rt.c 48.2 KB
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/*
 * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
 * policies)
 */

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#include "sched.h"

#include <linux/slab.h>

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int sched_rr_timeslice = RR_TIMESLICE;

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static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);

struct rt_bandwidth def_rt_bandwidth;

static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer)
{
	struct rt_bandwidth *rt_b =
		container_of(timer, struct rt_bandwidth, rt_period_timer);
	ktime_t now;
	int overrun;
	int idle = 0;

	for (;;) {
		now = hrtimer_cb_get_time(timer);
		overrun = hrtimer_forward(timer, now, rt_b->rt_period);

		if (!overrun)
			break;

		idle = do_sched_rt_period_timer(rt_b, overrun);
	}

	return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
}

void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime)
{
	rt_b->rt_period = ns_to_ktime(period);
	rt_b->rt_runtime = runtime;

	raw_spin_lock_init(&rt_b->rt_runtime_lock);

	hrtimer_init(&rt_b->rt_period_timer,
			CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	rt_b->rt_period_timer.function = sched_rt_period_timer;
}

static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
{
	if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
		return;

	if (hrtimer_active(&rt_b->rt_period_timer))
		return;

	raw_spin_lock(&rt_b->rt_runtime_lock);
	start_bandwidth_timer(&rt_b->rt_period_timer, rt_b->rt_period);
	raw_spin_unlock(&rt_b->rt_runtime_lock);
}

void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq)
{
	struct rt_prio_array *array;
	int i;

	array = &rt_rq->active;
	for (i = 0; i < MAX_RT_PRIO; i++) {
		INIT_LIST_HEAD(array->queue + i);
		__clear_bit(i, array->bitmap);
	}
	/* delimiter for bitsearch: */
	__set_bit(MAX_RT_PRIO, array->bitmap);

#if defined CONFIG_SMP
	rt_rq->highest_prio.curr = MAX_RT_PRIO;
	rt_rq->highest_prio.next = MAX_RT_PRIO;
	rt_rq->rt_nr_migratory = 0;
	rt_rq->overloaded = 0;
	plist_head_init(&rt_rq->pushable_tasks);
#endif
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	/* We start is dequeued state, because no RT tasks are queued */
	rt_rq->rt_queued = 0;
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	rt_rq->rt_time = 0;
	rt_rq->rt_throttled = 0;
	rt_rq->rt_runtime = 0;
	raw_spin_lock_init(&rt_rq->rt_runtime_lock);
}

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#ifdef CONFIG_RT_GROUP_SCHED
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static void destroy_rt_bandwidth(struct rt_bandwidth *rt_b)
{
	hrtimer_cancel(&rt_b->rt_period_timer);
}
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#define rt_entity_is_task(rt_se) (!(rt_se)->my_q)

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static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
{
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#ifdef CONFIG_SCHED_DEBUG
	WARN_ON_ONCE(!rt_entity_is_task(rt_se));
#endif
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	return container_of(rt_se, struct task_struct, rt);
}

static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
{
	return rt_rq->rq;
}

static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
{
	return rt_se->rt_rq;
}

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static inline struct rq *rq_of_rt_se(struct sched_rt_entity *rt_se)
{
	struct rt_rq *rt_rq = rt_se->rt_rq;

	return rt_rq->rq;
}

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void free_rt_sched_group(struct task_group *tg)
{
	int i;

	if (tg->rt_se)
		destroy_rt_bandwidth(&tg->rt_bandwidth);

	for_each_possible_cpu(i) {
		if (tg->rt_rq)
			kfree(tg->rt_rq[i]);
		if (tg->rt_se)
			kfree(tg->rt_se[i]);
	}

	kfree(tg->rt_rq);
	kfree(tg->rt_se);
}

void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
		struct sched_rt_entity *rt_se, int cpu,
		struct sched_rt_entity *parent)
{
	struct rq *rq = cpu_rq(cpu);

	rt_rq->highest_prio.curr = MAX_RT_PRIO;
	rt_rq->rt_nr_boosted = 0;
	rt_rq->rq = rq;
	rt_rq->tg = tg;

	tg->rt_rq[cpu] = rt_rq;
	tg->rt_se[cpu] = rt_se;

	if (!rt_se)
		return;

	if (!parent)
		rt_se->rt_rq = &rq->rt;
	else
		rt_se->rt_rq = parent->my_q;

	rt_se->my_q = rt_rq;
	rt_se->parent = parent;
	INIT_LIST_HEAD(&rt_se->run_list);
}

int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
{
	struct rt_rq *rt_rq;
	struct sched_rt_entity *rt_se;
	int i;

	tg->rt_rq = kzalloc(sizeof(rt_rq) * nr_cpu_ids, GFP_KERNEL);
	if (!tg->rt_rq)
		goto err;
	tg->rt_se = kzalloc(sizeof(rt_se) * nr_cpu_ids, GFP_KERNEL);
	if (!tg->rt_se)
		goto err;

	init_rt_bandwidth(&tg->rt_bandwidth,
			ktime_to_ns(def_rt_bandwidth.rt_period), 0);

	for_each_possible_cpu(i) {
		rt_rq = kzalloc_node(sizeof(struct rt_rq),
				     GFP_KERNEL, cpu_to_node(i));
		if (!rt_rq)
			goto err;

		rt_se = kzalloc_node(sizeof(struct sched_rt_entity),
				     GFP_KERNEL, cpu_to_node(i));
		if (!rt_se)
			goto err_free_rq;

		init_rt_rq(rt_rq, cpu_rq(i));
		rt_rq->rt_runtime = tg->rt_bandwidth.rt_runtime;
		init_tg_rt_entry(tg, rt_rq, rt_se, i, parent->rt_se[i]);
	}

	return 1;

err_free_rq:
	kfree(rt_rq);
err:
	return 0;
}

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#else /* CONFIG_RT_GROUP_SCHED */

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#define rt_entity_is_task(rt_se) (1)

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static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
{
	return container_of(rt_se, struct task_struct, rt);
}

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static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
{
	return container_of(rt_rq, struct rq, rt);
}

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static inline struct rq *rq_of_rt_se(struct sched_rt_entity *rt_se)
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{
	struct task_struct *p = rt_task_of(rt_se);
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	return task_rq(p);
}

static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
{
	struct rq *rq = rq_of_rt_se(rt_se);
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	return &rq->rt;
}

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void free_rt_sched_group(struct task_group *tg) { }

int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
{
	return 1;
}
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#endif /* CONFIG_RT_GROUP_SCHED */

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#ifdef CONFIG_SMP
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static int pull_rt_task(struct rq *this_rq);

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static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
{
	/* Try to pull RT tasks here if we lower this rq's prio */
	return rq->rt.highest_prio.curr > prev->prio;
}

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static inline int rt_overloaded(struct rq *rq)
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{
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	return atomic_read(&rq->rd->rto_count);
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}
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static inline void rt_set_overload(struct rq *rq)
{
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	if (!rq->online)
		return;

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	cpumask_set_cpu(rq->cpu, rq->rd->rto_mask);
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	/*
	 * Make sure the mask is visible before we set
	 * the overload count. That is checked to determine
	 * if we should look at the mask. It would be a shame
	 * if we looked at the mask, but the mask was not
	 * updated yet.
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	 *
	 * Matched by the barrier in pull_rt_task().
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	 */
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	smp_wmb();
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	atomic_inc(&rq->rd->rto_count);
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}
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static inline void rt_clear_overload(struct rq *rq)
{
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	if (!rq->online)
		return;

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	/* the order here really doesn't matter */
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	atomic_dec(&rq->rd->rto_count);
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	cpumask_clear_cpu(rq->cpu, rq->rd->rto_mask);
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}
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static void update_rt_migration(struct rt_rq *rt_rq)
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{
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	if (rt_rq->rt_nr_migratory && rt_rq->rt_nr_total > 1) {
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		if (!rt_rq->overloaded) {
			rt_set_overload(rq_of_rt_rq(rt_rq));
			rt_rq->overloaded = 1;
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		}
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	} else if (rt_rq->overloaded) {
		rt_clear_overload(rq_of_rt_rq(rt_rq));
		rt_rq->overloaded = 0;
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	}
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}
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static void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
{
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	struct task_struct *p;

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	if (!rt_entity_is_task(rt_se))
		return;

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	p = rt_task_of(rt_se);
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	rt_rq = &rq_of_rt_rq(rt_rq)->rt;

	rt_rq->rt_nr_total++;
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	if (p->nr_cpus_allowed > 1)
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		rt_rq->rt_nr_migratory++;

	update_rt_migration(rt_rq);
}

static void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
{
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	struct task_struct *p;

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	if (!rt_entity_is_task(rt_se))
		return;

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	p = rt_task_of(rt_se);
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	rt_rq = &rq_of_rt_rq(rt_rq)->rt;

	rt_rq->rt_nr_total--;
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	if (p->nr_cpus_allowed > 1)
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		rt_rq->rt_nr_migratory--;

	update_rt_migration(rt_rq);
}

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static inline int has_pushable_tasks(struct rq *rq)
{
	return !plist_head_empty(&rq->rt.pushable_tasks);
}

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static inline void set_post_schedule(struct rq *rq)
{
	/*
	 * We detect this state here so that we can avoid taking the RQ
	 * lock again later if there is no need to push
	 */
	rq->post_schedule = has_pushable_tasks(rq);
}

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static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
{
	plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
	plist_node_init(&p->pushable_tasks, p->prio);
	plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks);
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	/* Update the highest prio pushable task */
	if (p->prio < rq->rt.highest_prio.next)
		rq->rt.highest_prio.next = p->prio;
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}

static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
{
	plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);

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	/* Update the new highest prio pushable task */
	if (has_pushable_tasks(rq)) {
		p = plist_first_entry(&rq->rt.pushable_tasks,
				      struct task_struct, pushable_tasks);
		rq->rt.highest_prio.next = p->prio;
	} else
		rq->rt.highest_prio.next = MAX_RT_PRIO;
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}

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#else

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static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
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{
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}

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static inline void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
{
}

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static inline
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void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
{
}

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static inline
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void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
{
}
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static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
{
	return false;
}

static inline int pull_rt_task(struct rq *this_rq)
{
	return 0;
}

static inline void set_post_schedule(struct rq *rq)
{
}
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#endif /* CONFIG_SMP */

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static void enqueue_top_rt_rq(struct rt_rq *rt_rq);
static void dequeue_top_rt_rq(struct rt_rq *rt_rq);

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static inline int on_rt_rq(struct sched_rt_entity *rt_se)
{
	return !list_empty(&rt_se->run_list);
}

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#ifdef CONFIG_RT_GROUP_SCHED
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static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
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{
	if (!rt_rq->tg)
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		return RUNTIME_INF;
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	return rt_rq->rt_runtime;
}

static inline u64 sched_rt_period(struct rt_rq *rt_rq)
{
	return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
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}

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typedef struct task_group *rt_rq_iter_t;

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static inline struct task_group *next_task_group(struct task_group *tg)
{
	do {
		tg = list_entry_rcu(tg->list.next,
			typeof(struct task_group), list);
	} while (&tg->list != &task_groups && task_group_is_autogroup(tg));

	if (&tg->list == &task_groups)
		tg = NULL;

	return tg;
}

#define for_each_rt_rq(rt_rq, iter, rq)					\
	for (iter = container_of(&task_groups, typeof(*iter), list);	\
		(iter = next_task_group(iter)) &&			\
		(rt_rq = iter->rt_rq[cpu_of(rq)]);)
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#define for_each_sched_rt_entity(rt_se) \
	for (; rt_se; rt_se = rt_se->parent)

static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
{
	return rt_se->my_q;
}

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static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head);
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static void dequeue_rt_entity(struct sched_rt_entity *rt_se);

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static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
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{
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	struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
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	struct rq *rq = rq_of_rt_rq(rt_rq);
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	struct sched_rt_entity *rt_se;

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	int cpu = cpu_of(rq);
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	rt_se = rt_rq->tg->rt_se[cpu];
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	if (rt_rq->rt_nr_running) {
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		if (!rt_se)
			enqueue_top_rt_rq(rt_rq);
		else if (!on_rt_rq(rt_se))
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			enqueue_rt_entity(rt_se, false);
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		if (rt_rq->highest_prio.curr < curr->prio)
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			resched_curr(rq);
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	}
}

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static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
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{
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	struct sched_rt_entity *rt_se;
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	int cpu = cpu_of(rq_of_rt_rq(rt_rq));
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	rt_se = rt_rq->tg->rt_se[cpu];
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	if (!rt_se)
		dequeue_top_rt_rq(rt_rq);
	else if (on_rt_rq(rt_se))
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		dequeue_rt_entity(rt_se);
}

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static inline int rt_rq_throttled(struct rt_rq *rt_rq)
{
	return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
}

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static int rt_se_boosted(struct sched_rt_entity *rt_se)
{
	struct rt_rq *rt_rq = group_rt_rq(rt_se);
	struct task_struct *p;

	if (rt_rq)
		return !!rt_rq->rt_nr_boosted;

	p = rt_task_of(rt_se);
	return p->prio != p->normal_prio;
}

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#ifdef CONFIG_SMP
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static inline const struct cpumask *sched_rt_period_mask(void)
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{
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	return this_rq()->rd->span;
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}
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#else
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static inline const struct cpumask *sched_rt_period_mask(void)
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{
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	return cpu_online_mask;
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}
#endif
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static inline
struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
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{
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	return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
}
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static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
{
	return &rt_rq->tg->rt_bandwidth;
}

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#else /* !CONFIG_RT_GROUP_SCHED */
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static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
{
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	return rt_rq->rt_runtime;
}

static inline u64 sched_rt_period(struct rt_rq *rt_rq)
{
	return ktime_to_ns(def_rt_bandwidth.rt_period);
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}

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typedef struct rt_rq *rt_rq_iter_t;

#define for_each_rt_rq(rt_rq, iter, rq) \
	for ((void) iter, rt_rq = &rq->rt; rt_rq; rt_rq = NULL)

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#define for_each_sched_rt_entity(rt_se) \
	for (; rt_se; rt_se = NULL)

static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
{
	return NULL;
}

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static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
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{
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	struct rq *rq = rq_of_rt_rq(rt_rq);

	if (!rt_rq->rt_nr_running)
		return;

	enqueue_top_rt_rq(rt_rq);
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	resched_curr(rq);
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}

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static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
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{
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	dequeue_top_rt_rq(rt_rq);
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}

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static inline int rt_rq_throttled(struct rt_rq *rt_rq)
{
	return rt_rq->rt_throttled;
}

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static inline const struct cpumask *sched_rt_period_mask(void)
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{
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	return cpu_online_mask;
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}

static inline
struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
{
	return &cpu_rq(cpu)->rt;
}

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static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
{
	return &def_rt_bandwidth;
}

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#endif /* CONFIG_RT_GROUP_SCHED */
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bool sched_rt_bandwidth_account(struct rt_rq *rt_rq)
{
	struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);

	return (hrtimer_active(&rt_b->rt_period_timer) ||
		rt_rq->rt_time < rt_b->rt_runtime);
}

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#ifdef CONFIG_SMP
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/*
 * We ran out of runtime, see if we can borrow some from our neighbours.
 */
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static int do_balance_runtime(struct rt_rq *rt_rq)
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{
	struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
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	struct root_domain *rd = rq_of_rt_rq(rt_rq)->rd;
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	int i, weight, more = 0;
	u64 rt_period;

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	weight = cpumask_weight(rd->span);
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	raw_spin_lock(&rt_b->rt_runtime_lock);
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623
	rt_period = ktime_to_ns(rt_b->rt_period);
624
	for_each_cpu(i, rd->span) {
P
Peter Zijlstra 已提交
625 626 627 628 629 630
		struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
		s64 diff;

		if (iter == rt_rq)
			continue;

631
		raw_spin_lock(&iter->rt_runtime_lock);
632 633 634 635 636
		/*
		 * Either all rqs have inf runtime and there's nothing to steal
		 * or __disable_runtime() below sets a specific rq to inf to
		 * indicate its been disabled and disalow stealing.
		 */
P
Peter Zijlstra 已提交
637 638 639
		if (iter->rt_runtime == RUNTIME_INF)
			goto next;

640 641 642 643
		/*
		 * From runqueues with spare time, take 1/n part of their
		 * spare time, but no more than our period.
		 */
P
Peter Zijlstra 已提交
644 645
		diff = iter->rt_runtime - iter->rt_time;
		if (diff > 0) {
646
			diff = div_u64((u64)diff, weight);
P
Peter Zijlstra 已提交
647 648 649 650 651 652
			if (rt_rq->rt_runtime + diff > rt_period)
				diff = rt_period - rt_rq->rt_runtime;
			iter->rt_runtime -= diff;
			rt_rq->rt_runtime += diff;
			more = 1;
			if (rt_rq->rt_runtime == rt_period) {
653
				raw_spin_unlock(&iter->rt_runtime_lock);
P
Peter Zijlstra 已提交
654 655 656
				break;
			}
		}
P
Peter Zijlstra 已提交
657
next:
658
		raw_spin_unlock(&iter->rt_runtime_lock);
P
Peter Zijlstra 已提交
659
	}
660
	raw_spin_unlock(&rt_b->rt_runtime_lock);
P
Peter Zijlstra 已提交
661 662 663

	return more;
}
P
Peter Zijlstra 已提交
664

665 666 667
/*
 * Ensure this RQ takes back all the runtime it lend to its neighbours.
 */
P
Peter Zijlstra 已提交
668 669 670
static void __disable_runtime(struct rq *rq)
{
	struct root_domain *rd = rq->rd;
C
Cheng Xu 已提交
671
	rt_rq_iter_t iter;
P
Peter Zijlstra 已提交
672 673 674 675 676
	struct rt_rq *rt_rq;

	if (unlikely(!scheduler_running))
		return;

C
Cheng Xu 已提交
677
	for_each_rt_rq(rt_rq, iter, rq) {
P
Peter Zijlstra 已提交
678 679 680 681
		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
		s64 want;
		int i;

682 683
		raw_spin_lock(&rt_b->rt_runtime_lock);
		raw_spin_lock(&rt_rq->rt_runtime_lock);
684 685 686 687 688
		/*
		 * Either we're all inf and nobody needs to borrow, or we're
		 * already disabled and thus have nothing to do, or we have
		 * exactly the right amount of runtime to take out.
		 */
P
Peter Zijlstra 已提交
689 690 691
		if (rt_rq->rt_runtime == RUNTIME_INF ||
				rt_rq->rt_runtime == rt_b->rt_runtime)
			goto balanced;
692
		raw_spin_unlock(&rt_rq->rt_runtime_lock);
P
Peter Zijlstra 已提交
693

694 695 696 697 698
		/*
		 * Calculate the difference between what we started out with
		 * and what we current have, that's the amount of runtime
		 * we lend and now have to reclaim.
		 */
P
Peter Zijlstra 已提交
699 700
		want = rt_b->rt_runtime - rt_rq->rt_runtime;

701 702 703
		/*
		 * Greedy reclaim, take back as much as we can.
		 */
704
		for_each_cpu(i, rd->span) {
P
Peter Zijlstra 已提交
705 706 707
			struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
			s64 diff;

708 709 710
			/*
			 * Can't reclaim from ourselves or disabled runqueues.
			 */
711
			if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
P
Peter Zijlstra 已提交
712 713
				continue;

714
			raw_spin_lock(&iter->rt_runtime_lock);
P
Peter Zijlstra 已提交
715 716 717 718 719 720 721 722
			if (want > 0) {
				diff = min_t(s64, iter->rt_runtime, want);
				iter->rt_runtime -= diff;
				want -= diff;
			} else {
				iter->rt_runtime -= want;
				want -= want;
			}
723
			raw_spin_unlock(&iter->rt_runtime_lock);
P
Peter Zijlstra 已提交
724 725 726 727 728

			if (!want)
				break;
		}

729
		raw_spin_lock(&rt_rq->rt_runtime_lock);
730 731 732 733
		/*
		 * We cannot be left wanting - that would mean some runtime
		 * leaked out of the system.
		 */
P
Peter Zijlstra 已提交
734 735
		BUG_ON(want);
balanced:
736 737 738 739
		/*
		 * Disable all the borrow logic by pretending we have inf
		 * runtime - in which case borrowing doesn't make sense.
		 */
P
Peter Zijlstra 已提交
740
		rt_rq->rt_runtime = RUNTIME_INF;
741
		rt_rq->rt_throttled = 0;
742 743
		raw_spin_unlock(&rt_rq->rt_runtime_lock);
		raw_spin_unlock(&rt_b->rt_runtime_lock);
744 745 746

		/* Make rt_rq available for pick_next_task() */
		sched_rt_rq_enqueue(rt_rq);
P
Peter Zijlstra 已提交
747 748 749 750 751
	}
}

static void __enable_runtime(struct rq *rq)
{
C
Cheng Xu 已提交
752
	rt_rq_iter_t iter;
P
Peter Zijlstra 已提交
753 754 755 756 757
	struct rt_rq *rt_rq;

	if (unlikely(!scheduler_running))
		return;

758 759 760
	/*
	 * Reset each runqueue's bandwidth settings
	 */
C
Cheng Xu 已提交
761
	for_each_rt_rq(rt_rq, iter, rq) {
P
Peter Zijlstra 已提交
762 763
		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);

764 765
		raw_spin_lock(&rt_b->rt_runtime_lock);
		raw_spin_lock(&rt_rq->rt_runtime_lock);
P
Peter Zijlstra 已提交
766 767
		rt_rq->rt_runtime = rt_b->rt_runtime;
		rt_rq->rt_time = 0;
768
		rt_rq->rt_throttled = 0;
769 770
		raw_spin_unlock(&rt_rq->rt_runtime_lock);
		raw_spin_unlock(&rt_b->rt_runtime_lock);
P
Peter Zijlstra 已提交
771 772 773
	}
}

774 775 776 777
static int balance_runtime(struct rt_rq *rt_rq)
{
	int more = 0;

778 779 780
	if (!sched_feat(RT_RUNTIME_SHARE))
		return more;

781
	if (rt_rq->rt_time > rt_rq->rt_runtime) {
782
		raw_spin_unlock(&rt_rq->rt_runtime_lock);
783
		more = do_balance_runtime(rt_rq);
784
		raw_spin_lock(&rt_rq->rt_runtime_lock);
785 786 787 788
	}

	return more;
}
789
#else /* !CONFIG_SMP */
790 791 792 793
static inline int balance_runtime(struct rt_rq *rt_rq)
{
	return 0;
}
794
#endif /* CONFIG_SMP */
P
Peter Zijlstra 已提交
795

796 797
static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
{
798
	int i, idle = 1, throttled = 0;
799
	const struct cpumask *span;
800 801

	span = sched_rt_period_mask();
802 803 804 805 806 807 808 809 810 811 812 813 814
#ifdef CONFIG_RT_GROUP_SCHED
	/*
	 * FIXME: isolated CPUs should really leave the root task group,
	 * whether they are isolcpus or were isolated via cpusets, lest
	 * the timer run on a CPU which does not service all runqueues,
	 * potentially leaving other CPUs indefinitely throttled.  If
	 * isolation is really required, the user will turn the throttle
	 * off to kill the perturbations it causes anyway.  Meanwhile,
	 * this maintains functionality for boot and/or troubleshooting.
	 */
	if (rt_b == &root_task_group.rt_bandwidth)
		span = cpu_online_mask;
#endif
815
	for_each_cpu(i, span) {
816 817 818 819
		int enqueue = 0;
		struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
		struct rq *rq = rq_of_rt_rq(rt_rq);

820
		raw_spin_lock(&rq->lock);
821 822 823
		if (rt_rq->rt_time) {
			u64 runtime;

824
			raw_spin_lock(&rt_rq->rt_runtime_lock);
825 826 827 828 829 830 831
			if (rt_rq->rt_throttled)
				balance_runtime(rt_rq);
			runtime = rt_rq->rt_runtime;
			rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
			if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
				rt_rq->rt_throttled = 0;
				enqueue = 1;
832 833 834 835 836 837 838

				/*
				 * Force a clock update if the CPU was idle,
				 * lest wakeup -> unthrottle time accumulate.
				 */
				if (rt_rq->rt_nr_running && rq->curr == rq->idle)
					rq->skip_clock_update = -1;
839 840 841
			}
			if (rt_rq->rt_time || rt_rq->rt_nr_running)
				idle = 0;
842
			raw_spin_unlock(&rt_rq->rt_runtime_lock);
843
		} else if (rt_rq->rt_nr_running) {
844
			idle = 0;
845 846 847
			if (!rt_rq_throttled(rt_rq))
				enqueue = 1;
		}
848 849
		if (rt_rq->rt_throttled)
			throttled = 1;
850 851 852

		if (enqueue)
			sched_rt_rq_enqueue(rt_rq);
853
		raw_spin_unlock(&rq->lock);
854 855
	}

856 857 858
	if (!throttled && (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF))
		return 1;

859 860
	return idle;
}
P
Peter Zijlstra 已提交
861

P
Peter Zijlstra 已提交
862 863
static inline int rt_se_prio(struct sched_rt_entity *rt_se)
{
864
#ifdef CONFIG_RT_GROUP_SCHED
P
Peter Zijlstra 已提交
865 866 867
	struct rt_rq *rt_rq = group_rt_rq(rt_se);

	if (rt_rq)
868
		return rt_rq->highest_prio.curr;
P
Peter Zijlstra 已提交
869 870 871 872 873
#endif

	return rt_task_of(rt_se)->prio;
}

P
Peter Zijlstra 已提交
874
static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
P
Peter Zijlstra 已提交
875
{
P
Peter Zijlstra 已提交
876
	u64 runtime = sched_rt_runtime(rt_rq);
P
Peter Zijlstra 已提交
877 878

	if (rt_rq->rt_throttled)
P
Peter Zijlstra 已提交
879
		return rt_rq_throttled(rt_rq);
P
Peter Zijlstra 已提交
880

881
	if (runtime >= sched_rt_period(rt_rq))
P
Peter Zijlstra 已提交
882 883
		return 0;

884 885 886 887
	balance_runtime(rt_rq);
	runtime = sched_rt_runtime(rt_rq);
	if (runtime == RUNTIME_INF)
		return 0;
P
Peter Zijlstra 已提交
888

P
Peter Zijlstra 已提交
889
	if (rt_rq->rt_time > runtime) {
890 891 892 893 894 895 896 897
		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);

		/*
		 * Don't actually throttle groups that have no runtime assigned
		 * but accrue some time due to boosting.
		 */
		if (likely(rt_b->rt_runtime)) {
			rt_rq->rt_throttled = 1;
J
John Stultz 已提交
898
			printk_deferred_once("sched: RT throttling activated\n");
899 900 901 902 903 904 905 906 907
		} else {
			/*
			 * In case we did anyway, make it go away,
			 * replenishment is a joke, since it will replenish us
			 * with exactly 0 ns.
			 */
			rt_rq->rt_time = 0;
		}

P
Peter Zijlstra 已提交
908
		if (rt_rq_throttled(rt_rq)) {
P
Peter Zijlstra 已提交
909
			sched_rt_rq_dequeue(rt_rq);
P
Peter Zijlstra 已提交
910 911
			return 1;
		}
P
Peter Zijlstra 已提交
912 913 914 915 916
	}

	return 0;
}

I
Ingo Molnar 已提交
917 918 919 920
/*
 * Update the current task's runtime statistics. Skip current tasks that
 * are not in our scheduling class.
 */
A
Alexey Dobriyan 已提交
921
static void update_curr_rt(struct rq *rq)
I
Ingo Molnar 已提交
922 923
{
	struct task_struct *curr = rq->curr;
P
Peter Zijlstra 已提交
924
	struct sched_rt_entity *rt_se = &curr->rt;
I
Ingo Molnar 已提交
925 926
	u64 delta_exec;

P
Peter Zijlstra 已提交
927
	if (curr->sched_class != &rt_sched_class)
I
Ingo Molnar 已提交
928 929
		return;

930
	delta_exec = rq_clock_task(rq) - curr->se.exec_start;
931 932
	if (unlikely((s64)delta_exec <= 0))
		return;
I
Ingo Molnar 已提交
933

934 935
	schedstat_set(curr->se.statistics.exec_max,
		      max(curr->se.statistics.exec_max, delta_exec));
I
Ingo Molnar 已提交
936 937

	curr->se.sum_exec_runtime += delta_exec;
938 939
	account_group_exec_runtime(curr, delta_exec);

940
	curr->se.exec_start = rq_clock_task(rq);
941
	cpuacct_charge(curr, delta_exec);
P
Peter Zijlstra 已提交
942

943 944
	sched_rt_avg_update(rq, delta_exec);

945 946 947
	if (!rt_bandwidth_enabled())
		return;

D
Dhaval Giani 已提交
948
	for_each_sched_rt_entity(rt_se) {
949
		struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
D
Dhaval Giani 已提交
950

951
		if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
952
			raw_spin_lock(&rt_rq->rt_runtime_lock);
953 954
			rt_rq->rt_time += delta_exec;
			if (sched_rt_runtime_exceeded(rt_rq))
955
				resched_curr(rq);
956
			raw_spin_unlock(&rt_rq->rt_runtime_lock);
957
		}
D
Dhaval Giani 已提交
958
	}
I
Ingo Molnar 已提交
959 960
}

961 962 963 964 965 966 967 968 969 970 971 972
static void
dequeue_top_rt_rq(struct rt_rq *rt_rq)
{
	struct rq *rq = rq_of_rt_rq(rt_rq);

	BUG_ON(&rq->rt != rt_rq);

	if (!rt_rq->rt_queued)
		return;

	BUG_ON(!rq->nr_running);

973
	sub_nr_running(rq, rt_rq->rt_nr_running);
974 975 976 977 978 979 980 981 982 983 984 985 986 987 988
	rt_rq->rt_queued = 0;
}

static void
enqueue_top_rt_rq(struct rt_rq *rt_rq)
{
	struct rq *rq = rq_of_rt_rq(rt_rq);

	BUG_ON(&rq->rt != rt_rq);

	if (rt_rq->rt_queued)
		return;
	if (rt_rq_throttled(rt_rq) || !rt_rq->rt_nr_running)
		return;

989
	add_nr_running(rq, rt_rq->rt_nr_running);
990 991 992
	rt_rq->rt_queued = 1;
}

993
#if defined CONFIG_SMP
994

995 996
static void
inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
997
{
G
Gregory Haskins 已提交
998
	struct rq *rq = rq_of_rt_rq(rt_rq);
999

1000 1001 1002 1003 1004 1005 1006
#ifdef CONFIG_RT_GROUP_SCHED
	/*
	 * Change rq's cpupri only if rt_rq is the top queue.
	 */
	if (&rq->rt != rt_rq)
		return;
#endif
1007 1008
	if (rq->online && prio < prev_prio)
		cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
1009
}
1010

1011 1012 1013 1014
static void
dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
{
	struct rq *rq = rq_of_rt_rq(rt_rq);
1015

1016 1017 1018 1019 1020 1021 1022
#ifdef CONFIG_RT_GROUP_SCHED
	/*
	 * Change rq's cpupri only if rt_rq is the top queue.
	 */
	if (&rq->rt != rt_rq)
		return;
#endif
1023 1024
	if (rq->online && rt_rq->highest_prio.curr != prev_prio)
		cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
1025 1026
}

1027 1028
#else /* CONFIG_SMP */

P
Peter Zijlstra 已提交
1029
static inline
1030 1031 1032 1033 1034
void inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
static inline
void dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}

#endif /* CONFIG_SMP */
1035

1036
#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052
static void
inc_rt_prio(struct rt_rq *rt_rq, int prio)
{
	int prev_prio = rt_rq->highest_prio.curr;

	if (prio < prev_prio)
		rt_rq->highest_prio.curr = prio;

	inc_rt_prio_smp(rt_rq, prio, prev_prio);
}

static void
dec_rt_prio(struct rt_rq *rt_rq, int prio)
{
	int prev_prio = rt_rq->highest_prio.curr;

P
Peter Zijlstra 已提交
1053
	if (rt_rq->rt_nr_running) {
1054

1055
		WARN_ON(prio < prev_prio);
1056

1057
		/*
1058 1059
		 * This may have been our highest task, and therefore
		 * we may have some recomputation to do
1060
		 */
1061
		if (prio == prev_prio) {
1062 1063 1064
			struct rt_prio_array *array = &rt_rq->active;

			rt_rq->highest_prio.curr =
1065
				sched_find_first_bit(array->bitmap);
1066 1067
		}

1068
	} else
1069
		rt_rq->highest_prio.curr = MAX_RT_PRIO;
1070

1071 1072
	dec_rt_prio_smp(rt_rq, prio, prev_prio);
}
1073

1074 1075 1076 1077 1078 1079
#else

static inline void inc_rt_prio(struct rt_rq *rt_rq, int prio) {}
static inline void dec_rt_prio(struct rt_rq *rt_rq, int prio) {}

#endif /* CONFIG_SMP || CONFIG_RT_GROUP_SCHED */
1080

1081
#ifdef CONFIG_RT_GROUP_SCHED
1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095

static void
inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
{
	if (rt_se_boosted(rt_se))
		rt_rq->rt_nr_boosted++;

	if (rt_rq->tg)
		start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
}

static void
dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
{
P
Peter Zijlstra 已提交
1096 1097 1098 1099
	if (rt_se_boosted(rt_se))
		rt_rq->rt_nr_boosted--;

	WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114
}

#else /* CONFIG_RT_GROUP_SCHED */

static void
inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
{
	start_rt_bandwidth(&def_rt_bandwidth);
}

static inline
void dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) {}

#endif /* CONFIG_RT_GROUP_SCHED */

1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125
static inline
unsigned int rt_se_nr_running(struct sched_rt_entity *rt_se)
{
	struct rt_rq *group_rq = group_rt_rq(rt_se);

	if (group_rq)
		return group_rq->rt_nr_running;
	else
		return 1;
}

1126 1127 1128 1129 1130 1131
static inline
void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
{
	int prio = rt_se_prio(rt_se);

	WARN_ON(!rt_prio(prio));
1132
	rt_rq->rt_nr_running += rt_se_nr_running(rt_se);
1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143

	inc_rt_prio(rt_rq, prio);
	inc_rt_migration(rt_se, rt_rq);
	inc_rt_group(rt_se, rt_rq);
}

static inline
void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
{
	WARN_ON(!rt_prio(rt_se_prio(rt_se)));
	WARN_ON(!rt_rq->rt_nr_running);
1144
	rt_rq->rt_nr_running -= rt_se_nr_running(rt_se);
1145 1146 1147 1148

	dec_rt_prio(rt_rq, rt_se_prio(rt_se));
	dec_rt_migration(rt_se, rt_rq);
	dec_rt_group(rt_se, rt_rq);
1149 1150
}

1151
static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
I
Ingo Molnar 已提交
1152
{
P
Peter Zijlstra 已提交
1153 1154 1155
	struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
	struct rt_prio_array *array = &rt_rq->active;
	struct rt_rq *group_rq = group_rt_rq(rt_se);
1156
	struct list_head *queue = array->queue + rt_se_prio(rt_se);
I
Ingo Molnar 已提交
1157

1158 1159 1160 1161 1162 1163 1164
	/*
	 * Don't enqueue the group if its throttled, or when empty.
	 * The latter is a consequence of the former when a child group
	 * get throttled and the current group doesn't have any other
	 * active members.
	 */
	if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
P
Peter Zijlstra 已提交
1165
		return;
1166

1167 1168 1169 1170
	if (head)
		list_add(&rt_se->run_list, queue);
	else
		list_add_tail(&rt_se->run_list, queue);
P
Peter Zijlstra 已提交
1171
	__set_bit(rt_se_prio(rt_se), array->bitmap);
1172

P
Peter Zijlstra 已提交
1173 1174 1175
	inc_rt_tasks(rt_se, rt_rq);
}

1176
static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
P
Peter Zijlstra 已提交
1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191
{
	struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
	struct rt_prio_array *array = &rt_rq->active;

	list_del_init(&rt_se->run_list);
	if (list_empty(array->queue + rt_se_prio(rt_se)))
		__clear_bit(rt_se_prio(rt_se), array->bitmap);

	dec_rt_tasks(rt_se, rt_rq);
}

/*
 * Because the prio of an upper entry depends on the lower
 * entries, we must remove entries top - down.
 */
1192
static void dequeue_rt_stack(struct sched_rt_entity *rt_se)
P
Peter Zijlstra 已提交
1193
{
1194
	struct sched_rt_entity *back = NULL;
P
Peter Zijlstra 已提交
1195

1196 1197 1198 1199 1200
	for_each_sched_rt_entity(rt_se) {
		rt_se->back = back;
		back = rt_se;
	}

1201 1202
	dequeue_top_rt_rq(rt_rq_of_se(back));

1203 1204
	for (rt_se = back; rt_se; rt_se = rt_se->back) {
		if (on_rt_rq(rt_se))
1205 1206 1207 1208
			__dequeue_rt_entity(rt_se);
	}
}

1209
static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
1210
{
1211 1212
	struct rq *rq = rq_of_rt_se(rt_se);

1213 1214
	dequeue_rt_stack(rt_se);
	for_each_sched_rt_entity(rt_se)
1215
		__enqueue_rt_entity(rt_se, head);
1216
	enqueue_top_rt_rq(&rq->rt);
1217 1218 1219 1220
}

static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
{
1221 1222
	struct rq *rq = rq_of_rt_se(rt_se);

1223 1224 1225 1226 1227 1228
	dequeue_rt_stack(rt_se);

	for_each_sched_rt_entity(rt_se) {
		struct rt_rq *rt_rq = group_rt_rq(rt_se);

		if (rt_rq && rt_rq->rt_nr_running)
1229
			__enqueue_rt_entity(rt_se, false);
1230
	}
1231
	enqueue_top_rt_rq(&rq->rt);
I
Ingo Molnar 已提交
1232 1233 1234 1235 1236
}

/*
 * Adding/removing a task to/from a priority array:
 */
1237
static void
1238
enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
P
Peter Zijlstra 已提交
1239 1240 1241
{
	struct sched_rt_entity *rt_se = &p->rt;

1242
	if (flags & ENQUEUE_WAKEUP)
P
Peter Zijlstra 已提交
1243 1244
		rt_se->timeout = 0;

1245
	enqueue_rt_entity(rt_se, flags & ENQUEUE_HEAD);
1246

1247
	if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
1248
		enqueue_pushable_task(rq, p);
P
Peter Zijlstra 已提交
1249 1250
}

1251
static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
I
Ingo Molnar 已提交
1252
{
P
Peter Zijlstra 已提交
1253
	struct sched_rt_entity *rt_se = &p->rt;
I
Ingo Molnar 已提交
1254

1255
	update_curr_rt(rq);
1256
	dequeue_rt_entity(rt_se);
1257

1258
	dequeue_pushable_task(rq, p);
I
Ingo Molnar 已提交
1259 1260 1261
}

/*
1262 1263
 * Put task to the head or the end of the run list without the overhead of
 * dequeue followed by enqueue.
I
Ingo Molnar 已提交
1264
 */
1265 1266
static void
requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
P
Peter Zijlstra 已提交
1267
{
1268
	if (on_rt_rq(rt_se)) {
1269 1270 1271 1272 1273 1274 1275
		struct rt_prio_array *array = &rt_rq->active;
		struct list_head *queue = array->queue + rt_se_prio(rt_se);

		if (head)
			list_move(&rt_se->run_list, queue);
		else
			list_move_tail(&rt_se->run_list, queue);
1276
	}
P
Peter Zijlstra 已提交
1277 1278
}

1279
static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
I
Ingo Molnar 已提交
1280
{
P
Peter Zijlstra 已提交
1281 1282
	struct sched_rt_entity *rt_se = &p->rt;
	struct rt_rq *rt_rq;
I
Ingo Molnar 已提交
1283

P
Peter Zijlstra 已提交
1284 1285
	for_each_sched_rt_entity(rt_se) {
		rt_rq = rt_rq_of_se(rt_se);
1286
		requeue_rt_entity(rt_rq, rt_se, head);
P
Peter Zijlstra 已提交
1287
	}
I
Ingo Molnar 已提交
1288 1289
}

P
Peter Zijlstra 已提交
1290
static void yield_task_rt(struct rq *rq)
I
Ingo Molnar 已提交
1291
{
1292
	requeue_task_rt(rq, rq->curr, 0);
I
Ingo Molnar 已提交
1293 1294
}

1295
#ifdef CONFIG_SMP
1296 1297
static int find_lowest_rq(struct task_struct *task);

1298
static int
1299
select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
1300
{
1301 1302
	struct task_struct *curr;
	struct rq *rq;
1303

1304
	if (p->nr_cpus_allowed == 1)
1305 1306
		goto out;

1307 1308 1309 1310
	/* For anything but wake ups, just return the task_cpu */
	if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
		goto out;

1311 1312 1313 1314 1315
	rq = cpu_rq(cpu);

	rcu_read_lock();
	curr = ACCESS_ONCE(rq->curr); /* unlocked access */

1316
	/*
1317
	 * If the current task on @p's runqueue is an RT task, then
1318 1319 1320 1321
	 * try to see if we can wake this RT task up on another
	 * runqueue. Otherwise simply start this RT task
	 * on its current runqueue.
	 *
1322 1323 1324 1325 1326 1327 1328 1329 1330
	 * We want to avoid overloading runqueues. If the woken
	 * task is a higher priority, then it will stay on this CPU
	 * and the lower prio task should be moved to another CPU.
	 * Even though this will probably make the lower prio task
	 * lose its cache, we do not want to bounce a higher task
	 * around just because it gave up its CPU, perhaps for a
	 * lock?
	 *
	 * For equal prio tasks, we just let the scheduler sort it out.
1331 1332 1333 1334 1335 1336
	 *
	 * Otherwise, just let it ride on the affined RQ and the
	 * post-schedule router will push the preempted task away
	 *
	 * This test is optimistic, if we get it wrong the load-balancer
	 * will have to sort it out.
1337
	 */
1338
	if (curr && unlikely(rt_task(curr)) &&
1339
	    (curr->nr_cpus_allowed < 2 ||
1340
	     curr->prio <= p->prio)) {
1341
		int target = find_lowest_rq(p);
1342

1343 1344
		if (target != -1)
			cpu = target;
1345
	}
1346
	rcu_read_unlock();
1347

1348
out:
1349
	return cpu;
1350
}
1351 1352 1353

static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
{
1354
	if (rq->curr->nr_cpus_allowed == 1)
1355 1356
		return;

1357
	if (p->nr_cpus_allowed != 1
1358 1359
	    && cpupri_find(&rq->rd->cpupri, p, NULL))
		return;
1360

1361 1362
	if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
		return;
1363 1364 1365 1366 1367 1368 1369

	/*
	 * There appears to be other cpus that can accept
	 * current and none to run 'p', so lets reschedule
	 * to try and push current away:
	 */
	requeue_task_rt(rq, p, 1);
1370
	resched_curr(rq);
1371 1372
}

1373 1374
#endif /* CONFIG_SMP */

I
Ingo Molnar 已提交
1375 1376 1377
/*
 * Preempt the current task with a newly woken task if needed:
 */
P
Peter Zijlstra 已提交
1378
static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flags)
I
Ingo Molnar 已提交
1379
{
1380
	if (p->prio < rq->curr->prio) {
1381
		resched_curr(rq);
1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397
		return;
	}

#ifdef CONFIG_SMP
	/*
	 * If:
	 *
	 * - the newly woken task is of equal priority to the current task
	 * - the newly woken task is non-migratable while current is migratable
	 * - current will be preempted on the next reschedule
	 *
	 * we should check to see if current can readily move to a different
	 * cpu.  If so, we will reschedule to allow the push logic to try
	 * to move current somewhere else, making room for our non-migratable
	 * task.
	 */
1398
	if (p->prio == rq->curr->prio && !test_tsk_need_resched(rq->curr))
1399
		check_preempt_equal_prio(rq, p);
1400
#endif
I
Ingo Molnar 已提交
1401 1402
}

P
Peter Zijlstra 已提交
1403 1404
static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
						   struct rt_rq *rt_rq)
I
Ingo Molnar 已提交
1405
{
P
Peter Zijlstra 已提交
1406 1407
	struct rt_prio_array *array = &rt_rq->active;
	struct sched_rt_entity *next = NULL;
I
Ingo Molnar 已提交
1408 1409 1410 1411
	struct list_head *queue;
	int idx;

	idx = sched_find_first_bit(array->bitmap);
P
Peter Zijlstra 已提交
1412
	BUG_ON(idx >= MAX_RT_PRIO);
I
Ingo Molnar 已提交
1413 1414

	queue = array->queue + idx;
P
Peter Zijlstra 已提交
1415
	next = list_entry(queue->next, struct sched_rt_entity, run_list);
1416

P
Peter Zijlstra 已提交
1417 1418
	return next;
}
I
Ingo Molnar 已提交
1419

1420
static struct task_struct *_pick_next_task_rt(struct rq *rq)
P
Peter Zijlstra 已提交
1421 1422 1423
{
	struct sched_rt_entity *rt_se;
	struct task_struct *p;
1424
	struct rt_rq *rt_rq  = &rq->rt;
P
Peter Zijlstra 已提交
1425 1426 1427

	do {
		rt_se = pick_next_rt_entity(rq, rt_rq);
1428
		BUG_ON(!rt_se);
P
Peter Zijlstra 已提交
1429 1430 1431 1432
		rt_rq = group_rt_rq(rt_se);
	} while (rt_rq);

	p = rt_task_of(rt_se);
1433
	p->se.exec_start = rq_clock_task(rq);
1434 1435 1436 1437

	return p;
}

1438 1439
static struct task_struct *
pick_next_task_rt(struct rq *rq, struct task_struct *prev)
1440
{
1441 1442 1443
	struct task_struct *p;
	struct rt_rq *rt_rq = &rq->rt;

1444
	if (need_pull_rt_task(rq, prev)) {
1445
		pull_rt_task(rq);
1446 1447
		/*
		 * pull_rt_task() can drop (and re-acquire) rq->lock; this
1448 1449
		 * means a dl or stop task can slip in, in which case we need
		 * to re-start task selection.
1450
		 */
1451 1452
		if (unlikely((rq->stop && rq->stop->on_rq) ||
			     rq->dl.dl_nr_running))
1453 1454
			return RETRY_TASK;
	}
1455

1456 1457 1458 1459 1460 1461 1462
	/*
	 * We may dequeue prev's rt_rq in put_prev_task().
	 * So, we update time before rt_nr_running check.
	 */
	if (prev->sched_class == &rt_sched_class)
		update_curr_rt(rq);

1463
	if (!rt_rq->rt_queued)
1464 1465
		return NULL;

1466
	put_prev_task(rq, prev);
1467 1468

	p = _pick_next_task_rt(rq);
1469 1470 1471 1472 1473

	/* The running task is never eligible for pushing */
	if (p)
		dequeue_pushable_task(rq, p);

P
Peter Zijlstra 已提交
1474
	set_post_schedule(rq);
1475

P
Peter Zijlstra 已提交
1476
	return p;
I
Ingo Molnar 已提交
1477 1478
}

1479
static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
I
Ingo Molnar 已提交
1480
{
1481
	update_curr_rt(rq);
1482 1483 1484 1485 1486

	/*
	 * The previous task needs to be made eligible for pushing
	 * if it is still active
	 */
1487
	if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1)
1488
		enqueue_pushable_task(rq, p);
I
Ingo Molnar 已提交
1489 1490
}

1491
#ifdef CONFIG_SMP
P
Peter Zijlstra 已提交
1492

S
Steven Rostedt 已提交
1493 1494 1495
/* Only try algorithms three times */
#define RT_MAX_TRIES 3

1496 1497 1498
static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
{
	if (!task_running(rq, p) &&
1499
	    cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
1500 1501 1502 1503
		return 1;
	return 0;
}

1504 1505 1506 1507 1508
/*
 * Return the highest pushable rq's task, which is suitable to be executed
 * on the cpu, NULL otherwise
 */
static struct task_struct *pick_highest_pushable_task(struct rq *rq, int cpu)
S
Steven Rostedt 已提交
1509
{
1510 1511
	struct plist_head *head = &rq->rt.pushable_tasks;
	struct task_struct *p;
1512

1513 1514
	if (!has_pushable_tasks(rq))
		return NULL;
1515

1516 1517 1518
	plist_for_each_entry(p, head, pushable_tasks) {
		if (pick_rt_task(rq, p, cpu))
			return p;
1519 1520
	}

1521
	return NULL;
S
Steven Rostedt 已提交
1522 1523
}

1524
static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
S
Steven Rostedt 已提交
1525

G
Gregory Haskins 已提交
1526 1527 1528
static int find_lowest_rq(struct task_struct *task)
{
	struct sched_domain *sd;
1529
	struct cpumask *lowest_mask = this_cpu_cpumask_var_ptr(local_cpu_mask);
G
Gregory Haskins 已提交
1530 1531
	int this_cpu = smp_processor_id();
	int cpu      = task_cpu(task);
G
Gregory Haskins 已提交
1532

1533 1534 1535 1536
	/* Make sure the mask is initialized first */
	if (unlikely(!lowest_mask))
		return -1;

1537
	if (task->nr_cpus_allowed == 1)
1538
		return -1; /* No other targets possible */
G
Gregory Haskins 已提交
1539

1540 1541
	if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
		return -1; /* No targets found */
G
Gregory Haskins 已提交
1542 1543 1544 1545 1546 1547 1548 1549 1550

	/*
	 * At this point we have built a mask of cpus representing the
	 * lowest priority tasks in the system.  Now we want to elect
	 * the best one based on our affinity and topology.
	 *
	 * We prioritize the last cpu that the task executed on since
	 * it is most likely cache-hot in that location.
	 */
1551
	if (cpumask_test_cpu(cpu, lowest_mask))
G
Gregory Haskins 已提交
1552 1553 1554 1555 1556 1557
		return cpu;

	/*
	 * Otherwise, we consult the sched_domains span maps to figure
	 * out which cpu is logically closest to our hot cache data.
	 */
R
Rusty Russell 已提交
1558 1559
	if (!cpumask_test_cpu(this_cpu, lowest_mask))
		this_cpu = -1; /* Skip this_cpu opt if not among lowest */
G
Gregory Haskins 已提交
1560

1561
	rcu_read_lock();
R
Rusty Russell 已提交
1562 1563 1564
	for_each_domain(cpu, sd) {
		if (sd->flags & SD_WAKE_AFFINE) {
			int best_cpu;
G
Gregory Haskins 已提交
1565

R
Rusty Russell 已提交
1566 1567 1568 1569 1570
			/*
			 * "this_cpu" is cheaper to preempt than a
			 * remote processor.
			 */
			if (this_cpu != -1 &&
1571 1572
			    cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
				rcu_read_unlock();
R
Rusty Russell 已提交
1573
				return this_cpu;
1574
			}
R
Rusty Russell 已提交
1575 1576 1577

			best_cpu = cpumask_first_and(lowest_mask,
						     sched_domain_span(sd));
1578 1579
			if (best_cpu < nr_cpu_ids) {
				rcu_read_unlock();
R
Rusty Russell 已提交
1580
				return best_cpu;
1581
			}
G
Gregory Haskins 已提交
1582 1583
		}
	}
1584
	rcu_read_unlock();
G
Gregory Haskins 已提交
1585 1586 1587 1588 1589 1590

	/*
	 * And finally, if there were no matches within the domains
	 * just give the caller *something* to work with from the compatible
	 * locations.
	 */
R
Rusty Russell 已提交
1591 1592 1593 1594 1595 1596 1597
	if (this_cpu != -1)
		return this_cpu;

	cpu = cpumask_any(lowest_mask);
	if (cpu < nr_cpu_ids)
		return cpu;
	return -1;
1598 1599 1600
}

/* Will lock the rq it finds */
1601
static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1602 1603 1604
{
	struct rq *lowest_rq = NULL;
	int tries;
1605
	int cpu;
S
Steven Rostedt 已提交
1606

1607 1608 1609
	for (tries = 0; tries < RT_MAX_TRIES; tries++) {
		cpu = find_lowest_rq(task);

1610
		if ((cpu == -1) || (cpu == rq->cpu))
S
Steven Rostedt 已提交
1611 1612
			break;

1613 1614
		lowest_rq = cpu_rq(cpu);

S
Steven Rostedt 已提交
1615
		/* if the prio of this runqueue changed, try again */
1616
		if (double_lock_balance(rq, lowest_rq)) {
S
Steven Rostedt 已提交
1617 1618 1619 1620 1621 1622
			/*
			 * We had to unlock the run queue. In
			 * the mean time, task could have
			 * migrated already or had its affinity changed.
			 * Also make sure that it wasn't scheduled on its rq.
			 */
1623
			if (unlikely(task_rq(task) != rq ||
1624
				     !cpumask_test_cpu(lowest_rq->cpu,
1625
						       tsk_cpus_allowed(task)) ||
1626
				     task_running(rq, task) ||
P
Peter Zijlstra 已提交
1627
				     !task->on_rq)) {
1628

1629
				double_unlock_balance(rq, lowest_rq);
S
Steven Rostedt 已提交
1630 1631 1632 1633 1634 1635
				lowest_rq = NULL;
				break;
			}
		}

		/* If this rq is still suitable use it. */
1636
		if (lowest_rq->rt.highest_prio.curr > task->prio)
S
Steven Rostedt 已提交
1637 1638 1639
			break;

		/* try again */
1640
		double_unlock_balance(rq, lowest_rq);
S
Steven Rostedt 已提交
1641 1642 1643 1644 1645 1646
		lowest_rq = NULL;
	}

	return lowest_rq;
}

1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658
static struct task_struct *pick_next_pushable_task(struct rq *rq)
{
	struct task_struct *p;

	if (!has_pushable_tasks(rq))
		return NULL;

	p = plist_first_entry(&rq->rt.pushable_tasks,
			      struct task_struct, pushable_tasks);

	BUG_ON(rq->cpu != task_cpu(p));
	BUG_ON(task_current(rq, p));
1659
	BUG_ON(p->nr_cpus_allowed <= 1);
1660

P
Peter Zijlstra 已提交
1661
	BUG_ON(!p->on_rq);
1662 1663 1664 1665 1666
	BUG_ON(!rt_task(p));

	return p;
}

S
Steven Rostedt 已提交
1667 1668 1669 1670 1671
/*
 * If the current CPU has more than one RT task, see if the non
 * running task can migrate over to a CPU that is running a task
 * of lesser priority.
 */
1672
static int push_rt_task(struct rq *rq)
S
Steven Rostedt 已提交
1673 1674 1675
{
	struct task_struct *next_task;
	struct rq *lowest_rq;
1676
	int ret = 0;
S
Steven Rostedt 已提交
1677

G
Gregory Haskins 已提交
1678 1679 1680
	if (!rq->rt.overloaded)
		return 0;

1681
	next_task = pick_next_pushable_task(rq);
S
Steven Rostedt 已提交
1682 1683 1684
	if (!next_task)
		return 0;

P
Peter Zijlstra 已提交
1685
retry:
1686
	if (unlikely(next_task == rq->curr)) {
1687
		WARN_ON(1);
S
Steven Rostedt 已提交
1688
		return 0;
1689
	}
S
Steven Rostedt 已提交
1690 1691 1692 1693 1694 1695

	/*
	 * It's possible that the next_task slipped in of
	 * higher priority than current. If that's the case
	 * just reschedule current.
	 */
1696
	if (unlikely(next_task->prio < rq->curr->prio)) {
1697
		resched_curr(rq);
S
Steven Rostedt 已提交
1698 1699 1700
		return 0;
	}

1701
	/* We might release rq lock */
S
Steven Rostedt 已提交
1702 1703 1704
	get_task_struct(next_task);

	/* find_lock_lowest_rq locks the rq if found */
1705
	lowest_rq = find_lock_lowest_rq(next_task, rq);
S
Steven Rostedt 已提交
1706 1707 1708
	if (!lowest_rq) {
		struct task_struct *task;
		/*
1709
		 * find_lock_lowest_rq releases rq->lock
1710 1711 1712 1713 1714
		 * so it is possible that next_task has migrated.
		 *
		 * We need to make sure that the task is still on the same
		 * run-queue and is also still the next task eligible for
		 * pushing.
S
Steven Rostedt 已提交
1715
		 */
1716
		task = pick_next_pushable_task(rq);
1717 1718
		if (task_cpu(next_task) == rq->cpu && task == next_task) {
			/*
1719 1720 1721 1722
			 * The task hasn't migrated, and is still the next
			 * eligible task, but we failed to find a run-queue
			 * to push it to.  Do not retry in this case, since
			 * other cpus will pull from us when ready.
1723 1724
			 */
			goto out;
S
Steven Rostedt 已提交
1725
		}
1726

1727 1728 1729 1730
		if (!task)
			/* No more tasks, just exit */
			goto out;

1731
		/*
1732
		 * Something has shifted, try again.
1733
		 */
1734 1735 1736
		put_task_struct(next_task);
		next_task = task;
		goto retry;
S
Steven Rostedt 已提交
1737 1738
	}

1739
	deactivate_task(rq, next_task, 0);
S
Steven Rostedt 已提交
1740 1741
	set_task_cpu(next_task, lowest_rq->cpu);
	activate_task(lowest_rq, next_task, 0);
1742
	ret = 1;
S
Steven Rostedt 已提交
1743

1744
	resched_curr(lowest_rq);
S
Steven Rostedt 已提交
1745

1746
	double_unlock_balance(rq, lowest_rq);
S
Steven Rostedt 已提交
1747 1748 1749 1750

out:
	put_task_struct(next_task);

1751
	return ret;
S
Steven Rostedt 已提交
1752 1753 1754 1755 1756 1757 1758 1759 1760
}

static void push_rt_tasks(struct rq *rq)
{
	/* push_rt_task will return true if it moved an RT */
	while (push_rt_task(rq))
		;
}

1761 1762
static int pull_rt_task(struct rq *this_rq)
{
I
Ingo Molnar 已提交
1763
	int this_cpu = this_rq->cpu, ret = 0, cpu;
1764
	struct task_struct *p;
1765 1766
	struct rq *src_rq;

1767
	if (likely(!rt_overloaded(this_rq)))
1768 1769
		return 0;

P
Peter Zijlstra 已提交
1770 1771 1772 1773 1774 1775
	/*
	 * Match the barrier from rt_set_overloaded; this guarantees that if we
	 * see overloaded we must also see the rto_mask bit.
	 */
	smp_rmb();

1776
	for_each_cpu(cpu, this_rq->rd->rto_mask) {
1777 1778 1779 1780
		if (this_cpu == cpu)
			continue;

		src_rq = cpu_rq(cpu);
1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792

		/*
		 * Don't bother taking the src_rq->lock if the next highest
		 * task is known to be lower-priority than our current task.
		 * This may look racy, but if this value is about to go
		 * logically higher, the src_rq will push this task away.
		 * And if its going logically lower, we do not care
		 */
		if (src_rq->rt.highest_prio.next >=
		    this_rq->rt.highest_prio.curr)
			continue;

1793 1794 1795
		/*
		 * We can potentially drop this_rq's lock in
		 * double_lock_balance, and another CPU could
1796
		 * alter this_rq
1797
		 */
1798
		double_lock_balance(this_rq, src_rq);
1799 1800

		/*
1801 1802
		 * We can pull only a task, which is pushable
		 * on its rq, and no others.
1803
		 */
1804
		p = pick_highest_pushable_task(src_rq, this_cpu);
1805 1806 1807 1808 1809

		/*
		 * Do we have an RT task that preempts
		 * the to-be-scheduled task?
		 */
1810
		if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
1811
			WARN_ON(p == src_rq->curr);
P
Peter Zijlstra 已提交
1812
			WARN_ON(!p->on_rq);
1813 1814 1815 1816 1817 1818 1819

			/*
			 * There's a chance that p is higher in priority
			 * than what's currently running on its cpu.
			 * This is just that p is wakeing up and hasn't
			 * had a chance to schedule. We only pull
			 * p if it is lower in priority than the
1820
			 * current task on the run queue
1821
			 */
1822
			if (p->prio < src_rq->curr->prio)
M
Mike Galbraith 已提交
1823
				goto skip;
1824 1825 1826 1827 1828 1829 1830 1831 1832

			ret = 1;

			deactivate_task(src_rq, p, 0);
			set_task_cpu(p, this_cpu);
			activate_task(this_rq, p, 0);
			/*
			 * We continue with the search, just in
			 * case there's an even higher prio task
L
Lucas De Marchi 已提交
1833
			 * in another runqueue. (low likelihood
1834 1835 1836
			 * but possible)
			 */
		}
P
Peter Zijlstra 已提交
1837
skip:
1838
		double_unlock_balance(this_rq, src_rq);
1839 1840 1841 1842 1843
	}

	return ret;
}

1844
static void post_schedule_rt(struct rq *rq)
S
Steven Rostedt 已提交
1845
{
1846
	push_rt_tasks(rq);
S
Steven Rostedt 已提交
1847 1848
}

1849 1850 1851 1852
/*
 * If we are not running and we are not going to reschedule soon, we should
 * try to push tasks away now
 */
1853
static void task_woken_rt(struct rq *rq, struct task_struct *p)
1854
{
1855
	if (!task_running(rq, p) &&
1856
	    !test_tsk_need_resched(rq->curr) &&
1857
	    has_pushable_tasks(rq) &&
1858
	    p->nr_cpus_allowed > 1 &&
1859
	    (dl_task(rq->curr) || rt_task(rq->curr)) &&
1860
	    (rq->curr->nr_cpus_allowed < 2 ||
1861
	     rq->curr->prio <= p->prio))
1862 1863 1864
		push_rt_tasks(rq);
}

1865
static void set_cpus_allowed_rt(struct task_struct *p,
1866
				const struct cpumask *new_mask)
1867
{
1868 1869
	struct rq *rq;
	int weight;
1870 1871 1872

	BUG_ON(!rt_task(p));

1873 1874
	if (!p->on_rq)
		return;
1875

1876
	weight = cpumask_weight(new_mask);
1877

1878 1879 1880 1881
	/*
	 * Only update if the process changes its state from whether it
	 * can migrate or not.
	 */
1882
	if ((p->nr_cpus_allowed > 1) == (weight > 1))
1883
		return;
1884

1885
	rq = task_rq(p);
1886

1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898
	/*
	 * The process used to be able to migrate OR it can now migrate
	 */
	if (weight <= 1) {
		if (!task_current(rq, p))
			dequeue_pushable_task(rq, p);
		BUG_ON(!rq->rt.rt_nr_migratory);
		rq->rt.rt_nr_migratory--;
	} else {
		if (!task_current(rq, p))
			enqueue_pushable_task(rq, p);
		rq->rt.rt_nr_migratory++;
1899
	}
1900 1901

	update_rt_migration(&rq->rt);
1902
}
1903

1904
/* Assumes rq->lock is held */
1905
static void rq_online_rt(struct rq *rq)
1906 1907 1908
{
	if (rq->rt.overloaded)
		rt_set_overload(rq);
1909

P
Peter Zijlstra 已提交
1910 1911
	__enable_runtime(rq);

1912
	cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
1913 1914 1915
}

/* Assumes rq->lock is held */
1916
static void rq_offline_rt(struct rq *rq)
1917 1918 1919
{
	if (rq->rt.overloaded)
		rt_clear_overload(rq);
1920

P
Peter Zijlstra 已提交
1921 1922
	__disable_runtime(rq);

1923
	cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
1924
}
1925 1926 1927 1928 1929

/*
 * When switch from the rt queue, we bring ourselves to a position
 * that we might want to pull RT tasks from other runqueues.
 */
P
Peter Zijlstra 已提交
1930
static void switched_from_rt(struct rq *rq, struct task_struct *p)
1931 1932 1933 1934 1935 1936 1937 1938
{
	/*
	 * If there are other RT tasks then we will reschedule
	 * and the scheduling of the other RT tasks will handle
	 * the balancing. But if we are the last RT task
	 * we may need to handle the pulling of RT tasks
	 * now.
	 */
1939 1940 1941 1942
	if (!p->on_rq || rq->rt.rt_nr_running)
		return;

	if (pull_rt_task(rq))
1943
		resched_curr(rq);
1944
}
1945

1946
void __init init_sched_rt_class(void)
1947 1948 1949
{
	unsigned int i;

1950
	for_each_possible_cpu(i) {
1951
		zalloc_cpumask_var_node(&per_cpu(local_cpu_mask, i),
1952
					GFP_KERNEL, cpu_to_node(i));
1953
	}
1954
}
1955 1956 1957 1958 1959 1960 1961
#endif /* CONFIG_SMP */

/*
 * When switching a task to RT, we may overload the runqueue
 * with RT tasks. In this case we try to push them off to
 * other runqueues.
 */
P
Peter Zijlstra 已提交
1962
static void switched_to_rt(struct rq *rq, struct task_struct *p)
1963 1964 1965 1966 1967 1968 1969 1970 1971 1972
{
	int check_resched = 1;

	/*
	 * If we are already running, then there's nothing
	 * that needs to be done. But if we are not running
	 * we may need to preempt the current running task.
	 * If that current running task is also an RT task
	 * then see if we can move to another run queue.
	 */
P
Peter Zijlstra 已提交
1973
	if (p->on_rq && rq->curr != p) {
1974
#ifdef CONFIG_SMP
1975
		if (p->nr_cpus_allowed > 1 && rq->rt.overloaded &&
1976
		    /* Don't resched if we changed runqueues */
1977
		    push_rt_task(rq) && rq != task_rq(p))
1978 1979 1980
			check_resched = 0;
#endif /* CONFIG_SMP */
		if (check_resched && p->prio < rq->curr->prio)
1981
			resched_curr(rq);
1982 1983 1984 1985 1986 1987 1988
	}
}

/*
 * Priority of the task has changed. This may cause
 * us to initiate a push or pull.
 */
P
Peter Zijlstra 已提交
1989 1990
static void
prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
1991
{
P
Peter Zijlstra 已提交
1992
	if (!p->on_rq)
P
Peter Zijlstra 已提交
1993 1994 1995
		return;

	if (rq->curr == p) {
1996 1997 1998 1999 2000 2001 2002 2003 2004
#ifdef CONFIG_SMP
		/*
		 * If our priority decreases while running, we
		 * may need to pull tasks to this runqueue.
		 */
		if (oldprio < p->prio)
			pull_rt_task(rq);
		/*
		 * If there's a higher priority task waiting to run
2005 2006 2007
		 * then reschedule. Note, the above pull_rt_task
		 * can release the rq lock and p could migrate.
		 * Only reschedule if p is still on the same runqueue.
2008
		 */
2009
		if (p->prio > rq->rt.highest_prio.curr && rq->curr == p)
2010
			resched_curr(rq);
2011 2012 2013
#else
		/* For UP simply resched on drop of prio */
		if (oldprio < p->prio)
2014
			resched_curr(rq);
S
Steven Rostedt 已提交
2015
#endif /* CONFIG_SMP */
2016 2017 2018 2019 2020 2021 2022
	} else {
		/*
		 * This task is not running, but if it is
		 * greater than the current running task
		 * then reschedule.
		 */
		if (p->prio < rq->curr->prio)
2023
			resched_curr(rq);
2024 2025 2026
	}
}

2027 2028 2029 2030
static void watchdog(struct rq *rq, struct task_struct *p)
{
	unsigned long soft, hard;

2031 2032 2033
	/* max may change after cur was read, this will be fixed next tick */
	soft = task_rlimit(p, RLIMIT_RTTIME);
	hard = task_rlimit_max(p, RLIMIT_RTTIME);
2034 2035 2036 2037

	if (soft != RLIM_INFINITY) {
		unsigned long next;

2038 2039 2040 2041 2042
		if (p->rt.watchdog_stamp != jiffies) {
			p->rt.timeout++;
			p->rt.watchdog_stamp = jiffies;
		}

2043
		next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
2044
		if (p->rt.timeout > next)
2045
			p->cputime_expires.sched_exp = p->se.sum_exec_runtime;
2046 2047
	}
}
I
Ingo Molnar 已提交
2048

P
Peter Zijlstra 已提交
2049
static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
I
Ingo Molnar 已提交
2050
{
2051 2052
	struct sched_rt_entity *rt_se = &p->rt;

2053 2054
	update_curr_rt(rq);

2055 2056
	watchdog(rq, p);

I
Ingo Molnar 已提交
2057 2058 2059 2060 2061 2062 2063
	/*
	 * RR tasks need a special form of timeslice management.
	 * FIFO tasks have no timeslices.
	 */
	if (p->policy != SCHED_RR)
		return;

P
Peter Zijlstra 已提交
2064
	if (--p->rt.time_slice)
I
Ingo Molnar 已提交
2065 2066
		return;

2067
	p->rt.time_slice = sched_rr_timeslice;
I
Ingo Molnar 已提交
2068

2069
	/*
L
Li Bin 已提交
2070 2071
	 * Requeue to the end of queue if we (and all of our ancestors) are not
	 * the only element on the queue
2072
	 */
2073 2074 2075 2076 2077 2078
	for_each_sched_rt_entity(rt_se) {
		if (rt_se->run_list.prev != rt_se->run_list.next) {
			requeue_task_rt(rq, p, 0);
			set_tsk_need_resched(p);
			return;
		}
2079
	}
I
Ingo Molnar 已提交
2080 2081
}

2082 2083 2084 2085
static void set_curr_task_rt(struct rq *rq)
{
	struct task_struct *p = rq->curr;

2086
	p->se.exec_start = rq_clock_task(rq);
2087 2088 2089

	/* The running task is never eligible for pushing */
	dequeue_pushable_task(rq, p);
2090 2091
}

2092
static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
2093 2094 2095 2096 2097
{
	/*
	 * Time slice is 0 for SCHED_FIFO tasks
	 */
	if (task->policy == SCHED_RR)
2098
		return sched_rr_timeslice;
2099 2100 2101 2102
	else
		return 0;
}

2103
const struct sched_class rt_sched_class = {
2104
	.next			= &fair_sched_class,
I
Ingo Molnar 已提交
2105 2106 2107 2108 2109 2110 2111 2112 2113
	.enqueue_task		= enqueue_task_rt,
	.dequeue_task		= dequeue_task_rt,
	.yield_task		= yield_task_rt,

	.check_preempt_curr	= check_preempt_curr_rt,

	.pick_next_task		= pick_next_task_rt,
	.put_prev_task		= put_prev_task_rt,

2114
#ifdef CONFIG_SMP
L
Li Zefan 已提交
2115 2116
	.select_task_rq		= select_task_rq_rt,

2117
	.set_cpus_allowed       = set_cpus_allowed_rt,
2118 2119
	.rq_online              = rq_online_rt,
	.rq_offline             = rq_offline_rt,
2120
	.post_schedule		= post_schedule_rt,
2121
	.task_woken		= task_woken_rt,
2122
	.switched_from		= switched_from_rt,
2123
#endif
I
Ingo Molnar 已提交
2124

2125
	.set_curr_task          = set_curr_task_rt,
I
Ingo Molnar 已提交
2126
	.task_tick		= task_tick_rt,
2127

2128 2129
	.get_rr_interval	= get_rr_interval_rt,

2130 2131
	.prio_changed		= prio_changed_rt,
	.switched_to		= switched_to_rt,
I
Ingo Molnar 已提交
2132
};
2133 2134 2135 2136

#ifdef CONFIG_SCHED_DEBUG
extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq);

2137
void print_rt_stats(struct seq_file *m, int cpu)
2138
{
C
Cheng Xu 已提交
2139
	rt_rq_iter_t iter;
2140 2141 2142
	struct rt_rq *rt_rq;

	rcu_read_lock();
C
Cheng Xu 已提交
2143
	for_each_rt_rq(rt_rq, iter, cpu_rq(cpu))
2144 2145 2146
		print_rt_rq(m, cpu, rt_rq);
	rcu_read_unlock();
}
2147
#endif /* CONFIG_SCHED_DEBUG */