1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
   4 * policies)
   5 */
 
   6#include "sched.h"
   7
 
 
 
   8int sched_rr_timeslice = RR_TIMESLICE;
   9int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;
  10
  11static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);
  12
  13struct rt_bandwidth def_rt_bandwidth;
  14
  15static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer)
  16{
  17	struct rt_bandwidth *rt_b =
  18		container_of(timer, struct rt_bandwidth, rt_period_timer);
  19	int idle = 0;
  20	int overrun;
  21
  22	raw_spin_lock(&rt_b->rt_runtime_lock);
  23	for (;;) {
  24		overrun = hrtimer_forward_now(timer, rt_b->rt_period);
  25		if (!overrun)
  26			break;
  27
  28		raw_spin_unlock(&rt_b->rt_runtime_lock);
  29		idle = do_sched_rt_period_timer(rt_b, overrun);
  30		raw_spin_lock(&rt_b->rt_runtime_lock);
  31	}
  32	if (idle)
  33		rt_b->rt_period_active = 0;
  34	raw_spin_unlock(&rt_b->rt_runtime_lock);
  35
  36	return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
  37}
  38
  39void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime)
  40{
  41	rt_b->rt_period = ns_to_ktime(period);
  42	rt_b->rt_runtime = runtime;
  43
  44	raw_spin_lock_init(&rt_b->rt_runtime_lock);
  45
  46	hrtimer_init(&rt_b->rt_period_timer,
  47			CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  48	rt_b->rt_period_timer.function = sched_rt_period_timer;
  49}
  50
  51static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
  52{
  53	if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
  54		return;
  55
  56	raw_spin_lock(&rt_b->rt_runtime_lock);
  57	if (!rt_b->rt_period_active) {
  58		rt_b->rt_period_active = 1;
  59		/*
  60		 * SCHED_DEADLINE updates the bandwidth, as a run away
  61		 * RT task with a DL task could hog a CPU. But DL does
  62		 * not reset the period. If a deadline task was running
  63		 * without an RT task running, it can cause RT tasks to
  64		 * throttle when they start up. Kick the timer right away
  65		 * to update the period.
  66		 */
  67		hrtimer_forward_now(&rt_b->rt_period_timer, ns_to_ktime(0));
  68		hrtimer_start_expires(&rt_b->rt_period_timer, HRTIMER_MODE_ABS_PINNED);
  69	}
  70	raw_spin_unlock(&rt_b->rt_runtime_lock);
  71}
  72
 
 
 
 
  73void init_rt_rq(struct rt_rq *rt_rq)
  74{
  75	struct rt_prio_array *array;
  76	int i;
  77
  78	array = &rt_rq->active;
  79	for (i = 0; i < MAX_RT_PRIO; i++) {
  80		INIT_LIST_HEAD(array->queue + i);
  81		__clear_bit(i, array->bitmap);
  82	}
  83	/* delimiter for bitsearch: */
  84	__set_bit(MAX_RT_PRIO, array->bitmap);
  85
  86#if defined CONFIG_SMP
  87	rt_rq->highest_prio.curr = MAX_RT_PRIO;
  88	rt_rq->highest_prio.next = MAX_RT_PRIO;
  89	rt_rq->rt_nr_migratory = 0;
  90	rt_rq->overloaded = 0;
  91	plist_head_init(&rt_rq->pushable_tasks);
 
 
 
 
 
 
 
  92#endif /* CONFIG_SMP */
  93	/* We start is dequeued state, because no RT tasks are queued */
  94	rt_rq->rt_queued = 0;
  95
  96	rt_rq->rt_time = 0;
  97	rt_rq->rt_throttled = 0;
  98	rt_rq->rt_runtime = 0;
  99	raw_spin_lock_init(&rt_rq->rt_runtime_lock);
 100}
 101
 102#ifdef CONFIG_RT_GROUP_SCHED
 103static void destroy_rt_bandwidth(struct rt_bandwidth *rt_b)
 104{
 105	hrtimer_cancel(&rt_b->rt_period_timer);
 106}
 107
 108#define rt_entity_is_task(rt_se) (!(rt_se)->my_q)
 109
 110static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
 111{
 112#ifdef CONFIG_SCHED_DEBUG
 113	WARN_ON_ONCE(!rt_entity_is_task(rt_se));
 114#endif
 115	return container_of(rt_se, struct task_struct, rt);
 116}
 117
 118static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
 119{
 120	return rt_rq->rq;
 121}
 122
 123static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
 124{
 125	return rt_se->rt_rq;
 126}
 127
 128static inline struct rq *rq_of_rt_se(struct sched_rt_entity *rt_se)
 129{
 130	struct rt_rq *rt_rq = rt_se->rt_rq;
 131
 132	return rt_rq->rq;
 133}
 134
 135void free_rt_sched_group(struct task_group *tg)
 136{
 137	int i;
 138
 139	if (tg->rt_se)
 140		destroy_rt_bandwidth(&tg->rt_bandwidth);
 141
 142	for_each_possible_cpu(i) {
 143		if (tg->rt_rq)
 144			kfree(tg->rt_rq[i]);
 145		if (tg->rt_se)
 146			kfree(tg->rt_se[i]);
 147	}
 148
 149	kfree(tg->rt_rq);
 150	kfree(tg->rt_se);
 151}
 152
 153void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
 154		struct sched_rt_entity *rt_se, int cpu,
 155		struct sched_rt_entity *parent)
 156{
 157	struct rq *rq = cpu_rq(cpu);
 158
 159	rt_rq->highest_prio.curr = MAX_RT_PRIO;
 160	rt_rq->rt_nr_boosted = 0;
 161	rt_rq->rq = rq;
 162	rt_rq->tg = tg;
 163
 164	tg->rt_rq[cpu] = rt_rq;
 165	tg->rt_se[cpu] = rt_se;
 166
 167	if (!rt_se)
 168		return;
 169
 170	if (!parent)
 171		rt_se->rt_rq = &rq->rt;
 172	else
 173		rt_se->rt_rq = parent->my_q;
 174
 175	rt_se->my_q = rt_rq;
 176	rt_se->parent = parent;
 177	INIT_LIST_HEAD(&rt_se->run_list);
 178}
 179
 180int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
 181{
 182	struct rt_rq *rt_rq;
 183	struct sched_rt_entity *rt_se;
 184	int i;
 185
 186	tg->rt_rq = kzalloc(sizeof(rt_rq) * nr_cpu_ids, GFP_KERNEL);
 187	if (!tg->rt_rq)
 188		goto err;
 189	tg->rt_se = kzalloc(sizeof(rt_se) * nr_cpu_ids, GFP_KERNEL);
 190	if (!tg->rt_se)
 191		goto err;
 192
 193	init_rt_bandwidth(&tg->rt_bandwidth,
 194			ktime_to_ns(def_rt_bandwidth.rt_period), 0);
 195
 196	for_each_possible_cpu(i) {
 197		rt_rq = kzalloc_node(sizeof(struct rt_rq),
 198				     GFP_KERNEL, cpu_to_node(i));
 199		if (!rt_rq)
 200			goto err;
 201
 202		rt_se = kzalloc_node(sizeof(struct sched_rt_entity),
 203				     GFP_KERNEL, cpu_to_node(i));
 204		if (!rt_se)
 205			goto err_free_rq;
 206
 207		init_rt_rq(rt_rq);
 208		rt_rq->rt_runtime = tg->rt_bandwidth.rt_runtime;
 209		init_tg_rt_entry(tg, rt_rq, rt_se, i, parent->rt_se[i]);
 210	}
 211
 212	return 1;
 213
 214err_free_rq:
 215	kfree(rt_rq);
 216err:
 217	return 0;
 218}
 219
 220#else /* CONFIG_RT_GROUP_SCHED */
 221
 222#define rt_entity_is_task(rt_se) (1)
 223
 224static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
 225{
 226	return container_of(rt_se, struct task_struct, rt);
 227}
 228
 229static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
 230{
 231	return container_of(rt_rq, struct rq, rt);
 232}
 233
 234static inline struct rq *rq_of_rt_se(struct sched_rt_entity *rt_se)
 235{
 236	struct task_struct *p = rt_task_of(rt_se);
 237
 238	return task_rq(p);
 239}
 240
 241static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
 242{
 243	struct rq *rq = rq_of_rt_se(rt_se);
 244
 245	return &rq->rt;
 246}
 247
 248void free_rt_sched_group(struct task_group *tg) { }
 249
 250int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
 251{
 252	return 1;
 253}
 254#endif /* CONFIG_RT_GROUP_SCHED */
 255
 256#ifdef CONFIG_SMP
 257
 258static void pull_rt_task(struct rq *this_rq);
 259
 260static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
 261{
 262	/* Try to pull RT tasks here if we lower this rq's prio */
 263	return rq->rt.highest_prio.curr > prev->prio;
 264}
 265
 266static inline int rt_overloaded(struct rq *rq)
 267{
 268	return atomic_read(&rq->rd->rto_count);
 269}
 270
 271static inline void rt_set_overload(struct rq *rq)
 272{
 273	if (!rq->online)
 274		return;
 275
 276	cpumask_set_cpu(rq->cpu, rq->rd->rto_mask);
 277	/*
 278	 * Make sure the mask is visible before we set
 279	 * the overload count. That is checked to determine
 280	 * if we should look at the mask. It would be a shame
 281	 * if we looked at the mask, but the mask was not
 282	 * updated yet.
 283	 *
 284	 * Matched by the barrier in pull_rt_task().
 285	 */
 286	smp_wmb();
 287	atomic_inc(&rq->rd->rto_count);
 288}
 289
 290static inline void rt_clear_overload(struct rq *rq)
 291{
 292	if (!rq->online)
 293		return;
 294
 295	/* the order here really doesn't matter */
 296	atomic_dec(&rq->rd->rto_count);
 297	cpumask_clear_cpu(rq->cpu, rq->rd->rto_mask);
 298}
 299
 300static void update_rt_migration(struct rt_rq *rt_rq)
 301{
 302	if (rt_rq->rt_nr_migratory && rt_rq->rt_nr_total > 1) {
 303		if (!rt_rq->overloaded) {
 304			rt_set_overload(rq_of_rt_rq(rt_rq));
 305			rt_rq->overloaded = 1;
 306		}
 307	} else if (rt_rq->overloaded) {
 308		rt_clear_overload(rq_of_rt_rq(rt_rq));
 309		rt_rq->overloaded = 0;
 310	}
 311}
 312
 313static void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 314{
 315	struct task_struct *p;
 316
 317	if (!rt_entity_is_task(rt_se))
 318		return;
 319
 320	p = rt_task_of(rt_se);
 321	rt_rq = &rq_of_rt_rq(rt_rq)->rt;
 322
 323	rt_rq->rt_nr_total++;
 324	if (p->nr_cpus_allowed > 1)
 325		rt_rq->rt_nr_migratory++;
 326
 327	update_rt_migration(rt_rq);
 328}
 329
 330static void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 331{
 332	struct task_struct *p;
 333
 334	if (!rt_entity_is_task(rt_se))
 335		return;
 336
 337	p = rt_task_of(rt_se);
 338	rt_rq = &rq_of_rt_rq(rt_rq)->rt;
 339
 340	rt_rq->rt_nr_total--;
 341	if (p->nr_cpus_allowed > 1)
 342		rt_rq->rt_nr_migratory--;
 343
 344	update_rt_migration(rt_rq);
 345}
 346
 347static inline int has_pushable_tasks(struct rq *rq)
 348{
 349	return !plist_head_empty(&rq->rt.pushable_tasks);
 350}
 351
 352static DEFINE_PER_CPU(struct callback_head, rt_push_head);
 353static DEFINE_PER_CPU(struct callback_head, rt_pull_head);
 354
 355static void push_rt_tasks(struct rq *);
 356static void pull_rt_task(struct rq *);
 357
 358static inline void rt_queue_push_tasks(struct rq *rq)
 359{
 360	if (!has_pushable_tasks(rq))
 361		return;
 362
 363	queue_balance_callback(rq, &per_cpu(rt_push_head, rq->cpu), push_rt_tasks);
 364}
 365
 366static inline void rt_queue_pull_task(struct rq *rq)
 367{
 368	queue_balance_callback(rq, &per_cpu(rt_pull_head, rq->cpu), pull_rt_task);
 369}
 370
 371static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
 372{
 373	plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
 374	plist_node_init(&p->pushable_tasks, p->prio);
 375	plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks);
 376
 377	/* Update the highest prio pushable task */
 378	if (p->prio < rq->rt.highest_prio.next)
 379		rq->rt.highest_prio.next = p->prio;
 380}
 381
 382static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
 383{
 384	plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
 385
 386	/* Update the new highest prio pushable task */
 387	if (has_pushable_tasks(rq)) {
 388		p = plist_first_entry(&rq->rt.pushable_tasks,
 389				      struct task_struct, pushable_tasks);
 390		rq->rt.highest_prio.next = p->prio;
 391	} else
 392		rq->rt.highest_prio.next = MAX_RT_PRIO;
 393}
 394
 395#else
 396
 397static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
 398{
 399}
 400
 401static inline void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
 402{
 403}
 404
 405static inline
 406void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 407{
 408}
 409
 410static inline
 411void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 412{
 413}
 414
 415static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
 416{
 417	return false;
 418}
 419
 420static inline void pull_rt_task(struct rq *this_rq)
 421{
 422}
 423
 424static inline void rt_queue_push_tasks(struct rq *rq)
 425{
 426}
 427#endif /* CONFIG_SMP */
 428
 429static void enqueue_top_rt_rq(struct rt_rq *rt_rq);
 430static void dequeue_top_rt_rq(struct rt_rq *rt_rq);
 431
 432static inline int on_rt_rq(struct sched_rt_entity *rt_se)
 433{
 434	return rt_se->on_rq;
 435}
 436
 437#ifdef CONFIG_RT_GROUP_SCHED
 438
 439static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
 440{
 441	if (!rt_rq->tg)
 442		return RUNTIME_INF;
 443
 444	return rt_rq->rt_runtime;
 445}
 446
 447static inline u64 sched_rt_period(struct rt_rq *rt_rq)
 448{
 449	return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
 450}
 451
 452typedef struct task_group *rt_rq_iter_t;
 453
 454static inline struct task_group *next_task_group(struct task_group *tg)
 455{
 456	do {
 457		tg = list_entry_rcu(tg->list.next,
 458			typeof(struct task_group), list);
 459	} while (&tg->list != &task_groups && task_group_is_autogroup(tg));
 460
 461	if (&tg->list == &task_groups)
 462		tg = NULL;
 463
 464	return tg;
 465}
 466
 467#define for_each_rt_rq(rt_rq, iter, rq)					\
 468	for (iter = container_of(&task_groups, typeof(*iter), list);	\
 469		(iter = next_task_group(iter)) &&			\
 470		(rt_rq = iter->rt_rq[cpu_of(rq)]);)
 471
 472#define for_each_sched_rt_entity(rt_se) \
 473	for (; rt_se; rt_se = rt_se->parent)
 474
 475static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
 476{
 477	return rt_se->my_q;
 478}
 479
 480static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags);
 481static void dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags);
 482
 483static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
 484{
 485	struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
 486	struct rq *rq = rq_of_rt_rq(rt_rq);
 487	struct sched_rt_entity *rt_se;
 488
 489	int cpu = cpu_of(rq);
 490
 491	rt_se = rt_rq->tg->rt_se[cpu];
 492
 493	if (rt_rq->rt_nr_running) {
 494		if (!rt_se)
 495			enqueue_top_rt_rq(rt_rq);
 496		else if (!on_rt_rq(rt_se))
 497			enqueue_rt_entity(rt_se, 0);
 498
 499		if (rt_rq->highest_prio.curr < curr->prio)
 500			resched_curr(rq);
 501	}
 502}
 503
 504static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
 505{
 506	struct sched_rt_entity *rt_se;
 507	int cpu = cpu_of(rq_of_rt_rq(rt_rq));
 508
 509	rt_se = rt_rq->tg->rt_se[cpu];
 510
 511	if (!rt_se)
 512		dequeue_top_rt_rq(rt_rq);
 513	else if (on_rt_rq(rt_se))
 514		dequeue_rt_entity(rt_se, 0);
 515}
 516
 517static inline int rt_rq_throttled(struct rt_rq *rt_rq)
 518{
 519	return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
 520}
 521
 522static int rt_se_boosted(struct sched_rt_entity *rt_se)
 523{
 524	struct rt_rq *rt_rq = group_rt_rq(rt_se);
 525	struct task_struct *p;
 526
 527	if (rt_rq)
 528		return !!rt_rq->rt_nr_boosted;
 529
 530	p = rt_task_of(rt_se);
 531	return p->prio != p->normal_prio;
 532}
 533
 534#ifdef CONFIG_SMP
 535static inline const struct cpumask *sched_rt_period_mask(void)
 536{
 537	return this_rq()->rd->span;
 538}
 539#else
 540static inline const struct cpumask *sched_rt_period_mask(void)
 541{
 542	return cpu_online_mask;
 543}
 544#endif
 545
 546static inline
 547struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
 548{
 549	return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
 550}
 551
 552static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
 553{
 554	return &rt_rq->tg->rt_bandwidth;
 555}
 556
 557#else /* !CONFIG_RT_GROUP_SCHED */
 558
 559static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
 560{
 561	return rt_rq->rt_runtime;
 562}
 563
 564static inline u64 sched_rt_period(struct rt_rq *rt_rq)
 565{
 566	return ktime_to_ns(def_rt_bandwidth.rt_period);
 567}
 568
 569typedef struct rt_rq *rt_rq_iter_t;
 570
 571#define for_each_rt_rq(rt_rq, iter, rq) \
 572	for ((void) iter, rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
 573
 574#define for_each_sched_rt_entity(rt_se) \
 575	for (; rt_se; rt_se = NULL)
 576
 577static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
 578{
 579	return NULL;
 580}
 581
 582static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
 583{
 584	struct rq *rq = rq_of_rt_rq(rt_rq);
 585
 586	if (!rt_rq->rt_nr_running)
 587		return;
 588
 589	enqueue_top_rt_rq(rt_rq);
 590	resched_curr(rq);
 591}
 592
 593static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
 594{
 595	dequeue_top_rt_rq(rt_rq);
 596}
 597
 598static inline int rt_rq_throttled(struct rt_rq *rt_rq)
 599{
 600	return rt_rq->rt_throttled;
 601}
 602
 603static inline const struct cpumask *sched_rt_period_mask(void)
 604{
 605	return cpu_online_mask;
 606}
 607
 608static inline
 609struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
 610{
 611	return &cpu_rq(cpu)->rt;
 612}
 613
 614static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
 615{
 616	return &def_rt_bandwidth;
 617}
 618
 619#endif /* CONFIG_RT_GROUP_SCHED */
 620
 621bool sched_rt_bandwidth_account(struct rt_rq *rt_rq)
 622{
 623	struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 624
 625	return (hrtimer_active(&rt_b->rt_period_timer) ||
 626		rt_rq->rt_time < rt_b->rt_runtime);
 627}
 628
 629#ifdef CONFIG_SMP
 630/*
 631 * We ran out of runtime, see if we can borrow some from our neighbours.
 632 */
 633static void do_balance_runtime(struct rt_rq *rt_rq)
 634{
 635	struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 636	struct root_domain *rd = rq_of_rt_rq(rt_rq)->rd;
 637	int i, weight;
 638	u64 rt_period;
 639
 640	weight = cpumask_weight(rd->span);
 641
 642	raw_spin_lock(&rt_b->rt_runtime_lock);
 643	rt_period = ktime_to_ns(rt_b->rt_period);
 644	for_each_cpu(i, rd->span) {
 645		struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
 646		s64 diff;
 647
 648		if (iter == rt_rq)
 649			continue;
 650
 651		raw_spin_lock(&iter->rt_runtime_lock);
 652		/*
 653		 * Either all rqs have inf runtime and there's nothing to steal
 654		 * or __disable_runtime() below sets a specific rq to inf to
 655		 * indicate its been disabled and disalow stealing.
 656		 */
 657		if (iter->rt_runtime == RUNTIME_INF)
 658			goto next;
 659
 660		/*
 661		 * From runqueues with spare time, take 1/n part of their
 662		 * spare time, but no more than our period.
 663		 */
 664		diff = iter->rt_runtime - iter->rt_time;
 665		if (diff > 0) {
 666			diff = div_u64((u64)diff, weight);
 667			if (rt_rq->rt_runtime + diff > rt_period)
 668				diff = rt_period - rt_rq->rt_runtime;
 669			iter->rt_runtime -= diff;
 670			rt_rq->rt_runtime += diff;
 671			if (rt_rq->rt_runtime == rt_period) {
 672				raw_spin_unlock(&iter->rt_runtime_lock);
 673				break;
 674			}
 675		}
 676next:
 677		raw_spin_unlock(&iter->rt_runtime_lock);
 678	}
 679	raw_spin_unlock(&rt_b->rt_runtime_lock);
 680}
 681
 682/*
 683 * Ensure this RQ takes back all the runtime it lend to its neighbours.
 684 */
 685static void __disable_runtime(struct rq *rq)
 686{
 687	struct root_domain *rd = rq->rd;
 688	rt_rq_iter_t iter;
 689	struct rt_rq *rt_rq;
 690
 691	if (unlikely(!scheduler_running))
 692		return;
 693
 694	for_each_rt_rq(rt_rq, iter, rq) {
 695		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 696		s64 want;
 697		int i;
 698
 699		raw_spin_lock(&rt_b->rt_runtime_lock);
 700		raw_spin_lock(&rt_rq->rt_runtime_lock);
 701		/*
 702		 * Either we're all inf and nobody needs to borrow, or we're
 703		 * already disabled and thus have nothing to do, or we have
 704		 * exactly the right amount of runtime to take out.
 705		 */
 706		if (rt_rq->rt_runtime == RUNTIME_INF ||
 707				rt_rq->rt_runtime == rt_b->rt_runtime)
 708			goto balanced;
 709		raw_spin_unlock(&rt_rq->rt_runtime_lock);
 710
 711		/*
 712		 * Calculate the difference between what we started out with
 713		 * and what we current have, that's the amount of runtime
 714		 * we lend and now have to reclaim.
 715		 */
 716		want = rt_b->rt_runtime - rt_rq->rt_runtime;
 717
 718		/*
 719		 * Greedy reclaim, take back as much as we can.
 720		 */
 721		for_each_cpu(i, rd->span) {
 722			struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
 723			s64 diff;
 724
 725			/*
 726			 * Can't reclaim from ourselves or disabled runqueues.
 727			 */
 728			if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
 729				continue;
 730
 731			raw_spin_lock(&iter->rt_runtime_lock);
 732			if (want > 0) {
 733				diff = min_t(s64, iter->rt_runtime, want);
 734				iter->rt_runtime -= diff;
 735				want -= diff;
 736			} else {
 737				iter->rt_runtime -= want;
 738				want -= want;
 739			}
 740			raw_spin_unlock(&iter->rt_runtime_lock);
 741
 742			if (!want)
 743				break;
 744		}
 745
 746		raw_spin_lock(&rt_rq->rt_runtime_lock);
 747		/*
 748		 * We cannot be left wanting - that would mean some runtime
 749		 * leaked out of the system.
 750		 */
 751		BUG_ON(want);
 752balanced:
 753		/*
 754		 * Disable all the borrow logic by pretending we have inf
 755		 * runtime - in which case borrowing doesn't make sense.
 756		 */
 757		rt_rq->rt_runtime = RUNTIME_INF;
 758		rt_rq->rt_throttled = 0;
 759		raw_spin_unlock(&rt_rq->rt_runtime_lock);
 760		raw_spin_unlock(&rt_b->rt_runtime_lock);
 761
 762		/* Make rt_rq available for pick_next_task() */
 763		sched_rt_rq_enqueue(rt_rq);
 764	}
 765}
 766
 767static void __enable_runtime(struct rq *rq)
 768{
 769	rt_rq_iter_t iter;
 770	struct rt_rq *rt_rq;
 771
 772	if (unlikely(!scheduler_running))
 773		return;
 774
 775	/*
 776	 * Reset each runqueue's bandwidth settings
 777	 */
 778	for_each_rt_rq(rt_rq, iter, rq) {
 779		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 780
 781		raw_spin_lock(&rt_b->rt_runtime_lock);
 782		raw_spin_lock(&rt_rq->rt_runtime_lock);
 783		rt_rq->rt_runtime = rt_b->rt_runtime;
 784		rt_rq->rt_time = 0;
 785		rt_rq->rt_throttled = 0;
 786		raw_spin_unlock(&rt_rq->rt_runtime_lock);
 787		raw_spin_unlock(&rt_b->rt_runtime_lock);
 788	}
 789}
 790
 791static void balance_runtime(struct rt_rq *rt_rq)
 792{
 793	if (!sched_feat(RT_RUNTIME_SHARE))
 794		return;
 795
 796	if (rt_rq->rt_time > rt_rq->rt_runtime) {
 797		raw_spin_unlock(&rt_rq->rt_runtime_lock);
 798		do_balance_runtime(rt_rq);
 799		raw_spin_lock(&rt_rq->rt_runtime_lock);
 800	}
 801}
 802#else /* !CONFIG_SMP */
 803static inline void balance_runtime(struct rt_rq *rt_rq) {}
 804#endif /* CONFIG_SMP */
 805
 806static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
 807{
 808	int i, idle = 1, throttled = 0;
 809	const struct cpumask *span;
 810
 811	span = sched_rt_period_mask();
 812#ifdef CONFIG_RT_GROUP_SCHED
 813	/*
 814	 * FIXME: isolated CPUs should really leave the root task group,
 815	 * whether they are isolcpus or were isolated via cpusets, lest
 816	 * the timer run on a CPU which does not service all runqueues,
 817	 * potentially leaving other CPUs indefinitely throttled.  If
 818	 * isolation is really required, the user will turn the throttle
 819	 * off to kill the perturbations it causes anyway.  Meanwhile,
 820	 * this maintains functionality for boot and/or troubleshooting.
 821	 */
 822	if (rt_b == &root_task_group.rt_bandwidth)
 823		span = cpu_online_mask;
 824#endif
 825	for_each_cpu(i, span) {
 826		int enqueue = 0;
 827		struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
 828		struct rq *rq = rq_of_rt_rq(rt_rq);
 829		int skip;
 830
 831		/*
 832		 * When span == cpu_online_mask, taking each rq->lock
 833		 * can be time-consuming. Try to avoid it when possible.
 834		 */
 835		raw_spin_lock(&rt_rq->rt_runtime_lock);
 836		skip = !rt_rq->rt_time && !rt_rq->rt_nr_running;
 837		raw_spin_unlock(&rt_rq->rt_runtime_lock);
 838		if (skip)
 839			continue;
 840
 841		raw_spin_lock(&rq->lock);
 842		update_rq_clock(rq);
 843
 844		if (rt_rq->rt_time) {
 845			u64 runtime;
 846
 847			raw_spin_lock(&rt_rq->rt_runtime_lock);
 848			if (rt_rq->rt_throttled)
 849				balance_runtime(rt_rq);
 850			runtime = rt_rq->rt_runtime;
 851			rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
 852			if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
 853				rt_rq->rt_throttled = 0;
 854				enqueue = 1;
 855
 856				/*
 857				 * When we're idle and a woken (rt) task is
 858				 * throttled check_preempt_curr() will set
 859				 * skip_update and the time between the wakeup
 860				 * and this unthrottle will get accounted as
 861				 * 'runtime'.
 862				 */
 863				if (rt_rq->rt_nr_running && rq->curr == rq->idle)
 864					rq_clock_cancel_skipupdate(rq);
 865			}
 866			if (rt_rq->rt_time || rt_rq->rt_nr_running)
 867				idle = 0;
 868			raw_spin_unlock(&rt_rq->rt_runtime_lock);
 869		} else if (rt_rq->rt_nr_running) {
 870			idle = 0;
 871			if (!rt_rq_throttled(rt_rq))
 872				enqueue = 1;
 873		}
 874		if (rt_rq->rt_throttled)
 875			throttled = 1;
 876
 877		if (enqueue)
 878			sched_rt_rq_enqueue(rt_rq);
 879		raw_spin_unlock(&rq->lock);
 880	}
 881
 882	if (!throttled && (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF))
 883		return 1;
 884
 885	return idle;
 886}
 887
 888static inline int rt_se_prio(struct sched_rt_entity *rt_se)
 889{
 890#ifdef CONFIG_RT_GROUP_SCHED
 891	struct rt_rq *rt_rq = group_rt_rq(rt_se);
 892
 893	if (rt_rq)
 894		return rt_rq->highest_prio.curr;
 895#endif
 896
 897	return rt_task_of(rt_se)->prio;
 898}
 899
 900static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
 901{
 902	u64 runtime = sched_rt_runtime(rt_rq);
 903
 904	if (rt_rq->rt_throttled)
 905		return rt_rq_throttled(rt_rq);
 906
 907	if (runtime >= sched_rt_period(rt_rq))
 908		return 0;
 909
 910	balance_runtime(rt_rq);
 911	runtime = sched_rt_runtime(rt_rq);
 912	if (runtime == RUNTIME_INF)
 913		return 0;
 914
 915	if (rt_rq->rt_time > runtime) {
 916		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 917
 918		/*
 919		 * Don't actually throttle groups that have no runtime assigned
 920		 * but accrue some time due to boosting.
 921		 */
 922		if (likely(rt_b->rt_runtime)) {
 923			rt_rq->rt_throttled = 1;
 924			printk_deferred_once("sched: RT throttling activated\n");
 925		} else {
 926			/*
 927			 * In case we did anyway, make it go away,
 928			 * replenishment is a joke, since it will replenish us
 929			 * with exactly 0 ns.
 930			 */
 931			rt_rq->rt_time = 0;
 932		}
 933
 934		if (rt_rq_throttled(rt_rq)) {
 935			sched_rt_rq_dequeue(rt_rq);
 936			return 1;
 937		}
 938	}
 939
 940	return 0;
 941}
 942
 943/*
 944 * Update the current task's runtime statistics. Skip current tasks that
 945 * are not in our scheduling class.
 946 */
 947static void update_curr_rt(struct rq *rq)
 948{
 949	struct task_struct *curr = rq->curr;
 950	struct sched_rt_entity *rt_se = &curr->rt;
 951	u64 delta_exec;
 952	u64 now;
 953
 954	if (curr->sched_class != &rt_sched_class)
 955		return;
 956
 957	now = rq_clock_task(rq);
 958	delta_exec = now - curr->se.exec_start;
 959	if (unlikely((s64)delta_exec <= 0))
 960		return;
 961
 
 
 
 962	schedstat_set(curr->se.statistics.exec_max,
 963		      max(curr->se.statistics.exec_max, delta_exec));
 964
 965	curr->se.sum_exec_runtime += delta_exec;
 966	account_group_exec_runtime(curr, delta_exec);
 967
 968	curr->se.exec_start = now;
 969	cgroup_account_cputime(curr, delta_exec);
 970
 971	sched_rt_avg_update(rq, delta_exec);
 972
 973	if (!rt_bandwidth_enabled())
 974		return;
 975
 976	for_each_sched_rt_entity(rt_se) {
 977		struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 978
 979		if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
 980			raw_spin_lock(&rt_rq->rt_runtime_lock);
 981			rt_rq->rt_time += delta_exec;
 982			if (sched_rt_runtime_exceeded(rt_rq))
 983				resched_curr(rq);
 984			raw_spin_unlock(&rt_rq->rt_runtime_lock);
 985		}
 986	}
 987}
 988
 989static void
 990dequeue_top_rt_rq(struct rt_rq *rt_rq)
 991{
 992	struct rq *rq = rq_of_rt_rq(rt_rq);
 993
 994	BUG_ON(&rq->rt != rt_rq);
 995
 996	if (!rt_rq->rt_queued)
 997		return;
 998
 999	BUG_ON(!rq->nr_running);
1000
1001	sub_nr_running(rq, rt_rq->rt_nr_running);
1002	rt_rq->rt_queued = 0;
1003
1004	/* Kick cpufreq (see the comment in kernel/sched/sched.h). */
1005	cpufreq_update_util(rq, 0);
1006}
1007
1008static void
1009enqueue_top_rt_rq(struct rt_rq *rt_rq)
1010{
1011	struct rq *rq = rq_of_rt_rq(rt_rq);
1012
1013	BUG_ON(&rq->rt != rt_rq);
1014
1015	if (rt_rq->rt_queued)
1016		return;
1017	if (rt_rq_throttled(rt_rq) || !rt_rq->rt_nr_running)
1018		return;
1019
1020	add_nr_running(rq, rt_rq->rt_nr_running);
1021	rt_rq->rt_queued = 1;
1022
1023	/* Kick cpufreq (see the comment in kernel/sched/sched.h). */
1024	cpufreq_update_util(rq, 0);
1025}
1026
1027#if defined CONFIG_SMP
1028
1029static void
1030inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
1031{
1032	struct rq *rq = rq_of_rt_rq(rt_rq);
1033
1034#ifdef CONFIG_RT_GROUP_SCHED
1035	/*
1036	 * Change rq's cpupri only if rt_rq is the top queue.
1037	 */
1038	if (&rq->rt != rt_rq)
1039		return;
1040#endif
1041	if (rq->online && prio < prev_prio)
1042		cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
1043}
1044
1045static void
1046dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
1047{
1048	struct rq *rq = rq_of_rt_rq(rt_rq);
1049
1050#ifdef CONFIG_RT_GROUP_SCHED
1051	/*
1052	 * Change rq's cpupri only if rt_rq is the top queue.
1053	 */
1054	if (&rq->rt != rt_rq)
1055		return;
1056#endif
1057	if (rq->online && rt_rq->highest_prio.curr != prev_prio)
1058		cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
1059}
1060
1061#else /* CONFIG_SMP */
1062
1063static inline
1064void inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
1065static inline
1066void dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
1067
1068#endif /* CONFIG_SMP */
1069
1070#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
1071static void
1072inc_rt_prio(struct rt_rq *rt_rq, int prio)
1073{
1074	int prev_prio = rt_rq->highest_prio.curr;
1075
1076	if (prio < prev_prio)
1077		rt_rq->highest_prio.curr = prio;
1078
1079	inc_rt_prio_smp(rt_rq, prio, prev_prio);
1080}
1081
1082static void
1083dec_rt_prio(struct rt_rq *rt_rq, int prio)
1084{
1085	int prev_prio = rt_rq->highest_prio.curr;
1086
1087	if (rt_rq->rt_nr_running) {
1088
1089		WARN_ON(prio < prev_prio);
1090
1091		/*
1092		 * This may have been our highest task, and therefore
1093		 * we may have some recomputation to do
1094		 */
1095		if (prio == prev_prio) {
1096			struct rt_prio_array *array = &rt_rq->active;
1097
1098			rt_rq->highest_prio.curr =
1099				sched_find_first_bit(array->bitmap);
1100		}
1101
1102	} else
1103		rt_rq->highest_prio.curr = MAX_RT_PRIO;
1104
1105	dec_rt_prio_smp(rt_rq, prio, prev_prio);
1106}
1107
1108#else
1109
1110static inline void inc_rt_prio(struct rt_rq *rt_rq, int prio) {}
1111static inline void dec_rt_prio(struct rt_rq *rt_rq, int prio) {}
1112
1113#endif /* CONFIG_SMP || CONFIG_RT_GROUP_SCHED */
1114
1115#ifdef CONFIG_RT_GROUP_SCHED
1116
1117static void
1118inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1119{
1120	if (rt_se_boosted(rt_se))
1121		rt_rq->rt_nr_boosted++;
1122
1123	if (rt_rq->tg)
1124		start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
1125}
1126
1127static void
1128dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1129{
1130	if (rt_se_boosted(rt_se))
1131		rt_rq->rt_nr_boosted--;
1132
1133	WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
1134}
1135
1136#else /* CONFIG_RT_GROUP_SCHED */
1137
1138static void
1139inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1140{
1141	start_rt_bandwidth(&def_rt_bandwidth);
1142}
1143
1144static inline
1145void dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) {}
1146
1147#endif /* CONFIG_RT_GROUP_SCHED */
1148
1149static inline
1150unsigned int rt_se_nr_running(struct sched_rt_entity *rt_se)
1151{
1152	struct rt_rq *group_rq = group_rt_rq(rt_se);
1153
1154	if (group_rq)
1155		return group_rq->rt_nr_running;
1156	else
1157		return 1;
1158}
1159
1160static inline
1161unsigned int rt_se_rr_nr_running(struct sched_rt_entity *rt_se)
1162{
1163	struct rt_rq *group_rq = group_rt_rq(rt_se);
1164	struct task_struct *tsk;
1165
1166	if (group_rq)
1167		return group_rq->rr_nr_running;
1168
1169	tsk = rt_task_of(rt_se);
1170
1171	return (tsk->policy == SCHED_RR) ? 1 : 0;
1172}
1173
1174static inline
1175void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1176{
1177	int prio = rt_se_prio(rt_se);
1178
1179	WARN_ON(!rt_prio(prio));
1180	rt_rq->rt_nr_running += rt_se_nr_running(rt_se);
1181	rt_rq->rr_nr_running += rt_se_rr_nr_running(rt_se);
1182
1183	inc_rt_prio(rt_rq, prio);
1184	inc_rt_migration(rt_se, rt_rq);
1185	inc_rt_group(rt_se, rt_rq);
1186}
1187
1188static inline
1189void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1190{
1191	WARN_ON(!rt_prio(rt_se_prio(rt_se)));
1192	WARN_ON(!rt_rq->rt_nr_running);
1193	rt_rq->rt_nr_running -= rt_se_nr_running(rt_se);
1194	rt_rq->rr_nr_running -= rt_se_rr_nr_running(rt_se);
1195
1196	dec_rt_prio(rt_rq, rt_se_prio(rt_se));
1197	dec_rt_migration(rt_se, rt_rq);
1198	dec_rt_group(rt_se, rt_rq);
1199}
1200
1201/*
1202 * Change rt_se->run_list location unless SAVE && !MOVE
1203 *
1204 * assumes ENQUEUE/DEQUEUE flags match
1205 */
1206static inline bool move_entity(unsigned int flags)
1207{
1208	if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE)
1209		return false;
1210
1211	return true;
1212}
1213
1214static void __delist_rt_entity(struct sched_rt_entity *rt_se, struct rt_prio_array *array)
1215{
1216	list_del_init(&rt_se->run_list);
1217
1218	if (list_empty(array->queue + rt_se_prio(rt_se)))
1219		__clear_bit(rt_se_prio(rt_se), array->bitmap);
1220
1221	rt_se->on_list = 0;
1222}
1223
1224static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1225{
1226	struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
1227	struct rt_prio_array *array = &rt_rq->active;
1228	struct rt_rq *group_rq = group_rt_rq(rt_se);
1229	struct list_head *queue = array->queue + rt_se_prio(rt_se);
1230
1231	/*
1232	 * Don't enqueue the group if its throttled, or when empty.
1233	 * The latter is a consequence of the former when a child group
1234	 * get throttled and the current group doesn't have any other
1235	 * active members.
1236	 */
1237	if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running)) {
1238		if (rt_se->on_list)
1239			__delist_rt_entity(rt_se, array);
1240		return;
1241	}
1242
1243	if (move_entity(flags)) {
1244		WARN_ON_ONCE(rt_se->on_list);
1245		if (flags & ENQUEUE_HEAD)
1246			list_add(&rt_se->run_list, queue);
1247		else
1248			list_add_tail(&rt_se->run_list, queue);
1249
1250		__set_bit(rt_se_prio(rt_se), array->bitmap);
1251		rt_se->on_list = 1;
1252	}
1253	rt_se->on_rq = 1;
1254
1255	inc_rt_tasks(rt_se, rt_rq);
1256}
1257
1258static void __dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1259{
1260	struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
1261	struct rt_prio_array *array = &rt_rq->active;
1262
1263	if (move_entity(flags)) {
1264		WARN_ON_ONCE(!rt_se->on_list);
1265		__delist_rt_entity(rt_se, array);
1266	}
1267	rt_se->on_rq = 0;
1268
1269	dec_rt_tasks(rt_se, rt_rq);
1270}
1271
1272/*
1273 * Because the prio of an upper entry depends on the lower
1274 * entries, we must remove entries top - down.
1275 */
1276static void dequeue_rt_stack(struct sched_rt_entity *rt_se, unsigned int flags)
1277{
1278	struct sched_rt_entity *back = NULL;
1279
1280	for_each_sched_rt_entity(rt_se) {
1281		rt_se->back = back;
1282		back = rt_se;
1283	}
1284
1285	dequeue_top_rt_rq(rt_rq_of_se(back));
1286
1287	for (rt_se = back; rt_se; rt_se = rt_se->back) {
1288		if (on_rt_rq(rt_se))
1289			__dequeue_rt_entity(rt_se, flags);
1290	}
1291}
1292
1293static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1294{
1295	struct rq *rq = rq_of_rt_se(rt_se);
1296
1297	dequeue_rt_stack(rt_se, flags);
1298	for_each_sched_rt_entity(rt_se)
1299		__enqueue_rt_entity(rt_se, flags);
1300	enqueue_top_rt_rq(&rq->rt);
1301}
1302
1303static void dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1304{
1305	struct rq *rq = rq_of_rt_se(rt_se);
1306
1307	dequeue_rt_stack(rt_se, flags);
1308
1309	for_each_sched_rt_entity(rt_se) {
1310		struct rt_rq *rt_rq = group_rt_rq(rt_se);
1311
1312		if (rt_rq && rt_rq->rt_nr_running)
1313			__enqueue_rt_entity(rt_se, flags);
1314	}
1315	enqueue_top_rt_rq(&rq->rt);
1316}
1317
1318/*
1319 * Adding/removing a task to/from a priority array:
1320 */
1321static void
1322enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
1323{
1324	struct sched_rt_entity *rt_se = &p->rt;
1325
1326	if (flags & ENQUEUE_WAKEUP)
1327		rt_se->timeout = 0;
1328
1329	enqueue_rt_entity(rt_se, flags);
1330
1331	if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
1332		enqueue_pushable_task(rq, p);
1333}
1334
1335static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
1336{
1337	struct sched_rt_entity *rt_se = &p->rt;
1338
1339	update_curr_rt(rq);
1340	dequeue_rt_entity(rt_se, flags);
1341
1342	dequeue_pushable_task(rq, p);
1343}
1344
1345/*
1346 * Put task to the head or the end of the run list without the overhead of
1347 * dequeue followed by enqueue.
1348 */
1349static void
1350requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
1351{
1352	if (on_rt_rq(rt_se)) {
1353		struct rt_prio_array *array = &rt_rq->active;
1354		struct list_head *queue = array->queue + rt_se_prio(rt_se);
1355
1356		if (head)
1357			list_move(&rt_se->run_list, queue);
1358		else
1359			list_move_tail(&rt_se->run_list, queue);
1360	}
1361}
1362
1363static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
1364{
1365	struct sched_rt_entity *rt_se = &p->rt;
1366	struct rt_rq *rt_rq;
1367
1368	for_each_sched_rt_entity(rt_se) {
1369		rt_rq = rt_rq_of_se(rt_se);
1370		requeue_rt_entity(rt_rq, rt_se, head);
1371	}
1372}
1373
1374static void yield_task_rt(struct rq *rq)
1375{
1376	requeue_task_rt(rq, rq->curr, 0);
1377}
1378
1379#ifdef CONFIG_SMP
1380static int find_lowest_rq(struct task_struct *task);
1381
1382static int
1383select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
1384{
1385	struct task_struct *curr;
1386	struct rq *rq;
1387
1388	/* For anything but wake ups, just return the task_cpu */
1389	if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
1390		goto out;
1391
1392	rq = cpu_rq(cpu);
1393
1394	rcu_read_lock();
1395	curr = READ_ONCE(rq->curr); /* unlocked access */
1396
1397	/*
1398	 * If the current task on @p's runqueue is an RT task, then
1399	 * try to see if we can wake this RT task up on another
1400	 * runqueue. Otherwise simply start this RT task
1401	 * on its current runqueue.
1402	 *
1403	 * We want to avoid overloading runqueues. If the woken
1404	 * task is a higher priority, then it will stay on this CPU
1405	 * and the lower prio task should be moved to another CPU.
1406	 * Even though this will probably make the lower prio task
1407	 * lose its cache, we do not want to bounce a higher task
1408	 * around just because it gave up its CPU, perhaps for a
1409	 * lock?
1410	 *
1411	 * For equal prio tasks, we just let the scheduler sort it out.
1412	 *
1413	 * Otherwise, just let it ride on the affined RQ and the
1414	 * post-schedule router will push the preempted task away
1415	 *
1416	 * This test is optimistic, if we get it wrong the load-balancer
1417	 * will have to sort it out.
1418	 */
1419	if (curr && unlikely(rt_task(curr)) &&
1420	    (curr->nr_cpus_allowed < 2 ||
1421	     curr->prio <= p->prio)) {
1422		int target = find_lowest_rq(p);
1423
1424		/*
1425		 * Don't bother moving it if the destination CPU is
1426		 * not running a lower priority task.
1427		 */
1428		if (target != -1 &&
1429		    p->prio < cpu_rq(target)->rt.highest_prio.curr)
1430			cpu = target;
1431	}
1432	rcu_read_unlock();
1433
1434out:
1435	return cpu;
1436}
1437
1438static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
1439{
1440	/*
1441	 * Current can't be migrated, useless to reschedule,
1442	 * let's hope p can move out.
1443	 */
1444	if (rq->curr->nr_cpus_allowed == 1 ||
1445	    !cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
1446		return;
1447
1448	/*
1449	 * p is migratable, so let's not schedule it and
1450	 * see if it is pushed or pulled somewhere else.
1451	 */
1452	if (p->nr_cpus_allowed != 1
1453	    && cpupri_find(&rq->rd->cpupri, p, NULL))
1454		return;
1455
1456	/*
1457	 * There appear to be other CPUs that can accept
1458	 * the current task but none can run 'p', so lets reschedule
1459	 * to try and push the current task away:
1460	 */
1461	requeue_task_rt(rq, p, 1);
1462	resched_curr(rq);
1463}
1464
1465#endif /* CONFIG_SMP */
1466
1467/*
1468 * Preempt the current task with a newly woken task if needed:
1469 */
1470static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flags)
1471{
1472	if (p->prio < rq->curr->prio) {
1473		resched_curr(rq);
1474		return;
1475	}
1476
1477#ifdef CONFIG_SMP
1478	/*
1479	 * If:
1480	 *
1481	 * - the newly woken task is of equal priority to the current task
1482	 * - the newly woken task is non-migratable while current is migratable
1483	 * - current will be preempted on the next reschedule
1484	 *
1485	 * we should check to see if current can readily move to a different
1486	 * cpu.  If so, we will reschedule to allow the push logic to try
1487	 * to move current somewhere else, making room for our non-migratable
1488	 * task.
1489	 */
1490	if (p->prio == rq->curr->prio && !test_tsk_need_resched(rq->curr))
1491		check_preempt_equal_prio(rq, p);
1492#endif
1493}
1494
1495static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
1496						   struct rt_rq *rt_rq)
1497{
1498	struct rt_prio_array *array = &rt_rq->active;
1499	struct sched_rt_entity *next = NULL;
1500	struct list_head *queue;
1501	int idx;
1502
1503	idx = sched_find_first_bit(array->bitmap);
1504	BUG_ON(idx >= MAX_RT_PRIO);
1505
1506	queue = array->queue + idx;
1507	next = list_entry(queue->next, struct sched_rt_entity, run_list);
1508
1509	return next;
1510}
1511
1512static struct task_struct *_pick_next_task_rt(struct rq *rq)
1513{
1514	struct sched_rt_entity *rt_se;
1515	struct task_struct *p;
1516	struct rt_rq *rt_rq  = &rq->rt;
1517
1518	do {
1519		rt_se = pick_next_rt_entity(rq, rt_rq);
1520		BUG_ON(!rt_se);
1521		rt_rq = group_rt_rq(rt_se);
1522	} while (rt_rq);
1523
1524	p = rt_task_of(rt_se);
1525	p->se.exec_start = rq_clock_task(rq);
1526
1527	return p;
1528}
1529
1530static struct task_struct *
1531pick_next_task_rt(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
1532{
1533	struct task_struct *p;
1534	struct rt_rq *rt_rq = &rq->rt;
1535
1536	if (need_pull_rt_task(rq, prev)) {
1537		/*
1538		 * This is OK, because current is on_cpu, which avoids it being
1539		 * picked for load-balance and preemption/IRQs are still
1540		 * disabled avoiding further scheduler activity on it and we're
1541		 * being very careful to re-start the picking loop.
1542		 */
1543		rq_unpin_lock(rq, rf);
1544		pull_rt_task(rq);
1545		rq_repin_lock(rq, rf);
1546		/*
1547		 * pull_rt_task() can drop (and re-acquire) rq->lock; this
1548		 * means a dl or stop task can slip in, in which case we need
1549		 * to re-start task selection.
1550		 */
1551		if (unlikely((rq->stop && task_on_rq_queued(rq->stop)) ||
1552			     rq->dl.dl_nr_running))
1553			return RETRY_TASK;
1554	}
1555
1556	/*
1557	 * We may dequeue prev's rt_rq in put_prev_task().
1558	 * So, we update time before rt_nr_running check.
1559	 */
1560	if (prev->sched_class == &rt_sched_class)
1561		update_curr_rt(rq);
1562
1563	if (!rt_rq->rt_queued)
1564		return NULL;
1565
1566	put_prev_task(rq, prev);
1567
1568	p = _pick_next_task_rt(rq);
1569
1570	/* The running task is never eligible for pushing */
1571	dequeue_pushable_task(rq, p);
1572
1573	rt_queue_push_tasks(rq);
1574
1575	return p;
1576}
1577
1578static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
1579{
1580	update_curr_rt(rq);
1581
1582	/*
1583	 * The previous task needs to be made eligible for pushing
1584	 * if it is still active
1585	 */
1586	if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1)
1587		enqueue_pushable_task(rq, p);
1588}
1589
1590#ifdef CONFIG_SMP
1591
1592/* Only try algorithms three times */
1593#define RT_MAX_TRIES 3
1594
1595static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
1596{
1597	if (!task_running(rq, p) &&
1598	    cpumask_test_cpu(cpu, &p->cpus_allowed))
1599		return 1;
1600
1601	return 0;
1602}
1603
1604/*
1605 * Return the highest pushable rq's task, which is suitable to be executed
1606 * on the CPU, NULL otherwise
1607 */
1608static struct task_struct *pick_highest_pushable_task(struct rq *rq, int cpu)
1609{
1610	struct plist_head *head = &rq->rt.pushable_tasks;
1611	struct task_struct *p;
1612
1613	if (!has_pushable_tasks(rq))
1614		return NULL;
1615
1616	plist_for_each_entry(p, head, pushable_tasks) {
1617		if (pick_rt_task(rq, p, cpu))
1618			return p;
1619	}
1620
1621	return NULL;
1622}
1623
1624static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
1625
1626static int find_lowest_rq(struct task_struct *task)
1627{
1628	struct sched_domain *sd;
1629	struct cpumask *lowest_mask = this_cpu_cpumask_var_ptr(local_cpu_mask);
1630	int this_cpu = smp_processor_id();
1631	int cpu      = task_cpu(task);
1632
1633	/* Make sure the mask is initialized first */
1634	if (unlikely(!lowest_mask))
1635		return -1;
1636
1637	if (task->nr_cpus_allowed == 1)
1638		return -1; /* No other targets possible */
1639
1640	if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
1641		return -1; /* No targets found */
1642
1643	/*
1644	 * At this point we have built a mask of CPUs representing the
1645	 * lowest priority tasks in the system.  Now we want to elect
1646	 * the best one based on our affinity and topology.
1647	 *
1648	 * We prioritize the last CPU that the task executed on since
1649	 * it is most likely cache-hot in that location.
1650	 */
1651	if (cpumask_test_cpu(cpu, lowest_mask))
1652		return cpu;
1653
1654	/*
1655	 * Otherwise, we consult the sched_domains span maps to figure
1656	 * out which CPU is logically closest to our hot cache data.
1657	 */
1658	if (!cpumask_test_cpu(this_cpu, lowest_mask))
1659		this_cpu = -1; /* Skip this_cpu opt if not among lowest */
1660
1661	rcu_read_lock();
1662	for_each_domain(cpu, sd) {
1663		if (sd->flags & SD_WAKE_AFFINE) {
1664			int best_cpu;
1665
1666			/*
1667			 * "this_cpu" is cheaper to preempt than a
1668			 * remote processor.
1669			 */
1670			if (this_cpu != -1 &&
1671			    cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
1672				rcu_read_unlock();
1673				return this_cpu;
1674			}
1675
1676			best_cpu = cpumask_first_and(lowest_mask,
1677						     sched_domain_span(sd));
1678			if (best_cpu < nr_cpu_ids) {
1679				rcu_read_unlock();
1680				return best_cpu;
1681			}
1682		}
1683	}
1684	rcu_read_unlock();
1685
1686	/*
1687	 * And finally, if there were no matches within the domains
1688	 * just give the caller *something* to work with from the compatible
1689	 * locations.
1690	 */
1691	if (this_cpu != -1)
1692		return this_cpu;
1693
1694	cpu = cpumask_any(lowest_mask);
1695	if (cpu < nr_cpu_ids)
1696		return cpu;
1697
1698	return -1;
1699}
1700
1701/* Will lock the rq it finds */
1702static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1703{
1704	struct rq *lowest_rq = NULL;
1705	int tries;
1706	int cpu;
1707
1708	for (tries = 0; tries < RT_MAX_TRIES; tries++) {
1709		cpu = find_lowest_rq(task);
1710
1711		if ((cpu == -1) || (cpu == rq->cpu))
1712			break;
1713
1714		lowest_rq = cpu_rq(cpu);
1715
1716		if (lowest_rq->rt.highest_prio.curr <= task->prio) {
1717			/*
1718			 * Target rq has tasks of equal or higher priority,
1719			 * retrying does not release any lock and is unlikely
1720			 * to yield a different result.
1721			 */
1722			lowest_rq = NULL;
1723			break;
1724		}
1725
1726		/* if the prio of this runqueue changed, try again */
1727		if (double_lock_balance(rq, lowest_rq)) {
1728			/*
1729			 * We had to unlock the run queue. In
1730			 * the mean time, task could have
1731			 * migrated already or had its affinity changed.
1732			 * Also make sure that it wasn't scheduled on its rq.
1733			 */
1734			if (unlikely(task_rq(task) != rq ||
1735				     !cpumask_test_cpu(lowest_rq->cpu, &task->cpus_allowed) ||
 
1736				     task_running(rq, task) ||
1737				     !rt_task(task) ||
1738				     !task_on_rq_queued(task))) {
1739
1740				double_unlock_balance(rq, lowest_rq);
1741				lowest_rq = NULL;
1742				break;
1743			}
1744		}
1745
1746		/* If this rq is still suitable use it. */
1747		if (lowest_rq->rt.highest_prio.curr > task->prio)
1748			break;
1749
1750		/* try again */
1751		double_unlock_balance(rq, lowest_rq);
1752		lowest_rq = NULL;
1753	}
1754
1755	return lowest_rq;
1756}
1757
1758static struct task_struct *pick_next_pushable_task(struct rq *rq)
1759{
1760	struct task_struct *p;
1761
1762	if (!has_pushable_tasks(rq))
1763		return NULL;
1764
1765	p = plist_first_entry(&rq->rt.pushable_tasks,
1766			      struct task_struct, pushable_tasks);
1767
1768	BUG_ON(rq->cpu != task_cpu(p));
1769	BUG_ON(task_current(rq, p));
1770	BUG_ON(p->nr_cpus_allowed <= 1);
1771
1772	BUG_ON(!task_on_rq_queued(p));
1773	BUG_ON(!rt_task(p));
1774
1775	return p;
1776}
1777
1778/*
1779 * If the current CPU has more than one RT task, see if the non
1780 * running task can migrate over to a CPU that is running a task
1781 * of lesser priority.
1782 */
1783static int push_rt_task(struct rq *rq)
1784{
1785	struct task_struct *next_task;
1786	struct rq *lowest_rq;
1787	int ret = 0;
1788
1789	if (!rq->rt.overloaded)
1790		return 0;
1791
1792	next_task = pick_next_pushable_task(rq);
1793	if (!next_task)
1794		return 0;
1795
1796retry:
1797	if (unlikely(next_task == rq->curr)) {
1798		WARN_ON(1);
1799		return 0;
1800	}
1801
1802	/*
1803	 * It's possible that the next_task slipped in of
1804	 * higher priority than current. If that's the case
1805	 * just reschedule current.
1806	 */
1807	if (unlikely(next_task->prio < rq->curr->prio)) {
1808		resched_curr(rq);
1809		return 0;
1810	}
1811
1812	/* We might release rq lock */
1813	get_task_struct(next_task);
1814
1815	/* find_lock_lowest_rq locks the rq if found */
1816	lowest_rq = find_lock_lowest_rq(next_task, rq);
1817	if (!lowest_rq) {
1818		struct task_struct *task;
1819		/*
1820		 * find_lock_lowest_rq releases rq->lock
1821		 * so it is possible that next_task has migrated.
1822		 *
1823		 * We need to make sure that the task is still on the same
1824		 * run-queue and is also still the next task eligible for
1825		 * pushing.
1826		 */
1827		task = pick_next_pushable_task(rq);
1828		if (task == next_task) {
1829			/*
1830			 * The task hasn't migrated, and is still the next
1831			 * eligible task, but we failed to find a run-queue
1832			 * to push it to.  Do not retry in this case, since
1833			 * other CPUs will pull from us when ready.
1834			 */
1835			goto out;
1836		}
1837
1838		if (!task)
1839			/* No more tasks, just exit */
1840			goto out;
1841
1842		/*
1843		 * Something has shifted, try again.
1844		 */
1845		put_task_struct(next_task);
1846		next_task = task;
1847		goto retry;
1848	}
1849
1850	deactivate_task(rq, next_task, 0);
1851	set_task_cpu(next_task, lowest_rq->cpu);
1852	activate_task(lowest_rq, next_task, 0);
1853	ret = 1;
1854
1855	resched_curr(lowest_rq);
1856
1857	double_unlock_balance(rq, lowest_rq);
1858
1859out:
1860	put_task_struct(next_task);
1861
1862	return ret;
1863}
1864
1865static void push_rt_tasks(struct rq *rq)
1866{
1867	/* push_rt_task will return true if it moved an RT */
1868	while (push_rt_task(rq))
1869		;
1870}
1871
1872#ifdef HAVE_RT_PUSH_IPI
1873
1874/*
1875 * When a high priority task schedules out from a CPU and a lower priority
1876 * task is scheduled in, a check is made to see if there's any RT tasks
1877 * on other CPUs that are waiting to run because a higher priority RT task
1878 * is currently running on its CPU. In this case, the CPU with multiple RT
1879 * tasks queued on it (overloaded) needs to be notified that a CPU has opened
1880 * up that may be able to run one of its non-running queued RT tasks.
1881 *
1882 * All CPUs with overloaded RT tasks need to be notified as there is currently
1883 * no way to know which of these CPUs have the highest priority task waiting
1884 * to run. Instead of trying to take a spinlock on each of these CPUs,
1885 * which has shown to cause large latency when done on machines with many
1886 * CPUs, sending an IPI to the CPUs to have them push off the overloaded
1887 * RT tasks waiting to run.
1888 *
1889 * Just sending an IPI to each of the CPUs is also an issue, as on large
1890 * count CPU machines, this can cause an IPI storm on a CPU, especially
1891 * if its the only CPU with multiple RT tasks queued, and a large number
1892 * of CPUs scheduling a lower priority task at the same time.
1893 *
1894 * Each root domain has its own irq work function that can iterate over
1895 * all CPUs with RT overloaded tasks. Since all CPUs with overloaded RT
1896 * tassk must be checked if there's one or many CPUs that are lowering
1897 * their priority, there's a single irq work iterator that will try to
1898 * push off RT tasks that are waiting to run.
1899 *
1900 * When a CPU schedules a lower priority task, it will kick off the
1901 * irq work iterator that will jump to each CPU with overloaded RT tasks.
1902 * As it only takes the first CPU that schedules a lower priority task
1903 * to start the process, the rto_start variable is incremented and if
1904 * the atomic result is one, then that CPU will try to take the rto_lock.
1905 * This prevents high contention on the lock as the process handles all
1906 * CPUs scheduling lower priority tasks.
1907 *
1908 * All CPUs that are scheduling a lower priority task will increment the
1909 * rt_loop_next variable. This will make sure that the irq work iterator
1910 * checks all RT overloaded CPUs whenever a CPU schedules a new lower
1911 * priority task, even if the iterator is in the middle of a scan. Incrementing
1912 * the rt_loop_next will cause the iterator to perform another scan.
1913 *
 
 
1914 */
1915static int rto_next_cpu(struct root_domain *rd)
1916{
1917	int next;
1918	int cpu;
1919
 
 
1920	/*
1921	 * When starting the IPI RT pushing, the rto_cpu is set to -1,
1922	 * rt_next_cpu() will simply return the first CPU found in
1923	 * the rto_mask.
1924	 *
1925	 * If rto_next_cpu() is called with rto_cpu is a valid CPU, it
1926	 * will return the next CPU found in the rto_mask.
1927	 *
1928	 * If there are no more CPUs left in the rto_mask, then a check is made
1929	 * against rto_loop and rto_loop_next. rto_loop is only updated with
1930	 * the rto_lock held, but any CPU may increment the rto_loop_next
1931	 * without any locking.
1932	 */
1933	for (;;) {
1934
1935		/* When rto_cpu is -1 this acts like cpumask_first() */
1936		cpu = cpumask_next(rd->rto_cpu, rd->rto_mask);
1937
1938		rd->rto_cpu = cpu;
1939
1940		if (cpu < nr_cpu_ids)
1941			return cpu;
1942
1943		rd->rto_cpu = -1;
1944
 
1945		/*
1946		 * ACQUIRE ensures we see the @rto_mask changes
1947		 * made prior to the @next value observed.
1948		 *
1949		 * Matches WMB in rt_set_overload().
1950		 */
1951		next = atomic_read_acquire(&rd->rto_loop_next);
1952
1953		if (rd->rto_loop == next)
1954			break;
1955
1956		rd->rto_loop = next;
1957	}
 
1958
1959	return -1;
 
1960}
1961
1962static inline bool rto_start_trylock(atomic_t *v)
1963{
1964	return !atomic_cmpxchg_acquire(v, 0, 1);
1965}
1966
1967static inline void rto_start_unlock(atomic_t *v)
1968{
1969	atomic_set_release(v, 0);
 
 
 
 
 
 
 
 
 
1970}
1971
 
 
 
1972static void tell_cpu_to_push(struct rq *rq)
1973{
1974	int cpu = -1;
1975
1976	/* Keep the loop going if the IPI is currently active */
1977	atomic_inc(&rq->rd->rto_loop_next);
1978
1979	/* Only one CPU can initiate a loop at a time */
1980	if (!rto_start_trylock(&rq->rd->rto_loop_start))
1981		return;
 
 
 
 
 
 
 
 
 
 
 
1982
1983	raw_spin_lock(&rq->rd->rto_lock);
1984
1985	/*
1986	 * The rto_cpu is updated under the lock, if it has a valid CPU
1987	 * then the IPI is still running and will continue due to the
1988	 * update to loop_next, and nothing needs to be done here.
1989	 * Otherwise it is finishing up and an ipi needs to be sent.
1990	 */
1991	if (rq->rd->rto_cpu < 0)
1992		cpu = rto_next_cpu(rq->rd);
1993
1994	raw_spin_unlock(&rq->rd->rto_lock);
1995
1996	rto_start_unlock(&rq->rd->rto_loop_start);
1997
1998	if (cpu >= 0) {
1999		/* Make sure the rd does not get freed while pushing */
2000		sched_get_rd(rq->rd);
2001		irq_work_queue_on(&rq->rd->rto_push_work, cpu);
2002	}
2003}
2004
2005/* Called from hardirq context */
2006void rto_push_irq_work_func(struct irq_work *work)
2007{
2008	struct root_domain *rd =
2009		container_of(work, struct root_domain, rto_push_work);
2010	struct rq *rq;
2011	int cpu;
2012
2013	rq = this_rq();
2014
2015	/*
2016	 * We do not need to grab the lock to check for has_pushable_tasks.
2017	 * When it gets updated, a check is made if a push is possible.
2018	 */
 
 
 
2019	if (has_pushable_tasks(rq)) {
2020		raw_spin_lock(&rq->lock);
2021		push_rt_tasks(rq);
2022		raw_spin_unlock(&rq->lock);
2023	}
2024
2025	raw_spin_lock(&rd->rto_lock);
2026
2027	/* Pass the IPI to the next rt overloaded queue */
2028	cpu = rto_next_cpu(rd);
 
 
 
 
 
 
 
 
 
 
2029
2030	raw_spin_unlock(&rd->rto_lock);
 
 
2031
2032	if (cpu < 0) {
2033		sched_put_rd(rd);
2034		return;
2035	}
 
 
 
 
 
 
 
2036
2037	/* Try the next RT overloaded CPU */
2038	irq_work_queue_on(&rd->rto_push_work, cpu);
 
 
 
 
 
 
 
2039}
2040#endif /* HAVE_RT_PUSH_IPI */
2041
2042static void pull_rt_task(struct rq *this_rq)
2043{
2044	int this_cpu = this_rq->cpu, cpu;
2045	bool resched = false;
2046	struct task_struct *p;
2047	struct rq *src_rq;
2048	int rt_overload_count = rt_overloaded(this_rq);
2049
2050	if (likely(!rt_overload_count))
2051		return;
2052
2053	/*
2054	 * Match the barrier from rt_set_overloaded; this guarantees that if we
2055	 * see overloaded we must also see the rto_mask bit.
2056	 */
2057	smp_rmb();
2058
2059	/* If we are the only overloaded CPU do nothing */
2060	if (rt_overload_count == 1 &&
2061	    cpumask_test_cpu(this_rq->cpu, this_rq->rd->rto_mask))
2062		return;
2063
2064#ifdef HAVE_RT_PUSH_IPI
2065	if (sched_feat(RT_PUSH_IPI)) {
2066		tell_cpu_to_push(this_rq);
2067		return;
2068	}
2069#endif
2070
2071	for_each_cpu(cpu, this_rq->rd->rto_mask) {
2072		if (this_cpu == cpu)
2073			continue;
2074
2075		src_rq = cpu_rq(cpu);
2076
2077		/*
2078		 * Don't bother taking the src_rq->lock if the next highest
2079		 * task is known to be lower-priority than our current task.
2080		 * This may look racy, but if this value is about to go
2081		 * logically higher, the src_rq will push this task away.
2082		 * And if its going logically lower, we do not care
2083		 */
2084		if (src_rq->rt.highest_prio.next >=
2085		    this_rq->rt.highest_prio.curr)
2086			continue;
2087
2088		/*
2089		 * We can potentially drop this_rq's lock in
2090		 * double_lock_balance, and another CPU could
2091		 * alter this_rq
2092		 */
2093		double_lock_balance(this_rq, src_rq);
2094
2095		/*
2096		 * We can pull only a task, which is pushable
2097		 * on its rq, and no others.
2098		 */
2099		p = pick_highest_pushable_task(src_rq, this_cpu);
2100
2101		/*
2102		 * Do we have an RT task that preempts
2103		 * the to-be-scheduled task?
2104		 */
2105		if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
2106			WARN_ON(p == src_rq->curr);
2107			WARN_ON(!task_on_rq_queued(p));
2108
2109			/*
2110			 * There's a chance that p is higher in priority
2111			 * than what's currently running on its CPU.
2112			 * This is just that p is wakeing up and hasn't
2113			 * had a chance to schedule. We only pull
2114			 * p if it is lower in priority than the
2115			 * current task on the run queue
2116			 */
2117			if (p->prio < src_rq->curr->prio)
2118				goto skip;
2119
2120			resched = true;
2121
2122			deactivate_task(src_rq, p, 0);
2123			set_task_cpu(p, this_cpu);
2124			activate_task(this_rq, p, 0);
2125			/*
2126			 * We continue with the search, just in
2127			 * case there's an even higher prio task
2128			 * in another runqueue. (low likelihood
2129			 * but possible)
2130			 */
2131		}
2132skip:
2133		double_unlock_balance(this_rq, src_rq);
2134	}
2135
2136	if (resched)
2137		resched_curr(this_rq);
2138}
2139
2140/*
2141 * If we are not running and we are not going to reschedule soon, we should
2142 * try to push tasks away now
2143 */
2144static void task_woken_rt(struct rq *rq, struct task_struct *p)
2145{
2146	if (!task_running(rq, p) &&
2147	    !test_tsk_need_resched(rq->curr) &&
2148	    p->nr_cpus_allowed > 1 &&
2149	    (dl_task(rq->curr) || rt_task(rq->curr)) &&
2150	    (rq->curr->nr_cpus_allowed < 2 ||
2151	     rq->curr->prio <= p->prio))
2152		push_rt_tasks(rq);
2153}
2154
2155/* Assumes rq->lock is held */
2156static void rq_online_rt(struct rq *rq)
2157{
2158	if (rq->rt.overloaded)
2159		rt_set_overload(rq);
2160
2161	__enable_runtime(rq);
2162
2163	cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
2164}
2165
2166/* Assumes rq->lock is held */
2167static void rq_offline_rt(struct rq *rq)
2168{
2169	if (rq->rt.overloaded)
2170		rt_clear_overload(rq);
2171
2172	__disable_runtime(rq);
2173
2174	cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
2175}
2176
2177/*
2178 * When switch from the rt queue, we bring ourselves to a position
2179 * that we might want to pull RT tasks from other runqueues.
2180 */
2181static void switched_from_rt(struct rq *rq, struct task_struct *p)
2182{
2183	/*
2184	 * If there are other RT tasks then we will reschedule
2185	 * and the scheduling of the other RT tasks will handle
2186	 * the balancing. But if we are the last RT task
2187	 * we may need to handle the pulling of RT tasks
2188	 * now.
2189	 */
2190	if (!task_on_rq_queued(p) || rq->rt.rt_nr_running)
2191		return;
2192
2193	rt_queue_pull_task(rq);
2194}
2195
2196void __init init_sched_rt_class(void)
2197{
2198	unsigned int i;
2199
2200	for_each_possible_cpu(i) {
2201		zalloc_cpumask_var_node(&per_cpu(local_cpu_mask, i),
2202					GFP_KERNEL, cpu_to_node(i));
2203	}
2204}
2205#endif /* CONFIG_SMP */
2206
2207/*
2208 * When switching a task to RT, we may overload the runqueue
2209 * with RT tasks. In this case we try to push them off to
2210 * other runqueues.
2211 */
2212static void switched_to_rt(struct rq *rq, struct task_struct *p)
2213{
2214	/*
2215	 * If we are already running, then there's nothing
2216	 * that needs to be done. But if we are not running
2217	 * we may need to preempt the current running task.
2218	 * If that current running task is also an RT task
2219	 * then see if we can move to another run queue.
2220	 */
2221	if (task_on_rq_queued(p) && rq->curr != p) {
2222#ifdef CONFIG_SMP
2223		if (p->nr_cpus_allowed > 1 && rq->rt.overloaded)
2224			rt_queue_push_tasks(rq);
2225#endif /* CONFIG_SMP */
2226		if (p->prio < rq->curr->prio && cpu_online(cpu_of(rq)))
2227			resched_curr(rq);
2228	}
2229}
2230
2231/*
2232 * Priority of the task has changed. This may cause
2233 * us to initiate a push or pull.
2234 */
2235static void
2236prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
2237{
2238	if (!task_on_rq_queued(p))
2239		return;
2240
2241	if (rq->curr == p) {
2242#ifdef CONFIG_SMP
2243		/*
2244		 * If our priority decreases while running, we
2245		 * may need to pull tasks to this runqueue.
2246		 */
2247		if (oldprio < p->prio)
2248			rt_queue_pull_task(rq);
2249
2250		/*
2251		 * If there's a higher priority task waiting to run
2252		 * then reschedule.
2253		 */
2254		if (p->prio > rq->rt.highest_prio.curr)
2255			resched_curr(rq);
2256#else
2257		/* For UP simply resched on drop of prio */
2258		if (oldprio < p->prio)
2259			resched_curr(rq);
2260#endif /* CONFIG_SMP */
2261	} else {
2262		/*
2263		 * This task is not running, but if it is
2264		 * greater than the current running task
2265		 * then reschedule.
2266		 */
2267		if (p->prio < rq->curr->prio)
2268			resched_curr(rq);
2269	}
2270}
2271
2272#ifdef CONFIG_POSIX_TIMERS
2273static void watchdog(struct rq *rq, struct task_struct *p)
2274{
2275	unsigned long soft, hard;
2276
2277	/* max may change after cur was read, this will be fixed next tick */
2278	soft = task_rlimit(p, RLIMIT_RTTIME);
2279	hard = task_rlimit_max(p, RLIMIT_RTTIME);
2280
2281	if (soft != RLIM_INFINITY) {
2282		unsigned long next;
2283
2284		if (p->rt.watchdog_stamp != jiffies) {
2285			p->rt.timeout++;
2286			p->rt.watchdog_stamp = jiffies;
2287		}
2288
2289		next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
2290		if (p->rt.timeout > next)
2291			p->cputime_expires.sched_exp = p->se.sum_exec_runtime;
2292	}
2293}
2294#else
2295static inline void watchdog(struct rq *rq, struct task_struct *p) { }
2296#endif
2297
2298/*
2299 * scheduler tick hitting a task of our scheduling class.
2300 *
2301 * NOTE: This function can be called remotely by the tick offload that
2302 * goes along full dynticks. Therefore no local assumption can be made
2303 * and everything must be accessed through the @rq and @curr passed in
2304 * parameters.
2305 */
2306static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
2307{
2308	struct sched_rt_entity *rt_se = &p->rt;
2309
2310	update_curr_rt(rq);
2311
2312	watchdog(rq, p);
2313
2314	/*
2315	 * RR tasks need a special form of timeslice management.
2316	 * FIFO tasks have no timeslices.
2317	 */
2318	if (p->policy != SCHED_RR)
2319		return;
2320
2321	if (--p->rt.time_slice)
2322		return;
2323
2324	p->rt.time_slice = sched_rr_timeslice;
2325
2326	/*
2327	 * Requeue to the end of queue if we (and all of our ancestors) are not
2328	 * the only element on the queue
2329	 */
2330	for_each_sched_rt_entity(rt_se) {
2331		if (rt_se->run_list.prev != rt_se->run_list.next) {
2332			requeue_task_rt(rq, p, 0);
2333			resched_curr(rq);
2334			return;
2335		}
2336	}
2337}
2338
2339static void set_curr_task_rt(struct rq *rq)
2340{
2341	struct task_struct *p = rq->curr;
2342
2343	p->se.exec_start = rq_clock_task(rq);
2344
2345	/* The running task is never eligible for pushing */
2346	dequeue_pushable_task(rq, p);
2347}
2348
2349static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
2350{
2351	/*
2352	 * Time slice is 0 for SCHED_FIFO tasks
2353	 */
2354	if (task->policy == SCHED_RR)
2355		return sched_rr_timeslice;
2356	else
2357		return 0;
2358}
2359
2360const struct sched_class rt_sched_class = {
2361	.next			= &fair_sched_class,
2362	.enqueue_task		= enqueue_task_rt,
2363	.dequeue_task		= dequeue_task_rt,
2364	.yield_task		= yield_task_rt,
2365
2366	.check_preempt_curr	= check_preempt_curr_rt,
2367
2368	.pick_next_task		= pick_next_task_rt,
2369	.put_prev_task		= put_prev_task_rt,
2370
2371#ifdef CONFIG_SMP
2372	.select_task_rq		= select_task_rq_rt,
2373
2374	.set_cpus_allowed       = set_cpus_allowed_common,
2375	.rq_online              = rq_online_rt,
2376	.rq_offline             = rq_offline_rt,
2377	.task_woken		= task_woken_rt,
2378	.switched_from		= switched_from_rt,
2379#endif
2380
2381	.set_curr_task          = set_curr_task_rt,
2382	.task_tick		= task_tick_rt,
2383
2384	.get_rr_interval	= get_rr_interval_rt,
2385
2386	.prio_changed		= prio_changed_rt,
2387	.switched_to		= switched_to_rt,
2388
2389	.update_curr		= update_curr_rt,
2390};
2391
2392#ifdef CONFIG_RT_GROUP_SCHED
2393/*
2394 * Ensure that the real time constraints are schedulable.
2395 */
2396static DEFINE_MUTEX(rt_constraints_mutex);
2397
2398/* Must be called with tasklist_lock held */
2399static inline int tg_has_rt_tasks(struct task_group *tg)
2400{
2401	struct task_struct *g, *p;
2402
2403	/*
2404	 * Autogroups do not have RT tasks; see autogroup_create().
2405	 */
2406	if (task_group_is_autogroup(tg))
2407		return 0;
2408
2409	for_each_process_thread(g, p) {
2410		if (rt_task(p) && task_group(p) == tg)
2411			return 1;
2412	}
2413
2414	return 0;
2415}
2416
2417struct rt_schedulable_data {
2418	struct task_group *tg;
2419	u64 rt_period;
2420	u64 rt_runtime;
2421};
2422
2423static int tg_rt_schedulable(struct task_group *tg, void *data)
2424{
2425	struct rt_schedulable_data *d = data;
2426	struct task_group *child;
2427	unsigned long total, sum = 0;
2428	u64 period, runtime;
2429
2430	period = ktime_to_ns(tg->rt_bandwidth.rt_period);
2431	runtime = tg->rt_bandwidth.rt_runtime;
2432
2433	if (tg == d->tg) {
2434		period = d->rt_period;
2435		runtime = d->rt_runtime;
2436	}
2437
2438	/*
2439	 * Cannot have more runtime than the period.
2440	 */
2441	if (runtime > period && runtime != RUNTIME_INF)
2442		return -EINVAL;
2443
2444	/*
2445	 * Ensure we don't starve existing RT tasks.
2446	 */
2447	if (rt_bandwidth_enabled() && !runtime && tg_has_rt_tasks(tg))
2448		return -EBUSY;
2449
2450	total = to_ratio(period, runtime);
2451
2452	/*
2453	 * Nobody can have more than the global setting allows.
2454	 */
2455	if (total > to_ratio(global_rt_period(), global_rt_runtime()))
2456		return -EINVAL;
2457
2458	/*
2459	 * The sum of our children's runtime should not exceed our own.
2460	 */
2461	list_for_each_entry_rcu(child, &tg->children, siblings) {
2462		period = ktime_to_ns(child->rt_bandwidth.rt_period);
2463		runtime = child->rt_bandwidth.rt_runtime;
2464
2465		if (child == d->tg) {
2466			period = d->rt_period;
2467			runtime = d->rt_runtime;
2468		}
2469
2470		sum += to_ratio(period, runtime);
2471	}
2472
2473	if (sum > total)
2474		return -EINVAL;
2475
2476	return 0;
2477}
2478
2479static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
2480{
2481	int ret;
2482
2483	struct rt_schedulable_data data = {
2484		.tg = tg,
2485		.rt_period = period,
2486		.rt_runtime = runtime,
2487	};
2488
2489	rcu_read_lock();
2490	ret = walk_tg_tree(tg_rt_schedulable, tg_nop, &data);
2491	rcu_read_unlock();
2492
2493	return ret;
2494}
2495
2496static int tg_set_rt_bandwidth(struct task_group *tg,
2497		u64 rt_period, u64 rt_runtime)
2498{
2499	int i, err = 0;
2500
2501	/*
2502	 * Disallowing the root group RT runtime is BAD, it would disallow the
2503	 * kernel creating (and or operating) RT threads.
2504	 */
2505	if (tg == &root_task_group && rt_runtime == 0)
2506		return -EINVAL;
2507
2508	/* No period doesn't make any sense. */
2509	if (rt_period == 0)
2510		return -EINVAL;
2511
2512	mutex_lock(&rt_constraints_mutex);
2513	read_lock(&tasklist_lock);
2514	err = __rt_schedulable(tg, rt_period, rt_runtime);
2515	if (err)
2516		goto unlock;
2517
2518	raw_spin_lock_irq(&tg->rt_bandwidth.rt_runtime_lock);
2519	tg->rt_bandwidth.rt_period = ns_to_ktime(rt_period);
2520	tg->rt_bandwidth.rt_runtime = rt_runtime;
2521
2522	for_each_possible_cpu(i) {
2523		struct rt_rq *rt_rq = tg->rt_rq[i];
2524
2525		raw_spin_lock(&rt_rq->rt_runtime_lock);
2526		rt_rq->rt_runtime = rt_runtime;
2527		raw_spin_unlock(&rt_rq->rt_runtime_lock);
2528	}
2529	raw_spin_unlock_irq(&tg->rt_bandwidth.rt_runtime_lock);
2530unlock:
2531	read_unlock(&tasklist_lock);
2532	mutex_unlock(&rt_constraints_mutex);
2533
2534	return err;
2535}
2536
2537int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)
2538{
2539	u64 rt_runtime, rt_period;
2540
2541	rt_period = ktime_to_ns(tg->rt_bandwidth.rt_period);
2542	rt_runtime = (u64)rt_runtime_us * NSEC_PER_USEC;
2543	if (rt_runtime_us < 0)
2544		rt_runtime = RUNTIME_INF;
2545
2546	return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
2547}
2548
2549long sched_group_rt_runtime(struct task_group *tg)
2550{
2551	u64 rt_runtime_us;
2552
2553	if (tg->rt_bandwidth.rt_runtime == RUNTIME_INF)
2554		return -1;
2555
2556	rt_runtime_us = tg->rt_bandwidth.rt_runtime;
2557	do_div(rt_runtime_us, NSEC_PER_USEC);
2558	return rt_runtime_us;
2559}
2560
2561int sched_group_set_rt_period(struct task_group *tg, u64 rt_period_us)
2562{
2563	u64 rt_runtime, rt_period;
2564
2565	rt_period = rt_period_us * NSEC_PER_USEC;
2566	rt_runtime = tg->rt_bandwidth.rt_runtime;
2567
2568	return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
2569}
2570
2571long sched_group_rt_period(struct task_group *tg)
2572{
2573	u64 rt_period_us;
2574
2575	rt_period_us = ktime_to_ns(tg->rt_bandwidth.rt_period);
2576	do_div(rt_period_us, NSEC_PER_USEC);
2577	return rt_period_us;
2578}
2579
2580static int sched_rt_global_constraints(void)
2581{
2582	int ret = 0;
2583
2584	mutex_lock(&rt_constraints_mutex);
2585	read_lock(&tasklist_lock);
2586	ret = __rt_schedulable(NULL, 0, 0);
2587	read_unlock(&tasklist_lock);
2588	mutex_unlock(&rt_constraints_mutex);
2589
2590	return ret;
2591}
2592
2593int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
2594{
2595	/* Don't accept realtime tasks when there is no way for them to run */
2596	if (rt_task(tsk) && tg->rt_bandwidth.rt_runtime == 0)
2597		return 0;
2598
2599	return 1;
2600}
2601
2602#else /* !CONFIG_RT_GROUP_SCHED */
2603static int sched_rt_global_constraints(void)
2604{
2605	unsigned long flags;
2606	int i;
2607
2608	raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
2609	for_each_possible_cpu(i) {
2610		struct rt_rq *rt_rq = &cpu_rq(i)->rt;
2611
2612		raw_spin_lock(&rt_rq->rt_runtime_lock);
2613		rt_rq->rt_runtime = global_rt_runtime();
2614		raw_spin_unlock(&rt_rq->rt_runtime_lock);
2615	}
2616	raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
2617
2618	return 0;
2619}
2620#endif /* CONFIG_RT_GROUP_SCHED */
2621
2622static int sched_rt_global_validate(void)
2623{
2624	if (sysctl_sched_rt_period <= 0)
2625		return -EINVAL;
2626
2627	if ((sysctl_sched_rt_runtime != RUNTIME_INF) &&
2628		(sysctl_sched_rt_runtime > sysctl_sched_rt_period))
2629		return -EINVAL;
2630
2631	return 0;
2632}
2633
2634static void sched_rt_do_global(void)
2635{
2636	def_rt_bandwidth.rt_runtime = global_rt_runtime();
2637	def_rt_bandwidth.rt_period = ns_to_ktime(global_rt_period());
2638}
2639
2640int sched_rt_handler(struct ctl_table *table, int write,
2641		void __user *buffer, size_t *lenp,
2642		loff_t *ppos)
2643{
2644	int old_period, old_runtime;
2645	static DEFINE_MUTEX(mutex);
2646	int ret;
2647
2648	mutex_lock(&mutex);
2649	old_period = sysctl_sched_rt_period;
2650	old_runtime = sysctl_sched_rt_runtime;
2651
2652	ret = proc_dointvec(table, write, buffer, lenp, ppos);
2653
2654	if (!ret && write) {
2655		ret = sched_rt_global_validate();
2656		if (ret)
2657			goto undo;
2658
2659		ret = sched_dl_global_validate();
2660		if (ret)
2661			goto undo;
2662
2663		ret = sched_rt_global_constraints();
2664		if (ret)
2665			goto undo;
2666
2667		sched_rt_do_global();
2668		sched_dl_do_global();
2669	}
2670	if (0) {
2671undo:
2672		sysctl_sched_rt_period = old_period;
2673		sysctl_sched_rt_runtime = old_runtime;
2674	}
2675	mutex_unlock(&mutex);
2676
2677	return ret;
2678}
2679
2680int sched_rr_handler(struct ctl_table *table, int write,
2681		void __user *buffer, size_t *lenp,
2682		loff_t *ppos)
2683{
2684	int ret;
2685	static DEFINE_MUTEX(mutex);
2686
2687	mutex_lock(&mutex);
2688	ret = proc_dointvec(table, write, buffer, lenp, ppos);
2689	/*
2690	 * Make sure that internally we keep jiffies.
2691	 * Also, writing zero resets the timeslice to default:
2692	 */
2693	if (!ret && write) {
2694		sched_rr_timeslice =
2695			sysctl_sched_rr_timeslice <= 0 ? RR_TIMESLICE :
2696			msecs_to_jiffies(sysctl_sched_rr_timeslice);
2697	}
2698	mutex_unlock(&mutex);
2699
2700	return ret;
2701}
2702
2703#ifdef CONFIG_SCHED_DEBUG
 
 
2704void print_rt_stats(struct seq_file *m, int cpu)
2705{
2706	rt_rq_iter_t iter;
2707	struct rt_rq *rt_rq;
2708
2709	rcu_read_lock();
2710	for_each_rt_rq(rt_rq, iter, cpu_rq(cpu))
2711		print_rt_rq(m, cpu, rt_rq);
2712	rcu_read_unlock();
2713}
2714#endif /* CONFIG_SCHED_DEBUG */