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)
18 cpu_set(rq->cpu, rq->rd->rto_mask);
20 * Make sure the mask is visible before we set
21 * the overload count. That is checked to determine
22 * if we should look at the mask. It would be a shame
23 * if we looked at the mask, but the mask was not
27 atomic_inc(&rq->rd->rto_count);
30 static inline void rt_clear_overload(struct rq *rq)
35 /* the order here really doesn't matter */
36 atomic_dec(&rq->rd->rto_count);
37 cpu_clear(rq->cpu, rq->rd->rto_mask);
40 static void update_rt_migration(struct rq *rq)
42 if (rq->rt.rt_nr_migratory && (rq->rt.rt_nr_running > 1)) {
43 if (!rq->rt.overloaded) {
45 rq->rt.overloaded = 1;
47 } else if (rq->rt.overloaded) {
48 rt_clear_overload(rq);
49 rq->rt.overloaded = 0;
52 #endif /* CONFIG_SMP */
54 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
56 return container_of(rt_se, struct task_struct, rt);
59 static inline int on_rt_rq(struct sched_rt_entity *rt_se)
61 return !list_empty(&rt_se->run_list);
64 #ifdef CONFIG_RT_GROUP_SCHED
66 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
71 return rt_rq->rt_runtime;
74 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
76 return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
79 #define for_each_leaf_rt_rq(rt_rq, rq) \
80 list_for_each_entry(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
82 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
87 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
92 #define for_each_sched_rt_entity(rt_se) \
93 for (; rt_se; rt_se = rt_se->parent)
95 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
100 static void enqueue_rt_entity(struct sched_rt_entity *rt_se);
101 static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
103 static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
105 struct sched_rt_entity *rt_se = rt_rq->rt_se;
107 if (rt_se && !on_rt_rq(rt_se) && rt_rq->rt_nr_running) {
108 struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
110 enqueue_rt_entity(rt_se);
111 if (rt_rq->highest_prio < curr->prio)
116 static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
118 struct sched_rt_entity *rt_se = rt_rq->rt_se;
120 if (rt_se && on_rt_rq(rt_se))
121 dequeue_rt_entity(rt_se);
124 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
126 return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
129 static int rt_se_boosted(struct sched_rt_entity *rt_se)
131 struct rt_rq *rt_rq = group_rt_rq(rt_se);
132 struct task_struct *p;
135 return !!rt_rq->rt_nr_boosted;
137 p = rt_task_of(rt_se);
138 return p->prio != p->normal_prio;
142 static inline cpumask_t sched_rt_period_mask(void)
144 return cpu_rq(smp_processor_id())->rd->span;
147 static inline cpumask_t sched_rt_period_mask(void)
149 return cpu_online_map;
154 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
156 return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
159 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
161 return &rt_rq->tg->rt_bandwidth;
166 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
168 return rt_rq->rt_runtime;
171 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
173 return ktime_to_ns(def_rt_bandwidth.rt_period);
176 #define for_each_leaf_rt_rq(rt_rq, rq) \
177 for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
179 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
181 return container_of(rt_rq, struct rq, rt);
184 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
186 struct task_struct *p = rt_task_of(rt_se);
187 struct rq *rq = task_rq(p);
192 #define for_each_sched_rt_entity(rt_se) \
193 for (; rt_se; rt_se = NULL)
195 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
200 static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
204 static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
208 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
210 return rt_rq->rt_throttled;
213 static inline cpumask_t sched_rt_period_mask(void)
215 return cpu_online_map;
219 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
221 return &cpu_rq(cpu)->rt;
224 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
226 return &def_rt_bandwidth;
231 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
236 if (rt_b->rt_runtime == RUNTIME_INF)
239 span = sched_rt_period_mask();
240 for_each_cpu_mask(i, span) {
242 struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
243 struct rq *rq = rq_of_rt_rq(rt_rq);
245 spin_lock(&rq->lock);
246 if (rt_rq->rt_time) {
249 spin_lock(&rt_rq->rt_runtime_lock);
250 runtime = rt_rq->rt_runtime;
251 rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
252 if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
253 rt_rq->rt_throttled = 0;
256 if (rt_rq->rt_time || rt_rq->rt_nr_running)
258 spin_unlock(&rt_rq->rt_runtime_lock);
262 sched_rt_rq_enqueue(rt_rq);
263 spin_unlock(&rq->lock);
270 static int balance_runtime(struct rt_rq *rt_rq)
272 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
273 struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
274 int i, weight, more = 0;
277 weight = cpus_weight(rd->span);
279 spin_lock(&rt_b->rt_runtime_lock);
280 rt_period = ktime_to_ns(rt_b->rt_period);
281 for_each_cpu_mask(i, rd->span) {
282 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
288 spin_lock(&iter->rt_runtime_lock);
289 diff = iter->rt_runtime - iter->rt_time;
291 do_div(diff, weight);
292 if (rt_rq->rt_runtime + diff > rt_period)
293 diff = rt_period - rt_rq->rt_runtime;
294 iter->rt_runtime -= diff;
295 rt_rq->rt_runtime += diff;
297 if (rt_rq->rt_runtime == rt_period) {
298 spin_unlock(&iter->rt_runtime_lock);
302 spin_unlock(&iter->rt_runtime_lock);
304 spin_unlock(&rt_b->rt_runtime_lock);
310 static inline int rt_se_prio(struct sched_rt_entity *rt_se)
312 #ifdef CONFIG_RT_GROUP_SCHED
313 struct rt_rq *rt_rq = group_rt_rq(rt_se);
316 return rt_rq->highest_prio;
319 return rt_task_of(rt_se)->prio;
322 static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
324 u64 runtime = sched_rt_runtime(rt_rq);
326 if (runtime == RUNTIME_INF)
329 if (rt_rq->rt_throttled)
330 return rt_rq_throttled(rt_rq);
332 if (sched_rt_runtime(rt_rq) >= sched_rt_period(rt_rq))
336 if (rt_rq->rt_time > runtime) {
339 spin_unlock(&rt_rq->rt_runtime_lock);
340 more = balance_runtime(rt_rq);
341 spin_lock(&rt_rq->rt_runtime_lock);
344 runtime = sched_rt_runtime(rt_rq);
348 if (rt_rq->rt_time > runtime) {
349 rt_rq->rt_throttled = 1;
350 if (rt_rq_throttled(rt_rq)) {
351 sched_rt_rq_dequeue(rt_rq);
360 * Update the current task's runtime statistics. Skip current tasks that
361 * are not in our scheduling class.
363 static void update_curr_rt(struct rq *rq)
365 struct task_struct *curr = rq->curr;
366 struct sched_rt_entity *rt_se = &curr->rt;
367 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
370 if (!task_has_rt_policy(curr))
373 delta_exec = rq->clock - curr->se.exec_start;
374 if (unlikely((s64)delta_exec < 0))
377 schedstat_set(curr->se.exec_max, max(curr->se.exec_max, delta_exec));
379 curr->se.sum_exec_runtime += delta_exec;
380 curr->se.exec_start = rq->clock;
381 cpuacct_charge(curr, delta_exec);
383 for_each_sched_rt_entity(rt_se) {
384 rt_rq = rt_rq_of_se(rt_se);
386 spin_lock(&rt_rq->rt_runtime_lock);
387 rt_rq->rt_time += delta_exec;
388 if (sched_rt_runtime_exceeded(rt_rq))
390 spin_unlock(&rt_rq->rt_runtime_lock);
395 void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
397 WARN_ON(!rt_prio(rt_se_prio(rt_se)));
398 rt_rq->rt_nr_running++;
399 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
400 if (rt_se_prio(rt_se) < rt_rq->highest_prio) {
401 struct rq *rq = rq_of_rt_rq(rt_rq);
402 rt_rq->highest_prio = rt_se_prio(rt_se);
405 cpupri_set(&rq->rd->cpupri, rq->cpu,
410 if (rt_se->nr_cpus_allowed > 1) {
411 struct rq *rq = rq_of_rt_rq(rt_rq);
412 rq->rt.rt_nr_migratory++;
415 update_rt_migration(rq_of_rt_rq(rt_rq));
417 #ifdef CONFIG_RT_GROUP_SCHED
418 if (rt_se_boosted(rt_se))
419 rt_rq->rt_nr_boosted++;
422 start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
424 start_rt_bandwidth(&def_rt_bandwidth);
429 void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
432 int highest_prio = rt_rq->highest_prio;
435 WARN_ON(!rt_prio(rt_se_prio(rt_se)));
436 WARN_ON(!rt_rq->rt_nr_running);
437 rt_rq->rt_nr_running--;
438 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
439 if (rt_rq->rt_nr_running) {
440 struct rt_prio_array *array;
442 WARN_ON(rt_se_prio(rt_se) < rt_rq->highest_prio);
443 if (rt_se_prio(rt_se) == rt_rq->highest_prio) {
445 array = &rt_rq->active;
446 rt_rq->highest_prio =
447 sched_find_first_bit(array->bitmap);
448 } /* otherwise leave rq->highest prio alone */
450 rt_rq->highest_prio = MAX_RT_PRIO;
453 if (rt_se->nr_cpus_allowed > 1) {
454 struct rq *rq = rq_of_rt_rq(rt_rq);
455 rq->rt.rt_nr_migratory--;
458 if (rt_rq->highest_prio != highest_prio) {
459 struct rq *rq = rq_of_rt_rq(rt_rq);
462 cpupri_set(&rq->rd->cpupri, rq->cpu,
463 rt_rq->highest_prio);
466 update_rt_migration(rq_of_rt_rq(rt_rq));
467 #endif /* CONFIG_SMP */
468 #ifdef CONFIG_RT_GROUP_SCHED
469 if (rt_se_boosted(rt_se))
470 rt_rq->rt_nr_boosted--;
472 WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
476 static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
478 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
479 struct rt_prio_array *array = &rt_rq->active;
480 struct rt_rq *group_rq = group_rt_rq(rt_se);
482 if (group_rq && rt_rq_throttled(group_rq))
485 if (rt_se->nr_cpus_allowed == 1)
486 list_add_tail(&rt_se->run_list,
487 array->xqueue + rt_se_prio(rt_se));
489 list_add_tail(&rt_se->run_list,
490 array->squeue + rt_se_prio(rt_se));
492 __set_bit(rt_se_prio(rt_se), array->bitmap);
494 inc_rt_tasks(rt_se, rt_rq);
497 static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
499 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
500 struct rt_prio_array *array = &rt_rq->active;
502 list_del_init(&rt_se->run_list);
503 if (list_empty(array->squeue + rt_se_prio(rt_se))
504 && list_empty(array->xqueue + rt_se_prio(rt_se)))
505 __clear_bit(rt_se_prio(rt_se), array->bitmap);
507 dec_rt_tasks(rt_se, rt_rq);
511 * Because the prio of an upper entry depends on the lower
512 * entries, we must remove entries top - down.
514 static void dequeue_rt_stack(struct task_struct *p)
516 struct sched_rt_entity *rt_se, *back = NULL;
519 for_each_sched_rt_entity(rt_se) {
524 for (rt_se = back; rt_se; rt_se = rt_se->back) {
526 dequeue_rt_entity(rt_se);
531 * Adding/removing a task to/from a priority array:
533 static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
535 struct sched_rt_entity *rt_se = &p->rt;
543 * enqueue everybody, bottom - up.
545 for_each_sched_rt_entity(rt_se)
546 enqueue_rt_entity(rt_se);
549 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
551 struct sched_rt_entity *rt_se = &p->rt;
559 * re-enqueue all non-empty rt_rq entities.
561 for_each_sched_rt_entity(rt_se) {
562 rt_rq = group_rt_rq(rt_se);
563 if (rt_rq && rt_rq->rt_nr_running)
564 enqueue_rt_entity(rt_se);
569 * Put task to the end of the run list without the overhead of dequeue
570 * followed by enqueue.
572 * Note: We always enqueue the task to the shared-queue, regardless of its
573 * previous position w.r.t. exclusive vs shared. This is so that exclusive RR
574 * tasks fairly round-robin with all tasks on the runqueue, not just other
578 void requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
580 struct rt_prio_array *array = &rt_rq->active;
582 list_del_init(&rt_se->run_list);
583 list_add_tail(&rt_se->run_list, array->squeue + rt_se_prio(rt_se));
586 static void requeue_task_rt(struct rq *rq, struct task_struct *p)
588 struct sched_rt_entity *rt_se = &p->rt;
591 for_each_sched_rt_entity(rt_se) {
592 rt_rq = rt_rq_of_se(rt_se);
593 requeue_rt_entity(rt_rq, rt_se);
597 static void yield_task_rt(struct rq *rq)
599 requeue_task_rt(rq, rq->curr);
603 static int find_lowest_rq(struct task_struct *task);
605 static int select_task_rq_rt(struct task_struct *p, int sync)
607 struct rq *rq = task_rq(p);
610 * If the current task is an RT task, then
611 * try to see if we can wake this RT task up on another
612 * runqueue. Otherwise simply start this RT task
613 * on its current runqueue.
615 * We want to avoid overloading runqueues. Even if
616 * the RT task is of higher priority than the current RT task.
617 * RT tasks behave differently than other tasks. If
618 * one gets preempted, we try to push it off to another queue.
619 * So trying to keep a preempting RT task on the same
620 * cache hot CPU will force the running RT task to
621 * a cold CPU. So we waste all the cache for the lower
622 * RT task in hopes of saving some of a RT task
623 * that is just being woken and probably will have
626 if (unlikely(rt_task(rq->curr)) &&
627 (p->rt.nr_cpus_allowed > 1)) {
628 int cpu = find_lowest_rq(p);
630 return (cpu == -1) ? task_cpu(p) : cpu;
634 * Otherwise, just let it ride on the affined RQ and the
635 * post-schedule router will push the preempted task away
639 #endif /* CONFIG_SMP */
641 static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
642 struct rt_rq *rt_rq);
645 * Preempt the current task with a newly woken task if needed:
647 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p)
649 if (p->prio < rq->curr->prio) {
650 resched_task(rq->curr);
658 * - the newly woken task is of equal priority to the current task
659 * - the newly woken task is non-migratable while current is migratable
660 * - current will be preempted on the next reschedule
662 * we should check to see if current can readily move to a different
663 * cpu. If so, we will reschedule to allow the push logic to try
664 * to move current somewhere else, making room for our non-migratable
667 if((p->prio == rq->curr->prio)
668 && p->rt.nr_cpus_allowed == 1
669 && rq->curr->rt.nr_cpus_allowed != 1
670 && pick_next_rt_entity(rq, &rq->rt) != &rq->curr->rt) {
673 if (cpupri_find(&rq->rd->cpupri, rq->curr, &mask))
675 * There appears to be other cpus that can accept
676 * current, so lets reschedule to try and push it away
678 resched_task(rq->curr);
683 static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
686 struct rt_prio_array *array = &rt_rq->active;
687 struct sched_rt_entity *next = NULL;
688 struct list_head *queue;
691 idx = sched_find_first_bit(array->bitmap);
692 BUG_ON(idx >= MAX_RT_PRIO);
694 queue = array->xqueue + idx;
695 if (!list_empty(queue))
696 next = list_entry(queue->next, struct sched_rt_entity,
699 queue = array->squeue + idx;
700 next = list_entry(queue->next, struct sched_rt_entity,
707 static struct task_struct *pick_next_task_rt(struct rq *rq)
709 struct sched_rt_entity *rt_se;
710 struct task_struct *p;
715 if (unlikely(!rt_rq->rt_nr_running))
718 if (rt_rq_throttled(rt_rq))
722 rt_se = pick_next_rt_entity(rq, rt_rq);
724 rt_rq = group_rt_rq(rt_se);
727 p = rt_task_of(rt_se);
728 p->se.exec_start = rq->clock;
732 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
735 p->se.exec_start = 0;
740 /* Only try algorithms three times */
741 #define RT_MAX_TRIES 3
743 static int double_lock_balance(struct rq *this_rq, struct rq *busiest);
744 static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
746 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
748 if (!task_running(rq, p) &&
749 (cpu < 0 || cpu_isset(cpu, p->cpus_allowed)) &&
750 (p->rt.nr_cpus_allowed > 1))
755 /* Return the second highest RT task, NULL otherwise */
756 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
758 struct task_struct *next = NULL;
759 struct sched_rt_entity *rt_se;
760 struct rt_prio_array *array;
764 for_each_leaf_rt_rq(rt_rq, rq) {
765 array = &rt_rq->active;
766 idx = sched_find_first_bit(array->bitmap);
768 if (idx >= MAX_RT_PRIO)
770 if (next && next->prio < idx)
772 list_for_each_entry(rt_se, array->squeue + idx, run_list) {
773 struct task_struct *p = rt_task_of(rt_se);
774 if (pick_rt_task(rq, p, cpu)) {
780 idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
788 static DEFINE_PER_CPU(cpumask_t, local_cpu_mask);
790 static inline int pick_optimal_cpu(int this_cpu, cpumask_t *mask)
794 /* "this_cpu" is cheaper to preempt than a remote processor */
795 if ((this_cpu != -1) && cpu_isset(this_cpu, *mask))
798 first = first_cpu(*mask);
799 if (first != NR_CPUS)
805 static int find_lowest_rq(struct task_struct *task)
807 struct sched_domain *sd;
808 cpumask_t *lowest_mask = &__get_cpu_var(local_cpu_mask);
809 int this_cpu = smp_processor_id();
810 int cpu = task_cpu(task);
812 if (task->rt.nr_cpus_allowed == 1)
813 return -1; /* No other targets possible */
815 if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
816 return -1; /* No targets found */
819 * At this point we have built a mask of cpus representing the
820 * lowest priority tasks in the system. Now we want to elect
821 * the best one based on our affinity and topology.
823 * We prioritize the last cpu that the task executed on since
824 * it is most likely cache-hot in that location.
826 if (cpu_isset(cpu, *lowest_mask))
830 * Otherwise, we consult the sched_domains span maps to figure
831 * out which cpu is logically closest to our hot cache data.
834 this_cpu = -1; /* Skip this_cpu opt if the same */
836 for_each_domain(cpu, sd) {
837 if (sd->flags & SD_WAKE_AFFINE) {
838 cpumask_t domain_mask;
841 cpus_and(domain_mask, sd->span, *lowest_mask);
843 best_cpu = pick_optimal_cpu(this_cpu,
851 * And finally, if there were no matches within the domains
852 * just give the caller *something* to work with from the compatible
855 return pick_optimal_cpu(this_cpu, lowest_mask);
858 /* Will lock the rq it finds */
859 static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
861 struct rq *lowest_rq = NULL;
865 for (tries = 0; tries < RT_MAX_TRIES; tries++) {
866 cpu = find_lowest_rq(task);
868 if ((cpu == -1) || (cpu == rq->cpu))
871 lowest_rq = cpu_rq(cpu);
873 /* if the prio of this runqueue changed, try again */
874 if (double_lock_balance(rq, lowest_rq)) {
876 * We had to unlock the run queue. In
877 * the mean time, task could have
878 * migrated already or had its affinity changed.
879 * Also make sure that it wasn't scheduled on its rq.
881 if (unlikely(task_rq(task) != rq ||
882 !cpu_isset(lowest_rq->cpu,
883 task->cpus_allowed) ||
884 task_running(rq, task) ||
887 spin_unlock(&lowest_rq->lock);
893 /* If this rq is still suitable use it. */
894 if (lowest_rq->rt.highest_prio > task->prio)
898 spin_unlock(&lowest_rq->lock);
906 * If the current CPU has more than one RT task, see if the non
907 * running task can migrate over to a CPU that is running a task
908 * of lesser priority.
910 static int push_rt_task(struct rq *rq)
912 struct task_struct *next_task;
913 struct rq *lowest_rq;
915 int paranoid = RT_MAX_TRIES;
917 if (!rq->rt.overloaded)
920 next_task = pick_next_highest_task_rt(rq, -1);
925 if (unlikely(next_task == rq->curr)) {
931 * It's possible that the next_task slipped in of
932 * higher priority than current. If that's the case
933 * just reschedule current.
935 if (unlikely(next_task->prio < rq->curr->prio)) {
936 resched_task(rq->curr);
940 /* We might release rq lock */
941 get_task_struct(next_task);
943 /* find_lock_lowest_rq locks the rq if found */
944 lowest_rq = find_lock_lowest_rq(next_task, rq);
946 struct task_struct *task;
948 * find lock_lowest_rq releases rq->lock
949 * so it is possible that next_task has changed.
950 * If it has, then try again.
952 task = pick_next_highest_task_rt(rq, -1);
953 if (unlikely(task != next_task) && task && paranoid--) {
954 put_task_struct(next_task);
961 deactivate_task(rq, next_task, 0);
962 set_task_cpu(next_task, lowest_rq->cpu);
963 activate_task(lowest_rq, next_task, 0);
965 resched_task(lowest_rq->curr);
967 spin_unlock(&lowest_rq->lock);
971 put_task_struct(next_task);
977 * TODO: Currently we just use the second highest prio task on
978 * the queue, and stop when it can't migrate (or there's
979 * no more RT tasks). There may be a case where a lower
980 * priority RT task has a different affinity than the
981 * higher RT task. In this case the lower RT task could
982 * possibly be able to migrate where as the higher priority
983 * RT task could not. We currently ignore this issue.
984 * Enhancements are welcome!
986 static void push_rt_tasks(struct rq *rq)
988 /* push_rt_task will return true if it moved an RT */
989 while (push_rt_task(rq))
993 static int pull_rt_task(struct rq *this_rq)
995 int this_cpu = this_rq->cpu, ret = 0, cpu;
996 struct task_struct *p, *next;
999 if (likely(!rt_overloaded(this_rq)))
1002 next = pick_next_task_rt(this_rq);
1004 for_each_cpu_mask(cpu, this_rq->rd->rto_mask) {
1005 if (this_cpu == cpu)
1008 src_rq = cpu_rq(cpu);
1010 * We can potentially drop this_rq's lock in
1011 * double_lock_balance, and another CPU could
1012 * steal our next task - hence we must cause
1013 * the caller to recalculate the next task
1016 if (double_lock_balance(this_rq, src_rq)) {
1017 struct task_struct *old_next = next;
1019 next = pick_next_task_rt(this_rq);
1020 if (next != old_next)
1025 * Are there still pullable RT tasks?
1027 if (src_rq->rt.rt_nr_running <= 1)
1030 p = pick_next_highest_task_rt(src_rq, this_cpu);
1033 * Do we have an RT task that preempts
1034 * the to-be-scheduled task?
1036 if (p && (!next || (p->prio < next->prio))) {
1037 WARN_ON(p == src_rq->curr);
1038 WARN_ON(!p->se.on_rq);
1041 * There's a chance that p is higher in priority
1042 * than what's currently running on its cpu.
1043 * This is just that p is wakeing up and hasn't
1044 * had a chance to schedule. We only pull
1045 * p if it is lower in priority than the
1046 * current task on the run queue or
1047 * this_rq next task is lower in prio than
1048 * the current task on that rq.
1050 if (p->prio < src_rq->curr->prio ||
1051 (next && next->prio < src_rq->curr->prio))
1056 deactivate_task(src_rq, p, 0);
1057 set_task_cpu(p, this_cpu);
1058 activate_task(this_rq, p, 0);
1060 * We continue with the search, just in
1061 * case there's an even higher prio task
1062 * in another runqueue. (low likelyhood
1065 * Update next so that we won't pick a task
1066 * on another cpu with a priority lower (or equal)
1067 * than the one we just picked.
1073 spin_unlock(&src_rq->lock);
1079 static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
1081 /* Try to pull RT tasks here if we lower this rq's prio */
1082 if (unlikely(rt_task(prev)) && rq->rt.highest_prio > prev->prio)
1086 static void post_schedule_rt(struct rq *rq)
1089 * If we have more than one rt_task queued, then
1090 * see if we can push the other rt_tasks off to other CPUS.
1091 * Note we may release the rq lock, and since
1092 * the lock was owned by prev, we need to release it
1093 * first via finish_lock_switch and then reaquire it here.
1095 if (unlikely(rq->rt.overloaded)) {
1096 spin_lock_irq(&rq->lock);
1098 spin_unlock_irq(&rq->lock);
1103 * If we are not running and we are not going to reschedule soon, we should
1104 * try to push tasks away now
1106 static void task_wake_up_rt(struct rq *rq, struct task_struct *p)
1108 if (!task_running(rq, p) &&
1109 !test_tsk_need_resched(rq->curr) &&
1114 static unsigned long
1115 load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
1116 unsigned long max_load_move,
1117 struct sched_domain *sd, enum cpu_idle_type idle,
1118 int *all_pinned, int *this_best_prio)
1120 /* don't touch RT tasks */
1125 move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
1126 struct sched_domain *sd, enum cpu_idle_type idle)
1128 /* don't touch RT tasks */
1132 static void set_cpus_allowed_rt(struct task_struct *p,
1133 const cpumask_t *new_mask)
1135 int weight = cpus_weight(*new_mask);
1137 BUG_ON(!rt_task(p));
1140 * Update the migration status of the RQ if we have an RT task
1141 * which is running AND changing its weight value.
1143 if (p->se.on_rq && (weight != p->rt.nr_cpus_allowed)) {
1144 struct rq *rq = task_rq(p);
1146 if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
1147 rq->rt.rt_nr_migratory++;
1148 } else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
1149 BUG_ON(!rq->rt.rt_nr_migratory);
1150 rq->rt.rt_nr_migratory--;
1153 update_rt_migration(rq);
1155 if (unlikely(weight == 1 || p->rt.nr_cpus_allowed == 1))
1157 * If either the new or old weight is a "1", we need
1158 * to requeue to properly move between shared and
1161 requeue_task_rt(rq, p);
1164 p->cpus_allowed = *new_mask;
1165 p->rt.nr_cpus_allowed = weight;
1168 /* Assumes rq->lock is held */
1169 static void rq_online_rt(struct rq *rq)
1171 if (rq->rt.overloaded)
1172 rt_set_overload(rq);
1174 cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio);
1177 /* Assumes rq->lock is held */
1178 static void rq_offline_rt(struct rq *rq)
1180 if (rq->rt.overloaded)
1181 rt_clear_overload(rq);
1183 cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
1187 * When switch from the rt queue, we bring ourselves to a position
1188 * that we might want to pull RT tasks from other runqueues.
1190 static void switched_from_rt(struct rq *rq, struct task_struct *p,
1194 * If there are other RT tasks then we will reschedule
1195 * and the scheduling of the other RT tasks will handle
1196 * the balancing. But if we are the last RT task
1197 * we may need to handle the pulling of RT tasks
1200 if (!rq->rt.rt_nr_running)
1203 #endif /* CONFIG_SMP */
1206 * When switching a task to RT, we may overload the runqueue
1207 * with RT tasks. In this case we try to push them off to
1210 static void switched_to_rt(struct rq *rq, struct task_struct *p,
1213 int check_resched = 1;
1216 * If we are already running, then there's nothing
1217 * that needs to be done. But if we are not running
1218 * we may need to preempt the current running task.
1219 * If that current running task is also an RT task
1220 * then see if we can move to another run queue.
1224 if (rq->rt.overloaded && push_rt_task(rq) &&
1225 /* Don't resched if we changed runqueues */
1228 #endif /* CONFIG_SMP */
1229 if (check_resched && p->prio < rq->curr->prio)
1230 resched_task(rq->curr);
1235 * Priority of the task has changed. This may cause
1236 * us to initiate a push or pull.
1238 static void prio_changed_rt(struct rq *rq, struct task_struct *p,
1239 int oldprio, int running)
1244 * If our priority decreases while running, we
1245 * may need to pull tasks to this runqueue.
1247 if (oldprio < p->prio)
1250 * If there's a higher priority task waiting to run
1251 * then reschedule. Note, the above pull_rt_task
1252 * can release the rq lock and p could migrate.
1253 * Only reschedule if p is still on the same runqueue.
1255 if (p->prio > rq->rt.highest_prio && rq->curr == p)
1258 /* For UP simply resched on drop of prio */
1259 if (oldprio < p->prio)
1261 #endif /* CONFIG_SMP */
1264 * This task is not running, but if it is
1265 * greater than the current running task
1268 if (p->prio < rq->curr->prio)
1269 resched_task(rq->curr);
1273 static void watchdog(struct rq *rq, struct task_struct *p)
1275 unsigned long soft, hard;
1280 soft = p->signal->rlim[RLIMIT_RTTIME].rlim_cur;
1281 hard = p->signal->rlim[RLIMIT_RTTIME].rlim_max;
1283 if (soft != RLIM_INFINITY) {
1287 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
1288 if (p->rt.timeout > next)
1289 p->it_sched_expires = p->se.sum_exec_runtime;
1293 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
1300 * RR tasks need a special form of timeslice management.
1301 * FIFO tasks have no timeslices.
1303 if (p->policy != SCHED_RR)
1306 if (--p->rt.time_slice)
1309 p->rt.time_slice = DEF_TIMESLICE;
1312 * Requeue to the end of queue if we are not the only element
1315 if (p->rt.run_list.prev != p->rt.run_list.next) {
1316 requeue_task_rt(rq, p);
1317 set_tsk_need_resched(p);
1321 static void set_curr_task_rt(struct rq *rq)
1323 struct task_struct *p = rq->curr;
1325 p->se.exec_start = rq->clock;
1328 static const struct sched_class rt_sched_class = {
1329 .next = &fair_sched_class,
1330 .enqueue_task = enqueue_task_rt,
1331 .dequeue_task = dequeue_task_rt,
1332 .yield_task = yield_task_rt,
1334 .select_task_rq = select_task_rq_rt,
1335 #endif /* CONFIG_SMP */
1337 .check_preempt_curr = check_preempt_curr_rt,
1339 .pick_next_task = pick_next_task_rt,
1340 .put_prev_task = put_prev_task_rt,
1343 .load_balance = load_balance_rt,
1344 .move_one_task = move_one_task_rt,
1345 .set_cpus_allowed = set_cpus_allowed_rt,
1346 .rq_online = rq_online_rt,
1347 .rq_offline = rq_offline_rt,
1348 .pre_schedule = pre_schedule_rt,
1349 .post_schedule = post_schedule_rt,
1350 .task_wake_up = task_wake_up_rt,
1351 .switched_from = switched_from_rt,
1354 .set_curr_task = set_curr_task_rt,
1355 .task_tick = task_tick_rt,
1357 .prio_changed = prio_changed_rt,
1358 .switched_to = switched_to_rt,