sched: use highest_prio.curr for pull threshold
[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(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 < 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.curr;
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 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
551
552 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu);
553
554 static inline int next_prio(struct rq *rq)
555 {
556         struct task_struct *next = pick_next_highest_task_rt(rq, rq->cpu);
557
558         if (next && rt_prio(next->prio))
559                 return next->prio;
560         else
561                 return MAX_RT_PRIO;
562 }
563 #endif
564
565 static inline
566 void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
567 {
568         int prio = rt_se_prio(rt_se);
569 #ifdef CONFIG_SMP
570         struct rq *rq = rq_of_rt_rq(rt_rq);
571 #endif
572
573         WARN_ON(!rt_prio(prio));
574         rt_rq->rt_nr_running++;
575 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
576         if (prio < rt_rq->highest_prio.curr) {
577
578                 /*
579                  * If the new task is higher in priority than anything on the
580                  * run-queue, we have a new high that must be published to
581                  * the world.  We also know that the previous high becomes
582                  * our next-highest.
583                  */
584                 rt_rq->highest_prio.next = rt_rq->highest_prio.curr;
585                 rt_rq->highest_prio.curr = prio;
586 #ifdef CONFIG_SMP
587                 if (rq->online)
588                         cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
589 #endif
590         } else if (prio == rt_rq->highest_prio.curr)
591                 /*
592                  * If the next task is equal in priority to the highest on
593                  * the run-queue, then we implicitly know that the next highest
594                  * task cannot be any lower than current
595                  */
596                 rt_rq->highest_prio.next = prio;
597         else if (prio < rt_rq->highest_prio.next)
598                 /*
599                  * Otherwise, we need to recompute next-highest
600                  */
601                 rt_rq->highest_prio.next = next_prio(rq);
602 #endif
603 #ifdef CONFIG_SMP
604         if (rt_se->nr_cpus_allowed > 1)
605                 rq->rt.rt_nr_migratory++;
606
607         update_rt_migration(rq);
608 #endif
609 #ifdef CONFIG_RT_GROUP_SCHED
610         if (rt_se_boosted(rt_se))
611                 rt_rq->rt_nr_boosted++;
612
613         if (rt_rq->tg)
614                 start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
615 #else
616         start_rt_bandwidth(&def_rt_bandwidth);
617 #endif
618 }
619
620 static inline
621 void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
622 {
623 #ifdef CONFIG_SMP
624         struct rq *rq = rq_of_rt_rq(rt_rq);
625         int highest_prio = rt_rq->highest_prio.curr;
626 #endif
627
628         WARN_ON(!rt_prio(rt_se_prio(rt_se)));
629         WARN_ON(!rt_rq->rt_nr_running);
630         rt_rq->rt_nr_running--;
631 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
632         if (rt_rq->rt_nr_running) {
633                 int prio = rt_se_prio(rt_se);
634
635                 WARN_ON(prio < rt_rq->highest_prio.curr);
636
637                 /*
638                  * This may have been our highest or next-highest priority
639                  * task and therefore we may have some recomputation to do
640                  */
641                 if (prio == rt_rq->highest_prio.curr) {
642                         struct rt_prio_array *array = &rt_rq->active;
643
644                         rt_rq->highest_prio.curr =
645                                 sched_find_first_bit(array->bitmap);
646                 }
647
648                 if (prio <= rt_rq->highest_prio.next)
649                         rt_rq->highest_prio.next = next_prio(rq);
650         } else
651                 rt_rq->highest_prio.curr = MAX_RT_PRIO;
652 #endif
653 #ifdef CONFIG_SMP
654         if (rt_se->nr_cpus_allowed > 1)
655                 rq->rt.rt_nr_migratory--;
656
657         if (rq->online && rt_rq->highest_prio.curr != highest_prio)
658                 cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
659
660         update_rt_migration(rq);
661 #endif /* CONFIG_SMP */
662 #ifdef CONFIG_RT_GROUP_SCHED
663         if (rt_se_boosted(rt_se))
664                 rt_rq->rt_nr_boosted--;
665
666         WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
667 #endif
668 }
669
670 static void __enqueue_rt_entity(struct sched_rt_entity *rt_se)
671 {
672         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
673         struct rt_prio_array *array = &rt_rq->active;
674         struct rt_rq *group_rq = group_rt_rq(rt_se);
675         struct list_head *queue = array->queue + rt_se_prio(rt_se);
676
677         /*
678          * Don't enqueue the group if its throttled, or when empty.
679          * The latter is a consequence of the former when a child group
680          * get throttled and the current group doesn't have any other
681          * active members.
682          */
683         if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
684                 return;
685
686         list_add_tail(&rt_se->run_list, queue);
687         __set_bit(rt_se_prio(rt_se), array->bitmap);
688
689         inc_rt_tasks(rt_se, rt_rq);
690 }
691
692 static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
693 {
694         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
695         struct rt_prio_array *array = &rt_rq->active;
696
697         list_del_init(&rt_se->run_list);
698         if (list_empty(array->queue + rt_se_prio(rt_se)))
699                 __clear_bit(rt_se_prio(rt_se), array->bitmap);
700
701         dec_rt_tasks(rt_se, rt_rq);
702 }
703
704 /*
705  * Because the prio of an upper entry depends on the lower
706  * entries, we must remove entries top - down.
707  */
708 static void dequeue_rt_stack(struct sched_rt_entity *rt_se)
709 {
710         struct sched_rt_entity *back = NULL;
711
712         for_each_sched_rt_entity(rt_se) {
713                 rt_se->back = back;
714                 back = rt_se;
715         }
716
717         for (rt_se = back; rt_se; rt_se = rt_se->back) {
718                 if (on_rt_rq(rt_se))
719                         __dequeue_rt_entity(rt_se);
720         }
721 }
722
723 static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
724 {
725         dequeue_rt_stack(rt_se);
726         for_each_sched_rt_entity(rt_se)
727                 __enqueue_rt_entity(rt_se);
728 }
729
730 static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
731 {
732         dequeue_rt_stack(rt_se);
733
734         for_each_sched_rt_entity(rt_se) {
735                 struct rt_rq *rt_rq = group_rt_rq(rt_se);
736
737                 if (rt_rq && rt_rq->rt_nr_running)
738                         __enqueue_rt_entity(rt_se);
739         }
740 }
741
742 /*
743  * Adding/removing a task to/from a priority array:
744  */
745 static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
746 {
747         struct sched_rt_entity *rt_se = &p->rt;
748
749         if (wakeup)
750                 rt_se->timeout = 0;
751
752         enqueue_rt_entity(rt_se);
753
754         inc_cpu_load(rq, p->se.load.weight);
755 }
756
757 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
758 {
759         struct sched_rt_entity *rt_se = &p->rt;
760
761         update_curr_rt(rq);
762         dequeue_rt_entity(rt_se);
763
764         dec_cpu_load(rq, p->se.load.weight);
765 }
766
767 /*
768  * Put task to the end of the run list without the overhead of dequeue
769  * followed by enqueue.
770  */
771 static void
772 requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
773 {
774         if (on_rt_rq(rt_se)) {
775                 struct rt_prio_array *array = &rt_rq->active;
776                 struct list_head *queue = array->queue + rt_se_prio(rt_se);
777
778                 if (head)
779                         list_move(&rt_se->run_list, queue);
780                 else
781                         list_move_tail(&rt_se->run_list, queue);
782         }
783 }
784
785 static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
786 {
787         struct sched_rt_entity *rt_se = &p->rt;
788         struct rt_rq *rt_rq;
789
790         for_each_sched_rt_entity(rt_se) {
791                 rt_rq = rt_rq_of_se(rt_se);
792                 requeue_rt_entity(rt_rq, rt_se, head);
793         }
794 }
795
796 static void yield_task_rt(struct rq *rq)
797 {
798         requeue_task_rt(rq, rq->curr, 0);
799 }
800
801 #ifdef CONFIG_SMP
802 static int find_lowest_rq(struct task_struct *task);
803
804 static int select_task_rq_rt(struct task_struct *p, int sync)
805 {
806         struct rq *rq = task_rq(p);
807
808         /*
809          * If the current task is an RT task, then
810          * try to see if we can wake this RT task up on another
811          * runqueue. Otherwise simply start this RT task
812          * on its current runqueue.
813          *
814          * We want to avoid overloading runqueues. Even if
815          * the RT task is of higher priority than the current RT task.
816          * RT tasks behave differently than other tasks. If
817          * one gets preempted, we try to push it off to another queue.
818          * So trying to keep a preempting RT task on the same
819          * cache hot CPU will force the running RT task to
820          * a cold CPU. So we waste all the cache for the lower
821          * RT task in hopes of saving some of a RT task
822          * that is just being woken and probably will have
823          * cold cache anyway.
824          */
825         if (unlikely(rt_task(rq->curr)) &&
826             (p->rt.nr_cpus_allowed > 1)) {
827                 int cpu = find_lowest_rq(p);
828
829                 return (cpu == -1) ? task_cpu(p) : cpu;
830         }
831
832         /*
833          * Otherwise, just let it ride on the affined RQ and the
834          * post-schedule router will push the preempted task away
835          */
836         return task_cpu(p);
837 }
838
839 static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
840 {
841         cpumask_var_t mask;
842
843         if (rq->curr->rt.nr_cpus_allowed == 1)
844                 return;
845
846         if (!alloc_cpumask_var(&mask, GFP_ATOMIC))
847                 return;
848
849         if (p->rt.nr_cpus_allowed != 1
850             && cpupri_find(&rq->rd->cpupri, p, mask))
851                 goto free;
852
853         if (!cpupri_find(&rq->rd->cpupri, rq->curr, mask))
854                 goto free;
855
856         /*
857          * There appears to be other cpus that can accept
858          * current and none to run 'p', so lets reschedule
859          * to try and push current away:
860          */
861         requeue_task_rt(rq, p, 1);
862         resched_task(rq->curr);
863 free:
864         free_cpumask_var(mask);
865 }
866
867 #endif /* CONFIG_SMP */
868
869 /*
870  * Preempt the current task with a newly woken task if needed:
871  */
872 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int sync)
873 {
874         if (p->prio < rq->curr->prio) {
875                 resched_task(rq->curr);
876                 return;
877         }
878
879 #ifdef CONFIG_SMP
880         /*
881          * If:
882          *
883          * - the newly woken task is of equal priority to the current task
884          * - the newly woken task is non-migratable while current is migratable
885          * - current will be preempted on the next reschedule
886          *
887          * we should check to see if current can readily move to a different
888          * cpu.  If so, we will reschedule to allow the push logic to try
889          * to move current somewhere else, making room for our non-migratable
890          * task.
891          */
892         if (p->prio == rq->curr->prio && !need_resched())
893                 check_preempt_equal_prio(rq, p);
894 #endif
895 }
896
897 static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
898                                                    struct rt_rq *rt_rq)
899 {
900         struct rt_prio_array *array = &rt_rq->active;
901         struct sched_rt_entity *next = NULL;
902         struct list_head *queue;
903         int idx;
904
905         idx = sched_find_first_bit(array->bitmap);
906         BUG_ON(idx >= MAX_RT_PRIO);
907
908         queue = array->queue + idx;
909         next = list_entry(queue->next, struct sched_rt_entity, run_list);
910
911         return next;
912 }
913
914 static struct task_struct *pick_next_task_rt(struct rq *rq)
915 {
916         struct sched_rt_entity *rt_se;
917         struct task_struct *p;
918         struct rt_rq *rt_rq;
919
920         rt_rq = &rq->rt;
921
922         if (unlikely(!rt_rq->rt_nr_running))
923                 return NULL;
924
925         if (rt_rq_throttled(rt_rq))
926                 return NULL;
927
928         do {
929                 rt_se = pick_next_rt_entity(rq, rt_rq);
930                 BUG_ON(!rt_se);
931                 rt_rq = group_rt_rq(rt_se);
932         } while (rt_rq);
933
934         p = rt_task_of(rt_se);
935         p->se.exec_start = rq->clock;
936         return p;
937 }
938
939 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
940 {
941         update_curr_rt(rq);
942         p->se.exec_start = 0;
943 }
944
945 #ifdef CONFIG_SMP
946
947 /* Only try algorithms three times */
948 #define RT_MAX_TRIES 3
949
950 static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
951
952 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
953 {
954         if (!task_running(rq, p) &&
955             (cpu < 0 || cpumask_test_cpu(cpu, &p->cpus_allowed)) &&
956             (p->rt.nr_cpus_allowed > 1))
957                 return 1;
958         return 0;
959 }
960
961 /* Return the second highest RT task, NULL otherwise */
962 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
963 {
964         struct task_struct *next = NULL;
965         struct sched_rt_entity *rt_se;
966         struct rt_prio_array *array;
967         struct rt_rq *rt_rq;
968         int idx;
969
970         for_each_leaf_rt_rq(rt_rq, rq) {
971                 array = &rt_rq->active;
972                 idx = sched_find_first_bit(array->bitmap);
973  next_idx:
974                 if (idx >= MAX_RT_PRIO)
975                         continue;
976                 if (next && next->prio < idx)
977                         continue;
978                 list_for_each_entry(rt_se, array->queue + idx, run_list) {
979                         struct task_struct *p = rt_task_of(rt_se);
980                         if (pick_rt_task(rq, p, cpu)) {
981                                 next = p;
982                                 break;
983                         }
984                 }
985                 if (!next) {
986                         idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
987                         goto next_idx;
988                 }
989         }
990
991         return next;
992 }
993
994 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
995
996 static inline int pick_optimal_cpu(int this_cpu, cpumask_t *mask)
997 {
998         int first;
999
1000         /* "this_cpu" is cheaper to preempt than a remote processor */
1001         if ((this_cpu != -1) && cpu_isset(this_cpu, *mask))
1002                 return this_cpu;
1003
1004         first = first_cpu(*mask);
1005         if (first != NR_CPUS)
1006                 return first;
1007
1008         return -1;
1009 }
1010
1011 static int find_lowest_rq(struct task_struct *task)
1012 {
1013         struct sched_domain *sd;
1014         struct cpumask *lowest_mask = __get_cpu_var(local_cpu_mask);
1015         int this_cpu = smp_processor_id();
1016         int cpu      = task_cpu(task);
1017
1018         if (task->rt.nr_cpus_allowed == 1)
1019                 return -1; /* No other targets possible */
1020
1021         if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
1022                 return -1; /* No targets found */
1023
1024         /*
1025          * Only consider CPUs that are usable for migration.
1026          * I guess we might want to change cpupri_find() to ignore those
1027          * in the first place.
1028          */
1029         cpumask_and(lowest_mask, lowest_mask, cpu_active_mask);
1030
1031         /*
1032          * At this point we have built a mask of cpus representing the
1033          * lowest priority tasks in the system.  Now we want to elect
1034          * the best one based on our affinity and topology.
1035          *
1036          * We prioritize the last cpu that the task executed on since
1037          * it is most likely cache-hot in that location.
1038          */
1039         if (cpumask_test_cpu(cpu, lowest_mask))
1040                 return cpu;
1041
1042         /*
1043          * Otherwise, we consult the sched_domains span maps to figure
1044          * out which cpu is logically closest to our hot cache data.
1045          */
1046         if (this_cpu == cpu)
1047                 this_cpu = -1; /* Skip this_cpu opt if the same */
1048
1049         for_each_domain(cpu, sd) {
1050                 if (sd->flags & SD_WAKE_AFFINE) {
1051                         cpumask_t domain_mask;
1052                         int       best_cpu;
1053
1054                         cpumask_and(&domain_mask, sched_domain_span(sd),
1055                                     lowest_mask);
1056
1057                         best_cpu = pick_optimal_cpu(this_cpu,
1058                                                     &domain_mask);
1059                         if (best_cpu != -1)
1060                                 return best_cpu;
1061                 }
1062         }
1063
1064         /*
1065          * And finally, if there were no matches within the domains
1066          * just give the caller *something* to work with from the compatible
1067          * locations.
1068          */
1069         return pick_optimal_cpu(this_cpu, lowest_mask);
1070 }
1071
1072 /* Will lock the rq it finds */
1073 static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1074 {
1075         struct rq *lowest_rq = NULL;
1076         int tries;
1077         int cpu;
1078
1079         for (tries = 0; tries < RT_MAX_TRIES; tries++) {
1080                 cpu = find_lowest_rq(task);
1081
1082                 if ((cpu == -1) || (cpu == rq->cpu))
1083                         break;
1084
1085                 lowest_rq = cpu_rq(cpu);
1086
1087                 /* if the prio of this runqueue changed, try again */
1088                 if (double_lock_balance(rq, lowest_rq)) {
1089                         /*
1090                          * We had to unlock the run queue. In
1091                          * the mean time, task could have
1092                          * migrated already or had its affinity changed.
1093                          * Also make sure that it wasn't scheduled on its rq.
1094                          */
1095                         if (unlikely(task_rq(task) != rq ||
1096                                      !cpumask_test_cpu(lowest_rq->cpu,
1097                                                        &task->cpus_allowed) ||
1098                                      task_running(rq, task) ||
1099                                      !task->se.on_rq)) {
1100
1101                                 spin_unlock(&lowest_rq->lock);
1102                                 lowest_rq = NULL;
1103                                 break;
1104                         }
1105                 }
1106
1107                 /* If this rq is still suitable use it. */
1108                 if (lowest_rq->rt.highest_prio.curr > task->prio)
1109                         break;
1110
1111                 /* try again */
1112                 double_unlock_balance(rq, lowest_rq);
1113                 lowest_rq = NULL;
1114         }
1115
1116         return lowest_rq;
1117 }
1118
1119 /*
1120  * If the current CPU has more than one RT task, see if the non
1121  * running task can migrate over to a CPU that is running a task
1122  * of lesser priority.
1123  */
1124 static int push_rt_task(struct rq *rq)
1125 {
1126         struct task_struct *next_task;
1127         struct rq *lowest_rq;
1128         int ret = 0;
1129         int paranoid = RT_MAX_TRIES;
1130
1131         if (!rq->rt.overloaded)
1132                 return 0;
1133
1134         next_task = pick_next_highest_task_rt(rq, -1);
1135         if (!next_task)
1136                 return 0;
1137
1138  retry:
1139         if (unlikely(next_task == rq->curr)) {
1140                 WARN_ON(1);
1141                 return 0;
1142         }
1143
1144         /*
1145          * It's possible that the next_task slipped in of
1146          * higher priority than current. If that's the case
1147          * just reschedule current.
1148          */
1149         if (unlikely(next_task->prio < rq->curr->prio)) {
1150                 resched_task(rq->curr);
1151                 return 0;
1152         }
1153
1154         /* We might release rq lock */
1155         get_task_struct(next_task);
1156
1157         /* find_lock_lowest_rq locks the rq if found */
1158         lowest_rq = find_lock_lowest_rq(next_task, rq);
1159         if (!lowest_rq) {
1160                 struct task_struct *task;
1161                 /*
1162                  * find lock_lowest_rq releases rq->lock
1163                  * so it is possible that next_task has changed.
1164                  * If it has, then try again.
1165                  */
1166                 task = pick_next_highest_task_rt(rq, -1);
1167                 if (unlikely(task != next_task) && task && paranoid--) {
1168                         put_task_struct(next_task);
1169                         next_task = task;
1170                         goto retry;
1171                 }
1172                 goto out;
1173         }
1174
1175         deactivate_task(rq, next_task, 0);
1176         set_task_cpu(next_task, lowest_rq->cpu);
1177         activate_task(lowest_rq, next_task, 0);
1178
1179         resched_task(lowest_rq->curr);
1180
1181         double_unlock_balance(rq, lowest_rq);
1182
1183         ret = 1;
1184 out:
1185         put_task_struct(next_task);
1186
1187         return ret;
1188 }
1189
1190 /*
1191  * TODO: Currently we just use the second highest prio task on
1192  *       the queue, and stop when it can't migrate (or there's
1193  *       no more RT tasks).  There may be a case where a lower
1194  *       priority RT task has a different affinity than the
1195  *       higher RT task. In this case the lower RT task could
1196  *       possibly be able to migrate where as the higher priority
1197  *       RT task could not.  We currently ignore this issue.
1198  *       Enhancements are welcome!
1199  */
1200 static void push_rt_tasks(struct rq *rq)
1201 {
1202         /* push_rt_task will return true if it moved an RT */
1203         while (push_rt_task(rq))
1204                 ;
1205 }
1206
1207 static int pull_rt_task(struct rq *this_rq)
1208 {
1209         int this_cpu = this_rq->cpu, ret = 0, cpu;
1210         struct task_struct *p;
1211         struct rq *src_rq;
1212
1213         if (likely(!rt_overloaded(this_rq)))
1214                 return 0;
1215
1216         for_each_cpu(cpu, this_rq->rd->rto_mask) {
1217                 if (this_cpu == cpu)
1218                         continue;
1219
1220                 src_rq = cpu_rq(cpu);
1221                 /*
1222                  * We can potentially drop this_rq's lock in
1223                  * double_lock_balance, and another CPU could
1224                  * alter this_rq
1225                  */
1226                 double_lock_balance(this_rq, src_rq);
1227
1228                 /*
1229                  * Are there still pullable RT tasks?
1230                  */
1231                 if (src_rq->rt.rt_nr_running <= 1)
1232                         goto skip;
1233
1234                 p = pick_next_highest_task_rt(src_rq, this_cpu);
1235
1236                 /*
1237                  * Do we have an RT task that preempts
1238                  * the to-be-scheduled task?
1239                  */
1240                 if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
1241                         WARN_ON(p == src_rq->curr);
1242                         WARN_ON(!p->se.on_rq);
1243
1244                         /*
1245                          * There's a chance that p is higher in priority
1246                          * than what's currently running on its cpu.
1247                          * This is just that p is wakeing up and hasn't
1248                          * had a chance to schedule. We only pull
1249                          * p if it is lower in priority than the
1250                          * current task on the run queue
1251                          */
1252                         if (p->prio < src_rq->curr->prio)
1253                                 goto skip;
1254
1255                         ret = 1;
1256
1257                         deactivate_task(src_rq, p, 0);
1258                         set_task_cpu(p, this_cpu);
1259                         activate_task(this_rq, p, 0);
1260                         /*
1261                          * We continue with the search, just in
1262                          * case there's an even higher prio task
1263                          * in another runqueue. (low likelyhood
1264                          * but possible)
1265                          */
1266                 }
1267  skip:
1268                 double_unlock_balance(this_rq, src_rq);
1269         }
1270
1271         return ret;
1272 }
1273
1274 static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
1275 {
1276         /* Try to pull RT tasks here if we lower this rq's prio */
1277         if (unlikely(rt_task(prev)) && rq->rt.highest_prio.curr > prev->prio)
1278                 pull_rt_task(rq);
1279 }
1280
1281 static void post_schedule_rt(struct rq *rq)
1282 {
1283         /*
1284          * If we have more than one rt_task queued, then
1285          * see if we can push the other rt_tasks off to other CPUS.
1286          * Note we may release the rq lock, and since
1287          * the lock was owned by prev, we need to release it
1288          * first via finish_lock_switch and then reaquire it here.
1289          */
1290         if (unlikely(rq->rt.overloaded)) {
1291                 spin_lock_irq(&rq->lock);
1292                 push_rt_tasks(rq);
1293                 spin_unlock_irq(&rq->lock);
1294         }
1295 }
1296
1297 /*
1298  * If we are not running and we are not going to reschedule soon, we should
1299  * try to push tasks away now
1300  */
1301 static void task_wake_up_rt(struct rq *rq, struct task_struct *p)
1302 {
1303         if (!task_running(rq, p) &&
1304             !test_tsk_need_resched(rq->curr) &&
1305             rq->rt.overloaded)
1306                 push_rt_tasks(rq);
1307 }
1308
1309 static unsigned long
1310 load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
1311                 unsigned long max_load_move,
1312                 struct sched_domain *sd, enum cpu_idle_type idle,
1313                 int *all_pinned, int *this_best_prio)
1314 {
1315         /* don't touch RT tasks */
1316         return 0;
1317 }
1318
1319 static int
1320 move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
1321                  struct sched_domain *sd, enum cpu_idle_type idle)
1322 {
1323         /* don't touch RT tasks */
1324         return 0;
1325 }
1326
1327 static void set_cpus_allowed_rt(struct task_struct *p,
1328                                 const struct cpumask *new_mask)
1329 {
1330         int weight = cpumask_weight(new_mask);
1331
1332         BUG_ON(!rt_task(p));
1333
1334         /*
1335          * Update the migration status of the RQ if we have an RT task
1336          * which is running AND changing its weight value.
1337          */
1338         if (p->se.on_rq && (weight != p->rt.nr_cpus_allowed)) {
1339                 struct rq *rq = task_rq(p);
1340
1341                 if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
1342                         rq->rt.rt_nr_migratory++;
1343                 } else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
1344                         BUG_ON(!rq->rt.rt_nr_migratory);
1345                         rq->rt.rt_nr_migratory--;
1346                 }
1347
1348                 update_rt_migration(rq);
1349         }
1350
1351         cpumask_copy(&p->cpus_allowed, new_mask);
1352         p->rt.nr_cpus_allowed = weight;
1353 }
1354
1355 /* Assumes rq->lock is held */
1356 static void rq_online_rt(struct rq *rq)
1357 {
1358         if (rq->rt.overloaded)
1359                 rt_set_overload(rq);
1360
1361         __enable_runtime(rq);
1362
1363         cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
1364 }
1365
1366 /* Assumes rq->lock is held */
1367 static void rq_offline_rt(struct rq *rq)
1368 {
1369         if (rq->rt.overloaded)
1370                 rt_clear_overload(rq);
1371
1372         __disable_runtime(rq);
1373
1374         cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
1375 }
1376
1377 /*
1378  * When switch from the rt queue, we bring ourselves to a position
1379  * that we might want to pull RT tasks from other runqueues.
1380  */
1381 static void switched_from_rt(struct rq *rq, struct task_struct *p,
1382                            int running)
1383 {
1384         /*
1385          * If there are other RT tasks then we will reschedule
1386          * and the scheduling of the other RT tasks will handle
1387          * the balancing. But if we are the last RT task
1388          * we may need to handle the pulling of RT tasks
1389          * now.
1390          */
1391         if (!rq->rt.rt_nr_running)
1392                 pull_rt_task(rq);
1393 }
1394
1395 static inline void init_sched_rt_class(void)
1396 {
1397         unsigned int i;
1398
1399         for_each_possible_cpu(i)
1400                 alloc_cpumask_var(&per_cpu(local_cpu_mask, i), GFP_KERNEL);
1401 }
1402 #endif /* CONFIG_SMP */
1403
1404 /*
1405  * When switching a task to RT, we may overload the runqueue
1406  * with RT tasks. In this case we try to push them off to
1407  * other runqueues.
1408  */
1409 static void switched_to_rt(struct rq *rq, struct task_struct *p,
1410                            int running)
1411 {
1412         int check_resched = 1;
1413
1414         /*
1415          * If we are already running, then there's nothing
1416          * that needs to be done. But if we are not running
1417          * we may need to preempt the current running task.
1418          * If that current running task is also an RT task
1419          * then see if we can move to another run queue.
1420          */
1421         if (!running) {
1422 #ifdef CONFIG_SMP
1423                 if (rq->rt.overloaded && push_rt_task(rq) &&
1424                     /* Don't resched if we changed runqueues */
1425                     rq != task_rq(p))
1426                         check_resched = 0;
1427 #endif /* CONFIG_SMP */
1428                 if (check_resched && p->prio < rq->curr->prio)
1429                         resched_task(rq->curr);
1430         }
1431 }
1432
1433 /*
1434  * Priority of the task has changed. This may cause
1435  * us to initiate a push or pull.
1436  */
1437 static void prio_changed_rt(struct rq *rq, struct task_struct *p,
1438                             int oldprio, int running)
1439 {
1440         if (running) {
1441 #ifdef CONFIG_SMP
1442                 /*
1443                  * If our priority decreases while running, we
1444                  * may need to pull tasks to this runqueue.
1445                  */
1446                 if (oldprio < p->prio)
1447                         pull_rt_task(rq);
1448                 /*
1449                  * If there's a higher priority task waiting to run
1450                  * then reschedule. Note, the above pull_rt_task
1451                  * can release the rq lock and p could migrate.
1452                  * Only reschedule if p is still on the same runqueue.
1453                  */
1454                 if (p->prio > rq->rt.highest_prio.curr && rq->curr == p)
1455                         resched_task(p);
1456 #else
1457                 /* For UP simply resched on drop of prio */
1458                 if (oldprio < p->prio)
1459                         resched_task(p);
1460 #endif /* CONFIG_SMP */
1461         } else {
1462                 /*
1463                  * This task is not running, but if it is
1464                  * greater than the current running task
1465                  * then reschedule.
1466                  */
1467                 if (p->prio < rq->curr->prio)
1468                         resched_task(rq->curr);
1469         }
1470 }
1471
1472 static void watchdog(struct rq *rq, struct task_struct *p)
1473 {
1474         unsigned long soft, hard;
1475
1476         if (!p->signal)
1477                 return;
1478
1479         soft = p->signal->rlim[RLIMIT_RTTIME].rlim_cur;
1480         hard = p->signal->rlim[RLIMIT_RTTIME].rlim_max;
1481
1482         if (soft != RLIM_INFINITY) {
1483                 unsigned long next;
1484
1485                 p->rt.timeout++;
1486                 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
1487                 if (p->rt.timeout > next)
1488                         p->cputime_expires.sched_exp = p->se.sum_exec_runtime;
1489         }
1490 }
1491
1492 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
1493 {
1494         update_curr_rt(rq);
1495
1496         watchdog(rq, p);
1497
1498         /*
1499          * RR tasks need a special form of timeslice management.
1500          * FIFO tasks have no timeslices.
1501          */
1502         if (p->policy != SCHED_RR)
1503                 return;
1504
1505         if (--p->rt.time_slice)
1506                 return;
1507
1508         p->rt.time_slice = DEF_TIMESLICE;
1509
1510         /*
1511          * Requeue to the end of queue if we are not the only element
1512          * on the queue:
1513          */
1514         if (p->rt.run_list.prev != p->rt.run_list.next) {
1515                 requeue_task_rt(rq, p, 0);
1516                 set_tsk_need_resched(p);
1517         }
1518 }
1519
1520 static void set_curr_task_rt(struct rq *rq)
1521 {
1522         struct task_struct *p = rq->curr;
1523
1524         p->se.exec_start = rq->clock;
1525 }
1526
1527 static const struct sched_class rt_sched_class = {
1528         .next                   = &fair_sched_class,
1529         .enqueue_task           = enqueue_task_rt,
1530         .dequeue_task           = dequeue_task_rt,
1531         .yield_task             = yield_task_rt,
1532
1533         .check_preempt_curr     = check_preempt_curr_rt,
1534
1535         .pick_next_task         = pick_next_task_rt,
1536         .put_prev_task          = put_prev_task_rt,
1537
1538 #ifdef CONFIG_SMP
1539         .select_task_rq         = select_task_rq_rt,
1540
1541         .load_balance           = load_balance_rt,
1542         .move_one_task          = move_one_task_rt,
1543         .set_cpus_allowed       = set_cpus_allowed_rt,
1544         .rq_online              = rq_online_rt,
1545         .rq_offline             = rq_offline_rt,
1546         .pre_schedule           = pre_schedule_rt,
1547         .post_schedule          = post_schedule_rt,
1548         .task_wake_up           = task_wake_up_rt,
1549         .switched_from          = switched_from_rt,
1550 #endif
1551
1552         .set_curr_task          = set_curr_task_rt,
1553         .task_tick              = task_tick_rt,
1554
1555         .prio_changed           = prio_changed_rt,
1556         .switched_to            = switched_to_rt,
1557 };
1558
1559 #ifdef CONFIG_SCHED_DEBUG
1560 extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq);
1561
1562 static void print_rt_stats(struct seq_file *m, int cpu)
1563 {
1564         struct rt_rq *rt_rq;
1565
1566         rcu_read_lock();
1567         for_each_leaf_rt_rq(rt_rq, cpu_rq(cpu))
1568                 print_rt_rq(m, cpu, rt_rq);
1569         rcu_read_unlock();
1570 }
1571 #endif /* CONFIG_SCHED_DEBUG */
1572