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
   8#include "pelt.h"
 
   9
  10int sched_rr_timeslice = RR_TIMESLICE;
  11int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;
  12
  13static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);
  14
  15struct rt_bandwidth def_rt_bandwidth;
  16
  17static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer)
  18{
  19	struct rt_bandwidth *rt_b =
  20		container_of(timer, struct rt_bandwidth, rt_period_timer);
  21	int idle = 0;
  22	int overrun;
  23
  24	raw_spin_lock(&rt_b->rt_runtime_lock);
  25	for (;;) {
  26		overrun = hrtimer_forward_now(timer, rt_b->rt_period);
  27		if (!overrun)
  28			break;
  29
  30		raw_spin_unlock(&rt_b->rt_runtime_lock);
  31		idle = do_sched_rt_period_timer(rt_b, overrun);
  32		raw_spin_lock(&rt_b->rt_runtime_lock);
  33	}
  34	if (idle)
  35		rt_b->rt_period_active = 0;
  36	raw_spin_unlock(&rt_b->rt_runtime_lock);
  37
  38	return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
  39}
  40
  41void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime)
  42{
  43	rt_b->rt_period = ns_to_ktime(period);
  44	rt_b->rt_runtime = runtime;
  45
  46	raw_spin_lock_init(&rt_b->rt_runtime_lock);
  47
  48	hrtimer_init(&rt_b->rt_period_timer, CLOCK_MONOTONIC,
  49		     HRTIMER_MODE_REL_HARD);
  50	rt_b->rt_period_timer.function = sched_rt_period_timer;
  51}
  52
  53static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
  54{
  55	if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
  56		return;
  57
  58	raw_spin_lock(&rt_b->rt_runtime_lock);
  59	if (!rt_b->rt_period_active) {
  60		rt_b->rt_period_active = 1;
  61		/*
  62		 * SCHED_DEADLINE updates the bandwidth, as a run away
  63		 * RT task with a DL task could hog a CPU. But DL does
  64		 * not reset the period. If a deadline task was running
  65		 * without an RT task running, it can cause RT tasks to
  66		 * throttle when they start up. Kick the timer right away
  67		 * to update the period.
  68		 */
  69		hrtimer_forward_now(&rt_b->rt_period_timer, ns_to_ktime(0));
  70		hrtimer_start_expires(&rt_b->rt_period_timer,
  71				      HRTIMER_MODE_ABS_PINNED_HARD);
  72	}
  73	raw_spin_unlock(&rt_b->rt_runtime_lock);
  74}
  75
 
 
 
 
  76void init_rt_rq(struct rt_rq *rt_rq)
  77{
  78	struct rt_prio_array *array;
  79	int i;
  80
  81	array = &rt_rq->active;
  82	for (i = 0; i < MAX_RT_PRIO; i++) {
  83		INIT_LIST_HEAD(array->queue + i);
  84		__clear_bit(i, array->bitmap);
  85	}
  86	/* delimiter for bitsearch: */
  87	__set_bit(MAX_RT_PRIO, array->bitmap);
  88
  89#if defined CONFIG_SMP
  90	rt_rq->highest_prio.curr = MAX_RT_PRIO;
  91	rt_rq->highest_prio.next = MAX_RT_PRIO;
  92	rt_rq->rt_nr_migratory = 0;
  93	rt_rq->overloaded = 0;
  94	plist_head_init(&rt_rq->pushable_tasks);
 
 
 
 
 
 
 
  95#endif /* CONFIG_SMP */
  96	/* We start is dequeued state, because no RT tasks are queued */
  97	rt_rq->rt_queued = 0;
  98
  99	rt_rq->rt_time = 0;
 100	rt_rq->rt_throttled = 0;
 101	rt_rq->rt_runtime = 0;
 102	raw_spin_lock_init(&rt_rq->rt_runtime_lock);
 103}
 104
 105#ifdef CONFIG_RT_GROUP_SCHED
 106static void destroy_rt_bandwidth(struct rt_bandwidth *rt_b)
 107{
 108	hrtimer_cancel(&rt_b->rt_period_timer);
 109}
 110
 111#define rt_entity_is_task(rt_se) (!(rt_se)->my_q)
 112
 113static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
 114{
 115#ifdef CONFIG_SCHED_DEBUG
 116	WARN_ON_ONCE(!rt_entity_is_task(rt_se));
 117#endif
 118	return container_of(rt_se, struct task_struct, rt);
 119}
 120
 121static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
 122{
 123	return rt_rq->rq;
 124}
 125
 126static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
 127{
 128	return rt_se->rt_rq;
 129}
 130
 131static inline struct rq *rq_of_rt_se(struct sched_rt_entity *rt_se)
 132{
 133	struct rt_rq *rt_rq = rt_se->rt_rq;
 134
 135	return rt_rq->rq;
 136}
 137
 138void free_rt_sched_group(struct task_group *tg)
 139{
 140	int i;
 141
 142	if (tg->rt_se)
 143		destroy_rt_bandwidth(&tg->rt_bandwidth);
 144
 145	for_each_possible_cpu(i) {
 146		if (tg->rt_rq)
 147			kfree(tg->rt_rq[i]);
 148		if (tg->rt_se)
 149			kfree(tg->rt_se[i]);
 150	}
 151
 152	kfree(tg->rt_rq);
 153	kfree(tg->rt_se);
 154}
 155
 156void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
 157		struct sched_rt_entity *rt_se, int cpu,
 158		struct sched_rt_entity *parent)
 159{
 160	struct rq *rq = cpu_rq(cpu);
 161
 162	rt_rq->highest_prio.curr = MAX_RT_PRIO;
 163	rt_rq->rt_nr_boosted = 0;
 164	rt_rq->rq = rq;
 165	rt_rq->tg = tg;
 166
 167	tg->rt_rq[cpu] = rt_rq;
 168	tg->rt_se[cpu] = rt_se;
 169
 170	if (!rt_se)
 171		return;
 172
 173	if (!parent)
 174		rt_se->rt_rq = &rq->rt;
 175	else
 176		rt_se->rt_rq = parent->my_q;
 177
 178	rt_se->my_q = rt_rq;
 179	rt_se->parent = parent;
 180	INIT_LIST_HEAD(&rt_se->run_list);
 181}
 182
 183int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
 184{
 185	struct rt_rq *rt_rq;
 186	struct sched_rt_entity *rt_se;
 187	int i;
 188
 189	tg->rt_rq = kcalloc(nr_cpu_ids, sizeof(rt_rq), GFP_KERNEL);
 190	if (!tg->rt_rq)
 191		goto err;
 192	tg->rt_se = kcalloc(nr_cpu_ids, sizeof(rt_se), GFP_KERNEL);
 193	if (!tg->rt_se)
 194		goto err;
 195
 196	init_rt_bandwidth(&tg->rt_bandwidth,
 197			ktime_to_ns(def_rt_bandwidth.rt_period), 0);
 198
 199	for_each_possible_cpu(i) {
 200		rt_rq = kzalloc_node(sizeof(struct rt_rq),
 201				     GFP_KERNEL, cpu_to_node(i));
 202		if (!rt_rq)
 203			goto err;
 204
 205		rt_se = kzalloc_node(sizeof(struct sched_rt_entity),
 206				     GFP_KERNEL, cpu_to_node(i));
 207		if (!rt_se)
 208			goto err_free_rq;
 209
 210		init_rt_rq(rt_rq);
 211		rt_rq->rt_runtime = tg->rt_bandwidth.rt_runtime;
 212		init_tg_rt_entry(tg, rt_rq, rt_se, i, parent->rt_se[i]);
 213	}
 214
 215	return 1;
 216
 217err_free_rq:
 218	kfree(rt_rq);
 219err:
 220	return 0;
 221}
 222
 223#else /* CONFIG_RT_GROUP_SCHED */
 224
 225#define rt_entity_is_task(rt_se) (1)
 226
 227static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
 228{
 229	return container_of(rt_se, struct task_struct, rt);
 230}
 231
 232static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
 233{
 234	return container_of(rt_rq, struct rq, rt);
 235}
 236
 237static inline struct rq *rq_of_rt_se(struct sched_rt_entity *rt_se)
 238{
 239	struct task_struct *p = rt_task_of(rt_se);
 240
 241	return task_rq(p);
 242}
 243
 244static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
 245{
 246	struct rq *rq = rq_of_rt_se(rt_se);
 247
 248	return &rq->rt;
 249}
 250
 251void free_rt_sched_group(struct task_group *tg) { }
 252
 253int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
 254{
 255	return 1;
 256}
 257#endif /* CONFIG_RT_GROUP_SCHED */
 258
 259#ifdef CONFIG_SMP
 260
 261static void pull_rt_task(struct rq *this_rq);
 262
 263static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
 264{
 265	/* Try to pull RT tasks here if we lower this rq's prio */
 266	return rq->rt.highest_prio.curr > prev->prio;
 267}
 268
 269static inline int rt_overloaded(struct rq *rq)
 270{
 271	return atomic_read(&rq->rd->rto_count);
 272}
 273
 274static inline void rt_set_overload(struct rq *rq)
 275{
 276	if (!rq->online)
 277		return;
 278
 279	cpumask_set_cpu(rq->cpu, rq->rd->rto_mask);
 280	/*
 281	 * Make sure the mask is visible before we set
 282	 * the overload count. That is checked to determine
 283	 * if we should look at the mask. It would be a shame
 284	 * if we looked at the mask, but the mask was not
 285	 * updated yet.
 286	 *
 287	 * Matched by the barrier in pull_rt_task().
 288	 */
 289	smp_wmb();
 290	atomic_inc(&rq->rd->rto_count);
 291}
 292
 293static inline void rt_clear_overload(struct rq *rq)
 294{
 295	if (!rq->online)
 296		return;
 297
 298	/* the order here really doesn't matter */
 299	atomic_dec(&rq->rd->rto_count);
 300	cpumask_clear_cpu(rq->cpu, rq->rd->rto_mask);
 301}
 302
 303static void update_rt_migration(struct rt_rq *rt_rq)
 304{
 305	if (rt_rq->rt_nr_migratory && rt_rq->rt_nr_total > 1) {
 306		if (!rt_rq->overloaded) {
 307			rt_set_overload(rq_of_rt_rq(rt_rq));
 308			rt_rq->overloaded = 1;
 309		}
 310	} else if (rt_rq->overloaded) {
 311		rt_clear_overload(rq_of_rt_rq(rt_rq));
 312		rt_rq->overloaded = 0;
 313	}
 314}
 315
 316static void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 317{
 318	struct task_struct *p;
 319
 320	if (!rt_entity_is_task(rt_se))
 321		return;
 322
 323	p = rt_task_of(rt_se);
 324	rt_rq = &rq_of_rt_rq(rt_rq)->rt;
 325
 326	rt_rq->rt_nr_total++;
 327	if (p->nr_cpus_allowed > 1)
 328		rt_rq->rt_nr_migratory++;
 329
 330	update_rt_migration(rt_rq);
 331}
 332
 333static void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 334{
 335	struct task_struct *p;
 336
 337	if (!rt_entity_is_task(rt_se))
 338		return;
 339
 340	p = rt_task_of(rt_se);
 341	rt_rq = &rq_of_rt_rq(rt_rq)->rt;
 342
 343	rt_rq->rt_nr_total--;
 344	if (p->nr_cpus_allowed > 1)
 345		rt_rq->rt_nr_migratory--;
 346
 347	update_rt_migration(rt_rq);
 348}
 349
 350static inline int has_pushable_tasks(struct rq *rq)
 351{
 352	return !plist_head_empty(&rq->rt.pushable_tasks);
 353}
 354
 355static DEFINE_PER_CPU(struct callback_head, rt_push_head);
 356static DEFINE_PER_CPU(struct callback_head, rt_pull_head);
 357
 358static void push_rt_tasks(struct rq *);
 359static void pull_rt_task(struct rq *);
 360
 361static inline void rt_queue_push_tasks(struct rq *rq)
 362{
 363	if (!has_pushable_tasks(rq))
 364		return;
 365
 366	queue_balance_callback(rq, &per_cpu(rt_push_head, rq->cpu), push_rt_tasks);
 367}
 368
 369static inline void rt_queue_pull_task(struct rq *rq)
 370{
 371	queue_balance_callback(rq, &per_cpu(rt_pull_head, rq->cpu), pull_rt_task);
 372}
 373
 374static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
 375{
 376	plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
 377	plist_node_init(&p->pushable_tasks, p->prio);
 378	plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks);
 379
 380	/* Update the highest prio pushable task */
 381	if (p->prio < rq->rt.highest_prio.next)
 382		rq->rt.highest_prio.next = p->prio;
 383}
 384
 385static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
 386{
 387	plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
 388
 389	/* Update the new highest prio pushable task */
 390	if (has_pushable_tasks(rq)) {
 391		p = plist_first_entry(&rq->rt.pushable_tasks,
 392				      struct task_struct, pushable_tasks);
 393		rq->rt.highest_prio.next = p->prio;
 394	} else
 395		rq->rt.highest_prio.next = MAX_RT_PRIO;
 396}
 397
 398#else
 399
 400static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
 401{
 402}
 403
 404static inline void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
 405{
 406}
 407
 408static inline
 409void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 410{
 411}
 412
 413static inline
 414void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 415{
 416}
 417
 418static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
 419{
 420	return false;
 421}
 422
 423static inline void pull_rt_task(struct rq *this_rq)
 424{
 425}
 426
 427static inline void rt_queue_push_tasks(struct rq *rq)
 428{
 429}
 430#endif /* CONFIG_SMP */
 431
 432static void enqueue_top_rt_rq(struct rt_rq *rt_rq);
 433static void dequeue_top_rt_rq(struct rt_rq *rt_rq);
 434
 435static inline int on_rt_rq(struct sched_rt_entity *rt_se)
 436{
 437	return rt_se->on_rq;
 438}
 439
 440#ifdef CONFIG_RT_GROUP_SCHED
 441
 442static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
 443{
 444	if (!rt_rq->tg)
 445		return RUNTIME_INF;
 446
 447	return rt_rq->rt_runtime;
 448}
 449
 450static inline u64 sched_rt_period(struct rt_rq *rt_rq)
 451{
 452	return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
 453}
 454
 455typedef struct task_group *rt_rq_iter_t;
 456
 457static inline struct task_group *next_task_group(struct task_group *tg)
 458{
 459	do {
 460		tg = list_entry_rcu(tg->list.next,
 461			typeof(struct task_group), list);
 462	} while (&tg->list != &task_groups && task_group_is_autogroup(tg));
 463
 464	if (&tg->list == &task_groups)
 465		tg = NULL;
 466
 467	return tg;
 468}
 469
 470#define for_each_rt_rq(rt_rq, iter, rq)					\
 471	for (iter = container_of(&task_groups, typeof(*iter), list);	\
 472		(iter = next_task_group(iter)) &&			\
 473		(rt_rq = iter->rt_rq[cpu_of(rq)]);)
 474
 475#define for_each_sched_rt_entity(rt_se) \
 476	for (; rt_se; rt_se = rt_se->parent)
 477
 478static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
 479{
 480	return rt_se->my_q;
 481}
 482
 483static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags);
 484static void dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags);
 485
 486static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
 487{
 488	struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
 489	struct rq *rq = rq_of_rt_rq(rt_rq);
 490	struct sched_rt_entity *rt_se;
 491
 492	int cpu = cpu_of(rq);
 493
 494	rt_se = rt_rq->tg->rt_se[cpu];
 495
 496	if (rt_rq->rt_nr_running) {
 497		if (!rt_se)
 498			enqueue_top_rt_rq(rt_rq);
 499		else if (!on_rt_rq(rt_se))
 500			enqueue_rt_entity(rt_se, 0);
 501
 502		if (rt_rq->highest_prio.curr < curr->prio)
 503			resched_curr(rq);
 504	}
 505}
 506
 507static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
 508{
 509	struct sched_rt_entity *rt_se;
 510	int cpu = cpu_of(rq_of_rt_rq(rt_rq));
 511
 512	rt_se = rt_rq->tg->rt_se[cpu];
 513
 514	if (!rt_se) {
 515		dequeue_top_rt_rq(rt_rq);
 516		/* Kick cpufreq (see the comment in kernel/sched/sched.h). */
 517		cpufreq_update_util(rq_of_rt_rq(rt_rq), 0);
 518	}
 519	else if (on_rt_rq(rt_se))
 520		dequeue_rt_entity(rt_se, 0);
 521}
 522
 523static inline int rt_rq_throttled(struct rt_rq *rt_rq)
 524{
 525	return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
 526}
 527
 528static int rt_se_boosted(struct sched_rt_entity *rt_se)
 529{
 530	struct rt_rq *rt_rq = group_rt_rq(rt_se);
 531	struct task_struct *p;
 532
 533	if (rt_rq)
 534		return !!rt_rq->rt_nr_boosted;
 535
 536	p = rt_task_of(rt_se);
 537	return p->prio != p->normal_prio;
 538}
 539
 540#ifdef CONFIG_SMP
 541static inline const struct cpumask *sched_rt_period_mask(void)
 542{
 543	return this_rq()->rd->span;
 544}
 545#else
 546static inline const struct cpumask *sched_rt_period_mask(void)
 547{
 548	return cpu_online_mask;
 549}
 550#endif
 551
 552static inline
 553struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
 554{
 555	return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
 556}
 557
 558static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
 559{
 560	return &rt_rq->tg->rt_bandwidth;
 561}
 562
 563#else /* !CONFIG_RT_GROUP_SCHED */
 564
 565static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
 566{
 567	return rt_rq->rt_runtime;
 568}
 569
 570static inline u64 sched_rt_period(struct rt_rq *rt_rq)
 571{
 572	return ktime_to_ns(def_rt_bandwidth.rt_period);
 573}
 574
 575typedef struct rt_rq *rt_rq_iter_t;
 576
 577#define for_each_rt_rq(rt_rq, iter, rq) \
 578	for ((void) iter, rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
 579
 580#define for_each_sched_rt_entity(rt_se) \
 581	for (; rt_se; rt_se = NULL)
 582
 583static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
 584{
 585	return NULL;
 586}
 587
 588static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
 589{
 590	struct rq *rq = rq_of_rt_rq(rt_rq);
 591
 592	if (!rt_rq->rt_nr_running)
 593		return;
 594
 595	enqueue_top_rt_rq(rt_rq);
 596	resched_curr(rq);
 597}
 598
 599static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
 600{
 601	dequeue_top_rt_rq(rt_rq);
 602}
 603
 604static inline int rt_rq_throttled(struct rt_rq *rt_rq)
 605{
 606	return rt_rq->rt_throttled;
 607}
 608
 609static inline const struct cpumask *sched_rt_period_mask(void)
 610{
 611	return cpu_online_mask;
 612}
 613
 614static inline
 615struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
 616{
 617	return &cpu_rq(cpu)->rt;
 618}
 619
 620static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
 621{
 622	return &def_rt_bandwidth;
 623}
 624
 625#endif /* CONFIG_RT_GROUP_SCHED */
 626
 627bool sched_rt_bandwidth_account(struct rt_rq *rt_rq)
 628{
 629	struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 630
 631	return (hrtimer_active(&rt_b->rt_period_timer) ||
 632		rt_rq->rt_time < rt_b->rt_runtime);
 633}
 634
 635#ifdef CONFIG_SMP
 636/*
 637 * We ran out of runtime, see if we can borrow some from our neighbours.
 638 */
 639static void do_balance_runtime(struct rt_rq *rt_rq)
 640{
 641	struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 642	struct root_domain *rd = rq_of_rt_rq(rt_rq)->rd;
 643	int i, weight;
 644	u64 rt_period;
 645
 646	weight = cpumask_weight(rd->span);
 647
 648	raw_spin_lock(&rt_b->rt_runtime_lock);
 649	rt_period = ktime_to_ns(rt_b->rt_period);
 650	for_each_cpu(i, rd->span) {
 651		struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
 652		s64 diff;
 653
 654		if (iter == rt_rq)
 655			continue;
 656
 657		raw_spin_lock(&iter->rt_runtime_lock);
 658		/*
 659		 * Either all rqs have inf runtime and there's nothing to steal
 660		 * or __disable_runtime() below sets a specific rq to inf to
 661		 * indicate its been disabled and disalow stealing.
 662		 */
 663		if (iter->rt_runtime == RUNTIME_INF)
 664			goto next;
 665
 666		/*
 667		 * From runqueues with spare time, take 1/n part of their
 668		 * spare time, but no more than our period.
 669		 */
 670		diff = iter->rt_runtime - iter->rt_time;
 671		if (diff > 0) {
 672			diff = div_u64((u64)diff, weight);
 673			if (rt_rq->rt_runtime + diff > rt_period)
 674				diff = rt_period - rt_rq->rt_runtime;
 675			iter->rt_runtime -= diff;
 676			rt_rq->rt_runtime += diff;
 677			if (rt_rq->rt_runtime == rt_period) {
 678				raw_spin_unlock(&iter->rt_runtime_lock);
 679				break;
 680			}
 681		}
 682next:
 683		raw_spin_unlock(&iter->rt_runtime_lock);
 684	}
 685	raw_spin_unlock(&rt_b->rt_runtime_lock);
 686}
 687
 688/*
 689 * Ensure this RQ takes back all the runtime it lend to its neighbours.
 690 */
 691static void __disable_runtime(struct rq *rq)
 692{
 693	struct root_domain *rd = rq->rd;
 694	rt_rq_iter_t iter;
 695	struct rt_rq *rt_rq;
 696
 697	if (unlikely(!scheduler_running))
 698		return;
 699
 700	for_each_rt_rq(rt_rq, iter, rq) {
 701		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 702		s64 want;
 703		int i;
 704
 705		raw_spin_lock(&rt_b->rt_runtime_lock);
 706		raw_spin_lock(&rt_rq->rt_runtime_lock);
 707		/*
 708		 * Either we're all inf and nobody needs to borrow, or we're
 709		 * already disabled and thus have nothing to do, or we have
 710		 * exactly the right amount of runtime to take out.
 711		 */
 712		if (rt_rq->rt_runtime == RUNTIME_INF ||
 713				rt_rq->rt_runtime == rt_b->rt_runtime)
 714			goto balanced;
 715		raw_spin_unlock(&rt_rq->rt_runtime_lock);
 716
 717		/*
 718		 * Calculate the difference between what we started out with
 719		 * and what we current have, that's the amount of runtime
 720		 * we lend and now have to reclaim.
 721		 */
 722		want = rt_b->rt_runtime - rt_rq->rt_runtime;
 723
 724		/*
 725		 * Greedy reclaim, take back as much as we can.
 726		 */
 727		for_each_cpu(i, rd->span) {
 728			struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
 729			s64 diff;
 730
 731			/*
 732			 * Can't reclaim from ourselves or disabled runqueues.
 733			 */
 734			if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
 735				continue;
 736
 737			raw_spin_lock(&iter->rt_runtime_lock);
 738			if (want > 0) {
 739				diff = min_t(s64, iter->rt_runtime, want);
 740				iter->rt_runtime -= diff;
 741				want -= diff;
 742			} else {
 743				iter->rt_runtime -= want;
 744				want -= want;
 745			}
 746			raw_spin_unlock(&iter->rt_runtime_lock);
 747
 748			if (!want)
 749				break;
 750		}
 751
 752		raw_spin_lock(&rt_rq->rt_runtime_lock);
 753		/*
 754		 * We cannot be left wanting - that would mean some runtime
 755		 * leaked out of the system.
 756		 */
 757		BUG_ON(want);
 758balanced:
 759		/*
 760		 * Disable all the borrow logic by pretending we have inf
 761		 * runtime - in which case borrowing doesn't make sense.
 762		 */
 763		rt_rq->rt_runtime = RUNTIME_INF;
 764		rt_rq->rt_throttled = 0;
 765		raw_spin_unlock(&rt_rq->rt_runtime_lock);
 766		raw_spin_unlock(&rt_b->rt_runtime_lock);
 767
 768		/* Make rt_rq available for pick_next_task() */
 769		sched_rt_rq_enqueue(rt_rq);
 770	}
 771}
 772
 773static void __enable_runtime(struct rq *rq)
 774{
 775	rt_rq_iter_t iter;
 776	struct rt_rq *rt_rq;
 777
 778	if (unlikely(!scheduler_running))
 779		return;
 780
 781	/*
 782	 * Reset each runqueue's bandwidth settings
 783	 */
 784	for_each_rt_rq(rt_rq, iter, rq) {
 785		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 786
 787		raw_spin_lock(&rt_b->rt_runtime_lock);
 788		raw_spin_lock(&rt_rq->rt_runtime_lock);
 789		rt_rq->rt_runtime = rt_b->rt_runtime;
 790		rt_rq->rt_time = 0;
 791		rt_rq->rt_throttled = 0;
 792		raw_spin_unlock(&rt_rq->rt_runtime_lock);
 793		raw_spin_unlock(&rt_b->rt_runtime_lock);
 794	}
 795}
 796
 797static void balance_runtime(struct rt_rq *rt_rq)
 798{
 799	if (!sched_feat(RT_RUNTIME_SHARE))
 800		return;
 801
 802	if (rt_rq->rt_time > rt_rq->rt_runtime) {
 803		raw_spin_unlock(&rt_rq->rt_runtime_lock);
 804		do_balance_runtime(rt_rq);
 805		raw_spin_lock(&rt_rq->rt_runtime_lock);
 806	}
 807}
 808#else /* !CONFIG_SMP */
 809static inline void balance_runtime(struct rt_rq *rt_rq) {}
 810#endif /* CONFIG_SMP */
 811
 812static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
 813{
 814	int i, idle = 1, throttled = 0;
 815	const struct cpumask *span;
 816
 817	span = sched_rt_period_mask();
 818#ifdef CONFIG_RT_GROUP_SCHED
 819	/*
 820	 * FIXME: isolated CPUs should really leave the root task group,
 821	 * whether they are isolcpus or were isolated via cpusets, lest
 822	 * the timer run on a CPU which does not service all runqueues,
 823	 * potentially leaving other CPUs indefinitely throttled.  If
 824	 * isolation is really required, the user will turn the throttle
 825	 * off to kill the perturbations it causes anyway.  Meanwhile,
 826	 * this maintains functionality for boot and/or troubleshooting.
 827	 */
 828	if (rt_b == &root_task_group.rt_bandwidth)
 829		span = cpu_online_mask;
 830#endif
 831	for_each_cpu(i, span) {
 832		int enqueue = 0;
 833		struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
 834		struct rq *rq = rq_of_rt_rq(rt_rq);
 835		int skip;
 836
 837		/*
 838		 * When span == cpu_online_mask, taking each rq->lock
 839		 * can be time-consuming. Try to avoid it when possible.
 840		 */
 841		raw_spin_lock(&rt_rq->rt_runtime_lock);
 842		if (!sched_feat(RT_RUNTIME_SHARE) && rt_rq->rt_runtime != RUNTIME_INF)
 843			rt_rq->rt_runtime = rt_b->rt_runtime;
 844		skip = !rt_rq->rt_time && !rt_rq->rt_nr_running;
 845		raw_spin_unlock(&rt_rq->rt_runtime_lock);
 846		if (skip)
 847			continue;
 848
 849		raw_spin_lock(&rq->lock);
 850		update_rq_clock(rq);
 851
 852		if (rt_rq->rt_time) {
 853			u64 runtime;
 854
 855			raw_spin_lock(&rt_rq->rt_runtime_lock);
 856			if (rt_rq->rt_throttled)
 857				balance_runtime(rt_rq);
 858			runtime = rt_rq->rt_runtime;
 859			rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
 860			if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
 861				rt_rq->rt_throttled = 0;
 862				enqueue = 1;
 863
 864				/*
 865				 * When we're idle and a woken (rt) task is
 866				 * throttled check_preempt_curr() will set
 867				 * skip_update and the time between the wakeup
 868				 * and this unthrottle will get accounted as
 869				 * 'runtime'.
 870				 */
 871				if (rt_rq->rt_nr_running && rq->curr == rq->idle)
 872					rq_clock_cancel_skipupdate(rq);
 873			}
 874			if (rt_rq->rt_time || rt_rq->rt_nr_running)
 875				idle = 0;
 876			raw_spin_unlock(&rt_rq->rt_runtime_lock);
 877		} else if (rt_rq->rt_nr_running) {
 878			idle = 0;
 879			if (!rt_rq_throttled(rt_rq))
 880				enqueue = 1;
 881		}
 882		if (rt_rq->rt_throttled)
 883			throttled = 1;
 884
 885		if (enqueue)
 886			sched_rt_rq_enqueue(rt_rq);
 887		raw_spin_unlock(&rq->lock);
 888	}
 889
 890	if (!throttled && (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF))
 891		return 1;
 892
 893	return idle;
 894}
 895
 896static inline int rt_se_prio(struct sched_rt_entity *rt_se)
 897{
 898#ifdef CONFIG_RT_GROUP_SCHED
 899	struct rt_rq *rt_rq = group_rt_rq(rt_se);
 900
 901	if (rt_rq)
 902		return rt_rq->highest_prio.curr;
 903#endif
 904
 905	return rt_task_of(rt_se)->prio;
 906}
 907
 908static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
 909{
 910	u64 runtime = sched_rt_runtime(rt_rq);
 911
 912	if (rt_rq->rt_throttled)
 913		return rt_rq_throttled(rt_rq);
 914
 915	if (runtime >= sched_rt_period(rt_rq))
 916		return 0;
 917
 918	balance_runtime(rt_rq);
 919	runtime = sched_rt_runtime(rt_rq);
 920	if (runtime == RUNTIME_INF)
 921		return 0;
 922
 923	if (rt_rq->rt_time > runtime) {
 924		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 925
 926		/*
 927		 * Don't actually throttle groups that have no runtime assigned
 928		 * but accrue some time due to boosting.
 929		 */
 930		if (likely(rt_b->rt_runtime)) {
 931			rt_rq->rt_throttled = 1;
 932			printk_deferred_once("sched: RT throttling activated\n");
 933		} else {
 934			/*
 935			 * In case we did anyway, make it go away,
 936			 * replenishment is a joke, since it will replenish us
 937			 * with exactly 0 ns.
 938			 */
 939			rt_rq->rt_time = 0;
 940		}
 941
 942		if (rt_rq_throttled(rt_rq)) {
 943			sched_rt_rq_dequeue(rt_rq);
 944			return 1;
 945		}
 946	}
 947
 948	return 0;
 949}
 950
 951/*
 952 * Update the current task's runtime statistics. Skip current tasks that
 953 * are not in our scheduling class.
 954 */
 955static void update_curr_rt(struct rq *rq)
 956{
 957	struct task_struct *curr = rq->curr;
 958	struct sched_rt_entity *rt_se = &curr->rt;
 959	u64 delta_exec;
 960	u64 now;
 961
 962	if (curr->sched_class != &rt_sched_class)
 963		return;
 964
 965	now = rq_clock_task(rq);
 966	delta_exec = now - curr->se.exec_start;
 
 
 
 967	if (unlikely((s64)delta_exec <= 0))
 968		return;
 969
 970	schedstat_set(curr->se.statistics.exec_max,
 971		      max(curr->se.statistics.exec_max, delta_exec));
 972
 973	curr->se.sum_exec_runtime += delta_exec;
 974	account_group_exec_runtime(curr, delta_exec);
 975
 976	curr->se.exec_start = now;
 977	cgroup_account_cputime(curr, delta_exec);
 
 
 978
 979	if (!rt_bandwidth_enabled())
 980		return;
 981
 982	for_each_sched_rt_entity(rt_se) {
 983		struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 984
 985		if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
 986			raw_spin_lock(&rt_rq->rt_runtime_lock);
 987			rt_rq->rt_time += delta_exec;
 988			if (sched_rt_runtime_exceeded(rt_rq))
 989				resched_curr(rq);
 990			raw_spin_unlock(&rt_rq->rt_runtime_lock);
 991		}
 992	}
 993}
 994
 995static void
 996dequeue_top_rt_rq(struct rt_rq *rt_rq)
 997{
 998	struct rq *rq = rq_of_rt_rq(rt_rq);
 999
1000	BUG_ON(&rq->rt != rt_rq);
1001
1002	if (!rt_rq->rt_queued)
1003		return;
1004
1005	BUG_ON(!rq->nr_running);
1006
1007	sub_nr_running(rq, rt_rq->rt_nr_running);
1008	rt_rq->rt_queued = 0;
1009
1010}
1011
1012static void
1013enqueue_top_rt_rq(struct rt_rq *rt_rq)
1014{
1015	struct rq *rq = rq_of_rt_rq(rt_rq);
1016
1017	BUG_ON(&rq->rt != rt_rq);
1018
1019	if (rt_rq->rt_queued)
1020		return;
1021
1022	if (rt_rq_throttled(rt_rq))
1023		return;
1024
1025	if (rt_rq->rt_nr_running) {
1026		add_nr_running(rq, rt_rq->rt_nr_running);
1027		rt_rq->rt_queued = 1;
1028	}
1029
1030	/* Kick cpufreq (see the comment in kernel/sched/sched.h). */
1031	cpufreq_update_util(rq, 0);
1032}
1033
1034#if defined CONFIG_SMP
1035
1036static void
1037inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
1038{
1039	struct rq *rq = rq_of_rt_rq(rt_rq);
1040
1041#ifdef CONFIG_RT_GROUP_SCHED
1042	/*
1043	 * Change rq's cpupri only if rt_rq is the top queue.
1044	 */
1045	if (&rq->rt != rt_rq)
1046		return;
1047#endif
1048	if (rq->online && prio < prev_prio)
1049		cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
1050}
1051
1052static void
1053dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
1054{
1055	struct rq *rq = rq_of_rt_rq(rt_rq);
1056
1057#ifdef CONFIG_RT_GROUP_SCHED
1058	/*
1059	 * Change rq's cpupri only if rt_rq is the top queue.
1060	 */
1061	if (&rq->rt != rt_rq)
1062		return;
1063#endif
1064	if (rq->online && rt_rq->highest_prio.curr != prev_prio)
1065		cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
1066}
1067
1068#else /* CONFIG_SMP */
1069
1070static inline
1071void inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
1072static inline
1073void dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
1074
1075#endif /* CONFIG_SMP */
1076
1077#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
1078static void
1079inc_rt_prio(struct rt_rq *rt_rq, int prio)
1080{
1081	int prev_prio = rt_rq->highest_prio.curr;
1082
1083	if (prio < prev_prio)
1084		rt_rq->highest_prio.curr = prio;
1085
1086	inc_rt_prio_smp(rt_rq, prio, prev_prio);
1087}
1088
1089static void
1090dec_rt_prio(struct rt_rq *rt_rq, int prio)
1091{
1092	int prev_prio = rt_rq->highest_prio.curr;
1093
1094	if (rt_rq->rt_nr_running) {
1095
1096		WARN_ON(prio < prev_prio);
1097
1098		/*
1099		 * This may have been our highest task, and therefore
1100		 * we may have some recomputation to do
1101		 */
1102		if (prio == prev_prio) {
1103			struct rt_prio_array *array = &rt_rq->active;
1104
1105			rt_rq->highest_prio.curr =
1106				sched_find_first_bit(array->bitmap);
1107		}
1108
1109	} else
1110		rt_rq->highest_prio.curr = MAX_RT_PRIO;
1111
1112	dec_rt_prio_smp(rt_rq, prio, prev_prio);
1113}
1114
1115#else
1116
1117static inline void inc_rt_prio(struct rt_rq *rt_rq, int prio) {}
1118static inline void dec_rt_prio(struct rt_rq *rt_rq, int prio) {}
1119
1120#endif /* CONFIG_SMP || CONFIG_RT_GROUP_SCHED */
1121
1122#ifdef CONFIG_RT_GROUP_SCHED
1123
1124static void
1125inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1126{
1127	if (rt_se_boosted(rt_se))
1128		rt_rq->rt_nr_boosted++;
1129
1130	if (rt_rq->tg)
1131		start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
1132}
1133
1134static void
1135dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1136{
1137	if (rt_se_boosted(rt_se))
1138		rt_rq->rt_nr_boosted--;
1139
1140	WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
1141}
1142
1143#else /* CONFIG_RT_GROUP_SCHED */
1144
1145static void
1146inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1147{
1148	start_rt_bandwidth(&def_rt_bandwidth);
1149}
1150
1151static inline
1152void dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) {}
1153
1154#endif /* CONFIG_RT_GROUP_SCHED */
1155
1156static inline
1157unsigned int rt_se_nr_running(struct sched_rt_entity *rt_se)
1158{
1159	struct rt_rq *group_rq = group_rt_rq(rt_se);
1160
1161	if (group_rq)
1162		return group_rq->rt_nr_running;
1163	else
1164		return 1;
1165}
1166
1167static inline
1168unsigned int rt_se_rr_nr_running(struct sched_rt_entity *rt_se)
1169{
1170	struct rt_rq *group_rq = group_rt_rq(rt_se);
1171	struct task_struct *tsk;
1172
1173	if (group_rq)
1174		return group_rq->rr_nr_running;
1175
1176	tsk = rt_task_of(rt_se);
1177
1178	return (tsk->policy == SCHED_RR) ? 1 : 0;
1179}
1180
1181static inline
1182void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1183{
1184	int prio = rt_se_prio(rt_se);
1185
1186	WARN_ON(!rt_prio(prio));
1187	rt_rq->rt_nr_running += rt_se_nr_running(rt_se);
1188	rt_rq->rr_nr_running += rt_se_rr_nr_running(rt_se);
1189
1190	inc_rt_prio(rt_rq, prio);
1191	inc_rt_migration(rt_se, rt_rq);
1192	inc_rt_group(rt_se, rt_rq);
1193}
1194
1195static inline
1196void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1197{
1198	WARN_ON(!rt_prio(rt_se_prio(rt_se)));
1199	WARN_ON(!rt_rq->rt_nr_running);
1200	rt_rq->rt_nr_running -= rt_se_nr_running(rt_se);
1201	rt_rq->rr_nr_running -= rt_se_rr_nr_running(rt_se);
1202
1203	dec_rt_prio(rt_rq, rt_se_prio(rt_se));
1204	dec_rt_migration(rt_se, rt_rq);
1205	dec_rt_group(rt_se, rt_rq);
1206}
1207
1208/*
1209 * Change rt_se->run_list location unless SAVE && !MOVE
1210 *
1211 * assumes ENQUEUE/DEQUEUE flags match
1212 */
1213static inline bool move_entity(unsigned int flags)
1214{
1215	if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE)
1216		return false;
1217
1218	return true;
1219}
1220
1221static void __delist_rt_entity(struct sched_rt_entity *rt_se, struct rt_prio_array *array)
1222{
1223	list_del_init(&rt_se->run_list);
1224
1225	if (list_empty(array->queue + rt_se_prio(rt_se)))
1226		__clear_bit(rt_se_prio(rt_se), array->bitmap);
1227
1228	rt_se->on_list = 0;
1229}
1230
1231static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1232{
1233	struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
1234	struct rt_prio_array *array = &rt_rq->active;
1235	struct rt_rq *group_rq = group_rt_rq(rt_se);
1236	struct list_head *queue = array->queue + rt_se_prio(rt_se);
1237
1238	/*
1239	 * Don't enqueue the group if its throttled, or when empty.
1240	 * The latter is a consequence of the former when a child group
1241	 * get throttled and the current group doesn't have any other
1242	 * active members.
1243	 */
1244	if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running)) {
1245		if (rt_se->on_list)
1246			__delist_rt_entity(rt_se, array);
1247		return;
1248	}
1249
1250	if (move_entity(flags)) {
1251		WARN_ON_ONCE(rt_se->on_list);
1252		if (flags & ENQUEUE_HEAD)
1253			list_add(&rt_se->run_list, queue);
1254		else
1255			list_add_tail(&rt_se->run_list, queue);
1256
1257		__set_bit(rt_se_prio(rt_se), array->bitmap);
1258		rt_se->on_list = 1;
1259	}
1260	rt_se->on_rq = 1;
1261
1262	inc_rt_tasks(rt_se, rt_rq);
1263}
1264
1265static void __dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1266{
1267	struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
1268	struct rt_prio_array *array = &rt_rq->active;
1269
1270	if (move_entity(flags)) {
1271		WARN_ON_ONCE(!rt_se->on_list);
1272		__delist_rt_entity(rt_se, array);
1273	}
1274	rt_se->on_rq = 0;
1275
1276	dec_rt_tasks(rt_se, rt_rq);
1277}
1278
1279/*
1280 * Because the prio of an upper entry depends on the lower
1281 * entries, we must remove entries top - down.
1282 */
1283static void dequeue_rt_stack(struct sched_rt_entity *rt_se, unsigned int flags)
1284{
1285	struct sched_rt_entity *back = NULL;
1286
1287	for_each_sched_rt_entity(rt_se) {
1288		rt_se->back = back;
1289		back = rt_se;
1290	}
1291
1292	dequeue_top_rt_rq(rt_rq_of_se(back));
1293
1294	for (rt_se = back; rt_se; rt_se = rt_se->back) {
1295		if (on_rt_rq(rt_se))
1296			__dequeue_rt_entity(rt_se, flags);
1297	}
1298}
1299
1300static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1301{
1302	struct rq *rq = rq_of_rt_se(rt_se);
1303
1304	dequeue_rt_stack(rt_se, flags);
1305	for_each_sched_rt_entity(rt_se)
1306		__enqueue_rt_entity(rt_se, flags);
1307	enqueue_top_rt_rq(&rq->rt);
1308}
1309
1310static void dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1311{
1312	struct rq *rq = rq_of_rt_se(rt_se);
1313
1314	dequeue_rt_stack(rt_se, flags);
1315
1316	for_each_sched_rt_entity(rt_se) {
1317		struct rt_rq *rt_rq = group_rt_rq(rt_se);
1318
1319		if (rt_rq && rt_rq->rt_nr_running)
1320			__enqueue_rt_entity(rt_se, flags);
1321	}
1322	enqueue_top_rt_rq(&rq->rt);
1323}
1324
1325/*
1326 * Adding/removing a task to/from a priority array:
1327 */
1328static void
1329enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
1330{
1331	struct sched_rt_entity *rt_se = &p->rt;
1332
1333	if (flags & ENQUEUE_WAKEUP)
1334		rt_se->timeout = 0;
1335
1336	enqueue_rt_entity(rt_se, flags);
1337
1338	if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
1339		enqueue_pushable_task(rq, p);
1340}
1341
1342static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
1343{
1344	struct sched_rt_entity *rt_se = &p->rt;
1345
1346	update_curr_rt(rq);
1347	dequeue_rt_entity(rt_se, flags);
1348
1349	dequeue_pushable_task(rq, p);
1350}
1351
1352/*
1353 * Put task to the head or the end of the run list without the overhead of
1354 * dequeue followed by enqueue.
1355 */
1356static void
1357requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
1358{
1359	if (on_rt_rq(rt_se)) {
1360		struct rt_prio_array *array = &rt_rq->active;
1361		struct list_head *queue = array->queue + rt_se_prio(rt_se);
1362
1363		if (head)
1364			list_move(&rt_se->run_list, queue);
1365		else
1366			list_move_tail(&rt_se->run_list, queue);
1367	}
1368}
1369
1370static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
1371{
1372	struct sched_rt_entity *rt_se = &p->rt;
1373	struct rt_rq *rt_rq;
1374
1375	for_each_sched_rt_entity(rt_se) {
1376		rt_rq = rt_rq_of_se(rt_se);
1377		requeue_rt_entity(rt_rq, rt_se, head);
1378	}
1379}
1380
1381static void yield_task_rt(struct rq *rq)
1382{
1383	requeue_task_rt(rq, rq->curr, 0);
1384}
1385
1386#ifdef CONFIG_SMP
1387static int find_lowest_rq(struct task_struct *task);
1388
1389static int
1390select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
1391{
1392	struct task_struct *curr;
1393	struct rq *rq;
1394
1395	/* For anything but wake ups, just return the task_cpu */
1396	if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
1397		goto out;
1398
1399	rq = cpu_rq(cpu);
1400
1401	rcu_read_lock();
1402	curr = READ_ONCE(rq->curr); /* unlocked access */
1403
1404	/*
1405	 * If the current task on @p's runqueue is an RT task, then
1406	 * try to see if we can wake this RT task up on another
1407	 * runqueue. Otherwise simply start this RT task
1408	 * on its current runqueue.
1409	 *
1410	 * We want to avoid overloading runqueues. If the woken
1411	 * task is a higher priority, then it will stay on this CPU
1412	 * and the lower prio task should be moved to another CPU.
1413	 * Even though this will probably make the lower prio task
1414	 * lose its cache, we do not want to bounce a higher task
1415	 * around just because it gave up its CPU, perhaps for a
1416	 * lock?
1417	 *
1418	 * For equal prio tasks, we just let the scheduler sort it out.
1419	 *
1420	 * Otherwise, just let it ride on the affined RQ and the
1421	 * post-schedule router will push the preempted task away
1422	 *
1423	 * This test is optimistic, if we get it wrong the load-balancer
1424	 * will have to sort it out.
1425	 */
1426	if (curr && unlikely(rt_task(curr)) &&
1427	    (curr->nr_cpus_allowed < 2 ||
1428	     curr->prio <= p->prio)) {
1429		int target = find_lowest_rq(p);
1430
1431		/*
1432		 * Don't bother moving it if the destination CPU is
1433		 * not running a lower priority task.
1434		 */
1435		if (target != -1 &&
1436		    p->prio < cpu_rq(target)->rt.highest_prio.curr)
1437			cpu = target;
1438	}
1439	rcu_read_unlock();
1440
1441out:
1442	return cpu;
1443}
1444
1445static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
1446{
1447	/*
1448	 * Current can't be migrated, useless to reschedule,
1449	 * let's hope p can move out.
1450	 */
1451	if (rq->curr->nr_cpus_allowed == 1 ||
1452	    !cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
1453		return;
1454
1455	/*
1456	 * p is migratable, so let's not schedule it and
1457	 * see if it is pushed or pulled somewhere else.
1458	 */
1459	if (p->nr_cpus_allowed != 1
1460	    && cpupri_find(&rq->rd->cpupri, p, NULL))
1461		return;
1462
1463	/*
1464	 * There appear to be other CPUs that can accept
1465	 * the current task but none can run 'p', so lets reschedule
1466	 * to try and push the current task away:
1467	 */
1468	requeue_task_rt(rq, p, 1);
1469	resched_curr(rq);
1470}
1471
1472static int balance_rt(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
1473{
1474	if (!on_rt_rq(&p->rt) && need_pull_rt_task(rq, p)) {
1475		/*
1476		 * This is OK, because current is on_cpu, which avoids it being
1477		 * picked for load-balance and preemption/IRQs are still
1478		 * disabled avoiding further scheduler activity on it and we've
1479		 * not yet started the picking loop.
1480		 */
1481		rq_unpin_lock(rq, rf);
1482		pull_rt_task(rq);
1483		rq_repin_lock(rq, rf);
1484	}
1485
1486	return sched_stop_runnable(rq) || sched_dl_runnable(rq) || sched_rt_runnable(rq);
1487}
1488#endif /* CONFIG_SMP */
1489
1490/*
1491 * Preempt the current task with a newly woken task if needed:
1492 */
1493static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flags)
1494{
1495	if (p->prio < rq->curr->prio) {
1496		resched_curr(rq);
1497		return;
1498	}
1499
1500#ifdef CONFIG_SMP
1501	/*
1502	 * If:
1503	 *
1504	 * - the newly woken task is of equal priority to the current task
1505	 * - the newly woken task is non-migratable while current is migratable
1506	 * - current will be preempted on the next reschedule
1507	 *
1508	 * we should check to see if current can readily move to a different
1509	 * cpu.  If so, we will reschedule to allow the push logic to try
1510	 * to move current somewhere else, making room for our non-migratable
1511	 * task.
1512	 */
1513	if (p->prio == rq->curr->prio && !test_tsk_need_resched(rq->curr))
1514		check_preempt_equal_prio(rq, p);
1515#endif
1516}
1517
1518static inline void set_next_task_rt(struct rq *rq, struct task_struct *p)
1519{
1520	p->se.exec_start = rq_clock_task(rq);
1521
1522	/* The running task is never eligible for pushing */
1523	dequeue_pushable_task(rq, p);
1524
1525	/*
1526	 * If prev task was rt, put_prev_task() has already updated the
1527	 * utilization. We only care of the case where we start to schedule a
1528	 * rt task
1529	 */
1530	if (rq->curr->sched_class != &rt_sched_class)
1531		update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0);
1532
1533	rt_queue_push_tasks(rq);
1534}
1535
1536static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
1537						   struct rt_rq *rt_rq)
1538{
1539	struct rt_prio_array *array = &rt_rq->active;
1540	struct sched_rt_entity *next = NULL;
1541	struct list_head *queue;
1542	int idx;
1543
1544	idx = sched_find_first_bit(array->bitmap);
1545	BUG_ON(idx >= MAX_RT_PRIO);
1546
1547	queue = array->queue + idx;
1548	next = list_entry(queue->next, struct sched_rt_entity, run_list);
1549
1550	return next;
1551}
1552
1553static struct task_struct *_pick_next_task_rt(struct rq *rq)
1554{
1555	struct sched_rt_entity *rt_se;
 
1556	struct rt_rq *rt_rq  = &rq->rt;
1557
1558	do {
1559		rt_se = pick_next_rt_entity(rq, rt_rq);
1560		BUG_ON(!rt_se);
1561		rt_rq = group_rt_rq(rt_se);
1562	} while (rt_rq);
1563
1564	return rt_task_of(rt_se);
 
 
 
1565}
1566
1567static struct task_struct *
1568pick_next_task_rt(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
1569{
1570	struct task_struct *p;
 
1571
1572	WARN_ON_ONCE(prev || rf);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1573
1574	if (!sched_rt_runnable(rq))
1575		return NULL;
1576
 
 
1577	p = _pick_next_task_rt(rq);
1578	set_next_task_rt(rq, p);
 
 
 
 
 
1579	return p;
1580}
1581
1582static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
1583{
1584	update_curr_rt(rq);
1585
1586	update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 1);
1587
1588	/*
1589	 * The previous task needs to be made eligible for pushing
1590	 * if it is still active
1591	 */
1592	if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1)
1593		enqueue_pushable_task(rq, p);
1594}
1595
1596#ifdef CONFIG_SMP
1597
1598/* Only try algorithms three times */
1599#define RT_MAX_TRIES 3
1600
1601static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
1602{
1603	if (!task_running(rq, p) &&
1604	    cpumask_test_cpu(cpu, p->cpus_ptr))
1605		return 1;
1606
1607	return 0;
1608}
1609
1610/*
1611 * Return the highest pushable rq's task, which is suitable to be executed
1612 * on the CPU, NULL otherwise
1613 */
1614static struct task_struct *pick_highest_pushable_task(struct rq *rq, int cpu)
1615{
1616	struct plist_head *head = &rq->rt.pushable_tasks;
1617	struct task_struct *p;
1618
1619	if (!has_pushable_tasks(rq))
1620		return NULL;
1621
1622	plist_for_each_entry(p, head, pushable_tasks) {
1623		if (pick_rt_task(rq, p, cpu))
1624			return p;
1625	}
1626
1627	return NULL;
1628}
1629
1630static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
1631
1632static int find_lowest_rq(struct task_struct *task)
1633{
1634	struct sched_domain *sd;
1635	struct cpumask *lowest_mask = this_cpu_cpumask_var_ptr(local_cpu_mask);
1636	int this_cpu = smp_processor_id();
1637	int cpu      = task_cpu(task);
1638
1639	/* Make sure the mask is initialized first */
1640	if (unlikely(!lowest_mask))
1641		return -1;
1642
1643	if (task->nr_cpus_allowed == 1)
1644		return -1; /* No other targets possible */
1645
1646	if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
1647		return -1; /* No targets found */
1648
1649	/*
1650	 * At this point we have built a mask of CPUs representing the
1651	 * lowest priority tasks in the system.  Now we want to elect
1652	 * the best one based on our affinity and topology.
1653	 *
1654	 * We prioritize the last CPU that the task executed on since
1655	 * it is most likely cache-hot in that location.
1656	 */
1657	if (cpumask_test_cpu(cpu, lowest_mask))
1658		return cpu;
1659
1660	/*
1661	 * Otherwise, we consult the sched_domains span maps to figure
1662	 * out which CPU is logically closest to our hot cache data.
1663	 */
1664	if (!cpumask_test_cpu(this_cpu, lowest_mask))
1665		this_cpu = -1; /* Skip this_cpu opt if not among lowest */
1666
1667	rcu_read_lock();
1668	for_each_domain(cpu, sd) {
1669		if (sd->flags & SD_WAKE_AFFINE) {
1670			int best_cpu;
1671
1672			/*
1673			 * "this_cpu" is cheaper to preempt than a
1674			 * remote processor.
1675			 */
1676			if (this_cpu != -1 &&
1677			    cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
1678				rcu_read_unlock();
1679				return this_cpu;
1680			}
1681
1682			best_cpu = cpumask_first_and(lowest_mask,
1683						     sched_domain_span(sd));
1684			if (best_cpu < nr_cpu_ids) {
1685				rcu_read_unlock();
1686				return best_cpu;
1687			}
1688		}
1689	}
1690	rcu_read_unlock();
1691
1692	/*
1693	 * And finally, if there were no matches within the domains
1694	 * just give the caller *something* to work with from the compatible
1695	 * locations.
1696	 */
1697	if (this_cpu != -1)
1698		return this_cpu;
1699
1700	cpu = cpumask_any(lowest_mask);
1701	if (cpu < nr_cpu_ids)
1702		return cpu;
1703
1704	return -1;
1705}
1706
1707/* Will lock the rq it finds */
1708static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1709{
1710	struct rq *lowest_rq = NULL;
1711	int tries;
1712	int cpu;
1713
1714	for (tries = 0; tries < RT_MAX_TRIES; tries++) {
1715		cpu = find_lowest_rq(task);
1716
1717		if ((cpu == -1) || (cpu == rq->cpu))
1718			break;
1719
1720		lowest_rq = cpu_rq(cpu);
1721
1722		if (lowest_rq->rt.highest_prio.curr <= task->prio) {
1723			/*
1724			 * Target rq has tasks of equal or higher priority,
1725			 * retrying does not release any lock and is unlikely
1726			 * to yield a different result.
1727			 */
1728			lowest_rq = NULL;
1729			break;
1730		}
1731
1732		/* if the prio of this runqueue changed, try again */
1733		if (double_lock_balance(rq, lowest_rq)) {
1734			/*
1735			 * We had to unlock the run queue. In
1736			 * the mean time, task could have
1737			 * migrated already or had its affinity changed.
1738			 * Also make sure that it wasn't scheduled on its rq.
1739			 */
1740			if (unlikely(task_rq(task) != rq ||
1741				     !cpumask_test_cpu(lowest_rq->cpu, task->cpus_ptr) ||
 
1742				     task_running(rq, task) ||
1743				     !rt_task(task) ||
1744				     !task_on_rq_queued(task))) {
1745
1746				double_unlock_balance(rq, lowest_rq);
1747				lowest_rq = NULL;
1748				break;
1749			}
1750		}
1751
1752		/* If this rq is still suitable use it. */
1753		if (lowest_rq->rt.highest_prio.curr > task->prio)
1754			break;
1755
1756		/* try again */
1757		double_unlock_balance(rq, lowest_rq);
1758		lowest_rq = NULL;
1759	}
1760
1761	return lowest_rq;
1762}
1763
1764static struct task_struct *pick_next_pushable_task(struct rq *rq)
1765{
1766	struct task_struct *p;
1767
1768	if (!has_pushable_tasks(rq))
1769		return NULL;
1770
1771	p = plist_first_entry(&rq->rt.pushable_tasks,
1772			      struct task_struct, pushable_tasks);
1773
1774	BUG_ON(rq->cpu != task_cpu(p));
1775	BUG_ON(task_current(rq, p));
1776	BUG_ON(p->nr_cpus_allowed <= 1);
1777
1778	BUG_ON(!task_on_rq_queued(p));
1779	BUG_ON(!rt_task(p));
1780
1781	return p;
1782}
1783
1784/*
1785 * If the current CPU has more than one RT task, see if the non
1786 * running task can migrate over to a CPU that is running a task
1787 * of lesser priority.
1788 */
1789static int push_rt_task(struct rq *rq)
1790{
1791	struct task_struct *next_task;
1792	struct rq *lowest_rq;
1793	int ret = 0;
1794
1795	if (!rq->rt.overloaded)
1796		return 0;
1797
1798	next_task = pick_next_pushable_task(rq);
1799	if (!next_task)
1800		return 0;
1801
1802retry:
1803	if (WARN_ON(next_task == rq->curr))
 
1804		return 0;
 
1805
1806	/*
1807	 * It's possible that the next_task slipped in of
1808	 * higher priority than current. If that's the case
1809	 * just reschedule current.
1810	 */
1811	if (unlikely(next_task->prio < rq->curr->prio)) {
1812		resched_curr(rq);
1813		return 0;
1814	}
1815
1816	/* We might release rq lock */
1817	get_task_struct(next_task);
1818
1819	/* find_lock_lowest_rq locks the rq if found */
1820	lowest_rq = find_lock_lowest_rq(next_task, rq);
1821	if (!lowest_rq) {
1822		struct task_struct *task;
1823		/*
1824		 * find_lock_lowest_rq releases rq->lock
1825		 * so it is possible that next_task has migrated.
1826		 *
1827		 * We need to make sure that the task is still on the same
1828		 * run-queue and is also still the next task eligible for
1829		 * pushing.
1830		 */
1831		task = pick_next_pushable_task(rq);
1832		if (task == next_task) {
1833			/*
1834			 * The task hasn't migrated, and is still the next
1835			 * eligible task, but we failed to find a run-queue
1836			 * to push it to.  Do not retry in this case, since
1837			 * other CPUs will pull from us when ready.
1838			 */
1839			goto out;
1840		}
1841
1842		if (!task)
1843			/* No more tasks, just exit */
1844			goto out;
1845
1846		/*
1847		 * Something has shifted, try again.
1848		 */
1849		put_task_struct(next_task);
1850		next_task = task;
1851		goto retry;
1852	}
1853
1854	deactivate_task(rq, next_task, 0);
1855	set_task_cpu(next_task, lowest_rq->cpu);
1856	activate_task(lowest_rq, next_task, 0);
1857	ret = 1;
1858
1859	resched_curr(lowest_rq);
1860
1861	double_unlock_balance(rq, lowest_rq);
1862
1863out:
1864	put_task_struct(next_task);
1865
1866	return ret;
1867}
1868
1869static void push_rt_tasks(struct rq *rq)
1870{
1871	/* push_rt_task will return true if it moved an RT */
1872	while (push_rt_task(rq))
1873		;
1874}
1875
1876#ifdef HAVE_RT_PUSH_IPI
1877
1878/*
1879 * When a high priority task schedules out from a CPU and a lower priority
1880 * task is scheduled in, a check is made to see if there's any RT tasks
1881 * on other CPUs that are waiting to run because a higher priority RT task
1882 * is currently running on its CPU. In this case, the CPU with multiple RT
1883 * tasks queued on it (overloaded) needs to be notified that a CPU has opened
1884 * up that may be able to run one of its non-running queued RT tasks.
1885 *
1886 * All CPUs with overloaded RT tasks need to be notified as there is currently
1887 * no way to know which of these CPUs have the highest priority task waiting
1888 * to run. Instead of trying to take a spinlock on each of these CPUs,
1889 * which has shown to cause large latency when done on machines with many
1890 * CPUs, sending an IPI to the CPUs to have them push off the overloaded
1891 * RT tasks waiting to run.
1892 *
1893 * Just sending an IPI to each of the CPUs is also an issue, as on large
1894 * count CPU machines, this can cause an IPI storm on a CPU, especially
1895 * if its the only CPU with multiple RT tasks queued, and a large number
1896 * of CPUs scheduling a lower priority task at the same time.
1897 *
1898 * Each root domain has its own irq work function that can iterate over
1899 * all CPUs with RT overloaded tasks. Since all CPUs with overloaded RT
1900 * tassk must be checked if there's one or many CPUs that are lowering
1901 * their priority, there's a single irq work iterator that will try to
1902 * push off RT tasks that are waiting to run.
1903 *
1904 * When a CPU schedules a lower priority task, it will kick off the
1905 * irq work iterator that will jump to each CPU with overloaded RT tasks.
1906 * As it only takes the first CPU that schedules a lower priority task
1907 * to start the process, the rto_start variable is incremented and if
1908 * the atomic result is one, then that CPU will try to take the rto_lock.
1909 * This prevents high contention on the lock as the process handles all
1910 * CPUs scheduling lower priority tasks.
1911 *
1912 * All CPUs that are scheduling a lower priority task will increment the
1913 * rt_loop_next variable. This will make sure that the irq work iterator
1914 * checks all RT overloaded CPUs whenever a CPU schedules a new lower
1915 * priority task, even if the iterator is in the middle of a scan. Incrementing
1916 * the rt_loop_next will cause the iterator to perform another scan.
1917 *
 
 
1918 */
1919static int rto_next_cpu(struct root_domain *rd)
1920{
1921	int next;
1922	int cpu;
1923
 
 
1924	/*
1925	 * When starting the IPI RT pushing, the rto_cpu is set to -1,
1926	 * rt_next_cpu() will simply return the first CPU found in
1927	 * the rto_mask.
1928	 *
1929	 * If rto_next_cpu() is called with rto_cpu is a valid CPU, it
1930	 * will return the next CPU found in the rto_mask.
1931	 *
1932	 * If there are no more CPUs left in the rto_mask, then a check is made
1933	 * against rto_loop and rto_loop_next. rto_loop is only updated with
1934	 * the rto_lock held, but any CPU may increment the rto_loop_next
1935	 * without any locking.
1936	 */
1937	for (;;) {
1938
1939		/* When rto_cpu is -1 this acts like cpumask_first() */
1940		cpu = cpumask_next(rd->rto_cpu, rd->rto_mask);
1941
1942		rd->rto_cpu = cpu;
1943
1944		if (cpu < nr_cpu_ids)
1945			return cpu;
1946
1947		rd->rto_cpu = -1;
1948
 
1949		/*
1950		 * ACQUIRE ensures we see the @rto_mask changes
1951		 * made prior to the @next value observed.
1952		 *
1953		 * Matches WMB in rt_set_overload().
1954		 */
1955		next = atomic_read_acquire(&rd->rto_loop_next);
1956
1957		if (rd->rto_loop == next)
1958			break;
1959
1960		rd->rto_loop = next;
1961	}
 
1962
1963	return -1;
 
1964}
1965
1966static inline bool rto_start_trylock(atomic_t *v)
1967{
1968	return !atomic_cmpxchg_acquire(v, 0, 1);
1969}
1970
1971static inline void rto_start_unlock(atomic_t *v)
1972{
1973	atomic_set_release(v, 0);
 
 
 
 
 
 
 
 
 
1974}
1975
 
 
 
1976static void tell_cpu_to_push(struct rq *rq)
1977{
1978	int cpu = -1;
1979
1980	/* Keep the loop going if the IPI is currently active */
1981	atomic_inc(&rq->rd->rto_loop_next);
1982
1983	/* Only one CPU can initiate a loop at a time */
1984	if (!rto_start_trylock(&rq->rd->rto_loop_start))
1985		return;
1986
1987	raw_spin_lock(&rq->rd->rto_lock);
 
 
 
 
 
 
 
 
 
 
 
 
 
1988
1989	/*
1990	 * The rto_cpu is updated under the lock, if it has a valid CPU
1991	 * then the IPI is still running and will continue due to the
1992	 * update to loop_next, and nothing needs to be done here.
1993	 * Otherwise it is finishing up and an ipi needs to be sent.
1994	 */
1995	if (rq->rd->rto_cpu < 0)
1996		cpu = rto_next_cpu(rq->rd);
1997
1998	raw_spin_unlock(&rq->rd->rto_lock);
 
 
 
1999
2000	rto_start_unlock(&rq->rd->rto_loop_start);
2001
2002	if (cpu >= 0) {
2003		/* Make sure the rd does not get freed while pushing */
2004		sched_get_rd(rq->rd);
2005		irq_work_queue_on(&rq->rd->rto_push_work, cpu);
2006	}
2007}
2008
2009/* Called from hardirq context */
2010void rto_push_irq_work_func(struct irq_work *work)
2011{
2012	struct root_domain *rd =
2013		container_of(work, struct root_domain, rto_push_work);
2014	struct rq *rq;
2015	int cpu;
2016
2017	rq = this_rq();
2018
2019	/*
2020	 * We do not need to grab the lock to check for has_pushable_tasks.
2021	 * When it gets updated, a check is made if a push is possible.
2022	 */
 
 
 
2023	if (has_pushable_tasks(rq)) {
2024		raw_spin_lock(&rq->lock);
2025		push_rt_tasks(rq);
2026		raw_spin_unlock(&rq->lock);
2027	}
2028
2029	raw_spin_lock(&rd->rto_lock);
2030
2031	/* Pass the IPI to the next rt overloaded queue */
2032	cpu = rto_next_cpu(rd);
 
 
 
 
 
 
 
 
2033
2034	raw_spin_unlock(&rd->rto_lock);
2035
2036	if (cpu < 0) {
2037		sched_put_rd(rd);
 
 
 
2038		return;
2039	}
 
 
 
 
 
 
 
2040
2041	/* Try the next RT overloaded CPU */
2042	irq_work_queue_on(&rd->rto_push_work, cpu);
 
 
 
 
 
 
 
2043}
2044#endif /* HAVE_RT_PUSH_IPI */
2045
2046static void pull_rt_task(struct rq *this_rq)
2047{
2048	int this_cpu = this_rq->cpu, cpu;
2049	bool resched = false;
2050	struct task_struct *p;
2051	struct rq *src_rq;
2052	int rt_overload_count = rt_overloaded(this_rq);
2053
2054	if (likely(!rt_overload_count))
2055		return;
2056
2057	/*
2058	 * Match the barrier from rt_set_overloaded; this guarantees that if we
2059	 * see overloaded we must also see the rto_mask bit.
2060	 */
2061	smp_rmb();
2062
2063	/* If we are the only overloaded CPU do nothing */
2064	if (rt_overload_count == 1 &&
2065	    cpumask_test_cpu(this_rq->cpu, this_rq->rd->rto_mask))
2066		return;
2067
2068#ifdef HAVE_RT_PUSH_IPI
2069	if (sched_feat(RT_PUSH_IPI)) {
2070		tell_cpu_to_push(this_rq);
2071		return;
2072	}
2073#endif
2074
2075	for_each_cpu(cpu, this_rq->rd->rto_mask) {
2076		if (this_cpu == cpu)
2077			continue;
2078
2079		src_rq = cpu_rq(cpu);
2080
2081		/*
2082		 * Don't bother taking the src_rq->lock if the next highest
2083		 * task is known to be lower-priority than our current task.
2084		 * This may look racy, but if this value is about to go
2085		 * logically higher, the src_rq will push this task away.
2086		 * And if its going logically lower, we do not care
2087		 */
2088		if (src_rq->rt.highest_prio.next >=
2089		    this_rq->rt.highest_prio.curr)
2090			continue;
2091
2092		/*
2093		 * We can potentially drop this_rq's lock in
2094		 * double_lock_balance, and another CPU could
2095		 * alter this_rq
2096		 */
2097		double_lock_balance(this_rq, src_rq);
2098
2099		/*
2100		 * We can pull only a task, which is pushable
2101		 * on its rq, and no others.
2102		 */
2103		p = pick_highest_pushable_task(src_rq, this_cpu);
2104
2105		/*
2106		 * Do we have an RT task that preempts
2107		 * the to-be-scheduled task?
2108		 */
2109		if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
2110			WARN_ON(p == src_rq->curr);
2111			WARN_ON(!task_on_rq_queued(p));
2112
2113			/*
2114			 * There's a chance that p is higher in priority
2115			 * than what's currently running on its CPU.
2116			 * This is just that p is wakeing up and hasn't
2117			 * had a chance to schedule. We only pull
2118			 * p if it is lower in priority than the
2119			 * current task on the run queue
2120			 */
2121			if (p->prio < src_rq->curr->prio)
2122				goto skip;
2123
2124			resched = true;
2125
2126			deactivate_task(src_rq, p, 0);
2127			set_task_cpu(p, this_cpu);
2128			activate_task(this_rq, p, 0);
2129			/*
2130			 * We continue with the search, just in
2131			 * case there's an even higher prio task
2132			 * in another runqueue. (low likelihood
2133			 * but possible)
2134			 */
2135		}
2136skip:
2137		double_unlock_balance(this_rq, src_rq);
2138	}
2139
2140	if (resched)
2141		resched_curr(this_rq);
2142}
2143
2144/*
2145 * If we are not running and we are not going to reschedule soon, we should
2146 * try to push tasks away now
2147 */
2148static void task_woken_rt(struct rq *rq, struct task_struct *p)
2149{
2150	if (!task_running(rq, p) &&
2151	    !test_tsk_need_resched(rq->curr) &&
2152	    p->nr_cpus_allowed > 1 &&
2153	    (dl_task(rq->curr) || rt_task(rq->curr)) &&
2154	    (rq->curr->nr_cpus_allowed < 2 ||
2155	     rq->curr->prio <= p->prio))
2156		push_rt_tasks(rq);
2157}
2158
2159/* Assumes rq->lock is held */
2160static void rq_online_rt(struct rq *rq)
2161{
2162	if (rq->rt.overloaded)
2163		rt_set_overload(rq);
2164
2165	__enable_runtime(rq);
2166
2167	cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
2168}
2169
2170/* Assumes rq->lock is held */
2171static void rq_offline_rt(struct rq *rq)
2172{
2173	if (rq->rt.overloaded)
2174		rt_clear_overload(rq);
2175
2176	__disable_runtime(rq);
2177
2178	cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
2179}
2180
2181/*
2182 * When switch from the rt queue, we bring ourselves to a position
2183 * that we might want to pull RT tasks from other runqueues.
2184 */
2185static void switched_from_rt(struct rq *rq, struct task_struct *p)
2186{
2187	/*
2188	 * If there are other RT tasks then we will reschedule
2189	 * and the scheduling of the other RT tasks will handle
2190	 * the balancing. But if we are the last RT task
2191	 * we may need to handle the pulling of RT tasks
2192	 * now.
2193	 */
2194	if (!task_on_rq_queued(p) || rq->rt.rt_nr_running)
2195		return;
2196
2197	rt_queue_pull_task(rq);
2198}
2199
2200void __init init_sched_rt_class(void)
2201{
2202	unsigned int i;
2203
2204	for_each_possible_cpu(i) {
2205		zalloc_cpumask_var_node(&per_cpu(local_cpu_mask, i),
2206					GFP_KERNEL, cpu_to_node(i));
2207	}
2208}
2209#endif /* CONFIG_SMP */
2210
2211/*
2212 * When switching a task to RT, we may overload the runqueue
2213 * with RT tasks. In this case we try to push them off to
2214 * other runqueues.
2215 */
2216static void switched_to_rt(struct rq *rq, struct task_struct *p)
2217{
2218	/*
2219	 * If we are already running, then there's nothing
2220	 * that needs to be done. But if we are not running
2221	 * we may need to preempt the current running task.
2222	 * If that current running task is also an RT task
2223	 * then see if we can move to another run queue.
2224	 */
2225	if (task_on_rq_queued(p) && rq->curr != p) {
2226#ifdef CONFIG_SMP
2227		if (p->nr_cpus_allowed > 1 && rq->rt.overloaded)
2228			rt_queue_push_tasks(rq);
2229#endif /* CONFIG_SMP */
2230		if (p->prio < rq->curr->prio && cpu_online(cpu_of(rq)))
2231			resched_curr(rq);
 
2232	}
2233}
2234
2235/*
2236 * Priority of the task has changed. This may cause
2237 * us to initiate a push or pull.
2238 */
2239static void
2240prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
2241{
2242	if (!task_on_rq_queued(p))
2243		return;
2244
2245	if (rq->curr == p) {
2246#ifdef CONFIG_SMP
2247		/*
2248		 * If our priority decreases while running, we
2249		 * may need to pull tasks to this runqueue.
2250		 */
2251		if (oldprio < p->prio)
2252			rt_queue_pull_task(rq);
2253
2254		/*
2255		 * If there's a higher priority task waiting to run
2256		 * then reschedule.
2257		 */
2258		if (p->prio > rq->rt.highest_prio.curr)
2259			resched_curr(rq);
2260#else
2261		/* For UP simply resched on drop of prio */
2262		if (oldprio < p->prio)
2263			resched_curr(rq);
2264#endif /* CONFIG_SMP */
2265	} else {
2266		/*
2267		 * This task is not running, but if it is
2268		 * greater than the current running task
2269		 * then reschedule.
2270		 */
2271		if (p->prio < rq->curr->prio)
2272			resched_curr(rq);
2273	}
2274}
2275
2276#ifdef CONFIG_POSIX_TIMERS
2277static void watchdog(struct rq *rq, struct task_struct *p)
2278{
2279	unsigned long soft, hard;
2280
2281	/* max may change after cur was read, this will be fixed next tick */
2282	soft = task_rlimit(p, RLIMIT_RTTIME);
2283	hard = task_rlimit_max(p, RLIMIT_RTTIME);
2284
2285	if (soft != RLIM_INFINITY) {
2286		unsigned long next;
2287
2288		if (p->rt.watchdog_stamp != jiffies) {
2289			p->rt.timeout++;
2290			p->rt.watchdog_stamp = jiffies;
2291		}
2292
2293		next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
2294		if (p->rt.timeout > next) {
2295			posix_cputimers_rt_watchdog(&p->posix_cputimers,
2296						    p->se.sum_exec_runtime);
2297		}
2298	}
2299}
2300#else
2301static inline void watchdog(struct rq *rq, struct task_struct *p) { }
2302#endif
2303
2304/*
2305 * scheduler tick hitting a task of our scheduling class.
2306 *
2307 * NOTE: This function can be called remotely by the tick offload that
2308 * goes along full dynticks. Therefore no local assumption can be made
2309 * and everything must be accessed through the @rq and @curr passed in
2310 * parameters.
2311 */
2312static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
2313{
2314	struct sched_rt_entity *rt_se = &p->rt;
2315
2316	update_curr_rt(rq);
2317	update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 1);
2318
2319	watchdog(rq, p);
2320
2321	/*
2322	 * RR tasks need a special form of timeslice management.
2323	 * FIFO tasks have no timeslices.
2324	 */
2325	if (p->policy != SCHED_RR)
2326		return;
2327
2328	if (--p->rt.time_slice)
2329		return;
2330
2331	p->rt.time_slice = sched_rr_timeslice;
2332
2333	/*
2334	 * Requeue to the end of queue if we (and all of our ancestors) are not
2335	 * the only element on the queue
2336	 */
2337	for_each_sched_rt_entity(rt_se) {
2338		if (rt_se->run_list.prev != rt_se->run_list.next) {
2339			requeue_task_rt(rq, p, 0);
2340			resched_curr(rq);
2341			return;
2342		}
2343	}
2344}
2345
 
 
 
 
 
 
 
 
 
 
2346static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
2347{
2348	/*
2349	 * Time slice is 0 for SCHED_FIFO tasks
2350	 */
2351	if (task->policy == SCHED_RR)
2352		return sched_rr_timeslice;
2353	else
2354		return 0;
2355}
2356
2357const struct sched_class rt_sched_class = {
2358	.next			= &fair_sched_class,
2359	.enqueue_task		= enqueue_task_rt,
2360	.dequeue_task		= dequeue_task_rt,
2361	.yield_task		= yield_task_rt,
2362
2363	.check_preempt_curr	= check_preempt_curr_rt,
2364
2365	.pick_next_task		= pick_next_task_rt,
2366	.put_prev_task		= put_prev_task_rt,
2367	.set_next_task          = set_next_task_rt,
2368
2369#ifdef CONFIG_SMP
2370	.balance		= balance_rt,
2371	.select_task_rq		= select_task_rq_rt,
 
2372	.set_cpus_allowed       = set_cpus_allowed_common,
2373	.rq_online              = rq_online_rt,
2374	.rq_offline             = rq_offline_rt,
2375	.task_woken		= task_woken_rt,
2376	.switched_from		= switched_from_rt,
2377#endif
2378
 
2379	.task_tick		= task_tick_rt,
2380
2381	.get_rr_interval	= get_rr_interval_rt,
2382
2383	.prio_changed		= prio_changed_rt,
2384	.switched_to		= switched_to_rt,
2385
2386	.update_curr		= update_curr_rt,
2387
2388#ifdef CONFIG_UCLAMP_TASK
2389	.uclamp_enabled		= 1,
2390#endif
2391};
2392
2393#ifdef CONFIG_RT_GROUP_SCHED
2394/*
2395 * Ensure that the real time constraints are schedulable.
2396 */
2397static DEFINE_MUTEX(rt_constraints_mutex);
2398
2399/* Must be called with tasklist_lock held */
2400static inline int tg_has_rt_tasks(struct task_group *tg)
2401{
2402	struct task_struct *g, *p;
2403
2404	/*
2405	 * Autogroups do not have RT tasks; see autogroup_create().
2406	 */
2407	if (task_group_is_autogroup(tg))
2408		return 0;
2409
2410	for_each_process_thread(g, p) {
2411		if (rt_task(p) && task_group(p) == tg)
2412			return 1;
2413	}
2414
2415	return 0;
2416}
2417
2418struct rt_schedulable_data {
2419	struct task_group *tg;
2420	u64 rt_period;
2421	u64 rt_runtime;
2422};
2423
2424static int tg_rt_schedulable(struct task_group *tg, void *data)
2425{
2426	struct rt_schedulable_data *d = data;
2427	struct task_group *child;
2428	unsigned long total, sum = 0;
2429	u64 period, runtime;
2430
2431	period = ktime_to_ns(tg->rt_bandwidth.rt_period);
2432	runtime = tg->rt_bandwidth.rt_runtime;
2433
2434	if (tg == d->tg) {
2435		period = d->rt_period;
2436		runtime = d->rt_runtime;
2437	}
2438
2439	/*
2440	 * Cannot have more runtime than the period.
2441	 */
2442	if (runtime > period && runtime != RUNTIME_INF)
2443		return -EINVAL;
2444
2445	/*
2446	 * Ensure we don't starve existing RT tasks.
2447	 */
2448	if (rt_bandwidth_enabled() && !runtime && tg_has_rt_tasks(tg))
2449		return -EBUSY;
2450
2451	total = to_ratio(period, runtime);
2452
2453	/*
2454	 * Nobody can have more than the global setting allows.
2455	 */
2456	if (total > to_ratio(global_rt_period(), global_rt_runtime()))
2457		return -EINVAL;
2458
2459	/*
2460	 * The sum of our children's runtime should not exceed our own.
2461	 */
2462	list_for_each_entry_rcu(child, &tg->children, siblings) {
2463		period = ktime_to_ns(child->rt_bandwidth.rt_period);
2464		runtime = child->rt_bandwidth.rt_runtime;
2465
2466		if (child == d->tg) {
2467			period = d->rt_period;
2468			runtime = d->rt_runtime;
2469		}
2470
2471		sum += to_ratio(period, runtime);
2472	}
2473
2474	if (sum > total)
2475		return -EINVAL;
2476
2477	return 0;
2478}
2479
2480static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
2481{
2482	int ret;
2483
2484	struct rt_schedulable_data data = {
2485		.tg = tg,
2486		.rt_period = period,
2487		.rt_runtime = runtime,
2488	};
2489
2490	rcu_read_lock();
2491	ret = walk_tg_tree(tg_rt_schedulable, tg_nop, &data);
2492	rcu_read_unlock();
2493
2494	return ret;
2495}
2496
2497static int tg_set_rt_bandwidth(struct task_group *tg,
2498		u64 rt_period, u64 rt_runtime)
2499{
2500	int i, err = 0;
2501
2502	/*
2503	 * Disallowing the root group RT runtime is BAD, it would disallow the
2504	 * kernel creating (and or operating) RT threads.
2505	 */
2506	if (tg == &root_task_group && rt_runtime == 0)
2507		return -EINVAL;
2508
2509	/* No period doesn't make any sense. */
2510	if (rt_period == 0)
2511		return -EINVAL;
2512
2513	mutex_lock(&rt_constraints_mutex);
2514	read_lock(&tasklist_lock);
2515	err = __rt_schedulable(tg, rt_period, rt_runtime);
2516	if (err)
2517		goto unlock;
2518
2519	raw_spin_lock_irq(&tg->rt_bandwidth.rt_runtime_lock);
2520	tg->rt_bandwidth.rt_period = ns_to_ktime(rt_period);
2521	tg->rt_bandwidth.rt_runtime = rt_runtime;
2522
2523	for_each_possible_cpu(i) {
2524		struct rt_rq *rt_rq = tg->rt_rq[i];
2525
2526		raw_spin_lock(&rt_rq->rt_runtime_lock);
2527		rt_rq->rt_runtime = rt_runtime;
2528		raw_spin_unlock(&rt_rq->rt_runtime_lock);
2529	}
2530	raw_spin_unlock_irq(&tg->rt_bandwidth.rt_runtime_lock);
2531unlock:
2532	read_unlock(&tasklist_lock);
2533	mutex_unlock(&rt_constraints_mutex);
2534
2535	return err;
2536}
2537
2538int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)
2539{
2540	u64 rt_runtime, rt_period;
2541
2542	rt_period = ktime_to_ns(tg->rt_bandwidth.rt_period);
2543	rt_runtime = (u64)rt_runtime_us * NSEC_PER_USEC;
2544	if (rt_runtime_us < 0)
2545		rt_runtime = RUNTIME_INF;
2546	else if ((u64)rt_runtime_us > U64_MAX / NSEC_PER_USEC)
2547		return -EINVAL;
2548
2549	return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
2550}
2551
2552long sched_group_rt_runtime(struct task_group *tg)
2553{
2554	u64 rt_runtime_us;
2555
2556	if (tg->rt_bandwidth.rt_runtime == RUNTIME_INF)
2557		return -1;
2558
2559	rt_runtime_us = tg->rt_bandwidth.rt_runtime;
2560	do_div(rt_runtime_us, NSEC_PER_USEC);
2561	return rt_runtime_us;
2562}
2563
2564int sched_group_set_rt_period(struct task_group *tg, u64 rt_period_us)
2565{
2566	u64 rt_runtime, rt_period;
2567
2568	if (rt_period_us > U64_MAX / NSEC_PER_USEC)
2569		return -EINVAL;
2570
2571	rt_period = rt_period_us * NSEC_PER_USEC;
2572	rt_runtime = tg->rt_bandwidth.rt_runtime;
2573
2574	return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
2575}
2576
2577long sched_group_rt_period(struct task_group *tg)
2578{
2579	u64 rt_period_us;
2580
2581	rt_period_us = ktime_to_ns(tg->rt_bandwidth.rt_period);
2582	do_div(rt_period_us, NSEC_PER_USEC);
2583	return rt_period_us;
2584}
2585
2586static int sched_rt_global_constraints(void)
2587{
2588	int ret = 0;
2589
2590	mutex_lock(&rt_constraints_mutex);
2591	read_lock(&tasklist_lock);
2592	ret = __rt_schedulable(NULL, 0, 0);
2593	read_unlock(&tasklist_lock);
2594	mutex_unlock(&rt_constraints_mutex);
2595
2596	return ret;
2597}
2598
2599int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
2600{
2601	/* Don't accept realtime tasks when there is no way for them to run */
2602	if (rt_task(tsk) && tg->rt_bandwidth.rt_runtime == 0)
2603		return 0;
2604
2605	return 1;
2606}
2607
2608#else /* !CONFIG_RT_GROUP_SCHED */
2609static int sched_rt_global_constraints(void)
2610{
2611	unsigned long flags;
2612	int i;
2613
2614	raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
2615	for_each_possible_cpu(i) {
2616		struct rt_rq *rt_rq = &cpu_rq(i)->rt;
2617
2618		raw_spin_lock(&rt_rq->rt_runtime_lock);
2619		rt_rq->rt_runtime = global_rt_runtime();
2620		raw_spin_unlock(&rt_rq->rt_runtime_lock);
2621	}
2622	raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
2623
2624	return 0;
2625}
2626#endif /* CONFIG_RT_GROUP_SCHED */
2627
2628static int sched_rt_global_validate(void)
2629{
2630	if (sysctl_sched_rt_period <= 0)
2631		return -EINVAL;
2632
2633	if ((sysctl_sched_rt_runtime != RUNTIME_INF) &&
2634		(sysctl_sched_rt_runtime > sysctl_sched_rt_period))
2635		return -EINVAL;
2636
2637	return 0;
2638}
2639
2640static void sched_rt_do_global(void)
2641{
2642	def_rt_bandwidth.rt_runtime = global_rt_runtime();
2643	def_rt_bandwidth.rt_period = ns_to_ktime(global_rt_period());
2644}
2645
2646int sched_rt_handler(struct ctl_table *table, int write,
2647		void __user *buffer, size_t *lenp,
2648		loff_t *ppos)
2649{
2650	int old_period, old_runtime;
2651	static DEFINE_MUTEX(mutex);
2652	int ret;
2653
2654	mutex_lock(&mutex);
2655	old_period = sysctl_sched_rt_period;
2656	old_runtime = sysctl_sched_rt_runtime;
2657
2658	ret = proc_dointvec(table, write, buffer, lenp, ppos);
2659
2660	if (!ret && write) {
2661		ret = sched_rt_global_validate();
2662		if (ret)
2663			goto undo;
2664
2665		ret = sched_dl_global_validate();
2666		if (ret)
2667			goto undo;
2668
2669		ret = sched_rt_global_constraints();
2670		if (ret)
2671			goto undo;
2672
2673		sched_rt_do_global();
2674		sched_dl_do_global();
2675	}
2676	if (0) {
2677undo:
2678		sysctl_sched_rt_period = old_period;
2679		sysctl_sched_rt_runtime = old_runtime;
2680	}
2681	mutex_unlock(&mutex);
2682
2683	return ret;
2684}
2685
2686int sched_rr_handler(struct ctl_table *table, int write,
2687		void __user *buffer, size_t *lenp,
2688		loff_t *ppos)
2689{
2690	int ret;
2691	static DEFINE_MUTEX(mutex);
2692
2693	mutex_lock(&mutex);
2694	ret = proc_dointvec(table, write, buffer, lenp, ppos);
2695	/*
2696	 * Make sure that internally we keep jiffies.
2697	 * Also, writing zero resets the timeslice to default:
2698	 */
2699	if (!ret && write) {
2700		sched_rr_timeslice =
2701			sysctl_sched_rr_timeslice <= 0 ? RR_TIMESLICE :
2702			msecs_to_jiffies(sysctl_sched_rr_timeslice);
2703	}
2704	mutex_unlock(&mutex);
2705
2706	return ret;
2707}
2708
2709#ifdef CONFIG_SCHED_DEBUG
 
 
2710void print_rt_stats(struct seq_file *m, int cpu)
2711{
2712	rt_rq_iter_t iter;
2713	struct rt_rq *rt_rq;
2714
2715	rcu_read_lock();
2716	for_each_rt_rq(rt_rq, iter, cpu_rq(cpu))
2717		print_rt_rq(m, cpu, rt_rq);
2718	rcu_read_unlock();
2719}
2720#endif /* CONFIG_SCHED_DEBUG */