2 * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
8 static inline int rt_overloaded(struct rq *rq)
10 return atomic_read(&rq->rd->rto_count);
13 static inline void rt_set_overload(struct rq *rq)
15 cpu_set(rq->cpu, rq->rd->rto_mask);
17 * Make sure the mask is visible before we set
18 * the overload count. That is checked to determine
19 * if we should look at the mask. It would be a shame
20 * if we looked at the mask, but the mask was not
24 atomic_inc(&rq->rd->rto_count);
27 static inline void rt_clear_overload(struct rq *rq)
29 /* the order here really doesn't matter */
30 atomic_dec(&rq->rd->rto_count);
31 cpu_clear(rq->cpu, rq->rd->rto_mask);
34 static void update_rt_migration(struct rq *rq)
36 if (rq->rt.rt_nr_migratory && (rq->rt.rt_nr_running > 1)) {
37 if (!rq->rt.overloaded) {
39 rq->rt.overloaded = 1;
41 } else if (rq->rt.overloaded) {
42 rt_clear_overload(rq);
43 rq->rt.overloaded = 0;
46 #endif /* CONFIG_SMP */
48 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
50 return container_of(rt_se, struct task_struct, rt);
53 static inline int on_rt_rq(struct sched_rt_entity *rt_se)
55 return !list_empty(&rt_se->run_list);
58 #ifdef CONFIG_RT_GROUP_SCHED
60 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
65 return rt_rq->rt_runtime;
68 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
70 return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
73 #define for_each_leaf_rt_rq(rt_rq, rq) \
74 list_for_each_entry(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
76 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
81 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
86 #define for_each_sched_rt_entity(rt_se) \
87 for (; rt_se; rt_se = rt_se->parent)
89 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
94 static void enqueue_rt_entity(struct sched_rt_entity *rt_se);
95 static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
97 static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
99 struct sched_rt_entity *rt_se = rt_rq->rt_se;
101 if (rt_se && !on_rt_rq(rt_se) && rt_rq->rt_nr_running) {
102 struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
104 enqueue_rt_entity(rt_se);
105 if (rt_rq->highest_prio < curr->prio)
110 static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
112 struct sched_rt_entity *rt_se = rt_rq->rt_se;
114 if (rt_se && on_rt_rq(rt_se))
115 dequeue_rt_entity(rt_se);
118 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
120 return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
123 static int rt_se_boosted(struct sched_rt_entity *rt_se)
125 struct rt_rq *rt_rq = group_rt_rq(rt_se);
126 struct task_struct *p;
129 return !!rt_rq->rt_nr_boosted;
131 p = rt_task_of(rt_se);
132 return p->prio != p->normal_prio;
136 static inline cpumask_t sched_rt_period_mask(void)
138 return cpu_rq(smp_processor_id())->rd->span;
141 static inline cpumask_t sched_rt_period_mask(void)
143 return cpu_online_map;
148 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
150 return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
153 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
155 return &rt_rq->tg->rt_bandwidth;
160 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
162 return rt_rq->rt_runtime;
165 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
167 return ktime_to_ns(def_rt_bandwidth.rt_period);
170 #define for_each_leaf_rt_rq(rt_rq, rq) \
171 for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
173 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
175 return container_of(rt_rq, struct rq, rt);
178 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
180 struct task_struct *p = rt_task_of(rt_se);
181 struct rq *rq = task_rq(p);
186 #define for_each_sched_rt_entity(rt_se) \
187 for (; rt_se; rt_se = NULL)
189 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
194 static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
198 static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
202 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
204 return rt_rq->rt_throttled;
207 static inline cpumask_t sched_rt_period_mask(void)
209 return cpu_online_map;
213 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
215 return &cpu_rq(cpu)->rt;
218 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
220 return &def_rt_bandwidth;
225 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
230 if (rt_b->rt_runtime == RUNTIME_INF)
233 span = sched_rt_period_mask();
234 for_each_cpu_mask(i, span) {
236 struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
237 struct rq *rq = rq_of_rt_rq(rt_rq);
239 spin_lock(&rq->lock);
240 if (rt_rq->rt_time) {
243 spin_lock(&rt_rq->rt_runtime_lock);
244 runtime = rt_rq->rt_runtime;
245 rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
246 if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
247 rt_rq->rt_throttled = 0;
250 if (rt_rq->rt_time || rt_rq->rt_nr_running)
252 spin_unlock(&rt_rq->rt_runtime_lock);
256 sched_rt_rq_enqueue(rt_rq);
257 spin_unlock(&rq->lock);
264 static int balance_runtime(struct rt_rq *rt_rq)
266 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
267 struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
268 int i, weight, more = 0;
271 weight = cpus_weight(rd->span);
273 spin_lock(&rt_b->rt_runtime_lock);
274 rt_period = ktime_to_ns(rt_b->rt_period);
275 for_each_cpu_mask(i, rd->span) {
276 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
282 spin_lock(&iter->rt_runtime_lock);
283 diff = iter->rt_runtime - iter->rt_time;
285 do_div(diff, weight);
286 if (rt_rq->rt_runtime + diff > rt_period)
287 diff = rt_period - rt_rq->rt_runtime;
288 iter->rt_runtime -= diff;
289 rt_rq->rt_runtime += diff;
291 if (rt_rq->rt_runtime == rt_period) {
292 spin_unlock(&iter->rt_runtime_lock);
296 spin_unlock(&iter->rt_runtime_lock);
298 spin_unlock(&rt_b->rt_runtime_lock);
304 static inline int rt_se_prio(struct sched_rt_entity *rt_se)
306 #ifdef CONFIG_RT_GROUP_SCHED
307 struct rt_rq *rt_rq = group_rt_rq(rt_se);
310 return rt_rq->highest_prio;
313 return rt_task_of(rt_se)->prio;
316 static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
318 u64 runtime = sched_rt_runtime(rt_rq);
320 if (runtime == RUNTIME_INF)
323 if (rt_rq->rt_throttled)
324 return rt_rq_throttled(rt_rq);
326 if (sched_rt_runtime(rt_rq) >= sched_rt_period(rt_rq))
330 if (rt_rq->rt_time > runtime) {
333 spin_unlock(&rt_rq->rt_runtime_lock);
334 more = balance_runtime(rt_rq);
335 spin_lock(&rt_rq->rt_runtime_lock);
338 runtime = sched_rt_runtime(rt_rq);
342 if (rt_rq->rt_time > runtime) {
343 rt_rq->rt_throttled = 1;
344 if (rt_rq_throttled(rt_rq)) {
345 sched_rt_rq_dequeue(rt_rq);
354 * Update the current task's runtime statistics. Skip current tasks that
355 * are not in our scheduling class.
357 static void update_curr_rt(struct rq *rq)
359 struct task_struct *curr = rq->curr;
360 struct sched_rt_entity *rt_se = &curr->rt;
361 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
364 if (!task_has_rt_policy(curr))
367 delta_exec = rq->clock - curr->se.exec_start;
368 if (unlikely((s64)delta_exec < 0))
371 schedstat_set(curr->se.exec_max, max(curr->se.exec_max, delta_exec));
373 curr->se.sum_exec_runtime += delta_exec;
374 curr->se.exec_start = rq->clock;
375 cpuacct_charge(curr, delta_exec);
377 spin_lock(&rt_rq->rt_runtime_lock);
378 rt_rq->rt_time += delta_exec;
379 if (sched_rt_runtime_exceeded(rt_rq))
381 spin_unlock(&rt_rq->rt_runtime_lock);
385 void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
387 WARN_ON(!rt_prio(rt_se_prio(rt_se)));
388 rt_rq->rt_nr_running++;
389 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
390 if (rt_se_prio(rt_se) < rt_rq->highest_prio)
391 rt_rq->highest_prio = rt_se_prio(rt_se);
394 if (rt_se->nr_cpus_allowed > 1) {
395 struct rq *rq = rq_of_rt_rq(rt_rq);
396 rq->rt.rt_nr_migratory++;
399 update_rt_migration(rq_of_rt_rq(rt_rq));
401 #ifdef CONFIG_RT_GROUP_SCHED
402 if (rt_se_boosted(rt_se))
403 rt_rq->rt_nr_boosted++;
406 start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
408 start_rt_bandwidth(&def_rt_bandwidth);
413 void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
415 WARN_ON(!rt_prio(rt_se_prio(rt_se)));
416 WARN_ON(!rt_rq->rt_nr_running);
417 rt_rq->rt_nr_running--;
418 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
419 if (rt_rq->rt_nr_running) {
420 struct rt_prio_array *array;
422 WARN_ON(rt_se_prio(rt_se) < rt_rq->highest_prio);
423 if (rt_se_prio(rt_se) == rt_rq->highest_prio) {
425 array = &rt_rq->active;
426 rt_rq->highest_prio =
427 sched_find_first_bit(array->bitmap);
428 } /* otherwise leave rq->highest prio alone */
430 rt_rq->highest_prio = MAX_RT_PRIO;
433 if (rt_se->nr_cpus_allowed > 1) {
434 struct rq *rq = rq_of_rt_rq(rt_rq);
435 rq->rt.rt_nr_migratory--;
438 update_rt_migration(rq_of_rt_rq(rt_rq));
439 #endif /* CONFIG_SMP */
440 #ifdef CONFIG_RT_GROUP_SCHED
441 if (rt_se_boosted(rt_se))
442 rt_rq->rt_nr_boosted--;
444 WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
448 static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
450 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
451 struct rt_prio_array *array = &rt_rq->active;
452 struct rt_rq *group_rq = group_rt_rq(rt_se);
454 if (group_rq && rt_rq_throttled(group_rq))
457 list_add_tail(&rt_se->run_list, array->queue + rt_se_prio(rt_se));
458 __set_bit(rt_se_prio(rt_se), array->bitmap);
460 inc_rt_tasks(rt_se, rt_rq);
463 static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
465 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
466 struct rt_prio_array *array = &rt_rq->active;
468 list_del_init(&rt_se->run_list);
469 if (list_empty(array->queue + rt_se_prio(rt_se)))
470 __clear_bit(rt_se_prio(rt_se), array->bitmap);
472 dec_rt_tasks(rt_se, rt_rq);
476 * Because the prio of an upper entry depends on the lower
477 * entries, we must remove entries top - down.
479 * XXX: O(1/2 h^2) because we can only walk up, not down the chain.
480 * doesn't matter much for now, as h=2 for GROUP_SCHED.
482 static void dequeue_rt_stack(struct task_struct *p)
484 struct sched_rt_entity *rt_se, *top_se;
487 * dequeue all, top - down.
492 for_each_sched_rt_entity(rt_se) {
497 dequeue_rt_entity(top_se);
502 * Adding/removing a task to/from a priority array:
504 static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
506 struct sched_rt_entity *rt_se = &p->rt;
514 * enqueue everybody, bottom - up.
516 for_each_sched_rt_entity(rt_se)
517 enqueue_rt_entity(rt_se);
520 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
522 struct sched_rt_entity *rt_se = &p->rt;
530 * re-enqueue all non-empty rt_rq entities.
532 for_each_sched_rt_entity(rt_se) {
533 rt_rq = group_rt_rq(rt_se);
534 if (rt_rq && rt_rq->rt_nr_running)
535 enqueue_rt_entity(rt_se);
540 * Put task to the end of the run list without the overhead of dequeue
541 * followed by enqueue.
544 void requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
546 struct rt_prio_array *array = &rt_rq->active;
548 list_move_tail(&rt_se->run_list, array->queue + rt_se_prio(rt_se));
551 static void requeue_task_rt(struct rq *rq, struct task_struct *p)
553 struct sched_rt_entity *rt_se = &p->rt;
556 for_each_sched_rt_entity(rt_se) {
557 rt_rq = rt_rq_of_se(rt_se);
558 requeue_rt_entity(rt_rq, rt_se);
562 static void yield_task_rt(struct rq *rq)
564 requeue_task_rt(rq, rq->curr);
568 static int find_lowest_rq(struct task_struct *task);
570 static int select_task_rq_rt(struct task_struct *p, int sync)
572 struct rq *rq = task_rq(p);
575 * If the current task is an RT task, then
576 * try to see if we can wake this RT task up on another
577 * runqueue. Otherwise simply start this RT task
578 * on its current runqueue.
580 * We want to avoid overloading runqueues. Even if
581 * the RT task is of higher priority than the current RT task.
582 * RT tasks behave differently than other tasks. If
583 * one gets preempted, we try to push it off to another queue.
584 * So trying to keep a preempting RT task on the same
585 * cache hot CPU will force the running RT task to
586 * a cold CPU. So we waste all the cache for the lower
587 * RT task in hopes of saving some of a RT task
588 * that is just being woken and probably will have
591 if (unlikely(rt_task(rq->curr)) &&
592 (p->rt.nr_cpus_allowed > 1)) {
593 int cpu = find_lowest_rq(p);
595 return (cpu == -1) ? task_cpu(p) : cpu;
599 * Otherwise, just let it ride on the affined RQ and the
600 * post-schedule router will push the preempted task away
604 #endif /* CONFIG_SMP */
607 * Preempt the current task with a newly woken task if needed:
609 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p)
611 if (p->prio < rq->curr->prio)
612 resched_task(rq->curr);
615 static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
618 struct rt_prio_array *array = &rt_rq->active;
619 struct sched_rt_entity *next = NULL;
620 struct list_head *queue;
623 idx = sched_find_first_bit(array->bitmap);
624 BUG_ON(idx >= MAX_RT_PRIO);
626 queue = array->queue + idx;
627 next = list_entry(queue->next, struct sched_rt_entity, run_list);
632 static struct task_struct *pick_next_task_rt(struct rq *rq)
634 struct sched_rt_entity *rt_se;
635 struct task_struct *p;
640 if (unlikely(!rt_rq->rt_nr_running))
643 if (rt_rq_throttled(rt_rq))
647 rt_se = pick_next_rt_entity(rq, rt_rq);
649 rt_rq = group_rt_rq(rt_se);
652 p = rt_task_of(rt_se);
653 p->se.exec_start = rq->clock;
657 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
660 p->se.exec_start = 0;
665 /* Only try algorithms three times */
666 #define RT_MAX_TRIES 3
668 static int double_lock_balance(struct rq *this_rq, struct rq *busiest);
669 static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
671 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
673 if (!task_running(rq, p) &&
674 (cpu < 0 || cpu_isset(cpu, p->cpus_allowed)) &&
675 (p->rt.nr_cpus_allowed > 1))
680 /* Return the second highest RT task, NULL otherwise */
681 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
683 struct task_struct *next = NULL;
684 struct sched_rt_entity *rt_se;
685 struct rt_prio_array *array;
689 for_each_leaf_rt_rq(rt_rq, rq) {
690 array = &rt_rq->active;
691 idx = sched_find_first_bit(array->bitmap);
693 if (idx >= MAX_RT_PRIO)
695 if (next && next->prio < idx)
697 list_for_each_entry(rt_se, array->queue + idx, run_list) {
698 struct task_struct *p = rt_task_of(rt_se);
699 if (pick_rt_task(rq, p, cpu)) {
705 idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
713 static DEFINE_PER_CPU(cpumask_t, local_cpu_mask);
715 static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask)
717 int lowest_prio = -1;
722 cpus_and(*lowest_mask, task_rq(task)->rd->online, task->cpus_allowed);
725 * Scan each rq for the lowest prio.
727 for_each_cpu_mask(cpu, *lowest_mask) {
728 struct rq *rq = cpu_rq(cpu);
730 /* We look for lowest RT prio or non-rt CPU */
731 if (rq->rt.highest_prio >= MAX_RT_PRIO) {
733 * if we already found a low RT queue
734 * and now we found this non-rt queue
735 * clear the mask and set our bit.
736 * Otherwise just return the queue as is
737 * and the count==1 will cause the algorithm
738 * to use the first bit found.
740 if (lowest_cpu != -1) {
741 cpus_clear(*lowest_mask);
742 cpu_set(rq->cpu, *lowest_mask);
747 /* no locking for now */
748 if ((rq->rt.highest_prio > task->prio)
749 && (rq->rt.highest_prio >= lowest_prio)) {
750 if (rq->rt.highest_prio > lowest_prio) {
751 /* new low - clear old data */
752 lowest_prio = rq->rt.highest_prio;
758 cpu_clear(cpu, *lowest_mask);
762 * Clear out all the set bits that represent
763 * runqueues that were of higher prio than
766 if (lowest_cpu > 0) {
768 * Perhaps we could add another cpumask op to
769 * zero out bits. Like cpu_zero_bits(cpumask, nrbits);
770 * Then that could be optimized to use memset and such.
772 for_each_cpu_mask(cpu, *lowest_mask) {
773 if (cpu >= lowest_cpu)
775 cpu_clear(cpu, *lowest_mask);
782 static inline int pick_optimal_cpu(int this_cpu, cpumask_t *mask)
786 /* "this_cpu" is cheaper to preempt than a remote processor */
787 if ((this_cpu != -1) && cpu_isset(this_cpu, *mask))
790 first = first_cpu(*mask);
791 if (first != NR_CPUS)
797 static int find_lowest_rq(struct task_struct *task)
799 struct sched_domain *sd;
800 cpumask_t *lowest_mask = &__get_cpu_var(local_cpu_mask);
801 int this_cpu = smp_processor_id();
802 int cpu = task_cpu(task);
803 int count = find_lowest_cpus(task, lowest_mask);
806 return -1; /* No targets found */
809 * There is no sense in performing an optimal search if only one
813 return first_cpu(*lowest_mask);
816 * At this point we have built a mask of cpus representing the
817 * lowest priority tasks in the system. Now we want to elect
818 * the best one based on our affinity and topology.
820 * We prioritize the last cpu that the task executed on since
821 * it is most likely cache-hot in that location.
823 if (cpu_isset(cpu, *lowest_mask))
827 * Otherwise, we consult the sched_domains span maps to figure
828 * out which cpu is logically closest to our hot cache data.
831 this_cpu = -1; /* Skip this_cpu opt if the same */
833 for_each_domain(cpu, sd) {
834 if (sd->flags & SD_WAKE_AFFINE) {
835 cpumask_t domain_mask;
838 cpus_and(domain_mask, sd->span, *lowest_mask);
840 best_cpu = pick_optimal_cpu(this_cpu,
848 * And finally, if there were no matches within the domains
849 * just give the caller *something* to work with from the compatible
852 return pick_optimal_cpu(this_cpu, lowest_mask);
855 /* Will lock the rq it finds */
856 static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
858 struct rq *lowest_rq = NULL;
862 for (tries = 0; tries < RT_MAX_TRIES; tries++) {
863 cpu = find_lowest_rq(task);
865 if ((cpu == -1) || (cpu == rq->cpu))
868 lowest_rq = cpu_rq(cpu);
870 /* if the prio of this runqueue changed, try again */
871 if (double_lock_balance(rq, lowest_rq)) {
873 * We had to unlock the run queue. In
874 * the mean time, task could have
875 * migrated already or had its affinity changed.
876 * Also make sure that it wasn't scheduled on its rq.
878 if (unlikely(task_rq(task) != rq ||
879 !cpu_isset(lowest_rq->cpu,
880 task->cpus_allowed) ||
881 task_running(rq, task) ||
884 spin_unlock(&lowest_rq->lock);
890 /* If this rq is still suitable use it. */
891 if (lowest_rq->rt.highest_prio > task->prio)
895 spin_unlock(&lowest_rq->lock);
903 * If the current CPU has more than one RT task, see if the non
904 * running task can migrate over to a CPU that is running a task
905 * of lesser priority.
907 static int push_rt_task(struct rq *rq)
909 struct task_struct *next_task;
910 struct rq *lowest_rq;
912 int paranoid = RT_MAX_TRIES;
914 if (!rq->rt.overloaded)
917 next_task = pick_next_highest_task_rt(rq, -1);
922 if (unlikely(next_task == rq->curr)) {
928 * It's possible that the next_task slipped in of
929 * higher priority than current. If that's the case
930 * just reschedule current.
932 if (unlikely(next_task->prio < rq->curr->prio)) {
933 resched_task(rq->curr);
937 /* We might release rq lock */
938 get_task_struct(next_task);
940 /* find_lock_lowest_rq locks the rq if found */
941 lowest_rq = find_lock_lowest_rq(next_task, rq);
943 struct task_struct *task;
945 * find lock_lowest_rq releases rq->lock
946 * so it is possible that next_task has changed.
947 * If it has, then try again.
949 task = pick_next_highest_task_rt(rq, -1);
950 if (unlikely(task != next_task) && task && paranoid--) {
951 put_task_struct(next_task);
958 deactivate_task(rq, next_task, 0);
959 set_task_cpu(next_task, lowest_rq->cpu);
960 activate_task(lowest_rq, next_task, 0);
962 resched_task(lowest_rq->curr);
964 spin_unlock(&lowest_rq->lock);
968 put_task_struct(next_task);
974 * TODO: Currently we just use the second highest prio task on
975 * the queue, and stop when it can't migrate (or there's
976 * no more RT tasks). There may be a case where a lower
977 * priority RT task has a different affinity than the
978 * higher RT task. In this case the lower RT task could
979 * possibly be able to migrate where as the higher priority
980 * RT task could not. We currently ignore this issue.
981 * Enhancements are welcome!
983 static void push_rt_tasks(struct rq *rq)
985 /* push_rt_task will return true if it moved an RT */
986 while (push_rt_task(rq))
990 static int pull_rt_task(struct rq *this_rq)
992 int this_cpu = this_rq->cpu, ret = 0, cpu;
993 struct task_struct *p, *next;
996 if (likely(!rt_overloaded(this_rq)))
999 next = pick_next_task_rt(this_rq);
1001 for_each_cpu_mask(cpu, this_rq->rd->rto_mask) {
1002 if (this_cpu == cpu)
1005 src_rq = cpu_rq(cpu);
1007 * We can potentially drop this_rq's lock in
1008 * double_lock_balance, and another CPU could
1009 * steal our next task - hence we must cause
1010 * the caller to recalculate the next task
1013 if (double_lock_balance(this_rq, src_rq)) {
1014 struct task_struct *old_next = next;
1016 next = pick_next_task_rt(this_rq);
1017 if (next != old_next)
1022 * Are there still pullable RT tasks?
1024 if (src_rq->rt.rt_nr_running <= 1)
1027 p = pick_next_highest_task_rt(src_rq, this_cpu);
1030 * Do we have an RT task that preempts
1031 * the to-be-scheduled task?
1033 if (p && (!next || (p->prio < next->prio))) {
1034 WARN_ON(p == src_rq->curr);
1035 WARN_ON(!p->se.on_rq);
1038 * There's a chance that p is higher in priority
1039 * than what's currently running on its cpu.
1040 * This is just that p is wakeing up and hasn't
1041 * had a chance to schedule. We only pull
1042 * p if it is lower in priority than the
1043 * current task on the run queue or
1044 * this_rq next task is lower in prio than
1045 * the current task on that rq.
1047 if (p->prio < src_rq->curr->prio ||
1048 (next && next->prio < src_rq->curr->prio))
1053 deactivate_task(src_rq, p, 0);
1054 set_task_cpu(p, this_cpu);
1055 activate_task(this_rq, p, 0);
1057 * We continue with the search, just in
1058 * case there's an even higher prio task
1059 * in another runqueue. (low likelyhood
1062 * Update next so that we won't pick a task
1063 * on another cpu with a priority lower (or equal)
1064 * than the one we just picked.
1070 spin_unlock(&src_rq->lock);
1076 static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
1078 /* Try to pull RT tasks here if we lower this rq's prio */
1079 if (unlikely(rt_task(prev)) && rq->rt.highest_prio > prev->prio)
1083 static void post_schedule_rt(struct rq *rq)
1086 * If we have more than one rt_task queued, then
1087 * see if we can push the other rt_tasks off to other CPUS.
1088 * Note we may release the rq lock, and since
1089 * the lock was owned by prev, we need to release it
1090 * first via finish_lock_switch and then reaquire it here.
1092 if (unlikely(rq->rt.overloaded)) {
1093 spin_lock_irq(&rq->lock);
1095 spin_unlock_irq(&rq->lock);
1100 static void task_wake_up_rt(struct rq *rq, struct task_struct *p)
1102 if (!task_running(rq, p) &&
1103 (p->prio >= rq->rt.highest_prio) &&
1108 static unsigned long
1109 load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
1110 unsigned long max_load_move,
1111 struct sched_domain *sd, enum cpu_idle_type idle,
1112 int *all_pinned, int *this_best_prio)
1114 /* don't touch RT tasks */
1119 move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
1120 struct sched_domain *sd, enum cpu_idle_type idle)
1122 /* don't touch RT tasks */
1126 static void set_cpus_allowed_rt(struct task_struct *p, cpumask_t *new_mask)
1128 int weight = cpus_weight(*new_mask);
1130 BUG_ON(!rt_task(p));
1133 * Update the migration status of the RQ if we have an RT task
1134 * which is running AND changing its weight value.
1136 if (p->se.on_rq && (weight != p->rt.nr_cpus_allowed)) {
1137 struct rq *rq = task_rq(p);
1139 if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
1140 rq->rt.rt_nr_migratory++;
1141 } else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
1142 BUG_ON(!rq->rt.rt_nr_migratory);
1143 rq->rt.rt_nr_migratory--;
1146 update_rt_migration(rq);
1149 p->cpus_allowed = *new_mask;
1150 p->rt.nr_cpus_allowed = weight;
1153 /* Assumes rq->lock is held */
1154 static void join_domain_rt(struct rq *rq)
1156 if (rq->rt.overloaded)
1157 rt_set_overload(rq);
1160 /* Assumes rq->lock is held */
1161 static void leave_domain_rt(struct rq *rq)
1163 if (rq->rt.overloaded)
1164 rt_clear_overload(rq);
1168 * When switch from the rt queue, we bring ourselves to a position
1169 * that we might want to pull RT tasks from other runqueues.
1171 static void switched_from_rt(struct rq *rq, struct task_struct *p,
1175 * If there are other RT tasks then we will reschedule
1176 * and the scheduling of the other RT tasks will handle
1177 * the balancing. But if we are the last RT task
1178 * we may need to handle the pulling of RT tasks
1181 if (!rq->rt.rt_nr_running)
1184 #endif /* CONFIG_SMP */
1187 * When switching a task to RT, we may overload the runqueue
1188 * with RT tasks. In this case we try to push them off to
1191 static void switched_to_rt(struct rq *rq, struct task_struct *p,
1194 int check_resched = 1;
1197 * If we are already running, then there's nothing
1198 * that needs to be done. But if we are not running
1199 * we may need to preempt the current running task.
1200 * If that current running task is also an RT task
1201 * then see if we can move to another run queue.
1205 if (rq->rt.overloaded && push_rt_task(rq) &&
1206 /* Don't resched if we changed runqueues */
1209 #endif /* CONFIG_SMP */
1210 if (check_resched && p->prio < rq->curr->prio)
1211 resched_task(rq->curr);
1216 * Priority of the task has changed. This may cause
1217 * us to initiate a push or pull.
1219 static void prio_changed_rt(struct rq *rq, struct task_struct *p,
1220 int oldprio, int running)
1225 * If our priority decreases while running, we
1226 * may need to pull tasks to this runqueue.
1228 if (oldprio < p->prio)
1231 * If there's a higher priority task waiting to run
1232 * then reschedule. Note, the above pull_rt_task
1233 * can release the rq lock and p could migrate.
1234 * Only reschedule if p is still on the same runqueue.
1236 if (p->prio > rq->rt.highest_prio && rq->curr == p)
1239 /* For UP simply resched on drop of prio */
1240 if (oldprio < p->prio)
1242 #endif /* CONFIG_SMP */
1245 * This task is not running, but if it is
1246 * greater than the current running task
1249 if (p->prio < rq->curr->prio)
1250 resched_task(rq->curr);
1254 static void watchdog(struct rq *rq, struct task_struct *p)
1256 unsigned long soft, hard;
1261 soft = p->signal->rlim[RLIMIT_RTTIME].rlim_cur;
1262 hard = p->signal->rlim[RLIMIT_RTTIME].rlim_max;
1264 if (soft != RLIM_INFINITY) {
1268 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
1269 if (p->rt.timeout > next)
1270 p->it_sched_expires = p->se.sum_exec_runtime;
1274 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
1281 * RR tasks need a special form of timeslice management.
1282 * FIFO tasks have no timeslices.
1284 if (p->policy != SCHED_RR)
1287 if (--p->rt.time_slice)
1290 p->rt.time_slice = DEF_TIMESLICE;
1293 * Requeue to the end of queue if we are not the only element
1296 if (p->rt.run_list.prev != p->rt.run_list.next) {
1297 requeue_task_rt(rq, p);
1298 set_tsk_need_resched(p);
1302 static void set_curr_task_rt(struct rq *rq)
1304 struct task_struct *p = rq->curr;
1306 p->se.exec_start = rq->clock;
1309 const struct sched_class rt_sched_class = {
1310 .next = &fair_sched_class,
1311 .enqueue_task = enqueue_task_rt,
1312 .dequeue_task = dequeue_task_rt,
1313 .yield_task = yield_task_rt,
1315 .select_task_rq = select_task_rq_rt,
1316 #endif /* CONFIG_SMP */
1318 .check_preempt_curr = check_preempt_curr_rt,
1320 .pick_next_task = pick_next_task_rt,
1321 .put_prev_task = put_prev_task_rt,
1324 .load_balance = load_balance_rt,
1325 .move_one_task = move_one_task_rt,
1326 .set_cpus_allowed = set_cpus_allowed_rt,
1327 .join_domain = join_domain_rt,
1328 .leave_domain = leave_domain_rt,
1329 .pre_schedule = pre_schedule_rt,
1330 .post_schedule = post_schedule_rt,
1331 .task_wake_up = task_wake_up_rt,
1332 .switched_from = switched_from_rt,
1335 .set_curr_task = set_curr_task_rt,
1336 .task_tick = task_tick_rt,
1338 .prio_changed = prio_changed_rt,
1339 .switched_to = switched_to_rt,