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1 | /* |
2 | * Deadline Scheduling Class (SCHED_DEADLINE) | |
3 | * | |
4 | * Earliest Deadline First (EDF) + Constant Bandwidth Server (CBS). | |
5 | * | |
6 | * Tasks that periodically executes their instances for less than their | |
7 | * runtime won't miss any of their deadlines. | |
8 | * Tasks that are not periodic or sporadic or that tries to execute more | |
9 | * than their reserved bandwidth will be slowed down (and may potentially | |
10 | * miss some of their deadlines), and won't affect any other task. | |
11 | * | |
12 | * Copyright (C) 2012 Dario Faggioli <raistlin@linux.it>, | |
13 | * Michael Trimarchi <michael@amarulasolutions.com>, | |
14 | * Fabio Checconi <fchecconi@gmail.com> | |
15 | */ | |
16 | #include "sched.h" | |
17 | ||
18 | static inline int dl_time_before(u64 a, u64 b) | |
19 | { | |
20 | return (s64)(a - b) < 0; | |
21 | } | |
22 | ||
23 | static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se) | |
24 | { | |
25 | return container_of(dl_se, struct task_struct, dl); | |
26 | } | |
27 | ||
28 | static inline struct rq *rq_of_dl_rq(struct dl_rq *dl_rq) | |
29 | { | |
30 | return container_of(dl_rq, struct rq, dl); | |
31 | } | |
32 | ||
33 | static inline struct dl_rq *dl_rq_of_se(struct sched_dl_entity *dl_se) | |
34 | { | |
35 | struct task_struct *p = dl_task_of(dl_se); | |
36 | struct rq *rq = task_rq(p); | |
37 | ||
38 | return &rq->dl; | |
39 | } | |
40 | ||
41 | static inline int on_dl_rq(struct sched_dl_entity *dl_se) | |
42 | { | |
43 | return !RB_EMPTY_NODE(&dl_se->rb_node); | |
44 | } | |
45 | ||
46 | static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq) | |
47 | { | |
48 | struct sched_dl_entity *dl_se = &p->dl; | |
49 | ||
50 | return dl_rq->rb_leftmost == &dl_se->rb_node; | |
51 | } | |
52 | ||
53 | void init_dl_rq(struct dl_rq *dl_rq, struct rq *rq) | |
54 | { | |
55 | dl_rq->rb_root = RB_ROOT; | |
56 | } | |
57 | ||
58 | static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags); | |
59 | static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags); | |
60 | static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p, | |
61 | int flags); | |
62 | ||
63 | /* | |
64 | * We are being explicitly informed that a new instance is starting, | |
65 | * and this means that: | |
66 | * - the absolute deadline of the entity has to be placed at | |
67 | * current time + relative deadline; | |
68 | * - the runtime of the entity has to be set to the maximum value. | |
69 | * | |
70 | * The capability of specifying such event is useful whenever a -deadline | |
71 | * entity wants to (try to!) synchronize its behaviour with the scheduler's | |
72 | * one, and to (try to!) reconcile itself with its own scheduling | |
73 | * parameters. | |
74 | */ | |
75 | static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se) | |
76 | { | |
77 | struct dl_rq *dl_rq = dl_rq_of_se(dl_se); | |
78 | struct rq *rq = rq_of_dl_rq(dl_rq); | |
79 | ||
80 | WARN_ON(!dl_se->dl_new || dl_se->dl_throttled); | |
81 | ||
82 | /* | |
83 | * We use the regular wall clock time to set deadlines in the | |
84 | * future; in fact, we must consider execution overheads (time | |
85 | * spent on hardirq context, etc.). | |
86 | */ | |
87 | dl_se->deadline = rq_clock(rq) + dl_se->dl_deadline; | |
88 | dl_se->runtime = dl_se->dl_runtime; | |
89 | dl_se->dl_new = 0; | |
90 | } | |
91 | ||
92 | /* | |
93 | * Pure Earliest Deadline First (EDF) scheduling does not deal with the | |
94 | * possibility of a entity lasting more than what it declared, and thus | |
95 | * exhausting its runtime. | |
96 | * | |
97 | * Here we are interested in making runtime overrun possible, but we do | |
98 | * not want a entity which is misbehaving to affect the scheduling of all | |
99 | * other entities. | |
100 | * Therefore, a budgeting strategy called Constant Bandwidth Server (CBS) | |
101 | * is used, in order to confine each entity within its own bandwidth. | |
102 | * | |
103 | * This function deals exactly with that, and ensures that when the runtime | |
104 | * of a entity is replenished, its deadline is also postponed. That ensures | |
105 | * the overrunning entity can't interfere with other entity in the system and | |
106 | * can't make them miss their deadlines. Reasons why this kind of overruns | |
107 | * could happen are, typically, a entity voluntarily trying to overcome its | |
108 | * runtime, or it just underestimated it during sched_setscheduler_ex(). | |
109 | */ | |
110 | static void replenish_dl_entity(struct sched_dl_entity *dl_se) | |
111 | { | |
112 | struct dl_rq *dl_rq = dl_rq_of_se(dl_se); | |
113 | struct rq *rq = rq_of_dl_rq(dl_rq); | |
114 | ||
115 | /* | |
116 | * We keep moving the deadline away until we get some | |
117 | * available runtime for the entity. This ensures correct | |
118 | * handling of situations where the runtime overrun is | |
119 | * arbitrary large. | |
120 | */ | |
121 | while (dl_se->runtime <= 0) { | |
122 | dl_se->deadline += dl_se->dl_deadline; | |
123 | dl_se->runtime += dl_se->dl_runtime; | |
124 | } | |
125 | ||
126 | /* | |
127 | * At this point, the deadline really should be "in | |
128 | * the future" with respect to rq->clock. If it's | |
129 | * not, we are, for some reason, lagging too much! | |
130 | * Anyway, after having warn userspace abut that, | |
131 | * we still try to keep the things running by | |
132 | * resetting the deadline and the budget of the | |
133 | * entity. | |
134 | */ | |
135 | if (dl_time_before(dl_se->deadline, rq_clock(rq))) { | |
136 | static bool lag_once = false; | |
137 | ||
138 | if (!lag_once) { | |
139 | lag_once = true; | |
140 | printk_sched("sched: DL replenish lagged to much\n"); | |
141 | } | |
142 | dl_se->deadline = rq_clock(rq) + dl_se->dl_deadline; | |
143 | dl_se->runtime = dl_se->dl_runtime; | |
144 | } | |
145 | } | |
146 | ||
147 | /* | |
148 | * Here we check if --at time t-- an entity (which is probably being | |
149 | * [re]activated or, in general, enqueued) can use its remaining runtime | |
150 | * and its current deadline _without_ exceeding the bandwidth it is | |
151 | * assigned (function returns true if it can't). We are in fact applying | |
152 | * one of the CBS rules: when a task wakes up, if the residual runtime | |
153 | * over residual deadline fits within the allocated bandwidth, then we | |
154 | * can keep the current (absolute) deadline and residual budget without | |
155 | * disrupting the schedulability of the system. Otherwise, we should | |
156 | * refill the runtime and set the deadline a period in the future, | |
157 | * because keeping the current (absolute) deadline of the task would | |
158 | * result in breaking guarantees promised to other tasks. | |
159 | * | |
160 | * This function returns true if: | |
161 | * | |
162 | * runtime / (deadline - t) > dl_runtime / dl_deadline , | |
163 | * | |
164 | * IOW we can't recycle current parameters. | |
165 | */ | |
166 | static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t) | |
167 | { | |
168 | u64 left, right; | |
169 | ||
170 | /* | |
171 | * left and right are the two sides of the equation above, | |
172 | * after a bit of shuffling to use multiplications instead | |
173 | * of divisions. | |
174 | * | |
175 | * Note that none of the time values involved in the two | |
176 | * multiplications are absolute: dl_deadline and dl_runtime | |
177 | * are the relative deadline and the maximum runtime of each | |
178 | * instance, runtime is the runtime left for the last instance | |
179 | * and (deadline - t), since t is rq->clock, is the time left | |
180 | * to the (absolute) deadline. Even if overflowing the u64 type | |
181 | * is very unlikely to occur in both cases, here we scale down | |
182 | * as we want to avoid that risk at all. Scaling down by 10 | |
183 | * means that we reduce granularity to 1us. We are fine with it, | |
184 | * since this is only a true/false check and, anyway, thinking | |
185 | * of anything below microseconds resolution is actually fiction | |
186 | * (but still we want to give the user that illusion >;). | |
187 | */ | |
188 | left = (dl_se->dl_deadline >> 10) * (dl_se->runtime >> 10); | |
189 | right = ((dl_se->deadline - t) >> 10) * (dl_se->dl_runtime >> 10); | |
190 | ||
191 | return dl_time_before(right, left); | |
192 | } | |
193 | ||
194 | /* | |
195 | * When a -deadline entity is queued back on the runqueue, its runtime and | |
196 | * deadline might need updating. | |
197 | * | |
198 | * The policy here is that we update the deadline of the entity only if: | |
199 | * - the current deadline is in the past, | |
200 | * - using the remaining runtime with the current deadline would make | |
201 | * the entity exceed its bandwidth. | |
202 | */ | |
203 | static void update_dl_entity(struct sched_dl_entity *dl_se) | |
204 | { | |
205 | struct dl_rq *dl_rq = dl_rq_of_se(dl_se); | |
206 | struct rq *rq = rq_of_dl_rq(dl_rq); | |
207 | ||
208 | /* | |
209 | * The arrival of a new instance needs special treatment, i.e., | |
210 | * the actual scheduling parameters have to be "renewed". | |
211 | */ | |
212 | if (dl_se->dl_new) { | |
213 | setup_new_dl_entity(dl_se); | |
214 | return; | |
215 | } | |
216 | ||
217 | if (dl_time_before(dl_se->deadline, rq_clock(rq)) || | |
218 | dl_entity_overflow(dl_se, rq_clock(rq))) { | |
219 | dl_se->deadline = rq_clock(rq) + dl_se->dl_deadline; | |
220 | dl_se->runtime = dl_se->dl_runtime; | |
221 | } | |
222 | } | |
223 | ||
224 | /* | |
225 | * If the entity depleted all its runtime, and if we want it to sleep | |
226 | * while waiting for some new execution time to become available, we | |
227 | * set the bandwidth enforcement timer to the replenishment instant | |
228 | * and try to activate it. | |
229 | * | |
230 | * Notice that it is important for the caller to know if the timer | |
231 | * actually started or not (i.e., the replenishment instant is in | |
232 | * the future or in the past). | |
233 | */ | |
234 | static int start_dl_timer(struct sched_dl_entity *dl_se) | |
235 | { | |
236 | struct dl_rq *dl_rq = dl_rq_of_se(dl_se); | |
237 | struct rq *rq = rq_of_dl_rq(dl_rq); | |
238 | ktime_t now, act; | |
239 | ktime_t soft, hard; | |
240 | unsigned long range; | |
241 | s64 delta; | |
242 | ||
243 | /* | |
244 | * We want the timer to fire at the deadline, but considering | |
245 | * that it is actually coming from rq->clock and not from | |
246 | * hrtimer's time base reading. | |
247 | */ | |
248 | act = ns_to_ktime(dl_se->deadline); | |
249 | now = hrtimer_cb_get_time(&dl_se->dl_timer); | |
250 | delta = ktime_to_ns(now) - rq_clock(rq); | |
251 | act = ktime_add_ns(act, delta); | |
252 | ||
253 | /* | |
254 | * If the expiry time already passed, e.g., because the value | |
255 | * chosen as the deadline is too small, don't even try to | |
256 | * start the timer in the past! | |
257 | */ | |
258 | if (ktime_us_delta(act, now) < 0) | |
259 | return 0; | |
260 | ||
261 | hrtimer_set_expires(&dl_se->dl_timer, act); | |
262 | ||
263 | soft = hrtimer_get_softexpires(&dl_se->dl_timer); | |
264 | hard = hrtimer_get_expires(&dl_se->dl_timer); | |
265 | range = ktime_to_ns(ktime_sub(hard, soft)); | |
266 | __hrtimer_start_range_ns(&dl_se->dl_timer, soft, | |
267 | range, HRTIMER_MODE_ABS, 0); | |
268 | ||
269 | return hrtimer_active(&dl_se->dl_timer); | |
270 | } | |
271 | ||
272 | /* | |
273 | * This is the bandwidth enforcement timer callback. If here, we know | |
274 | * a task is not on its dl_rq, since the fact that the timer was running | |
275 | * means the task is throttled and needs a runtime replenishment. | |
276 | * | |
277 | * However, what we actually do depends on the fact the task is active, | |
278 | * (it is on its rq) or has been removed from there by a call to | |
279 | * dequeue_task_dl(). In the former case we must issue the runtime | |
280 | * replenishment and add the task back to the dl_rq; in the latter, we just | |
281 | * do nothing but clearing dl_throttled, so that runtime and deadline | |
282 | * updating (and the queueing back to dl_rq) will be done by the | |
283 | * next call to enqueue_task_dl(). | |
284 | */ | |
285 | static enum hrtimer_restart dl_task_timer(struct hrtimer *timer) | |
286 | { | |
287 | struct sched_dl_entity *dl_se = container_of(timer, | |
288 | struct sched_dl_entity, | |
289 | dl_timer); | |
290 | struct task_struct *p = dl_task_of(dl_se); | |
291 | struct rq *rq = task_rq(p); | |
292 | raw_spin_lock(&rq->lock); | |
293 | ||
294 | /* | |
295 | * We need to take care of a possible races here. In fact, the | |
296 | * task might have changed its scheduling policy to something | |
297 | * different from SCHED_DEADLINE or changed its reservation | |
298 | * parameters (through sched_setscheduler()). | |
299 | */ | |
300 | if (!dl_task(p) || dl_se->dl_new) | |
301 | goto unlock; | |
302 | ||
303 | sched_clock_tick(); | |
304 | update_rq_clock(rq); | |
305 | dl_se->dl_throttled = 0; | |
306 | if (p->on_rq) { | |
307 | enqueue_task_dl(rq, p, ENQUEUE_REPLENISH); | |
308 | if (task_has_dl_policy(rq->curr)) | |
309 | check_preempt_curr_dl(rq, p, 0); | |
310 | else | |
311 | resched_task(rq->curr); | |
312 | } | |
313 | unlock: | |
314 | raw_spin_unlock(&rq->lock); | |
315 | ||
316 | return HRTIMER_NORESTART; | |
317 | } | |
318 | ||
319 | void init_dl_task_timer(struct sched_dl_entity *dl_se) | |
320 | { | |
321 | struct hrtimer *timer = &dl_se->dl_timer; | |
322 | ||
323 | if (hrtimer_active(timer)) { | |
324 | hrtimer_try_to_cancel(timer); | |
325 | return; | |
326 | } | |
327 | ||
328 | hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
329 | timer->function = dl_task_timer; | |
330 | } | |
331 | ||
332 | static | |
333 | int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se) | |
334 | { | |
335 | int dmiss = dl_time_before(dl_se->deadline, rq_clock(rq)); | |
336 | int rorun = dl_se->runtime <= 0; | |
337 | ||
338 | if (!rorun && !dmiss) | |
339 | return 0; | |
340 | ||
341 | /* | |
342 | * If we are beyond our current deadline and we are still | |
343 | * executing, then we have already used some of the runtime of | |
344 | * the next instance. Thus, if we do not account that, we are | |
345 | * stealing bandwidth from the system at each deadline miss! | |
346 | */ | |
347 | if (dmiss) { | |
348 | dl_se->runtime = rorun ? dl_se->runtime : 0; | |
349 | dl_se->runtime -= rq_clock(rq) - dl_se->deadline; | |
350 | } | |
351 | ||
352 | return 1; | |
353 | } | |
354 | ||
355 | /* | |
356 | * Update the current task's runtime statistics (provided it is still | |
357 | * a -deadline task and has not been removed from the dl_rq). | |
358 | */ | |
359 | static void update_curr_dl(struct rq *rq) | |
360 | { | |
361 | struct task_struct *curr = rq->curr; | |
362 | struct sched_dl_entity *dl_se = &curr->dl; | |
363 | u64 delta_exec; | |
364 | ||
365 | if (!dl_task(curr) || !on_dl_rq(dl_se)) | |
366 | return; | |
367 | ||
368 | /* | |
369 | * Consumed budget is computed considering the time as | |
370 | * observed by schedulable tasks (excluding time spent | |
371 | * in hardirq context, etc.). Deadlines are instead | |
372 | * computed using hard walltime. This seems to be the more | |
373 | * natural solution, but the full ramifications of this | |
374 | * approach need further study. | |
375 | */ | |
376 | delta_exec = rq_clock_task(rq) - curr->se.exec_start; | |
377 | if (unlikely((s64)delta_exec < 0)) | |
378 | delta_exec = 0; | |
379 | ||
380 | schedstat_set(curr->se.statistics.exec_max, | |
381 | max(curr->se.statistics.exec_max, delta_exec)); | |
382 | ||
383 | curr->se.sum_exec_runtime += delta_exec; | |
384 | account_group_exec_runtime(curr, delta_exec); | |
385 | ||
386 | curr->se.exec_start = rq_clock_task(rq); | |
387 | cpuacct_charge(curr, delta_exec); | |
388 | ||
389 | dl_se->runtime -= delta_exec; | |
390 | if (dl_runtime_exceeded(rq, dl_se)) { | |
391 | __dequeue_task_dl(rq, curr, 0); | |
392 | if (likely(start_dl_timer(dl_se))) | |
393 | dl_se->dl_throttled = 1; | |
394 | else | |
395 | enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH); | |
396 | ||
397 | if (!is_leftmost(curr, &rq->dl)) | |
398 | resched_task(curr); | |
399 | } | |
400 | } | |
401 | ||
402 | static void __enqueue_dl_entity(struct sched_dl_entity *dl_se) | |
403 | { | |
404 | struct dl_rq *dl_rq = dl_rq_of_se(dl_se); | |
405 | struct rb_node **link = &dl_rq->rb_root.rb_node; | |
406 | struct rb_node *parent = NULL; | |
407 | struct sched_dl_entity *entry; | |
408 | int leftmost = 1; | |
409 | ||
410 | BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node)); | |
411 | ||
412 | while (*link) { | |
413 | parent = *link; | |
414 | entry = rb_entry(parent, struct sched_dl_entity, rb_node); | |
415 | if (dl_time_before(dl_se->deadline, entry->deadline)) | |
416 | link = &parent->rb_left; | |
417 | else { | |
418 | link = &parent->rb_right; | |
419 | leftmost = 0; | |
420 | } | |
421 | } | |
422 | ||
423 | if (leftmost) | |
424 | dl_rq->rb_leftmost = &dl_se->rb_node; | |
425 | ||
426 | rb_link_node(&dl_se->rb_node, parent, link); | |
427 | rb_insert_color(&dl_se->rb_node, &dl_rq->rb_root); | |
428 | ||
429 | dl_rq->dl_nr_running++; | |
430 | } | |
431 | ||
432 | static void __dequeue_dl_entity(struct sched_dl_entity *dl_se) | |
433 | { | |
434 | struct dl_rq *dl_rq = dl_rq_of_se(dl_se); | |
435 | ||
436 | if (RB_EMPTY_NODE(&dl_se->rb_node)) | |
437 | return; | |
438 | ||
439 | if (dl_rq->rb_leftmost == &dl_se->rb_node) { | |
440 | struct rb_node *next_node; | |
441 | ||
442 | next_node = rb_next(&dl_se->rb_node); | |
443 | dl_rq->rb_leftmost = next_node; | |
444 | } | |
445 | ||
446 | rb_erase(&dl_se->rb_node, &dl_rq->rb_root); | |
447 | RB_CLEAR_NODE(&dl_se->rb_node); | |
448 | ||
449 | dl_rq->dl_nr_running--; | |
450 | } | |
451 | ||
452 | static void | |
453 | enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags) | |
454 | { | |
455 | BUG_ON(on_dl_rq(dl_se)); | |
456 | ||
457 | /* | |
458 | * If this is a wakeup or a new instance, the scheduling | |
459 | * parameters of the task might need updating. Otherwise, | |
460 | * we want a replenishment of its runtime. | |
461 | */ | |
462 | if (!dl_se->dl_new && flags & ENQUEUE_REPLENISH) | |
463 | replenish_dl_entity(dl_se); | |
464 | else | |
465 | update_dl_entity(dl_se); | |
466 | ||
467 | __enqueue_dl_entity(dl_se); | |
468 | } | |
469 | ||
470 | static void dequeue_dl_entity(struct sched_dl_entity *dl_se) | |
471 | { | |
472 | __dequeue_dl_entity(dl_se); | |
473 | } | |
474 | ||
475 | static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags) | |
476 | { | |
477 | /* | |
478 | * If p is throttled, we do nothing. In fact, if it exhausted | |
479 | * its budget it needs a replenishment and, since it now is on | |
480 | * its rq, the bandwidth timer callback (which clearly has not | |
481 | * run yet) will take care of this. | |
482 | */ | |
483 | if (p->dl.dl_throttled) | |
484 | return; | |
485 | ||
486 | enqueue_dl_entity(&p->dl, flags); | |
487 | inc_nr_running(rq); | |
488 | } | |
489 | ||
490 | static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags) | |
491 | { | |
492 | dequeue_dl_entity(&p->dl); | |
493 | } | |
494 | ||
495 | static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags) | |
496 | { | |
497 | update_curr_dl(rq); | |
498 | __dequeue_task_dl(rq, p, flags); | |
499 | ||
500 | dec_nr_running(rq); | |
501 | } | |
502 | ||
503 | /* | |
504 | * Yield task semantic for -deadline tasks is: | |
505 | * | |
506 | * get off from the CPU until our next instance, with | |
507 | * a new runtime. This is of little use now, since we | |
508 | * don't have a bandwidth reclaiming mechanism. Anyway, | |
509 | * bandwidth reclaiming is planned for the future, and | |
510 | * yield_task_dl will indicate that some spare budget | |
511 | * is available for other task instances to use it. | |
512 | */ | |
513 | static void yield_task_dl(struct rq *rq) | |
514 | { | |
515 | struct task_struct *p = rq->curr; | |
516 | ||
517 | /* | |
518 | * We make the task go to sleep until its current deadline by | |
519 | * forcing its runtime to zero. This way, update_curr_dl() stops | |
520 | * it and the bandwidth timer will wake it up and will give it | |
521 | * new scheduling parameters (thanks to dl_new=1). | |
522 | */ | |
523 | if (p->dl.runtime > 0) { | |
524 | rq->curr->dl.dl_new = 1; | |
525 | p->dl.runtime = 0; | |
526 | } | |
527 | update_curr_dl(rq); | |
528 | } | |
529 | ||
530 | /* | |
531 | * Only called when both the current and waking task are -deadline | |
532 | * tasks. | |
533 | */ | |
534 | static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p, | |
535 | int flags) | |
536 | { | |
537 | if (dl_time_before(p->dl.deadline, rq->curr->dl.deadline)) | |
538 | resched_task(rq->curr); | |
539 | } | |
540 | ||
541 | #ifdef CONFIG_SCHED_HRTICK | |
542 | static void start_hrtick_dl(struct rq *rq, struct task_struct *p) | |
543 | { | |
544 | s64 delta = p->dl.dl_runtime - p->dl.runtime; | |
545 | ||
546 | if (delta > 10000) | |
547 | hrtick_start(rq, p->dl.runtime); | |
548 | } | |
549 | #endif | |
550 | ||
551 | static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq, | |
552 | struct dl_rq *dl_rq) | |
553 | { | |
554 | struct rb_node *left = dl_rq->rb_leftmost; | |
555 | ||
556 | if (!left) | |
557 | return NULL; | |
558 | ||
559 | return rb_entry(left, struct sched_dl_entity, rb_node); | |
560 | } | |
561 | ||
562 | struct task_struct *pick_next_task_dl(struct rq *rq) | |
563 | { | |
564 | struct sched_dl_entity *dl_se; | |
565 | struct task_struct *p; | |
566 | struct dl_rq *dl_rq; | |
567 | ||
568 | dl_rq = &rq->dl; | |
569 | ||
570 | if (unlikely(!dl_rq->dl_nr_running)) | |
571 | return NULL; | |
572 | ||
573 | dl_se = pick_next_dl_entity(rq, dl_rq); | |
574 | BUG_ON(!dl_se); | |
575 | ||
576 | p = dl_task_of(dl_se); | |
577 | p->se.exec_start = rq_clock_task(rq); | |
578 | #ifdef CONFIG_SCHED_HRTICK | |
579 | if (hrtick_enabled(rq)) | |
580 | start_hrtick_dl(rq, p); | |
581 | #endif | |
582 | return p; | |
583 | } | |
584 | ||
585 | static void put_prev_task_dl(struct rq *rq, struct task_struct *p) | |
586 | { | |
587 | update_curr_dl(rq); | |
588 | } | |
589 | ||
590 | static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued) | |
591 | { | |
592 | update_curr_dl(rq); | |
593 | ||
594 | #ifdef CONFIG_SCHED_HRTICK | |
595 | if (hrtick_enabled(rq) && queued && p->dl.runtime > 0) | |
596 | start_hrtick_dl(rq, p); | |
597 | #endif | |
598 | } | |
599 | ||
600 | static void task_fork_dl(struct task_struct *p) | |
601 | { | |
602 | /* | |
603 | * SCHED_DEADLINE tasks cannot fork and this is achieved through | |
604 | * sched_fork() | |
605 | */ | |
606 | } | |
607 | ||
608 | static void task_dead_dl(struct task_struct *p) | |
609 | { | |
610 | struct hrtimer *timer = &p->dl.dl_timer; | |
611 | ||
612 | if (hrtimer_active(timer)) | |
613 | hrtimer_try_to_cancel(timer); | |
614 | } | |
615 | ||
616 | static void set_curr_task_dl(struct rq *rq) | |
617 | { | |
618 | struct task_struct *p = rq->curr; | |
619 | ||
620 | p->se.exec_start = rq_clock_task(rq); | |
621 | } | |
622 | ||
623 | static void switched_from_dl(struct rq *rq, struct task_struct *p) | |
624 | { | |
625 | if (hrtimer_active(&p->dl.dl_timer)) | |
626 | hrtimer_try_to_cancel(&p->dl.dl_timer); | |
627 | } | |
628 | ||
629 | static void switched_to_dl(struct rq *rq, struct task_struct *p) | |
630 | { | |
631 | /* | |
632 | * If p is throttled, don't consider the possibility | |
633 | * of preempting rq->curr, the check will be done right | |
634 | * after its runtime will get replenished. | |
635 | */ | |
636 | if (unlikely(p->dl.dl_throttled)) | |
637 | return; | |
638 | ||
639 | if (p->on_rq || rq->curr != p) { | |
640 | if (task_has_dl_policy(rq->curr)) | |
641 | check_preempt_curr_dl(rq, p, 0); | |
642 | else | |
643 | resched_task(rq->curr); | |
644 | } | |
645 | } | |
646 | ||
647 | static void prio_changed_dl(struct rq *rq, struct task_struct *p, | |
648 | int oldprio) | |
649 | { | |
650 | switched_to_dl(rq, p); | |
651 | } | |
652 | ||
653 | #ifdef CONFIG_SMP | |
654 | static int | |
655 | select_task_rq_dl(struct task_struct *p, int prev_cpu, int sd_flag, int flags) | |
656 | { | |
657 | return task_cpu(p); | |
658 | } | |
659 | #endif | |
660 | ||
661 | const struct sched_class dl_sched_class = { | |
662 | .next = &rt_sched_class, | |
663 | .enqueue_task = enqueue_task_dl, | |
664 | .dequeue_task = dequeue_task_dl, | |
665 | .yield_task = yield_task_dl, | |
666 | ||
667 | .check_preempt_curr = check_preempt_curr_dl, | |
668 | ||
669 | .pick_next_task = pick_next_task_dl, | |
670 | .put_prev_task = put_prev_task_dl, | |
671 | ||
672 | #ifdef CONFIG_SMP | |
673 | .select_task_rq = select_task_rq_dl, | |
674 | #endif | |
675 | ||
676 | .set_curr_task = set_curr_task_dl, | |
677 | .task_tick = task_tick_dl, | |
678 | .task_fork = task_fork_dl, | |
679 | .task_dead = task_dead_dl, | |
680 | ||
681 | .prio_changed = prio_changed_dl, | |
682 | .switched_from = switched_from_dl, | |
683 | .switched_to = switched_to_dl, | |
684 | }; |