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Commit | Line | Data |
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bb44e5d1 IM |
1 | /* |
2 | * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR | |
3 | * policies) | |
4 | */ | |
5 | ||
4fd29176 | 6 | #ifdef CONFIG_SMP |
84de4274 | 7 | |
637f5085 | 8 | static inline int rt_overloaded(struct rq *rq) |
4fd29176 | 9 | { |
637f5085 | 10 | return atomic_read(&rq->rd->rto_count); |
4fd29176 | 11 | } |
84de4274 | 12 | |
4fd29176 SR |
13 | static inline void rt_set_overload(struct rq *rq) |
14 | { | |
637f5085 | 15 | cpu_set(rq->cpu, rq->rd->rto_mask); |
4fd29176 SR |
16 | /* |
17 | * Make sure the mask is visible before we set | |
18 | * the overload count. That is checked to determine | |
19 | * if we should look at the mask. It would be a shame | |
20 | * if we looked at the mask, but the mask was not | |
21 | * updated yet. | |
22 | */ | |
23 | wmb(); | |
637f5085 | 24 | atomic_inc(&rq->rd->rto_count); |
4fd29176 | 25 | } |
84de4274 | 26 | |
4fd29176 SR |
27 | static inline void rt_clear_overload(struct rq *rq) |
28 | { | |
29 | /* the order here really doesn't matter */ | |
637f5085 GH |
30 | atomic_dec(&rq->rd->rto_count); |
31 | cpu_clear(rq->cpu, rq->rd->rto_mask); | |
4fd29176 | 32 | } |
73fe6aae GH |
33 | |
34 | static void update_rt_migration(struct rq *rq) | |
35 | { | |
637f5085 | 36 | if (rq->rt.rt_nr_migratory && (rq->rt.rt_nr_running > 1)) { |
cdc8eb98 GH |
37 | if (!rq->rt.overloaded) { |
38 | rt_set_overload(rq); | |
39 | rq->rt.overloaded = 1; | |
40 | } | |
41 | } else if (rq->rt.overloaded) { | |
73fe6aae | 42 | rt_clear_overload(rq); |
637f5085 GH |
43 | rq->rt.overloaded = 0; |
44 | } | |
73fe6aae | 45 | } |
4fd29176 SR |
46 | #endif /* CONFIG_SMP */ |
47 | ||
bb44e5d1 IM |
48 | /* |
49 | * Update the current task's runtime statistics. Skip current tasks that | |
50 | * are not in our scheduling class. | |
51 | */ | |
a9957449 | 52 | static void update_curr_rt(struct rq *rq) |
bb44e5d1 IM |
53 | { |
54 | struct task_struct *curr = rq->curr; | |
55 | u64 delta_exec; | |
56 | ||
57 | if (!task_has_rt_policy(curr)) | |
58 | return; | |
59 | ||
d281918d | 60 | delta_exec = rq->clock - curr->se.exec_start; |
bb44e5d1 IM |
61 | if (unlikely((s64)delta_exec < 0)) |
62 | delta_exec = 0; | |
6cfb0d5d IM |
63 | |
64 | schedstat_set(curr->se.exec_max, max(curr->se.exec_max, delta_exec)); | |
bb44e5d1 IM |
65 | |
66 | curr->se.sum_exec_runtime += delta_exec; | |
d281918d | 67 | curr->se.exec_start = rq->clock; |
d842de87 | 68 | cpuacct_charge(curr, delta_exec); |
bb44e5d1 IM |
69 | } |
70 | ||
63489e45 SR |
71 | static inline void inc_rt_tasks(struct task_struct *p, struct rq *rq) |
72 | { | |
73 | WARN_ON(!rt_task(p)); | |
74 | rq->rt.rt_nr_running++; | |
764a9d6f SR |
75 | #ifdef CONFIG_SMP |
76 | if (p->prio < rq->rt.highest_prio) | |
77 | rq->rt.highest_prio = p->prio; | |
73fe6aae GH |
78 | if (p->nr_cpus_allowed > 1) |
79 | rq->rt.rt_nr_migratory++; | |
80 | ||
81 | update_rt_migration(rq); | |
764a9d6f | 82 | #endif /* CONFIG_SMP */ |
63489e45 SR |
83 | } |
84 | ||
85 | static inline void dec_rt_tasks(struct task_struct *p, struct rq *rq) | |
86 | { | |
87 | WARN_ON(!rt_task(p)); | |
88 | WARN_ON(!rq->rt.rt_nr_running); | |
89 | rq->rt.rt_nr_running--; | |
764a9d6f SR |
90 | #ifdef CONFIG_SMP |
91 | if (rq->rt.rt_nr_running) { | |
92 | struct rt_prio_array *array; | |
93 | ||
94 | WARN_ON(p->prio < rq->rt.highest_prio); | |
95 | if (p->prio == rq->rt.highest_prio) { | |
96 | /* recalculate */ | |
97 | array = &rq->rt.active; | |
98 | rq->rt.highest_prio = | |
99 | sched_find_first_bit(array->bitmap); | |
100 | } /* otherwise leave rq->highest prio alone */ | |
101 | } else | |
102 | rq->rt.highest_prio = MAX_RT_PRIO; | |
73fe6aae GH |
103 | if (p->nr_cpus_allowed > 1) |
104 | rq->rt.rt_nr_migratory--; | |
105 | ||
106 | update_rt_migration(rq); | |
764a9d6f | 107 | #endif /* CONFIG_SMP */ |
63489e45 SR |
108 | } |
109 | ||
fd390f6a | 110 | static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup) |
bb44e5d1 IM |
111 | { |
112 | struct rt_prio_array *array = &rq->rt.active; | |
113 | ||
fa717060 | 114 | list_add_tail(&p->rt.run_list, array->queue + p->prio); |
bb44e5d1 | 115 | __set_bit(p->prio, array->bitmap); |
58e2d4ca | 116 | inc_cpu_load(rq, p->se.load.weight); |
63489e45 SR |
117 | |
118 | inc_rt_tasks(p, rq); | |
78f2c7db PZ |
119 | |
120 | if (wakeup) | |
121 | p->rt.timeout = 0; | |
bb44e5d1 IM |
122 | } |
123 | ||
124 | /* | |
125 | * Adding/removing a task to/from a priority array: | |
126 | */ | |
f02231e5 | 127 | static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep) |
bb44e5d1 IM |
128 | { |
129 | struct rt_prio_array *array = &rq->rt.active; | |
130 | ||
f1e14ef6 | 131 | update_curr_rt(rq); |
bb44e5d1 | 132 | |
fa717060 | 133 | list_del(&p->rt.run_list); |
bb44e5d1 IM |
134 | if (list_empty(array->queue + p->prio)) |
135 | __clear_bit(p->prio, array->bitmap); | |
58e2d4ca | 136 | dec_cpu_load(rq, p->se.load.weight); |
63489e45 SR |
137 | |
138 | dec_rt_tasks(p, rq); | |
bb44e5d1 IM |
139 | } |
140 | ||
141 | /* | |
142 | * Put task to the end of the run list without the overhead of dequeue | |
143 | * followed by enqueue. | |
144 | */ | |
145 | static void requeue_task_rt(struct rq *rq, struct task_struct *p) | |
146 | { | |
147 | struct rt_prio_array *array = &rq->rt.active; | |
148 | ||
fa717060 | 149 | list_move_tail(&p->rt.run_list, array->queue + p->prio); |
bb44e5d1 IM |
150 | } |
151 | ||
152 | static void | |
4530d7ab | 153 | yield_task_rt(struct rq *rq) |
bb44e5d1 | 154 | { |
4530d7ab | 155 | requeue_task_rt(rq, rq->curr); |
bb44e5d1 IM |
156 | } |
157 | ||
e7693a36 | 158 | #ifdef CONFIG_SMP |
318e0893 GH |
159 | static int find_lowest_rq(struct task_struct *task); |
160 | ||
e7693a36 GH |
161 | static int select_task_rq_rt(struct task_struct *p, int sync) |
162 | { | |
318e0893 GH |
163 | struct rq *rq = task_rq(p); |
164 | ||
165 | /* | |
e1f47d89 SR |
166 | * If the current task is an RT task, then |
167 | * try to see if we can wake this RT task up on another | |
168 | * runqueue. Otherwise simply start this RT task | |
169 | * on its current runqueue. | |
170 | * | |
171 | * We want to avoid overloading runqueues. Even if | |
172 | * the RT task is of higher priority than the current RT task. | |
173 | * RT tasks behave differently than other tasks. If | |
174 | * one gets preempted, we try to push it off to another queue. | |
175 | * So trying to keep a preempting RT task on the same | |
176 | * cache hot CPU will force the running RT task to | |
177 | * a cold CPU. So we waste all the cache for the lower | |
178 | * RT task in hopes of saving some of a RT task | |
179 | * that is just being woken and probably will have | |
180 | * cold cache anyway. | |
318e0893 | 181 | */ |
17b3279b GH |
182 | if (unlikely(rt_task(rq->curr)) && |
183 | (p->nr_cpus_allowed > 1)) { | |
318e0893 GH |
184 | int cpu = find_lowest_rq(p); |
185 | ||
186 | return (cpu == -1) ? task_cpu(p) : cpu; | |
187 | } | |
188 | ||
189 | /* | |
190 | * Otherwise, just let it ride on the affined RQ and the | |
191 | * post-schedule router will push the preempted task away | |
192 | */ | |
e7693a36 GH |
193 | return task_cpu(p); |
194 | } | |
195 | #endif /* CONFIG_SMP */ | |
196 | ||
bb44e5d1 IM |
197 | /* |
198 | * Preempt the current task with a newly woken task if needed: | |
199 | */ | |
200 | static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p) | |
201 | { | |
202 | if (p->prio < rq->curr->prio) | |
203 | resched_task(rq->curr); | |
204 | } | |
205 | ||
fb8d4724 | 206 | static struct task_struct *pick_next_task_rt(struct rq *rq) |
bb44e5d1 IM |
207 | { |
208 | struct rt_prio_array *array = &rq->rt.active; | |
209 | struct task_struct *next; | |
210 | struct list_head *queue; | |
211 | int idx; | |
212 | ||
213 | idx = sched_find_first_bit(array->bitmap); | |
214 | if (idx >= MAX_RT_PRIO) | |
215 | return NULL; | |
216 | ||
217 | queue = array->queue + idx; | |
fa717060 | 218 | next = list_entry(queue->next, struct task_struct, rt.run_list); |
bb44e5d1 | 219 | |
d281918d | 220 | next->se.exec_start = rq->clock; |
bb44e5d1 IM |
221 | |
222 | return next; | |
223 | } | |
224 | ||
31ee529c | 225 | static void put_prev_task_rt(struct rq *rq, struct task_struct *p) |
bb44e5d1 | 226 | { |
f1e14ef6 | 227 | update_curr_rt(rq); |
bb44e5d1 IM |
228 | p->se.exec_start = 0; |
229 | } | |
230 | ||
681f3e68 | 231 | #ifdef CONFIG_SMP |
e8fa1362 SR |
232 | /* Only try algorithms three times */ |
233 | #define RT_MAX_TRIES 3 | |
234 | ||
235 | static int double_lock_balance(struct rq *this_rq, struct rq *busiest); | |
236 | static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep); | |
237 | ||
f65eda4f SR |
238 | static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu) |
239 | { | |
240 | if (!task_running(rq, p) && | |
73fe6aae GH |
241 | (cpu < 0 || cpu_isset(cpu, p->cpus_allowed)) && |
242 | (p->nr_cpus_allowed > 1)) | |
f65eda4f SR |
243 | return 1; |
244 | return 0; | |
245 | } | |
246 | ||
e8fa1362 | 247 | /* Return the second highest RT task, NULL otherwise */ |
79064fbf | 248 | static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu) |
e8fa1362 SR |
249 | { |
250 | struct rt_prio_array *array = &rq->rt.active; | |
251 | struct task_struct *next; | |
252 | struct list_head *queue; | |
253 | int idx; | |
254 | ||
e8fa1362 SR |
255 | if (likely(rq->rt.rt_nr_running < 2)) |
256 | return NULL; | |
257 | ||
258 | idx = sched_find_first_bit(array->bitmap); | |
259 | if (unlikely(idx >= MAX_RT_PRIO)) { | |
260 | WARN_ON(1); /* rt_nr_running is bad */ | |
261 | return NULL; | |
262 | } | |
263 | ||
264 | queue = array->queue + idx; | |
f65eda4f SR |
265 | BUG_ON(list_empty(queue)); |
266 | ||
fa717060 | 267 | next = list_entry(queue->next, struct task_struct, rt.run_list); |
f65eda4f SR |
268 | if (unlikely(pick_rt_task(rq, next, cpu))) |
269 | goto out; | |
e8fa1362 SR |
270 | |
271 | if (queue->next->next != queue) { | |
272 | /* same prio task */ | |
79064fbf | 273 | next = list_entry(queue->next->next, struct task_struct, |
fa717060 | 274 | rt.run_list); |
f65eda4f SR |
275 | if (pick_rt_task(rq, next, cpu)) |
276 | goto out; | |
e8fa1362 SR |
277 | } |
278 | ||
f65eda4f | 279 | retry: |
e8fa1362 SR |
280 | /* slower, but more flexible */ |
281 | idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1); | |
f65eda4f | 282 | if (unlikely(idx >= MAX_RT_PRIO)) |
e8fa1362 | 283 | return NULL; |
e8fa1362 SR |
284 | |
285 | queue = array->queue + idx; | |
f65eda4f SR |
286 | BUG_ON(list_empty(queue)); |
287 | ||
fa717060 | 288 | list_for_each_entry(next, queue, rt.run_list) { |
f65eda4f SR |
289 | if (pick_rt_task(rq, next, cpu)) |
290 | goto out; | |
291 | } | |
292 | ||
293 | goto retry; | |
e8fa1362 | 294 | |
f65eda4f | 295 | out: |
e8fa1362 SR |
296 | return next; |
297 | } | |
298 | ||
299 | static DEFINE_PER_CPU(cpumask_t, local_cpu_mask); | |
300 | ||
6e1254d2 | 301 | static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask) |
e8fa1362 | 302 | { |
6e1254d2 | 303 | int lowest_prio = -1; |
610bf056 | 304 | int lowest_cpu = -1; |
06f90dbd | 305 | int count = 0; |
610bf056 | 306 | int cpu; |
e8fa1362 | 307 | |
637f5085 | 308 | cpus_and(*lowest_mask, task_rq(task)->rd->online, task->cpus_allowed); |
e8fa1362 | 309 | |
07b4032c GH |
310 | /* |
311 | * Scan each rq for the lowest prio. | |
312 | */ | |
610bf056 | 313 | for_each_cpu_mask(cpu, *lowest_mask) { |
07b4032c | 314 | struct rq *rq = cpu_rq(cpu); |
e8fa1362 | 315 | |
07b4032c GH |
316 | /* We look for lowest RT prio or non-rt CPU */ |
317 | if (rq->rt.highest_prio >= MAX_RT_PRIO) { | |
610bf056 SR |
318 | /* |
319 | * if we already found a low RT queue | |
320 | * and now we found this non-rt queue | |
321 | * clear the mask and set our bit. | |
322 | * Otherwise just return the queue as is | |
323 | * and the count==1 will cause the algorithm | |
324 | * to use the first bit found. | |
325 | */ | |
326 | if (lowest_cpu != -1) { | |
6e1254d2 | 327 | cpus_clear(*lowest_mask); |
610bf056 SR |
328 | cpu_set(rq->cpu, *lowest_mask); |
329 | } | |
6e1254d2 | 330 | return 1; |
07b4032c GH |
331 | } |
332 | ||
333 | /* no locking for now */ | |
6e1254d2 GH |
334 | if ((rq->rt.highest_prio > task->prio) |
335 | && (rq->rt.highest_prio >= lowest_prio)) { | |
336 | if (rq->rt.highest_prio > lowest_prio) { | |
337 | /* new low - clear old data */ | |
338 | lowest_prio = rq->rt.highest_prio; | |
610bf056 SR |
339 | lowest_cpu = cpu; |
340 | count = 0; | |
6e1254d2 | 341 | } |
06f90dbd | 342 | count++; |
610bf056 SR |
343 | } else |
344 | cpu_clear(cpu, *lowest_mask); | |
345 | } | |
346 | ||
347 | /* | |
348 | * Clear out all the set bits that represent | |
349 | * runqueues that were of higher prio than | |
350 | * the lowest_prio. | |
351 | */ | |
352 | if (lowest_cpu > 0) { | |
353 | /* | |
354 | * Perhaps we could add another cpumask op to | |
355 | * zero out bits. Like cpu_zero_bits(cpumask, nrbits); | |
356 | * Then that could be optimized to use memset and such. | |
357 | */ | |
358 | for_each_cpu_mask(cpu, *lowest_mask) { | |
359 | if (cpu >= lowest_cpu) | |
360 | break; | |
361 | cpu_clear(cpu, *lowest_mask); | |
e8fa1362 | 362 | } |
07b4032c GH |
363 | } |
364 | ||
06f90dbd | 365 | return count; |
6e1254d2 GH |
366 | } |
367 | ||
368 | static inline int pick_optimal_cpu(int this_cpu, cpumask_t *mask) | |
369 | { | |
370 | int first; | |
371 | ||
372 | /* "this_cpu" is cheaper to preempt than a remote processor */ | |
373 | if ((this_cpu != -1) && cpu_isset(this_cpu, *mask)) | |
374 | return this_cpu; | |
375 | ||
376 | first = first_cpu(*mask); | |
377 | if (first != NR_CPUS) | |
378 | return first; | |
379 | ||
380 | return -1; | |
381 | } | |
382 | ||
383 | static int find_lowest_rq(struct task_struct *task) | |
384 | { | |
385 | struct sched_domain *sd; | |
386 | cpumask_t *lowest_mask = &__get_cpu_var(local_cpu_mask); | |
387 | int this_cpu = smp_processor_id(); | |
388 | int cpu = task_cpu(task); | |
06f90dbd GH |
389 | int count = find_lowest_cpus(task, lowest_mask); |
390 | ||
391 | if (!count) | |
392 | return -1; /* No targets found */ | |
6e1254d2 | 393 | |
06f90dbd GH |
394 | /* |
395 | * There is no sense in performing an optimal search if only one | |
396 | * target is found. | |
397 | */ | |
398 | if (count == 1) | |
399 | return first_cpu(*lowest_mask); | |
6e1254d2 GH |
400 | |
401 | /* | |
402 | * At this point we have built a mask of cpus representing the | |
403 | * lowest priority tasks in the system. Now we want to elect | |
404 | * the best one based on our affinity and topology. | |
405 | * | |
406 | * We prioritize the last cpu that the task executed on since | |
407 | * it is most likely cache-hot in that location. | |
408 | */ | |
409 | if (cpu_isset(cpu, *lowest_mask)) | |
410 | return cpu; | |
411 | ||
412 | /* | |
413 | * Otherwise, we consult the sched_domains span maps to figure | |
414 | * out which cpu is logically closest to our hot cache data. | |
415 | */ | |
416 | if (this_cpu == cpu) | |
417 | this_cpu = -1; /* Skip this_cpu opt if the same */ | |
418 | ||
419 | for_each_domain(cpu, sd) { | |
420 | if (sd->flags & SD_WAKE_AFFINE) { | |
421 | cpumask_t domain_mask; | |
422 | int best_cpu; | |
423 | ||
424 | cpus_and(domain_mask, sd->span, *lowest_mask); | |
425 | ||
426 | best_cpu = pick_optimal_cpu(this_cpu, | |
427 | &domain_mask); | |
428 | if (best_cpu != -1) | |
429 | return best_cpu; | |
430 | } | |
431 | } | |
432 | ||
433 | /* | |
434 | * And finally, if there were no matches within the domains | |
435 | * just give the caller *something* to work with from the compatible | |
436 | * locations. | |
437 | */ | |
438 | return pick_optimal_cpu(this_cpu, lowest_mask); | |
07b4032c GH |
439 | } |
440 | ||
441 | /* Will lock the rq it finds */ | |
4df64c0b | 442 | static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq) |
07b4032c GH |
443 | { |
444 | struct rq *lowest_rq = NULL; | |
07b4032c | 445 | int tries; |
4df64c0b | 446 | int cpu; |
e8fa1362 | 447 | |
07b4032c GH |
448 | for (tries = 0; tries < RT_MAX_TRIES; tries++) { |
449 | cpu = find_lowest_rq(task); | |
450 | ||
2de0b463 | 451 | if ((cpu == -1) || (cpu == rq->cpu)) |
e8fa1362 SR |
452 | break; |
453 | ||
07b4032c GH |
454 | lowest_rq = cpu_rq(cpu); |
455 | ||
e8fa1362 | 456 | /* if the prio of this runqueue changed, try again */ |
07b4032c | 457 | if (double_lock_balance(rq, lowest_rq)) { |
e8fa1362 SR |
458 | /* |
459 | * We had to unlock the run queue. In | |
460 | * the mean time, task could have | |
461 | * migrated already or had its affinity changed. | |
462 | * Also make sure that it wasn't scheduled on its rq. | |
463 | */ | |
07b4032c | 464 | if (unlikely(task_rq(task) != rq || |
4df64c0b IM |
465 | !cpu_isset(lowest_rq->cpu, |
466 | task->cpus_allowed) || | |
07b4032c | 467 | task_running(rq, task) || |
e8fa1362 | 468 | !task->se.on_rq)) { |
4df64c0b | 469 | |
e8fa1362 SR |
470 | spin_unlock(&lowest_rq->lock); |
471 | lowest_rq = NULL; | |
472 | break; | |
473 | } | |
474 | } | |
475 | ||
476 | /* If this rq is still suitable use it. */ | |
477 | if (lowest_rq->rt.highest_prio > task->prio) | |
478 | break; | |
479 | ||
480 | /* try again */ | |
481 | spin_unlock(&lowest_rq->lock); | |
482 | lowest_rq = NULL; | |
483 | } | |
484 | ||
485 | return lowest_rq; | |
486 | } | |
487 | ||
488 | /* | |
489 | * If the current CPU has more than one RT task, see if the non | |
490 | * running task can migrate over to a CPU that is running a task | |
491 | * of lesser priority. | |
492 | */ | |
697f0a48 | 493 | static int push_rt_task(struct rq *rq) |
e8fa1362 SR |
494 | { |
495 | struct task_struct *next_task; | |
496 | struct rq *lowest_rq; | |
497 | int ret = 0; | |
498 | int paranoid = RT_MAX_TRIES; | |
499 | ||
a22d7fc1 GH |
500 | if (!rq->rt.overloaded) |
501 | return 0; | |
502 | ||
697f0a48 | 503 | next_task = pick_next_highest_task_rt(rq, -1); |
e8fa1362 SR |
504 | if (!next_task) |
505 | return 0; | |
506 | ||
507 | retry: | |
697f0a48 | 508 | if (unlikely(next_task == rq->curr)) { |
f65eda4f | 509 | WARN_ON(1); |
e8fa1362 | 510 | return 0; |
f65eda4f | 511 | } |
e8fa1362 SR |
512 | |
513 | /* | |
514 | * It's possible that the next_task slipped in of | |
515 | * higher priority than current. If that's the case | |
516 | * just reschedule current. | |
517 | */ | |
697f0a48 GH |
518 | if (unlikely(next_task->prio < rq->curr->prio)) { |
519 | resched_task(rq->curr); | |
e8fa1362 SR |
520 | return 0; |
521 | } | |
522 | ||
697f0a48 | 523 | /* We might release rq lock */ |
e8fa1362 SR |
524 | get_task_struct(next_task); |
525 | ||
526 | /* find_lock_lowest_rq locks the rq if found */ | |
697f0a48 | 527 | lowest_rq = find_lock_lowest_rq(next_task, rq); |
e8fa1362 SR |
528 | if (!lowest_rq) { |
529 | struct task_struct *task; | |
530 | /* | |
697f0a48 | 531 | * find lock_lowest_rq releases rq->lock |
e8fa1362 SR |
532 | * so it is possible that next_task has changed. |
533 | * If it has, then try again. | |
534 | */ | |
697f0a48 | 535 | task = pick_next_highest_task_rt(rq, -1); |
e8fa1362 SR |
536 | if (unlikely(task != next_task) && task && paranoid--) { |
537 | put_task_struct(next_task); | |
538 | next_task = task; | |
539 | goto retry; | |
540 | } | |
541 | goto out; | |
542 | } | |
543 | ||
697f0a48 | 544 | deactivate_task(rq, next_task, 0); |
e8fa1362 SR |
545 | set_task_cpu(next_task, lowest_rq->cpu); |
546 | activate_task(lowest_rq, next_task, 0); | |
547 | ||
548 | resched_task(lowest_rq->curr); | |
549 | ||
550 | spin_unlock(&lowest_rq->lock); | |
551 | ||
552 | ret = 1; | |
553 | out: | |
554 | put_task_struct(next_task); | |
555 | ||
556 | return ret; | |
557 | } | |
558 | ||
559 | /* | |
560 | * TODO: Currently we just use the second highest prio task on | |
561 | * the queue, and stop when it can't migrate (or there's | |
562 | * no more RT tasks). There may be a case where a lower | |
563 | * priority RT task has a different affinity than the | |
564 | * higher RT task. In this case the lower RT task could | |
565 | * possibly be able to migrate where as the higher priority | |
566 | * RT task could not. We currently ignore this issue. | |
567 | * Enhancements are welcome! | |
568 | */ | |
569 | static void push_rt_tasks(struct rq *rq) | |
570 | { | |
571 | /* push_rt_task will return true if it moved an RT */ | |
572 | while (push_rt_task(rq)) | |
573 | ; | |
574 | } | |
575 | ||
f65eda4f SR |
576 | static int pull_rt_task(struct rq *this_rq) |
577 | { | |
80bf3171 IM |
578 | int this_cpu = this_rq->cpu, ret = 0, cpu; |
579 | struct task_struct *p, *next; | |
f65eda4f | 580 | struct rq *src_rq; |
f65eda4f | 581 | |
637f5085 | 582 | if (likely(!rt_overloaded(this_rq))) |
f65eda4f SR |
583 | return 0; |
584 | ||
585 | next = pick_next_task_rt(this_rq); | |
586 | ||
637f5085 | 587 | for_each_cpu_mask(cpu, this_rq->rd->rto_mask) { |
f65eda4f SR |
588 | if (this_cpu == cpu) |
589 | continue; | |
590 | ||
591 | src_rq = cpu_rq(cpu); | |
f65eda4f SR |
592 | /* |
593 | * We can potentially drop this_rq's lock in | |
594 | * double_lock_balance, and another CPU could | |
595 | * steal our next task - hence we must cause | |
596 | * the caller to recalculate the next task | |
597 | * in that case: | |
598 | */ | |
599 | if (double_lock_balance(this_rq, src_rq)) { | |
600 | struct task_struct *old_next = next; | |
80bf3171 | 601 | |
f65eda4f SR |
602 | next = pick_next_task_rt(this_rq); |
603 | if (next != old_next) | |
604 | ret = 1; | |
605 | } | |
606 | ||
607 | /* | |
608 | * Are there still pullable RT tasks? | |
609 | */ | |
610 | if (src_rq->rt.rt_nr_running <= 1) { | |
611 | spin_unlock(&src_rq->lock); | |
612 | continue; | |
613 | } | |
614 | ||
f65eda4f SR |
615 | p = pick_next_highest_task_rt(src_rq, this_cpu); |
616 | ||
617 | /* | |
618 | * Do we have an RT task that preempts | |
619 | * the to-be-scheduled task? | |
620 | */ | |
621 | if (p && (!next || (p->prio < next->prio))) { | |
622 | WARN_ON(p == src_rq->curr); | |
623 | WARN_ON(!p->se.on_rq); | |
624 | ||
625 | /* | |
626 | * There's a chance that p is higher in priority | |
627 | * than what's currently running on its cpu. | |
628 | * This is just that p is wakeing up and hasn't | |
629 | * had a chance to schedule. We only pull | |
630 | * p if it is lower in priority than the | |
631 | * current task on the run queue or | |
632 | * this_rq next task is lower in prio than | |
633 | * the current task on that rq. | |
634 | */ | |
635 | if (p->prio < src_rq->curr->prio || | |
636 | (next && next->prio < src_rq->curr->prio)) | |
80bf3171 | 637 | goto out; |
f65eda4f SR |
638 | |
639 | ret = 1; | |
640 | ||
641 | deactivate_task(src_rq, p, 0); | |
642 | set_task_cpu(p, this_cpu); | |
643 | activate_task(this_rq, p, 0); | |
644 | /* | |
645 | * We continue with the search, just in | |
646 | * case there's an even higher prio task | |
647 | * in another runqueue. (low likelyhood | |
648 | * but possible) | |
80bf3171 | 649 | * |
f65eda4f SR |
650 | * Update next so that we won't pick a task |
651 | * on another cpu with a priority lower (or equal) | |
652 | * than the one we just picked. | |
653 | */ | |
654 | next = p; | |
655 | ||
656 | } | |
80bf3171 | 657 | out: |
f65eda4f SR |
658 | spin_unlock(&src_rq->lock); |
659 | } | |
660 | ||
661 | return ret; | |
662 | } | |
663 | ||
9a897c5a | 664 | static void pre_schedule_rt(struct rq *rq, struct task_struct *prev) |
f65eda4f SR |
665 | { |
666 | /* Try to pull RT tasks here if we lower this rq's prio */ | |
7f51f298 | 667 | if (unlikely(rt_task(prev)) && rq->rt.highest_prio > prev->prio) |
f65eda4f SR |
668 | pull_rt_task(rq); |
669 | } | |
670 | ||
9a897c5a | 671 | static void post_schedule_rt(struct rq *rq) |
e8fa1362 SR |
672 | { |
673 | /* | |
674 | * If we have more than one rt_task queued, then | |
675 | * see if we can push the other rt_tasks off to other CPUS. | |
676 | * Note we may release the rq lock, and since | |
677 | * the lock was owned by prev, we need to release it | |
678 | * first via finish_lock_switch and then reaquire it here. | |
679 | */ | |
a22d7fc1 | 680 | if (unlikely(rq->rt.overloaded)) { |
e8fa1362 SR |
681 | spin_lock_irq(&rq->lock); |
682 | push_rt_tasks(rq); | |
683 | spin_unlock_irq(&rq->lock); | |
684 | } | |
685 | } | |
686 | ||
4642dafd | 687 | |
9a897c5a | 688 | static void task_wake_up_rt(struct rq *rq, struct task_struct *p) |
4642dafd | 689 | { |
9a897c5a | 690 | if (!task_running(rq, p) && |
a22d7fc1 GH |
691 | (p->prio >= rq->rt.highest_prio) && |
692 | rq->rt.overloaded) | |
4642dafd SR |
693 | push_rt_tasks(rq); |
694 | } | |
695 | ||
43010659 | 696 | static unsigned long |
bb44e5d1 | 697 | load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest, |
e1d1484f PW |
698 | unsigned long max_load_move, |
699 | struct sched_domain *sd, enum cpu_idle_type idle, | |
700 | int *all_pinned, int *this_best_prio) | |
bb44e5d1 | 701 | { |
c7a1e46a SR |
702 | /* don't touch RT tasks */ |
703 | return 0; | |
e1d1484f PW |
704 | } |
705 | ||
706 | static int | |
707 | move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest, | |
708 | struct sched_domain *sd, enum cpu_idle_type idle) | |
709 | { | |
c7a1e46a SR |
710 | /* don't touch RT tasks */ |
711 | return 0; | |
bb44e5d1 | 712 | } |
deeeccd4 | 713 | |
73fe6aae GH |
714 | static void set_cpus_allowed_rt(struct task_struct *p, cpumask_t *new_mask) |
715 | { | |
716 | int weight = cpus_weight(*new_mask); | |
717 | ||
718 | BUG_ON(!rt_task(p)); | |
719 | ||
720 | /* | |
721 | * Update the migration status of the RQ if we have an RT task | |
722 | * which is running AND changing its weight value. | |
723 | */ | |
724 | if (p->se.on_rq && (weight != p->nr_cpus_allowed)) { | |
725 | struct rq *rq = task_rq(p); | |
726 | ||
deeeccd4 | 727 | if ((p->nr_cpus_allowed <= 1) && (weight > 1)) { |
73fe6aae | 728 | rq->rt.rt_nr_migratory++; |
deeeccd4 | 729 | } else if ((p->nr_cpus_allowed > 1) && (weight <= 1)) { |
73fe6aae GH |
730 | BUG_ON(!rq->rt.rt_nr_migratory); |
731 | rq->rt.rt_nr_migratory--; | |
732 | } | |
733 | ||
734 | update_rt_migration(rq); | |
735 | } | |
736 | ||
737 | p->cpus_allowed = *new_mask; | |
738 | p->nr_cpus_allowed = weight; | |
739 | } | |
deeeccd4 | 740 | |
bdd7c81b IM |
741 | /* Assumes rq->lock is held */ |
742 | static void join_domain_rt(struct rq *rq) | |
743 | { | |
744 | if (rq->rt.overloaded) | |
745 | rt_set_overload(rq); | |
746 | } | |
747 | ||
748 | /* Assumes rq->lock is held */ | |
749 | static void leave_domain_rt(struct rq *rq) | |
750 | { | |
751 | if (rq->rt.overloaded) | |
752 | rt_clear_overload(rq); | |
753 | } | |
cb469845 SR |
754 | |
755 | /* | |
756 | * When switch from the rt queue, we bring ourselves to a position | |
757 | * that we might want to pull RT tasks from other runqueues. | |
758 | */ | |
759 | static void switched_from_rt(struct rq *rq, struct task_struct *p, | |
760 | int running) | |
761 | { | |
762 | /* | |
763 | * If there are other RT tasks then we will reschedule | |
764 | * and the scheduling of the other RT tasks will handle | |
765 | * the balancing. But if we are the last RT task | |
766 | * we may need to handle the pulling of RT tasks | |
767 | * now. | |
768 | */ | |
769 | if (!rq->rt.rt_nr_running) | |
770 | pull_rt_task(rq); | |
771 | } | |
772 | #endif /* CONFIG_SMP */ | |
773 | ||
774 | /* | |
775 | * When switching a task to RT, we may overload the runqueue | |
776 | * with RT tasks. In this case we try to push them off to | |
777 | * other runqueues. | |
778 | */ | |
779 | static void switched_to_rt(struct rq *rq, struct task_struct *p, | |
780 | int running) | |
781 | { | |
782 | int check_resched = 1; | |
783 | ||
784 | /* | |
785 | * If we are already running, then there's nothing | |
786 | * that needs to be done. But if we are not running | |
787 | * we may need to preempt the current running task. | |
788 | * If that current running task is also an RT task | |
789 | * then see if we can move to another run queue. | |
790 | */ | |
791 | if (!running) { | |
792 | #ifdef CONFIG_SMP | |
793 | if (rq->rt.overloaded && push_rt_task(rq) && | |
794 | /* Don't resched if we changed runqueues */ | |
795 | rq != task_rq(p)) | |
796 | check_resched = 0; | |
797 | #endif /* CONFIG_SMP */ | |
798 | if (check_resched && p->prio < rq->curr->prio) | |
799 | resched_task(rq->curr); | |
800 | } | |
801 | } | |
802 | ||
803 | /* | |
804 | * Priority of the task has changed. This may cause | |
805 | * us to initiate a push or pull. | |
806 | */ | |
807 | static void prio_changed_rt(struct rq *rq, struct task_struct *p, | |
808 | int oldprio, int running) | |
809 | { | |
810 | if (running) { | |
811 | #ifdef CONFIG_SMP | |
812 | /* | |
813 | * If our priority decreases while running, we | |
814 | * may need to pull tasks to this runqueue. | |
815 | */ | |
816 | if (oldprio < p->prio) | |
817 | pull_rt_task(rq); | |
818 | /* | |
819 | * If there's a higher priority task waiting to run | |
820 | * then reschedule. | |
821 | */ | |
822 | if (p->prio > rq->rt.highest_prio) | |
823 | resched_task(p); | |
824 | #else | |
825 | /* For UP simply resched on drop of prio */ | |
826 | if (oldprio < p->prio) | |
827 | resched_task(p); | |
e8fa1362 | 828 | #endif /* CONFIG_SMP */ |
cb469845 SR |
829 | } else { |
830 | /* | |
831 | * This task is not running, but if it is | |
832 | * greater than the current running task | |
833 | * then reschedule. | |
834 | */ | |
835 | if (p->prio < rq->curr->prio) | |
836 | resched_task(rq->curr); | |
837 | } | |
838 | } | |
839 | ||
78f2c7db PZ |
840 | static void watchdog(struct rq *rq, struct task_struct *p) |
841 | { | |
842 | unsigned long soft, hard; | |
843 | ||
844 | if (!p->signal) | |
845 | return; | |
846 | ||
847 | soft = p->signal->rlim[RLIMIT_RTTIME].rlim_cur; | |
848 | hard = p->signal->rlim[RLIMIT_RTTIME].rlim_max; | |
849 | ||
850 | if (soft != RLIM_INFINITY) { | |
851 | unsigned long next; | |
852 | ||
853 | p->rt.timeout++; | |
854 | next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ); | |
855 | if (next > p->rt.timeout) { | |
856 | u64 next_time = p->se.sum_exec_runtime; | |
857 | ||
858 | next_time += next * (NSEC_PER_SEC/HZ); | |
859 | if (p->it_sched_expires > next_time) | |
860 | p->it_sched_expires = next_time; | |
861 | } else | |
862 | p->it_sched_expires = p->se.sum_exec_runtime; | |
863 | } | |
864 | } | |
bb44e5d1 IM |
865 | |
866 | static void task_tick_rt(struct rq *rq, struct task_struct *p) | |
867 | { | |
67e2be02 PZ |
868 | update_curr_rt(rq); |
869 | ||
78f2c7db PZ |
870 | watchdog(rq, p); |
871 | ||
bb44e5d1 IM |
872 | /* |
873 | * RR tasks need a special form of timeslice management. | |
874 | * FIFO tasks have no timeslices. | |
875 | */ | |
876 | if (p->policy != SCHED_RR) | |
877 | return; | |
878 | ||
fa717060 | 879 | if (--p->rt.time_slice) |
bb44e5d1 IM |
880 | return; |
881 | ||
fa717060 | 882 | p->rt.time_slice = DEF_TIMESLICE; |
bb44e5d1 | 883 | |
98fbc798 DA |
884 | /* |
885 | * Requeue to the end of queue if we are not the only element | |
886 | * on the queue: | |
887 | */ | |
fa717060 | 888 | if (p->rt.run_list.prev != p->rt.run_list.next) { |
98fbc798 DA |
889 | requeue_task_rt(rq, p); |
890 | set_tsk_need_resched(p); | |
891 | } | |
bb44e5d1 IM |
892 | } |
893 | ||
83b699ed SV |
894 | static void set_curr_task_rt(struct rq *rq) |
895 | { | |
896 | struct task_struct *p = rq->curr; | |
897 | ||
898 | p->se.exec_start = rq->clock; | |
899 | } | |
900 | ||
5522d5d5 IM |
901 | const struct sched_class rt_sched_class = { |
902 | .next = &fair_sched_class, | |
bb44e5d1 IM |
903 | .enqueue_task = enqueue_task_rt, |
904 | .dequeue_task = dequeue_task_rt, | |
905 | .yield_task = yield_task_rt, | |
e7693a36 GH |
906 | #ifdef CONFIG_SMP |
907 | .select_task_rq = select_task_rq_rt, | |
908 | #endif /* CONFIG_SMP */ | |
bb44e5d1 IM |
909 | |
910 | .check_preempt_curr = check_preempt_curr_rt, | |
911 | ||
912 | .pick_next_task = pick_next_task_rt, | |
913 | .put_prev_task = put_prev_task_rt, | |
914 | ||
681f3e68 | 915 | #ifdef CONFIG_SMP |
bb44e5d1 | 916 | .load_balance = load_balance_rt, |
e1d1484f | 917 | .move_one_task = move_one_task_rt, |
73fe6aae | 918 | .set_cpus_allowed = set_cpus_allowed_rt, |
bdd7c81b IM |
919 | .join_domain = join_domain_rt, |
920 | .leave_domain = leave_domain_rt, | |
9a897c5a SR |
921 | .pre_schedule = pre_schedule_rt, |
922 | .post_schedule = post_schedule_rt, | |
923 | .task_wake_up = task_wake_up_rt, | |
cb469845 | 924 | .switched_from = switched_from_rt, |
681f3e68 | 925 | #endif |
bb44e5d1 | 926 | |
83b699ed | 927 | .set_curr_task = set_curr_task_rt, |
bb44e5d1 | 928 | .task_tick = task_tick_rt, |
cb469845 SR |
929 | |
930 | .prio_changed = prio_changed_rt, | |
931 | .switched_to = switched_to_rt, | |
bb44e5d1 | 932 | }; |