xref: /linux/kernel/sched/deadline.c (revision 2c1ed907520c50326b8f604907a8478b27881a2e)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Deadline Scheduling Class (SCHED_DEADLINE)
4  *
5  * Earliest Deadline First (EDF) + Constant Bandwidth Server (CBS).
6  *
7  * Tasks that periodically executes their instances for less than their
8  * runtime won't miss any of their deadlines.
9  * Tasks that are not periodic or sporadic or that tries to execute more
10  * than their reserved bandwidth will be slowed down (and may potentially
11  * miss some of their deadlines), and won't affect any other task.
12  *
13  * Copyright (C) 2012 Dario Faggioli <raistlin@linux.it>,
14  *                    Juri Lelli <juri.lelli@gmail.com>,
15  *                    Michael Trimarchi <michael@amarulasolutions.com>,
16  *                    Fabio Checconi <fchecconi@gmail.com>
17  */
18 
19 #include <linux/cpuset.h>
20 
21 /*
22  * Default limits for DL period; on the top end we guard against small util
23  * tasks still getting ridiculously long effective runtimes, on the bottom end we
24  * guard against timer DoS.
25  */
26 static unsigned int sysctl_sched_dl_period_max = 1 << 22; /* ~4 seconds */
27 static unsigned int sysctl_sched_dl_period_min = 100;     /* 100 us */
28 #ifdef CONFIG_SYSCTL
29 static const struct ctl_table sched_dl_sysctls[] = {
30 	{
31 		.procname       = "sched_deadline_period_max_us",
32 		.data           = &sysctl_sched_dl_period_max,
33 		.maxlen         = sizeof(unsigned int),
34 		.mode           = 0644,
35 		.proc_handler   = proc_douintvec_minmax,
36 		.extra1         = (void *)&sysctl_sched_dl_period_min,
37 	},
38 	{
39 		.procname       = "sched_deadline_period_min_us",
40 		.data           = &sysctl_sched_dl_period_min,
41 		.maxlen         = sizeof(unsigned int),
42 		.mode           = 0644,
43 		.proc_handler   = proc_douintvec_minmax,
44 		.extra2         = (void *)&sysctl_sched_dl_period_max,
45 	},
46 };
47 
sched_dl_sysctl_init(void)48 static int __init sched_dl_sysctl_init(void)
49 {
50 	register_sysctl_init("kernel", sched_dl_sysctls);
51 	return 0;
52 }
53 late_initcall(sched_dl_sysctl_init);
54 #endif
55 
dl_server(struct sched_dl_entity * dl_se)56 static bool dl_server(struct sched_dl_entity *dl_se)
57 {
58 	return dl_se->dl_server;
59 }
60 
dl_task_of(struct sched_dl_entity * dl_se)61 static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
62 {
63 	BUG_ON(dl_server(dl_se));
64 	return container_of(dl_se, struct task_struct, dl);
65 }
66 
rq_of_dl_rq(struct dl_rq * dl_rq)67 static inline struct rq *rq_of_dl_rq(struct dl_rq *dl_rq)
68 {
69 	return container_of(dl_rq, struct rq, dl);
70 }
71 
rq_of_dl_se(struct sched_dl_entity * dl_se)72 static inline struct rq *rq_of_dl_se(struct sched_dl_entity *dl_se)
73 {
74 	struct rq *rq = dl_se->rq;
75 
76 	if (!dl_server(dl_se))
77 		rq = task_rq(dl_task_of(dl_se));
78 
79 	return rq;
80 }
81 
dl_rq_of_se(struct sched_dl_entity * dl_se)82 static inline struct dl_rq *dl_rq_of_se(struct sched_dl_entity *dl_se)
83 {
84 	return &rq_of_dl_se(dl_se)->dl;
85 }
86 
on_dl_rq(struct sched_dl_entity * dl_se)87 static inline int on_dl_rq(struct sched_dl_entity *dl_se)
88 {
89 	return !RB_EMPTY_NODE(&dl_se->rb_node);
90 }
91 
92 #ifdef CONFIG_RT_MUTEXES
pi_of(struct sched_dl_entity * dl_se)93 static inline struct sched_dl_entity *pi_of(struct sched_dl_entity *dl_se)
94 {
95 	return dl_se->pi_se;
96 }
97 
is_dl_boosted(struct sched_dl_entity * dl_se)98 static inline bool is_dl_boosted(struct sched_dl_entity *dl_se)
99 {
100 	return pi_of(dl_se) != dl_se;
101 }
102 #else
pi_of(struct sched_dl_entity * dl_se)103 static inline struct sched_dl_entity *pi_of(struct sched_dl_entity *dl_se)
104 {
105 	return dl_se;
106 }
107 
is_dl_boosted(struct sched_dl_entity * dl_se)108 static inline bool is_dl_boosted(struct sched_dl_entity *dl_se)
109 {
110 	return false;
111 }
112 #endif
113 
114 #ifdef CONFIG_SMP
dl_bw_of(int i)115 static inline struct dl_bw *dl_bw_of(int i)
116 {
117 	RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
118 			 "sched RCU must be held");
119 	return &cpu_rq(i)->rd->dl_bw;
120 }
121 
dl_bw_cpus(int i)122 static inline int dl_bw_cpus(int i)
123 {
124 	struct root_domain *rd = cpu_rq(i)->rd;
125 	int cpus;
126 
127 	RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
128 			 "sched RCU must be held");
129 
130 	if (cpumask_subset(rd->span, cpu_active_mask))
131 		return cpumask_weight(rd->span);
132 
133 	cpus = 0;
134 
135 	for_each_cpu_and(i, rd->span, cpu_active_mask)
136 		cpus++;
137 
138 	return cpus;
139 }
140 
__dl_bw_capacity(const struct cpumask * mask)141 static inline unsigned long __dl_bw_capacity(const struct cpumask *mask)
142 {
143 	unsigned long cap = 0;
144 	int i;
145 
146 	for_each_cpu_and(i, mask, cpu_active_mask)
147 		cap += arch_scale_cpu_capacity(i);
148 
149 	return cap;
150 }
151 
152 /*
153  * XXX Fix: If 'rq->rd == def_root_domain' perform AC against capacity
154  * of the CPU the task is running on rather rd's \Sum CPU capacity.
155  */
dl_bw_capacity(int i)156 static inline unsigned long dl_bw_capacity(int i)
157 {
158 	if (!sched_asym_cpucap_active() &&
159 	    arch_scale_cpu_capacity(i) == SCHED_CAPACITY_SCALE) {
160 		return dl_bw_cpus(i) << SCHED_CAPACITY_SHIFT;
161 	} else {
162 		RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
163 				 "sched RCU must be held");
164 
165 		return __dl_bw_capacity(cpu_rq(i)->rd->span);
166 	}
167 }
168 
dl_bw_visited(int cpu,u64 gen)169 static inline bool dl_bw_visited(int cpu, u64 gen)
170 {
171 	struct root_domain *rd = cpu_rq(cpu)->rd;
172 
173 	if (rd->visit_gen == gen)
174 		return true;
175 
176 	rd->visit_gen = gen;
177 	return false;
178 }
179 
180 static inline
__dl_update(struct dl_bw * dl_b,s64 bw)181 void __dl_update(struct dl_bw *dl_b, s64 bw)
182 {
183 	struct root_domain *rd = container_of(dl_b, struct root_domain, dl_bw);
184 	int i;
185 
186 	RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
187 			 "sched RCU must be held");
188 	for_each_cpu_and(i, rd->span, cpu_active_mask) {
189 		struct rq *rq = cpu_rq(i);
190 
191 		rq->dl.extra_bw += bw;
192 	}
193 }
194 #else
dl_bw_of(int i)195 static inline struct dl_bw *dl_bw_of(int i)
196 {
197 	return &cpu_rq(i)->dl.dl_bw;
198 }
199 
dl_bw_cpus(int i)200 static inline int dl_bw_cpus(int i)
201 {
202 	return 1;
203 }
204 
dl_bw_capacity(int i)205 static inline unsigned long dl_bw_capacity(int i)
206 {
207 	return SCHED_CAPACITY_SCALE;
208 }
209 
dl_bw_visited(int cpu,u64 gen)210 static inline bool dl_bw_visited(int cpu, u64 gen)
211 {
212 	return false;
213 }
214 
215 static inline
__dl_update(struct dl_bw * dl_b,s64 bw)216 void __dl_update(struct dl_bw *dl_b, s64 bw)
217 {
218 	struct dl_rq *dl = container_of(dl_b, struct dl_rq, dl_bw);
219 
220 	dl->extra_bw += bw;
221 }
222 #endif
223 
224 static inline
__dl_sub(struct dl_bw * dl_b,u64 tsk_bw,int cpus)225 void __dl_sub(struct dl_bw *dl_b, u64 tsk_bw, int cpus)
226 {
227 	dl_b->total_bw -= tsk_bw;
228 	__dl_update(dl_b, (s32)tsk_bw / cpus);
229 }
230 
231 static inline
__dl_add(struct dl_bw * dl_b,u64 tsk_bw,int cpus)232 void __dl_add(struct dl_bw *dl_b, u64 tsk_bw, int cpus)
233 {
234 	dl_b->total_bw += tsk_bw;
235 	__dl_update(dl_b, -((s32)tsk_bw / cpus));
236 }
237 
238 static inline bool
__dl_overflow(struct dl_bw * dl_b,unsigned long cap,u64 old_bw,u64 new_bw)239 __dl_overflow(struct dl_bw *dl_b, unsigned long cap, u64 old_bw, u64 new_bw)
240 {
241 	return dl_b->bw != -1 &&
242 	       cap_scale(dl_b->bw, cap) < dl_b->total_bw - old_bw + new_bw;
243 }
244 
245 static inline
__add_running_bw(u64 dl_bw,struct dl_rq * dl_rq)246 void __add_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
247 {
248 	u64 old = dl_rq->running_bw;
249 
250 	lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
251 	dl_rq->running_bw += dl_bw;
252 	SCHED_WARN_ON(dl_rq->running_bw < old); /* overflow */
253 	SCHED_WARN_ON(dl_rq->running_bw > dl_rq->this_bw);
254 	/* kick cpufreq (see the comment in kernel/sched/sched.h). */
255 	cpufreq_update_util(rq_of_dl_rq(dl_rq), 0);
256 }
257 
258 static inline
__sub_running_bw(u64 dl_bw,struct dl_rq * dl_rq)259 void __sub_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
260 {
261 	u64 old = dl_rq->running_bw;
262 
263 	lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
264 	dl_rq->running_bw -= dl_bw;
265 	SCHED_WARN_ON(dl_rq->running_bw > old); /* underflow */
266 	if (dl_rq->running_bw > old)
267 		dl_rq->running_bw = 0;
268 	/* kick cpufreq (see the comment in kernel/sched/sched.h). */
269 	cpufreq_update_util(rq_of_dl_rq(dl_rq), 0);
270 }
271 
272 static inline
__add_rq_bw(u64 dl_bw,struct dl_rq * dl_rq)273 void __add_rq_bw(u64 dl_bw, struct dl_rq *dl_rq)
274 {
275 	u64 old = dl_rq->this_bw;
276 
277 	lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
278 	dl_rq->this_bw += dl_bw;
279 	SCHED_WARN_ON(dl_rq->this_bw < old); /* overflow */
280 }
281 
282 static inline
__sub_rq_bw(u64 dl_bw,struct dl_rq * dl_rq)283 void __sub_rq_bw(u64 dl_bw, struct dl_rq *dl_rq)
284 {
285 	u64 old = dl_rq->this_bw;
286 
287 	lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
288 	dl_rq->this_bw -= dl_bw;
289 	SCHED_WARN_ON(dl_rq->this_bw > old); /* underflow */
290 	if (dl_rq->this_bw > old)
291 		dl_rq->this_bw = 0;
292 	SCHED_WARN_ON(dl_rq->running_bw > dl_rq->this_bw);
293 }
294 
295 static inline
add_rq_bw(struct sched_dl_entity * dl_se,struct dl_rq * dl_rq)296 void add_rq_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
297 {
298 	if (!dl_entity_is_special(dl_se))
299 		__add_rq_bw(dl_se->dl_bw, dl_rq);
300 }
301 
302 static inline
sub_rq_bw(struct sched_dl_entity * dl_se,struct dl_rq * dl_rq)303 void sub_rq_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
304 {
305 	if (!dl_entity_is_special(dl_se))
306 		__sub_rq_bw(dl_se->dl_bw, dl_rq);
307 }
308 
309 static inline
add_running_bw(struct sched_dl_entity * dl_se,struct dl_rq * dl_rq)310 void add_running_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
311 {
312 	if (!dl_entity_is_special(dl_se))
313 		__add_running_bw(dl_se->dl_bw, dl_rq);
314 }
315 
316 static inline
sub_running_bw(struct sched_dl_entity * dl_se,struct dl_rq * dl_rq)317 void sub_running_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
318 {
319 	if (!dl_entity_is_special(dl_se))
320 		__sub_running_bw(dl_se->dl_bw, dl_rq);
321 }
322 
dl_rq_change_utilization(struct rq * rq,struct sched_dl_entity * dl_se,u64 new_bw)323 static void dl_rq_change_utilization(struct rq *rq, struct sched_dl_entity *dl_se, u64 new_bw)
324 {
325 	if (dl_se->dl_non_contending) {
326 		sub_running_bw(dl_se, &rq->dl);
327 		dl_se->dl_non_contending = 0;
328 
329 		/*
330 		 * If the timer handler is currently running and the
331 		 * timer cannot be canceled, inactive_task_timer()
332 		 * will see that dl_not_contending is not set, and
333 		 * will not touch the rq's active utilization,
334 		 * so we are still safe.
335 		 */
336 		if (hrtimer_try_to_cancel(&dl_se->inactive_timer) == 1) {
337 			if (!dl_server(dl_se))
338 				put_task_struct(dl_task_of(dl_se));
339 		}
340 	}
341 	__sub_rq_bw(dl_se->dl_bw, &rq->dl);
342 	__add_rq_bw(new_bw, &rq->dl);
343 }
344 
345 static __always_inline
cancel_dl_timer(struct sched_dl_entity * dl_se,struct hrtimer * timer)346 void cancel_dl_timer(struct sched_dl_entity *dl_se, struct hrtimer *timer)
347 {
348 	/*
349 	 * If the timer callback was running (hrtimer_try_to_cancel == -1),
350 	 * it will eventually call put_task_struct().
351 	 */
352 	if (hrtimer_try_to_cancel(timer) == 1 && !dl_server(dl_se))
353 		put_task_struct(dl_task_of(dl_se));
354 }
355 
356 static __always_inline
cancel_replenish_timer(struct sched_dl_entity * dl_se)357 void cancel_replenish_timer(struct sched_dl_entity *dl_se)
358 {
359 	cancel_dl_timer(dl_se, &dl_se->dl_timer);
360 }
361 
362 static __always_inline
cancel_inactive_timer(struct sched_dl_entity * dl_se)363 void cancel_inactive_timer(struct sched_dl_entity *dl_se)
364 {
365 	cancel_dl_timer(dl_se, &dl_se->inactive_timer);
366 }
367 
dl_change_utilization(struct task_struct * p,u64 new_bw)368 static void dl_change_utilization(struct task_struct *p, u64 new_bw)
369 {
370 	WARN_ON_ONCE(p->dl.flags & SCHED_FLAG_SUGOV);
371 
372 	if (task_on_rq_queued(p))
373 		return;
374 
375 	dl_rq_change_utilization(task_rq(p), &p->dl, new_bw);
376 }
377 
378 static void __dl_clear_params(struct sched_dl_entity *dl_se);
379 
380 /*
381  * The utilization of a task cannot be immediately removed from
382  * the rq active utilization (running_bw) when the task blocks.
383  * Instead, we have to wait for the so called "0-lag time".
384  *
385  * If a task blocks before the "0-lag time", a timer (the inactive
386  * timer) is armed, and running_bw is decreased when the timer
387  * fires.
388  *
389  * If the task wakes up again before the inactive timer fires,
390  * the timer is canceled, whereas if the task wakes up after the
391  * inactive timer fired (and running_bw has been decreased) the
392  * task's utilization has to be added to running_bw again.
393  * A flag in the deadline scheduling entity (dl_non_contending)
394  * is used to avoid race conditions between the inactive timer handler
395  * and task wakeups.
396  *
397  * The following diagram shows how running_bw is updated. A task is
398  * "ACTIVE" when its utilization contributes to running_bw; an
399  * "ACTIVE contending" task is in the TASK_RUNNING state, while an
400  * "ACTIVE non contending" task is a blocked task for which the "0-lag time"
401  * has not passed yet. An "INACTIVE" task is a task for which the "0-lag"
402  * time already passed, which does not contribute to running_bw anymore.
403  *                              +------------------+
404  *             wakeup           |    ACTIVE        |
405  *          +------------------>+   contending     |
406  *          | add_running_bw    |                  |
407  *          |                   +----+------+------+
408  *          |                        |      ^
409  *          |                dequeue |      |
410  * +--------+-------+                |      |
411  * |                |   t >= 0-lag   |      | wakeup
412  * |    INACTIVE    |<---------------+      |
413  * |                | sub_running_bw |      |
414  * +--------+-------+                |      |
415  *          ^                        |      |
416  *          |              t < 0-lag |      |
417  *          |                        |      |
418  *          |                        V      |
419  *          |                   +----+------+------+
420  *          | sub_running_bw    |    ACTIVE        |
421  *          +-------------------+                  |
422  *            inactive timer    |  non contending  |
423  *            fired             +------------------+
424  *
425  * The task_non_contending() function is invoked when a task
426  * blocks, and checks if the 0-lag time already passed or
427  * not (in the first case, it directly updates running_bw;
428  * in the second case, it arms the inactive timer).
429  *
430  * The task_contending() function is invoked when a task wakes
431  * up, and checks if the task is still in the "ACTIVE non contending"
432  * state or not (in the second case, it updates running_bw).
433  */
task_non_contending(struct sched_dl_entity * dl_se)434 static void task_non_contending(struct sched_dl_entity *dl_se)
435 {
436 	struct hrtimer *timer = &dl_se->inactive_timer;
437 	struct rq *rq = rq_of_dl_se(dl_se);
438 	struct dl_rq *dl_rq = &rq->dl;
439 	s64 zerolag_time;
440 
441 	/*
442 	 * If this is a non-deadline task that has been boosted,
443 	 * do nothing
444 	 */
445 	if (dl_se->dl_runtime == 0)
446 		return;
447 
448 	if (dl_entity_is_special(dl_se))
449 		return;
450 
451 	WARN_ON(dl_se->dl_non_contending);
452 
453 	zerolag_time = dl_se->deadline -
454 		 div64_long((dl_se->runtime * dl_se->dl_period),
455 			dl_se->dl_runtime);
456 
457 	/*
458 	 * Using relative times instead of the absolute "0-lag time"
459 	 * allows to simplify the code
460 	 */
461 	zerolag_time -= rq_clock(rq);
462 
463 	/*
464 	 * If the "0-lag time" already passed, decrease the active
465 	 * utilization now, instead of starting a timer
466 	 */
467 	if ((zerolag_time < 0) || hrtimer_active(&dl_se->inactive_timer)) {
468 		if (dl_server(dl_se)) {
469 			sub_running_bw(dl_se, dl_rq);
470 		} else {
471 			struct task_struct *p = dl_task_of(dl_se);
472 
473 			if (dl_task(p))
474 				sub_running_bw(dl_se, dl_rq);
475 
476 			if (!dl_task(p) || READ_ONCE(p->__state) == TASK_DEAD) {
477 				struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
478 
479 				if (READ_ONCE(p->__state) == TASK_DEAD)
480 					sub_rq_bw(dl_se, &rq->dl);
481 				raw_spin_lock(&dl_b->lock);
482 				__dl_sub(dl_b, dl_se->dl_bw, dl_bw_cpus(task_cpu(p)));
483 				raw_spin_unlock(&dl_b->lock);
484 				__dl_clear_params(dl_se);
485 			}
486 		}
487 
488 		return;
489 	}
490 
491 	dl_se->dl_non_contending = 1;
492 	if (!dl_server(dl_se))
493 		get_task_struct(dl_task_of(dl_se));
494 
495 	hrtimer_start(timer, ns_to_ktime(zerolag_time), HRTIMER_MODE_REL_HARD);
496 }
497 
task_contending(struct sched_dl_entity * dl_se,int flags)498 static void task_contending(struct sched_dl_entity *dl_se, int flags)
499 {
500 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
501 
502 	/*
503 	 * If this is a non-deadline task that has been boosted,
504 	 * do nothing
505 	 */
506 	if (dl_se->dl_runtime == 0)
507 		return;
508 
509 	if (flags & ENQUEUE_MIGRATED)
510 		add_rq_bw(dl_se, dl_rq);
511 
512 	if (dl_se->dl_non_contending) {
513 		dl_se->dl_non_contending = 0;
514 		/*
515 		 * If the timer handler is currently running and the
516 		 * timer cannot be canceled, inactive_task_timer()
517 		 * will see that dl_not_contending is not set, and
518 		 * will not touch the rq's active utilization,
519 		 * so we are still safe.
520 		 */
521 		cancel_inactive_timer(dl_se);
522 	} else {
523 		/*
524 		 * Since "dl_non_contending" is not set, the
525 		 * task's utilization has already been removed from
526 		 * active utilization (either when the task blocked,
527 		 * when the "inactive timer" fired).
528 		 * So, add it back.
529 		 */
530 		add_running_bw(dl_se, dl_rq);
531 	}
532 }
533 
is_leftmost(struct sched_dl_entity * dl_se,struct dl_rq * dl_rq)534 static inline int is_leftmost(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
535 {
536 	return rb_first_cached(&dl_rq->root) == &dl_se->rb_node;
537 }
538 
539 static void init_dl_rq_bw_ratio(struct dl_rq *dl_rq);
540 
init_dl_bw(struct dl_bw * dl_b)541 void init_dl_bw(struct dl_bw *dl_b)
542 {
543 	raw_spin_lock_init(&dl_b->lock);
544 	if (global_rt_runtime() == RUNTIME_INF)
545 		dl_b->bw = -1;
546 	else
547 		dl_b->bw = to_ratio(global_rt_period(), global_rt_runtime());
548 	dl_b->total_bw = 0;
549 }
550 
init_dl_rq(struct dl_rq * dl_rq)551 void init_dl_rq(struct dl_rq *dl_rq)
552 {
553 	dl_rq->root = RB_ROOT_CACHED;
554 
555 #ifdef CONFIG_SMP
556 	/* zero means no -deadline tasks */
557 	dl_rq->earliest_dl.curr = dl_rq->earliest_dl.next = 0;
558 
559 	dl_rq->overloaded = 0;
560 	dl_rq->pushable_dl_tasks_root = RB_ROOT_CACHED;
561 #else
562 	init_dl_bw(&dl_rq->dl_bw);
563 #endif
564 
565 	dl_rq->running_bw = 0;
566 	dl_rq->this_bw = 0;
567 	init_dl_rq_bw_ratio(dl_rq);
568 }
569 
570 #ifdef CONFIG_SMP
571 
dl_overloaded(struct rq * rq)572 static inline int dl_overloaded(struct rq *rq)
573 {
574 	return atomic_read(&rq->rd->dlo_count);
575 }
576 
dl_set_overload(struct rq * rq)577 static inline void dl_set_overload(struct rq *rq)
578 {
579 	if (!rq->online)
580 		return;
581 
582 	cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask);
583 	/*
584 	 * Must be visible before the overload count is
585 	 * set (as in sched_rt.c).
586 	 *
587 	 * Matched by the barrier in pull_dl_task().
588 	 */
589 	smp_wmb();
590 	atomic_inc(&rq->rd->dlo_count);
591 }
592 
dl_clear_overload(struct rq * rq)593 static inline void dl_clear_overload(struct rq *rq)
594 {
595 	if (!rq->online)
596 		return;
597 
598 	atomic_dec(&rq->rd->dlo_count);
599 	cpumask_clear_cpu(rq->cpu, rq->rd->dlo_mask);
600 }
601 
602 #define __node_2_pdl(node) \
603 	rb_entry((node), struct task_struct, pushable_dl_tasks)
604 
__pushable_less(struct rb_node * a,const struct rb_node * b)605 static inline bool __pushable_less(struct rb_node *a, const struct rb_node *b)
606 {
607 	return dl_entity_preempt(&__node_2_pdl(a)->dl, &__node_2_pdl(b)->dl);
608 }
609 
has_pushable_dl_tasks(struct rq * rq)610 static inline int has_pushable_dl_tasks(struct rq *rq)
611 {
612 	return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root.rb_root);
613 }
614 
615 /*
616  * The list of pushable -deadline task is not a plist, like in
617  * sched_rt.c, it is an rb-tree with tasks ordered by deadline.
618  */
enqueue_pushable_dl_task(struct rq * rq,struct task_struct * p)619 static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
620 {
621 	struct rb_node *leftmost;
622 
623 	WARN_ON_ONCE(!RB_EMPTY_NODE(&p->pushable_dl_tasks));
624 
625 	leftmost = rb_add_cached(&p->pushable_dl_tasks,
626 				 &rq->dl.pushable_dl_tasks_root,
627 				 __pushable_less);
628 	if (leftmost)
629 		rq->dl.earliest_dl.next = p->dl.deadline;
630 
631 	if (!rq->dl.overloaded) {
632 		dl_set_overload(rq);
633 		rq->dl.overloaded = 1;
634 	}
635 }
636 
dequeue_pushable_dl_task(struct rq * rq,struct task_struct * p)637 static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
638 {
639 	struct dl_rq *dl_rq = &rq->dl;
640 	struct rb_root_cached *root = &dl_rq->pushable_dl_tasks_root;
641 	struct rb_node *leftmost;
642 
643 	if (RB_EMPTY_NODE(&p->pushable_dl_tasks))
644 		return;
645 
646 	leftmost = rb_erase_cached(&p->pushable_dl_tasks, root);
647 	if (leftmost)
648 		dl_rq->earliest_dl.next = __node_2_pdl(leftmost)->dl.deadline;
649 
650 	RB_CLEAR_NODE(&p->pushable_dl_tasks);
651 
652 	if (!has_pushable_dl_tasks(rq) && rq->dl.overloaded) {
653 		dl_clear_overload(rq);
654 		rq->dl.overloaded = 0;
655 	}
656 }
657 
658 static int push_dl_task(struct rq *rq);
659 
need_pull_dl_task(struct rq * rq,struct task_struct * prev)660 static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
661 {
662 	return rq->online && dl_task(prev);
663 }
664 
665 static DEFINE_PER_CPU(struct balance_callback, dl_push_head);
666 static DEFINE_PER_CPU(struct balance_callback, dl_pull_head);
667 
668 static void push_dl_tasks(struct rq *);
669 static void pull_dl_task(struct rq *);
670 
deadline_queue_push_tasks(struct rq * rq)671 static inline void deadline_queue_push_tasks(struct rq *rq)
672 {
673 	if (!has_pushable_dl_tasks(rq))
674 		return;
675 
676 	queue_balance_callback(rq, &per_cpu(dl_push_head, rq->cpu), push_dl_tasks);
677 }
678 
deadline_queue_pull_task(struct rq * rq)679 static inline void deadline_queue_pull_task(struct rq *rq)
680 {
681 	queue_balance_callback(rq, &per_cpu(dl_pull_head, rq->cpu), pull_dl_task);
682 }
683 
684 static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq);
685 
dl_task_offline_migration(struct rq * rq,struct task_struct * p)686 static struct rq *dl_task_offline_migration(struct rq *rq, struct task_struct *p)
687 {
688 	struct rq *later_rq = NULL;
689 	struct dl_bw *dl_b;
690 
691 	later_rq = find_lock_later_rq(p, rq);
692 	if (!later_rq) {
693 		int cpu;
694 
695 		/*
696 		 * If we cannot preempt any rq, fall back to pick any
697 		 * online CPU:
698 		 */
699 		cpu = cpumask_any_and(cpu_active_mask, p->cpus_ptr);
700 		if (cpu >= nr_cpu_ids) {
701 			/*
702 			 * Failed to find any suitable CPU.
703 			 * The task will never come back!
704 			 */
705 			WARN_ON_ONCE(dl_bandwidth_enabled());
706 
707 			/*
708 			 * If admission control is disabled we
709 			 * try a little harder to let the task
710 			 * run.
711 			 */
712 			cpu = cpumask_any(cpu_active_mask);
713 		}
714 		later_rq = cpu_rq(cpu);
715 		double_lock_balance(rq, later_rq);
716 	}
717 
718 	if (p->dl.dl_non_contending || p->dl.dl_throttled) {
719 		/*
720 		 * Inactive timer is armed (or callback is running, but
721 		 * waiting for us to release rq locks). In any case, when it
722 		 * will fire (or continue), it will see running_bw of this
723 		 * task migrated to later_rq (and correctly handle it).
724 		 */
725 		sub_running_bw(&p->dl, &rq->dl);
726 		sub_rq_bw(&p->dl, &rq->dl);
727 
728 		add_rq_bw(&p->dl, &later_rq->dl);
729 		add_running_bw(&p->dl, &later_rq->dl);
730 	} else {
731 		sub_rq_bw(&p->dl, &rq->dl);
732 		add_rq_bw(&p->dl, &later_rq->dl);
733 	}
734 
735 	/*
736 	 * And we finally need to fix up root_domain(s) bandwidth accounting,
737 	 * since p is still hanging out in the old (now moved to default) root
738 	 * domain.
739 	 */
740 	dl_b = &rq->rd->dl_bw;
741 	raw_spin_lock(&dl_b->lock);
742 	__dl_sub(dl_b, p->dl.dl_bw, cpumask_weight(rq->rd->span));
743 	raw_spin_unlock(&dl_b->lock);
744 
745 	dl_b = &later_rq->rd->dl_bw;
746 	raw_spin_lock(&dl_b->lock);
747 	__dl_add(dl_b, p->dl.dl_bw, cpumask_weight(later_rq->rd->span));
748 	raw_spin_unlock(&dl_b->lock);
749 
750 	set_task_cpu(p, later_rq->cpu);
751 	double_unlock_balance(later_rq, rq);
752 
753 	return later_rq;
754 }
755 
756 #else
757 
758 static inline
enqueue_pushable_dl_task(struct rq * rq,struct task_struct * p)759 void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
760 {
761 }
762 
763 static inline
dequeue_pushable_dl_task(struct rq * rq,struct task_struct * p)764 void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
765 {
766 }
767 
768 static inline
inc_dl_migration(struct sched_dl_entity * dl_se,struct dl_rq * dl_rq)769 void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
770 {
771 }
772 
773 static inline
dec_dl_migration(struct sched_dl_entity * dl_se,struct dl_rq * dl_rq)774 void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
775 {
776 }
777 
deadline_queue_push_tasks(struct rq * rq)778 static inline void deadline_queue_push_tasks(struct rq *rq)
779 {
780 }
781 
deadline_queue_pull_task(struct rq * rq)782 static inline void deadline_queue_pull_task(struct rq *rq)
783 {
784 }
785 #endif /* CONFIG_SMP */
786 
787 static void
788 enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags);
789 static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags);
790 static void dequeue_dl_entity(struct sched_dl_entity *dl_se, int flags);
791 static void wakeup_preempt_dl(struct rq *rq, struct task_struct *p, int flags);
792 
replenish_dl_new_period(struct sched_dl_entity * dl_se,struct rq * rq)793 static inline void replenish_dl_new_period(struct sched_dl_entity *dl_se,
794 					    struct rq *rq)
795 {
796 	/* for non-boosted task, pi_of(dl_se) == dl_se */
797 	dl_se->deadline = rq_clock(rq) + pi_of(dl_se)->dl_deadline;
798 	dl_se->runtime = pi_of(dl_se)->dl_runtime;
799 
800 	/*
801 	 * If it is a deferred reservation, and the server
802 	 * is not handling an starvation case, defer it.
803 	 */
804 	if (dl_se->dl_defer && !dl_se->dl_defer_running) {
805 		dl_se->dl_throttled = 1;
806 		dl_se->dl_defer_armed = 1;
807 	}
808 }
809 
810 /*
811  * We are being explicitly informed that a new instance is starting,
812  * and this means that:
813  *  - the absolute deadline of the entity has to be placed at
814  *    current time + relative deadline;
815  *  - the runtime of the entity has to be set to the maximum value.
816  *
817  * The capability of specifying such event is useful whenever a -deadline
818  * entity wants to (try to!) synchronize its behaviour with the scheduler's
819  * one, and to (try to!) reconcile itself with its own scheduling
820  * parameters.
821  */
setup_new_dl_entity(struct sched_dl_entity * dl_se)822 static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
823 {
824 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
825 	struct rq *rq = rq_of_dl_rq(dl_rq);
826 
827 	WARN_ON(is_dl_boosted(dl_se));
828 	WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
829 
830 	/*
831 	 * We are racing with the deadline timer. So, do nothing because
832 	 * the deadline timer handler will take care of properly recharging
833 	 * the runtime and postponing the deadline
834 	 */
835 	if (dl_se->dl_throttled)
836 		return;
837 
838 	/*
839 	 * We use the regular wall clock time to set deadlines in the
840 	 * future; in fact, we must consider execution overheads (time
841 	 * spent on hardirq context, etc.).
842 	 */
843 	replenish_dl_new_period(dl_se, rq);
844 }
845 
846 static int start_dl_timer(struct sched_dl_entity *dl_se);
847 static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t);
848 
849 /*
850  * Pure Earliest Deadline First (EDF) scheduling does not deal with the
851  * possibility of a entity lasting more than what it declared, and thus
852  * exhausting its runtime.
853  *
854  * Here we are interested in making runtime overrun possible, but we do
855  * not want a entity which is misbehaving to affect the scheduling of all
856  * other entities.
857  * Therefore, a budgeting strategy called Constant Bandwidth Server (CBS)
858  * is used, in order to confine each entity within its own bandwidth.
859  *
860  * This function deals exactly with that, and ensures that when the runtime
861  * of a entity is replenished, its deadline is also postponed. That ensures
862  * the overrunning entity can't interfere with other entity in the system and
863  * can't make them miss their deadlines. Reasons why this kind of overruns
864  * could happen are, typically, a entity voluntarily trying to overcome its
865  * runtime, or it just underestimated it during sched_setattr().
866  */
replenish_dl_entity(struct sched_dl_entity * dl_se)867 static void replenish_dl_entity(struct sched_dl_entity *dl_se)
868 {
869 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
870 	struct rq *rq = rq_of_dl_rq(dl_rq);
871 
872 	WARN_ON_ONCE(pi_of(dl_se)->dl_runtime <= 0);
873 
874 	/*
875 	 * This could be the case for a !-dl task that is boosted.
876 	 * Just go with full inherited parameters.
877 	 *
878 	 * Or, it could be the case of a deferred reservation that
879 	 * was not able to consume its runtime in background and
880 	 * reached this point with current u > U.
881 	 *
882 	 * In both cases, set a new period.
883 	 */
884 	if (dl_se->dl_deadline == 0 ||
885 	    (dl_se->dl_defer_armed && dl_entity_overflow(dl_se, rq_clock(rq)))) {
886 		dl_se->deadline = rq_clock(rq) + pi_of(dl_se)->dl_deadline;
887 		dl_se->runtime = pi_of(dl_se)->dl_runtime;
888 	}
889 
890 	if (dl_se->dl_yielded && dl_se->runtime > 0)
891 		dl_se->runtime = 0;
892 
893 	/*
894 	 * We keep moving the deadline away until we get some
895 	 * available runtime for the entity. This ensures correct
896 	 * handling of situations where the runtime overrun is
897 	 * arbitrary large.
898 	 */
899 	while (dl_se->runtime <= 0) {
900 		dl_se->deadline += pi_of(dl_se)->dl_period;
901 		dl_se->runtime += pi_of(dl_se)->dl_runtime;
902 	}
903 
904 	/*
905 	 * At this point, the deadline really should be "in
906 	 * the future" with respect to rq->clock. If it's
907 	 * not, we are, for some reason, lagging too much!
908 	 * Anyway, after having warn userspace abut that,
909 	 * we still try to keep the things running by
910 	 * resetting the deadline and the budget of the
911 	 * entity.
912 	 */
913 	if (dl_time_before(dl_se->deadline, rq_clock(rq))) {
914 		printk_deferred_once("sched: DL replenish lagged too much\n");
915 		replenish_dl_new_period(dl_se, rq);
916 	}
917 
918 	if (dl_se->dl_yielded)
919 		dl_se->dl_yielded = 0;
920 	if (dl_se->dl_throttled)
921 		dl_se->dl_throttled = 0;
922 
923 	/*
924 	 * If this is the replenishment of a deferred reservation,
925 	 * clear the flag and return.
926 	 */
927 	if (dl_se->dl_defer_armed) {
928 		dl_se->dl_defer_armed = 0;
929 		return;
930 	}
931 
932 	/*
933 	 * A this point, if the deferred server is not armed, and the deadline
934 	 * is in the future, if it is not running already, throttle the server
935 	 * and arm the defer timer.
936 	 */
937 	if (dl_se->dl_defer && !dl_se->dl_defer_running &&
938 	    dl_time_before(rq_clock(dl_se->rq), dl_se->deadline - dl_se->runtime)) {
939 		if (!is_dl_boosted(dl_se) && dl_se->server_has_tasks(dl_se)) {
940 
941 			/*
942 			 * Set dl_se->dl_defer_armed and dl_throttled variables to
943 			 * inform the start_dl_timer() that this is a deferred
944 			 * activation.
945 			 */
946 			dl_se->dl_defer_armed = 1;
947 			dl_se->dl_throttled = 1;
948 			if (!start_dl_timer(dl_se)) {
949 				/*
950 				 * If for whatever reason (delays), a previous timer was
951 				 * queued but not serviced, cancel it and clean the
952 				 * deferrable server variables intended for start_dl_timer().
953 				 */
954 				hrtimer_try_to_cancel(&dl_se->dl_timer);
955 				dl_se->dl_defer_armed = 0;
956 				dl_se->dl_throttled = 0;
957 			}
958 		}
959 	}
960 }
961 
962 /*
963  * Here we check if --at time t-- an entity (which is probably being
964  * [re]activated or, in general, enqueued) can use its remaining runtime
965  * and its current deadline _without_ exceeding the bandwidth it is
966  * assigned (function returns true if it can't). We are in fact applying
967  * one of the CBS rules: when a task wakes up, if the residual runtime
968  * over residual deadline fits within the allocated bandwidth, then we
969  * can keep the current (absolute) deadline and residual budget without
970  * disrupting the schedulability of the system. Otherwise, we should
971  * refill the runtime and set the deadline a period in the future,
972  * because keeping the current (absolute) deadline of the task would
973  * result in breaking guarantees promised to other tasks (refer to
974  * Documentation/scheduler/sched-deadline.rst for more information).
975  *
976  * This function returns true if:
977  *
978  *   runtime / (deadline - t) > dl_runtime / dl_deadline ,
979  *
980  * IOW we can't recycle current parameters.
981  *
982  * Notice that the bandwidth check is done against the deadline. For
983  * task with deadline equal to period this is the same of using
984  * dl_period instead of dl_deadline in the equation above.
985  */
dl_entity_overflow(struct sched_dl_entity * dl_se,u64 t)986 static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t)
987 {
988 	u64 left, right;
989 
990 	/*
991 	 * left and right are the two sides of the equation above,
992 	 * after a bit of shuffling to use multiplications instead
993 	 * of divisions.
994 	 *
995 	 * Note that none of the time values involved in the two
996 	 * multiplications are absolute: dl_deadline and dl_runtime
997 	 * are the relative deadline and the maximum runtime of each
998 	 * instance, runtime is the runtime left for the last instance
999 	 * and (deadline - t), since t is rq->clock, is the time left
1000 	 * to the (absolute) deadline. Even if overflowing the u64 type
1001 	 * is very unlikely to occur in both cases, here we scale down
1002 	 * as we want to avoid that risk at all. Scaling down by 10
1003 	 * means that we reduce granularity to 1us. We are fine with it,
1004 	 * since this is only a true/false check and, anyway, thinking
1005 	 * of anything below microseconds resolution is actually fiction
1006 	 * (but still we want to give the user that illusion >;).
1007 	 */
1008 	left = (pi_of(dl_se)->dl_deadline >> DL_SCALE) * (dl_se->runtime >> DL_SCALE);
1009 	right = ((dl_se->deadline - t) >> DL_SCALE) *
1010 		(pi_of(dl_se)->dl_runtime >> DL_SCALE);
1011 
1012 	return dl_time_before(right, left);
1013 }
1014 
1015 /*
1016  * Revised wakeup rule [1]: For self-suspending tasks, rather then
1017  * re-initializing task's runtime and deadline, the revised wakeup
1018  * rule adjusts the task's runtime to avoid the task to overrun its
1019  * density.
1020  *
1021  * Reasoning: a task may overrun the density if:
1022  *    runtime / (deadline - t) > dl_runtime / dl_deadline
1023  *
1024  * Therefore, runtime can be adjusted to:
1025  *     runtime = (dl_runtime / dl_deadline) * (deadline - t)
1026  *
1027  * In such way that runtime will be equal to the maximum density
1028  * the task can use without breaking any rule.
1029  *
1030  * [1] Luca Abeni, Giuseppe Lipari, and Juri Lelli. 2015. Constant
1031  * bandwidth server revisited. SIGBED Rev. 11, 4 (January 2015), 19-24.
1032  */
1033 static void
update_dl_revised_wakeup(struct sched_dl_entity * dl_se,struct rq * rq)1034 update_dl_revised_wakeup(struct sched_dl_entity *dl_se, struct rq *rq)
1035 {
1036 	u64 laxity = dl_se->deadline - rq_clock(rq);
1037 
1038 	/*
1039 	 * If the task has deadline < period, and the deadline is in the past,
1040 	 * it should already be throttled before this check.
1041 	 *
1042 	 * See update_dl_entity() comments for further details.
1043 	 */
1044 	WARN_ON(dl_time_before(dl_se->deadline, rq_clock(rq)));
1045 
1046 	dl_se->runtime = (dl_se->dl_density * laxity) >> BW_SHIFT;
1047 }
1048 
1049 /*
1050  * Regarding the deadline, a task with implicit deadline has a relative
1051  * deadline == relative period. A task with constrained deadline has a
1052  * relative deadline <= relative period.
1053  *
1054  * We support constrained deadline tasks. However, there are some restrictions
1055  * applied only for tasks which do not have an implicit deadline. See
1056  * update_dl_entity() to know more about such restrictions.
1057  *
1058  * The dl_is_implicit() returns true if the task has an implicit deadline.
1059  */
dl_is_implicit(struct sched_dl_entity * dl_se)1060 static inline bool dl_is_implicit(struct sched_dl_entity *dl_se)
1061 {
1062 	return dl_se->dl_deadline == dl_se->dl_period;
1063 }
1064 
1065 /*
1066  * When a deadline entity is placed in the runqueue, its runtime and deadline
1067  * might need to be updated. This is done by a CBS wake up rule. There are two
1068  * different rules: 1) the original CBS; and 2) the Revisited CBS.
1069  *
1070  * When the task is starting a new period, the Original CBS is used. In this
1071  * case, the runtime is replenished and a new absolute deadline is set.
1072  *
1073  * When a task is queued before the begin of the next period, using the
1074  * remaining runtime and deadline could make the entity to overflow, see
1075  * dl_entity_overflow() to find more about runtime overflow. When such case
1076  * is detected, the runtime and deadline need to be updated.
1077  *
1078  * If the task has an implicit deadline, i.e., deadline == period, the Original
1079  * CBS is applied. The runtime is replenished and a new absolute deadline is
1080  * set, as in the previous cases.
1081  *
1082  * However, the Original CBS does not work properly for tasks with
1083  * deadline < period, which are said to have a constrained deadline. By
1084  * applying the Original CBS, a constrained deadline task would be able to run
1085  * runtime/deadline in a period. With deadline < period, the task would
1086  * overrun the runtime/period allowed bandwidth, breaking the admission test.
1087  *
1088  * In order to prevent this misbehave, the Revisited CBS is used for
1089  * constrained deadline tasks when a runtime overflow is detected. In the
1090  * Revisited CBS, rather than replenishing & setting a new absolute deadline,
1091  * the remaining runtime of the task is reduced to avoid runtime overflow.
1092  * Please refer to the comments update_dl_revised_wakeup() function to find
1093  * more about the Revised CBS rule.
1094  */
update_dl_entity(struct sched_dl_entity * dl_se)1095 static void update_dl_entity(struct sched_dl_entity *dl_se)
1096 {
1097 	struct rq *rq = rq_of_dl_se(dl_se);
1098 
1099 	if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
1100 	    dl_entity_overflow(dl_se, rq_clock(rq))) {
1101 
1102 		if (unlikely(!dl_is_implicit(dl_se) &&
1103 			     !dl_time_before(dl_se->deadline, rq_clock(rq)) &&
1104 			     !is_dl_boosted(dl_se))) {
1105 			update_dl_revised_wakeup(dl_se, rq);
1106 			return;
1107 		}
1108 
1109 		replenish_dl_new_period(dl_se, rq);
1110 	} else if (dl_server(dl_se) && dl_se->dl_defer) {
1111 		/*
1112 		 * The server can still use its previous deadline, so check if
1113 		 * it left the dl_defer_running state.
1114 		 */
1115 		if (!dl_se->dl_defer_running) {
1116 			dl_se->dl_defer_armed = 1;
1117 			dl_se->dl_throttled = 1;
1118 		}
1119 	}
1120 }
1121 
dl_next_period(struct sched_dl_entity * dl_se)1122 static inline u64 dl_next_period(struct sched_dl_entity *dl_se)
1123 {
1124 	return dl_se->deadline - dl_se->dl_deadline + dl_se->dl_period;
1125 }
1126 
1127 /*
1128  * If the entity depleted all its runtime, and if we want it to sleep
1129  * while waiting for some new execution time to become available, we
1130  * set the bandwidth replenishment timer to the replenishment instant
1131  * and try to activate it.
1132  *
1133  * Notice that it is important for the caller to know if the timer
1134  * actually started or not (i.e., the replenishment instant is in
1135  * the future or in the past).
1136  */
start_dl_timer(struct sched_dl_entity * dl_se)1137 static int start_dl_timer(struct sched_dl_entity *dl_se)
1138 {
1139 	struct hrtimer *timer = &dl_se->dl_timer;
1140 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
1141 	struct rq *rq = rq_of_dl_rq(dl_rq);
1142 	ktime_t now, act;
1143 	s64 delta;
1144 
1145 	lockdep_assert_rq_held(rq);
1146 
1147 	/*
1148 	 * We want the timer to fire at the deadline, but considering
1149 	 * that it is actually coming from rq->clock and not from
1150 	 * hrtimer's time base reading.
1151 	 *
1152 	 * The deferred reservation will have its timer set to
1153 	 * (deadline - runtime). At that point, the CBS rule will decide
1154 	 * if the current deadline can be used, or if a replenishment is
1155 	 * required to avoid add too much pressure on the system
1156 	 * (current u > U).
1157 	 */
1158 	if (dl_se->dl_defer_armed) {
1159 		WARN_ON_ONCE(!dl_se->dl_throttled);
1160 		act = ns_to_ktime(dl_se->deadline - dl_se->runtime);
1161 	} else {
1162 		/* act = deadline - rel-deadline + period */
1163 		act = ns_to_ktime(dl_next_period(dl_se));
1164 	}
1165 
1166 	now = hrtimer_cb_get_time(timer);
1167 	delta = ktime_to_ns(now) - rq_clock(rq);
1168 	act = ktime_add_ns(act, delta);
1169 
1170 	/*
1171 	 * If the expiry time already passed, e.g., because the value
1172 	 * chosen as the deadline is too small, don't even try to
1173 	 * start the timer in the past!
1174 	 */
1175 	if (ktime_us_delta(act, now) < 0)
1176 		return 0;
1177 
1178 	/*
1179 	 * !enqueued will guarantee another callback; even if one is already in
1180 	 * progress. This ensures a balanced {get,put}_task_struct().
1181 	 *
1182 	 * The race against __run_timer() clearing the enqueued state is
1183 	 * harmless because we're holding task_rq()->lock, therefore the timer
1184 	 * expiring after we've done the check will wait on its task_rq_lock()
1185 	 * and observe our state.
1186 	 */
1187 	if (!hrtimer_is_queued(timer)) {
1188 		if (!dl_server(dl_se))
1189 			get_task_struct(dl_task_of(dl_se));
1190 		hrtimer_start(timer, act, HRTIMER_MODE_ABS_HARD);
1191 	}
1192 
1193 	return 1;
1194 }
1195 
__push_dl_task(struct rq * rq,struct rq_flags * rf)1196 static void __push_dl_task(struct rq *rq, struct rq_flags *rf)
1197 {
1198 #ifdef CONFIG_SMP
1199 	/*
1200 	 * Queueing this task back might have overloaded rq, check if we need
1201 	 * to kick someone away.
1202 	 */
1203 	if (has_pushable_dl_tasks(rq)) {
1204 		/*
1205 		 * Nothing relies on rq->lock after this, so its safe to drop
1206 		 * rq->lock.
1207 		 */
1208 		rq_unpin_lock(rq, rf);
1209 		push_dl_task(rq);
1210 		rq_repin_lock(rq, rf);
1211 	}
1212 #endif
1213 }
1214 
1215 /* a defer timer will not be reset if the runtime consumed was < dl_server_min_res */
1216 static const u64 dl_server_min_res = 1 * NSEC_PER_MSEC;
1217 
dl_server_timer(struct hrtimer * timer,struct sched_dl_entity * dl_se)1218 static enum hrtimer_restart dl_server_timer(struct hrtimer *timer, struct sched_dl_entity *dl_se)
1219 {
1220 	struct rq *rq = rq_of_dl_se(dl_se);
1221 	u64 fw;
1222 
1223 	scoped_guard (rq_lock, rq) {
1224 		struct rq_flags *rf = &scope.rf;
1225 
1226 		if (!dl_se->dl_throttled || !dl_se->dl_runtime)
1227 			return HRTIMER_NORESTART;
1228 
1229 		sched_clock_tick();
1230 		update_rq_clock(rq);
1231 
1232 		if (!dl_se->dl_runtime)
1233 			return HRTIMER_NORESTART;
1234 
1235 		if (!dl_se->server_has_tasks(dl_se)) {
1236 			replenish_dl_entity(dl_se);
1237 			return HRTIMER_NORESTART;
1238 		}
1239 
1240 		if (dl_se->dl_defer_armed) {
1241 			/*
1242 			 * First check if the server could consume runtime in background.
1243 			 * If so, it is possible to push the defer timer for this amount
1244 			 * of time. The dl_server_min_res serves as a limit to avoid
1245 			 * forwarding the timer for a too small amount of time.
1246 			 */
1247 			if (dl_time_before(rq_clock(dl_se->rq),
1248 					   (dl_se->deadline - dl_se->runtime - dl_server_min_res))) {
1249 
1250 				/* reset the defer timer */
1251 				fw = dl_se->deadline - rq_clock(dl_se->rq) - dl_se->runtime;
1252 
1253 				hrtimer_forward_now(timer, ns_to_ktime(fw));
1254 				return HRTIMER_RESTART;
1255 			}
1256 
1257 			dl_se->dl_defer_running = 1;
1258 		}
1259 
1260 		enqueue_dl_entity(dl_se, ENQUEUE_REPLENISH);
1261 
1262 		if (!dl_task(dl_se->rq->curr) || dl_entity_preempt(dl_se, &dl_se->rq->curr->dl))
1263 			resched_curr(rq);
1264 
1265 		__push_dl_task(rq, rf);
1266 	}
1267 
1268 	return HRTIMER_NORESTART;
1269 }
1270 
1271 /*
1272  * This is the bandwidth enforcement timer callback. If here, we know
1273  * a task is not on its dl_rq, since the fact that the timer was running
1274  * means the task is throttled and needs a runtime replenishment.
1275  *
1276  * However, what we actually do depends on the fact the task is active,
1277  * (it is on its rq) or has been removed from there by a call to
1278  * dequeue_task_dl(). In the former case we must issue the runtime
1279  * replenishment and add the task back to the dl_rq; in the latter, we just
1280  * do nothing but clearing dl_throttled, so that runtime and deadline
1281  * updating (and the queueing back to dl_rq) will be done by the
1282  * next call to enqueue_task_dl().
1283  */
dl_task_timer(struct hrtimer * timer)1284 static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
1285 {
1286 	struct sched_dl_entity *dl_se = container_of(timer,
1287 						     struct sched_dl_entity,
1288 						     dl_timer);
1289 	struct task_struct *p;
1290 	struct rq_flags rf;
1291 	struct rq *rq;
1292 
1293 	if (dl_server(dl_se))
1294 		return dl_server_timer(timer, dl_se);
1295 
1296 	p = dl_task_of(dl_se);
1297 	rq = task_rq_lock(p, &rf);
1298 
1299 	/*
1300 	 * The task might have changed its scheduling policy to something
1301 	 * different than SCHED_DEADLINE (through switched_from_dl()).
1302 	 */
1303 	if (!dl_task(p))
1304 		goto unlock;
1305 
1306 	/*
1307 	 * The task might have been boosted by someone else and might be in the
1308 	 * boosting/deboosting path, its not throttled.
1309 	 */
1310 	if (is_dl_boosted(dl_se))
1311 		goto unlock;
1312 
1313 	/*
1314 	 * Spurious timer due to start_dl_timer() race; or we already received
1315 	 * a replenishment from rt_mutex_setprio().
1316 	 */
1317 	if (!dl_se->dl_throttled)
1318 		goto unlock;
1319 
1320 	sched_clock_tick();
1321 	update_rq_clock(rq);
1322 
1323 	/*
1324 	 * If the throttle happened during sched-out; like:
1325 	 *
1326 	 *   schedule()
1327 	 *     deactivate_task()
1328 	 *       dequeue_task_dl()
1329 	 *         update_curr_dl()
1330 	 *           start_dl_timer()
1331 	 *         __dequeue_task_dl()
1332 	 *     prev->on_rq = 0;
1333 	 *
1334 	 * We can be both throttled and !queued. Replenish the counter
1335 	 * but do not enqueue -- wait for our wakeup to do that.
1336 	 */
1337 	if (!task_on_rq_queued(p)) {
1338 		replenish_dl_entity(dl_se);
1339 		goto unlock;
1340 	}
1341 
1342 #ifdef CONFIG_SMP
1343 	if (unlikely(!rq->online)) {
1344 		/*
1345 		 * If the runqueue is no longer available, migrate the
1346 		 * task elsewhere. This necessarily changes rq.
1347 		 */
1348 		lockdep_unpin_lock(__rq_lockp(rq), rf.cookie);
1349 		rq = dl_task_offline_migration(rq, p);
1350 		rf.cookie = lockdep_pin_lock(__rq_lockp(rq));
1351 		update_rq_clock(rq);
1352 
1353 		/*
1354 		 * Now that the task has been migrated to the new RQ and we
1355 		 * have that locked, proceed as normal and enqueue the task
1356 		 * there.
1357 		 */
1358 	}
1359 #endif
1360 
1361 	enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
1362 	if (dl_task(rq->donor))
1363 		wakeup_preempt_dl(rq, p, 0);
1364 	else
1365 		resched_curr(rq);
1366 
1367 	__push_dl_task(rq, &rf);
1368 
1369 unlock:
1370 	task_rq_unlock(rq, p, &rf);
1371 
1372 	/*
1373 	 * This can free the task_struct, including this hrtimer, do not touch
1374 	 * anything related to that after this.
1375 	 */
1376 	put_task_struct(p);
1377 
1378 	return HRTIMER_NORESTART;
1379 }
1380 
init_dl_task_timer(struct sched_dl_entity * dl_se)1381 static void init_dl_task_timer(struct sched_dl_entity *dl_se)
1382 {
1383 	struct hrtimer *timer = &dl_se->dl_timer;
1384 
1385 	hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
1386 	timer->function = dl_task_timer;
1387 }
1388 
1389 /*
1390  * During the activation, CBS checks if it can reuse the current task's
1391  * runtime and period. If the deadline of the task is in the past, CBS
1392  * cannot use the runtime, and so it replenishes the task. This rule
1393  * works fine for implicit deadline tasks (deadline == period), and the
1394  * CBS was designed for implicit deadline tasks. However, a task with
1395  * constrained deadline (deadline < period) might be awakened after the
1396  * deadline, but before the next period. In this case, replenishing the
1397  * task would allow it to run for runtime / deadline. As in this case
1398  * deadline < period, CBS enables a task to run for more than the
1399  * runtime / period. In a very loaded system, this can cause a domino
1400  * effect, making other tasks miss their deadlines.
1401  *
1402  * To avoid this problem, in the activation of a constrained deadline
1403  * task after the deadline but before the next period, throttle the
1404  * task and set the replenishing timer to the begin of the next period,
1405  * unless it is boosted.
1406  */
dl_check_constrained_dl(struct sched_dl_entity * dl_se)1407 static inline void dl_check_constrained_dl(struct sched_dl_entity *dl_se)
1408 {
1409 	struct rq *rq = rq_of_dl_se(dl_se);
1410 
1411 	if (dl_time_before(dl_se->deadline, rq_clock(rq)) &&
1412 	    dl_time_before(rq_clock(rq), dl_next_period(dl_se))) {
1413 		if (unlikely(is_dl_boosted(dl_se) || !start_dl_timer(dl_se)))
1414 			return;
1415 		dl_se->dl_throttled = 1;
1416 		if (dl_se->runtime > 0)
1417 			dl_se->runtime = 0;
1418 	}
1419 }
1420 
1421 static
dl_runtime_exceeded(struct sched_dl_entity * dl_se)1422 int dl_runtime_exceeded(struct sched_dl_entity *dl_se)
1423 {
1424 	return (dl_se->runtime <= 0);
1425 }
1426 
1427 /*
1428  * This function implements the GRUB accounting rule. According to the
1429  * GRUB reclaiming algorithm, the runtime is not decreased as "dq = -dt",
1430  * but as "dq = -(max{u, (Umax - Uinact - Uextra)} / Umax) dt",
1431  * where u is the utilization of the task, Umax is the maximum reclaimable
1432  * utilization, Uinact is the (per-runqueue) inactive utilization, computed
1433  * as the difference between the "total runqueue utilization" and the
1434  * "runqueue active utilization", and Uextra is the (per runqueue) extra
1435  * reclaimable utilization.
1436  * Since rq->dl.running_bw and rq->dl.this_bw contain utilizations multiplied
1437  * by 2^BW_SHIFT, the result has to be shifted right by BW_SHIFT.
1438  * Since rq->dl.bw_ratio contains 1 / Umax multiplied by 2^RATIO_SHIFT, dl_bw
1439  * is multiplied by rq->dl.bw_ratio and shifted right by RATIO_SHIFT.
1440  * Since delta is a 64 bit variable, to have an overflow its value should be
1441  * larger than 2^(64 - 20 - 8), which is more than 64 seconds. So, overflow is
1442  * not an issue here.
1443  */
grub_reclaim(u64 delta,struct rq * rq,struct sched_dl_entity * dl_se)1444 static u64 grub_reclaim(u64 delta, struct rq *rq, struct sched_dl_entity *dl_se)
1445 {
1446 	u64 u_act;
1447 	u64 u_inact = rq->dl.this_bw - rq->dl.running_bw; /* Utot - Uact */
1448 
1449 	/*
1450 	 * Instead of computing max{u, (u_max - u_inact - u_extra)}, we
1451 	 * compare u_inact + u_extra with u_max - u, because u_inact + u_extra
1452 	 * can be larger than u_max. So, u_max - u_inact - u_extra would be
1453 	 * negative leading to wrong results.
1454 	 */
1455 	if (u_inact + rq->dl.extra_bw > rq->dl.max_bw - dl_se->dl_bw)
1456 		u_act = dl_se->dl_bw;
1457 	else
1458 		u_act = rq->dl.max_bw - u_inact - rq->dl.extra_bw;
1459 
1460 	u_act = (u_act * rq->dl.bw_ratio) >> RATIO_SHIFT;
1461 	return (delta * u_act) >> BW_SHIFT;
1462 }
1463 
dl_scaled_delta_exec(struct rq * rq,struct sched_dl_entity * dl_se,s64 delta_exec)1464 s64 dl_scaled_delta_exec(struct rq *rq, struct sched_dl_entity *dl_se, s64 delta_exec)
1465 {
1466 	s64 scaled_delta_exec;
1467 
1468 	/*
1469 	 * For tasks that participate in GRUB, we implement GRUB-PA: the
1470 	 * spare reclaimed bandwidth is used to clock down frequency.
1471 	 *
1472 	 * For the others, we still need to scale reservation parameters
1473 	 * according to current frequency and CPU maximum capacity.
1474 	 */
1475 	if (unlikely(dl_se->flags & SCHED_FLAG_RECLAIM)) {
1476 		scaled_delta_exec = grub_reclaim(delta_exec, rq, dl_se);
1477 	} else {
1478 		int cpu = cpu_of(rq);
1479 		unsigned long scale_freq = arch_scale_freq_capacity(cpu);
1480 		unsigned long scale_cpu = arch_scale_cpu_capacity(cpu);
1481 
1482 		scaled_delta_exec = cap_scale(delta_exec, scale_freq);
1483 		scaled_delta_exec = cap_scale(scaled_delta_exec, scale_cpu);
1484 	}
1485 
1486 	return scaled_delta_exec;
1487 }
1488 
1489 static inline void
1490 update_stats_dequeue_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se,
1491 			int flags);
update_curr_dl_se(struct rq * rq,struct sched_dl_entity * dl_se,s64 delta_exec)1492 static void update_curr_dl_se(struct rq *rq, struct sched_dl_entity *dl_se, s64 delta_exec)
1493 {
1494 	s64 scaled_delta_exec;
1495 
1496 	if (unlikely(delta_exec <= 0)) {
1497 		if (unlikely(dl_se->dl_yielded))
1498 			goto throttle;
1499 		return;
1500 	}
1501 
1502 	if (dl_server(dl_se) && dl_se->dl_throttled && !dl_se->dl_defer)
1503 		return;
1504 
1505 	if (dl_entity_is_special(dl_se))
1506 		return;
1507 
1508 	scaled_delta_exec = dl_scaled_delta_exec(rq, dl_se, delta_exec);
1509 
1510 	dl_se->runtime -= scaled_delta_exec;
1511 
1512 	/*
1513 	 * The fair server can consume its runtime while throttled (not queued/
1514 	 * running as regular CFS).
1515 	 *
1516 	 * If the server consumes its entire runtime in this state. The server
1517 	 * is not required for the current period. Thus, reset the server by
1518 	 * starting a new period, pushing the activation.
1519 	 */
1520 	if (dl_se->dl_defer && dl_se->dl_throttled && dl_runtime_exceeded(dl_se)) {
1521 		/*
1522 		 * If the server was previously activated - the starving condition
1523 		 * took place, it this point it went away because the fair scheduler
1524 		 * was able to get runtime in background. So return to the initial
1525 		 * state.
1526 		 */
1527 		dl_se->dl_defer_running = 0;
1528 
1529 		hrtimer_try_to_cancel(&dl_se->dl_timer);
1530 
1531 		replenish_dl_new_period(dl_se, dl_se->rq);
1532 
1533 		/*
1534 		 * Not being able to start the timer seems problematic. If it could not
1535 		 * be started for whatever reason, we need to "unthrottle" the DL server
1536 		 * and queue right away. Otherwise nothing might queue it. That's similar
1537 		 * to what enqueue_dl_entity() does on start_dl_timer==0. For now, just warn.
1538 		 */
1539 		WARN_ON_ONCE(!start_dl_timer(dl_se));
1540 
1541 		return;
1542 	}
1543 
1544 throttle:
1545 	if (dl_runtime_exceeded(dl_se) || dl_se->dl_yielded) {
1546 		dl_se->dl_throttled = 1;
1547 
1548 		/* If requested, inform the user about runtime overruns. */
1549 		if (dl_runtime_exceeded(dl_se) &&
1550 		    (dl_se->flags & SCHED_FLAG_DL_OVERRUN))
1551 			dl_se->dl_overrun = 1;
1552 
1553 		dequeue_dl_entity(dl_se, 0);
1554 		if (!dl_server(dl_se)) {
1555 			update_stats_dequeue_dl(&rq->dl, dl_se, 0);
1556 			dequeue_pushable_dl_task(rq, dl_task_of(dl_se));
1557 		}
1558 
1559 		if (unlikely(is_dl_boosted(dl_se) || !start_dl_timer(dl_se))) {
1560 			if (dl_server(dl_se))
1561 				enqueue_dl_entity(dl_se, ENQUEUE_REPLENISH);
1562 			else
1563 				enqueue_task_dl(rq, dl_task_of(dl_se), ENQUEUE_REPLENISH);
1564 		}
1565 
1566 		if (!is_leftmost(dl_se, &rq->dl))
1567 			resched_curr(rq);
1568 	}
1569 
1570 	/*
1571 	 * The fair server (sole dl_server) does not account for real-time
1572 	 * workload because it is running fair work.
1573 	 */
1574 	if (dl_se == &rq->fair_server)
1575 		return;
1576 
1577 #ifdef CONFIG_RT_GROUP_SCHED
1578 	/*
1579 	 * Because -- for now -- we share the rt bandwidth, we need to
1580 	 * account our runtime there too, otherwise actual rt tasks
1581 	 * would be able to exceed the shared quota.
1582 	 *
1583 	 * Account to the root rt group for now.
1584 	 *
1585 	 * The solution we're working towards is having the RT groups scheduled
1586 	 * using deadline servers -- however there's a few nasties to figure
1587 	 * out before that can happen.
1588 	 */
1589 	if (rt_bandwidth_enabled()) {
1590 		struct rt_rq *rt_rq = &rq->rt;
1591 
1592 		raw_spin_lock(&rt_rq->rt_runtime_lock);
1593 		/*
1594 		 * We'll let actual RT tasks worry about the overflow here, we
1595 		 * have our own CBS to keep us inline; only account when RT
1596 		 * bandwidth is relevant.
1597 		 */
1598 		if (sched_rt_bandwidth_account(rt_rq))
1599 			rt_rq->rt_time += delta_exec;
1600 		raw_spin_unlock(&rt_rq->rt_runtime_lock);
1601 	}
1602 #endif
1603 }
1604 
1605 /*
1606  * In the non-defer mode, the idle time is not accounted, as the
1607  * server provides a guarantee.
1608  *
1609  * If the dl_server is in defer mode, the idle time is also considered
1610  * as time available for the fair server, avoiding a penalty for the
1611  * rt scheduler that did not consumed that time.
1612  */
dl_server_update_idle_time(struct rq * rq,struct task_struct * p)1613 void dl_server_update_idle_time(struct rq *rq, struct task_struct *p)
1614 {
1615 	s64 delta_exec, scaled_delta_exec;
1616 
1617 	if (!rq->fair_server.dl_defer)
1618 		return;
1619 
1620 	/* no need to discount more */
1621 	if (rq->fair_server.runtime < 0)
1622 		return;
1623 
1624 	delta_exec = rq_clock_task(rq) - p->se.exec_start;
1625 	if (delta_exec < 0)
1626 		return;
1627 
1628 	scaled_delta_exec = dl_scaled_delta_exec(rq, &rq->fair_server, delta_exec);
1629 
1630 	rq->fair_server.runtime -= scaled_delta_exec;
1631 
1632 	if (rq->fair_server.runtime < 0) {
1633 		rq->fair_server.dl_defer_running = 0;
1634 		rq->fair_server.runtime = 0;
1635 	}
1636 
1637 	p->se.exec_start = rq_clock_task(rq);
1638 }
1639 
dl_server_update(struct sched_dl_entity * dl_se,s64 delta_exec)1640 void dl_server_update(struct sched_dl_entity *dl_se, s64 delta_exec)
1641 {
1642 	/* 0 runtime = fair server disabled */
1643 	if (dl_se->dl_runtime)
1644 		update_curr_dl_se(dl_se->rq, dl_se, delta_exec);
1645 }
1646 
dl_server_start(struct sched_dl_entity * dl_se)1647 void dl_server_start(struct sched_dl_entity *dl_se)
1648 {
1649 	struct rq *rq = dl_se->rq;
1650 
1651 	/*
1652 	 * XXX: the apply do not work fine at the init phase for the
1653 	 * fair server because things are not yet set. We need to improve
1654 	 * this before getting generic.
1655 	 */
1656 	if (!dl_server(dl_se)) {
1657 		u64 runtime =  50 * NSEC_PER_MSEC;
1658 		u64 period = 1000 * NSEC_PER_MSEC;
1659 
1660 		dl_server_apply_params(dl_se, runtime, period, 1);
1661 
1662 		dl_se->dl_server = 1;
1663 		dl_se->dl_defer = 1;
1664 		setup_new_dl_entity(dl_se);
1665 	}
1666 
1667 	if (!dl_se->dl_runtime)
1668 		return;
1669 
1670 	dl_se->dl_server_active = 1;
1671 	enqueue_dl_entity(dl_se, ENQUEUE_WAKEUP);
1672 	if (!dl_task(dl_se->rq->curr) || dl_entity_preempt(dl_se, &rq->curr->dl))
1673 		resched_curr(dl_se->rq);
1674 }
1675 
dl_server_stop(struct sched_dl_entity * dl_se)1676 void dl_server_stop(struct sched_dl_entity *dl_se)
1677 {
1678 	if (!dl_se->dl_runtime)
1679 		return;
1680 
1681 	dequeue_dl_entity(dl_se, DEQUEUE_SLEEP);
1682 	hrtimer_try_to_cancel(&dl_se->dl_timer);
1683 	dl_se->dl_defer_armed = 0;
1684 	dl_se->dl_throttled = 0;
1685 	dl_se->dl_server_active = 0;
1686 }
1687 
dl_server_init(struct sched_dl_entity * dl_se,struct rq * rq,dl_server_has_tasks_f has_tasks,dl_server_pick_f pick_task)1688 void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq,
1689 		    dl_server_has_tasks_f has_tasks,
1690 		    dl_server_pick_f pick_task)
1691 {
1692 	dl_se->rq = rq;
1693 	dl_se->server_has_tasks = has_tasks;
1694 	dl_se->server_pick_task = pick_task;
1695 }
1696 
__dl_server_attach_root(struct sched_dl_entity * dl_se,struct rq * rq)1697 void __dl_server_attach_root(struct sched_dl_entity *dl_se, struct rq *rq)
1698 {
1699 	u64 new_bw = dl_se->dl_bw;
1700 	int cpu = cpu_of(rq);
1701 	struct dl_bw *dl_b;
1702 
1703 	dl_b = dl_bw_of(cpu_of(rq));
1704 	guard(raw_spinlock)(&dl_b->lock);
1705 
1706 	if (!dl_bw_cpus(cpu))
1707 		return;
1708 
1709 	__dl_add(dl_b, new_bw, dl_bw_cpus(cpu));
1710 }
1711 
dl_server_apply_params(struct sched_dl_entity * dl_se,u64 runtime,u64 period,bool init)1712 int dl_server_apply_params(struct sched_dl_entity *dl_se, u64 runtime, u64 period, bool init)
1713 {
1714 	u64 old_bw = init ? 0 : to_ratio(dl_se->dl_period, dl_se->dl_runtime);
1715 	u64 new_bw = to_ratio(period, runtime);
1716 	struct rq *rq = dl_se->rq;
1717 	int cpu = cpu_of(rq);
1718 	struct dl_bw *dl_b;
1719 	unsigned long cap;
1720 	int retval = 0;
1721 	int cpus;
1722 
1723 	dl_b = dl_bw_of(cpu);
1724 	guard(raw_spinlock)(&dl_b->lock);
1725 
1726 	cpus = dl_bw_cpus(cpu);
1727 	cap = dl_bw_capacity(cpu);
1728 
1729 	if (__dl_overflow(dl_b, cap, old_bw, new_bw))
1730 		return -EBUSY;
1731 
1732 	if (init) {
1733 		__add_rq_bw(new_bw, &rq->dl);
1734 		__dl_add(dl_b, new_bw, cpus);
1735 	} else {
1736 		__dl_sub(dl_b, dl_se->dl_bw, cpus);
1737 		__dl_add(dl_b, new_bw, cpus);
1738 
1739 		dl_rq_change_utilization(rq, dl_se, new_bw);
1740 	}
1741 
1742 	dl_se->dl_runtime = runtime;
1743 	dl_se->dl_deadline = period;
1744 	dl_se->dl_period = period;
1745 
1746 	dl_se->runtime = 0;
1747 	dl_se->deadline = 0;
1748 
1749 	dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime);
1750 	dl_se->dl_density = to_ratio(dl_se->dl_deadline, dl_se->dl_runtime);
1751 
1752 	return retval;
1753 }
1754 
1755 /*
1756  * Update the current task's runtime statistics (provided it is still
1757  * a -deadline task and has not been removed from the dl_rq).
1758  */
update_curr_dl(struct rq * rq)1759 static void update_curr_dl(struct rq *rq)
1760 {
1761 	struct task_struct *donor = rq->donor;
1762 	struct sched_dl_entity *dl_se = &donor->dl;
1763 	s64 delta_exec;
1764 
1765 	if (!dl_task(donor) || !on_dl_rq(dl_se))
1766 		return;
1767 
1768 	/*
1769 	 * Consumed budget is computed considering the time as
1770 	 * observed by schedulable tasks (excluding time spent
1771 	 * in hardirq context, etc.). Deadlines are instead
1772 	 * computed using hard walltime. This seems to be the more
1773 	 * natural solution, but the full ramifications of this
1774 	 * approach need further study.
1775 	 */
1776 	delta_exec = update_curr_common(rq);
1777 	update_curr_dl_se(rq, dl_se, delta_exec);
1778 }
1779 
inactive_task_timer(struct hrtimer * timer)1780 static enum hrtimer_restart inactive_task_timer(struct hrtimer *timer)
1781 {
1782 	struct sched_dl_entity *dl_se = container_of(timer,
1783 						     struct sched_dl_entity,
1784 						     inactive_timer);
1785 	struct task_struct *p = NULL;
1786 	struct rq_flags rf;
1787 	struct rq *rq;
1788 
1789 	if (!dl_server(dl_se)) {
1790 		p = dl_task_of(dl_se);
1791 		rq = task_rq_lock(p, &rf);
1792 	} else {
1793 		rq = dl_se->rq;
1794 		rq_lock(rq, &rf);
1795 	}
1796 
1797 	sched_clock_tick();
1798 	update_rq_clock(rq);
1799 
1800 	if (dl_server(dl_se))
1801 		goto no_task;
1802 
1803 	if (!dl_task(p) || READ_ONCE(p->__state) == TASK_DEAD) {
1804 		struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
1805 
1806 		if (READ_ONCE(p->__state) == TASK_DEAD && dl_se->dl_non_contending) {
1807 			sub_running_bw(&p->dl, dl_rq_of_se(&p->dl));
1808 			sub_rq_bw(&p->dl, dl_rq_of_se(&p->dl));
1809 			dl_se->dl_non_contending = 0;
1810 		}
1811 
1812 		raw_spin_lock(&dl_b->lock);
1813 		__dl_sub(dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
1814 		raw_spin_unlock(&dl_b->lock);
1815 		__dl_clear_params(dl_se);
1816 
1817 		goto unlock;
1818 	}
1819 
1820 no_task:
1821 	if (dl_se->dl_non_contending == 0)
1822 		goto unlock;
1823 
1824 	sub_running_bw(dl_se, &rq->dl);
1825 	dl_se->dl_non_contending = 0;
1826 unlock:
1827 
1828 	if (!dl_server(dl_se)) {
1829 		task_rq_unlock(rq, p, &rf);
1830 		put_task_struct(p);
1831 	} else {
1832 		rq_unlock(rq, &rf);
1833 	}
1834 
1835 	return HRTIMER_NORESTART;
1836 }
1837 
init_dl_inactive_task_timer(struct sched_dl_entity * dl_se)1838 static void init_dl_inactive_task_timer(struct sched_dl_entity *dl_se)
1839 {
1840 	struct hrtimer *timer = &dl_se->inactive_timer;
1841 
1842 	hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
1843 	timer->function = inactive_task_timer;
1844 }
1845 
1846 #define __node_2_dle(node) \
1847 	rb_entry((node), struct sched_dl_entity, rb_node)
1848 
1849 #ifdef CONFIG_SMP
1850 
inc_dl_deadline(struct dl_rq * dl_rq,u64 deadline)1851 static void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
1852 {
1853 	struct rq *rq = rq_of_dl_rq(dl_rq);
1854 
1855 	if (dl_rq->earliest_dl.curr == 0 ||
1856 	    dl_time_before(deadline, dl_rq->earliest_dl.curr)) {
1857 		if (dl_rq->earliest_dl.curr == 0)
1858 			cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_HIGHER);
1859 		dl_rq->earliest_dl.curr = deadline;
1860 		cpudl_set(&rq->rd->cpudl, rq->cpu, deadline);
1861 	}
1862 }
1863 
dec_dl_deadline(struct dl_rq * dl_rq,u64 deadline)1864 static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
1865 {
1866 	struct rq *rq = rq_of_dl_rq(dl_rq);
1867 
1868 	/*
1869 	 * Since we may have removed our earliest (and/or next earliest)
1870 	 * task we must recompute them.
1871 	 */
1872 	if (!dl_rq->dl_nr_running) {
1873 		dl_rq->earliest_dl.curr = 0;
1874 		dl_rq->earliest_dl.next = 0;
1875 		cpudl_clear(&rq->rd->cpudl, rq->cpu);
1876 		cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
1877 	} else {
1878 		struct rb_node *leftmost = rb_first_cached(&dl_rq->root);
1879 		struct sched_dl_entity *entry = __node_2_dle(leftmost);
1880 
1881 		dl_rq->earliest_dl.curr = entry->deadline;
1882 		cpudl_set(&rq->rd->cpudl, rq->cpu, entry->deadline);
1883 	}
1884 }
1885 
1886 #else
1887 
inc_dl_deadline(struct dl_rq * dl_rq,u64 deadline)1888 static inline void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
dec_dl_deadline(struct dl_rq * dl_rq,u64 deadline)1889 static inline void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
1890 
1891 #endif /* CONFIG_SMP */
1892 
1893 static inline
inc_dl_tasks(struct sched_dl_entity * dl_se,struct dl_rq * dl_rq)1894 void inc_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
1895 {
1896 	u64 deadline = dl_se->deadline;
1897 
1898 	dl_rq->dl_nr_running++;
1899 	add_nr_running(rq_of_dl_rq(dl_rq), 1);
1900 
1901 	inc_dl_deadline(dl_rq, deadline);
1902 }
1903 
1904 static inline
dec_dl_tasks(struct sched_dl_entity * dl_se,struct dl_rq * dl_rq)1905 void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
1906 {
1907 	WARN_ON(!dl_rq->dl_nr_running);
1908 	dl_rq->dl_nr_running--;
1909 	sub_nr_running(rq_of_dl_rq(dl_rq), 1);
1910 
1911 	dec_dl_deadline(dl_rq, dl_se->deadline);
1912 }
1913 
__dl_less(struct rb_node * a,const struct rb_node * b)1914 static inline bool __dl_less(struct rb_node *a, const struct rb_node *b)
1915 {
1916 	return dl_time_before(__node_2_dle(a)->deadline, __node_2_dle(b)->deadline);
1917 }
1918 
1919 static __always_inline struct sched_statistics *
__schedstats_from_dl_se(struct sched_dl_entity * dl_se)1920 __schedstats_from_dl_se(struct sched_dl_entity *dl_se)
1921 {
1922 	if (!schedstat_enabled())
1923 		return NULL;
1924 
1925 	if (dl_server(dl_se))
1926 		return NULL;
1927 
1928 	return &dl_task_of(dl_se)->stats;
1929 }
1930 
1931 static inline void
update_stats_wait_start_dl(struct dl_rq * dl_rq,struct sched_dl_entity * dl_se)1932 update_stats_wait_start_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se)
1933 {
1934 	struct sched_statistics *stats = __schedstats_from_dl_se(dl_se);
1935 	if (stats)
1936 		__update_stats_wait_start(rq_of_dl_rq(dl_rq), dl_task_of(dl_se), stats);
1937 }
1938 
1939 static inline void
update_stats_wait_end_dl(struct dl_rq * dl_rq,struct sched_dl_entity * dl_se)1940 update_stats_wait_end_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se)
1941 {
1942 	struct sched_statistics *stats = __schedstats_from_dl_se(dl_se);
1943 	if (stats)
1944 		__update_stats_wait_end(rq_of_dl_rq(dl_rq), dl_task_of(dl_se), stats);
1945 }
1946 
1947 static inline void
update_stats_enqueue_sleeper_dl(struct dl_rq * dl_rq,struct sched_dl_entity * dl_se)1948 update_stats_enqueue_sleeper_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se)
1949 {
1950 	struct sched_statistics *stats = __schedstats_from_dl_se(dl_se);
1951 	if (stats)
1952 		__update_stats_enqueue_sleeper(rq_of_dl_rq(dl_rq), dl_task_of(dl_se), stats);
1953 }
1954 
1955 static inline void
update_stats_enqueue_dl(struct dl_rq * dl_rq,struct sched_dl_entity * dl_se,int flags)1956 update_stats_enqueue_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se,
1957 			int flags)
1958 {
1959 	if (!schedstat_enabled())
1960 		return;
1961 
1962 	if (flags & ENQUEUE_WAKEUP)
1963 		update_stats_enqueue_sleeper_dl(dl_rq, dl_se);
1964 }
1965 
1966 static inline void
update_stats_dequeue_dl(struct dl_rq * dl_rq,struct sched_dl_entity * dl_se,int flags)1967 update_stats_dequeue_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se,
1968 			int flags)
1969 {
1970 	struct task_struct *p = dl_task_of(dl_se);
1971 
1972 	if (!schedstat_enabled())
1973 		return;
1974 
1975 	if ((flags & DEQUEUE_SLEEP)) {
1976 		unsigned int state;
1977 
1978 		state = READ_ONCE(p->__state);
1979 		if (state & TASK_INTERRUPTIBLE)
1980 			__schedstat_set(p->stats.sleep_start,
1981 					rq_clock(rq_of_dl_rq(dl_rq)));
1982 
1983 		if (state & TASK_UNINTERRUPTIBLE)
1984 			__schedstat_set(p->stats.block_start,
1985 					rq_clock(rq_of_dl_rq(dl_rq)));
1986 	}
1987 }
1988 
__enqueue_dl_entity(struct sched_dl_entity * dl_se)1989 static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
1990 {
1991 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
1992 
1993 	WARN_ON_ONCE(!RB_EMPTY_NODE(&dl_se->rb_node));
1994 
1995 	rb_add_cached(&dl_se->rb_node, &dl_rq->root, __dl_less);
1996 
1997 	inc_dl_tasks(dl_se, dl_rq);
1998 }
1999 
__dequeue_dl_entity(struct sched_dl_entity * dl_se)2000 static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
2001 {
2002 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
2003 
2004 	if (RB_EMPTY_NODE(&dl_se->rb_node))
2005 		return;
2006 
2007 	rb_erase_cached(&dl_se->rb_node, &dl_rq->root);
2008 
2009 	RB_CLEAR_NODE(&dl_se->rb_node);
2010 
2011 	dec_dl_tasks(dl_se, dl_rq);
2012 }
2013 
2014 static void
enqueue_dl_entity(struct sched_dl_entity * dl_se,int flags)2015 enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags)
2016 {
2017 	WARN_ON_ONCE(on_dl_rq(dl_se));
2018 
2019 	update_stats_enqueue_dl(dl_rq_of_se(dl_se), dl_se, flags);
2020 
2021 	/*
2022 	 * Check if a constrained deadline task was activated
2023 	 * after the deadline but before the next period.
2024 	 * If that is the case, the task will be throttled and
2025 	 * the replenishment timer will be set to the next period.
2026 	 */
2027 	if (!dl_se->dl_throttled && !dl_is_implicit(dl_se))
2028 		dl_check_constrained_dl(dl_se);
2029 
2030 	if (flags & (ENQUEUE_RESTORE|ENQUEUE_MIGRATING)) {
2031 		struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
2032 
2033 		add_rq_bw(dl_se, dl_rq);
2034 		add_running_bw(dl_se, dl_rq);
2035 	}
2036 
2037 	/*
2038 	 * If p is throttled, we do not enqueue it. In fact, if it exhausted
2039 	 * its budget it needs a replenishment and, since it now is on
2040 	 * its rq, the bandwidth timer callback (which clearly has not
2041 	 * run yet) will take care of this.
2042 	 * However, the active utilization does not depend on the fact
2043 	 * that the task is on the runqueue or not (but depends on the
2044 	 * task's state - in GRUB parlance, "inactive" vs "active contending").
2045 	 * In other words, even if a task is throttled its utilization must
2046 	 * be counted in the active utilization; hence, we need to call
2047 	 * add_running_bw().
2048 	 */
2049 	if (!dl_se->dl_defer && dl_se->dl_throttled && !(flags & ENQUEUE_REPLENISH)) {
2050 		if (flags & ENQUEUE_WAKEUP)
2051 			task_contending(dl_se, flags);
2052 
2053 		return;
2054 	}
2055 
2056 	/*
2057 	 * If this is a wakeup or a new instance, the scheduling
2058 	 * parameters of the task might need updating. Otherwise,
2059 	 * we want a replenishment of its runtime.
2060 	 */
2061 	if (flags & ENQUEUE_WAKEUP) {
2062 		task_contending(dl_se, flags);
2063 		update_dl_entity(dl_se);
2064 	} else if (flags & ENQUEUE_REPLENISH) {
2065 		replenish_dl_entity(dl_se);
2066 	} else if ((flags & ENQUEUE_RESTORE) &&
2067 		   !is_dl_boosted(dl_se) &&
2068 		   dl_time_before(dl_se->deadline, rq_clock(rq_of_dl_se(dl_se)))) {
2069 		setup_new_dl_entity(dl_se);
2070 	}
2071 
2072 	/*
2073 	 * If the reservation is still throttled, e.g., it got replenished but is a
2074 	 * deferred task and still got to wait, don't enqueue.
2075 	 */
2076 	if (dl_se->dl_throttled && start_dl_timer(dl_se))
2077 		return;
2078 
2079 	/*
2080 	 * We're about to enqueue, make sure we're not ->dl_throttled!
2081 	 * In case the timer was not started, say because the defer time
2082 	 * has passed, mark as not throttled and mark unarmed.
2083 	 * Also cancel earlier timers, since letting those run is pointless.
2084 	 */
2085 	if (dl_se->dl_throttled) {
2086 		hrtimer_try_to_cancel(&dl_se->dl_timer);
2087 		dl_se->dl_defer_armed = 0;
2088 		dl_se->dl_throttled = 0;
2089 	}
2090 
2091 	__enqueue_dl_entity(dl_se);
2092 }
2093 
dequeue_dl_entity(struct sched_dl_entity * dl_se,int flags)2094 static void dequeue_dl_entity(struct sched_dl_entity *dl_se, int flags)
2095 {
2096 	__dequeue_dl_entity(dl_se);
2097 
2098 	if (flags & (DEQUEUE_SAVE|DEQUEUE_MIGRATING)) {
2099 		struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
2100 
2101 		sub_running_bw(dl_se, dl_rq);
2102 		sub_rq_bw(dl_se, dl_rq);
2103 	}
2104 
2105 	/*
2106 	 * This check allows to start the inactive timer (or to immediately
2107 	 * decrease the active utilization, if needed) in two cases:
2108 	 * when the task blocks and when it is terminating
2109 	 * (p->state == TASK_DEAD). We can handle the two cases in the same
2110 	 * way, because from GRUB's point of view the same thing is happening
2111 	 * (the task moves from "active contending" to "active non contending"
2112 	 * or "inactive")
2113 	 */
2114 	if (flags & DEQUEUE_SLEEP)
2115 		task_non_contending(dl_se);
2116 }
2117 
enqueue_task_dl(struct rq * rq,struct task_struct * p,int flags)2118 static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
2119 {
2120 	if (is_dl_boosted(&p->dl)) {
2121 		/*
2122 		 * Because of delays in the detection of the overrun of a
2123 		 * thread's runtime, it might be the case that a thread
2124 		 * goes to sleep in a rt mutex with negative runtime. As
2125 		 * a consequence, the thread will be throttled.
2126 		 *
2127 		 * While waiting for the mutex, this thread can also be
2128 		 * boosted via PI, resulting in a thread that is throttled
2129 		 * and boosted at the same time.
2130 		 *
2131 		 * In this case, the boost overrides the throttle.
2132 		 */
2133 		if (p->dl.dl_throttled) {
2134 			/*
2135 			 * The replenish timer needs to be canceled. No
2136 			 * problem if it fires concurrently: boosted threads
2137 			 * are ignored in dl_task_timer().
2138 			 */
2139 			cancel_replenish_timer(&p->dl);
2140 			p->dl.dl_throttled = 0;
2141 		}
2142 	} else if (!dl_prio(p->normal_prio)) {
2143 		/*
2144 		 * Special case in which we have a !SCHED_DEADLINE task that is going
2145 		 * to be deboosted, but exceeds its runtime while doing so. No point in
2146 		 * replenishing it, as it's going to return back to its original
2147 		 * scheduling class after this. If it has been throttled, we need to
2148 		 * clear the flag, otherwise the task may wake up as throttled after
2149 		 * being boosted again with no means to replenish the runtime and clear
2150 		 * the throttle.
2151 		 */
2152 		p->dl.dl_throttled = 0;
2153 		if (!(flags & ENQUEUE_REPLENISH))
2154 			printk_deferred_once("sched: DL de-boosted task PID %d: REPLENISH flag missing\n",
2155 					     task_pid_nr(p));
2156 
2157 		return;
2158 	}
2159 
2160 	check_schedstat_required();
2161 	update_stats_wait_start_dl(dl_rq_of_se(&p->dl), &p->dl);
2162 
2163 	if (p->on_rq == TASK_ON_RQ_MIGRATING)
2164 		flags |= ENQUEUE_MIGRATING;
2165 
2166 	enqueue_dl_entity(&p->dl, flags);
2167 
2168 	if (dl_server(&p->dl))
2169 		return;
2170 
2171 	if (!task_current(rq, p) && !p->dl.dl_throttled && p->nr_cpus_allowed > 1)
2172 		enqueue_pushable_dl_task(rq, p);
2173 }
2174 
dequeue_task_dl(struct rq * rq,struct task_struct * p,int flags)2175 static bool dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
2176 {
2177 	update_curr_dl(rq);
2178 
2179 	if (p->on_rq == TASK_ON_RQ_MIGRATING)
2180 		flags |= DEQUEUE_MIGRATING;
2181 
2182 	dequeue_dl_entity(&p->dl, flags);
2183 	if (!p->dl.dl_throttled && !dl_server(&p->dl))
2184 		dequeue_pushable_dl_task(rq, p);
2185 
2186 	return true;
2187 }
2188 
2189 /*
2190  * Yield task semantic for -deadline tasks is:
2191  *
2192  *   get off from the CPU until our next instance, with
2193  *   a new runtime. This is of little use now, since we
2194  *   don't have a bandwidth reclaiming mechanism. Anyway,
2195  *   bandwidth reclaiming is planned for the future, and
2196  *   yield_task_dl will indicate that some spare budget
2197  *   is available for other task instances to use it.
2198  */
yield_task_dl(struct rq * rq)2199 static void yield_task_dl(struct rq *rq)
2200 {
2201 	/*
2202 	 * We make the task go to sleep until its current deadline by
2203 	 * forcing its runtime to zero. This way, update_curr_dl() stops
2204 	 * it and the bandwidth timer will wake it up and will give it
2205 	 * new scheduling parameters (thanks to dl_yielded=1).
2206 	 */
2207 	rq->curr->dl.dl_yielded = 1;
2208 
2209 	update_rq_clock(rq);
2210 	update_curr_dl(rq);
2211 	/*
2212 	 * Tell update_rq_clock() that we've just updated,
2213 	 * so we don't do microscopic update in schedule()
2214 	 * and double the fastpath cost.
2215 	 */
2216 	rq_clock_skip_update(rq);
2217 }
2218 
2219 #ifdef CONFIG_SMP
2220 
dl_task_is_earliest_deadline(struct task_struct * p,struct rq * rq)2221 static inline bool dl_task_is_earliest_deadline(struct task_struct *p,
2222 						 struct rq *rq)
2223 {
2224 	return (!rq->dl.dl_nr_running ||
2225 		dl_time_before(p->dl.deadline,
2226 			       rq->dl.earliest_dl.curr));
2227 }
2228 
2229 static int find_later_rq(struct task_struct *task);
2230 
2231 static int
select_task_rq_dl(struct task_struct * p,int cpu,int flags)2232 select_task_rq_dl(struct task_struct *p, int cpu, int flags)
2233 {
2234 	struct task_struct *curr, *donor;
2235 	bool select_rq;
2236 	struct rq *rq;
2237 
2238 	if (!(flags & WF_TTWU))
2239 		goto out;
2240 
2241 	rq = cpu_rq(cpu);
2242 
2243 	rcu_read_lock();
2244 	curr = READ_ONCE(rq->curr); /* unlocked access */
2245 	donor = READ_ONCE(rq->donor);
2246 
2247 	/*
2248 	 * If we are dealing with a -deadline task, we must
2249 	 * decide where to wake it up.
2250 	 * If it has a later deadline and the current task
2251 	 * on this rq can't move (provided the waking task
2252 	 * can!) we prefer to send it somewhere else. On the
2253 	 * other hand, if it has a shorter deadline, we
2254 	 * try to make it stay here, it might be important.
2255 	 */
2256 	select_rq = unlikely(dl_task(donor)) &&
2257 		    (curr->nr_cpus_allowed < 2 ||
2258 		     !dl_entity_preempt(&p->dl, &donor->dl)) &&
2259 		    p->nr_cpus_allowed > 1;
2260 
2261 	/*
2262 	 * Take the capacity of the CPU into account to
2263 	 * ensure it fits the requirement of the task.
2264 	 */
2265 	if (sched_asym_cpucap_active())
2266 		select_rq |= !dl_task_fits_capacity(p, cpu);
2267 
2268 	if (select_rq) {
2269 		int target = find_later_rq(p);
2270 
2271 		if (target != -1 &&
2272 		    dl_task_is_earliest_deadline(p, cpu_rq(target)))
2273 			cpu = target;
2274 	}
2275 	rcu_read_unlock();
2276 
2277 out:
2278 	return cpu;
2279 }
2280 
migrate_task_rq_dl(struct task_struct * p,int new_cpu __maybe_unused)2281 static void migrate_task_rq_dl(struct task_struct *p, int new_cpu __maybe_unused)
2282 {
2283 	struct rq_flags rf;
2284 	struct rq *rq;
2285 
2286 	if (READ_ONCE(p->__state) != TASK_WAKING)
2287 		return;
2288 
2289 	rq = task_rq(p);
2290 	/*
2291 	 * Since p->state == TASK_WAKING, set_task_cpu() has been called
2292 	 * from try_to_wake_up(). Hence, p->pi_lock is locked, but
2293 	 * rq->lock is not... So, lock it
2294 	 */
2295 	rq_lock(rq, &rf);
2296 	if (p->dl.dl_non_contending) {
2297 		update_rq_clock(rq);
2298 		sub_running_bw(&p->dl, &rq->dl);
2299 		p->dl.dl_non_contending = 0;
2300 		/*
2301 		 * If the timer handler is currently running and the
2302 		 * timer cannot be canceled, inactive_task_timer()
2303 		 * will see that dl_not_contending is not set, and
2304 		 * will not touch the rq's active utilization,
2305 		 * so we are still safe.
2306 		 */
2307 		cancel_inactive_timer(&p->dl);
2308 	}
2309 	sub_rq_bw(&p->dl, &rq->dl);
2310 	rq_unlock(rq, &rf);
2311 }
2312 
check_preempt_equal_dl(struct rq * rq,struct task_struct * p)2313 static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
2314 {
2315 	/*
2316 	 * Current can't be migrated, useless to reschedule,
2317 	 * let's hope p can move out.
2318 	 */
2319 	if (rq->curr->nr_cpus_allowed == 1 ||
2320 	    !cpudl_find(&rq->rd->cpudl, rq->donor, NULL))
2321 		return;
2322 
2323 	/*
2324 	 * p is migratable, so let's not schedule it and
2325 	 * see if it is pushed or pulled somewhere else.
2326 	 */
2327 	if (p->nr_cpus_allowed != 1 &&
2328 	    cpudl_find(&rq->rd->cpudl, p, NULL))
2329 		return;
2330 
2331 	resched_curr(rq);
2332 }
2333 
balance_dl(struct rq * rq,struct task_struct * p,struct rq_flags * rf)2334 static int balance_dl(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
2335 {
2336 	if (!on_dl_rq(&p->dl) && need_pull_dl_task(rq, p)) {
2337 		/*
2338 		 * This is OK, because current is on_cpu, which avoids it being
2339 		 * picked for load-balance and preemption/IRQs are still
2340 		 * disabled avoiding further scheduler activity on it and we've
2341 		 * not yet started the picking loop.
2342 		 */
2343 		rq_unpin_lock(rq, rf);
2344 		pull_dl_task(rq);
2345 		rq_repin_lock(rq, rf);
2346 	}
2347 
2348 	return sched_stop_runnable(rq) || sched_dl_runnable(rq);
2349 }
2350 #endif /* CONFIG_SMP */
2351 
2352 /*
2353  * Only called when both the current and waking task are -deadline
2354  * tasks.
2355  */
wakeup_preempt_dl(struct rq * rq,struct task_struct * p,int flags)2356 static void wakeup_preempt_dl(struct rq *rq, struct task_struct *p,
2357 				  int flags)
2358 {
2359 	if (dl_entity_preempt(&p->dl, &rq->donor->dl)) {
2360 		resched_curr(rq);
2361 		return;
2362 	}
2363 
2364 #ifdef CONFIG_SMP
2365 	/*
2366 	 * In the unlikely case current and p have the same deadline
2367 	 * let us try to decide what's the best thing to do...
2368 	 */
2369 	if ((p->dl.deadline == rq->donor->dl.deadline) &&
2370 	    !test_tsk_need_resched(rq->curr))
2371 		check_preempt_equal_dl(rq, p);
2372 #endif /* CONFIG_SMP */
2373 }
2374 
2375 #ifdef CONFIG_SCHED_HRTICK
start_hrtick_dl(struct rq * rq,struct sched_dl_entity * dl_se)2376 static void start_hrtick_dl(struct rq *rq, struct sched_dl_entity *dl_se)
2377 {
2378 	hrtick_start(rq, dl_se->runtime);
2379 }
2380 #else /* !CONFIG_SCHED_HRTICK */
start_hrtick_dl(struct rq * rq,struct sched_dl_entity * dl_se)2381 static void start_hrtick_dl(struct rq *rq, struct sched_dl_entity *dl_se)
2382 {
2383 }
2384 #endif
2385 
set_next_task_dl(struct rq * rq,struct task_struct * p,bool first)2386 static void set_next_task_dl(struct rq *rq, struct task_struct *p, bool first)
2387 {
2388 	struct sched_dl_entity *dl_se = &p->dl;
2389 	struct dl_rq *dl_rq = &rq->dl;
2390 
2391 	p->se.exec_start = rq_clock_task(rq);
2392 	if (on_dl_rq(&p->dl))
2393 		update_stats_wait_end_dl(dl_rq, dl_se);
2394 
2395 	/* You can't push away the running task */
2396 	dequeue_pushable_dl_task(rq, p);
2397 
2398 	if (!first)
2399 		return;
2400 
2401 	if (rq->donor->sched_class != &dl_sched_class)
2402 		update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0);
2403 
2404 	deadline_queue_push_tasks(rq);
2405 
2406 	if (hrtick_enabled_dl(rq))
2407 		start_hrtick_dl(rq, &p->dl);
2408 }
2409 
pick_next_dl_entity(struct dl_rq * dl_rq)2410 static struct sched_dl_entity *pick_next_dl_entity(struct dl_rq *dl_rq)
2411 {
2412 	struct rb_node *left = rb_first_cached(&dl_rq->root);
2413 
2414 	if (!left)
2415 		return NULL;
2416 
2417 	return __node_2_dle(left);
2418 }
2419 
2420 /*
2421  * __pick_next_task_dl - Helper to pick the next -deadline task to run.
2422  * @rq: The runqueue to pick the next task from.
2423  */
__pick_task_dl(struct rq * rq)2424 static struct task_struct *__pick_task_dl(struct rq *rq)
2425 {
2426 	struct sched_dl_entity *dl_se;
2427 	struct dl_rq *dl_rq = &rq->dl;
2428 	struct task_struct *p;
2429 
2430 again:
2431 	if (!sched_dl_runnable(rq))
2432 		return NULL;
2433 
2434 	dl_se = pick_next_dl_entity(dl_rq);
2435 	WARN_ON_ONCE(!dl_se);
2436 
2437 	if (dl_server(dl_se)) {
2438 		p = dl_se->server_pick_task(dl_se);
2439 		if (!p) {
2440 			if (dl_server_active(dl_se)) {
2441 				dl_se->dl_yielded = 1;
2442 				update_curr_dl_se(rq, dl_se, 0);
2443 			}
2444 			goto again;
2445 		}
2446 		rq->dl_server = dl_se;
2447 	} else {
2448 		p = dl_task_of(dl_se);
2449 	}
2450 
2451 	return p;
2452 }
2453 
pick_task_dl(struct rq * rq)2454 static struct task_struct *pick_task_dl(struct rq *rq)
2455 {
2456 	return __pick_task_dl(rq);
2457 }
2458 
put_prev_task_dl(struct rq * rq,struct task_struct * p,struct task_struct * next)2459 static void put_prev_task_dl(struct rq *rq, struct task_struct *p, struct task_struct *next)
2460 {
2461 	struct sched_dl_entity *dl_se = &p->dl;
2462 	struct dl_rq *dl_rq = &rq->dl;
2463 
2464 	if (on_dl_rq(&p->dl))
2465 		update_stats_wait_start_dl(dl_rq, dl_se);
2466 
2467 	update_curr_dl(rq);
2468 
2469 	update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 1);
2470 	if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1)
2471 		enqueue_pushable_dl_task(rq, p);
2472 }
2473 
2474 /*
2475  * scheduler tick hitting a task of our scheduling class.
2476  *
2477  * NOTE: This function can be called remotely by the tick offload that
2478  * goes along full dynticks. Therefore no local assumption can be made
2479  * and everything must be accessed through the @rq and @curr passed in
2480  * parameters.
2481  */
task_tick_dl(struct rq * rq,struct task_struct * p,int queued)2482 static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued)
2483 {
2484 	update_curr_dl(rq);
2485 
2486 	update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 1);
2487 	/*
2488 	 * Even when we have runtime, update_curr_dl() might have resulted in us
2489 	 * not being the leftmost task anymore. In that case NEED_RESCHED will
2490 	 * be set and schedule() will start a new hrtick for the next task.
2491 	 */
2492 	if (hrtick_enabled_dl(rq) && queued && p->dl.runtime > 0 &&
2493 	    is_leftmost(&p->dl, &rq->dl))
2494 		start_hrtick_dl(rq, &p->dl);
2495 }
2496 
task_fork_dl(struct task_struct * p)2497 static void task_fork_dl(struct task_struct *p)
2498 {
2499 	/*
2500 	 * SCHED_DEADLINE tasks cannot fork and this is achieved through
2501 	 * sched_fork()
2502 	 */
2503 }
2504 
2505 #ifdef CONFIG_SMP
2506 
2507 /* Only try algorithms three times */
2508 #define DL_MAX_TRIES 3
2509 
2510 /*
2511  * Return the earliest pushable rq's task, which is suitable to be executed
2512  * on the CPU, NULL otherwise:
2513  */
pick_earliest_pushable_dl_task(struct rq * rq,int cpu)2514 static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq, int cpu)
2515 {
2516 	struct task_struct *p = NULL;
2517 	struct rb_node *next_node;
2518 
2519 	if (!has_pushable_dl_tasks(rq))
2520 		return NULL;
2521 
2522 	next_node = rb_first_cached(&rq->dl.pushable_dl_tasks_root);
2523 	while (next_node) {
2524 		p = __node_2_pdl(next_node);
2525 
2526 		if (task_is_pushable(rq, p, cpu))
2527 			return p;
2528 
2529 		next_node = rb_next(next_node);
2530 	}
2531 
2532 	return NULL;
2533 }
2534 
2535 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
2536 
find_later_rq(struct task_struct * task)2537 static int find_later_rq(struct task_struct *task)
2538 {
2539 	struct sched_domain *sd;
2540 	struct cpumask *later_mask = this_cpu_cpumask_var_ptr(local_cpu_mask_dl);
2541 	int this_cpu = smp_processor_id();
2542 	int cpu = task_cpu(task);
2543 
2544 	/* Make sure the mask is initialized first */
2545 	if (unlikely(!later_mask))
2546 		return -1;
2547 
2548 	if (task->nr_cpus_allowed == 1)
2549 		return -1;
2550 
2551 	/*
2552 	 * We have to consider system topology and task affinity
2553 	 * first, then we can look for a suitable CPU.
2554 	 */
2555 	if (!cpudl_find(&task_rq(task)->rd->cpudl, task, later_mask))
2556 		return -1;
2557 
2558 	/*
2559 	 * If we are here, some targets have been found, including
2560 	 * the most suitable which is, among the runqueues where the
2561 	 * current tasks have later deadlines than the task's one, the
2562 	 * rq with the latest possible one.
2563 	 *
2564 	 * Now we check how well this matches with task's
2565 	 * affinity and system topology.
2566 	 *
2567 	 * The last CPU where the task run is our first
2568 	 * guess, since it is most likely cache-hot there.
2569 	 */
2570 	if (cpumask_test_cpu(cpu, later_mask))
2571 		return cpu;
2572 	/*
2573 	 * Check if this_cpu is to be skipped (i.e., it is
2574 	 * not in the mask) or not.
2575 	 */
2576 	if (!cpumask_test_cpu(this_cpu, later_mask))
2577 		this_cpu = -1;
2578 
2579 	rcu_read_lock();
2580 	for_each_domain(cpu, sd) {
2581 		if (sd->flags & SD_WAKE_AFFINE) {
2582 			int best_cpu;
2583 
2584 			/*
2585 			 * If possible, preempting this_cpu is
2586 			 * cheaper than migrating.
2587 			 */
2588 			if (this_cpu != -1 &&
2589 			    cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
2590 				rcu_read_unlock();
2591 				return this_cpu;
2592 			}
2593 
2594 			best_cpu = cpumask_any_and_distribute(later_mask,
2595 							      sched_domain_span(sd));
2596 			/*
2597 			 * Last chance: if a CPU being in both later_mask
2598 			 * and current sd span is valid, that becomes our
2599 			 * choice. Of course, the latest possible CPU is
2600 			 * already under consideration through later_mask.
2601 			 */
2602 			if (best_cpu < nr_cpu_ids) {
2603 				rcu_read_unlock();
2604 				return best_cpu;
2605 			}
2606 		}
2607 	}
2608 	rcu_read_unlock();
2609 
2610 	/*
2611 	 * At this point, all our guesses failed, we just return
2612 	 * 'something', and let the caller sort the things out.
2613 	 */
2614 	if (this_cpu != -1)
2615 		return this_cpu;
2616 
2617 	cpu = cpumask_any_distribute(later_mask);
2618 	if (cpu < nr_cpu_ids)
2619 		return cpu;
2620 
2621 	return -1;
2622 }
2623 
2624 /* Locks the rq it finds */
find_lock_later_rq(struct task_struct * task,struct rq * rq)2625 static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
2626 {
2627 	struct rq *later_rq = NULL;
2628 	int tries;
2629 	int cpu;
2630 
2631 	for (tries = 0; tries < DL_MAX_TRIES; tries++) {
2632 		cpu = find_later_rq(task);
2633 
2634 		if ((cpu == -1) || (cpu == rq->cpu))
2635 			break;
2636 
2637 		later_rq = cpu_rq(cpu);
2638 
2639 		if (!dl_task_is_earliest_deadline(task, later_rq)) {
2640 			/*
2641 			 * Target rq has tasks of equal or earlier deadline,
2642 			 * retrying does not release any lock and is unlikely
2643 			 * to yield a different result.
2644 			 */
2645 			later_rq = NULL;
2646 			break;
2647 		}
2648 
2649 		/* Retry if something changed. */
2650 		if (double_lock_balance(rq, later_rq)) {
2651 			if (unlikely(task_rq(task) != rq ||
2652 				     !cpumask_test_cpu(later_rq->cpu, &task->cpus_mask) ||
2653 				     task_on_cpu(rq, task) ||
2654 				     !dl_task(task) ||
2655 				     is_migration_disabled(task) ||
2656 				     !task_on_rq_queued(task))) {
2657 				double_unlock_balance(rq, later_rq);
2658 				later_rq = NULL;
2659 				break;
2660 			}
2661 		}
2662 
2663 		/*
2664 		 * If the rq we found has no -deadline task, or
2665 		 * its earliest one has a later deadline than our
2666 		 * task, the rq is a good one.
2667 		 */
2668 		if (dl_task_is_earliest_deadline(task, later_rq))
2669 			break;
2670 
2671 		/* Otherwise we try again. */
2672 		double_unlock_balance(rq, later_rq);
2673 		later_rq = NULL;
2674 	}
2675 
2676 	return later_rq;
2677 }
2678 
pick_next_pushable_dl_task(struct rq * rq)2679 static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
2680 {
2681 	struct task_struct *p;
2682 
2683 	if (!has_pushable_dl_tasks(rq))
2684 		return NULL;
2685 
2686 	p = __node_2_pdl(rb_first_cached(&rq->dl.pushable_dl_tasks_root));
2687 
2688 	WARN_ON_ONCE(rq->cpu != task_cpu(p));
2689 	WARN_ON_ONCE(task_current(rq, p));
2690 	WARN_ON_ONCE(p->nr_cpus_allowed <= 1);
2691 
2692 	WARN_ON_ONCE(!task_on_rq_queued(p));
2693 	WARN_ON_ONCE(!dl_task(p));
2694 
2695 	return p;
2696 }
2697 
2698 /*
2699  * See if the non running -deadline tasks on this rq
2700  * can be sent to some other CPU where they can preempt
2701  * and start executing.
2702  */
push_dl_task(struct rq * rq)2703 static int push_dl_task(struct rq *rq)
2704 {
2705 	struct task_struct *next_task;
2706 	struct rq *later_rq;
2707 	int ret = 0;
2708 
2709 	next_task = pick_next_pushable_dl_task(rq);
2710 	if (!next_task)
2711 		return 0;
2712 
2713 retry:
2714 	/*
2715 	 * If next_task preempts rq->curr, and rq->curr
2716 	 * can move away, it makes sense to just reschedule
2717 	 * without going further in pushing next_task.
2718 	 */
2719 	if (dl_task(rq->donor) &&
2720 	    dl_time_before(next_task->dl.deadline, rq->donor->dl.deadline) &&
2721 	    rq->curr->nr_cpus_allowed > 1) {
2722 		resched_curr(rq);
2723 		return 0;
2724 	}
2725 
2726 	if (is_migration_disabled(next_task))
2727 		return 0;
2728 
2729 	if (WARN_ON(next_task == rq->curr))
2730 		return 0;
2731 
2732 	/* We might release rq lock */
2733 	get_task_struct(next_task);
2734 
2735 	/* Will lock the rq it'll find */
2736 	later_rq = find_lock_later_rq(next_task, rq);
2737 	if (!later_rq) {
2738 		struct task_struct *task;
2739 
2740 		/*
2741 		 * We must check all this again, since
2742 		 * find_lock_later_rq releases rq->lock and it is
2743 		 * then possible that next_task has migrated.
2744 		 */
2745 		task = pick_next_pushable_dl_task(rq);
2746 		if (task == next_task) {
2747 			/*
2748 			 * The task is still there. We don't try
2749 			 * again, some other CPU will pull it when ready.
2750 			 */
2751 			goto out;
2752 		}
2753 
2754 		if (!task)
2755 			/* No more tasks */
2756 			goto out;
2757 
2758 		put_task_struct(next_task);
2759 		next_task = task;
2760 		goto retry;
2761 	}
2762 
2763 	move_queued_task_locked(rq, later_rq, next_task);
2764 	ret = 1;
2765 
2766 	resched_curr(later_rq);
2767 
2768 	double_unlock_balance(rq, later_rq);
2769 
2770 out:
2771 	put_task_struct(next_task);
2772 
2773 	return ret;
2774 }
2775 
push_dl_tasks(struct rq * rq)2776 static void push_dl_tasks(struct rq *rq)
2777 {
2778 	/* push_dl_task() will return true if it moved a -deadline task */
2779 	while (push_dl_task(rq))
2780 		;
2781 }
2782 
pull_dl_task(struct rq * this_rq)2783 static void pull_dl_task(struct rq *this_rq)
2784 {
2785 	int this_cpu = this_rq->cpu, cpu;
2786 	struct task_struct *p, *push_task;
2787 	bool resched = false;
2788 	struct rq *src_rq;
2789 	u64 dmin = LONG_MAX;
2790 
2791 	if (likely(!dl_overloaded(this_rq)))
2792 		return;
2793 
2794 	/*
2795 	 * Match the barrier from dl_set_overloaded; this guarantees that if we
2796 	 * see overloaded we must also see the dlo_mask bit.
2797 	 */
2798 	smp_rmb();
2799 
2800 	for_each_cpu(cpu, this_rq->rd->dlo_mask) {
2801 		if (this_cpu == cpu)
2802 			continue;
2803 
2804 		src_rq = cpu_rq(cpu);
2805 
2806 		/*
2807 		 * It looks racy, and it is! However, as in sched_rt.c,
2808 		 * we are fine with this.
2809 		 */
2810 		if (this_rq->dl.dl_nr_running &&
2811 		    dl_time_before(this_rq->dl.earliest_dl.curr,
2812 				   src_rq->dl.earliest_dl.next))
2813 			continue;
2814 
2815 		/* Might drop this_rq->lock */
2816 		push_task = NULL;
2817 		double_lock_balance(this_rq, src_rq);
2818 
2819 		/*
2820 		 * If there are no more pullable tasks on the
2821 		 * rq, we're done with it.
2822 		 */
2823 		if (src_rq->dl.dl_nr_running <= 1)
2824 			goto skip;
2825 
2826 		p = pick_earliest_pushable_dl_task(src_rq, this_cpu);
2827 
2828 		/*
2829 		 * We found a task to be pulled if:
2830 		 *  - it preempts our current (if there's one),
2831 		 *  - it will preempt the last one we pulled (if any).
2832 		 */
2833 		if (p && dl_time_before(p->dl.deadline, dmin) &&
2834 		    dl_task_is_earliest_deadline(p, this_rq)) {
2835 			WARN_ON(p == src_rq->curr);
2836 			WARN_ON(!task_on_rq_queued(p));
2837 
2838 			/*
2839 			 * Then we pull iff p has actually an earlier
2840 			 * deadline than the current task of its runqueue.
2841 			 */
2842 			if (dl_time_before(p->dl.deadline,
2843 					   src_rq->donor->dl.deadline))
2844 				goto skip;
2845 
2846 			if (is_migration_disabled(p)) {
2847 				push_task = get_push_task(src_rq);
2848 			} else {
2849 				move_queued_task_locked(src_rq, this_rq, p);
2850 				dmin = p->dl.deadline;
2851 				resched = true;
2852 			}
2853 
2854 			/* Is there any other task even earlier? */
2855 		}
2856 skip:
2857 		double_unlock_balance(this_rq, src_rq);
2858 
2859 		if (push_task) {
2860 			preempt_disable();
2861 			raw_spin_rq_unlock(this_rq);
2862 			stop_one_cpu_nowait(src_rq->cpu, push_cpu_stop,
2863 					    push_task, &src_rq->push_work);
2864 			preempt_enable();
2865 			raw_spin_rq_lock(this_rq);
2866 		}
2867 	}
2868 
2869 	if (resched)
2870 		resched_curr(this_rq);
2871 }
2872 
2873 /*
2874  * Since the task is not running and a reschedule is not going to happen
2875  * anytime soon on its runqueue, we try pushing it away now.
2876  */
task_woken_dl(struct rq * rq,struct task_struct * p)2877 static void task_woken_dl(struct rq *rq, struct task_struct *p)
2878 {
2879 	if (!task_on_cpu(rq, p) &&
2880 	    !test_tsk_need_resched(rq->curr) &&
2881 	    p->nr_cpus_allowed > 1 &&
2882 	    dl_task(rq->donor) &&
2883 	    (rq->curr->nr_cpus_allowed < 2 ||
2884 	     !dl_entity_preempt(&p->dl, &rq->donor->dl))) {
2885 		push_dl_tasks(rq);
2886 	}
2887 }
2888 
set_cpus_allowed_dl(struct task_struct * p,struct affinity_context * ctx)2889 static void set_cpus_allowed_dl(struct task_struct *p,
2890 				struct affinity_context *ctx)
2891 {
2892 	struct root_domain *src_rd;
2893 	struct rq *rq;
2894 
2895 	WARN_ON_ONCE(!dl_task(p));
2896 
2897 	rq = task_rq(p);
2898 	src_rd = rq->rd;
2899 	/*
2900 	 * Migrating a SCHED_DEADLINE task between exclusive
2901 	 * cpusets (different root_domains) entails a bandwidth
2902 	 * update. We already made space for us in the destination
2903 	 * domain (see cpuset_can_attach()).
2904 	 */
2905 	if (!cpumask_intersects(src_rd->span, ctx->new_mask)) {
2906 		struct dl_bw *src_dl_b;
2907 
2908 		src_dl_b = dl_bw_of(cpu_of(rq));
2909 		/*
2910 		 * We now free resources of the root_domain we are migrating
2911 		 * off. In the worst case, sched_setattr() may temporary fail
2912 		 * until we complete the update.
2913 		 */
2914 		raw_spin_lock(&src_dl_b->lock);
2915 		__dl_sub(src_dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
2916 		raw_spin_unlock(&src_dl_b->lock);
2917 	}
2918 
2919 	set_cpus_allowed_common(p, ctx);
2920 }
2921 
2922 /* Assumes rq->lock is held */
rq_online_dl(struct rq * rq)2923 static void rq_online_dl(struct rq *rq)
2924 {
2925 	if (rq->dl.overloaded)
2926 		dl_set_overload(rq);
2927 
2928 	cpudl_set_freecpu(&rq->rd->cpudl, rq->cpu);
2929 	if (rq->dl.dl_nr_running > 0)
2930 		cpudl_set(&rq->rd->cpudl, rq->cpu, rq->dl.earliest_dl.curr);
2931 }
2932 
2933 /* Assumes rq->lock is held */
rq_offline_dl(struct rq * rq)2934 static void rq_offline_dl(struct rq *rq)
2935 {
2936 	if (rq->dl.overloaded)
2937 		dl_clear_overload(rq);
2938 
2939 	cpudl_clear(&rq->rd->cpudl, rq->cpu);
2940 	cpudl_clear_freecpu(&rq->rd->cpudl, rq->cpu);
2941 }
2942 
init_sched_dl_class(void)2943 void __init init_sched_dl_class(void)
2944 {
2945 	unsigned int i;
2946 
2947 	for_each_possible_cpu(i)
2948 		zalloc_cpumask_var_node(&per_cpu(local_cpu_mask_dl, i),
2949 					GFP_KERNEL, cpu_to_node(i));
2950 }
2951 
dl_add_task_root_domain(struct task_struct * p)2952 void dl_add_task_root_domain(struct task_struct *p)
2953 {
2954 	struct rq_flags rf;
2955 	struct rq *rq;
2956 	struct dl_bw *dl_b;
2957 
2958 	raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
2959 	if (!dl_task(p)) {
2960 		raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags);
2961 		return;
2962 	}
2963 
2964 	rq = __task_rq_lock(p, &rf);
2965 
2966 	dl_b = &rq->rd->dl_bw;
2967 	raw_spin_lock(&dl_b->lock);
2968 
2969 	__dl_add(dl_b, p->dl.dl_bw, cpumask_weight(rq->rd->span));
2970 
2971 	raw_spin_unlock(&dl_b->lock);
2972 
2973 	task_rq_unlock(rq, p, &rf);
2974 }
2975 
dl_clear_root_domain(struct root_domain * rd)2976 void dl_clear_root_domain(struct root_domain *rd)
2977 {
2978 	int i;
2979 
2980 	guard(raw_spinlock_irqsave)(&rd->dl_bw.lock);
2981 	rd->dl_bw.total_bw = 0;
2982 
2983 	/*
2984 	 * dl_server bandwidth is only restored when CPUs are attached to root
2985 	 * domains (after domains are created or CPUs moved back to the
2986 	 * default root doamin).
2987 	 */
2988 	for_each_cpu(i, rd->span) {
2989 		struct sched_dl_entity *dl_se = &cpu_rq(i)->fair_server;
2990 
2991 		if (dl_server(dl_se) && cpu_active(i))
2992 			rd->dl_bw.total_bw += dl_se->dl_bw;
2993 	}
2994 }
2995 
2996 #endif /* CONFIG_SMP */
2997 
switched_from_dl(struct rq * rq,struct task_struct * p)2998 static void switched_from_dl(struct rq *rq, struct task_struct *p)
2999 {
3000 	/*
3001 	 * task_non_contending() can start the "inactive timer" (if the 0-lag
3002 	 * time is in the future). If the task switches back to dl before
3003 	 * the "inactive timer" fires, it can continue to consume its current
3004 	 * runtime using its current deadline. If it stays outside of
3005 	 * SCHED_DEADLINE until the 0-lag time passes, inactive_task_timer()
3006 	 * will reset the task parameters.
3007 	 */
3008 	if (task_on_rq_queued(p) && p->dl.dl_runtime)
3009 		task_non_contending(&p->dl);
3010 
3011 	/*
3012 	 * In case a task is setscheduled out from SCHED_DEADLINE we need to
3013 	 * keep track of that on its cpuset (for correct bandwidth tracking).
3014 	 */
3015 	dec_dl_tasks_cs(p);
3016 
3017 	if (!task_on_rq_queued(p)) {
3018 		/*
3019 		 * Inactive timer is armed. However, p is leaving DEADLINE and
3020 		 * might migrate away from this rq while continuing to run on
3021 		 * some other class. We need to remove its contribution from
3022 		 * this rq running_bw now, or sub_rq_bw (below) will complain.
3023 		 */
3024 		if (p->dl.dl_non_contending)
3025 			sub_running_bw(&p->dl, &rq->dl);
3026 		sub_rq_bw(&p->dl, &rq->dl);
3027 	}
3028 
3029 	/*
3030 	 * We cannot use inactive_task_timer() to invoke sub_running_bw()
3031 	 * at the 0-lag time, because the task could have been migrated
3032 	 * while SCHED_OTHER in the meanwhile.
3033 	 */
3034 	if (p->dl.dl_non_contending)
3035 		p->dl.dl_non_contending = 0;
3036 
3037 	/*
3038 	 * Since this might be the only -deadline task on the rq,
3039 	 * this is the right place to try to pull some other one
3040 	 * from an overloaded CPU, if any.
3041 	 */
3042 	if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
3043 		return;
3044 
3045 	deadline_queue_pull_task(rq);
3046 }
3047 
3048 /*
3049  * When switching to -deadline, we may overload the rq, then
3050  * we try to push someone off, if possible.
3051  */
switched_to_dl(struct rq * rq,struct task_struct * p)3052 static void switched_to_dl(struct rq *rq, struct task_struct *p)
3053 {
3054 	cancel_inactive_timer(&p->dl);
3055 
3056 	/*
3057 	 * In case a task is setscheduled to SCHED_DEADLINE we need to keep
3058 	 * track of that on its cpuset (for correct bandwidth tracking).
3059 	 */
3060 	inc_dl_tasks_cs(p);
3061 
3062 	/* If p is not queued we will update its parameters at next wakeup. */
3063 	if (!task_on_rq_queued(p)) {
3064 		add_rq_bw(&p->dl, &rq->dl);
3065 
3066 		return;
3067 	}
3068 
3069 	if (rq->donor != p) {
3070 #ifdef CONFIG_SMP
3071 		if (p->nr_cpus_allowed > 1 && rq->dl.overloaded)
3072 			deadline_queue_push_tasks(rq);
3073 #endif
3074 		if (dl_task(rq->donor))
3075 			wakeup_preempt_dl(rq, p, 0);
3076 		else
3077 			resched_curr(rq);
3078 	} else {
3079 		update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0);
3080 	}
3081 }
3082 
3083 /*
3084  * If the scheduling parameters of a -deadline task changed,
3085  * a push or pull operation might be needed.
3086  */
prio_changed_dl(struct rq * rq,struct task_struct * p,int oldprio)3087 static void prio_changed_dl(struct rq *rq, struct task_struct *p,
3088 			    int oldprio)
3089 {
3090 	if (!task_on_rq_queued(p))
3091 		return;
3092 
3093 #ifdef CONFIG_SMP
3094 	/*
3095 	 * This might be too much, but unfortunately
3096 	 * we don't have the old deadline value, and
3097 	 * we can't argue if the task is increasing
3098 	 * or lowering its prio, so...
3099 	 */
3100 	if (!rq->dl.overloaded)
3101 		deadline_queue_pull_task(rq);
3102 
3103 	if (task_current_donor(rq, p)) {
3104 		/*
3105 		 * If we now have a earlier deadline task than p,
3106 		 * then reschedule, provided p is still on this
3107 		 * runqueue.
3108 		 */
3109 		if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline))
3110 			resched_curr(rq);
3111 	} else {
3112 		/*
3113 		 * Current may not be deadline in case p was throttled but we
3114 		 * have just replenished it (e.g. rt_mutex_setprio()).
3115 		 *
3116 		 * Otherwise, if p was given an earlier deadline, reschedule.
3117 		 */
3118 		if (!dl_task(rq->curr) ||
3119 		    dl_time_before(p->dl.deadline, rq->curr->dl.deadline))
3120 			resched_curr(rq);
3121 	}
3122 #else
3123 	/*
3124 	 * We don't know if p has a earlier or later deadline, so let's blindly
3125 	 * set a (maybe not needed) rescheduling point.
3126 	 */
3127 	resched_curr(rq);
3128 #endif
3129 }
3130 
3131 #ifdef CONFIG_SCHED_CORE
task_is_throttled_dl(struct task_struct * p,int cpu)3132 static int task_is_throttled_dl(struct task_struct *p, int cpu)
3133 {
3134 	return p->dl.dl_throttled;
3135 }
3136 #endif
3137 
3138 DEFINE_SCHED_CLASS(dl) = {
3139 
3140 	.enqueue_task		= enqueue_task_dl,
3141 	.dequeue_task		= dequeue_task_dl,
3142 	.yield_task		= yield_task_dl,
3143 
3144 	.wakeup_preempt		= wakeup_preempt_dl,
3145 
3146 	.pick_task		= pick_task_dl,
3147 	.put_prev_task		= put_prev_task_dl,
3148 	.set_next_task		= set_next_task_dl,
3149 
3150 #ifdef CONFIG_SMP
3151 	.balance		= balance_dl,
3152 	.select_task_rq		= select_task_rq_dl,
3153 	.migrate_task_rq	= migrate_task_rq_dl,
3154 	.set_cpus_allowed       = set_cpus_allowed_dl,
3155 	.rq_online              = rq_online_dl,
3156 	.rq_offline             = rq_offline_dl,
3157 	.task_woken		= task_woken_dl,
3158 	.find_lock_rq		= find_lock_later_rq,
3159 #endif
3160 
3161 	.task_tick		= task_tick_dl,
3162 	.task_fork              = task_fork_dl,
3163 
3164 	.prio_changed           = prio_changed_dl,
3165 	.switched_from		= switched_from_dl,
3166 	.switched_to		= switched_to_dl,
3167 
3168 	.update_curr		= update_curr_dl,
3169 #ifdef CONFIG_SCHED_CORE
3170 	.task_is_throttled	= task_is_throttled_dl,
3171 #endif
3172 };
3173 
3174 /* Used for dl_bw check and update, used under sched_rt_handler()::mutex */
3175 static u64 dl_generation;
3176 
sched_dl_global_validate(void)3177 int sched_dl_global_validate(void)
3178 {
3179 	u64 runtime = global_rt_runtime();
3180 	u64 period = global_rt_period();
3181 	u64 new_bw = to_ratio(period, runtime);
3182 	u64 gen = ++dl_generation;
3183 	struct dl_bw *dl_b;
3184 	int cpu, cpus, ret = 0;
3185 	unsigned long flags;
3186 
3187 	/*
3188 	 * Here we want to check the bandwidth not being set to some
3189 	 * value smaller than the currently allocated bandwidth in
3190 	 * any of the root_domains.
3191 	 */
3192 	for_each_possible_cpu(cpu) {
3193 		rcu_read_lock_sched();
3194 
3195 		if (dl_bw_visited(cpu, gen))
3196 			goto next;
3197 
3198 		dl_b = dl_bw_of(cpu);
3199 		cpus = dl_bw_cpus(cpu);
3200 
3201 		raw_spin_lock_irqsave(&dl_b->lock, flags);
3202 		if (new_bw * cpus < dl_b->total_bw)
3203 			ret = -EBUSY;
3204 		raw_spin_unlock_irqrestore(&dl_b->lock, flags);
3205 
3206 next:
3207 		rcu_read_unlock_sched();
3208 
3209 		if (ret)
3210 			break;
3211 	}
3212 
3213 	return ret;
3214 }
3215 
init_dl_rq_bw_ratio(struct dl_rq * dl_rq)3216 static void init_dl_rq_bw_ratio(struct dl_rq *dl_rq)
3217 {
3218 	if (global_rt_runtime() == RUNTIME_INF) {
3219 		dl_rq->bw_ratio = 1 << RATIO_SHIFT;
3220 		dl_rq->max_bw = dl_rq->extra_bw = 1 << BW_SHIFT;
3221 	} else {
3222 		dl_rq->bw_ratio = to_ratio(global_rt_runtime(),
3223 			  global_rt_period()) >> (BW_SHIFT - RATIO_SHIFT);
3224 		dl_rq->max_bw = dl_rq->extra_bw =
3225 			to_ratio(global_rt_period(), global_rt_runtime());
3226 	}
3227 }
3228 
sched_dl_do_global(void)3229 void sched_dl_do_global(void)
3230 {
3231 	u64 new_bw = -1;
3232 	u64 gen = ++dl_generation;
3233 	struct dl_bw *dl_b;
3234 	int cpu;
3235 	unsigned long flags;
3236 
3237 	if (global_rt_runtime() != RUNTIME_INF)
3238 		new_bw = to_ratio(global_rt_period(), global_rt_runtime());
3239 
3240 	for_each_possible_cpu(cpu) {
3241 		rcu_read_lock_sched();
3242 
3243 		if (dl_bw_visited(cpu, gen)) {
3244 			rcu_read_unlock_sched();
3245 			continue;
3246 		}
3247 
3248 		dl_b = dl_bw_of(cpu);
3249 
3250 		raw_spin_lock_irqsave(&dl_b->lock, flags);
3251 		dl_b->bw = new_bw;
3252 		raw_spin_unlock_irqrestore(&dl_b->lock, flags);
3253 
3254 		rcu_read_unlock_sched();
3255 		init_dl_rq_bw_ratio(&cpu_rq(cpu)->dl);
3256 	}
3257 }
3258 
3259 /*
3260  * We must be sure that accepting a new task (or allowing changing the
3261  * parameters of an existing one) is consistent with the bandwidth
3262  * constraints. If yes, this function also accordingly updates the currently
3263  * allocated bandwidth to reflect the new situation.
3264  *
3265  * This function is called while holding p's rq->lock.
3266  */
sched_dl_overflow(struct task_struct * p,int policy,const struct sched_attr * attr)3267 int sched_dl_overflow(struct task_struct *p, int policy,
3268 		      const struct sched_attr *attr)
3269 {
3270 	u64 period = attr->sched_period ?: attr->sched_deadline;
3271 	u64 runtime = attr->sched_runtime;
3272 	u64 new_bw = dl_policy(policy) ? to_ratio(period, runtime) : 0;
3273 	int cpus, err = -1, cpu = task_cpu(p);
3274 	struct dl_bw *dl_b = dl_bw_of(cpu);
3275 	unsigned long cap;
3276 
3277 	if (attr->sched_flags & SCHED_FLAG_SUGOV)
3278 		return 0;
3279 
3280 	/* !deadline task may carry old deadline bandwidth */
3281 	if (new_bw == p->dl.dl_bw && task_has_dl_policy(p))
3282 		return 0;
3283 
3284 	/*
3285 	 * Either if a task, enters, leave, or stays -deadline but changes
3286 	 * its parameters, we may need to update accordingly the total
3287 	 * allocated bandwidth of the container.
3288 	 */
3289 	raw_spin_lock(&dl_b->lock);
3290 	cpus = dl_bw_cpus(cpu);
3291 	cap = dl_bw_capacity(cpu);
3292 
3293 	if (dl_policy(policy) && !task_has_dl_policy(p) &&
3294 	    !__dl_overflow(dl_b, cap, 0, new_bw)) {
3295 		if (hrtimer_active(&p->dl.inactive_timer))
3296 			__dl_sub(dl_b, p->dl.dl_bw, cpus);
3297 		__dl_add(dl_b, new_bw, cpus);
3298 		err = 0;
3299 	} else if (dl_policy(policy) && task_has_dl_policy(p) &&
3300 		   !__dl_overflow(dl_b, cap, p->dl.dl_bw, new_bw)) {
3301 		/*
3302 		 * XXX this is slightly incorrect: when the task
3303 		 * utilization decreases, we should delay the total
3304 		 * utilization change until the task's 0-lag point.
3305 		 * But this would require to set the task's "inactive
3306 		 * timer" when the task is not inactive.
3307 		 */
3308 		__dl_sub(dl_b, p->dl.dl_bw, cpus);
3309 		__dl_add(dl_b, new_bw, cpus);
3310 		dl_change_utilization(p, new_bw);
3311 		err = 0;
3312 	} else if (!dl_policy(policy) && task_has_dl_policy(p)) {
3313 		/*
3314 		 * Do not decrease the total deadline utilization here,
3315 		 * switched_from_dl() will take care to do it at the correct
3316 		 * (0-lag) time.
3317 		 */
3318 		err = 0;
3319 	}
3320 	raw_spin_unlock(&dl_b->lock);
3321 
3322 	return err;
3323 }
3324 
3325 /*
3326  * This function initializes the sched_dl_entity of a newly becoming
3327  * SCHED_DEADLINE task.
3328  *
3329  * Only the static values are considered here, the actual runtime and the
3330  * absolute deadline will be properly calculated when the task is enqueued
3331  * for the first time with its new policy.
3332  */
__setparam_dl(struct task_struct * p,const struct sched_attr * attr)3333 void __setparam_dl(struct task_struct *p, const struct sched_attr *attr)
3334 {
3335 	struct sched_dl_entity *dl_se = &p->dl;
3336 
3337 	dl_se->dl_runtime = attr->sched_runtime;
3338 	dl_se->dl_deadline = attr->sched_deadline;
3339 	dl_se->dl_period = attr->sched_period ?: dl_se->dl_deadline;
3340 	dl_se->flags = attr->sched_flags & SCHED_DL_FLAGS;
3341 	dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime);
3342 	dl_se->dl_density = to_ratio(dl_se->dl_deadline, dl_se->dl_runtime);
3343 }
3344 
__getparam_dl(struct task_struct * p,struct sched_attr * attr)3345 void __getparam_dl(struct task_struct *p, struct sched_attr *attr)
3346 {
3347 	struct sched_dl_entity *dl_se = &p->dl;
3348 
3349 	attr->sched_priority = p->rt_priority;
3350 	attr->sched_runtime = dl_se->dl_runtime;
3351 	attr->sched_deadline = dl_se->dl_deadline;
3352 	attr->sched_period = dl_se->dl_period;
3353 	attr->sched_flags &= ~SCHED_DL_FLAGS;
3354 	attr->sched_flags |= dl_se->flags;
3355 }
3356 
3357 /*
3358  * This function validates the new parameters of a -deadline task.
3359  * We ask for the deadline not being zero, and greater or equal
3360  * than the runtime, as well as the period of being zero or
3361  * greater than deadline. Furthermore, we have to be sure that
3362  * user parameters are above the internal resolution of 1us (we
3363  * check sched_runtime only since it is always the smaller one) and
3364  * below 2^63 ns (we have to check both sched_deadline and
3365  * sched_period, as the latter can be zero).
3366  */
__checkparam_dl(const struct sched_attr * attr)3367 bool __checkparam_dl(const struct sched_attr *attr)
3368 {
3369 	u64 period, max, min;
3370 
3371 	/* special dl tasks don't actually use any parameter */
3372 	if (attr->sched_flags & SCHED_FLAG_SUGOV)
3373 		return true;
3374 
3375 	/* deadline != 0 */
3376 	if (attr->sched_deadline == 0)
3377 		return false;
3378 
3379 	/*
3380 	 * Since we truncate DL_SCALE bits, make sure we're at least
3381 	 * that big.
3382 	 */
3383 	if (attr->sched_runtime < (1ULL << DL_SCALE))
3384 		return false;
3385 
3386 	/*
3387 	 * Since we use the MSB for wrap-around and sign issues, make
3388 	 * sure it's not set (mind that period can be equal to zero).
3389 	 */
3390 	if (attr->sched_deadline & (1ULL << 63) ||
3391 	    attr->sched_period & (1ULL << 63))
3392 		return false;
3393 
3394 	period = attr->sched_period;
3395 	if (!period)
3396 		period = attr->sched_deadline;
3397 
3398 	/* runtime <= deadline <= period (if period != 0) */
3399 	if (period < attr->sched_deadline ||
3400 	    attr->sched_deadline < attr->sched_runtime)
3401 		return false;
3402 
3403 	max = (u64)READ_ONCE(sysctl_sched_dl_period_max) * NSEC_PER_USEC;
3404 	min = (u64)READ_ONCE(sysctl_sched_dl_period_min) * NSEC_PER_USEC;
3405 
3406 	if (period < min || period > max)
3407 		return false;
3408 
3409 	return true;
3410 }
3411 
3412 /*
3413  * This function clears the sched_dl_entity static params.
3414  */
__dl_clear_params(struct sched_dl_entity * dl_se)3415 static void __dl_clear_params(struct sched_dl_entity *dl_se)
3416 {
3417 	dl_se->dl_runtime		= 0;
3418 	dl_se->dl_deadline		= 0;
3419 	dl_se->dl_period		= 0;
3420 	dl_se->flags			= 0;
3421 	dl_se->dl_bw			= 0;
3422 	dl_se->dl_density		= 0;
3423 
3424 	dl_se->dl_throttled		= 0;
3425 	dl_se->dl_yielded		= 0;
3426 	dl_se->dl_non_contending	= 0;
3427 	dl_se->dl_overrun		= 0;
3428 	dl_se->dl_server		= 0;
3429 
3430 #ifdef CONFIG_RT_MUTEXES
3431 	dl_se->pi_se			= dl_se;
3432 #endif
3433 }
3434 
init_dl_entity(struct sched_dl_entity * dl_se)3435 void init_dl_entity(struct sched_dl_entity *dl_se)
3436 {
3437 	RB_CLEAR_NODE(&dl_se->rb_node);
3438 	init_dl_task_timer(dl_se);
3439 	init_dl_inactive_task_timer(dl_se);
3440 	__dl_clear_params(dl_se);
3441 }
3442 
dl_param_changed(struct task_struct * p,const struct sched_attr * attr)3443 bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr)
3444 {
3445 	struct sched_dl_entity *dl_se = &p->dl;
3446 
3447 	if (dl_se->dl_runtime != attr->sched_runtime ||
3448 	    dl_se->dl_deadline != attr->sched_deadline ||
3449 	    dl_se->dl_period != attr->sched_period ||
3450 	    dl_se->flags != (attr->sched_flags & SCHED_DL_FLAGS))
3451 		return true;
3452 
3453 	return false;
3454 }
3455 
3456 #ifdef CONFIG_SMP
dl_cpuset_cpumask_can_shrink(const struct cpumask * cur,const struct cpumask * trial)3457 int dl_cpuset_cpumask_can_shrink(const struct cpumask *cur,
3458 				 const struct cpumask *trial)
3459 {
3460 	unsigned long flags, cap;
3461 	struct dl_bw *cur_dl_b;
3462 	int ret = 1;
3463 
3464 	rcu_read_lock_sched();
3465 	cur_dl_b = dl_bw_of(cpumask_any(cur));
3466 	cap = __dl_bw_capacity(trial);
3467 	raw_spin_lock_irqsave(&cur_dl_b->lock, flags);
3468 	if (__dl_overflow(cur_dl_b, cap, 0, 0))
3469 		ret = 0;
3470 	raw_spin_unlock_irqrestore(&cur_dl_b->lock, flags);
3471 	rcu_read_unlock_sched();
3472 
3473 	return ret;
3474 }
3475 
3476 enum dl_bw_request {
3477 	dl_bw_req_deactivate = 0,
3478 	dl_bw_req_alloc,
3479 	dl_bw_req_free
3480 };
3481 
dl_bw_manage(enum dl_bw_request req,int cpu,u64 dl_bw)3482 static int dl_bw_manage(enum dl_bw_request req, int cpu, u64 dl_bw)
3483 {
3484 	unsigned long flags, cap;
3485 	struct dl_bw *dl_b;
3486 	bool overflow = 0;
3487 	u64 fair_server_bw = 0;
3488 
3489 	rcu_read_lock_sched();
3490 	dl_b = dl_bw_of(cpu);
3491 	raw_spin_lock_irqsave(&dl_b->lock, flags);
3492 
3493 	cap = dl_bw_capacity(cpu);
3494 	switch (req) {
3495 	case dl_bw_req_free:
3496 		__dl_sub(dl_b, dl_bw, dl_bw_cpus(cpu));
3497 		break;
3498 	case dl_bw_req_alloc:
3499 		overflow = __dl_overflow(dl_b, cap, 0, dl_bw);
3500 
3501 		if (!overflow) {
3502 			/*
3503 			 * We reserve space in the destination
3504 			 * root_domain, as we can't fail after this point.
3505 			 * We will free resources in the source root_domain
3506 			 * later on (see set_cpus_allowed_dl()).
3507 			 */
3508 			__dl_add(dl_b, dl_bw, dl_bw_cpus(cpu));
3509 		}
3510 		break;
3511 	case dl_bw_req_deactivate:
3512 		/*
3513 		 * cpu is not off yet, but we need to do the math by
3514 		 * considering it off already (i.e., what would happen if we
3515 		 * turn cpu off?).
3516 		 */
3517 		cap -= arch_scale_cpu_capacity(cpu);
3518 
3519 		/*
3520 		 * cpu is going offline and NORMAL tasks will be moved away
3521 		 * from it. We can thus discount dl_server bandwidth
3522 		 * contribution as it won't need to be servicing tasks after
3523 		 * the cpu is off.
3524 		 */
3525 		if (cpu_rq(cpu)->fair_server.dl_server)
3526 			fair_server_bw = cpu_rq(cpu)->fair_server.dl_bw;
3527 
3528 		/*
3529 		 * Not much to check if no DEADLINE bandwidth is present.
3530 		 * dl_servers we can discount, as tasks will be moved out the
3531 		 * offlined CPUs anyway.
3532 		 */
3533 		if (dl_b->total_bw - fair_server_bw > 0) {
3534 			/*
3535 			 * Leaving at least one CPU for DEADLINE tasks seems a
3536 			 * wise thing to do. As said above, cpu is not offline
3537 			 * yet, so account for that.
3538 			 */
3539 			if (dl_bw_cpus(cpu) - 1)
3540 				overflow = __dl_overflow(dl_b, cap, fair_server_bw, 0);
3541 			else
3542 				overflow = 1;
3543 		}
3544 
3545 		break;
3546 	}
3547 
3548 	raw_spin_unlock_irqrestore(&dl_b->lock, flags);
3549 	rcu_read_unlock_sched();
3550 
3551 	return overflow ? -EBUSY : 0;
3552 }
3553 
dl_bw_deactivate(int cpu)3554 int dl_bw_deactivate(int cpu)
3555 {
3556 	return dl_bw_manage(dl_bw_req_deactivate, cpu, 0);
3557 }
3558 
dl_bw_alloc(int cpu,u64 dl_bw)3559 int dl_bw_alloc(int cpu, u64 dl_bw)
3560 {
3561 	return dl_bw_manage(dl_bw_req_alloc, cpu, dl_bw);
3562 }
3563 
dl_bw_free(int cpu,u64 dl_bw)3564 void dl_bw_free(int cpu, u64 dl_bw)
3565 {
3566 	dl_bw_manage(dl_bw_req_free, cpu, dl_bw);
3567 }
3568 #endif
3569 
3570 #ifdef CONFIG_SCHED_DEBUG
print_dl_stats(struct seq_file * m,int cpu)3571 void print_dl_stats(struct seq_file *m, int cpu)
3572 {
3573 	print_dl_rq(m, cpu, &cpu_rq(cpu)->dl);
3574 }
3575 #endif /* CONFIG_SCHED_DEBUG */
3576