rt_b->rt_period_timer,
45 CLOCK_MONOTONIC, HRTIMER_MODE_REL);
46 rt_b->rt_period_timer.function = sched_rt_period_timer;
47}
48
49static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
50{
51 if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
52 return;
53
54 if (hrtimer_active(&rt_b->rt_period_timer))
55 return;
56
57 raw_spin_lock(&rt_b->rt_runtime_lock);
58 start_bandwidth_timer(&rt_b->rt_period_timer, rt_b->rt_period);
59 raw_spin_unlock(&rt_b->rt_runtime_lock);
60}
61
62void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq)
63{
64 struct rt_prio_array *array;
65 int i;
66
67 array = &rt_rq->active;
68 for (i = 0; i < MAX_RT_PRIO; i++) {
69 INIT_LIST_HEAD(array->queue + i);
70 __clear_bit(i, array->bitmap);
71 }
72 /* delimiter for bitsearch: */
73 __set_bit(MAX_RT_PRIO, array->bitmap);
74
75#if defined CONFIG_SMP
76 rt_rq->highest_prio.curr = MAX_RT_PRIO;
77 rt_rq->highest_prio.next = MAX_RT_PRIO;
78 rt_rq->rt_nr_migratory = 0;
79 rt_rq->overloaded = 0;
80 plist_head_init(&rt_rq->pushable_tasks);
81#endif
82
83 rt_rq->rt_time = 0;
84 rt_rq->rt_throttled = 0;
85 rt_rq->rt_runtime = 0;
86 raw_spin_lock_init(&rt_rq->rt_runtime_lock);
87}
88
89#ifdef CONFIG_RT_GROUP_SCHED
90static void destroy_rt_bandwidth(struct rt_bandwidth *rt_b)
91{
92 hrtimer_cancel(&rt_b->rt_period_timer);
93}
94
95#define rt_entity_is_task(rt_se) (!(rt_se)->my_q)
96
97static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
98{
99#ifdef CONFIG_SCHED_DEBUG
100 WARN_ON_ONCE(!rt_entity_is_task(rt_se));
101#endif
102 return container_of(rt_se, struct task_struct, rt);
103}
104
105static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
106{
107 return rt_rq->rq;
108}
109
110static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
111{
112 return rt_se->rt_rq;
113}
114
115void free_rt_sched_group(struct task_group *tg)
116{
117 int i;
118
119 if (tg->rt_se)
120 destroy_rt_bandwidth(&tg->rt_bandwidth);
121
122 for_each_possible_cpu(i) {
123 if (tg->rt_rq)
124 kfree(tg->rt_rq[i]);
125 if (tg->rt_se)
126 kfree(tg->rt_se[i]);
127 }
128
129 kfree(tg->rt_rq);
130 kfree(tg->rt_se);
131}
132
133void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
134 struct sched_rt_entity *rt_se, int cpu,
135 struct sched_rt_entity *parent)
136{
137 struct rq *rq = cpu_rq(cpu);
138
139 rt_rq->highest_prio.curr = MAX_RT_PRIO;
140 rt_rq->rt_nr_boosted = 0;
141 rt_rq->rq = rq;
142 rt_rq->tg = tg;
143
144 tg->rt_rq[cpu] = rt_rq;
145 tg->rt_se[cpu] = rt_se;
146
147 if (!rt_se)
148 return;
149
150 if (!parent)
151 rt_se->rt_rq = &rq->rt;
152 else
153 rt_se->rt_rq = parent->my_q;
154
155 rt_se->my_q = rt_rq;
156 rt_se->parent = parent;
157 INIT_LIST_HEAD(&rt_se->run_list);
158}
159
160int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
161{
162 struct rt_rq *rt_rq;
163 struct sched_rt_entity *rt_se;
164 int i;
165
166 tg->rt_rq = kzalloc(sizeof(rt_rq) * nr_cpu_ids, GFP_KERNEL);
167 if (!tg->rt_rq)
168 goto err;
169 tg->rt_se = kzalloc(sizeof(rt_se) * nr_cpu_ids, GFP_KERNEL);
170 if (!tg->rt_se)
171 goto err;
172
173 init_rt_bandwidth(&tg->rt_bandwidth,
174 ktime_to_ns(def_rt_bandwidth.rt_period), 0);
175
176 for_each_possible_cpu(i) {
177 rt_rq = kzalloc_node(sizeof(struct rt_rq),
178 GFP_KERNEL, cpu_to_node(i));
179 if (!rt_rq)
180 goto err;
181
182 rt_se = kzalloc_node(sizeof(struct sched_rt_entity),
183 GFP_KERNEL, cpu_to_node(i));
184 if (!rt_se)
185 goto err_free_rq;
186
187 init_rt_rq(rt_rq, cpu_rq(i));
188 rt_rq->rt_runtime = tg->rt_bandwidth.rt_runtime;
189 init_tg_rt_entry(tg, rt_rq, rt_se, i, parent->rt_se[i]);
190 }
191
192 return 1;
193
194err_free_rq:
195 kfree(rt_rq);
196err:
197 return 0;
198}
199
200#else /* CONFIG_RT_GROUP_SCHED */
201
202#define rt_entity_is_task(rt_se) (1)
203
204static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
205{
206 return container_of(rt_se, struct task_struct, rt);
207}
208
209static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
210{
211 return container_of(rt_rq, struct rq, rt);
212}
213
214static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
215{
216 struct task_struct *p = rt_task_of(rt_se);
217 struct rq *rq = task_rq(p);
218
219 return &rq->rt;
220}
221
222void free_rt_sched_group(struct task_group *tg) { }
223
224int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
225{
226 return 1;
227}
228#endif /* CONFIG_RT_GROUP_SCHED */
229
230#ifdef CONFIG_SMP
231
232static int pull_rt_task(struct rq *this_rq);
233
234static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
235{
236 /* Try to pull RT tasks here if we lower this rq's prio */
237 return rq->rt.highest_prio.curr > prev->prio;
238}
239
240static inline int rt_overloaded(struct rq *rq)
241{
242 return atomic_read(&rq->rd->rto_count);
243}
244
245static inline void rt_set_overload(struct rq *rq)
246{
247 if (!rq->online)
248 return;
249
250 cpumask_set_cpu(rq->cpu, rq->rd->rto_mask);
251 /*
252 * Make sure the mask is visible before we set
253 * the overload count. That is checked to determine
254 * if we should look at the mask. It would be a shame
255 * if we looked at the mask, but the mask was not
256 * updated yet.
257 *
258 * Matched by the barrier in pull_rt_task().
259 */
260 smp_wmb();
261 atomic_inc(&rq->rd->rto_count);
262}
263
264static inline void rt_clear_overload(struct rq *rq)
265{
266 if (!rq->online)
267 return;
268
269 /* the order here really doesn't matter */
270 atomic_dec(&rq->rd->rto_count);
271 cpumask_clear_cpu(rq->cpu, rq->rd->rto_mask);
272}
273
274static void update_rt_migration(struct rt_rq *rt_rq)
275{
276 if (rt_rq->rt_nr_migratory && rt_rq->rt_nr_total > 1) {
277 if (!rt_rq->overloaded) {
278 rt_set_overload(rq_of_rt_rq(rt_rq));
279 rt_rq->overloaded = 1;
280 }
281 } else if (rt_rq->overloaded) {
282 rt_clear_overload(rq_of_rt_rq(rt_rq));
283 rt_rq->overloaded = 0;
284 }
285}
286
287static void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
288{
289 struct task_struct *p;
290
291 if (!rt_entity_is_task(rt_se))
292 return;
293
294 p = rt_task_of(rt_se);
295 rt_rq = &rq_of_rt_rq(rt_rq)->rt;
296
297 rt_rq->rt_nr_total++;
298 if (p->nr_cpus_allowed > 1)
299 rt_rq->rt_nr_migratory++;
300
301 update_rt_migration(rt_rq);
302}
303
304static void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
305{
306 struct task_struct *p;
307
308 if (!rt_entity_is_task(rt_se))
309 return;
310
311 p = rt_task_of(rt_se);
312 rt_rq = &rq_of_rt_rq(rt_rq)->rt;
313
314 rt_rq->rt_nr_total--;
315 if (p->nr_cpus_allowed > 1)
316 rt_rq->rt_nr_migratory--;
317
318 update_rt_migration(rt_rq);
319}
320
321static inline int has_pushable_tasks(struct rq *rq)
322{
323 return !plist_head_empty(&rq->rt.pushable_tasks);
324}
325
326static inline void set_post_schedule(struct rq *rq)
327{
328 /*
329 * We detect this state here so that we can avoid taking the RQ
330 * lock again later if there is no need to push
331 */
332 rq->post_schedule = has_pushable_tasks(rq);
333}
334
335static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
336{
337 plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
338 plist_node_init(&p->pushable_tasks, p->prio);
339 plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks);
340
341 /* Update the highest prio pushable task */
342 if (p->prio < rq->rt.highest_prio.next)
343 rq->rt.highest_prio.next = p->prio;
344}
345
346static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
347{
348 plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
349
350 /* Update the new highest prio pushable task */
351 if (has_pushable_tasks(rq)) {
352 p = plist_first_entry(&rq->rt.pushable_tasks,
353 struct task_struct, pushable_tasks);
354 rq->rt.highest_prio.next = p->prio;
355 } else
356 rq->rt.highest_prio.next = MAX_RT_PRIO;
357}
358
359#else
360
361static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
362{
363}
364
365static inline void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
366{
367}
368
369static inline
370void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
371{
372}
373
374static inline
375void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
376{
377}
378
379static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
380{
381 return false;
382}
383
384static inline int pull_rt_task(struct rq *this_rq)
385{
386 return 0;
387}
388
389static inline void set_post_schedule(struct rq *rq)
390{
391}
392#endif /* CONFIG_SMP */
393
394static inline int on_rt_rq(struct sched_rt_entity *rt_se)
395{
396 return !list_empty(&rt_se->run_list);
397}
398
399#ifdef CONFIG_RT_GROUP_SCHED
400
401static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
402{
403 if (!rt_rq->tg)
404 return RUNTIME_INF;
405
406 return rt_rq->rt_runtime;
407}
408
409static inline u64 sched_rt_period(struct rt_rq *rt_rq)
410{
411 return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
412}
413
414typedef struct task_group *rt_rq_iter_t;
415
416static inline struct task_group *next_task_group(struct task_group *tg)
417{
418 do {
419 tg = list_entry_rcu(tg->list.next,
420 typeof(struct task_group), list);
421 } while (&tg->list != &task_groups && task_group_is_autogroup(tg));
422
423 if (&tg->list == &task_groups)
424 tg = NULL;
425
426 return tg;
427}
428
429#define for_each_rt_rq(rt_rq, iter, rq) \
430 for (iter = container_of(&task_groups, typeof(*iter), list); \
431 (iter = next_task_group(iter)) && \
432 (rt_rq = iter->rt_rq[cpu_of(rq)]);)
433
434#define for_each_sched_rt_entity(rt_se) \
435 for (; rt_se; rt_se = rt_se->parent)
436
437static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
438{
439 return rt_se->my_q;
440}
441
442static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head);
443static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
444
445static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
446{
447 struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
448 struct sched_rt_entity *rt_se;
449
450 int cpu = cpu_of(rq_of_rt_rq(rt_rq));
451
452 rt_se = rt_rq->tg->rt_se[cpu];
453
454 if (rt_rq->rt_nr_running) {
455 if (rt_se && !on_rt_rq(rt_se))
456 enqueue_rt_entity(rt_se, false);
457 if (rt_rq->highest_prio.curr < curr->prio)
458 resched_task(curr);
459 }
460}
461
462static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
463{
464 struct sched_rt_entity *rt_se;
465 int cpu = cpu_of(rq_of_rt_rq(rt_rq));
466
467 rt_se = rt_rq->tg->rt_se[cpu];
468
469 if (rt_se && on_rt_rq(rt_se))
470 dequeue_rt_entity(rt_se);
471}
472
473static int rt_se_boosted(struct sched_rt_entity *rt_se)
474{
475 struct rt_rq *rt_rq = group_rt_rq(rt_se);
476 struct task_struct *p;
477
478 if (rt_rq)
479 return !!rt_rq->rt_nr_boosted;
480
481 p = rt_task_of(rt_se);
482 return p->prio != p->normal_prio;
483}
484
485#ifdef CONFIG_SMP
486static inline const struct cpumask *sched_rt_period_mask(void)
487{
488 return this_rq()->rd->span;
489}
490#else
491static inline const struct cpumask *sched_rt_period_mask(void)
492{
493 return cpu_online_mask;
494}
495#endif
496
497static inline
498struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
499{
500 return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
501}
502
503static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
504{
505 return &rt_rq->tg->rt_bandwidth;
506}
507
508#else /* !CONFIG_RT_GROUP_SCHED */
509
510static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
511{
512 return rt_rq->rt_runtime;
513}
514
515static inline u64 sched_rt_period(struct rt_rq *rt_rq)
516{
517 return ktime_to_ns(def_rt_bandwidth.rt_period);
518}
519
520typedef struct rt_rq *rt_rq_iter_t;
521
522#define for_each_rt_rq(rt_rq, iter, rq) \
523 for ((void) iter, rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
524
525#define for_each_sched_rt_entity(rt_se) \
526 for (; rt_se; rt_se = NULL)
527
528static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
529{
530 return NULL;
531}
532
533static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
534{
535 if (rt_rq->rt_nr_running)
536 resched_task(rq_of_rt_rq(rt_rq)->curr);
537}
538
539static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
540{
541}
542
543static inline const struct cpumask *sched_rt_period_mask(void)
544{
545 return cpu_online_mask;
546}
547
548static inline
549struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
550{
551 return &cpu_rq(cpu)->rt;
552}
553
554static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
555{
556 return &def_rt_bandwidth;
557}
558
559#endif /* CONFIG_RT_GROUP_SCHED */
560
561bool sched_rt_bandwidth_account(struct rt_rq *rt_rq)
562{
563 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
564
565 return (hrtimer_active(&rt_b->rt_period_timer) ||
566 rt_rq->rt_time < rt_b->rt_runtime);
567}
568
569#ifdef CONFIG_SMP
570/*
571 * We ran out of runtime, see if we can borrow some from our neighbours.
572 */
573static int do_balance_runtime(struct rt_rq *rt_rq)
574{
575 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
576 struct root_domain *rd = rq_of_rt_rq(rt_rq)->rd;
577 int i, weight, more = 0;
578 u64 rt_period;
579
580 weight = cpumask_weight(rd->span);
581
582 raw_spin_lock(&rt_b->rt_runtime_lock);
583 rt_period = ktime_to_ns(rt_b->rt_period);
584 for_each_cpu(i, rd->span) {
585 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
586 s64 diff;
587
588 if (iter == rt_rq)
589 continue;
590
591 raw_spin_lock(&iter->rt_runtime_lock);
592 /*
593 * Either all rqs have inf runtime and there's nothing to steal
594 * or __disable_runtime() below sets a specific rq to inf to
595 * indicate its been disabled and disalow stealing.
596 */
597 if (iter->rt_runtime == RUNTIME_INF)
598 goto next;
599
600 /*
601 * From runqueues with spare time, take 1/n part of their
602 * spare time, but no more than our period.
603 */
604 diff = iter->rt_runtime - iter->rt_time;
605 if (diff > 0) {
606 diff = div_u64((u64)diff, weight);
607 if (rt_rq->rt_runtime + diff > rt_period)
608 diff = rt_period - rt_rq->rt_runtime;
609 iter->rt_runtime -= diff;
610 rt_rq->rt_runtime += diff;
611 more = 1;
612 if (rt_rq->rt_runtime == rt_period) {
613 raw_spin_unlock(&iter->rt_runtime_lock);
614 break;
615 }
616 }
617next:
618 raw_spin_unlock(&iter->rt_runtime_lock);
619 }
620 raw_spin_unlock(&rt_b->rt_runtime_lock);
621
622 return more;
623}
624
625/*
626 * Ensure this RQ takes back all the runtime it lend to its neighbours.
627 */
628static void __disable_runtime(struct rq *rq)
629{
630 struct root_domain *rd = rq->rd;
631 rt_rq_iter_t iter;
632 struct rt_rq *rt_rq;
633
634 if (unlikely(!scheduler_running))
635 return;
636
637 for_each_rt_rq(rt_rq, iter, rq) {
638 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
639 s64 want;
640 int i;
641
642 raw_spin_lock(&rt_b->rt_runtime_lock);
643 raw_spin_lock(&rt_rq->rt_runtime_lock);
644 /*
645 * Either we're all inf and nobody needs to borrow, or we're
646 * already disabled and thus have nothing to do, or we have
647 * exactly the right amount of runtime to take out.
648 */
649 if (rt_rq->rt_runtime == RUNTIME_INF ||
650 rt_rq->rt_runtime == rt_b->rt_runtime)
651 goto balanced;
652 raw_spin_unlock(&rt_rq->rt_runtime_lock);
653
654 /*
655 * Calculate the difference between what we started out with
656 * and what we current have, that's the amount of runtime
657 * we lend and now have to reclaim.
658 */
659 want = rt_b->rt_runtime - rt_rq->rt_runtime;
660
661 /*
662 * Greedy reclaim, take back as much as we can.
663 */
664 for_each_cpu(i, rd->span) {
665 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
666 s64 diff;
667
668 /*
669 * Can't reclaim from ourselves or disabled runqueues.
670 */
671 if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
672 continue;
673
674 raw_spin_lock(&iter->rt_runtime_lock);
675 if (want > 0) {
676 diff = min_t(s64, iter->rt_runtime, want);
677 iter->rt_runtime -= diff;
678 want -= diff;
679 } else {
680 iter->rt_runtime -= want;
681 want -= want;
682 }
683 raw_spin_unlock(&iter->rt_runtime_lock);
684
685 if (!want)
686 break;
687 }
688
689 raw_spin_lock(&rt_rq->rt_runtime_lock);
690 /*
691 * We cannot be left wanting - that would mean some runtime
692 * leaked out of the system.
693 */
694 BUG_ON(want);
695balanced:
696 /*
697 * Disable all the borrow logic by pretending we have inf
698 * runtime - in which case borrowing doesn't make sense.
699 */
700 rt_rq->rt_runtime = RUNTIME_INF;
701 rt_rq->rt_throttled = 0;
702 raw_spin_unlock(&rt_rq->rt_runtime_lock);
703 raw_spin_unlock(&rt_b->rt_runtime_lock);
704 }
705}
706
707static void __enable_runtime(struct rq *rq)
708{
709 rt_rq_iter_t iter;
710 struct rt_rq *rt_rq;
711
712 if (unlikely(!scheduler_running))
713 return;
714
715 /*
716 * Reset each runqueue's bandwidth settings
717 */
718 for_each_rt_rq(rt_rq, iter, rq) {
719 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
720
721 raw_spin_lock(&rt_b->rt_runtime_lock);
722 raw_spin_lock(&rt_rq->rt_runtime_lock);
723 rt_rq->rt_runtime = rt_b->rt_runtime;
724 rt_rq->rt_time = 0;
725 rt_rq->rt_throttled = 0;
726 raw_spin_unlock(&rt_rq->rt_runtime_lock);
727 raw_spin_unlock(&rt_b->rt_runtime_lock);
728 }
729}
730
731static int balance_runtime(struct rt_rq *rt_rq)
732{
733 int more = 0;
734
735 if (!sched_feat(RT_RUNTIME_SHARE))
736 return more;
737
738 if (rt_rq->rt_time > rt_rq->rt_runtime) {
739 raw_spin_unlock(&rt_rq->rt_runtime_lock);
740 more = do_balance_runtime(rt_rq);
741 raw_spin_lock(&rt_rq->rt_runtime_lock);
742 }
743
744 return more;
745}
746#else /* !CONFIG_SMP */
747static inline int balance_runtime(struct rt_rq *rt_rq)
748{
749 return 0;
750}
751#endif /* CONFIG_SMP */
752
753static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
754{
755 int i, idle = 1, throttled = 0;
756 const struct cpumask *span;
757
758 span = sched_rt_period_mask();
759#ifdef CONFIG_RT_GROUP_SCHED
760 /*
761 * FIXME: isolated CPUs should really leave the root task group,
762 * whether they are isolcpus or were isolated via cpusets, lest
763 * the timer run on a CPU which does not service all runqueues,
764 * potentially leaving other CPUs indefinitely throttled. If
765 * isolation is really required, the user will turn the throttle
766 * off to kill the perturbations it causes anyway. Meanwhile,
767 * this maintains functionality for boot and/or troubleshooting.
768 */
769 if (rt_b == &root_task_group.rt_bandwidth)
770 span = cpu_online_mask;
771#endif
772 for_each_cpu(i, span) {
773 int enqueue = 0;
774 struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
775 struct rq *rq = rq_of_rt_rq(rt_rq);
776
777 raw_spin_lock(&rq->lock);
778 if (rt_rq->rt_time) {
779 u64 runtime;
780
781 raw_spin_lock(&rt_rq->rt_runtime_lock);
782 if (rt_rq->rt_throttled)
783 balance_runtime(rt_rq);
784 runtime = rt_rq->rt_runtime;
785 rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
786 if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
787 rt_rq->rt_throttled = 0;
788 enqueue = 1;
789
790 /*
791 * Force a clock update if the CPU was idle,
792 * lest wakeup -> unthrottle time accumulate.
793 */
794 if (rt_rq->rt_nr_running && rq->curr == rq->idle)
795 rq->skip_clock_update = -1;
796 }
797 if (rt_rq->rt_time || rt_rq->rt_nr_running)
798 idle = 0;
799 raw_spin_unlock(&rt_rq->rt_runtime_lock);
800 } else if (rt_rq->rt_nr_running) {
801 idle = 0;
802 if (!rt_rq_throttled(rt_rq))
803 enqueue = 1;
804 }
805 if (rt_rq->rt_throttled)
806 throttled = 1;
807
808 if (enqueue)
809 sched_rt_rq_enqueue(rt_rq);
810 raw_spin_unlock(&rq->lock);
811 }
812
813 if (!throttled && (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF))
814 return 1;
815
816 return idle;
817}
818
819static inline int rt_se_prio(struct sched_rt_entity *rt_se)
820{
821#ifdef CONFIG_RT_GROUP_SCHED
822 struct rt_rq *rt_rq = group_rt_rq(rt_se);
823
824 if (rt_rq)
825 return rt_rq->highest_prio.curr;
826#endif
827
828 return rt_task_of(rt_se)->prio;
829}
830
831static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
832{
833 u64 runtime = sched_rt_runtime(rt_rq);
834
835 if (rt_rq->rt_throttled)
836 return rt_rq_throttled(rt_rq);
837
838 if (runtime >= sched_rt_period(rt_rq))
839 return 0;
840
841 balance_runtime(rt_rq);
842 runtime = sched_rt_runtime(rt_rq);
843 if (runtime == RUNTIME_INF)
844 return 0;
845
846 if (rt_rq->rt_time > runtime) {
847 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
848
849 /*
850 * Don't actually throttle groups that have no runtime assigned
851 * but accrue some time due to boosting.
852 */
853 if (likely(rt_b->rt_runtime)) {
854 static bool once = false;
855
856 rt_rq->rt_throttled = 1;
857
858 if (!once) {
859 once = true;
860 printk_sched("sched: RT throttling activated\n");
861 }
862 } else {
863 /*
864 * In case we did anyway, make it go away,
865 * replenishment is a joke, since it will replenish us
866 * with exactly 0 ns.
867 */
868 rt_rq->rt_time = 0;
869 }
870
871 if (rt_rq_throttled(rt_rq)) {
872 sched_rt_rq_dequeue(rt_rq);
873 return 1;
874 }
875 }
876
877 return 0;
878}
879
880/*
881 * Update the current task's runtime statistics. Skip current tasks that
882 * are not in our scheduling class.
883 */
884static void update_curr_rt(struct rq *rq)
885{
886 struct task_struct *curr = rq->curr;
887 struct sched_rt_entity *rt_se = &curr->rt;
888 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
889 u64 delta_exec;
890
891 if (curr->sched_class != &rt_sched_class)
892 return;
893
894 delta_exec = rq_clock_task(rq) - curr->se.exec_start;
895 if (unlikely((s64)delta_exec <= 0))
896 return;
897
898 schedstat_set(curr->se.statistics.exec_max,
899 max(curr->se.statistics.exec_max, delta_exec));
900
901 curr->se.sum_exec_runtime += delta_exec;
902 account_group_exec_runtime(curr, delta_exec);
903
904 curr->se.exec_start = rq_clock_task(rq);
905 cpuacct_charge(curr, delta_exec);
906
907 sched_rt_avg_update(rq, delta_exec);
908
909 if (!rt_bandwidth_enabled())
910 return;
911
912 for_each_sched_rt_entity(rt_se) {
913 rt_rq = rt_rq_of_se(rt_se);
914
915 if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
916 raw_spin_lock(&rt_rq->rt_runtime_lock);
917 rt_rq->rt_time += delta_exec;
918 if (sched_rt_runtime_exceeded(rt_rq))
919 resched_task(curr);
920 raw_spin_unlock(&rt_rq->rt_runtime_lock);
921 }
922 }
923}
924
925#if defined CONFIG_SMP
926
927static void
928inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
929{
930 struct rq *rq = rq_of_rt_rq(rt_rq);
931
932#ifdef CONFIG_RT_GROUP_SCHED
933 /*
934 * Change rq's cpupri only if rt_rq is the top queue.
935 */
936 if (&rq->rt != rt_rq)
937 return;
938#endif
939 if (rq->online && prio < prev_prio)
940 cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
941}
942
943static void
944dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
945{
946 struct rq *rq = rq_of_rt_rq(rt_rq);
947
948#ifdef CONFIG_RT_GROUP_SCHED
949 /*
950 * Change rq's cpupri only if rt_rq is the top queue.
951 */
952 if (&rq->rt != rt_rq)
953 return;
954#endif
955 if (rq->online && rt_rq->highest_prio.curr != prev_prio)
956 cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
957}
958
959#else /* CONFIG_SMP */
960
961static inline
962void inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
963static inline
964void dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
965
966#endif /* CONFIG_SMP */
967
968#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
969static void
970inc_rt_prio(struct rt_rq *rt_rq, int prio)
971{
972 int prev_prio = rt_rq->highest_prio.curr;
973
974 if (prio < prev_prio)
975 rt_rq->highest_prio.curr = prio;
976
977 inc_rt_prio_smp(rt_rq, prio, prev_prio);
978}
979
980static void
981dec_rt_prio(struct rt_rq *rt_rq, int prio)
982{
983 int prev_prio = rt_rq->highest_prio.curr;
984
985 if (rt_rq->rt_nr_running) {
986
987 WARN_ON(prio < prev_prio);
988
989 /*
990 * This may have been our highest task, and therefore
991 * we may have some recomputation to do
992 */
993 if (prio == prev_prio) {
994 struct rt_prio_array *array = &rt_rq->active;
995
996 rt_rq->highest_prio.curr =
997 sched_find_first_bit(array->bitmap);
998 }
999
1000 } else
1001 rt_rq->highest_prio.curr = MAX_RT_PRIO;
1002
1003 dec_rt_prio_smp(rt_rq, prio, prev_prio);
1004}
1005
1006#else
1007
1008static inline void inc_rt_prio(struct rt_rq *rt_rq, int prio) {}
1009static inline void dec_rt_prio(struct rt_rq *rt_rq, int prio) {}
1010
1011#endif /* CONFIG_SMP || CONFIG_RT_GROUP_SCHED */
1012
1013#ifdef CONFIG_RT_GROUP_SCHED
1014
1015static void
1016inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1017{
1018 if (rt_se_boosted(rt_se))
1019 rt_rq->rt_nr_boosted++;
1020
1021 if (rt_rq->tg)
1022 start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
1023}
1024
1025static void
1026dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1027{
1028 if (rt_se_boosted(rt_se))
1029 rt_rq->rt_nr_boosted--;
1030
1031 WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
1032}
1033
1034#else /* CONFIG_RT_GROUP_SCHED */
1035
1036static void
1037inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1038{
1039 start_rt_bandwidth(&def_rt_bandwidth);
1040}
1041
1042static inline
1043void dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) {}
1044
1045#endif /* CONFIG_RT_GROUP_SCHED */
1046
1047static inline
1048void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1049{
1050 int prio = rt_se_prio(rt_se);
1051
1052 WARN_ON(!rt_prio(prio));
1053 rt_rq->rt_nr_running++;
1054
1055 inc_rt_prio(rt_rq, prio);
1056 inc_rt_migration(rt_se, rt_rq);
1057 inc_rt_group(rt_se, rt_rq);
1058}
1059
1060static inline
1061void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1062{
1063 WARN_ON(!rt_prio(rt_se_prio(rt_se)));
1064 WARN_ON(!rt_rq->rt_nr_running);
1065 rt_rq->rt_nr_running--;
1066
1067 dec_rt_prio(rt_rq, rt_se_prio(rt_se));
1068 dec_rt_migration(rt_se, rt_rq);
1069 dec_rt_group(rt_se, rt_rq);
1070}
1071
1072static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
1073{
1074 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
1075 struct rt_prio_array *array = &rt_rq->active;
1076 struct rt_rq *group_rq = group_rt_rq(rt_se);
1077 struct list_head *queue = array->queue + rt_se_prio(rt_se);
1078
1079 /*
1080 * Don't enqueue the group if its throttled, or when empty.
1081 * The latter is a consequence of the former when a child group
1082 * get throttled and the current group doesn't have any other
1083 * active members.
1084 */
1085 if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
1086 return;
1087
1088 if (head)
1089 list_add(&rt_se->run_list, queue);
1090 else
1091 list_add_tail(&rt_se->run_list, queue);
1092 __set_bit(rt_se_prio(rt_se), array->bitmap);
1093
1094 inc_rt_tasks(rt_se, rt_rq);
1095}
1096
1097static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
1098{
1099 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
1100 struct rt_prio_array *array = &rt_rq->active;
1101
1102 list_del_init(&rt_se->run_list);
1103 if (list_empty(array->queue + rt_se_prio(rt_se)))
1104 __clear_bit(rt_se_prio(rt_se), array->bitmap);
1105
1106 dec_rt_tasks(rt_se, rt_rq);
1107}
1108
1109/*
1110 * Because the prio of an upper entry depends on the lower
1111 * entries, we must remove entries top - down.
1112 */
1113static void dequeue_rt_stack(struct sched_rt_entity *rt_se)
1114{
1115 struct sched_rt_entity *back = NULL;
1116
1117 for_each_sched_rt_entity(rt_se) {
1118 rt_se->back = back;
1119 back = rt_se;
1120 }
1121
1122 for (rt_se = back; rt_se; rt_se = rt_se->back) {
1123 if (on_rt_rq(rt_se))
1124 __dequeue_rt_entity(rt_se);
1125 }
1126}
1127
1128static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
1129{
1130 dequeue_rt_stack(rt_se);
1131 for_each_sched_rt_entity(rt_se)
1132 __enqueue_rt_entity(rt_se, head);
1133}
1134
1135static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
1136{
1137 dequeue_rt_stack(rt_se);
1138
1139 for_each_sched_rt_entity(rt_se) {
1140 struct rt_rq *rt_rq = group_rt_rq(rt_se);
1141
1142 if (rt_rq && rt_rq->rt_nr_running)
1143 __enqueue_rt_entity(rt_se, false);
1144 }
1145}
1146
1147/*
1148 * Adding/removing a task to/from a priority array:
1149 */
1150static void
1151enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
1152{
1153 struct sched_rt_entity *rt_se = &p->rt;
1154
1155 if (flags & ENQUEUE_WAKEUP)
1156 rt_se->timeout = 0;
1157
1158 enqueue_rt_entity(rt_se, flags & ENQUEUE_HEAD);
1159
1160 if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
1161 enqueue_pushable_task(rq, p);
1162
1163 inc_nr_running(rq);
1164}
1165
1166static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
1167{
1168 struct sched_rt_entity *rt_se = &p->rt;
1169
1170 update_curr_rt(rq);
1171 dequeue_rt_entity(rt_se);
1172
1173 dequeue_pushable_task(rq, p);
1174
1175 dec_nr_running(rq);
1176}
1177
1178/*
1179 * Put task to the head or the end of the run list without the overhead of
1180 * dequeue followed by enqueue.
1181 */
1182static void
1183requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
1184{
1185 if (on_rt_rq(rt_se)) {
1186 struct rt_prio_array *array = &rt_rq->active;
1187 struct list_head *queue = array->queue + rt_se_prio(rt_se);
1188
1189 if (head)
1190 list_move(&rt_se->run_list, queue);
1191 else
1192 list_move_tail(&rt_se->run_list, queue);
1193 }
1194}
1195
1196static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
1197{
1198 struct sched_rt_entity *rt_se = &p->rt;
1199 struct rt_rq *rt_rq;
1200
1201 for_each_sched_rt_entity(rt_se) {
1202 rt_rq = rt_rq_of_se(rt_se);
1203 requeue_rt_entity(rt_rq, rt_se, head);
1204 }
1205}
1206
1207static void yield_task_rt(struct rq *rq)
1208{
1209 requeue_task_rt(rq, rq->curr, 0);
1210}
1211
1212#ifdef CONFIG_SMP
1213static int find_lowest_rq(struct task_struct *task);
1214
1215static int
1216select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
1217{
1218 struct task_struct *curr;
1219 struct rq *rq;
1220
1221 if (p->nr_cpus_allowed == 1)
1222 goto out;
1223
1224 /* For anything but wake ups, just return the task_cpu */
1225 if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
1226 goto out;
1227
1228 rq = cpu_rq(cpu);
1229
1230 rcu_read_lock();
1231 curr = ACCESS_ONCE(rq->curr); /* unlocked access */
1232
1233 /*
1234 * If the current task on @p's runqueue is an RT task, then
1235 * try to see if we can wake this RT task up on another
1236 * runqueue. Otherwise simply start this RT task
1237 * on its current runqueue.
1238 *
1239 * We want to avoid overloading runqueues. If the woken
1240 * task is a higher priority, then it will stay on this CPU
1241 * and the lower prio task should be moved to another CPU.
1242 * Even though this will probably make the lower prio task
1243 * lose its cache, we do not want to bounce a higher task
1244 * around just because it gave up its CPU, perhaps for a
1245 * lock?
1246 *
1247 * For equal prio tasks, we just let the scheduler sort it out.
1248 *
1249 * Otherwise, just let it ride on the affined RQ and the
1250 * post-schedule router will push the preempted task away
1251 *
1252 * This test is optimistic, if we get it wrong the load-balancer
1253 * will have to sort it out.
1254 */
1255 if (curr && unlikely(rt_task(curr)) &&
1256 (curr->nr_cpus_allowed < 2 ||
1257 curr->prio <= p->prio)) {
1258 int target = find_lowest_rq(p);
1259
1260 if (target != -1)
1261 cpu = target;
1262 }
1263 rcu_read_unlock();
1264
1265out:
1266 return cpu;
1267}
1268
1269static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
1270{
1271 if (rq->curr->nr_cpus_allowed == 1)
1272 return;
1273
1274 if (p->nr_cpus_allowed != 1
1275 && cpupri_find(&rq->rd->cpupri, p, NULL))
1276 return;
1277
1278 if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
1279 return;
1280
1281 /*
1282 * There appears to be other cpus that can accept
1283 * current and none to run 'p', so lets reschedule
1284 * to try and push current away:
1285 */
1286 requeue_task_rt(rq, p, 1);
1287 resched_task(rq->curr);
1288}
1289
1290#endif /* CONFIG_SMP */
1291
1292/*
1293 * Preempt the current task with a newly woken task if needed:
1294 */
1295static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flags)
1296{
1297 if (p->prio < rq->curr->prio) {
1298 resched_task(rq->curr);
1299 return;
1300 }
1301
1302#ifdef CONFIG_SMP
1303 /*
1304 * If:
1305 *
1306 * - the newly woken task is of equal priority to the current task
1307 * - the newly woken task is non-migratable while current is migratable
1308 * - current will be preempted on the next reschedule
1309 *
1310 * we should check to see if current can readily move to a different
1311 * cpu. If so, we will reschedule to allow the push logic to try
1312 * to move current somewhere else, making room for our non-migratable
1313 * task.
1314 */
1315 if (p->prio == rq->curr->prio && !test_tsk_need_resched(rq->curr))
1316 check_preempt_equal_prio(rq, p);
1317#endif
1318}
1319
1320static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
1321 struct rt_rq *rt_rq)
1322{
1323 struct rt_prio_array *array = &rt_rq->active;
1324 struct sched_rt_entity *next = NULL;
1325 struct list_head *queue;
1326 int idx;
1327
1328 idx = sched_find_first_bit(array->bitmap);
1329 BUG_ON(idx >= MAX_RT_PRIO);
1330
1331 queue = array->queue + idx;
1332 next = list_entry(queue->next, struct sched_rt_entity, run_list);
1333
1334 return next;
1335}
1336
1337static struct task_struct *_pick_next_task_rt(struct rq *rq)
1338{
1339 struct sched_rt_entity *rt_se;
1340 struct task_struct *p;
1341 struct rt_rq *rt_rq = &rq->rt;
1342
1343 do {
1344 rt_se = pick_next_rt_entity(rq, rt_rq);
1345 BUG_ON(!rt_se);
1346 rt_rq = group_rt_rq(rt_se);
1347 } while (rt_rq);
1348
1349 p = rt_task_of(rt_se);
1350 p->se.exec_start = rq_clock_task(rq);
1351
1352 return p;
1353}
1354
1355static struct task_struct *
1356pick_next_task_rt(struct rq *rq, struct task_struct *prev)
1357{
1358 struct task_struct *p;
1359 struct rt_rq *rt_rq = &rq->rt;
1360
1361 if (need_pull_rt_task(rq, prev)) {
1362 pull_rt_task(rq);
1363 /*
1364 * pull_rt_task() can drop (and re-acquire) rq->lock; this
1365 * means a dl or stop task can slip in, in which case we need
1366 * to re-start task selection.
1367 */
1368 if (unlikely((rq->stop && rq->stop->on_rq) ||
1369 rq->dl.dl_nr_running))
1370 return RETRY_TASK;
1371 }
1372
1373 /*
1374 * We may dequeue prev's rt_rq in put_prev_task().
1375 * So, we update time before rt_nr_running check.
1376 */
1377 if (prev->sched_class == &rt_sched_class)
1378 update_curr_rt(rq);
1379
1380 if (!rt_rq->rt_nr_running)
1381 return NULL;
1382
1383 if (rt_rq_throttled(rt_rq))
1384 return NULL;
1385
1386 put_prev_task(rq, prev);
1387
1388 p = _pick_next_task_rt(rq);
1389
1390 /* The running task is never eligible for pushing */
1391 if (p)
1392 dequeue_pushable_task(rq, p);
1393
1394 set_post_schedule(rq);
1395
1396 return p;
1397}
1398
1399static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
1400{
1401 update_curr_rt(rq);
1402
1403 /*
1404 * The previous task needs to be made eligible for pushing
1405 * if it is still active
1406 */
1407 if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1)
1408 enqueue_pushable_task(rq, p);
1409}
1410
1411#ifdef CONFIG_SMP
1412
1413/* Only try algorithms three times */
1414#define RT_MAX_TRIES 3
1415
1416static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
1417{
1418 if (!task_running(rq, p) &&
1419 cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
1420 return 1;
1421 return 0;
1422}
1423
1424/*
1425 * Return the highest pushable rq's task, which is suitable to be executed
1426 * on the cpu, NULL otherwise
1427 */
1428static struct task_struct *pick_highest_pushable_task(struct rq *rq, int cpu)
1429{
1430 struct plist_head *head = &rq->rt.pushable_tasks;
1431 struct task_struct *p;
1432
1433 if (!has_pushable_tasks(rq))
1434 return NULL;
1435
1436 plist_for_each_entry(p, head, pushable_tasks) {
1437 if (pick_rt_task(rq, p, cpu))
1438 return p;
1439 }
1440
1441 return NULL;
1442}
1443
1444static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
1445
1446static int find_lowest_rq(struct task_struct *task)
1447{
1448 struct sched_domain *sd;
1449 struct cpumask *lowest_mask = __get_cpu_var(local_cpu_mask);
1450 int this_cpu = smp_processor_id();
1451 int cpu = task_cpu(task);
1452
1453 /* Make sure the mask is initialized first */
1454 if (unlikely(!lowest_mask))
1455 return -1;
1456
1457 if (task->nr_cpus_allowed == 1)
1458 return -1; /* No other targets possible */
1459
1460 if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
1461 return -1; /* No targets found */
1462
1463 /*
1464 * At this point we have built a mask of cpus representing the
1465 * lowest priority tasks in the system. Now we want to elect
1466 * the best one based on our affinity and topology.
1467 *
1468 * We prioritize the last cpu that the task executed on since
1469 * it is most likely cache-hot in that location.
1470 */
1471 if (cpumask_test_cpu(cpu, lowest_mask))
1472 return cpu;
1473
1474 /*
1475 * Otherwise, we consult the sched_domains span maps to figure
1476 * out which cpu is logically closest to our hot cache data.
1477 */
1478 if (!cpumask_test_cpu(this_cpu, lowest_mask))
1479 this_cpu = -1; /* Skip this_cpu opt if not among lowest */
1480
1481 rcu_read_lock();
1482 for_each_domain(cpu, sd) {
1483 if (sd->flags & SD_WAKE_AFFINE) {
1484 int best_cpu;
1485
1486 /*
1487 * "this_cpu" is cheaper to preempt than a
1488 * remote processor.
1489 */
1490 if (this_cpu != -1 &&
1491 cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
1492 rcu_read_unlock();
1493 return this_cpu;
1494 }
1495
1496 best_cpu = cpumask_first_and(lowest_mask,
1497 sched_domain_span(sd));
1498 if (best_cpu < nr_cpu_ids) {
1499 rcu_read_unlock();
1500 return best_cpu;
1501 }
1502 }
1503 }
1504 rcu_read_unlock();
1505
1506 /*
1507 * And finally, if there were no matches within the domains
1508 * just give the caller *something* to work with from the compatible
1509 * locations.
1510 */
1511 if (this_cpu != -1)
1512 return this_cpu;
1513
1514 cpu = cpumask_any(lowest_mask);
1515 if (cpu < nr_cpu_ids)
1516 return cpu;
1517 return -1;
1518}
1519
1520/* Will lock the rq it finds */
1521static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1522{
1523 struct rq *lowest_rq = NULL;
1524 int tries;
1525 int cpu;
1526
1527 for (tries = 0; tries < RT_MAX_TRIES; tries++) {
1528 cpu = find_lowest_rq(task);
1529
1530 if ((cpu == -1) || (cpu == rq->cpu))
1531 break;
1532
1533 lowest_rq = cpu_rq(cpu);
1534
1535 /* if the prio of this runqueue changed, try again */
1536 if (double_lock_balance(rq, lowest_rq)) {
1537 /*
1538 * We had to unlock the run queue. In
1539 * the mean time, task could have
1540 * migrated already or had its affinity changed.
1541 * Also make sure that it wasn't scheduled on its rq.
1542 */
1543 if (unlikely(task_rq(task) != rq ||
1544 !cpumask_test_cpu(lowest_rq->cpu,
1545 tsk_cpus_allowed(task)) ||
1546 task_running(rq, task) ||
1547 !task->on_rq)) {
1548
1549 double_unlock_balance(rq, lowest_rq);
1550 lowest_rq = NULL;
1551 break;
1552 }
1553 }
1554
1555 /* If this rq is still suitable use it. */
1556 if (lowest_rq->rt.highest_prio.curr > task->prio)
1557 break;
1558
1559 /* try again */
1560 double_unlock_balance(rq, lowest_rq);
1561 lowest_rq = NULL;
1562 }
1563
1564 return lowest_rq;
1565}
1566
1567static struct task_struct *pick_next_pushable_task(struct rq *rq)
1568{
1569 struct task_struct *p;
1570
1571 if (!has_pushable_tasks(rq))
1572 return NULL;
1573
1574 p = plist_first_entry(&rq->rt.pushable_tasks,
1575 struct task_struct, pushable_tasks);
1576
1577 BUG_ON(rq->cpu != task_cpu(p));
1578 BUG_ON(task_current(rq, p));
1579 BUG_ON(p->nr_cpus_allowed <= 1);
1580
1581 BUG_ON(!p->on_rq);
1582 BUG_ON(!rt_task(p));
1583
1584 return p;
1585}
1586
1587/*
1588 * If the current CPU has more than one RT task, see if the non
1589 * running task can migrate over to a CPU that is running a task
1590 * of lesser priority.
1591 */
1592static int push_rt_task(struct rq *rq)
1593{
1594 struct task_struct *next_task;
1595 struct rq *lowest_rq;
1596 int ret = 0;
1597
1598 if (!rq->rt.overloaded)
1599 return 0;
1600
1601 next_task = pick_next_pushable_task(rq);
1602 if (!next_task)
1603 return 0;
1604
1605retry:
1606 if (unlikely(next_task == rq->curr)) {
1607 WARN_ON(1);
1608 return 0;
1609 }
1610
1611 /*
1612 * It's possible that the next_task slipped in of
1613 * higher priority than current. If that's the case
1614 * just reschedule current.
1615 */
1616 if (unlikely(next_task->prio < rq->curr->prio)) {
1617 resched_task(rq->curr);
1618 return 0;
1619 }
1620
1621 /* We might release rq lock */
1622 get_task_struct(next_task);
1623
1624 /* find_lock_lowest_rq locks the rq if found */
1625 lowest_rq = find_lock_lowest_rq(next_task, rq);
1626 if (!lowest_rq) {
1627 struct task_struct *task;
1628 /*
1629 * find_lock_lowest_rq releases rq->lock
1630 * so it is possible that next_task has migrated.
1631 *
1632 * We need to make sure that the task is still on the same
1633 * run-queue and is also still the next task eligible for
1634 * pushing.
1635 */
1636 task = pick_next_pushable_task(rq);
1637 if (task_cpu(next_task) == rq->cpu && task == next_task) {
1638 /*
1639 * The task hasn't migrated, and is still the next
1640 * eligible task, but we failed to find a run-queue
1641 * to push it to. Do not retry in this case, since
1642 * other cpus will pull from us when ready.
1643 */
1644 goto out;
1645 }
1646
1647 if (!task)
1648 /* No more tasks, just exit */
1649 goto out;
1650
1651 /*
1652 * Something has shifted, try again.
1653 */
1654 put_task_struct(next_task);
1655 next_task = task;
1656 goto retry;
1657 }
1658
1659 deactivate_task(rq, next_task, 0);
1660 set_task_cpu(next_task, lowest_rq->cpu);
1661 activate_task(lowest_rq, next_task, 0);
1662 ret = 1;
1663
1664 resched_task(lowest_rq->curr);
1665
1666 double_unlock_balance(rq, lowest_rq);
1667
1668out:
1669 put_task_struct(next_task);
1670
1671 return ret;
1672}
1673
1674static void push_rt_tasks(struct rq *rq)
1675{
1676 /* push_rt_task will return true if it moved an RT */
1677 while (push_rt_task(rq))
1678 ;
1679}
1680
1681static int pull_rt_task(struct rq *this_rq)
1682{
1683 int this_cpu = this_rq->cpu, ret = 0, cpu;
1684 struct task_struct *p;
1685 struct rq *src_rq;
1686
1687 if (likely(!rt_overloaded(this_rq)))
1688 return 0;
1689
1690 /*
1691 * Match the barrier from rt_set_overloaded; this guarantees that if we
1692 * see overloaded we must also see the rto_mask bit.
1693 */
1694 smp_rmb();
1695
1696 for_each_cpu(cpu, this_rq->rd->rto_mask) {
1697 if (this_cpu == cpu)
1698 continue;
1699
1700 src_rq = cpu_rq(cpu);
1701
1702 /*
1703 * Don't bother taking the src_rq->lock if the next highest
1704 * task is known to be lower-priority than our current task.
1705 * This may look racy, but if this value is about to go
1706 * logically higher, the src_rq will push this task away.
1707 * And if its going logically lower, we do not care
1708 */
1709 if (src_rq->rt.highest_prio.next >=
1710 this_rq->rt.highest_prio.curr)
1711 continue;
1712
1713 /*
1714 * We can potentially drop this_rq's lock in
1715 * double_lock_balance, and another CPU could
1716 * alter this_rq
1717 */
1718 double_lock_balance(this_rq, src_rq);
1719
1720 /*
1721 * We can pull only a task, which is pushable
1722 * on its rq, and no others.
1723 */
1724 p = pick_highest_pushable_task(src_rq, this_cpu);
1725
1726 /*
1727 * Do we have an RT task that preempts
1728 * the to-be-scheduled task?
1729 */
1730 if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
1731 WARN_ON(p == src_rq->curr);
1732 WARN_ON(!p->on_rq);
1733
1734 /*
1735 * There's a chance that p is higher in priority
1736 * than what's currently running on its cpu.
1737 * This is just that p is wakeing up and hasn't
1738 * had a chance to schedule. We only pull
1739 * p if it is lower in priority than the
1740 * current task on the run queue
1741 */
1742 if (p->prio < src_rq->curr->prio)
1743 goto skip;
1744
1745 ret = 1;
1746
1747 deactivate_task(src_rq, p, 0);
1748 set_task_cpu(p, this_cpu);
1749 activate_task(this_rq, p, 0);
1750 /*
1751 * We continue with the search, just in
1752 * case there's an even higher prio task
1753 * in another runqueue. (low likelihood
1754 * but possible)
1755 */
1756 }
1757skip:
1758 double_unlock_balance(this_rq, src_rq);
1759 }
1760
1761 return ret;
1762}
1763
1764static void post_schedule_rt(struct rq *rq)
1765{
1766 push_rt_tasks(rq);
1767}
1768
1769/*
1770 * If we are not running and we are not going to reschedule soon, we should
1771 * try to push tasks away now
1772 */
1773static void task_woken_rt(struct rq *rq, struct task_struct *p)
1774{
1775 if (!task_running(rq, p) &&
1776 !test_tsk_need_resched(rq->curr) &&
1777 has_pushable_tasks(rq) &&
1778 p->nr_cpus_allowed > 1 &&
1779 (dl_task(rq->curr) || rt_task(rq->curr)) &&
1780 (rq->curr->nr_cpus_allowed < 2 ||
1781 rq->curr->prio <= p->prio))
1782 push_rt_tasks(rq);
1783}
1784
1785static void set_cpus_allowed_rt(struct task_struct *p,
1786 const struct cpumask *new_mask)
1787{
1788 struct rq *rq;
1789 int weight;
1790
1791 BUG_ON(!rt_task(p));
1792
1793 if (!p->on_rq)
1794 return;
1795
1796 weight = cpumask_weight(new_mask);
1797
1798 /*
1799 * Only update if the process changes its state from whether it
1800 * can migrate or not.
1801 */
1802 if ((p->nr_cpus_allowed > 1) == (weight > 1))
1803 return;
1804
1805 rq = task_rq(p);
1806
1807 /*
1808 * The process used to be able to migrate OR it can now migrate
1809 */
1810 if (weight <= 1) {
1811 if (!task_current(rq, p))
1812 dequeue_pushable_task(rq, p);
1813 BUG_ON(!rq->rt.rt_nr_migratory);
1814 rq->rt.rt_nr_migratory--;
1815 } else {
1816 if (!task_current(rq, p))
1817 enqueue_pushable_task(rq, p);
1818 rq->rt.rt_nr_migratory++;
1819 }
1820
1821 update_rt_migration(&rq->rt);
1822}
1823
1824/* Assumes rq->lock is held */
1825static void rq_online_rt(struct rq *rq)
1826{
1827 if (rq->rt.overloaded)
1828 rt_set_overload(rq);
1829
1830 __enable_runtime(rq);
1831
1832 cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
1833}
1834
1835/* Assumes rq->lock is held */
1836static void rq_offline_rt(struct rq *rq)
1837{
1838 if (rq->rt.overloaded)
1839 rt_clear_overload(rq);
1840
1841 __disable_runtime(rq);
1842
1843 cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
1844}
1845
1846/*
1847 * When switch from the rt queue, we bring ourselves to a position
1848 * that we might want to pull RT tasks from other runqueues.
1849 */
1850static void switched_from_rt(struct rq *rq, struct task_struct *p)
1851{
1852 /*
1853 * If there are other RT tasks then we will reschedule
1854 * and the scheduling of the other RT tasks will handle
1855 * the balancing. But if we are the last RT task
1856 * we may need to handle the pulling of RT tasks
1857 * now.
1858 */
1859 if (!p->on_rq || rq->rt.rt_nr_running)
1860 return;
1861
1862 if (pull_rt_task(rq))
1863 resched_task(rq->curr);
1864}
1865
1866void __init init_sched_rt_class(void)
1867{
1868 unsigned int i;
1869
1870 for_each_possible_cpu(i) {
1871 zalloc_cpumask_var_node(&per_cpu(local_cpu_mask, i),
1872 GFP_KERNEL, cpu_to_node(i));
1873 }
1874}
1875#endif /* CONFIG_SMP */
1876
1877/*
1878 * When switching a task to RT, we may overload the runqueue
1879 * with RT tasks. In this case we try to push them off to
1880 * other runqueues.
1881 */
1882static void switched_to_rt(struct rq *rq, struct task_struct *p)
1883{
1884 int check_resched = 1;
1885
1886 /*
1887 * If we are already running, then there's nothing
1888 * that needs to be done. But if we are not running
1889 * we may need to preempt the current running task.
1890 * If that current running task is also an RT task
1891 * then see if we can move to another run queue.
1892 */
1893 if (p->on_rq && rq->curr != p) {
1894#ifdef CONFIG_SMP
1895 if (rq->rt.overloaded && push_rt_task(rq) &&
1896 /* Don't resched if we changed runqueues */
1897 rq != task_rq(p))
1898 check_resched = 0;
1899#endif /* CONFIG_SMP */
1900 if (check_resched && p->prio < rq->curr->prio)
1901 resched_task(rq->curr);
1902 }
1903}
1904
1905/*
1906 * Priority of the task has changed. This may cause
1907 * us to initiate a push or pull.
1908 */
1909static void
1910prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
1911{
1912 if (!p->on_rq)
1913 return;
1914
1915 if (rq->curr == p) {
1916#ifdef CONFIG_SMP
1917 /*
1918 * If our priority decreases while running, we
1919 * may need to pull tasks to this runqueue.
1920 */
1921 if (oldprio < p->prio)
1922 pull_rt_task(rq);
1923 /*
1924 * If there's a higher priority task waiting to run
1925 * then reschedule. Note, the above pull_rt_task
1926 * can release the rq lock and p could migrate.
1927 * Only reschedule if p is still on the same runqueue.
1928 */
1929 if (p->prio > rq->rt.highest_prio.curr && rq->curr == p)
1930 resched_task(p);
1931#else
1932 /* For UP simply resched on drop of prio */
1933 if (oldprio < p->prio)
1934 resched_task(p);
1935#endif /* CONFIG_SMP */
1936 } else {
1937 /*
1938 * This task is not running, but if it is
1939 * greater than the current running task
1940 * then reschedule.
1941 */
1942 if (p->prio < rq->curr->prio)
1943 resched_task(rq->curr);
1944 }
1945}
1946
1947static void watchdog(struct rq *rq, struct task_struct *p)
1948{
1949 unsigned long soft, hard;
1950
1951 /* max may change after cur was read, this will be fixed next tick */
1952 soft = task_rlimit(p, RLIMIT_RTTIME);
1953 hard = task_rlimit_max(p, RLIMIT_RTTIME);
1954
1955 if (soft != RLIM_INFINITY) {
1956 unsigned long next;
1957
1958 if (p->rt.watchdog_stamp != jiffies) {
1959 p->rt.timeout++;
1960 p->rt.watchdog_stamp = jiffies;
1961 }
1962
1963 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
1964 if (p->rt.timeout > next)
1965 p->cputime_expires.sched_exp = p->se.sum_exec_runtime;
1966 }
1967}
1968
1969static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
1970{
1971 struct sched_rt_entity *rt_se = &p->rt;
1972
1973 update_curr_rt(rq);
1974
1975 watchdog(rq, p);
1976
1977 /*
1978 * RR tasks need a special form of timeslice management.
1979 * FIFO tasks have no timeslices.
1980 */
1981 if (p->policy != SCHED_RR)
1982 return;
1983
1984 if (--p->rt.time_slice)
1985 return;
1986
1987 p->rt.time_slice = sched_rr_timeslice;
1988
1989 /*
1990 * Requeue to the end of queue if we (and all of our ancestors) are not
1991 * the only element on the queue
1992 */
1993 for_each_sched_rt_entity(rt_se) {
1994 if (rt_se->run_list.prev != rt_se->run_list.next) {
1995 requeue_task_rt(rq, p, 0);
1996 set_tsk_need_resched(p);
1997 return;
1998 }
1999 }
2000}
2001
2002static void set_curr_task_rt(struct rq *rq)
2003{
2004 struct task_struct *p = rq->curr;
2005
2006 p->se.exec_start = rq_clock_task(rq);
2007
2008 /* The running task is never eligible for pushing */
2009 dequeue_pushable_task(rq, p);
2010}
2011
2012static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
2013{
2014 /*
2015 * Time slice is 0 for SCHED_FIFO tasks
2016 */
2017 if (task->policy == SCHED_RR)
2018 return sched_rr_timeslice;
2019 else
2020 return 0;
2021}
2022
2023const struct sched_class rt_sched_class = {
2024 .next = &fair_sched_class,
2025 .enqueue_task = enqueue_task_rt,
2026 .dequeue_task = dequeue_task_rt,
2027 .yield_task = yield_task_rt,
2028
2029 .check_preempt_curr = check_preempt_curr_rt,
2030
2031 .pick_next_task = pick_next_task_rt,
2032 .put_prev_task = put_prev_task_rt,
2033
2034#ifdef CONFIG_SMP
2035 .select_task_rq = select_task_rq_rt,
2036
2037 .set_cpus_allowed = set_cpus_allowed_rt,
2038 .rq_online = rq_online_rt,
2039 .rq_offline = rq_offline_rt,
2040 .post_schedule = post_schedule_rt,
2041 .task_woken = task_woken_rt,
2042 .switched_from = switched_from_rt,
2043#endif
2044
2045 .set_curr_task = set_curr_task_rt,
2046 .task_tick = task_tick_rt,
2047
2048 .get_rr_interval = get_rr_interval_rt,
2049
2050 .prio_changed = prio_changed_rt,
2051 .switched_to = switched_to_rt,
2052};
2053
2054#ifdef CONFIG_SCHED_DEBUG
2055extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq);
2056
2057void print_rt_stats(struct seq_file *m, int cpu)
2058{
2059 rt_rq_iter_t iter;
2060 struct rt_rq *rt_rq;
2061
2062 rcu_read_lock();
2063 for_each_rt_rq(rt_rq, iter, cpu_rq(cpu))
2064 print_rt_rq(m, cpu, rt_rq);
2065 rcu_read_unlock();
2066}
2067#endif /* CONFIG_SCHED_DEBUG */