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TOMOYO Linux Cross Reference
Linux/kernel/sched_rt.c

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  1 /*
  2  * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
  3  * policies)
  4  */
  5 
  6 #ifdef CONFIG_RT_GROUP_SCHED
  7 
  8 #define rt_entity_is_task(rt_se) (!(rt_se)->my_q)
  9 
 10 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
 11 {
 12 #ifdef CONFIG_SCHED_DEBUG
 13         WARN_ON_ONCE(!rt_entity_is_task(rt_se));
 14 #endif
 15         return container_of(rt_se, struct task_struct, rt);
 16 }
 17 
 18 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
 19 {
 20         return rt_rq->rq;
 21 }
 22 
 23 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
 24 {
 25         return rt_se->rt_rq;
 26 }
 27 
 28 #else /* CONFIG_RT_GROUP_SCHED */
 29 
 30 #define rt_entity_is_task(rt_se) (1)
 31 
 32 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
 33 {
 34         return container_of(rt_se, struct task_struct, rt);
 35 }
 36 
 37 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
 38 {
 39         return container_of(rt_rq, struct rq, rt);
 40 }
 41 
 42 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
 43 {
 44         struct task_struct *p = rt_task_of(rt_se);
 45         struct rq *rq = task_rq(p);
 46 
 47         return &rq->rt;
 48 }
 49 
 50 #endif /* CONFIG_RT_GROUP_SCHED */
 51 
 52 #ifdef CONFIG_SMP
 53 
 54 static inline int rt_overloaded(struct rq *rq)
 55 {
 56         return atomic_read(&rq->rd->rto_count);
 57 }
 58 
 59 static inline void rt_set_overload(struct rq *rq)
 60 {
 61         if (!rq->online)
 62                 return;
 63 
 64         cpumask_set_cpu(rq->cpu, rq->rd->rto_mask);
 65         /*
 66          * Make sure the mask is visible before we set
 67          * the overload count. That is checked to determine
 68          * if we should look at the mask. It would be a shame
 69          * if we looked at the mask, but the mask was not
 70          * updated yet.
 71          */
 72         wmb();
 73         atomic_inc(&rq->rd->rto_count);
 74 }
 75 
 76 static inline void rt_clear_overload(struct rq *rq)
 77 {
 78         if (!rq->online)
 79                 return;
 80 
 81         /* the order here really doesn't matter */
 82         atomic_dec(&rq->rd->rto_count);
 83         cpumask_clear_cpu(rq->cpu, rq->rd->rto_mask);
 84 }
 85 
 86 static void update_rt_migration(struct rt_rq *rt_rq)
 87 {
 88         if (rt_rq->rt_nr_migratory && rt_rq->rt_nr_total > 1) {
 89                 if (!rt_rq->overloaded) {
 90                         rt_set_overload(rq_of_rt_rq(rt_rq));
 91                         rt_rq->overloaded = 1;
 92                 }
 93         } else if (rt_rq->overloaded) {
 94                 rt_clear_overload(rq_of_rt_rq(rt_rq));
 95                 rt_rq->overloaded = 0;
 96         }
 97 }
 98 
 99 static void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
100 {
101         if (!rt_entity_is_task(rt_se))
102                 return;
103 
104         rt_rq = &rq_of_rt_rq(rt_rq)->rt;
105 
106         rt_rq->rt_nr_total++;
107         if (rt_se->nr_cpus_allowed > 1)
108                 rt_rq->rt_nr_migratory++;
109 
110         update_rt_migration(rt_rq);
111 }
112 
113 static void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
114 {
115         if (!rt_entity_is_task(rt_se))
116                 return;
117 
118         rt_rq = &rq_of_rt_rq(rt_rq)->rt;
119 
120         rt_rq->rt_nr_total--;
121         if (rt_se->nr_cpus_allowed > 1)
122                 rt_rq->rt_nr_migratory--;
123 
124         update_rt_migration(rt_rq);
125 }
126 
127 static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
128 {
129         plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
130         plist_node_init(&p->pushable_tasks, p->prio);
131         plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks);
132 }
133 
134 static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
135 {
136         plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
137 }
138 
139 static inline int has_pushable_tasks(struct rq *rq)
140 {
141         return !plist_head_empty(&rq->rt.pushable_tasks);
142 }
143 
144 #else
145 
146 static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
147 {
148 }
149 
150 static inline void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
151 {
152 }
153 
154 static inline
155 void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
156 {
157 }
158 
159 static inline
160 void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
161 {
162 }
163 
164 #endif /* CONFIG_SMP */
165 
166 static inline int on_rt_rq(struct sched_rt_entity *rt_se)
167 {
168         return !list_empty(&rt_se->run_list);
169 }
170 
171 #ifdef CONFIG_RT_GROUP_SCHED
172 
173 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
174 {
175         if (!rt_rq->tg)
176                 return RUNTIME_INF;
177 
178         return rt_rq->rt_runtime;
179 }
180 
181 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
182 {
183         return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
184 }
185 
186 typedef struct task_group *rt_rq_iter_t;
187 
188 #define for_each_rt_rq(rt_rq, iter, rq) \
189         for (iter = list_entry_rcu(task_groups.next, typeof(*iter), list); \
190              (&iter->list != &task_groups) && \
191              (rt_rq = iter->rt_rq[cpu_of(rq)]); \
192              iter = list_entry_rcu(iter->list.next, typeof(*iter), list))
193 
194 static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
195 {
196         list_add_rcu(&rt_rq->leaf_rt_rq_list,
197                         &rq_of_rt_rq(rt_rq)->leaf_rt_rq_list);
198 }
199 
200 static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)
201 {
202         list_del_rcu(&rt_rq->leaf_rt_rq_list);
203 }
204 
205 #define for_each_leaf_rt_rq(rt_rq, rq) \
206         list_for_each_entry_rcu(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
207 
208 #define for_each_sched_rt_entity(rt_se) \
209         for (; rt_se; rt_se = rt_se->parent)
210 
211 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
212 {
213         return rt_se->my_q;
214 }
215 
216 static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head);
217 static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
218 
219 static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
220 {
221         struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
222         struct sched_rt_entity *rt_se;
223 
224         int cpu = cpu_of(rq_of_rt_rq(rt_rq));
225 
226         rt_se = rt_rq->tg->rt_se[cpu];
227 
228         if (rt_rq->rt_nr_running) {
229                 if (rt_se && !on_rt_rq(rt_se))
230                         enqueue_rt_entity(rt_se, false);
231                 if (rt_rq->highest_prio.curr < curr->prio)
232                         resched_task(curr);
233         }
234 }
235 
236 static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
237 {
238         struct sched_rt_entity *rt_se;
239         int cpu = cpu_of(rq_of_rt_rq(rt_rq));
240 
241         rt_se = rt_rq->tg->rt_se[cpu];
242 
243         if (rt_se && on_rt_rq(rt_se))
244                 dequeue_rt_entity(rt_se);
245 }
246 
247 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
248 {
249         return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
250 }
251 
252 static int rt_se_boosted(struct sched_rt_entity *rt_se)
253 {
254         struct rt_rq *rt_rq = group_rt_rq(rt_se);
255         struct task_struct *p;
256 
257         if (rt_rq)
258                 return !!rt_rq->rt_nr_boosted;
259 
260         p = rt_task_of(rt_se);
261         return p->prio != p->normal_prio;
262 }
263 
264 #ifdef CONFIG_SMP
265 static inline const struct cpumask *sched_rt_period_mask(void)
266 {
267         return cpu_rq(smp_processor_id())->rd->span;
268 }
269 #else
270 static inline const struct cpumask *sched_rt_period_mask(void)
271 {
272         return cpu_online_mask;
273 }
274 #endif
275 
276 static inline
277 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
278 {
279         return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
280 }
281 
282 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
283 {
284         return &rt_rq->tg->rt_bandwidth;
285 }
286 
287 #else /* !CONFIG_RT_GROUP_SCHED */
288 
289 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
290 {
291         return rt_rq->rt_runtime;
292 }
293 
294 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
295 {
296         return ktime_to_ns(def_rt_bandwidth.rt_period);
297 }
298 
299 typedef struct rt_rq *rt_rq_iter_t;
300 
301 #define for_each_rt_rq(rt_rq, iter, rq) \
302         for ((void) iter, rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
303 
304 static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
305 {
306 }
307 
308 static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)
309 {
310 }
311 
312 #define for_each_leaf_rt_rq(rt_rq, rq) \
313         for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
314 
315 #define for_each_sched_rt_entity(rt_se) \
316         for (; rt_se; rt_se = NULL)
317 
318 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
319 {
320         return NULL;
321 }
322 
323 static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
324 {
325         if (rt_rq->rt_nr_running)
326                 resched_task(rq_of_rt_rq(rt_rq)->curr);
327 }
328 
329 static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
330 {
331 }
332 
333 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
334 {
335         return rt_rq->rt_throttled;
336 }
337 
338 static inline const struct cpumask *sched_rt_period_mask(void)
339 {
340         return cpu_online_mask;
341 }
342 
343 static inline
344 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
345 {
346         return &cpu_rq(cpu)->rt;
347 }
348 
349 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
350 {
351         return &def_rt_bandwidth;
352 }
353 
354 #endif /* CONFIG_RT_GROUP_SCHED */
355 
356 #ifdef CONFIG_SMP
357 /*
358  * We ran out of runtime, see if we can borrow some from our neighbours.
359  */
360 static int do_balance_runtime(struct rt_rq *rt_rq)
361 {
362         struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
363         struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
364         int i, weight, more = 0;
365         u64 rt_period;
366 
367         weight = cpumask_weight(rd->span);
368 
369         raw_spin_lock(&rt_b->rt_runtime_lock);
370         rt_period = ktime_to_ns(rt_b->rt_period);
371         for_each_cpu(i, rd->span) {
372                 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
373                 s64 diff;
374 
375                 if (iter == rt_rq)
376                         continue;
377 
378                 raw_spin_lock(&iter->rt_runtime_lock);
379                 /*
380                  * Either all rqs have inf runtime and there's nothing to steal
381                  * or __disable_runtime() below sets a specific rq to inf to
382                  * indicate its been disabled and disalow stealing.
383                  */
384                 if (iter->rt_runtime == RUNTIME_INF)
385                         goto next;
386 
387                 /*
388                  * From runqueues with spare time, take 1/n part of their
389                  * spare time, but no more than our period.
390                  */
391                 diff = iter->rt_runtime - iter->rt_time;
392                 if (diff > 0) {
393                         diff = div_u64((u64)diff, weight);
394                         if (rt_rq->rt_runtime + diff > rt_period)
395                                 diff = rt_period - rt_rq->rt_runtime;
396                         iter->rt_runtime -= diff;
397                         rt_rq->rt_runtime += diff;
398                         more = 1;
399                         if (rt_rq->rt_runtime == rt_period) {
400                                 raw_spin_unlock(&iter->rt_runtime_lock);
401                                 break;
402                         }
403                 }
404 next:
405                 raw_spin_unlock(&iter->rt_runtime_lock);
406         }
407         raw_spin_unlock(&rt_b->rt_runtime_lock);
408 
409         return more;
410 }
411 
412 /*
413  * Ensure this RQ takes back all the runtime it lend to its neighbours.
414  */
415 static void __disable_runtime(struct rq *rq)
416 {
417         struct root_domain *rd = rq->rd;
418         rt_rq_iter_t iter;
419         struct rt_rq *rt_rq;
420 
421         if (unlikely(!scheduler_running))
422                 return;
423 
424         for_each_rt_rq(rt_rq, iter, rq) {
425                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
426                 s64 want;
427                 int i;
428 
429                 raw_spin_lock(&rt_b->rt_runtime_lock);
430                 raw_spin_lock(&rt_rq->rt_runtime_lock);
431                 /*
432                  * Either we're all inf and nobody needs to borrow, or we're
433                  * already disabled and thus have nothing to do, or we have
434                  * exactly the right amount of runtime to take out.
435                  */
436                 if (rt_rq->rt_runtime == RUNTIME_INF ||
437                                 rt_rq->rt_runtime == rt_b->rt_runtime)
438                         goto balanced;
439                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
440 
441                 /*
442                  * Calculate the difference between what we started out with
443                  * and what we current have, that's the amount of runtime
444                  * we lend and now have to reclaim.
445                  */
446                 want = rt_b->rt_runtime - rt_rq->rt_runtime;
447 
448                 /*
449                  * Greedy reclaim, take back as much as we can.
450                  */
451                 for_each_cpu(i, rd->span) {
452                         struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
453                         s64 diff;
454 
455                         /*
456                          * Can't reclaim from ourselves or disabled runqueues.
457                          */
458                         if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
459                                 continue;
460 
461                         raw_spin_lock(&iter->rt_runtime_lock);
462                         if (want > 0) {
463                                 diff = min_t(s64, iter->rt_runtime, want);
464                                 iter->rt_runtime -= diff;
465                                 want -= diff;
466                         } else {
467                                 iter->rt_runtime -= want;
468                                 want -= want;
469                         }
470                         raw_spin_unlock(&iter->rt_runtime_lock);
471 
472                         if (!want)
473                                 break;
474                 }
475 
476                 raw_spin_lock(&rt_rq->rt_runtime_lock);
477                 /*
478                  * We cannot be left wanting - that would mean some runtime
479                  * leaked out of the system.
480                  */
481                 BUG_ON(want);
482 balanced:
483                 /*
484                  * Disable all the borrow logic by pretending we have inf
485                  * runtime - in which case borrowing doesn't make sense.
486                  */
487                 rt_rq->rt_runtime = RUNTIME_INF;
488                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
489                 raw_spin_unlock(&rt_b->rt_runtime_lock);
490         }
491 }
492 
493 static void disable_runtime(struct rq *rq)
494 {
495         unsigned long flags;
496 
497         raw_spin_lock_irqsave(&rq->lock, flags);
498         __disable_runtime(rq);
499         raw_spin_unlock_irqrestore(&rq->lock, flags);
500 }
501 
502 static void __enable_runtime(struct rq *rq)
503 {
504         rt_rq_iter_t iter;
505         struct rt_rq *rt_rq;
506 
507         if (unlikely(!scheduler_running))
508                 return;
509 
510         /*
511          * Reset each runqueue's bandwidth settings
512          */
513         for_each_rt_rq(rt_rq, iter, rq) {
514                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
515 
516                 raw_spin_lock(&rt_b->rt_runtime_lock);
517                 raw_spin_lock(&rt_rq->rt_runtime_lock);
518                 rt_rq->rt_runtime = rt_b->rt_runtime;
519                 rt_rq->rt_time = 0;
520                 rt_rq->rt_throttled = 0;
521                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
522                 raw_spin_unlock(&rt_b->rt_runtime_lock);
523         }
524 }
525 
526 static void enable_runtime(struct rq *rq)
527 {
528         unsigned long flags;
529 
530         raw_spin_lock_irqsave(&rq->lock, flags);
531         __enable_runtime(rq);
532         raw_spin_unlock_irqrestore(&rq->lock, flags);
533 }
534 
535 static int balance_runtime(struct rt_rq *rt_rq)
536 {
537         int more = 0;
538 
539         if (rt_rq->rt_time > rt_rq->rt_runtime) {
540                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
541                 more = do_balance_runtime(rt_rq);
542                 raw_spin_lock(&rt_rq->rt_runtime_lock);
543         }
544 
545         return more;
546 }
547 #else /* !CONFIG_SMP */
548 static inline int balance_runtime(struct rt_rq *rt_rq)
549 {
550         return 0;
551 }
552 #endif /* CONFIG_SMP */
553 
554 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
555 {
556         int i, idle = 1;
557         const struct cpumask *span;
558 
559         if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
560                 return 1;
561 
562         span = sched_rt_period_mask();
563         for_each_cpu(i, span) {
564                 int enqueue = 0;
565                 struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
566                 struct rq *rq = rq_of_rt_rq(rt_rq);
567 
568                 raw_spin_lock(&rq->lock);
569                 if (rt_rq->rt_time) {
570                         u64 runtime;
571 
572                         raw_spin_lock(&rt_rq->rt_runtime_lock);
573                         if (rt_rq->rt_throttled)
574                                 balance_runtime(rt_rq);
575                         runtime = rt_rq->rt_runtime;
576                         rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
577                         if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
578                                 rt_rq->rt_throttled = 0;
579                                 enqueue = 1;
580 
581                                 /*
582                                  * Force a clock update if the CPU was idle,
583                                  * lest wakeup -> unthrottle time accumulate.
584                                  */
585                                 if (rt_rq->rt_nr_running && rq->curr == rq->idle)
586                                         rq->skip_clock_update = -1;
587                         }
588                         if (rt_rq->rt_time || rt_rq->rt_nr_running)
589                                 idle = 0;
590                         raw_spin_unlock(&rt_rq->rt_runtime_lock);
591                 } else if (rt_rq->rt_nr_running) {
592                         idle = 0;
593                         if (!rt_rq_throttled(rt_rq))
594                                 enqueue = 1;
595                 }
596 
597                 if (enqueue)
598                         sched_rt_rq_enqueue(rt_rq);
599                 raw_spin_unlock(&rq->lock);
600         }
601 
602         return idle;
603 }
604 
605 static inline int rt_se_prio(struct sched_rt_entity *rt_se)
606 {
607 #ifdef CONFIG_RT_GROUP_SCHED
608         struct rt_rq *rt_rq = group_rt_rq(rt_se);
609 
610         if (rt_rq)
611                 return rt_rq->highest_prio.curr;
612 #endif
613 
614         return rt_task_of(rt_se)->prio;
615 }
616 
617 static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
618 {
619         u64 runtime = sched_rt_runtime(rt_rq);
620 
621         if (rt_rq->rt_throttled)
622                 return rt_rq_throttled(rt_rq);
623 
624         if (sched_rt_runtime(rt_rq) >= sched_rt_period(rt_rq))
625                 return 0;
626 
627         balance_runtime(rt_rq);
628         runtime = sched_rt_runtime(rt_rq);
629         if (runtime == RUNTIME_INF)
630                 return 0;
631 
632         if (rt_rq->rt_time > runtime) {
633                 rt_rq->rt_throttled = 1;
634                 if (rt_rq_throttled(rt_rq)) {
635                         sched_rt_rq_dequeue(rt_rq);
636                         return 1;
637                 }
638         }
639 
640         return 0;
641 }
642 
643 /*
644  * Update the current task's runtime statistics. Skip current tasks that
645  * are not in our scheduling class.
646  */
647 static void update_curr_rt(struct rq *rq)
648 {
649         struct task_struct *curr = rq->curr;
650         struct sched_rt_entity *rt_se = &curr->rt;
651         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
652         u64 delta_exec;
653 
654         if (curr->sched_class != &rt_sched_class)
655                 return;
656 
657         delta_exec = rq->clock_task - curr->se.exec_start;
658         if (unlikely((s64)delta_exec < 0))
659                 delta_exec = 0;
660 
661         schedstat_set(curr->se.statistics.exec_max, max(curr->se.statistics.exec_max, delta_exec));
662 
663         curr->se.sum_exec_runtime += delta_exec;
664         account_group_exec_runtime(curr, delta_exec);
665 
666         curr->se.exec_start = rq->clock_task;
667         cpuacct_charge(curr, delta_exec);
668 
669         sched_rt_avg_update(rq, delta_exec);
670 
671         if (!rt_bandwidth_enabled())
672                 return;
673 
674         for_each_sched_rt_entity(rt_se) {
675                 rt_rq = rt_rq_of_se(rt_se);
676 
677                 if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
678                         raw_spin_lock(&rt_rq->rt_runtime_lock);
679                         rt_rq->rt_time += delta_exec;
680                         if (sched_rt_runtime_exceeded(rt_rq))
681                                 resched_task(curr);
682                         raw_spin_unlock(&rt_rq->rt_runtime_lock);
683                 }
684         }
685 }
686 
687 #if defined CONFIG_SMP
688 
689 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu);
690 
691 static inline int next_prio(struct rq *rq)
692 {
693         struct task_struct *next = pick_next_highest_task_rt(rq, rq->cpu);
694 
695         if (next && rt_prio(next->prio))
696                 return next->prio;
697         else
698                 return MAX_RT_PRIO;
699 }
700 
701 static void
702 inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
703 {
704         struct rq *rq = rq_of_rt_rq(rt_rq);
705 
706         if (prio < prev_prio) {
707 
708                 /*
709                  * If the new task is higher in priority than anything on the
710                  * run-queue, we know that the previous high becomes our
711                  * next-highest.
712                  */
713                 rt_rq->highest_prio.next = prev_prio;
714 
715                 if (rq->online)
716                         cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
717 
718         } else if (prio == rt_rq->highest_prio.curr)
719                 /*
720                  * If the next task is equal in priority to the highest on
721                  * the run-queue, then we implicitly know that the next highest
722                  * task cannot be any lower than current
723                  */
724                 rt_rq->highest_prio.next = prio;
725         else if (prio < rt_rq->highest_prio.next)
726                 /*
727                  * Otherwise, we need to recompute next-highest
728                  */
729                 rt_rq->highest_prio.next = next_prio(rq);
730 }
731 
732 static void
733 dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
734 {
735         struct rq *rq = rq_of_rt_rq(rt_rq);
736 
737         if (rt_rq->rt_nr_running && (prio <= rt_rq->highest_prio.next))
738                 rt_rq->highest_prio.next = next_prio(rq);
739 
740         if (rq->online && rt_rq->highest_prio.curr != prev_prio)
741                 cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
742 }
743 
744 #else /* CONFIG_SMP */
745 
746 static inline
747 void inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
748 static inline
749 void dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
750 
751 #endif /* CONFIG_SMP */
752 
753 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
754 static void
755 inc_rt_prio(struct rt_rq *rt_rq, int prio)
756 {
757         int prev_prio = rt_rq->highest_prio.curr;
758 
759         if (prio < prev_prio)
760                 rt_rq->highest_prio.curr = prio;
761 
762         inc_rt_prio_smp(rt_rq, prio, prev_prio);
763 }
764 
765 static void
766 dec_rt_prio(struct rt_rq *rt_rq, int prio)
767 {
768         int prev_prio = rt_rq->highest_prio.curr;
769 
770         if (rt_rq->rt_nr_running) {
771 
772                 WARN_ON(prio < prev_prio);
773 
774                 /*
775                  * This may have been our highest task, and therefore
776                  * we may have some recomputation to do
777                  */
778                 if (prio == prev_prio) {
779                         struct rt_prio_array *array = &rt_rq->active;
780 
781                         rt_rq->highest_prio.curr =
782                                 sched_find_first_bit(array->bitmap);
783                 }
784 
785         } else
786                 rt_rq->highest_prio.curr = MAX_RT_PRIO;
787 
788         dec_rt_prio_smp(rt_rq, prio, prev_prio);
789 }
790 
791 #else
792 
793 static inline void inc_rt_prio(struct rt_rq *rt_rq, int prio) {}
794 static inline void dec_rt_prio(struct rt_rq *rt_rq, int prio) {}
795 
796 #endif /* CONFIG_SMP || CONFIG_RT_GROUP_SCHED */
797 
798 #ifdef CONFIG_RT_GROUP_SCHED
799 
800 static void
801 inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
802 {
803         if (rt_se_boosted(rt_se))
804                 rt_rq->rt_nr_boosted++;
805 
806         if (rt_rq->tg)
807                 start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
808 }
809 
810 static void
811 dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
812 {
813         if (rt_se_boosted(rt_se))
814                 rt_rq->rt_nr_boosted--;
815 
816         WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
817 }
818 
819 #else /* CONFIG_RT_GROUP_SCHED */
820 
821 static void
822 inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
823 {
824         start_rt_bandwidth(&def_rt_bandwidth);
825 }
826 
827 static inline
828 void dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) {}
829 
830 #endif /* CONFIG_RT_GROUP_SCHED */
831 
832 static inline
833 void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
834 {
835         int prio = rt_se_prio(rt_se);
836 
837         WARN_ON(!rt_prio(prio));
838         rt_rq->rt_nr_running++;
839 
840         inc_rt_prio(rt_rq, prio);
841         inc_rt_migration(rt_se, rt_rq);
842         inc_rt_group(rt_se, rt_rq);
843 }
844 
845 static inline
846 void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
847 {
848         WARN_ON(!rt_prio(rt_se_prio(rt_se)));
849         WARN_ON(!rt_rq->rt_nr_running);
850         rt_rq->rt_nr_running--;
851 
852         dec_rt_prio(rt_rq, rt_se_prio(rt_se));
853         dec_rt_migration(rt_se, rt_rq);
854         dec_rt_group(rt_se, rt_rq);
855 }
856 
857 static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
858 {
859         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
860         struct rt_prio_array *array = &rt_rq->active;
861         struct rt_rq *group_rq = group_rt_rq(rt_se);
862         struct list_head *queue = array->queue + rt_se_prio(rt_se);
863 
864         /*
865          * Don't enqueue the group if its throttled, or when empty.
866          * The latter is a consequence of the former when a child group
867          * get throttled and the current group doesn't have any other
868          * active members.
869          */
870         if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
871                 return;
872 
873         if (!rt_rq->rt_nr_running)
874                 list_add_leaf_rt_rq(rt_rq);
875 
876         if (head)
877                 list_add(&rt_se->run_list, queue);
878         else
879                 list_add_tail(&rt_se->run_list, queue);
880         __set_bit(rt_se_prio(rt_se), array->bitmap);
881 
882         inc_rt_tasks(rt_se, rt_rq);
883 }
884 
885 static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
886 {
887         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
888         struct rt_prio_array *array = &rt_rq->active;
889 
890         list_del_init(&rt_se->run_list);
891         if (list_empty(array->queue + rt_se_prio(rt_se)))
892                 __clear_bit(rt_se_prio(rt_se), array->bitmap);
893 
894         dec_rt_tasks(rt_se, rt_rq);
895         if (!rt_rq->rt_nr_running)
896                 list_del_leaf_rt_rq(rt_rq);
897 }
898 
899 /*
900  * Because the prio of an upper entry depends on the lower
901  * entries, we must remove entries top - down.
902  */
903 static void dequeue_rt_stack(struct sched_rt_entity *rt_se)
904 {
905         struct sched_rt_entity *back = NULL;
906 
907         for_each_sched_rt_entity(rt_se) {
908                 rt_se->back = back;
909                 back = rt_se;
910         }
911 
912         for (rt_se = back; rt_se; rt_se = rt_se->back) {
913                 if (on_rt_rq(rt_se))
914                         __dequeue_rt_entity(rt_se);
915         }
916 }
917 
918 static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
919 {
920         dequeue_rt_stack(rt_se);
921         for_each_sched_rt_entity(rt_se)
922                 __enqueue_rt_entity(rt_se, head);
923 }
924 
925 static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
926 {
927         dequeue_rt_stack(rt_se);
928 
929         for_each_sched_rt_entity(rt_se) {
930                 struct rt_rq *rt_rq = group_rt_rq(rt_se);
931 
932                 if (rt_rq && rt_rq->rt_nr_running)
933                         __enqueue_rt_entity(rt_se, false);
934         }
935 }
936 
937 /*
938  * Adding/removing a task to/from a priority array:
939  */
940 static void
941 enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
942 {
943         struct sched_rt_entity *rt_se = &p->rt;
944 
945         if (flags & ENQUEUE_WAKEUP)
946                 rt_se->timeout = 0;
947 
948         enqueue_rt_entity(rt_se, flags & ENQUEUE_HEAD);
949 
950         if (!task_current(rq, p) && p->rt.nr_cpus_allowed > 1)
951                 enqueue_pushable_task(rq, p);
952 }
953 
954 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
955 {
956         struct sched_rt_entity *rt_se = &p->rt;
957 
958         update_curr_rt(rq);
959         dequeue_rt_entity(rt_se);
960 
961         dequeue_pushable_task(rq, p);
962 }
963 
964 /*
965  * Put task to the end of the run list without the overhead of dequeue
966  * followed by enqueue.
967  */
968 static void
969 requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
970 {
971         if (on_rt_rq(rt_se)) {
972                 struct rt_prio_array *array = &rt_rq->active;
973                 struct list_head *queue = array->queue + rt_se_prio(rt_se);
974 
975                 if (head)
976                         list_move(&rt_se->run_list, queue);
977                 else
978                         list_move_tail(&rt_se->run_list, queue);
979         }
980 }
981 
982 static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
983 {
984         struct sched_rt_entity *rt_se = &p->rt;
985         struct rt_rq *rt_rq;
986 
987         for_each_sched_rt_entity(rt_se) {
988                 rt_rq = rt_rq_of_se(rt_se);
989                 requeue_rt_entity(rt_rq, rt_se, head);
990         }
991 }
992 
993 static void yield_task_rt(struct rq *rq)
994 {
995         requeue_task_rt(rq, rq->curr, 0);
996 }
997 
998 #ifdef CONFIG_SMP
999 static int find_lowest_rq(struct task_struct *task);
1000 
1001 static int
1002 select_task_rq_rt(struct task_struct *p, int sd_flag, int flags)
1003 {
1004         struct task_struct *curr;
1005         struct rq *rq;
1006         int cpu;
1007 
1008         if (sd_flag != SD_BALANCE_WAKE)
1009                 return smp_processor_id();
1010 
1011         cpu = task_cpu(p);
1012         rq = cpu_rq(cpu);
1013 
1014         rcu_read_lock();
1015         curr = ACCESS_ONCE(rq->curr); /* unlocked access */
1016 
1017         /*
1018          * If the current task on @p's runqueue is an RT task, then
1019          * try to see if we can wake this RT task up on another
1020          * runqueue. Otherwise simply start this RT task
1021          * on its current runqueue.
1022          *
1023          * We want to avoid overloading runqueues. If the woken
1024          * task is a higher priority, then it will stay on this CPU
1025          * and the lower prio task should be moved to another CPU.
1026          * Even though this will probably make the lower prio task
1027          * lose its cache, we do not want to bounce a higher task
1028          * around just because it gave up its CPU, perhaps for a
1029          * lock?
1030          *
1031          * For equal prio tasks, we just let the scheduler sort it out.
1032          *
1033          * Otherwise, just let it ride on the affined RQ and the
1034          * post-schedule router will push the preempted task away
1035          *
1036          * This test is optimistic, if we get it wrong the load-balancer
1037          * will have to sort it out.
1038          */
1039         if (curr && unlikely(rt_task(curr)) &&
1040             (curr->rt.nr_cpus_allowed < 2 ||
1041              curr->prio <= p->prio) &&
1042             (p->rt.nr_cpus_allowed > 1)) {
1043                 int target = find_lowest_rq(p);
1044 
1045                 if (target != -1)
1046                         cpu = target;
1047         }
1048         rcu_read_unlock();
1049 
1050         return cpu;
1051 }
1052 
1053 static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
1054 {
1055         if (rq->curr->rt.nr_cpus_allowed == 1)
1056                 return;
1057 
1058         if (p->rt.nr_cpus_allowed != 1
1059             && cpupri_find(&rq->rd->cpupri, p, NULL))
1060                 return;
1061 
1062         if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
1063                 return;
1064 
1065         /*
1066          * There appears to be other cpus that can accept
1067          * current and none to run 'p', so lets reschedule
1068          * to try and push current away:
1069          */
1070         requeue_task_rt(rq, p, 1);
1071         resched_task(rq->curr);
1072 }
1073 
1074 #endif /* CONFIG_SMP */
1075 
1076 /*
1077  * Preempt the current task with a newly woken task if needed:
1078  */
1079 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flags)
1080 {
1081         if (p->prio < rq->curr->prio) {
1082                 resched_task(rq->curr);
1083                 return;
1084         }
1085 
1086 #ifdef CONFIG_SMP
1087         /*
1088          * If:
1089          *
1090          * - the newly woken task is of equal priority to the current task
1091          * - the newly woken task is non-migratable while current is migratable
1092          * - current will be preempted on the next reschedule
1093          *
1094          * we should check to see if current can readily move to a different
1095          * cpu.  If so, we will reschedule to allow the push logic to try
1096          * to move current somewhere else, making room for our non-migratable
1097          * task.
1098          */
1099         if (p->prio == rq->curr->prio && !test_tsk_need_resched(rq->curr))
1100                 check_preempt_equal_prio(rq, p);
1101 #endif
1102 }
1103 
1104 static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
1105                                                    struct rt_rq *rt_rq)
1106 {
1107         struct rt_prio_array *array = &rt_rq->active;
1108         struct sched_rt_entity *next = NULL;
1109         struct list_head *queue;
1110         int idx;
1111 
1112         idx = sched_find_first_bit(array->bitmap);
1113         BUG_ON(idx >= MAX_RT_PRIO);
1114 
1115         queue = array->queue + idx;
1116         next = list_entry(queue->next, struct sched_rt_entity, run_list);
1117 
1118         return next;
1119 }
1120 
1121 static struct task_struct *_pick_next_task_rt(struct rq *rq)
1122 {
1123         struct sched_rt_entity *rt_se;
1124         struct task_struct *p;
1125         struct rt_rq *rt_rq;
1126 
1127         rt_rq = &rq->rt;
1128 
1129         if (unlikely(!rt_rq->rt_nr_running))
1130                 return NULL;
1131 
1132         if (rt_rq_throttled(rt_rq))
1133                 return NULL;
1134 
1135         do {
1136                 rt_se = pick_next_rt_entity(rq, rt_rq);
1137                 BUG_ON(!rt_se);
1138                 rt_rq = group_rt_rq(rt_se);
1139         } while (rt_rq);
1140 
1141         p = rt_task_of(rt_se);
1142         p->se.exec_start = rq->clock_task;
1143 
1144         return p;
1145 }
1146 
1147 static struct task_struct *pick_next_task_rt(struct rq *rq)
1148 {
1149         struct task_struct *p = _pick_next_task_rt(rq);
1150 
1151         /* The running task is never eligible for pushing */
1152         if (p)
1153                 dequeue_pushable_task(rq, p);
1154 
1155 #ifdef CONFIG_SMP
1156         /*
1157          * We detect this state here so that we can avoid taking the RQ
1158          * lock again later if there is no need to push
1159          */
1160         rq->post_schedule = has_pushable_tasks(rq);
1161 #endif
1162 
1163         return p;
1164 }
1165 
1166 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
1167 {
1168         update_curr_rt(rq);
1169         p->se.exec_start = 0;
1170 
1171         /*
1172          * The previous task needs to be made eligible for pushing
1173          * if it is still active
1174          */
1175         if (on_rt_rq(&p->rt) && p->rt.nr_cpus_allowed > 1)
1176                 enqueue_pushable_task(rq, p);
1177 }
1178 
1179 #ifdef CONFIG_SMP
1180 
1181 /* Only try algorithms three times */
1182 #define RT_MAX_TRIES 3
1183 
1184 static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
1185 
1186 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
1187 {
1188         if (!task_running(rq, p) &&
1189             (cpu < 0 || cpumask_test_cpu(cpu, &p->cpus_allowed)) &&
1190             (p->rt.nr_cpus_allowed > 1))
1191                 return 1;
1192         return 0;
1193 }
1194 
1195 /* Return the second highest RT task, NULL otherwise */
1196 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
1197 {
1198         struct task_struct *next = NULL;
1199         struct sched_rt_entity *rt_se;
1200         struct rt_prio_array *array;
1201         struct rt_rq *rt_rq;
1202         int idx;
1203 
1204         for_each_leaf_rt_rq(rt_rq, rq) {
1205                 array = &rt_rq->active;
1206                 idx = sched_find_first_bit(array->bitmap);
1207 next_idx:
1208                 if (idx >= MAX_RT_PRIO)
1209                         continue;
1210                 if (next && next->prio < idx)
1211                         continue;
1212                 list_for_each_entry(rt_se, array->queue + idx, run_list) {
1213                         struct task_struct *p;
1214 
1215                         if (!rt_entity_is_task(rt_se))
1216                                 continue;
1217 
1218                         p = rt_task_of(rt_se);
1219                         if (pick_rt_task(rq, p, cpu)) {
1220                                 next = p;
1221                                 break;
1222                         }
1223                 }
1224                 if (!next) {
1225                         idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
1226                         goto next_idx;
1227                 }
1228         }
1229 
1230         return next;
1231 }
1232 
1233 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
1234 
1235 static int find_lowest_rq(struct task_struct *task)
1236 {
1237         struct sched_domain *sd;
1238         struct cpumask *lowest_mask = __get_cpu_var(local_cpu_mask);
1239         int this_cpu = smp_processor_id();
1240         int cpu      = task_cpu(task);
1241 
1242         /* Make sure the mask is initialized first */
1243         if (unlikely(!lowest_mask))
1244                 return -1;
1245 
1246         if (task->rt.nr_cpus_allowed == 1)
1247                 return -1; /* No other targets possible */
1248 
1249         if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
1250                 return -1; /* No targets found */
1251 
1252         /*
1253          * At this point we have built a mask of cpus representing the
1254          * lowest priority tasks in the system.  Now we want to elect
1255          * the best one based on our affinity and topology.
1256          *
1257          * We prioritize the last cpu that the task executed on since
1258          * it is most likely cache-hot in that location.
1259          */
1260         if (cpumask_test_cpu(cpu, lowest_mask))
1261                 return cpu;
1262 
1263         /*
1264          * Otherwise, we consult the sched_domains span maps to figure
1265          * out which cpu is logically closest to our hot cache data.
1266          */
1267         if (!cpumask_test_cpu(this_cpu, lowest_mask))
1268                 this_cpu = -1; /* Skip this_cpu opt if not among lowest */
1269 
1270         rcu_read_lock();
1271         for_each_domain(cpu, sd) {
1272                 if (sd->flags & SD_WAKE_AFFINE) {
1273                         int best_cpu;
1274 
1275                         /*
1276                          * "this_cpu" is cheaper to preempt than a
1277                          * remote processor.
1278                          */
1279                         if (this_cpu != -1 &&
1280                             cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
1281                                 rcu_read_unlock();
1282                                 return this_cpu;
1283                         }
1284 
1285                         best_cpu = cpumask_first_and(lowest_mask,
1286                                                      sched_domain_span(sd));
1287                         if (best_cpu < nr_cpu_ids) {
1288                                 rcu_read_unlock();
1289                                 return best_cpu;
1290                         }
1291                 }
1292         }
1293         rcu_read_unlock();
1294 
1295         /*
1296          * And finally, if there were no matches within the domains
1297          * just give the caller *something* to work with from the compatible
1298          * locations.
1299          */
1300         if (this_cpu != -1)
1301                 return this_cpu;
1302 
1303         cpu = cpumask_any(lowest_mask);
1304         if (cpu < nr_cpu_ids)
1305                 return cpu;
1306         return -1;
1307 }
1308 
1309 /* Will lock the rq it finds */
1310 static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1311 {
1312         struct rq *lowest_rq = NULL;
1313         int tries;
1314         int cpu;
1315 
1316         for (tries = 0; tries < RT_MAX_TRIES; tries++) {
1317                 cpu = find_lowest_rq(task);
1318 
1319                 if ((cpu == -1) || (cpu == rq->cpu))
1320                         break;
1321 
1322                 lowest_rq = cpu_rq(cpu);
1323 
1324                 /* if the prio of this runqueue changed, try again */
1325                 if (double_lock_balance(rq, lowest_rq)) {
1326                         /*
1327                          * We had to unlock the run queue. In
1328                          * the mean time, task could have
1329                          * migrated already or had its affinity changed.
1330                          * Also make sure that it wasn't scheduled on its rq.
1331                          */
1332                         if (unlikely(task_rq(task) != rq ||
1333                                      !cpumask_test_cpu(lowest_rq->cpu,
1334                                                        &task->cpus_allowed) ||
1335                                      task_running(rq, task) ||
1336                                      !task->on_rq)) {
1337 
1338                                 raw_spin_unlock(&lowest_rq->lock);
1339                                 lowest_rq = NULL;
1340                                 break;
1341                         }
1342                 }
1343 
1344                 /* If this rq is still suitable use it. */
1345                 if (lowest_rq->rt.highest_prio.curr > task->prio)
1346                         break;
1347 
1348                 /* try again */
1349                 double_unlock_balance(rq, lowest_rq);
1350                 lowest_rq = NULL;
1351         }
1352 
1353         return lowest_rq;
1354 }
1355 
1356 static struct task_struct *pick_next_pushable_task(struct rq *rq)
1357 {
1358         struct task_struct *p;
1359 
1360         if (!has_pushable_tasks(rq))
1361                 return NULL;
1362 
1363         p = plist_first_entry(&rq->rt.pushable_tasks,
1364                               struct task_struct, pushable_tasks);
1365 
1366         BUG_ON(rq->cpu != task_cpu(p));
1367         BUG_ON(task_current(rq, p));
1368         BUG_ON(p->rt.nr_cpus_allowed <= 1);
1369 
1370         BUG_ON(!p->on_rq);
1371         BUG_ON(!rt_task(p));
1372 
1373         return p;
1374 }
1375 
1376 /*
1377  * If the current CPU has more than one RT task, see if the non
1378  * running task can migrate over to a CPU that is running a task
1379  * of lesser priority.
1380  */
1381 static int push_rt_task(struct rq *rq)
1382 {
1383         struct task_struct *next_task;
1384         struct rq *lowest_rq;
1385 
1386         if (!rq->rt.overloaded)
1387                 return 0;
1388 
1389         next_task = pick_next_pushable_task(rq);
1390         if (!next_task)
1391                 return 0;
1392 
1393 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1394        if (unlikely(task_running(rq, next_task)))
1395                return 0;
1396 #endif
1397 
1398 retry:
1399         if (unlikely(next_task == rq->curr)) {
1400                 WARN_ON(1);
1401                 return 0;
1402         }
1403 
1404         /*
1405          * It's possible that the next_task slipped in of
1406          * higher priority than current. If that's the case
1407          * just reschedule current.
1408          */
1409         if (unlikely(next_task->prio < rq->curr->prio)) {
1410                 resched_task(rq->curr);
1411                 return 0;
1412         }
1413 
1414         /* We might release rq lock */
1415         get_task_struct(next_task);
1416 
1417         /* find_lock_lowest_rq locks the rq if found */
1418         lowest_rq = find_lock_lowest_rq(next_task, rq);
1419         if (!lowest_rq) {
1420                 struct task_struct *task;
1421                 /*
1422                  * find lock_lowest_rq releases rq->lock
1423                  * so it is possible that next_task has migrated.
1424                  *
1425                  * We need to make sure that the task is still on the same
1426                  * run-queue and is also still the next task eligible for
1427                  * pushing.
1428                  */
1429                 task = pick_next_pushable_task(rq);
1430                 if (task_cpu(next_task) == rq->cpu && task == next_task) {
1431                         /*
1432                          * If we get here, the task hasn't moved at all, but
1433                          * it has failed to push.  We will not try again,
1434                          * since the other cpus will pull from us when they
1435                          * are ready.
1436                          */
1437                         dequeue_pushable_task(rq, next_task);
1438                         goto out;
1439                 }
1440 
1441                 if (!task)
1442                         /* No more tasks, just exit */
1443                         goto out;
1444 
1445                 /*
1446                  * Something has shifted, try again.
1447                  */
1448                 put_task_struct(next_task);
1449                 next_task = task;
1450                 goto retry;
1451         }
1452 
1453         deactivate_task(rq, next_task, 0);
1454         set_task_cpu(next_task, lowest_rq->cpu);
1455         activate_task(lowest_rq, next_task, 0);
1456 
1457         resched_task(lowest_rq->curr);
1458 
1459         double_unlock_balance(rq, lowest_rq);
1460 
1461 out:
1462         put_task_struct(next_task);
1463 
1464         return 1;
1465 }
1466 
1467 static void push_rt_tasks(struct rq *rq)
1468 {
1469         /* push_rt_task will return true if it moved an RT */
1470         while (push_rt_task(rq))
1471                 ;
1472 }
1473 
1474 static int pull_rt_task(struct rq *this_rq)
1475 {
1476         int this_cpu = this_rq->cpu, ret = 0, cpu;
1477         struct task_struct *p;
1478         struct rq *src_rq;
1479 
1480         if (likely(!rt_overloaded(this_rq)))
1481                 return 0;
1482 
1483         for_each_cpu(cpu, this_rq->rd->rto_mask) {
1484                 if (this_cpu == cpu)
1485                         continue;
1486 
1487                 src_rq = cpu_rq(cpu);
1488 
1489                 /*
1490                  * Don't bother taking the src_rq->lock if the next highest
1491                  * task is known to be lower-priority than our current task.
1492                  * This may look racy, but if this value is about to go
1493                  * logically higher, the src_rq will push this task away.
1494                  * And if its going logically lower, we do not care
1495                  */
1496                 if (src_rq->rt.highest_prio.next >=
1497                     this_rq->rt.highest_prio.curr)
1498                         continue;
1499 
1500                 /*
1501                  * We can potentially drop this_rq's lock in
1502                  * double_lock_balance, and another CPU could
1503                  * alter this_rq
1504                  */
1505                 double_lock_balance(this_rq, src_rq);
1506 
1507                 /*
1508                  * Are there still pullable RT tasks?
1509                  */
1510                 if (src_rq->rt.rt_nr_running <= 1)
1511                         goto skip;
1512 
1513                 p = pick_next_highest_task_rt(src_rq, this_cpu);
1514 
1515                 /*
1516                  * Do we have an RT task that preempts
1517                  * the to-be-scheduled task?
1518                  */
1519                 if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
1520                         WARN_ON(p == src_rq->curr);
1521                         WARN_ON(!p->on_rq);
1522 
1523                         /*
1524                          * There's a chance that p is higher in priority
1525                          * than what's currently running on its cpu.
1526                          * This is just that p is wakeing up and hasn't
1527                          * had a chance to schedule. We only pull
1528                          * p if it is lower in priority than the
1529                          * current task on the run queue
1530                          */
1531                         if (p->prio < src_rq->curr->prio)
1532                                 goto skip;
1533 
1534                         ret = 1;
1535 
1536                         deactivate_task(src_rq, p, 0);
1537                         set_task_cpu(p, this_cpu);
1538                         activate_task(this_rq, p, 0);
1539                         /*
1540                          * We continue with the search, just in
1541                          * case there's an even higher prio task
1542                          * in another runqueue. (low likelihood
1543                          * but possible)
1544                          */
1545                 }
1546 skip:
1547                 double_unlock_balance(this_rq, src_rq);
1548         }
1549 
1550         return ret;
1551 }
1552 
1553 static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
1554 {
1555         /* Try to pull RT tasks here if we lower this rq's prio */
1556         if (unlikely(rt_task(prev)) && rq->rt.highest_prio.curr > prev->prio)
1557                 pull_rt_task(rq);
1558 }
1559 
1560 static void post_schedule_rt(struct rq *rq)
1561 {
1562         push_rt_tasks(rq);
1563 }
1564 
1565 /*
1566  * If we are not running and we are not going to reschedule soon, we should
1567  * try to push tasks away now
1568  */
1569 static void task_woken_rt(struct rq *rq, struct task_struct *p)
1570 {
1571         if (!task_running(rq, p) &&
1572             !test_tsk_need_resched(rq->curr) &&
1573             has_pushable_tasks(rq) &&
1574             p->rt.nr_cpus_allowed > 1 &&
1575             rt_task(rq->curr) &&
1576             (rq->curr->rt.nr_cpus_allowed < 2 ||
1577              rq->curr->prio <= p->prio))
1578                 push_rt_tasks(rq);
1579 }
1580 
1581 static void set_cpus_allowed_rt(struct task_struct *p,
1582                                 const struct cpumask *new_mask)
1583 {
1584         int weight = cpumask_weight(new_mask);
1585 
1586         BUG_ON(!rt_task(p));
1587 
1588         /*
1589          * Update the migration status of the RQ if we have an RT task
1590          * which is running AND changing its weight value.
1591          */
1592         if (p->on_rq && (weight != p->rt.nr_cpus_allowed)) {
1593                 struct rq *rq = task_rq(p);
1594 
1595                 if (!task_current(rq, p)) {
1596                         /*
1597                          * Make sure we dequeue this task from the pushable list
1598                          * before going further.  It will either remain off of
1599                          * the list because we are no longer pushable, or it
1600                          * will be requeued.
1601                          */
1602                         if (p->rt.nr_cpus_allowed > 1)
1603                                 dequeue_pushable_task(rq, p);
1604 
1605                         /*
1606                          * Requeue if our weight is changing and still > 1
1607                          */
1608                         if (weight > 1)
1609                                 enqueue_pushable_task(rq, p);
1610 
1611                 }
1612 
1613                 if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
1614                         rq->rt.rt_nr_migratory++;
1615                 } else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
1616                         BUG_ON(!rq->rt.rt_nr_migratory);
1617                         rq->rt.rt_nr_migratory--;
1618                 }
1619 
1620                 update_rt_migration(&rq->rt);
1621         }
1622 
1623         cpumask_copy(&p->cpus_allowed, new_mask);
1624         p->rt.nr_cpus_allowed = weight;
1625 }
1626 
1627 /* Assumes rq->lock is held */
1628 static void rq_online_rt(struct rq *rq)
1629 {
1630         if (rq->rt.overloaded)
1631                 rt_set_overload(rq);
1632 
1633         __enable_runtime(rq);
1634 
1635         cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
1636 }
1637 
1638 /* Assumes rq->lock is held */
1639 static void rq_offline_rt(struct rq *rq)
1640 {
1641         if (rq->rt.overloaded)
1642                 rt_clear_overload(rq);
1643 
1644         __disable_runtime(rq);
1645 
1646         cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
1647 }
1648 
1649 /*
1650  * When switch from the rt queue, we bring ourselves to a position
1651  * that we might want to pull RT tasks from other runqueues.
1652  */
1653 static void switched_from_rt(struct rq *rq, struct task_struct *p)
1654 {
1655         /*
1656          * If there are other RT tasks then we will reschedule
1657          * and the scheduling of the other RT tasks will handle
1658          * the balancing. But if we are the last RT task
1659          * we may need to handle the pulling of RT tasks
1660          * now.
1661          */
1662         if (p->on_rq && !rq->rt.rt_nr_running)
1663                 pull_rt_task(rq);
1664 }
1665 
1666 static inline void init_sched_rt_class(void)
1667 {
1668         unsigned int i;
1669 
1670         for_each_possible_cpu(i)
1671                 zalloc_cpumask_var_node(&per_cpu(local_cpu_mask, i),
1672                                         GFP_KERNEL, cpu_to_node(i));
1673 }
1674 #endif /* CONFIG_SMP */
1675 
1676 /*
1677  * When switching a task to RT, we may overload the runqueue
1678  * with RT tasks. In this case we try to push them off to
1679  * other runqueues.
1680  */
1681 static void switched_to_rt(struct rq *rq, struct task_struct *p)
1682 {
1683         int check_resched = 1;
1684 
1685         /*
1686          * If we are already running, then there's nothing
1687          * that needs to be done. But if we are not running
1688          * we may need to preempt the current running task.
1689          * If that current running task is also an RT task
1690          * then see if we can move to another run queue.
1691          */
1692         if (p->on_rq && rq->curr != p) {
1693 #ifdef CONFIG_SMP
1694                 if (rq->rt.overloaded && push_rt_task(rq) &&
1695                     /* Don't resched if we changed runqueues */
1696                     rq != task_rq(p))
1697                         check_resched = 0;
1698 #endif /* CONFIG_SMP */
1699                 if (check_resched && p->prio < rq->curr->prio)
1700                         resched_task(rq->curr);
1701         }
1702 }
1703 
1704 /*
1705  * Priority of the task has changed. This may cause
1706  * us to initiate a push or pull.
1707  */
1708 static void
1709 prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
1710 {
1711         if (!p->on_rq)
1712                 return;
1713 
1714         if (rq->curr == p) {
1715 #ifdef CONFIG_SMP
1716                 /*
1717                  * If our priority decreases while running, we
1718                  * may need to pull tasks to this runqueue.
1719                  */
1720                 if (oldprio < p->prio)
1721                         pull_rt_task(rq);
1722                 /*
1723                  * If there's a higher priority task waiting to run
1724                  * then reschedule. Note, the above pull_rt_task
1725                  * can release the rq lock and p could migrate.
1726                  * Only reschedule if p is still on the same runqueue.
1727                  */
1728                 if (p->prio > rq->rt.highest_prio.curr && rq->curr == p)
1729                         resched_task(p);
1730 #else
1731                 /* For UP simply resched on drop of prio */
1732                 if (oldprio < p->prio)
1733                         resched_task(p);
1734 #endif /* CONFIG_SMP */
1735         } else {
1736                 /*
1737                  * This task is not running, but if it is
1738                  * greater than the current running task
1739                  * then reschedule.
1740                  */
1741                 if (p->prio < rq->curr->prio)
1742                         resched_task(rq->curr);
1743         }
1744 }
1745 
1746 static void watchdog(struct rq *rq, struct task_struct *p)
1747 {
1748         unsigned long soft, hard;
1749 
1750         /* max may change after cur was read, this will be fixed next tick */
1751         soft = task_rlimit(p, RLIMIT_RTTIME);
1752         hard = task_rlimit_max(p, RLIMIT_RTTIME);
1753 
1754         if (soft != RLIM_INFINITY) {
1755                 unsigned long next;
1756 
1757                 p->rt.timeout++;
1758                 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
1759                 if (p->rt.timeout > next)
1760                         p->cputime_expires.sched_exp = p->se.sum_exec_runtime;
1761         }
1762 }
1763 
1764 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
1765 {
1766         update_curr_rt(rq);
1767 
1768         watchdog(rq, p);
1769 
1770         /*
1771          * RR tasks need a special form of timeslice management.
1772          * FIFO tasks have no timeslices.
1773          */
1774         if (p->policy != SCHED_RR)
1775                 return;
1776 
1777         if (--p->rt.time_slice)
1778                 return;
1779 
1780         p->rt.time_slice = DEF_TIMESLICE;
1781 
1782         /*
1783          * Requeue to the end of queue if we are not the only element
1784          * on the queue:
1785          */
1786         if (p->rt.run_list.prev != p->rt.run_list.next) {
1787                 requeue_task_rt(rq, p, 0);
1788                 set_tsk_need_resched(p);
1789         }
1790 }
1791 
1792 static void set_curr_task_rt(struct rq *rq)
1793 {
1794         struct task_struct *p = rq->curr;
1795 
1796         p->se.exec_start = rq->clock_task;
1797 
1798         /* The running task is never eligible for pushing */
1799         dequeue_pushable_task(rq, p);
1800 }
1801 
1802 static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
1803 {
1804         /*
1805          * Time slice is 0 for SCHED_FIFO tasks
1806          */
1807         if (task->policy == SCHED_RR)
1808                 return DEF_TIMESLICE;
1809         else
1810                 return 0;
1811 }
1812 
1813 static const struct sched_class rt_sched_class = {
1814         .next                   = &fair_sched_class,
1815         .enqueue_task           = enqueue_task_rt,
1816         .dequeue_task           = dequeue_task_rt,
1817         .yield_task             = yield_task_rt,
1818 
1819         .check_preempt_curr     = check_preempt_curr_rt,
1820 
1821         .pick_next_task         = pick_next_task_rt,
1822         .put_prev_task          = put_prev_task_rt,
1823 
1824 #ifdef CONFIG_SMP
1825         .select_task_rq         = select_task_rq_rt,
1826 
1827         .set_cpus_allowed       = set_cpus_allowed_rt,
1828         .rq_online              = rq_online_rt,
1829         .rq_offline             = rq_offline_rt,
1830         .pre_schedule           = pre_schedule_rt,
1831         .post_schedule          = post_schedule_rt,
1832         .task_woken             = task_woken_rt,
1833         .switched_from          = switched_from_rt,
1834 #endif
1835 
1836         .set_curr_task          = set_curr_task_rt,
1837         .task_tick              = task_tick_rt,
1838 
1839         .get_rr_interval        = get_rr_interval_rt,
1840 
1841         .prio_changed           = prio_changed_rt,
1842         .switched_to            = switched_to_rt,
1843 };
1844 
1845 #ifdef CONFIG_SCHED_DEBUG
1846 extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq);
1847 
1848 static void print_rt_stats(struct seq_file *m, int cpu)
1849 {
1850         rt_rq_iter_t iter;
1851         struct rt_rq *rt_rq;
1852 
1853         rcu_read_lock();
1854         for_each_rt_rq(rt_rq, iter, cpu_rq(cpu))
1855                 print_rt_rq(m, cpu, rt_rq);
1856         rcu_read_unlock();
1857 }
1858 #endif /* CONFIG_SCHED_DEBUG */
1859 
1860 

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