Merge commit 'v2.6.29-rc7' into perfcounters/core
[linux-2.6.git] / kernel / sched_rt.c
1 /*
2  * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
3  * policies)
4  */
5
6 #ifdef CONFIG_SMP
7
8 static inline int rt_overloaded(struct rq *rq)
9 {
10         return atomic_read(&rq->rd->rto_count);
11 }
12
13 static inline void rt_set_overload(struct rq *rq)
14 {
15         if (!rq->online)
16                 return;
17
18         cpumask_set_cpu(rq->cpu, rq->rd->rto_mask);
19         /*
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
24          * updated yet.
25          */
26         wmb();
27         atomic_inc(&rq->rd->rto_count);
28 }
29
30 static inline void rt_clear_overload(struct rq *rq)
31 {
32         if (!rq->online)
33                 return;
34
35         /* the order here really doesn't matter */
36         atomic_dec(&rq->rd->rto_count);
37         cpumask_clear_cpu(rq->cpu, rq->rd->rto_mask);
38 }
39
40 static void update_rt_migration(struct rq *rq)
41 {
42         if (rq->rt.rt_nr_migratory && (rq->rt.rt_nr_running > 1)) {
43                 if (!rq->rt.overloaded) {
44                         rt_set_overload(rq);
45                         rq->rt.overloaded = 1;
46                 }
47         } else if (rq->rt.overloaded) {
48                 rt_clear_overload(rq);
49                 rq->rt.overloaded = 0;
50         }
51 }
52 #endif /* CONFIG_SMP */
53
54 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
55 {
56         return container_of(rt_se, struct task_struct, rt);
57 }
58
59 static inline int on_rt_rq(struct sched_rt_entity *rt_se)
60 {
61         return !list_empty(&rt_se->run_list);
62 }
63
64 #ifdef CONFIG_RT_GROUP_SCHED
65
66 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
67 {
68         if (!rt_rq->tg)
69                 return RUNTIME_INF;
70
71         return rt_rq->rt_runtime;
72 }
73
74 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
75 {
76         return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
77 }
78
79 #define for_each_leaf_rt_rq(rt_rq, rq) \
80         list_for_each_entry_rcu(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
81
82 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
83 {
84         return rt_rq->rq;
85 }
86
87 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
88 {
89         return rt_se->rt_rq;
90 }
91
92 #define for_each_sched_rt_entity(rt_se) \
93         for (; rt_se; rt_se = rt_se->parent)
94
95 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
96 {
97         return rt_se->my_q;
98 }
99
100 static void enqueue_rt_entity(struct sched_rt_entity *rt_se);
101 static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
102
103 static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
104 {
105         struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
106         struct sched_rt_entity *rt_se = rt_rq->rt_se;
107
108         if (rt_rq->rt_nr_running) {
109                 if (rt_se && !on_rt_rq(rt_se))
110                         enqueue_rt_entity(rt_se);
111                 if (rt_rq->highest_prio < curr->prio)
112                         resched_task(curr);
113         }
114 }
115
116 static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
117 {
118         struct sched_rt_entity *rt_se = rt_rq->rt_se;
119
120         if (rt_se && on_rt_rq(rt_se))
121                 dequeue_rt_entity(rt_se);
122 }
123
124 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
125 {
126         return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
127 }
128
129 static int rt_se_boosted(struct sched_rt_entity *rt_se)
130 {
131         struct rt_rq *rt_rq = group_rt_rq(rt_se);
132         struct task_struct *p;
133
134         if (rt_rq)
135                 return !!rt_rq->rt_nr_boosted;
136
137         p = rt_task_of(rt_se);
138         return p->prio != p->normal_prio;
139 }
140
141 #ifdef CONFIG_SMP
142 static inline const struct cpumask *sched_rt_period_mask(void)
143 {
144         return cpu_rq(smp_processor_id())->rd->span;
145 }
146 #else
147 static inline const struct cpumask *sched_rt_period_mask(void)
148 {
149         return cpu_online_mask;
150 }
151 #endif
152
153 static inline
154 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
155 {
156         return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
157 }
158
159 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
160 {
161         return &rt_rq->tg->rt_bandwidth;
162 }
163
164 #else /* !CONFIG_RT_GROUP_SCHED */
165
166 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
167 {
168         return rt_rq->rt_runtime;
169 }
170
171 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
172 {
173         return ktime_to_ns(def_rt_bandwidth.rt_period);
174 }
175
176 #define for_each_leaf_rt_rq(rt_rq, rq) \
177         for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
178
179 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
180 {
181         return container_of(rt_rq, struct rq, rt);
182 }
183
184 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
185 {
186         struct task_struct *p = rt_task_of(rt_se);
187         struct rq *rq = task_rq(p);
188
189         return &rq->rt;
190 }
191
192 #define for_each_sched_rt_entity(rt_se) \
193         for (; rt_se; rt_se = NULL)
194
195 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
196 {
197         return NULL;
198 }
199
200 static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
201 {
202         if (rt_rq->rt_nr_running)
203                 resched_task(rq_of_rt_rq(rt_rq)->curr);
204 }
205
206 static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
207 {
208 }
209
210 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
211 {
212         return rt_rq->rt_throttled;
213 }
214
215 static inline const struct cpumask *sched_rt_period_mask(void)
216 {
217         return cpu_online_mask;
218 }
219
220 static inline
221 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
222 {
223         return &cpu_rq(cpu)->rt;
224 }
225
226 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
227 {
228         return &def_rt_bandwidth;
229 }
230
231 #endif /* CONFIG_RT_GROUP_SCHED */
232
233 #ifdef CONFIG_SMP
234 /*
235  * We ran out of runtime, see if we can borrow some from our neighbours.
236  */
237 static int do_balance_runtime(struct rt_rq *rt_rq)
238 {
239         struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
240         struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
241         int i, weight, more = 0;
242         u64 rt_period;
243
244         weight = cpumask_weight(rd->span);
245
246         spin_lock(&rt_b->rt_runtime_lock);
247         rt_period = ktime_to_ns(rt_b->rt_period);
248         for_each_cpu(i, rd->span) {
249                 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
250                 s64 diff;
251
252                 if (iter == rt_rq)
253                         continue;
254
255                 spin_lock(&iter->rt_runtime_lock);
256                 /*
257                  * Either all rqs have inf runtime and there's nothing to steal
258                  * or __disable_runtime() below sets a specific rq to inf to
259                  * indicate its been disabled and disalow stealing.
260                  */
261                 if (iter->rt_runtime == RUNTIME_INF)
262                         goto next;
263
264                 /*
265                  * From runqueues with spare time, take 1/n part of their
266                  * spare time, but no more than our period.
267                  */
268                 diff = iter->rt_runtime - iter->rt_time;
269                 if (diff > 0) {
270                         diff = div_u64((u64)diff, weight);
271                         if (rt_rq->rt_runtime + diff > rt_period)
272                                 diff = rt_period - rt_rq->rt_runtime;
273                         iter->rt_runtime -= diff;
274                         rt_rq->rt_runtime += diff;
275                         more = 1;
276                         if (rt_rq->rt_runtime == rt_period) {
277                                 spin_unlock(&iter->rt_runtime_lock);
278                                 break;
279                         }
280                 }
281 next:
282                 spin_unlock(&iter->rt_runtime_lock);
283         }
284         spin_unlock(&rt_b->rt_runtime_lock);
285
286         return more;
287 }
288
289 /*
290  * Ensure this RQ takes back all the runtime it lend to its neighbours.
291  */
292 static void __disable_runtime(struct rq *rq)
293 {
294         struct root_domain *rd = rq->rd;
295         struct rt_rq *rt_rq;
296
297         if (unlikely(!scheduler_running))
298                 return;
299
300         for_each_leaf_rt_rq(rt_rq, rq) {
301                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
302                 s64 want;
303                 int i;
304
305                 spin_lock(&rt_b->rt_runtime_lock);
306                 spin_lock(&rt_rq->rt_runtime_lock);
307                 /*
308                  * Either we're all inf and nobody needs to borrow, or we're
309                  * already disabled and thus have nothing to do, or we have
310                  * exactly the right amount of runtime to take out.
311                  */
312                 if (rt_rq->rt_runtime == RUNTIME_INF ||
313                                 rt_rq->rt_runtime == rt_b->rt_runtime)
314                         goto balanced;
315                 spin_unlock(&rt_rq->rt_runtime_lock);
316
317                 /*
318                  * Calculate the difference between what we started out with
319                  * and what we current have, that's the amount of runtime
320                  * we lend and now have to reclaim.
321                  */
322                 want = rt_b->rt_runtime - rt_rq->rt_runtime;
323
324                 /*
325                  * Greedy reclaim, take back as much as we can.
326                  */
327                 for_each_cpu(i, rd->span) {
328                         struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
329                         s64 diff;
330
331                         /*
332                          * Can't reclaim from ourselves or disabled runqueues.
333                          */
334                         if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
335                                 continue;
336
337                         spin_lock(&iter->rt_runtime_lock);
338                         if (want > 0) {
339                                 diff = min_t(s64, iter->rt_runtime, want);
340                                 iter->rt_runtime -= diff;
341                                 want -= diff;
342                         } else {
343                                 iter->rt_runtime -= want;
344                                 want -= want;
345                         }
346                         spin_unlock(&iter->rt_runtime_lock);
347
348                         if (!want)
349                                 break;
350                 }
351
352                 spin_lock(&rt_rq->rt_runtime_lock);
353                 /*
354                  * We cannot be left wanting - that would mean some runtime
355                  * leaked out of the system.
356                  */
357                 BUG_ON(want);
358 balanced:
359                 /*
360                  * Disable all the borrow logic by pretending we have inf
361                  * runtime - in which case borrowing doesn't make sense.
362                  */
363                 rt_rq->rt_runtime = RUNTIME_INF;
364                 spin_unlock(&rt_rq->rt_runtime_lock);
365                 spin_unlock(&rt_b->rt_runtime_lock);
366         }
367 }
368
369 static void disable_runtime(struct rq *rq)
370 {
371         unsigned long flags;
372
373         spin_lock_irqsave(&rq->lock, flags);
374         __disable_runtime(rq);
375         spin_unlock_irqrestore(&rq->lock, flags);
376 }
377
378 static void __enable_runtime(struct rq *rq)
379 {
380         struct rt_rq *rt_rq;
381
382         if (unlikely(!scheduler_running))
383                 return;
384
385         /*
386          * Reset each runqueue's bandwidth settings
387          */
388         for_each_leaf_rt_rq(rt_rq, rq) {
389                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
390
391                 spin_lock(&rt_b->rt_runtime_lock);
392                 spin_lock(&rt_rq->rt_runtime_lock);
393                 rt_rq->rt_runtime = rt_b->rt_runtime;
394                 rt_rq->rt_time = 0;
395                 rt_rq->rt_throttled = 0;
396                 spin_unlock(&rt_rq->rt_runtime_lock);
397                 spin_unlock(&rt_b->rt_runtime_lock);
398         }
399 }
400
401 static void enable_runtime(struct rq *rq)
402 {
403         unsigned long flags;
404
405         spin_lock_irqsave(&rq->lock, flags);
406         __enable_runtime(rq);
407         spin_unlock_irqrestore(&rq->lock, flags);
408 }
409
410 static int balance_runtime(struct rt_rq *rt_rq)
411 {
412         int more = 0;
413
414         if (rt_rq->rt_time > rt_rq->rt_runtime) {
415                 spin_unlock(&rt_rq->rt_runtime_lock);
416                 more = do_balance_runtime(rt_rq);
417                 spin_lock(&rt_rq->rt_runtime_lock);
418         }
419
420         return more;
421 }
422 #else /* !CONFIG_SMP */
423 static inline int balance_runtime(struct rt_rq *rt_rq)
424 {
425         return 0;
426 }
427 #endif /* CONFIG_SMP */
428
429 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
430 {
431         int i, idle = 1;
432         const struct cpumask *span;
433
434         if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
435                 return 1;
436
437         span = sched_rt_period_mask();
438         for_each_cpu(i, span) {
439                 int enqueue = 0;
440                 struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
441                 struct rq *rq = rq_of_rt_rq(rt_rq);
442
443                 spin_lock(&rq->lock);
444                 if (rt_rq->rt_time) {
445                         u64 runtime;
446
447                         spin_lock(&rt_rq->rt_runtime_lock);
448                         if (rt_rq->rt_throttled)
449                                 balance_runtime(rt_rq);
450                         runtime = rt_rq->rt_runtime;
451                         rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
452                         if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
453                                 rt_rq->rt_throttled = 0;
454                                 enqueue = 1;
455                         }
456                         if (rt_rq->rt_time || rt_rq->rt_nr_running)
457                                 idle = 0;
458                         spin_unlock(&rt_rq->rt_runtime_lock);
459                 } else if (rt_rq->rt_nr_running)
460                         idle = 0;
461
462                 if (enqueue)
463                         sched_rt_rq_enqueue(rt_rq);
464                 spin_unlock(&rq->lock);
465         }
466
467         return idle;
468 }
469
470 static inline int rt_se_prio(struct sched_rt_entity *rt_se)
471 {
472 #ifdef CONFIG_RT_GROUP_SCHED
473         struct rt_rq *rt_rq = group_rt_rq(rt_se);
474
475         if (rt_rq)
476                 return rt_rq->highest_prio;
477 #endif
478
479         return rt_task_of(rt_se)->prio;
480 }
481
482 static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
483 {
484         u64 runtime = sched_rt_runtime(rt_rq);
485
486         if (rt_rq->rt_throttled)
487                 return rt_rq_throttled(rt_rq);
488
489         if (sched_rt_runtime(rt_rq) >= sched_rt_period(rt_rq))
490                 return 0;
491
492         balance_runtime(rt_rq);
493         runtime = sched_rt_runtime(rt_rq);
494         if (runtime == RUNTIME_INF)
495                 return 0;
496
497         if (rt_rq->rt_time > runtime) {
498                 rt_rq->rt_throttled = 1;
499                 if (rt_rq_throttled(rt_rq)) {
500                         sched_rt_rq_dequeue(rt_rq);
501                         return 1;
502                 }
503         }
504
505         return 0;
506 }
507
508 /*
509  * Update the current task's runtime statistics. Skip current tasks that
510  * are not in our scheduling class.
511  */
512 static void update_curr_rt(struct rq *rq)
513 {
514         struct task_struct *curr = rq->curr;
515         struct sched_rt_entity *rt_se = &curr->rt;
516         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
517         u64 delta_exec;
518
519         if (!task_has_rt_policy(curr))
520                 return;
521
522         delta_exec = rq->clock - curr->se.exec_start;
523         if (unlikely((s64)delta_exec < 0))
524                 delta_exec = 0;
525
526         schedstat_set(curr->se.exec_max, max(curr->se.exec_max, delta_exec));
527
528         curr->se.sum_exec_runtime += delta_exec;
529         account_group_exec_runtime(curr, delta_exec);
530
531         curr->se.exec_start = rq->clock;
532         cpuacct_charge(curr, delta_exec);
533
534         if (!rt_bandwidth_enabled())
535                 return;
536
537         for_each_sched_rt_entity(rt_se) {
538                 rt_rq = rt_rq_of_se(rt_se);
539
540                 if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
541                         spin_lock(&rt_rq->rt_runtime_lock);
542                         rt_rq->rt_time += delta_exec;
543                         if (sched_rt_runtime_exceeded(rt_rq))
544                                 resched_task(curr);
545                         spin_unlock(&rt_rq->rt_runtime_lock);
546                 }
547         }
548 }
549
550 static inline
551 void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
552 {
553         WARN_ON(!rt_prio(rt_se_prio(rt_se)));
554         rt_rq->rt_nr_running++;
555 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
556         if (rt_se_prio(rt_se) < rt_rq->highest_prio) {
557 #ifdef CONFIG_SMP
558                 struct rq *rq = rq_of_rt_rq(rt_rq);
559 #endif
560
561                 rt_rq->highest_prio = rt_se_prio(rt_se);
562 #ifdef CONFIG_SMP
563                 if (rq->online)
564                         cpupri_set(&rq->rd->cpupri, rq->cpu,
565                                    rt_se_prio(rt_se));
566 #endif
567         }
568 #endif
569 #ifdef CONFIG_SMP
570         if (rt_se->nr_cpus_allowed > 1) {
571                 struct rq *rq = rq_of_rt_rq(rt_rq);
572
573                 rq->rt.rt_nr_migratory++;
574         }
575
576         update_rt_migration(rq_of_rt_rq(rt_rq));
577 #endif
578 #ifdef CONFIG_RT_GROUP_SCHED
579         if (rt_se_boosted(rt_se))
580                 rt_rq->rt_nr_boosted++;
581
582         if (rt_rq->tg)
583                 start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
584 #else
585         start_rt_bandwidth(&def_rt_bandwidth);
586 #endif
587 }
588
589 static inline
590 void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
591 {
592 #ifdef CONFIG_SMP
593         int highest_prio = rt_rq->highest_prio;
594 #endif
595
596         WARN_ON(!rt_prio(rt_se_prio(rt_se)));
597         WARN_ON(!rt_rq->rt_nr_running);
598         rt_rq->rt_nr_running--;
599 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
600         if (rt_rq->rt_nr_running) {
601                 struct rt_prio_array *array;
602
603                 WARN_ON(rt_se_prio(rt_se) < rt_rq->highest_prio);
604                 if (rt_se_prio(rt_se) == rt_rq->highest_prio) {
605                         /* recalculate */
606                         array = &rt_rq->active;
607                         rt_rq->highest_prio =
608                                 sched_find_first_bit(array->bitmap);
609                 } /* otherwise leave rq->highest prio alone */
610         } else
611                 rt_rq->highest_prio = MAX_RT_PRIO;
612 #endif
613 #ifdef CONFIG_SMP
614         if (rt_se->nr_cpus_allowed > 1) {
615                 struct rq *rq = rq_of_rt_rq(rt_rq);
616                 rq->rt.rt_nr_migratory--;
617         }
618
619         if (rt_rq->highest_prio != highest_prio) {
620                 struct rq *rq = rq_of_rt_rq(rt_rq);
621
622                 if (rq->online)
623                         cpupri_set(&rq->rd->cpupri, rq->cpu,
624                                    rt_rq->highest_prio);
625         }
626
627         update_rt_migration(rq_of_rt_rq(rt_rq));
628 #endif /* CONFIG_SMP */
629 #ifdef CONFIG_RT_GROUP_SCHED
630         if (rt_se_boosted(rt_se))
631                 rt_rq->rt_nr_boosted--;
632
633         WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
634 #endif
635 }
636
637 static void __enqueue_rt_entity(struct sched_rt_entity *rt_se)
638 {
639         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
640         struct rt_prio_array *array = &rt_rq->active;
641         struct rt_rq *group_rq = group_rt_rq(rt_se);
642         struct list_head *queue = array->queue + rt_se_prio(rt_se);
643
644         /*
645          * Don't enqueue the group if its throttled, or when empty.
646          * The latter is a consequence of the former when a child group
647          * get throttled and the current group doesn't have any other
648          * active members.
649          */
650         if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
651                 return;
652
653         list_add_tail(&rt_se->run_list, queue);
654         __set_bit(rt_se_prio(rt_se), array->bitmap);
655
656         inc_rt_tasks(rt_se, rt_rq);
657 }
658
659 static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
660 {
661         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
662         struct rt_prio_array *array = &rt_rq->active;
663
664         list_del_init(&rt_se->run_list);
665         if (list_empty(array->queue + rt_se_prio(rt_se)))
666                 __clear_bit(rt_se_prio(rt_se), array->bitmap);
667
668         dec_rt_tasks(rt_se, rt_rq);
669 }
670
671 /*
672  * Because the prio of an upper entry depends on the lower
673  * entries, we must remove entries top - down.
674  */
675 static void dequeue_rt_stack(struct sched_rt_entity *rt_se)
676 {
677         struct sched_rt_entity *back = NULL;
678
679         for_each_sched_rt_entity(rt_se) {
680                 rt_se->back = back;
681                 back = rt_se;
682         }
683
684         for (rt_se = back; rt_se; rt_se = rt_se->back) {
685                 if (on_rt_rq(rt_se))
686                         __dequeue_rt_entity(rt_se);
687         }
688 }
689
690 static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
691 {
692         dequeue_rt_stack(rt_se);
693         for_each_sched_rt_entity(rt_se)
694                 __enqueue_rt_entity(rt_se);
695 }
696
697 static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
698 {
699         dequeue_rt_stack(rt_se);
700
701         for_each_sched_rt_entity(rt_se) {
702                 struct rt_rq *rt_rq = group_rt_rq(rt_se);
703
704                 if (rt_rq && rt_rq->rt_nr_running)
705                         __enqueue_rt_entity(rt_se);
706         }
707 }
708
709 /*
710  * Adding/removing a task to/from a priority array:
711  */
712 static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
713 {
714         struct sched_rt_entity *rt_se = &p->rt;
715
716         if (wakeup)
717                 rt_se->timeout = 0;
718
719         enqueue_rt_entity(rt_se);
720
721         inc_cpu_load(rq, p->se.load.weight);
722 }
723
724 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
725 {
726         struct sched_rt_entity *rt_se = &p->rt;
727
728         update_curr_rt(rq);
729         dequeue_rt_entity(rt_se);
730
731         dec_cpu_load(rq, p->se.load.weight);
732 }
733
734 /*
735  * Put task to the end of the run list without the overhead of dequeue
736  * followed by enqueue.
737  */
738 static void
739 requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
740 {
741         if (on_rt_rq(rt_se)) {
742                 struct rt_prio_array *array = &rt_rq->active;
743                 struct list_head *queue = array->queue + rt_se_prio(rt_se);
744
745                 if (head)
746                         list_move(&rt_se->run_list, queue);
747                 else
748                         list_move_tail(&rt_se->run_list, queue);
749         }
750 }
751
752 static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
753 {
754         struct sched_rt_entity *rt_se = &p->rt;
755         struct rt_rq *rt_rq;
756
757         for_each_sched_rt_entity(rt_se) {
758                 rt_rq = rt_rq_of_se(rt_se);
759                 requeue_rt_entity(rt_rq, rt_se, head);
760         }
761 }
762
763 static void yield_task_rt(struct rq *rq)
764 {
765         requeue_task_rt(rq, rq->curr, 0);
766 }
767
768 #ifdef CONFIG_SMP
769 static int find_lowest_rq(struct task_struct *task);
770
771 static int select_task_rq_rt(struct task_struct *p, int sync)
772 {
773         struct rq *rq = task_rq(p);
774
775         /*
776          * If the current task is an RT task, then
777          * try to see if we can wake this RT task up on another
778          * runqueue. Otherwise simply start this RT task
779          * on its current runqueue.
780          *
781          * We want to avoid overloading runqueues. Even if
782          * the RT task is of higher priority than the current RT task.
783          * RT tasks behave differently than other tasks. If
784          * one gets preempted, we try to push it off to another queue.
785          * So trying to keep a preempting RT task on the same
786          * cache hot CPU will force the running RT task to
787          * a cold CPU. So we waste all the cache for the lower
788          * RT task in hopes of saving some of a RT task
789          * that is just being woken and probably will have
790          * cold cache anyway.
791          */
792         if (unlikely(rt_task(rq->curr)) &&
793             (p->rt.nr_cpus_allowed > 1)) {
794                 int cpu = find_lowest_rq(p);
795
796                 return (cpu == -1) ? task_cpu(p) : cpu;
797         }
798
799         /*
800          * Otherwise, just let it ride on the affined RQ and the
801          * post-schedule router will push the preempted task away
802          */
803         return task_cpu(p);
804 }
805
806 static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
807 {
808         cpumask_var_t mask;
809
810         if (rq->curr->rt.nr_cpus_allowed == 1)
811                 return;
812
813         if (!alloc_cpumask_var(&mask, GFP_ATOMIC))
814                 return;
815
816         if (p->rt.nr_cpus_allowed != 1
817             && cpupri_find(&rq->rd->cpupri, p, mask))
818                 goto free;
819
820         if (!cpupri_find(&rq->rd->cpupri, rq->curr, mask))
821                 goto free;
822
823         /*
824          * There appears to be other cpus that can accept
825          * current and none to run 'p', so lets reschedule
826          * to try and push current away:
827          */
828         requeue_task_rt(rq, p, 1);
829         resched_task(rq->curr);
830 free:
831         free_cpumask_var(mask);
832 }
833
834 #endif /* CONFIG_SMP */
835
836 /*
837  * Preempt the current task with a newly woken task if needed:
838  */
839 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int sync)
840 {
841         if (p->prio < rq->curr->prio) {
842                 resched_task(rq->curr);
843                 return;
844         }
845
846 #ifdef CONFIG_SMP
847         /*
848          * If:
849          *
850          * - the newly woken task is of equal priority to the current task
851          * - the newly woken task is non-migratable while current is migratable
852          * - current will be preempted on the next reschedule
853          *
854          * we should check to see if current can readily move to a different
855          * cpu.  If so, we will reschedule to allow the push logic to try
856          * to move current somewhere else, making room for our non-migratable
857          * task.
858          */
859         if (p->prio == rq->curr->prio && !need_resched())
860                 check_preempt_equal_prio(rq, p);
861 #endif
862 }
863
864 static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
865                                                    struct rt_rq *rt_rq)
866 {
867         struct rt_prio_array *array = &rt_rq->active;
868         struct sched_rt_entity *next = NULL;
869         struct list_head *queue;
870         int idx;
871
872         idx = sched_find_first_bit(array->bitmap);
873         BUG_ON(idx >= MAX_RT_PRIO);
874
875         queue = array->queue + idx;
876         next = list_entry(queue->next, struct sched_rt_entity, run_list);
877
878         return next;
879 }
880
881 static struct task_struct *pick_next_task_rt(struct rq *rq)
882 {
883         struct sched_rt_entity *rt_se;
884         struct task_struct *p;
885         struct rt_rq *rt_rq;
886
887         rt_rq = &rq->rt;
888
889         if (unlikely(!rt_rq->rt_nr_running))
890                 return NULL;
891
892         if (rt_rq_throttled(rt_rq))
893                 return NULL;
894
895         do {
896                 rt_se = pick_next_rt_entity(rq, rt_rq);
897                 BUG_ON(!rt_se);
898                 rt_rq = group_rt_rq(rt_se);
899         } while (rt_rq);
900
901         p = rt_task_of(rt_se);
902         p->se.exec_start = rq->clock;
903         return p;
904 }
905
906 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
907 {
908         update_curr_rt(rq);
909         p->se.exec_start = 0;
910 }
911
912 #ifdef CONFIG_SMP
913
914 /* Only try algorithms three times */
915 #define RT_MAX_TRIES 3
916
917 static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
918
919 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
920 {
921         if (!task_running(rq, p) &&
922             (cpu < 0 || cpumask_test_cpu(cpu, &p->cpus_allowed)) &&
923             (p->rt.nr_cpus_allowed > 1))
924                 return 1;
925         return 0;
926 }
927
928 /* Return the second highest RT task, NULL otherwise */
929 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
930 {
931         struct task_struct *next = NULL;
932         struct sched_rt_entity *rt_se;
933         struct rt_prio_array *array;
934         struct rt_rq *rt_rq;
935         int idx;
936
937         for_each_leaf_rt_rq(rt_rq, rq) {
938                 array = &rt_rq->active;
939                 idx = sched_find_first_bit(array->bitmap);
940  next_idx:
941                 if (idx >= MAX_RT_PRIO)
942                         continue;
943                 if (next && next->prio < idx)
944                         continue;
945                 list_for_each_entry(rt_se, array->queue + idx, run_list) {
946                         struct task_struct *p = rt_task_of(rt_se);
947                         if (pick_rt_task(rq, p, cpu)) {
948                                 next = p;
949                                 break;
950                         }
951                 }
952                 if (!next) {
953                         idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
954                         goto next_idx;
955                 }
956         }
957
958         return next;
959 }
960
961 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
962
963 static inline int pick_optimal_cpu(int this_cpu,
964                                    const struct cpumask *mask)
965 {
966         int first;
967
968         /* "this_cpu" is cheaper to preempt than a remote processor */
969         if ((this_cpu != -1) && cpumask_test_cpu(this_cpu, mask))
970                 return this_cpu;
971
972         first = cpumask_first(mask);
973         if (first < nr_cpu_ids)
974                 return first;
975
976         return -1;
977 }
978
979 static int find_lowest_rq(struct task_struct *task)
980 {
981         struct sched_domain *sd;
982         struct cpumask *lowest_mask = __get_cpu_var(local_cpu_mask);
983         int this_cpu = smp_processor_id();
984         int cpu      = task_cpu(task);
985         cpumask_var_t domain_mask;
986
987         if (task->rt.nr_cpus_allowed == 1)
988                 return -1; /* No other targets possible */
989
990         if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
991                 return -1; /* No targets found */
992
993         /*
994          * Only consider CPUs that are usable for migration.
995          * I guess we might want to change cpupri_find() to ignore those
996          * in the first place.
997          */
998         cpumask_and(lowest_mask, lowest_mask, cpu_active_mask);
999
1000         /*
1001          * At this point we have built a mask of cpus representing the
1002          * lowest priority tasks in the system.  Now we want to elect
1003          * the best one based on our affinity and topology.
1004          *
1005          * We prioritize the last cpu that the task executed on since
1006          * it is most likely cache-hot in that location.
1007          */
1008         if (cpumask_test_cpu(cpu, lowest_mask))
1009                 return cpu;
1010
1011         /*
1012          * Otherwise, we consult the sched_domains span maps to figure
1013          * out which cpu is logically closest to our hot cache data.
1014          */
1015         if (this_cpu == cpu)
1016                 this_cpu = -1; /* Skip this_cpu opt if the same */
1017
1018         if (alloc_cpumask_var(&domain_mask, GFP_ATOMIC)) {
1019                 for_each_domain(cpu, sd) {
1020                         if (sd->flags & SD_WAKE_AFFINE) {
1021                                 int best_cpu;
1022
1023                                 cpumask_and(domain_mask,
1024                                             sched_domain_span(sd),
1025                                             lowest_mask);
1026
1027                                 best_cpu = pick_optimal_cpu(this_cpu,
1028                                                             domain_mask);
1029
1030                                 if (best_cpu != -1) {
1031                                         free_cpumask_var(domain_mask);
1032                                         return best_cpu;
1033                                 }
1034                         }
1035                 }
1036                 free_cpumask_var(domain_mask);
1037         }
1038
1039         /*
1040          * And finally, if there were no matches within the domains
1041          * just give the caller *something* to work with from the compatible
1042          * locations.
1043          */
1044         return pick_optimal_cpu(this_cpu, lowest_mask);
1045 }
1046
1047 /* Will lock the rq it finds */
1048 static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1049 {
1050         struct rq *lowest_rq = NULL;
1051         int tries;
1052         int cpu;
1053
1054         for (tries = 0; tries < RT_MAX_TRIES; tries++) {
1055                 cpu = find_lowest_rq(task);
1056
1057                 if ((cpu == -1) || (cpu == rq->cpu))
1058                         break;
1059
1060                 lowest_rq = cpu_rq(cpu);
1061
1062                 /* if the prio of this runqueue changed, try again */
1063                 if (double_lock_balance(rq, lowest_rq)) {
1064                         /*
1065                          * We had to unlock the run queue. In
1066                          * the mean time, task could have
1067                          * migrated already or had its affinity changed.
1068                          * Also make sure that it wasn't scheduled on its rq.
1069                          */
1070                         if (unlikely(task_rq(task) != rq ||
1071                                      !cpumask_test_cpu(lowest_rq->cpu,
1072                                                        &task->cpus_allowed) ||
1073                                      task_running(rq, task) ||
1074                                      !task->se.on_rq)) {
1075
1076                                 spin_unlock(&lowest_rq->lock);
1077                                 lowest_rq = NULL;
1078                                 break;
1079                         }
1080                 }
1081
1082                 /* If this rq is still suitable use it. */
1083                 if (lowest_rq->rt.highest_prio > task->prio)
1084                         break;
1085
1086                 /* try again */
1087                 double_unlock_balance(rq, lowest_rq);
1088                 lowest_rq = NULL;
1089         }
1090
1091         return lowest_rq;
1092 }
1093
1094 /*
1095  * If the current CPU has more than one RT task, see if the non
1096  * running task can migrate over to a CPU that is running a task
1097  * of lesser priority.
1098  */
1099 static int push_rt_task(struct rq *rq)
1100 {
1101         struct task_struct *next_task;
1102         struct rq *lowest_rq;
1103         int ret = 0;
1104         int paranoid = RT_MAX_TRIES;
1105
1106         if (!rq->rt.overloaded)
1107                 return 0;
1108
1109         next_task = pick_next_highest_task_rt(rq, -1);
1110         if (!next_task)
1111                 return 0;
1112
1113  retry:
1114         if (unlikely(next_task == rq->curr)) {
1115                 WARN_ON(1);
1116                 return 0;
1117         }
1118
1119         /*
1120          * It's possible that the next_task slipped in of
1121          * higher priority than current. If that's the case
1122          * just reschedule current.
1123          */
1124         if (unlikely(next_task->prio < rq->curr->prio)) {
1125                 resched_task(rq->curr);
1126                 return 0;
1127         }
1128
1129         /* We might release rq lock */
1130         get_task_struct(next_task);
1131
1132         /* find_lock_lowest_rq locks the rq if found */
1133         lowest_rq = find_lock_lowest_rq(next_task, rq);
1134         if (!lowest_rq) {
1135                 struct task_struct *task;
1136                 /*
1137                  * find lock_lowest_rq releases rq->lock
1138                  * so it is possible that next_task has changed.
1139                  * If it has, then try again.
1140                  */
1141                 task = pick_next_highest_task_rt(rq, -1);
1142                 if (unlikely(task != next_task) && task && paranoid--) {
1143                         put_task_struct(next_task);
1144                         next_task = task;
1145                         goto retry;
1146                 }
1147                 goto out;
1148         }
1149
1150         deactivate_task(rq, next_task, 0);
1151         set_task_cpu(next_task, lowest_rq->cpu);
1152         activate_task(lowest_rq, next_task, 0);
1153
1154         resched_task(lowest_rq->curr);
1155
1156         double_unlock_balance(rq, lowest_rq);
1157
1158         ret = 1;
1159 out:
1160         put_task_struct(next_task);
1161
1162         return ret;
1163 }
1164
1165 /*
1166  * TODO: Currently we just use the second highest prio task on
1167  *       the queue, and stop when it can't migrate (or there's
1168  *       no more RT tasks).  There may be a case where a lower
1169  *       priority RT task has a different affinity than the
1170  *       higher RT task. In this case the lower RT task could
1171  *       possibly be able to migrate where as the higher priority
1172  *       RT task could not.  We currently ignore this issue.
1173  *       Enhancements are welcome!
1174  */
1175 static void push_rt_tasks(struct rq *rq)
1176 {
1177         /* push_rt_task will return true if it moved an RT */
1178         while (push_rt_task(rq))
1179                 ;
1180 }
1181
1182 static int pull_rt_task(struct rq *this_rq)
1183 {
1184         int this_cpu = this_rq->cpu, ret = 0, cpu;
1185         struct task_struct *p, *next;
1186         struct rq *src_rq;
1187
1188         if (likely(!rt_overloaded(this_rq)))
1189                 return 0;
1190
1191         next = pick_next_task_rt(this_rq);
1192
1193         for_each_cpu(cpu, this_rq->rd->rto_mask) {
1194                 if (this_cpu == cpu)
1195                         continue;
1196
1197                 src_rq = cpu_rq(cpu);
1198                 /*
1199                  * We can potentially drop this_rq's lock in
1200                  * double_lock_balance, and another CPU could
1201                  * steal our next task - hence we must cause
1202                  * the caller to recalculate the next task
1203                  * in that case:
1204                  */
1205                 if (double_lock_balance(this_rq, src_rq)) {
1206                         struct task_struct *old_next = next;
1207
1208                         next = pick_next_task_rt(this_rq);
1209                         if (next != old_next)
1210                                 ret = 1;
1211                 }
1212
1213                 /*
1214                  * Are there still pullable RT tasks?
1215                  */
1216                 if (src_rq->rt.rt_nr_running <= 1)
1217                         goto skip;
1218
1219                 p = pick_next_highest_task_rt(src_rq, this_cpu);
1220
1221                 /*
1222                  * Do we have an RT task that preempts
1223                  * the to-be-scheduled task?
1224                  */
1225                 if (p && (!next || (p->prio < next->prio))) {
1226                         WARN_ON(p == src_rq->curr);
1227                         WARN_ON(!p->se.on_rq);
1228
1229                         /*
1230                          * There's a chance that p is higher in priority
1231                          * than what's currently running on its cpu.
1232                          * This is just that p is wakeing up and hasn't
1233                          * had a chance to schedule. We only pull
1234                          * p if it is lower in priority than the
1235                          * current task on the run queue or
1236                          * this_rq next task is lower in prio than
1237                          * the current task on that rq.
1238                          */
1239                         if (p->prio < src_rq->curr->prio ||
1240                             (next && next->prio < src_rq->curr->prio))
1241                                 goto skip;
1242
1243                         ret = 1;
1244
1245                         deactivate_task(src_rq, p, 0);
1246                         set_task_cpu(p, this_cpu);
1247                         activate_task(this_rq, p, 0);
1248                         /*
1249                          * We continue with the search, just in
1250                          * case there's an even higher prio task
1251                          * in another runqueue. (low likelyhood
1252                          * but possible)
1253                          *
1254                          * Update next so that we won't pick a task
1255                          * on another cpu with a priority lower (or equal)
1256                          * than the one we just picked.
1257                          */
1258                         next = p;
1259
1260                 }
1261  skip:
1262                 double_unlock_balance(this_rq, src_rq);
1263         }
1264
1265         return ret;
1266 }
1267
1268 static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
1269 {
1270         /* Try to pull RT tasks here if we lower this rq's prio */
1271         if (unlikely(rt_task(prev)) && rq->rt.highest_prio > prev->prio)
1272                 pull_rt_task(rq);
1273 }
1274
1275 static void post_schedule_rt(struct rq *rq)
1276 {
1277         /*
1278          * If we have more than one rt_task queued, then
1279          * see if we can push the other rt_tasks off to other CPUS.
1280          * Note we may release the rq lock, and since
1281          * the lock was owned by prev, we need to release it
1282          * first via finish_lock_switch and then reaquire it here.
1283          */
1284         if (unlikely(rq->rt.overloaded)) {
1285                 spin_lock_irq(&rq->lock);
1286                 push_rt_tasks(rq);
1287                 spin_unlock_irq(&rq->lock);
1288         }
1289 }
1290
1291 /*
1292  * If we are not running and we are not going to reschedule soon, we should
1293  * try to push tasks away now
1294  */
1295 static void task_wake_up_rt(struct rq *rq, struct task_struct *p)
1296 {
1297         if (!task_running(rq, p) &&
1298             !test_tsk_need_resched(rq->curr) &&
1299             rq->rt.overloaded)
1300                 push_rt_tasks(rq);
1301 }
1302
1303 static unsigned long
1304 load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
1305                 unsigned long max_load_move,
1306                 struct sched_domain *sd, enum cpu_idle_type idle,
1307                 int *all_pinned, int *this_best_prio)
1308 {
1309         /* don't touch RT tasks */
1310         return 0;
1311 }
1312
1313 static int
1314 move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
1315                  struct sched_domain *sd, enum cpu_idle_type idle)
1316 {
1317         /* don't touch RT tasks */
1318         return 0;
1319 }
1320
1321 static void set_cpus_allowed_rt(struct task_struct *p,
1322                                 const struct cpumask *new_mask)
1323 {
1324         int weight = cpumask_weight(new_mask);
1325
1326         BUG_ON(!rt_task(p));
1327
1328         /*
1329          * Update the migration status of the RQ if we have an RT task
1330          * which is running AND changing its weight value.
1331          */
1332         if (p->se.on_rq && (weight != p->rt.nr_cpus_allowed)) {
1333                 struct rq *rq = task_rq(p);
1334
1335                 if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
1336                         rq->rt.rt_nr_migratory++;
1337                 } else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
1338                         BUG_ON(!rq->rt.rt_nr_migratory);
1339                         rq->rt.rt_nr_migratory--;
1340                 }
1341
1342                 update_rt_migration(rq);
1343         }
1344
1345         cpumask_copy(&p->cpus_allowed, new_mask);
1346         p->rt.nr_cpus_allowed = weight;
1347 }
1348
1349 /* Assumes rq->lock is held */
1350 static void rq_online_rt(struct rq *rq)
1351 {
1352         if (rq->rt.overloaded)
1353                 rt_set_overload(rq);
1354
1355         __enable_runtime(rq);
1356
1357         cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio);
1358 }
1359
1360 /* Assumes rq->lock is held */
1361 static void rq_offline_rt(struct rq *rq)
1362 {
1363         if (rq->rt.overloaded)
1364                 rt_clear_overload(rq);
1365
1366         __disable_runtime(rq);
1367
1368         cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
1369 }
1370
1371 /*
1372  * When switch from the rt queue, we bring ourselves to a position
1373  * that we might want to pull RT tasks from other runqueues.
1374  */
1375 static void switched_from_rt(struct rq *rq, struct task_struct *p,
1376                            int running)
1377 {
1378         /*
1379          * If there are other RT tasks then we will reschedule
1380          * and the scheduling of the other RT tasks will handle
1381          * the balancing. But if we are the last RT task
1382          * we may need to handle the pulling of RT tasks
1383          * now.
1384          */
1385         if (!rq->rt.rt_nr_running)
1386                 pull_rt_task(rq);
1387 }
1388
1389 static inline void init_sched_rt_class(void)
1390 {
1391         unsigned int i;
1392
1393         for_each_possible_cpu(i)
1394                 alloc_cpumask_var_node(&per_cpu(local_cpu_mask, i),
1395                                         GFP_KERNEL, cpu_to_node(i));
1396 }
1397 #endif /* CONFIG_SMP */
1398
1399 /*
1400  * When switching a task to RT, we may overload the runqueue
1401  * with RT tasks. In this case we try to push them off to
1402  * other runqueues.
1403  */
1404 static void switched_to_rt(struct rq *rq, struct task_struct *p,
1405                            int running)
1406 {
1407         int check_resched = 1;
1408
1409         /*
1410          * If we are already running, then there's nothing
1411          * that needs to be done. But if we are not running
1412          * we may need to preempt the current running task.
1413          * If that current running task is also an RT task
1414          * then see if we can move to another run queue.
1415          */
1416         if (!running) {
1417 #ifdef CONFIG_SMP
1418                 if (rq->rt.overloaded && push_rt_task(rq) &&
1419                     /* Don't resched if we changed runqueues */
1420                     rq != task_rq(p))
1421                         check_resched = 0;
1422 #endif /* CONFIG_SMP */
1423                 if (check_resched && p->prio < rq->curr->prio)
1424                         resched_task(rq->curr);
1425         }
1426 }
1427
1428 /*
1429  * Priority of the task has changed. This may cause
1430  * us to initiate a push or pull.
1431  */
1432 static void prio_changed_rt(struct rq *rq, struct task_struct *p,
1433                             int oldprio, int running)
1434 {
1435         if (running) {
1436 #ifdef CONFIG_SMP
1437                 /*
1438                  * If our priority decreases while running, we
1439                  * may need to pull tasks to this runqueue.
1440                  */
1441                 if (oldprio < p->prio)
1442                         pull_rt_task(rq);
1443                 /*
1444                  * If there's a higher priority task waiting to run
1445                  * then reschedule. Note, the above pull_rt_task
1446                  * can release the rq lock and p could migrate.
1447                  * Only reschedule if p is still on the same runqueue.
1448                  */
1449                 if (p->prio > rq->rt.highest_prio && rq->curr == p)
1450                         resched_task(p);
1451 #else
1452                 /* For UP simply resched on drop of prio */
1453                 if (oldprio < p->prio)
1454                         resched_task(p);
1455 #endif /* CONFIG_SMP */
1456         } else {
1457                 /*
1458                  * This task is not running, but if it is
1459                  * greater than the current running task
1460                  * then reschedule.
1461                  */
1462                 if (p->prio < rq->curr->prio)
1463                         resched_task(rq->curr);
1464         }
1465 }
1466
1467 static void watchdog(struct rq *rq, struct task_struct *p)
1468 {
1469         unsigned long soft, hard;
1470
1471         if (!p->signal)
1472                 return;
1473
1474         soft = p->signal->rlim[RLIMIT_RTTIME].rlim_cur;
1475         hard = p->signal->rlim[RLIMIT_RTTIME].rlim_max;
1476
1477         if (soft != RLIM_INFINITY) {
1478                 unsigned long next;
1479
1480                 p->rt.timeout++;
1481                 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
1482                 if (p->rt.timeout > next)
1483                         p->cputime_expires.sched_exp = p->se.sum_exec_runtime;
1484         }
1485 }
1486
1487 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
1488 {
1489         update_curr_rt(rq);
1490
1491         watchdog(rq, p);
1492
1493         /*
1494          * RR tasks need a special form of timeslice management.
1495          * FIFO tasks have no timeslices.
1496          */
1497         if (p->policy != SCHED_RR)
1498                 return;
1499
1500         if (--p->rt.time_slice)
1501                 return;
1502
1503         p->rt.time_slice = DEF_TIMESLICE;
1504
1505         /*
1506          * Requeue to the end of queue if we are not the only element
1507          * on the queue:
1508          */
1509         if (p->rt.run_list.prev != p->rt.run_list.next) {
1510                 requeue_task_rt(rq, p, 0);
1511                 set_tsk_need_resched(p);
1512         }
1513 }
1514
1515 static void set_curr_task_rt(struct rq *rq)
1516 {
1517         struct task_struct *p = rq->curr;
1518
1519         p->se.exec_start = rq->clock;
1520 }
1521
1522 static const struct sched_class rt_sched_class = {
1523         .next                   = &fair_sched_class,
1524         .enqueue_task           = enqueue_task_rt,
1525         .dequeue_task           = dequeue_task_rt,
1526         .yield_task             = yield_task_rt,
1527
1528         .check_preempt_curr     = check_preempt_curr_rt,
1529
1530         .pick_next_task         = pick_next_task_rt,
1531         .put_prev_task          = put_prev_task_rt,
1532
1533 #ifdef CONFIG_SMP
1534         .select_task_rq         = select_task_rq_rt,
1535
1536         .load_balance           = load_balance_rt,
1537         .move_one_task          = move_one_task_rt,
1538         .set_cpus_allowed       = set_cpus_allowed_rt,
1539         .rq_online              = rq_online_rt,
1540         .rq_offline             = rq_offline_rt,
1541         .pre_schedule           = pre_schedule_rt,
1542         .post_schedule          = post_schedule_rt,
1543         .task_wake_up           = task_wake_up_rt,
1544         .switched_from          = switched_from_rt,
1545 #endif
1546
1547         .set_curr_task          = set_curr_task_rt,
1548         .task_tick              = task_tick_rt,
1549
1550         .prio_changed           = prio_changed_rt,
1551         .switched_to            = switched_to_rt,
1552 };
1553
1554 #ifdef CONFIG_SCHED_DEBUG
1555 extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq);
1556
1557 static void print_rt_stats(struct seq_file *m, int cpu)
1558 {
1559         struct rt_rq *rt_rq;
1560
1561         rcu_read_lock();
1562         for_each_leaf_rt_rq(rt_rq, cpu_rq(cpu))
1563                 print_rt_rq(m, cpu, rt_rq);
1564         rcu_read_unlock();
1565 }
1566 #endif /* CONFIG_SCHED_DEBUG */
1567