kernel/sched/core.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  kernel/sched/core.c
 *
 *  Core kernel scheduler code and related syscalls
 *
 *  Copyright (C) 1991-2002  Linus Torvalds
 */
#define CREATE_TRACE_POINTS
#include <trace/events/sched.h>
#undef CREATE_TRACE_POINTS

#include "sched.h"

#include <linux/nospec.h>

#include <linux/kcov.h>
#include <linux/scs.h>

#include <asm/switch_to.h>
#include <asm/tlb.h>

#include "../workqueue_internal.h"
#include "../../io_uring/io-wq.h"
#include "../smpboot.h"

#include "pelt.h"
#include "smp.h"

#include <trace/hooks/sched.h>
#include <trace/hooks/dtask.h>
#include <trace/hooks/cgroup.h>

/*
 * Export tracepoints that act as a bare tracehook (ie: have no trace event
 * associated with them) to allow external modules to probe them.
 */
EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_cfs_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_rt_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_dl_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_irq_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_se_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_thermal_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_cpu_capacity_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_cfs_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_se_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_switch);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_waking);
#ifdef CONFIG_SCHEDSTATS
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_stat_sleep);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_stat_wait);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_stat_iowait);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_stat_blocked);
#endif

DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
EXPORT_SYMBOL_GPL(runqueues);

#ifdef CONFIG_SCHED_DEBUG
/*
 * Debugging: various feature bits
 *
 * If SCHED_DEBUG is disabled, each compilation unit has its own copy of
 * sysctl_sched_features, defined in sched.h, to allow constants propagation
 * at compile time and compiler optimization based on features default.
 */
#define SCHED_FEAT(name, enabled)	\
	(1UL << __SCHED_FEAT_##name) * enabled |
const_debug unsigned int sysctl_sched_features =
#include "features.h"
	0;
EXPORT_SYMBOL_GPL(sysctl_sched_features);
#undef SCHED_FEAT

/*
 * Print a warning if need_resched is set for the given duration (if
 * LATENCY_WARN is enabled).
 *
 * If sysctl_resched_latency_warn_once is set, only one warning will be shown
 * per boot.
 */
__read_mostly int sysctl_resched_latency_warn_ms = 100;
__read_mostly int sysctl_resched_latency_warn_once = 1;
#endif /* CONFIG_SCHED_DEBUG */

/*
 * Number of tasks to iterate in a single balance run.
 * Limited because this is done with IRQs disabled.
 */
const_debug unsigned int sysctl_sched_nr_migrate = 32;

/*
 * period over which we measure -rt task CPU usage in us.
 * default: 1s
 */
unsigned int sysctl_sched_rt_period = 1000000;

__read_mostly int scheduler_running;

#ifdef CONFIG_SCHED_CORE

DEFINE_STATIC_KEY_FALSE(__sched_core_enabled);

/* kernel prio, less is more */
static inline int __task_prio(struct task_struct *p)
{
	if (p->sched_class == &stop_sched_class) /* trumps deadline */
		return -2;

	if (rt_prio(p->prio)) /* includes deadline */
		return p->prio; /* [-1, 99] */

	if (p->sched_class == &idle_sched_class)
		return MAX_RT_PRIO + NICE_WIDTH; /* 140 */

	return MAX_RT_PRIO + MAX_NICE; /* 120, squash fair */
}

/*
 * l(a,b)
 * le(a,b) := !l(b,a)
 * g(a,b)  := l(b,a)
 * ge(a,b) := !l(a,b)
 */

/* real prio, less is less */
static inline bool prio_less(struct task_struct *a, struct task_struct *b, bool in_fi)
{

	int pa = __task_prio(a), pb = __task_prio(b);

	if (-pa < -pb)
		return true;

	if (-pb < -pa)
		return false;

	if (pa == -1) /* dl_prio() doesn't work because of stop_class above */
		return !dl_time_before(a->dl.deadline, b->dl.deadline);

	if (pa == MAX_RT_PRIO + MAX_NICE)	/* fair */
		return cfs_prio_less(a, b, in_fi);

	return false;
}

static inline bool __sched_core_less(struct task_struct *a, struct task_struct *b)
{
	if (a->core_cookie < b->core_cookie)
		return true;

	if (a->core_cookie > b->core_cookie)
		return false;

	/* flip prio, so high prio is leftmost */
	if (prio_less(b, a, task_rq(a)->core->core_forceidle))
		return true;

	return false;
}

#define __node_2_sc(node) rb_entry((node), struct task_struct, core_node)

static inline bool rb_sched_core_less(struct rb_node *a, const struct rb_node *b)
{
	return __sched_core_less(__node_2_sc(a), __node_2_sc(b));
}

static inline int rb_sched_core_cmp(const void *key, const struct rb_node *node)
{
	const struct task_struct *p = __node_2_sc(node);
	unsigned long cookie = (unsigned long)key;

	if (cookie < p->core_cookie)
		return -1;

	if (cookie > p->core_cookie)
		return 1;

	return 0;
}

void sched_core_enqueue(struct rq *rq, struct task_struct *p)
{
	rq->core->core_task_seq++;

	if (!p->core_cookie)
		return;

	rb_add(&p->core_node, &rq->core_tree, rb_sched_core_less);
}

void sched_core_dequeue(struct rq *rq, struct task_struct *p)
{
	rq->core->core_task_seq++;

	if (!sched_core_enqueued(p))
		return;

	rb_erase(&p->core_node, &rq->core_tree);
	RB_CLEAR_NODE(&p->core_node);
}

/*
 * Find left-most (aka, highest priority) task matching @cookie.
 */
static struct task_struct *sched_core_find(struct rq *rq, unsigned long cookie)
{
	struct rb_node *node;

	node = rb_find_first((void *)cookie, &rq->core_tree, rb_sched_core_cmp);
	/*
	 * The idle task always matches any cookie!
	 */
	if (!node)
		return idle_sched_class.pick_task(rq);

	return __node_2_sc(node);
}

static struct task_struct *sched_core_next(struct task_struct *p, unsigned long cookie)
{
	struct rb_node *node = &p->core_node;

	node = rb_next(node);
	if (!node)
		return NULL;

	p = container_of(node, struct task_struct, core_node);
	if (p->core_cookie != cookie)
		return NULL;

	return p;
}

/*
 * Magic required such that:
 *
 *	raw_spin_rq_lock(rq);
 *	...
 *	raw_spin_rq_unlock(rq);
 *
 * ends up locking and unlocking the _same_ lock, and all CPUs
 * always agree on what rq has what lock.
 *
 * XXX entirely possible to selectively enable cores, don't bother for now.
 */

static DEFINE_MUTEX(sched_core_mutex);
static atomic_t sched_core_count;
static struct cpumask sched_core_mask;

static void sched_core_lock(int cpu, unsigned long *flags)
{
	const struct cpumask *smt_mask = cpu_smt_mask(cpu);
	int t, i = 0;

	local_irq_save(*flags);
	for_each_cpu(t, smt_mask)
		raw_spin_lock_nested(&cpu_rq(t)->__lock, i++);
}

static void sched_core_unlock(int cpu, unsigned long *flags)
{
	const struct cpumask *smt_mask = cpu_smt_mask(cpu);
	int t;

	for_each_cpu(t, smt_mask)
		raw_spin_unlock(&cpu_rq(t)->__lock);
	local_irq_restore(*flags);
}

static void __sched_core_flip(bool enabled)
{
	unsigned long flags;
	int cpu, t;

	cpus_read_lock();

	/*
	 * Toggle the online cores, one by one.
	 */
	cpumask_copy(&sched_core_mask, cpu_online_mask);
	for_each_cpu(cpu, &sched_core_mask) {
		const struct cpumask *smt_mask = cpu_smt_mask(cpu);

		sched_core_lock(cpu, &flags);

		for_each_cpu(t, smt_mask)
			cpu_rq(t)->core_enabled = enabled;

		sched_core_unlock(cpu, &flags);

		cpumask_andnot(&sched_core_mask, &sched_core_mask, smt_mask);
	}

	/*
	 * Toggle the offline CPUs.
	 */
	cpumask_copy(&sched_core_mask, cpu_possible_mask);
	cpumask_andnot(&sched_core_mask, &sched_core_mask, cpu_online_mask);

	for_each_cpu(cpu, &sched_core_mask)
		cpu_rq(cpu)->core_enabled = enabled;

	cpus_read_unlock();
}

static void sched_core_assert_empty(void)
{
	int cpu;

	for_each_possible_cpu(cpu)
		WARN_ON_ONCE(!RB_EMPTY_ROOT(&cpu_rq(cpu)->core_tree));
}

static void __sched_core_enable(void)
{
	static_branch_enable(&__sched_core_enabled);
	/*
	 * Ensure all previous instances of raw_spin_rq_*lock() have finished
	 * and future ones will observe !sched_core_disabled().
	 */
	synchronize_rcu();
	__sched_core_flip(true);
	sched_core_assert_empty();
}

static void __sched_core_disable(void)
{
	sched_core_assert_empty();
	__sched_core_flip(false);
	static_branch_disable(&__sched_core_enabled);
}

void sched_core_get(void)
{
	if (atomic_inc_not_zero(&sched_core_count))
		return;

	mutex_lock(&sched_core_mutex);
	if (!atomic_read(&sched_core_count))
		__sched_core_enable();

	smp_mb__before_atomic();
	atomic_inc(&sched_core_count);
	mutex_unlock(&sched_core_mutex);
}

static void __sched_core_put(struct work_struct *work)
{
	if (atomic_dec_and_mutex_lock(&sched_core_count, &sched_core_mutex)) {
		__sched_core_disable();
		mutex_unlock(&sched_core_mutex);
	}
}

void sched_core_put(void)
{
	static DECLARE_WORK(_work, __sched_core_put);

	/*
	 * "There can be only one"
	 *
	 * Either this is the last one, or we don't actually need to do any
	 * 'work'. If it is the last *again*, we rely on
	 * WORK_STRUCT_PENDING_BIT.
	 */
	if (!atomic_add_unless(&sched_core_count, -1, 1))
		schedule_work(&_work);
}

#else /* !CONFIG_SCHED_CORE */

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

#endif /* CONFIG_SCHED_CORE */

/*
 * part of the period that we allow rt tasks to run in us.
 * default: 0.95s
 */
int sysctl_sched_rt_runtime = 950000;


/*
 * Serialization rules:
 *
 * Lock order:
 *
 *   p->pi_lock
 *     rq->lock
 *       hrtimer_cpu_base->lock (hrtimer_start() for bandwidth controls)
 *
 *  rq1->lock
 *    rq2->lock  where: rq1 < rq2
 *
 * Regular state:
 *
 * Normal scheduling state is serialized by rq->lock. __schedule() takes the
 * local CPU's rq->lock, it optionally removes the task from the runqueue and
 * always looks at the local rq data structures to find the most eligible task
 * to run next.
 *
 * Task enqueue is also under rq->lock, possibly taken from another CPU.
 * Wakeups from another LLC domain might use an IPI to transfer the enqueue to
 * the local CPU to avoid bouncing the runqueue state around [ see
 * ttwu_queue_wakelist() ]
 *
 * Task wakeup, specifically wakeups that involve migration, are horribly
 * complicated to avoid having to take two rq->locks.
 *
 * Special state:
 *
 * System-calls and anything external will use task_rq_lock() which acquires
 * both p->pi_lock and rq->lock. As a consequence the state they change is
 * stable while holding either lock:
 *
 *  - sched_setaffinity()/
 *    set_cpus_allowed_ptr():	p->cpus_ptr, p->nr_cpus_allowed
 *  - set_user_nice():		p->se.load, p->*prio
 *  - __sched_setscheduler():	p->sched_class, p->policy, p->*prio,
 *				p->se.load, p->rt_priority,
 *				p->dl.dl_{runtime, deadline, period, flags, bw, density}
 *  - sched_setnuma():		p->numa_preferred_nid
 *  - sched_move_task()/
 *    cpu_cgroup_fork():	p->sched_task_group
 *  - uclamp_update_active()	p->uclamp*
 *
 * p->state <- TASK_*:
 *
 *   is changed locklessly using set_current_state(), __set_current_state() or
 *   set_special_state(), see their respective comments, or by
 *   try_to_wake_up(). This latter uses p->pi_lock to serialize against
 *   concurrent self.
 *
 * p->on_rq <- { 0, 1 = TASK_ON_RQ_QUEUED, 2 = TASK_ON_RQ_MIGRATING }:
 *
 *   is set by activate_task() and cleared by deactivate_task(), under
 *   rq->lock. Non-zero indicates the task is runnable, the special
 *   ON_RQ_MIGRATING state is used for migration without holding both
 *   rq->locks. It indicates task_cpu() is not stable, see task_rq_lock().
 *
 * p->on_cpu <- { 0, 1 }:
 *
 *   is set by prepare_task() and cleared by finish_task() such that it will be
 *   set before p is scheduled-in and cleared after p is scheduled-out, both
 *   under rq->lock. Non-zero indicates the task is running on its CPU.
 *
 *   [ The astute reader will observe that it is possible for two tasks on one
 *     CPU to have ->on_cpu = 1 at the same time. ]
 *
 * task_cpu(p): is changed by set_task_cpu(), the rules are:
 *
 *  - Don't call set_task_cpu() on a blocked task:
 *
 *    We don't care what CPU we're not running on, this simplifies hotplug,
 *    the CPU assignment of blocked tasks isn't required to be valid.
 *
 *  - for try_to_wake_up(), called under p->pi_lock:
 *
 *    This allows try_to_wake_up() to only take one rq->lock, see its comment.
 *
 *  - for migration called under rq->lock:
 *    [ see task_on_rq_migrating() in task_rq_lock() ]
 *
 *    o move_queued_task()
 *    o detach_task()
 *
 *  - for migration called under double_rq_lock():
 *
 *    o __migrate_swap_task()
 *    o push_rt_task() / pull_rt_task()
 *    o push_dl_task() / pull_dl_task()
 *    o dl_task_offline_migration()
 *
 */

void raw_spin_rq_lock_nested(struct rq *rq, int subclass)
{
	raw_spinlock_t *lock;

	/* Matches synchronize_rcu() in __sched_core_enable() */
	preempt_disable();
	if (sched_core_disabled()) {
		raw_spin_lock_nested(&rq->__lock, subclass);
		/* preempt_count *MUST* be > 1 */
		preempt_enable_no_resched();
		return;
	}

	for (;;) {
		lock = __rq_lockp(rq);
		raw_spin_lock_nested(lock, subclass);
		if (likely(lock == __rq_lockp(rq))) {
			/* preempt_count *MUST* be > 1 */
			preempt_enable_no_resched();
			return;
		}
		raw_spin_unlock(lock);
	}
}
EXPORT_SYMBOL_GPL(raw_spin_rq_lock_nested);

bool raw_spin_rq_trylock(struct rq *rq)
{
	raw_spinlock_t *lock;
	bool ret;

	/* Matches synchronize_rcu() in __sched_core_enable() */
	preempt_disable();
	if (sched_core_disabled()) {
		ret = raw_spin_trylock(&rq->__lock);
		preempt_enable();
		return ret;
	}

	for (;;) {
		lock = __rq_lockp(rq);
		ret = raw_spin_trylock(lock);
		if (!ret || (likely(lock == __rq_lockp(rq)))) {
			preempt_enable();
			return ret;
		}
		raw_spin_unlock(lock);
	}
}

void raw_spin_rq_unlock(struct rq *rq)
{
	raw_spin_unlock(rq_lockp(rq));
}
EXPORT_SYMBOL_GPL(raw_spin_rq_unlock);

#ifdef CONFIG_SMP
/*
 * double_rq_lock - safely lock two runqueues
 */
void double_rq_lock(struct rq *rq1, struct rq *rq2)
{
	lockdep_assert_irqs_disabled();

	if (rq_order_less(rq2, rq1))
		swap(rq1, rq2);

	raw_spin_rq_lock(rq1);
	if (__rq_lockp(rq1) != __rq_lockp(rq2))
		raw_spin_rq_lock_nested(rq2, SINGLE_DEPTH_NESTING);

	double_rq_clock_clear_update(rq1, rq2);
}
EXPORT_SYMBOL_GPL(double_rq_lock);
#endif

/*
 * __task_rq_lock - lock the rq @p resides on.
 */
struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
	__acquires(rq->lock)
{
	struct rq *rq;

	lockdep_assert_held(&p->pi_lock);

	for (;;) {
		rq = task_rq(p);
		raw_spin_rq_lock(rq);
		if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
			rq_pin_lock(rq, rf);
			return rq;
		}
		raw_spin_rq_unlock(rq);

		while (unlikely(task_on_rq_migrating(p)))
			cpu_relax();
	}
}
EXPORT_SYMBOL_GPL(__task_rq_lock);

/*
 * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
 */
struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
	__acquires(p->pi_lock)
	__acquires(rq->lock)
{
	struct rq *rq;

	for (;;) {
		raw_spin_lock_irqsave(&p->pi_lock, rf->flags);
		rq = task_rq(p);
		raw_spin_rq_lock(rq);
		/*
		 *	move_queued_task()		task_rq_lock()
		 *
		 *	ACQUIRE (rq->lock)
		 *	[S] ->on_rq = MIGRATING		[L] rq = task_rq()
		 *	WMB (__set_task_cpu())		ACQUIRE (rq->lock);
		 *	[S] ->cpu = new_cpu		[L] task_rq()
		 *					[L] ->on_rq
		 *	RELEASE (rq->lock)
		 *
		 * If we observe the old CPU in task_rq_lock(), the acquire of
		 * the old rq->lock will fully serialize against the stores.
		 *
		 * If we observe the new CPU in task_rq_lock(), the address
		 * dependency headed by '[L] rq = task_rq()' and the acquire
		 * will pair with the WMB to ensure we then also see migrating.
		 */
		if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
			rq_pin_lock(rq, rf);
			return rq;
		}
		raw_spin_rq_unlock(rq);
		raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);

		while (unlikely(task_on_rq_migrating(p)))
			cpu_relax();
	}
}
EXPORT_SYMBOL_GPL(task_rq_lock);

/*
 * RQ-clock updating methods:
 */

static void update_rq_clock_task(struct rq *rq, s64 delta)
{
/*
 * In theory, the compile should just see 0 here, and optimize out the call
 * to sched_rt_avg_update. But I don't trust it...
 */
	s64 __maybe_unused steal = 0, irq_delta = 0;

#ifdef CONFIG_IRQ_TIME_ACCOUNTING
	irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;

	/*
	 * Since irq_time is only updated on {soft,}irq_exit, we might run into
	 * this case when a previous update_rq_clock() happened inside a
	 * {soft,}irq region.
	 *
	 * When this happens, we stop ->clock_task and only update the
	 * prev_irq_time stamp to account for the part that fit, so that a next
	 * update will consume the rest. This ensures ->clock_task is
	 * monotonic.
	 *
	 * It does however cause some slight miss-attribution of {soft,}irq
	 * time, a more accurate solution would be to update the irq_time using
	 * the current rq->clock timestamp, except that would require using
	 * atomic ops.
	 */
	if (irq_delta > delta)
		irq_delta = delta;

	rq->prev_irq_time += irq_delta;
	delta -= irq_delta;
#endif
#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
	if (static_key_false((&paravirt_steal_rq_enabled))) {
		steal = paravirt_steal_clock(cpu_of(rq));
		steal -= rq->prev_steal_time_rq;

		if (unlikely(steal > delta))
			steal = delta;

		rq->prev_steal_time_rq += steal;
		delta -= steal;
	}
#endif

	rq->clock_task += delta;

#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
	if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY))
		update_irq_load_avg(rq, irq_delta + steal);
#endif
	update_rq_clock_pelt(rq, delta);
}

void update_rq_clock(struct rq *rq)
{
	s64 delta;

	lockdep_assert_rq_held(rq);

	if (rq->clock_update_flags & RQCF_ACT_SKIP)
		return;

#ifdef CONFIG_SCHED_DEBUG
	if (sched_feat(WARN_DOUBLE_CLOCK))
		SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED);
	rq->clock_update_flags |= RQCF_UPDATED;
#endif

	delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
	if (delta < 0)
		return;
	rq->clock += delta;
	update_rq_clock_task(rq, delta);
}
EXPORT_SYMBOL_GPL(update_rq_clock);

#ifdef CONFIG_SCHED_HRTICK
/*
 * Use HR-timers to deliver accurate preemption points.
 */

static void hrtick_clear(struct rq *rq)
{
	if (hrtimer_active(&rq->hrtick_timer))
		hrtimer_cancel(&rq->hrtick_timer);
}

/*
 * High-resolution timer tick.
 * Runs from hardirq context with interrupts disabled.
 */
static enum hrtimer_restart hrtick(struct hrtimer *timer)
{
	struct rq *rq = container_of(timer, struct rq, hrtick_timer);
	struct rq_flags rf;

	WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());

	rq_lock(rq, &rf);
	update_rq_clock(rq);
	rq->curr->sched_class->task_tick(rq, rq->curr, 1);
	rq_unlock(rq, &rf);

	return HRTIMER_NORESTART;
}

#ifdef CONFIG_SMP

static void __hrtick_restart(struct rq *rq)
{
	struct hrtimer *timer = &rq->hrtick_timer;
	ktime_t time = rq->hrtick_time;

	hrtimer_start(timer, time, HRTIMER_MODE_ABS_PINNED_HARD);
}

/*
 * called from hardirq (IPI) context
 */
static void __hrtick_start(void *arg)
{
	struct rq *rq = arg;
	struct rq_flags rf;

	rq_lock(rq, &rf);
	__hrtick_restart(rq);
	rq_unlock(rq, &rf);
}

/*
 * Called to set the hrtick timer state.
 *
 * called with rq->lock held and irqs disabled
 */
void hrtick_start(struct rq *rq, u64 delay)
{
	struct hrtimer *timer = &rq->hrtick_timer;
	s64 delta;

	/*
	 * Don't schedule slices shorter than 10000ns, that just
	 * doesn't make sense and can cause timer DoS.
	 */
	delta = max_t(s64, delay, 10000LL);
	rq->hrtick_time = ktime_add_ns(timer->base->get_time(), delta);

	if (rq == this_rq())
		__hrtick_restart(rq);
	else
		smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
}

#else
/*
 * Called to set the hrtick timer state.
 *
 * called with rq->lock held and irqs disabled
 */
void hrtick_start(struct rq *rq, u64 delay)
{
	/*
	 * Don't schedule slices shorter than 10000ns, that just
	 * doesn't make sense. Rely on vruntime for fairness.
	 */
	delay = max_t(u64, delay, 10000LL);
	hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay),
		      HRTIMER_MODE_REL_PINNED_HARD);
}

#endif /* CONFIG_SMP */

static void hrtick_rq_init(struct rq *rq)
{
#ifdef CONFIG_SMP
	INIT_CSD(&rq->hrtick_csd, __hrtick_start, rq);
#endif
	hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
	rq->hrtick_timer.function = hrtick;
}
#else	/* CONFIG_SCHED_HRTICK */
static inline void hrtick_clear(struct rq *rq)
{
}

static inline void hrtick_rq_init(struct rq *rq)
{
}
#endif	/* CONFIG_SCHED_HRTICK */

/*
 * cmpxchg based fetch_or, macro so it works for different integer types
 */
#define fetch_or(ptr, mask)						\
	({								\
		typeof(ptr) _ptr = (ptr);				\
		typeof(mask) _mask = (mask);				\
		typeof(*_ptr) _old, _val = *_ptr;			\
									\
		for (;;) {						\
			_old = cmpxchg(_ptr, _val, _val | _mask);	\
			if (_old == _val)				\
				break;					\
			_val = _old;					\
		}							\
	_old;								\
})

#if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
/*
 * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
 * this avoids any races wrt polling state changes and thereby avoids
 * spurious IPIs.
 */
static bool set_nr_and_not_polling(struct task_struct *p)
{
	struct thread_info *ti = task_thread_info(p);
	return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
}

/*
 * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
 *
 * If this returns true, then the idle task promises to call
 * sched_ttwu_pending() and reschedule soon.
 */
static bool set_nr_if_polling(struct task_struct *p)
{
	struct thread_info *ti = task_thread_info(p);
	typeof(ti->flags) old, val = READ_ONCE(ti->flags);

	for (;;) {
		if (!(val & _TIF_POLLING_NRFLAG))
			return false;
		if (val & _TIF_NEED_RESCHED)
			return true;
		old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED);
		if (old == val)
			break;
		val = old;
	}
	return true;
}

#else
static bool set_nr_and_not_polling(struct task_struct *p)
{
	set_tsk_need_resched(p);
	return true;
}

#ifdef CONFIG_SMP
static bool set_nr_if_polling(struct task_struct *p)
{
	return false;
}
#endif
#endif

static bool __wake_q_add(struct wake_q_head *head, struct task_struct *task)
{
	struct wake_q_node *node = &task->wake_q;

	/*
	 * Atomically grab the task, if ->wake_q is !nil already it means
	 * it's already queued (either by us or someone else) and will get the
	 * wakeup due to that.
	 *
	 * In order to ensure that a pending wakeup will observe our pending
	 * state, even in the failed case, an explicit smp_mb() must be used.
	 */
	smp_mb__before_atomic();
	if (unlikely(cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL)))
		return false;

	/*
	 * The head is context local, there can be no concurrency.
	 */
	*head->lastp = node;
	head->lastp = &node->next;
	head->count++;
	return true;
}

/**
 * wake_q_add() - queue a wakeup for 'later' waking.
 * @head: the wake_q_head to add @task to
 * @task: the task to queue for 'later' wakeup
 *
 * Queue a task for later wakeup, most likely by the wake_up_q() call in the
 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
 * instantly.
 *
 * This function must be used as-if it were wake_up_process(); IOW the task
 * must be ready to be woken at this location.
 */
void wake_q_add(struct wake_q_head *head, struct task_struct *task)
{
	if (__wake_q_add(head, task))
		get_task_struct(task);
}

/**
 * wake_q_add_safe() - safely queue a wakeup for 'later' waking.
 * @head: the wake_q_head to add @task to
 * @task: the task to queue for 'later' wakeup
 *
 * Queue a task for later wakeup, most likely by the wake_up_q() call in the
 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
 * instantly.
 *
 * This function must be used as-if it were wake_up_process(); IOW the task
 * must be ready to be woken at this location.
 *
 * This function is essentially a task-safe equivalent to wake_q_add(). Callers
 * that already hold reference to @task can call the 'safe' version and trust
 * wake_q to do the right thing depending whether or not the @task is already
 * queued for wakeup.
 */
void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task)
{
	if (!__wake_q_add(head, task))
		put_task_struct(task);
}

void wake_up_q(struct wake_q_head *head)
{
	struct wake_q_node *node = head->first;

	while (node != WAKE_Q_TAIL) {
		struct task_struct *task;

		task = container_of(node, struct task_struct, wake_q);
		/* Task can safely be re-inserted now: */
		node = node->next;
		task->wake_q.next = NULL;
		task->wake_q_count = head->count;

		/*
		 * wake_up_process() executes a full barrier, which pairs with
		 * the queueing in wake_q_add() so as not to miss wakeups.
		 */
		wake_up_process(task);
		task->wake_q_count = 0;
		put_task_struct(task);
	}
}

/*
 * resched_curr - mark rq's current task 'to be rescheduled now'.
 *
 * On UP this means the setting of the need_resched flag, on SMP it
 * might also involve a cross-CPU call to trigger the scheduler on
 * the target CPU.
 */
void resched_curr(struct rq *rq)
{
	struct task_struct *curr = rq->curr;
	int cpu;

	lockdep_assert_rq_held(rq);

	if (test_tsk_need_resched(curr))
		return;

	cpu = cpu_of(rq);

	if (cpu == smp_processor_id()) {
		set_tsk_need_resched(curr);
		set_preempt_need_resched();
		return;
	}

	if (set_nr_and_not_polling(curr))
		smp_send_reschedule(cpu);
	else
		trace_sched_wake_idle_without_ipi(cpu);
}
EXPORT_SYMBOL_GPL(resched_curr);

void resched_cpu(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
	unsigned long flags;

	raw_spin_rq_lock_irqsave(rq, flags);
	if (cpu_online(cpu) || cpu == smp_processor_id())
		resched_curr(rq);
	raw_spin_rq_unlock_irqrestore(rq, flags);
}

#ifdef CONFIG_SMP
#ifdef CONFIG_NO_HZ_COMMON
/*
 * In the semi idle case, use the nearest busy CPU for migrating timers
 * from an idle CPU.  This is good for power-savings.
 *
 * We don't do similar optimization for completely idle system, as
 * selecting an idle CPU will add more delays to the timers than intended
 * (as that CPU's timer base may not be uptodate wrt jiffies etc).
 */
int get_nohz_timer_target(void)
{
	int i, cpu = smp_processor_id(), default_cpu = -1;
	struct sched_domain *sd;
	const struct cpumask *hk_mask;
	bool done = false;

	trace_android_rvh_get_nohz_timer_target(&cpu, &done);
	if (done)
		return cpu;

	if (housekeeping_cpu(cpu, HK_FLAG_TIMER)) {
		if (!idle_cpu(cpu))
			return cpu;
		default_cpu = cpu;
	}

	hk_mask = housekeeping_cpumask(HK_FLAG_TIMER);

	rcu_read_lock();
	for_each_domain(cpu, sd) {
		for_each_cpu_and(i, sched_domain_span(sd), hk_mask) {
			if (cpu == i)
				continue;

			if (!idle_cpu(i)) {
				cpu = i;
				goto unlock;
			}
		}
	}

	if (default_cpu == -1)
		default_cpu = housekeeping_any_cpu(HK_FLAG_TIMER);
	cpu = default_cpu;
unlock:
	rcu_read_unlock();
	return cpu;
}

/*
 * When add_timer_on() enqueues a timer into the timer wheel of an
 * idle CPU then this timer might expire before the next timer event
 * which is scheduled to wake up that CPU. In case of a completely
 * idle system the next event might even be infinite time into the
 * future. wake_up_idle_cpu() ensures that the CPU is woken up and
 * leaves the inner idle loop so the newly added timer is taken into
 * account when the CPU goes back to idle and evaluates the timer
 * wheel for the next timer event.
 */
static void wake_up_idle_cpu(int cpu)
{
	struct rq *rq = cpu_rq(cpu);

	if (cpu == smp_processor_id())
		return;

	if (set_nr_and_not_polling(rq->idle))
		smp_send_reschedule(cpu);
	else
		trace_sched_wake_idle_without_ipi(cpu);
}

static bool wake_up_full_nohz_cpu(int cpu)
{
	/*
	 * We just need the target to call irq_exit() and re-evaluate
	 * the next tick. The nohz full kick at least implies that.
	 * If needed we can still optimize that later with an
	 * empty IRQ.
	 */
	if (cpu_is_offline(cpu))
		return true;  /* Don't try to wake offline CPUs. */
	if (tick_nohz_full_cpu(cpu)) {
		if (cpu != smp_processor_id() ||
		    tick_nohz_tick_stopped())
			tick_nohz_full_kick_cpu(cpu);
		return true;
	}

	return false;
}

/*
 * Wake up the specified CPU.  If the CPU is going offline, it is the
 * caller's responsibility to deal with the lost wakeup, for example,
 * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
 */
void wake_up_nohz_cpu(int cpu)
{
	if (!wake_up_full_nohz_cpu(cpu))
		wake_up_idle_cpu(cpu);
}

static void nohz_csd_func(void *info)
{
	struct rq *rq = info;
	int cpu = cpu_of(rq);
	unsigned int flags;

	/*
	 * Release the rq::nohz_csd.
	 */
	flags = atomic_fetch_andnot(NOHZ_KICK_MASK | NOHZ_NEWILB_KICK, nohz_flags(cpu));
	WARN_ON(!(flags & NOHZ_KICK_MASK));

	rq->idle_balance = idle_cpu(cpu);
	if (rq->idle_balance && !need_resched()) {
		rq->nohz_idle_balance = flags;
		raise_softirq_irqoff(SCHED_SOFTIRQ);
	}
}

#endif /* CONFIG_NO_HZ_COMMON */

#ifdef CONFIG_NO_HZ_FULL
bool sched_can_stop_tick(struct rq *rq)
{
	int fifo_nr_running;

	/* Deadline tasks, even if single, need the tick */
	if (rq->dl.dl_nr_running)
		return false;

	/*
	 * If there are more than one RR tasks, we need the tick to affect the
	 * actual RR behaviour.
	 */
	if (rq->rt.rr_nr_running) {
		if (rq->rt.rr_nr_running == 1)
			return true;
		else
			return false;
	}

	/*
	 * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
	 * forced preemption between FIFO tasks.
	 */
	fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;
	if (fifo_nr_running)
		return true;

	/*
	 * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
	 * if there's more than one we need the tick for involuntary
	 * preemption.
	 */
	if (rq->nr_running > 1)
		return false;

	return true;
}
#endif /* CONFIG_NO_HZ_FULL */
#endif /* CONFIG_SMP */

#if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
			(defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
/*
 * Iterate task_group tree rooted at *from, calling @down when first entering a
 * node and @up when leaving it for the final time.
 *
 * Caller must hold rcu_lock or sufficient equivalent.
 */
int walk_tg_tree_from(struct task_group *from,
			     tg_visitor down, tg_visitor up, void *data)
{
	struct task_group *parent, *child;
	int ret;

	parent = from;

down:
	ret = (*down)(parent, data);
	if (ret)
		goto out;
	list_for_each_entry_rcu(child, &parent->children, siblings) {
		parent = child;
		goto down;

up:
		continue;
	}
	ret = (*up)(parent, data);
	if (ret || parent == from)
		goto out;

	child = parent;
	parent = parent->parent;
	if (parent)
		goto up;
out:
	return ret;
}

int tg_nop(struct task_group *tg, void *data)
{
	return 0;
}
#endif

static void set_load_weight(struct task_struct *p, bool update_load)
{
	int prio = p->static_prio - MAX_RT_PRIO;
	struct load_weight *load = &p->se.load;

	/*
	 * SCHED_IDLE tasks get minimal weight:
	 */
	if (task_has_idle_policy(p)) {
		load->weight = scale_load(WEIGHT_IDLEPRIO);
		load->inv_weight = WMULT_IDLEPRIO;
		return;
	}

	/*
	 * SCHED_OTHER tasks have to update their load when changing their
	 * weight
	 */
	if (update_load && p->sched_class == &fair_sched_class) {
		reweight_task(p, prio);
	} else {
		load->weight = scale_load(sched_prio_to_weight[prio]);
		load->inv_weight = sched_prio_to_wmult[prio];
	}
}

#ifdef CONFIG_UCLAMP_TASK
/*
 * Serializes updates of utilization clamp values
 *
 * The (slow-path) user-space triggers utilization clamp value updates which
 * can require updates on (fast-path) scheduler's data structures used to
 * support enqueue/dequeue operations.
 * While the per-CPU rq lock protects fast-path update operations, user-space
 * requests are serialized using a mutex to reduce the risk of conflicting
 * updates or API abuses.
 */
static DEFINE_MUTEX(uclamp_mutex);

/* Max allowed minimum utilization */
unsigned int sysctl_sched_uclamp_util_min = SCHED_CAPACITY_SCALE;

/* Max allowed maximum utilization */
unsigned int sysctl_sched_uclamp_util_max = SCHED_CAPACITY_SCALE;

/*
 * By default RT tasks run at the maximum performance point/capacity of the
 * system. Uclamp enforces this by always setting UCLAMP_MIN of RT tasks to
 * SCHED_CAPACITY_SCALE.
 *
 * This knob allows admins to change the default behavior when uclamp is being
 * used. In battery powered devices, particularly, running at the maximum
 * capacity and frequency will increase energy consumption and shorten the
 * battery life.
 *
 * This knob only affects RT tasks that their uclamp_se->user_defined == false.
 *
 * This knob will not override the system default sched_util_clamp_min defined
 * above.
 */
unsigned int sysctl_sched_uclamp_util_min_rt_default = SCHED_CAPACITY_SCALE;

/* All clamps are required to be less or equal than these values */
static struct uclamp_se uclamp_default[UCLAMP_CNT];

/*
 * This static key is used to reduce the uclamp overhead in the fast path. It
 * primarily disables the call to uclamp_rq_{inc, dec}() in
 * enqueue/dequeue_task().
 *
 * This allows users to continue to enable uclamp in their kernel config with
 * minimum uclamp overhead in the fast path.
 *
 * As soon as userspace modifies any of the uclamp knobs, the static key is
 * enabled, since we have an actual users that make use of uclamp
 * functionality.
 *
 * The knobs that would enable this static key are:
 *
 *   * A task modifying its uclamp value with sched_setattr().
 *   * An admin modifying the sysctl_sched_uclamp_{min, max} via procfs.
 *   * An admin modifying the cgroup cpu.uclamp.{min, max}
 */
DEFINE_STATIC_KEY_FALSE(sched_uclamp_used);
EXPORT_SYMBOL_GPL(sched_uclamp_used);

/* Integer rounded range for each bucket */
#define UCLAMP_BUCKET_DELTA DIV_ROUND_CLOSEST(SCHED_CAPACITY_SCALE, UCLAMP_BUCKETS)

#define for_each_clamp_id(clamp_id) \
	for ((clamp_id) = 0; (clamp_id) < UCLAMP_CNT; (clamp_id)++)

static inline unsigned int uclamp_bucket_id(unsigned int clamp_value)
{
	return min_t(unsigned int, clamp_value / UCLAMP_BUCKET_DELTA, UCLAMP_BUCKETS - 1);
}

static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
{
	if (clamp_id == UCLAMP_MIN)
		return 0;
	return SCHED_CAPACITY_SCALE;
}

static inline void uclamp_se_set(struct uclamp_se *uc_se,
				 unsigned int value, bool user_defined)
{
	uc_se->value = value;
	uc_se->bucket_id = uclamp_bucket_id(value);
	uc_se->user_defined = user_defined;
}

static inline unsigned int
uclamp_idle_value(struct rq *rq, enum uclamp_id clamp_id,
		  unsigned int clamp_value)
{
	/*
	 * Avoid blocked utilization pushing up the frequency when we go
	 * idle (which drops the max-clamp) by retaining the last known
	 * max-clamp.
	 */
	if (clamp_id == UCLAMP_MAX) {
		rq->uclamp_flags |= UCLAMP_FLAG_IDLE;
		return clamp_value;
	}

	return uclamp_none(UCLAMP_MIN);
}

static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
				     unsigned int clamp_value)
{
	/* Reset max-clamp retention only on idle exit */
	if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE))
		return;

	uclamp_rq_set(rq, clamp_id, clamp_value);
}

static inline
unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
				   unsigned int clamp_value)
{
	struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket;
	int bucket_id = UCLAMP_BUCKETS - 1;

	/*
	 * Since both min and max clamps are max aggregated, find the
	 * top most bucket with tasks in.
	 */
	for ( ; bucket_id >= 0; bucket_id--) {
		if (!bucket[bucket_id].tasks)
			continue;
		return bucket[bucket_id].value;
	}

	/* No tasks -- default clamp values */
	return uclamp_idle_value(rq, clamp_id, clamp_value);
}

static void __uclamp_update_util_min_rt_default(struct task_struct *p)
{
	unsigned int default_util_min;
	struct uclamp_se *uc_se;

	lockdep_assert_held(&p->pi_lock);

	uc_se = &p->uclamp_req[UCLAMP_MIN];

	/* Only sync if user didn't override the default */
	if (uc_se->user_defined)
		return;

	default_util_min = sysctl_sched_uclamp_util_min_rt_default;
	uclamp_se_set(uc_se, default_util_min, false);
}

static void uclamp_update_util_min_rt_default(struct task_struct *p)
{
	struct rq_flags rf;
	struct rq *rq;

	if (!rt_task(p))
		return;

	/* Protect updates to p->uclamp_* */
	rq = task_rq_lock(p, &rf);
	__uclamp_update_util_min_rt_default(p);
	task_rq_unlock(rq, p, &rf);
}

static void uclamp_sync_util_min_rt_default(void)
{
	struct task_struct *g, *p;

	/*
	 * copy_process()			sysctl_uclamp
	 *					  uclamp_min_rt = X;
	 *   write_lock(&tasklist_lock)		  read_lock(&tasklist_lock)
	 *   // link thread			  smp_mb__after_spinlock()
	 *   write_unlock(&tasklist_lock)	  read_unlock(&tasklist_lock);
	 *   sched_post_fork()			  for_each_process_thread()
	 *     __uclamp_sync_rt()		    __uclamp_sync_rt()
	 *
	 * Ensures that either sched_post_fork() will observe the new
	 * uclamp_min_rt or for_each_process_thread() will observe the new
	 * task.
	 */
	read_lock(&tasklist_lock);
	smp_mb__after_spinlock();
	read_unlock(&tasklist_lock);

	rcu_read_lock();
	for_each_process_thread(g, p)
		uclamp_update_util_min_rt_default(p);
	rcu_read_unlock();
}

static inline struct uclamp_se
uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id)
{
	/* Copy by value as we could modify it */
	struct uclamp_se uc_req = p->uclamp_req[clamp_id];
#ifdef CONFIG_UCLAMP_TASK_GROUP
	unsigned int tg_min, tg_max, value;

	/*
	 * Tasks in autogroups or root task group will be
	 * restricted by system defaults.
	 */
	if (task_group_is_autogroup(task_group(p)))
		return uc_req;
	if (task_group(p) == &root_task_group)
		return uc_req;

	tg_min = task_group(p)->uclamp[UCLAMP_MIN].value;
	tg_max = task_group(p)->uclamp[UCLAMP_MAX].value;
	value = uc_req.value;
	value = clamp(value, tg_min, tg_max);
	uclamp_se_set(&uc_req, value, false);
#endif

	return uc_req;
}

/*
 * The effective clamp bucket index of a task depends on, by increasing
 * priority:
 * - the task specific clamp value, when explicitly requested from userspace
 * - the task group effective clamp value, for tasks not either in the root
 *   group or in an autogroup
 * - the system default clamp value, defined by the sysadmin
 */
static inline struct uclamp_se
uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
{
	struct uclamp_se uc_req = uclamp_tg_restrict(p, clamp_id);
	struct uclamp_se uc_max = uclamp_default[clamp_id];
	struct uclamp_se uc_eff;
	int ret = 0;

	trace_android_rvh_uclamp_eff_get(p, clamp_id, &uc_max, &uc_eff, &ret);
	if (ret)
		return uc_eff;

	/* System default restrictions always apply */
	if (unlikely(uc_req.value > uc_max.value))
		return uc_max;

	return uc_req;
}

unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
{
	struct uclamp_se uc_eff;

	/* Task currently refcounted: use back-annotated (effective) value */
	if (p->uclamp[clamp_id].active)
		return (unsigned long)p->uclamp[clamp_id].value;

	uc_eff = uclamp_eff_get(p, clamp_id);

	return (unsigned long)uc_eff.value;
}
EXPORT_SYMBOL_GPL(uclamp_eff_value);

/*
 * When a task is enqueued on a rq, the clamp bucket currently defined by the
 * task's uclamp::bucket_id is refcounted on that rq. This also immediately
 * updates the rq's clamp value if required.
 *
 * Tasks can have a task-specific value requested from user-space, track
 * within each bucket the maximum value for tasks refcounted in it.
 * This "local max aggregation" allows to track the exact "requested" value
 * for each bucket when all its RUNNABLE tasks require the same clamp.
 */
static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p,
				    enum uclamp_id clamp_id)
{
	struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
	struct uclamp_se *uc_se = &p->uclamp[clamp_id];
	struct uclamp_bucket *bucket;

	lockdep_assert_rq_held(rq);

	/* Update task effective clamp */
	p->uclamp[clamp_id] = uclamp_eff_get(p, clamp_id);

	bucket = &uc_rq->bucket[uc_se->bucket_id];
	bucket->tasks++;
	uc_se->active = true;

	uclamp_idle_reset(rq, clamp_id, uc_se->value);

	/*
	 * Local max aggregation: rq buckets always track the max
	 * "requested" clamp value of its RUNNABLE tasks.
	 */
	if (bucket->tasks == 1 || uc_se->value > bucket->value)
		bucket->value = uc_se->value;

	if (uc_se->value > uclamp_rq_get(rq, clamp_id))
		uclamp_rq_set(rq, clamp_id, uc_se->value);
}

/*
 * When a task is dequeued from a rq, the clamp bucket refcounted by the task
 * is released. If this is the last task reference counting the rq's max
 * active clamp value, then the rq's clamp value is updated.
 *
 * Both refcounted tasks and rq's cached clamp values are expected to be
 * always valid. If it's detected they are not, as defensive programming,
 * enforce the expected state and warn.
 */
static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p,
				    enum uclamp_id clamp_id)
{
	struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
	struct uclamp_se *uc_se = &p->uclamp[clamp_id];
	struct uclamp_bucket *bucket;
	unsigned int bkt_clamp;
	unsigned int rq_clamp;

	lockdep_assert_rq_held(rq);

	/*
	 * If sched_uclamp_used was enabled after task @p was enqueued,
	 * we could end up with unbalanced call to uclamp_rq_dec_id().
	 *
	 * In this case the uc_se->active flag should be false since no uclamp
	 * accounting was performed at enqueue time and we can just return
	 * here.
	 *
	 * Need to be careful of the following enqueue/dequeue ordering
	 * problem too
	 *
	 *	enqueue(taskA)
	 *	// sched_uclamp_used gets enabled
	 *	enqueue(taskB)
	 *	dequeue(taskA)
	 *	// Must not decrement bucket->tasks here
	 *	dequeue(taskB)
	 *
	 * where we could end up with stale data in uc_se and
	 * bucket[uc_se->bucket_id].
	 *
	 * The following check here eliminates the possibility of such race.
	 */
	if (unlikely(!uc_se->active))
		return;

	bucket = &uc_rq->bucket[uc_se->bucket_id];

	SCHED_WARN_ON(!bucket->tasks);
	if (likely(bucket->tasks))
		bucket->tasks--;

	uc_se->active = false;

	/*
	 * Keep "local max aggregation" simple and accept to (possibly)
	 * overboost some RUNNABLE tasks in the same bucket.
	 * The rq clamp bucket value is reset to its base value whenever
	 * there are no more RUNNABLE tasks refcounting it.
	 */
	if (likely(bucket->tasks))
		return;

	rq_clamp = uclamp_rq_get(rq, clamp_id);
	/*
	 * Defensive programming: this should never happen. If it happens,
	 * e.g. due to future modification, warn and fixup the expected value.
	 */
	SCHED_WARN_ON(bucket->value > rq_clamp);
	if (bucket->value >= rq_clamp) {
		bkt_clamp = uclamp_rq_max_value(rq, clamp_id, uc_se->value);
		uclamp_rq_set(rq, clamp_id, bkt_clamp);
	}
}

static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p)
{
	enum uclamp_id clamp_id;

	/*
	 * Avoid any overhead until uclamp is actually used by the userspace.
	 *
	 * The condition is constructed such that a NOP is generated when
	 * sched_uclamp_used is disabled.
	 */
	if (!static_branch_unlikely(&sched_uclamp_used))
		return;

	if (unlikely(!p->sched_class->uclamp_enabled))
		return;

	for_each_clamp_id(clamp_id)
		uclamp_rq_inc_id(rq, p, clamp_id);

	/* Reset clamp idle holding when there is one RUNNABLE task */
	if (rq->uclamp_flags & UCLAMP_FLAG_IDLE)
		rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
}

static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p)
{
	enum uclamp_id clamp_id;

	/*
	 * Avoid any overhead until uclamp is actually used by the userspace.
	 *
	 * The condition is constructed such that a NOP is generated when
	 * sched_uclamp_used is disabled.
	 */
	if (!static_branch_unlikely(&sched_uclamp_used))
		return;

	if (unlikely(!p->sched_class->uclamp_enabled))
		return;

	for_each_clamp_id(clamp_id)
		uclamp_rq_dec_id(rq, p, clamp_id);
}

static inline void uclamp_rq_reinc_id(struct rq *rq, struct task_struct *p,
				      enum uclamp_id clamp_id)
{
	if (!p->uclamp[clamp_id].active)
		return;

	uclamp_rq_dec_id(rq, p, clamp_id);
	uclamp_rq_inc_id(rq, p, clamp_id);

	/*
	 * Make sure to clear the idle flag if we've transiently reached 0
	 * active tasks on rq.
	 */
	if (clamp_id == UCLAMP_MAX && (rq->uclamp_flags & UCLAMP_FLAG_IDLE))
		rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
}

static inline void
uclamp_update_active(struct task_struct *p)
{
	enum uclamp_id clamp_id;
	struct rq_flags rf;
	struct rq *rq;

	/*
	 * Lock the task and the rq where the task is (or was) queued.
	 *
	 * We might lock the (previous) rq of a !RUNNABLE task, but that's the
	 * price to pay to safely serialize util_{min,max} updates with
	 * enqueues, dequeues and migration operations.
	 * This is the same locking schema used by __set_cpus_allowed_ptr().
	 */
	rq = task_rq_lock(p, &rf);

	/*
	 * Setting the clamp bucket is serialized by task_rq_lock().
	 * If the task is not yet RUNNABLE and its task_struct is not
	 * affecting a valid clamp bucket, the next time it's enqueued,
	 * it will already see the updated clamp bucket value.
	 */
	for_each_clamp_id(clamp_id)
		uclamp_rq_reinc_id(rq, p, clamp_id);

	task_rq_unlock(rq, p, &rf);
}

#ifdef CONFIG_UCLAMP_TASK_GROUP
static inline void
uclamp_update_active_tasks(struct cgroup_subsys_state *css)
{
	struct css_task_iter it;
	struct task_struct *p;

	css_task_iter_start(css, 0, &it);
	while ((p = css_task_iter_next(&it)))
		uclamp_update_active(p);
	css_task_iter_end(&it);
}

static void cpu_util_update_eff(struct cgroup_subsys_state *css);
static void uclamp_update_root_tg(void)
{
	struct task_group *tg = &root_task_group;

	uclamp_se_set(&tg->uclamp_req[UCLAMP_MIN],
		      sysctl_sched_uclamp_util_min, false);
	uclamp_se_set(&tg->uclamp_req[UCLAMP_MAX],
		      sysctl_sched_uclamp_util_max, false);

	rcu_read_lock();
	cpu_util_update_eff(&root_task_group.css);
	rcu_read_unlock();
}
#else
static void uclamp_update_root_tg(void) { }
#endif

int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
				void *buffer, size_t *lenp, loff_t *ppos)
{
	bool update_root_tg = false;
	int old_min, old_max, old_min_rt;
	int result;

	mutex_lock(&uclamp_mutex);
	old_min = sysctl_sched_uclamp_util_min;
	old_max = sysctl_sched_uclamp_util_max;
	old_min_rt = sysctl_sched_uclamp_util_min_rt_default;

	result = proc_dointvec(table, write, buffer, lenp, ppos);
	if (result)
		goto undo;
	if (!write)
		goto done;

	if (sysctl_sched_uclamp_util_min > sysctl_sched_uclamp_util_max ||
	    sysctl_sched_uclamp_util_max > SCHED_CAPACITY_SCALE	||
	    sysctl_sched_uclamp_util_min_rt_default > SCHED_CAPACITY_SCALE) {

		result = -EINVAL;
		goto undo;
	}

	if (old_min != sysctl_sched_uclamp_util_min) {
		uclamp_se_set(&uclamp_default[UCLAMP_MIN],
			      sysctl_sched_uclamp_util_min, false);
		update_root_tg = true;
	}
	if (old_max != sysctl_sched_uclamp_util_max) {
		uclamp_se_set(&uclamp_default[UCLAMP_MAX],
			      sysctl_sched_uclamp_util_max, false);
		update_root_tg = true;
	}

	if (update_root_tg) {
		static_branch_enable(&sched_uclamp_used);
		uclamp_update_root_tg();
	}

	if (old_min_rt != sysctl_sched_uclamp_util_min_rt_default) {
		static_branch_enable(&sched_uclamp_used);
		uclamp_sync_util_min_rt_default();
	}

	/*
	 * We update all RUNNABLE tasks only when task groups are in use.
	 * Otherwise, keep it simple and do just a lazy update at each next
	 * task enqueue time.
	 */

	goto done;

undo:
	sysctl_sched_uclamp_util_min = old_min;
	sysctl_sched_uclamp_util_max = old_max;
	sysctl_sched_uclamp_util_min_rt_default = old_min_rt;
done:
	mutex_unlock(&uclamp_mutex);

	return result;
}

static int uclamp_validate(struct task_struct *p,
			   const struct sched_attr *attr)
{
	int util_min = p->uclamp_req[UCLAMP_MIN].value;
	int util_max = p->uclamp_req[UCLAMP_MAX].value;

	if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) {
		util_min = attr->sched_util_min;

		if (util_min + 1 > SCHED_CAPACITY_SCALE + 1)
			return -EINVAL;
	}

	if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) {
		util_max = attr->sched_util_max;

		if (util_max + 1 > SCHED_CAPACITY_SCALE + 1)
			return -EINVAL;
	}

	if (util_min != -1 && util_max != -1 && util_min > util_max)
		return -EINVAL;

	/*
	 * We have valid uclamp attributes; make sure uclamp is enabled.
	 *
	 * We need to do that here, because enabling static branches is a
	 * blocking operation which obviously cannot be done while holding
	 * scheduler locks.
	 */
	static_branch_enable(&sched_uclamp_used);

	return 0;
}

static bool uclamp_reset(const struct sched_attr *attr,
			 enum uclamp_id clamp_id,
			 struct uclamp_se *uc_se)
{
	/* Reset on sched class change for a non user-defined clamp value. */
	if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)) &&
	    !uc_se->user_defined)
		return true;

	/* Reset on sched_util_{min,max} == -1. */
	if (clamp_id == UCLAMP_MIN &&
	    attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN &&
	    attr->sched_util_min == -1) {
		return true;
	}

	if (clamp_id == UCLAMP_MAX &&
	    attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX &&
	    attr->sched_util_max == -1) {
		return true;
	}

	return false;
}

static void __setscheduler_uclamp(struct task_struct *p,
				  const struct sched_attr *attr)
{
	enum uclamp_id clamp_id;

	for_each_clamp_id(clamp_id) {
		struct uclamp_se *uc_se = &p->uclamp_req[clamp_id];
		unsigned int value;

		if (!uclamp_reset(attr, clamp_id, uc_se))
			continue;

		/*
		 * RT by default have a 100% boost value that could be modified
		 * at runtime.
		 */
		if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN))
			value = sysctl_sched_uclamp_util_min_rt_default;
		else
			value = uclamp_none(clamp_id);

		uclamp_se_set(uc_se, value, false);

	}

	if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)))
		return;

	if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN &&
	    attr->sched_util_min != -1) {
		uclamp_se_set(&p->uclamp_req[UCLAMP_MIN],
			      attr->sched_util_min, true);
		trace_android_vh_setscheduler_uclamp(p, UCLAMP_MIN, attr->sched_util_min);
	}

	if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX &&
	    attr->sched_util_max != -1) {
		uclamp_se_set(&p->uclamp_req[UCLAMP_MAX],
			      attr->sched_util_max, true);
		trace_android_vh_setscheduler_uclamp(p, UCLAMP_MAX, attr->sched_util_max);
	}
}

static void uclamp_fork(struct task_struct *p)
{
	enum uclamp_id clamp_id;

	/*
	 * We don't need to hold task_rq_lock() when updating p->uclamp_* here
	 * as the task is still at its early fork stages.
	 */
	for_each_clamp_id(clamp_id)
		p->uclamp[clamp_id].active = false;

	if (likely(!p->sched_reset_on_fork))
		return;

	for_each_clamp_id(clamp_id) {
		uclamp_se_set(&p->uclamp_req[clamp_id],
			      uclamp_none(clamp_id), false);
	}
}

static void uclamp_post_fork(struct task_struct *p)
{
	uclamp_update_util_min_rt_default(p);
}

static void __init init_uclamp_rq(struct rq *rq)
{
	enum uclamp_id clamp_id;
	struct uclamp_rq *uc_rq = rq->uclamp;

	for_each_clamp_id(clamp_id) {
		uc_rq[clamp_id] = (struct uclamp_rq) {
			.value = uclamp_none(clamp_id)
		};
	}

	rq->uclamp_flags = UCLAMP_FLAG_IDLE;
}

static void __init init_uclamp(void)
{
	struct uclamp_se uc_max = {};
	enum uclamp_id clamp_id;
	int cpu;

	for_each_possible_cpu(cpu)
		init_uclamp_rq(cpu_rq(cpu));

	for_each_clamp_id(clamp_id) {
		uclamp_se_set(&init_task.uclamp_req[clamp_id],
			      uclamp_none(clamp_id), false);
	}

	/* System defaults allow max clamp values for both indexes */
	uclamp_se_set(&uc_max, uclamp_none(UCLAMP_MAX), false);
	for_each_clamp_id(clamp_id) {
		uclamp_default[clamp_id] = uc_max;
#ifdef CONFIG_UCLAMP_TASK_GROUP
		root_task_group.uclamp_req[clamp_id] = uc_max;
		root_task_group.uclamp[clamp_id] = uc_max;
#endif
	}
}

#else /* CONFIG_UCLAMP_TASK */
static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p) { }
static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) { }
static inline int uclamp_validate(struct task_struct *p,
				  const struct sched_attr *attr)
{
	return -EOPNOTSUPP;
}
static void __setscheduler_uclamp(struct task_struct *p,
				  const struct sched_attr *attr) { }
static inline void uclamp_fork(struct task_struct *p) { }
static inline void uclamp_post_fork(struct task_struct *p) { }
static inline void init_uclamp(void) { }
#endif /* CONFIG_UCLAMP_TASK */

bool sched_task_on_rq(struct task_struct *p)
{
	return task_on_rq_queued(p);
}

static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
{
	if (!(flags & ENQUEUE_NOCLOCK))
		update_rq_clock(rq);

	if (!(flags & ENQUEUE_RESTORE)) {
		sched_info_enqueue(rq, p);
		psi_enqueue(p, flags & ENQUEUE_WAKEUP);
	}

	uclamp_rq_inc(rq, p);
	trace_android_rvh_enqueue_task(rq, p, flags);
	p->sched_class->enqueue_task(rq, p, flags);
	trace_android_rvh_after_enqueue_task(rq, p, flags);

	if (sched_core_enabled(rq))
		sched_core_enqueue(rq, p);
}

static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
{
	if (sched_core_enabled(rq))
		sched_core_dequeue(rq, p);

	if (!(flags & DEQUEUE_NOCLOCK))
		update_rq_clock(rq);

	if (!(flags & DEQUEUE_SAVE)) {
		sched_info_dequeue(rq, p);
		psi_dequeue(p, flags & DEQUEUE_SLEEP);
	}

	uclamp_rq_dec(rq, p);
	trace_android_rvh_dequeue_task(rq, p, flags);
	p->sched_class->dequeue_task(rq, p, flags);
	trace_android_rvh_after_dequeue_task(rq, p, flags);
}

void activate_task(struct rq *rq, struct task_struct *p, int flags)
{
	if (task_on_rq_migrating(p))
		flags |= ENQUEUE_MIGRATED;

	enqueue_task(rq, p, flags);

	p->on_rq = TASK_ON_RQ_QUEUED;
}
EXPORT_SYMBOL_GPL(activate_task);

void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
{
	p->on_rq = (flags & DEQUEUE_SLEEP) ? 0 : TASK_ON_RQ_MIGRATING;

	dequeue_task(rq, p, flags);
}
EXPORT_SYMBOL_GPL(deactivate_task);

static inline int __normal_prio(int policy, int rt_prio, int nice)
{
	int prio;

	if (dl_policy(policy))
		prio = MAX_DL_PRIO - 1;
	else if (rt_policy(policy))
		prio = MAX_RT_PRIO - 1 - rt_prio;
	else
		prio = NICE_TO_PRIO(nice);

	return prio;
}

/*
 * Calculate the expected normal priority: i.e. priority
 * without taking RT-inheritance into account. Might be
 * boosted by interactivity modifiers. Changes upon fork,
 * setprio syscalls, and whenever the interactivity
 * estimator recalculates.
 */
static inline int normal_prio(struct task_struct *p)
{
	return __normal_prio(p->policy, p->rt_priority, PRIO_TO_NICE(p->static_prio));
}

/*
 * Calculate the current priority, i.e. the priority
 * taken into account by the scheduler. This value might
 * be boosted by RT tasks, or might be boosted by
 * interactivity modifiers. Will be RT if the task got
 * RT-boosted. If not then it returns p->normal_prio.
 */
static int effective_prio(struct task_struct *p)
{
	p->normal_prio = normal_prio(p);
	/*
	 * If we are RT tasks or we were boosted to RT priority,
	 * keep the priority unchanged. Otherwise, update priority
	 * to the normal priority:
	 */
	if (!rt_prio(p->prio))
		return p->normal_prio;
	return p->prio;
}

/**
 * task_curr - is this task currently executing on a CPU?
 * @p: the task in question.
 *
 * Return: 1 if the task is currently executing. 0 otherwise.
 */
inline int task_curr(const struct task_struct *p)
{
	return cpu_curr(task_cpu(p)) == p;
}

/*
 * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
 * use the balance_callback list if you want balancing.
 *
 * this means any call to check_class_changed() must be followed by a call to
 * balance_callback().
 */
static inline void check_class_changed(struct rq *rq, struct task_struct *p,
				       const struct sched_class *prev_class,
				       int oldprio)
{
	if (prev_class != p->sched_class) {
		if (prev_class->switched_from)
			prev_class->switched_from(rq, p);

		p->sched_class->switched_to(rq, p);
	} else if (oldprio != p->prio || dl_task(p))
		p->sched_class->prio_changed(rq, p, oldprio);
}

void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
{
	if (p->sched_class == rq->curr->sched_class)
		rq->curr->sched_class->check_preempt_curr(rq, p, flags);
	else if (p->sched_class > rq->curr->sched_class)
		resched_curr(rq);

	/*
	 * A queue event has occurred, and we're going to schedule.  In
	 * this case, we can save a useless back to back clock update.
	 */
	if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
		rq_clock_skip_update(rq);
}
EXPORT_SYMBOL_GPL(check_preempt_curr);

#ifdef CONFIG_SMP

static void
__do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask, u32 flags);

static int __set_cpus_allowed_ptr(struct task_struct *p,
				  const struct cpumask *new_mask,
				  u32 flags);

static void migrate_disable_switch(struct rq *rq, struct task_struct *p)
{
	if (likely(!p->migration_disabled))
		return;

	if (p->cpus_ptr != &p->cpus_mask)
		return;

	/*
	 * Violates locking rules! see comment in __do_set_cpus_allowed().
	 */
	__do_set_cpus_allowed(p, cpumask_of(rq->cpu), SCA_MIGRATE_DISABLE);
}

void migrate_disable(void)
{
	struct task_struct *p = current;

	if (p->migration_disabled) {
		p->migration_disabled++;
		return;
	}

	preempt_disable();
	this_rq()->nr_pinned++;
	p->migration_disabled = 1;
	preempt_enable();
}
EXPORT_SYMBOL_GPL(migrate_disable);

void migrate_enable(void)
{
	struct task_struct *p = current;

	if (p->migration_disabled > 1) {
		p->migration_disabled--;
		return;
	}

	/*
	 * Ensure stop_task runs either before or after this, and that
	 * __set_cpus_allowed_ptr(SCA_MIGRATE_ENABLE) doesn't schedule().
	 */
	preempt_disable();
	if (p->cpus_ptr != &p->cpus_mask)
		__set_cpus_allowed_ptr(p, &p->cpus_mask, SCA_MIGRATE_ENABLE);
	/*
	 * Mustn't clear migration_disabled() until cpus_ptr points back at the
	 * regular cpus_mask, otherwise things that race (eg.
	 * select_fallback_rq) get confused.
	 */
	barrier();
	p->migration_disabled = 0;
	this_rq()->nr_pinned--;
	preempt_enable();
}
EXPORT_SYMBOL_GPL(migrate_enable);

static inline bool rq_has_pinned_tasks(struct rq *rq)
{
	return rq->nr_pinned;
}

/*
 * Per-CPU kthreads are allowed to run on !active && online CPUs, see
 * __set_cpus_allowed_ptr() and select_fallback_rq().
 */
static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
{
	bool allowed = true;

	/* When not in the task's cpumask, no point in looking further. */
	if (!cpumask_test_cpu(cpu, p->cpus_ptr))
		return false;

	/* migrate_disabled() must be allowed to finish. */
	if (is_migration_disabled(p))
		return cpu_online(cpu);

	/* check for all cases */
	trace_android_rvh_is_cpu_allowed(p, cpu, &allowed);

	/* Non kernel threads are not allowed during either online or offline. */
	if (!(p->flags & PF_KTHREAD))
		return cpu_active(cpu) && task_cpu_possible(cpu, p) && allowed;

	/* KTHREAD_IS_PER_CPU is always allowed. */
	if (kthread_is_per_cpu(p))
		return cpu_online(cpu);

	if (!allowed)
		return false;

	/* Regular kernel threads don't get to stay during offline. */
	if (cpu_dying(cpu))
		return false;

	/* But are allowed during online. */
	return cpu_online(cpu);
}

/*
 * This is how migration works:
 *
 * 1) we invoke migration_cpu_stop() on the target CPU using
 *    stop_one_cpu().
 * 2) stopper starts to run (implicitly forcing the migrated thread
 *    off the CPU)
 * 3) it checks whether the migrated task is still in the wrong runqueue.
 * 4) if it's in the wrong runqueue then the migration thread removes
 *    it and puts it into the right queue.
 * 5) stopper completes and stop_one_cpu() returns and the migration
 *    is done.
 */

/*
 * move_queued_task - move a queued task to new rq.
 *
 * Returns (locked) new rq. Old rq's lock is released.
 */
static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf,
				   struct task_struct *p, int new_cpu)
{
	int detached = 0;

	lockdep_assert_rq_held(rq);

	/*
	 * The vendor hook may drop the lock temporarily, so
	 * pass the rq flags to unpin lock. We expect the
	 * rq lock to be held after return.
	 */
	trace_android_rvh_migrate_queued_task(rq, rf, p, new_cpu, &detached);
	if (detached)
		goto attach;

	deactivate_task(rq, p, DEQUEUE_NOCLOCK);
	set_task_cpu(p, new_cpu);

attach:
	rq_unlock(rq, rf);
	rq = cpu_rq(new_cpu);

	rq_lock(rq, rf);
	BUG_ON(task_cpu(p) != new_cpu);
	activate_task(rq, p, 0);
	check_preempt_curr(rq, p, 0);

	return rq;
}

struct migration_arg {
	struct task_struct		*task;
	int				dest_cpu;
	struct set_affinity_pending	*pending;
};

/*
 * @refs: number of wait_for_completion()
 * @stop_pending: is @stop_work in use
 */
struct set_affinity_pending {
	refcount_t		refs;
	unsigned int		stop_pending;
	struct completion	done;
	struct cpu_stop_work	stop_work;
	struct migration_arg	arg;
};

/*
 * Move (not current) task off this CPU, onto the destination CPU. We're doing
 * this because either it can't run here any more (set_cpus_allowed()
 * away from this CPU, or CPU going down), or because we're
 * attempting to rebalance this task on exec (sched_exec).
 *
 * So we race with normal scheduler movements, but that's OK, as long
 * as the task is no longer on this CPU.
 */
struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf,
			  struct task_struct *p, int dest_cpu)
{
	/* Affinity changed (again). */
	if (!is_cpu_allowed(p, dest_cpu))
		return rq;

	update_rq_clock(rq);
	rq = move_queued_task(rq, rf, p, dest_cpu);

	return rq;
}
EXPORT_SYMBOL_GPL(__migrate_task);

/*
 * migration_cpu_stop - this will be executed by a highprio stopper thread
 * and performs thread migration by bumping thread off CPU then
 * 'pushing' onto another runqueue.
 */
static int migration_cpu_stop(void *data)
{
	struct migration_arg *arg = data;
	struct set_affinity_pending *pending = arg->pending;
	struct task_struct *p = arg->task;
	struct rq *rq = this_rq();
	bool complete = false;
	struct rq_flags rf;

	/*
	 * The original target CPU might have gone down and we might
	 * be on another CPU but it doesn't matter.
	 */
	local_irq_save(rf.flags);
	/*
	 * We need to explicitly wake pending tasks before running
	 * __migrate_task() such that we will not miss enforcing cpus_ptr
	 * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
	 */
	flush_smp_call_function_from_idle();

	raw_spin_lock(&p->pi_lock);
	rq_lock(rq, &rf);

	/*
	 * If we were passed a pending, then ->stop_pending was set, thus
	 * p->migration_pending must have remained stable.
	 */
	WARN_ON_ONCE(pending && pending != p->migration_pending);

	/*
	 * If task_rq(p) != rq, it cannot be migrated here, because we're
	 * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
	 * we're holding p->pi_lock.
	 */
	if (task_rq(p) == rq) {
		if (is_migration_disabled(p))
			goto out;

		if (pending) {
			p->migration_pending = NULL;
			complete = true;

			if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask))
				goto out;
		}

		if (task_on_rq_queued(p))
			rq = __migrate_task(rq, &rf, p, arg->dest_cpu);
		else
			p->wake_cpu = arg->dest_cpu;

		/*
		 * XXX __migrate_task() can fail, at which point we might end
		 * up running on a dodgy CPU, AFAICT this can only happen
		 * during CPU hotplug, at which point we'll get pushed out
		 * anyway, so it's probably not a big deal.
		 */

	} else if (pending) {
		/*
		 * This happens when we get migrated between migrate_enable()'s
		 * preempt_enable() and scheduling the stopper task. At that
		 * point we're a regular task again and not current anymore.
		 *
		 * A !PREEMPT kernel has a giant hole here, which makes it far
		 * more likely.
		 */

		/*
		 * The task moved before the stopper got to run. We're holding
		 * ->pi_lock, so the allowed mask is stable - if it got
		 * somewhere allowed, we're done.
		 */
		if (cpumask_test_cpu(task_cpu(p), p->cpus_ptr)) {
			p->migration_pending = NULL;
			complete = true;
			goto out;
		}

		/*
		 * When migrate_enable() hits a rq mis-match we can't reliably
		 * determine is_migration_disabled() and so have to chase after
		 * it.
		 */
		WARN_ON_ONCE(!pending->stop_pending);
		preempt_disable();
		task_rq_unlock(rq, p, &rf);
		stop_one_cpu_nowait(task_cpu(p), migration_cpu_stop,
				    &pending->arg, &pending->stop_work);
		preempt_enable();
		return 0;
	}
out:
	if (pending)
		pending->stop_pending = false;
	task_rq_unlock(rq, p, &rf);

	if (complete)
		complete_all(&pending->done);

	return 0;
}

int push_cpu_stop(void *arg)
{
	struct rq *lowest_rq = NULL, *rq = this_rq();
	struct task_struct *p = arg;

	raw_spin_lock_irq(&p->pi_lock);
	raw_spin_rq_lock(rq);

	if (task_rq(p) != rq)
		goto out_unlock;

	if (is_migration_disabled(p)) {
		p->migration_flags |= MDF_PUSH;
		goto out_unlock;
	}

	p->migration_flags &= ~MDF_PUSH;

	if (p->sched_class->find_lock_rq)
		lowest_rq = p->sched_class->find_lock_rq(p, rq);

	if (!lowest_rq)
		goto out_unlock;

	// XXX validate p is still the highest prio task
	if (task_rq(p) == rq) {
		deactivate_task(rq, p, 0);
		set_task_cpu(p, lowest_rq->cpu);
		activate_task(lowest_rq, p, 0);
		resched_curr(lowest_rq);
	}

	double_unlock_balance(rq, lowest_rq);

out_unlock:
	rq->push_busy = false;
	raw_spin_rq_unlock(rq);
	raw_spin_unlock_irq(&p->pi_lock);

	put_task_struct(p);
	return 0;
}

/*
 * sched_class::set_cpus_allowed must do the below, but is not required to
 * actually call this function.
 */
void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask, u32 flags)
{
	if (flags & (SCA_MIGRATE_ENABLE | SCA_MIGRATE_DISABLE)) {
		p->cpus_ptr = new_mask;
		return;
	}

	cpumask_copy(&p->cpus_mask, new_mask);
	p->nr_cpus_allowed = cpumask_weight(new_mask);
	trace_android_rvh_set_cpus_allowed_comm(p, new_mask);
}

static void
__do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask, u32 flags)
{
	struct rq *rq = task_rq(p);
	bool queued, running;

	/*
	 * This here violates the locking rules for affinity, since we're only
	 * supposed to change these variables while holding both rq->lock and
	 * p->pi_lock.
	 *
	 * HOWEVER, it magically works, because ttwu() is the only code that
	 * accesses these variables under p->pi_lock and only does so after
	 * smp_cond_load_acquire(&p->on_cpu, !VAL), and we're in __schedule()
	 * before finish_task().
	 *
	 * XXX do further audits, this smells like something putrid.
	 */
	if (flags & SCA_MIGRATE_DISABLE)
		SCHED_WARN_ON(!p->on_cpu);
	else
		lockdep_assert_held(&p->pi_lock);

	queued = task_on_rq_queued(p);
	running = task_current(rq, p);

	if (queued) {
		/*
		 * Because __kthread_bind() calls this on blocked tasks without
		 * holding rq->lock.
		 */
		lockdep_assert_rq_held(rq);
		dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
	}
	if (running)
		put_prev_task(rq, p);

	p->sched_class->set_cpus_allowed(p, new_mask, flags);

	if (queued)
		enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
	if (running)
		set_next_task(rq, p);
}

void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
{
	__do_set_cpus_allowed(p, new_mask, 0);
}

int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src,
		      int node)
{
	cpumask_t *user_mask;
	unsigned long flags;

	/*
	 * Always clear dst->user_cpus_ptr first as their user_cpus_ptr's
	 * may differ by now due to racing.
	 */
	dst->user_cpus_ptr = NULL;

	/*
	 * This check is racy and losing the race is a valid situation.
	 * It is not worth the extra overhead of taking the pi_lock on
	 * every fork/clone.
	 */
	if (data_race(!src->user_cpus_ptr))
		return 0;

	user_mask = kmalloc_node(cpumask_size(), GFP_KERNEL, node);
	if (!user_mask)
		return -ENOMEM;

	/*
	 * Use pi_lock to protect content of user_cpus_ptr
	 *
	 * Though unlikely, user_cpus_ptr can be reset to NULL by a concurrent
	 * do_set_cpus_allowed().
	 */
	raw_spin_lock_irqsave(&src->pi_lock, flags);
	if (src->user_cpus_ptr) {
		swap(dst->user_cpus_ptr, user_mask);
		cpumask_copy(dst->user_cpus_ptr, src->user_cpus_ptr);
	}
	raw_spin_unlock_irqrestore(&src->pi_lock, flags);

	if (unlikely(user_mask))
		kfree(user_mask);

	return 0;
}

static inline struct cpumask *clear_user_cpus_ptr(struct task_struct *p)
{
	struct cpumask *user_mask = NULL;

	swap(p->user_cpus_ptr, user_mask);

	return user_mask;
}

void release_user_cpus_ptr(struct task_struct *p)
{
	kfree(clear_user_cpus_ptr(p));
}

/*
 * This function is wildly self concurrent; here be dragons.
 *
 *
 * When given a valid mask, __set_cpus_allowed_ptr() must block until the
 * designated task is enqueued on an allowed CPU. If that task is currently
 * running, we have to kick it out using the CPU stopper.
 *
 * Migrate-Disable comes along and tramples all over our nice sandcastle.
 * Consider:
 *
 *     Initial conditions: P0->cpus_mask = [0, 1]
 *
 *     P0@CPU0                  P1
 *
 *     migrate_disable();
 *     <preempted>
 *                              set_cpus_allowed_ptr(P0, [1]);
 *
 * P1 *cannot* return from this set_cpus_allowed_ptr() call until P0 executes
 * its outermost migrate_enable() (i.e. it exits its Migrate-Disable region).
 * This means we need the following scheme:
 *
 *     P0@CPU0                  P1
 *
 *     migrate_disable();
 *     <preempted>
 *                              set_cpus_allowed_ptr(P0, [1]);
 *                                <blocks>
 *     <resumes>
 *     migrate_enable();
 *       __set_cpus_allowed_ptr();
 *       <wakes local stopper>
 *                         `--> <woken on migration completion>
 *
 * Now the fun stuff: there may be several P1-like tasks, i.e. multiple
 * concurrent set_cpus_allowed_ptr(P0, [*]) calls. CPU affinity changes of any
 * task p are serialized by p->pi_lock, which we can leverage: the one that
 * should come into effect at the end of the Migrate-Disable region is the last
 * one. This means we only need to track a single cpumask (i.e. p->cpus_mask),
 * but we still need to properly signal those waiting tasks at the appropriate
 * moment.
 *
 * This is implemented using struct set_affinity_pending. The first
 * __set_cpus_allowed_ptr() caller within a given Migrate-Disable region will
 * setup an instance of that struct and install it on the targeted task_struct.
 * Any and all further callers will reuse that instance. Those then wait for
 * a completion signaled at the tail of the CPU stopper callback (1), triggered
 * on the end of the Migrate-Disable region (i.e. outermost migrate_enable()).
 *
 *
 * (1) In the cases covered above. There is one more where the completion is
 * signaled within affine_move_task() itself: when a subsequent affinity request
 * occurs after the stopper bailed out due to the targeted task still being
 * Migrate-Disable. Consider:
 *
 *     Initial conditions: P0->cpus_mask = [0, 1]
 *
 *     CPU0		  P1				P2
 *     <P0>
 *       migrate_disable();
 *       <preempted>
 *                        set_cpus_allowed_ptr(P0, [1]);
 *                          <blocks>
 *     <migration/0>
 *       migration_cpu_stop()
 *         is_migration_disabled()
 *           <bails>
 *                                                       set_cpus_allowed_ptr(P0, [0, 1]);
 *                                                         <signal completion>
 *                          <awakes>
 *
 * Note that the above is safe vs a concurrent migrate_enable(), as any
 * pending affinity completion is preceded by an uninstallation of
 * p->migration_pending done with p->pi_lock held.
 */
static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flags *rf,
			    int dest_cpu, unsigned int flags)
{
	struct set_affinity_pending my_pending = { }, *pending = NULL;
	bool stop_pending, complete = false;

	/* Can the task run on the task's current CPU? If so, we're done */
	if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) {
		struct task_struct *push_task = NULL;

		if ((flags & SCA_MIGRATE_ENABLE) &&
		    (p->migration_flags & MDF_PUSH) && !rq->push_busy) {
			rq->push_busy = true;
			push_task = get_task_struct(p);
		}

		/*
		 * If there are pending waiters, but no pending stop_work,
		 * then complete now.
		 */
		pending = p->migration_pending;
		if (pending && !pending->stop_pending) {
			p->migration_pending = NULL;
			complete = true;
		}

		preempt_disable();
		task_rq_unlock(rq, p, rf);
		if (push_task) {
			stop_one_cpu_nowait(rq->cpu, push_cpu_stop,
					    p, &rq->push_work);
		}
		preempt_enable();

		if (complete)
			complete_all(&pending->done);

		return 0;
	}

	if (!(flags & SCA_MIGRATE_ENABLE)) {
		/* serialized by p->pi_lock */
		if (!p->migration_pending) {
			/* Install the request */
			refcount_set(&my_pending.refs, 1);
			init_completion(&my_pending.done);
			my_pending.arg = (struct migration_arg) {
				.task = p,
				.dest_cpu = dest_cpu,
				.pending = &my_pending,
			};

			p->migration_pending = &my_pending;
		} else {
			pending = p->migration_pending;
			refcount_inc(&pending->refs);
			/*
			 * Affinity has changed, but we've already installed a
			 * pending. migration_cpu_stop() *must* see this, else
			 * we risk a completion of the pending despite having a
			 * task on a disallowed CPU.
			 *
			 * Serialized by p->pi_lock, so this is safe.
			 */
			pending->arg.dest_cpu = dest_cpu;
		}
	}
	pending = p->migration_pending;
	/*
	 * - !MIGRATE_ENABLE:
	 *   we'll have installed a pending if there wasn't one already.
	 *
	 * - MIGRATE_ENABLE:
	 *   we're here because the current CPU isn't matching anymore,
	 *   the only way that can happen is because of a concurrent
	 *   set_cpus_allowed_ptr() call, which should then still be
	 *   pending completion.
	 *
	 * Either way, we really should have a @pending here.
	 */
	if (WARN_ON_ONCE(!pending)) {
		task_rq_unlock(rq, p, rf);
		return -EINVAL;
	}

	if (task_running(rq, p) || READ_ONCE(p->__state) == TASK_WAKING) {
		/*
		 * MIGRATE_ENABLE gets here because 'p == current', but for
		 * anything else we cannot do is_migration_disabled(), punt
		 * and have the stopper function handle it all race-free.
		 */
		stop_pending = pending->stop_pending;
		if (!stop_pending)
			pending->stop_pending = true;

		if (flags & SCA_MIGRATE_ENABLE)
			p->migration_flags &= ~MDF_PUSH;

		preempt_disable();
		task_rq_unlock(rq, p, rf);
		if (!stop_pending) {
			stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop,
					    &pending->arg, &pending->stop_work);
		}
		preempt_enable();

		if (flags & SCA_MIGRATE_ENABLE)
			return 0;
	} else {

		if (!is_migration_disabled(p)) {
			if (task_on_rq_queued(p))
				rq = move_queued_task(rq, rf, p, dest_cpu);

			if (!pending->stop_pending) {
				p->migration_pending = NULL;
				complete = true;
			}
		}
		task_rq_unlock(rq, p, rf);

		if (complete)
			complete_all(&pending->done);
	}

	wait_for_completion(&pending->done);

	if (refcount_dec_and_test(&pending->refs))
		wake_up_var(&pending->refs); /* No UaF, just an address */

	/*
	 * Block the original owner of &pending until all subsequent callers
	 * have seen the completion and decremented the refcount
	 */
	wait_var_event(&my_pending.refs, !refcount_read(&my_pending.refs));

	/* ARGH */
	WARN_ON_ONCE(my_pending.stop_pending);

	return 0;
}

/*
 * Called with both p->pi_lock and rq->lock held; drops both before returning.
 */
static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
					 const struct cpumask *new_mask,
					 u32 flags,
					 struct rq *rq,
					 struct rq_flags *rf)
	__releases(rq->lock)
	__releases(p->pi_lock)
{
	const struct cpumask *cpu_allowed_mask = task_cpu_possible_mask(p);
	const struct cpumask *cpu_valid_mask = cpu_active_mask;
	bool kthread = p->flags & PF_KTHREAD;
	struct cpumask *user_mask = NULL;
	unsigned int dest_cpu;
	int ret = 0;

	update_rq_clock(rq);

	if (kthread || is_migration_disabled(p)) {
		/*
		 * Kernel threads are allowed on online && !active CPUs,
		 * however, during cpu-hot-unplug, even these might get pushed
		 * away if not KTHREAD_IS_PER_CPU.
		 *
		 * Specifically, migration_disabled() tasks must not fail the
		 * cpumask_any_and_distribute() pick below, esp. so on
		 * SCA_MIGRATE_ENABLE, otherwise we'll not call
		 * set_cpus_allowed_common() and actually reset p->cpus_ptr.
		 */
		cpu_valid_mask = cpu_online_mask;
	}

	if (!kthread && !cpumask_subset(new_mask, cpu_allowed_mask)) {
		ret = -EINVAL;
		goto out;
	}

	/*
	 * Must re-check here, to close a race against __kthread_bind(),
	 * sched_setaffinity() is not guaranteed to observe the flag.
	 */
	if ((flags & SCA_CHECK) && (p->flags & PF_NO_SETAFFINITY)) {
		ret = -EINVAL;
		goto out;
	}

	if (!(flags & SCA_MIGRATE_ENABLE)) {
		if (cpumask_equal(&p->cpus_mask, new_mask))
			goto out;

		if (WARN_ON_ONCE(p == current &&
				 is_migration_disabled(p) &&
				 !cpumask_test_cpu(task_cpu(p), new_mask))) {
			ret = -EBUSY;
			goto out;
		}
	}

	/*
	 * Picking a ~random cpu helps in cases where we are changing affinity
	 * for groups of tasks (ie. cpuset), so that load balancing is not
	 * immediately required to distribute the tasks within their new mask.
	 */
	dest_cpu = cpumask_any_and_distribute(cpu_valid_mask, new_mask);
	trace_android_rvh_set_cpus_allowed_ptr_locked(cpu_valid_mask, new_mask, &dest_cpu);
	trace_android_rvh_set_cpus_allowed_by_task(cpu_valid_mask, new_mask, p, &dest_cpu);

	if (dest_cpu >= nr_cpu_ids) {
		ret = -EINVAL;
		goto out;
	}

	__do_set_cpus_allowed(p, new_mask, flags);

	if (flags & SCA_USER)
		user_mask = clear_user_cpus_ptr(p);

	ret = affine_move_task(rq, p, rf, dest_cpu, flags);

	kfree(user_mask);

	return ret;

out:
	task_rq_unlock(rq, p, rf);

	return ret;
}

/*
 * Change a given task's CPU affinity. Migrate the thread to a
 * proper CPU and schedule it away if the CPU it's executing on
 * is removed from the allowed bitmask.
 *
 * NOTE: the caller must have a valid reference to the task, the
 * task must not exit() & deallocate itself prematurely. The
 * call is not atomic; no spinlocks may be held.
 */
static int __set_cpus_allowed_ptr(struct task_struct *p,
				  const struct cpumask *new_mask, u32 flags)
{
	struct rq_flags rf;
	struct rq *rq;

	rq = task_rq_lock(p, &rf);
	return __set_cpus_allowed_ptr_locked(p, new_mask, flags, rq, &rf);
}

int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
{
	return __set_cpus_allowed_ptr(p, new_mask, 0);
}
EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);

/*
 * Change a given task's CPU affinity to the intersection of its current
 * affinity mask and @subset_mask, writing the resulting mask to @new_mask
 * and pointing @p->user_cpus_ptr to a copy of the old mask.
 * If the resulting mask is empty, leave the affinity unchanged and return
 * -EINVAL.
 */
static int restrict_cpus_allowed_ptr(struct task_struct *p,
				     struct cpumask *new_mask,
				     const struct cpumask *subset_mask)
{
	struct cpumask *user_mask = NULL;
	struct rq_flags rf;
	struct rq *rq;
	int err;

	if (!p->user_cpus_ptr) {
		user_mask = kmalloc(cpumask_size(), GFP_KERNEL);
		if (!user_mask)
			return -ENOMEM;
	}

	rq = task_rq_lock(p, &rf);

	/*
	 * Forcefully restricting the affinity of a deadline task is
	 * likely to cause problems, so fail and noisily override the
	 * mask entirely.
	 */
	if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
		err = -EPERM;
		goto err_unlock;
	}

	if (!cpumask_and(new_mask, &p->cpus_mask, subset_mask)) {
		err = -EINVAL;
		goto err_unlock;
	}

	/*
	 * We're about to butcher the task affinity, so keep track of what
	 * the user asked for in case we're able to restore it later on.
	 */
	if (user_mask) {
		cpumask_copy(user_mask, p->cpus_ptr);
		p->user_cpus_ptr = user_mask;
	}

	return __set_cpus_allowed_ptr_locked(p, new_mask, 0, rq, &rf);

err_unlock:
	task_rq_unlock(rq, p, &rf);
	kfree(user_mask);
	return err;
}

/*
 * Restrict the CPU affinity of task @p so that it is a subset of
 * task_cpu_possible_mask() and point @p->user_cpu_ptr to a copy of the
 * old affinity mask. If the resulting mask is empty, we warn and walk
 * up the cpuset hierarchy until we find a suitable mask.
 */
void force_compatible_cpus_allowed_ptr(struct task_struct *p)
{
	cpumask_var_t new_mask;
	const struct cpumask *override_mask = task_cpu_possible_mask(p);

	alloc_cpumask_var(&new_mask, GFP_KERNEL);

	/*
	 * __migrate_task() can fail silently in the face of concurrent
	 * offlining of the chosen destination CPU, so take the hotplug
	 * lock to ensure that the migration succeeds.
	 */
	trace_android_vh_force_compatible_pre(NULL);
	cpus_read_lock();
	if (!cpumask_available(new_mask))
		goto out_set_mask;

	if (!restrict_cpus_allowed_ptr(p, new_mask, override_mask))
		goto out_free_mask;

	/*
	 * We failed to find a valid subset of the affinity mask for the
	 * task, so override it based on its cpuset hierarchy.
	 */
	cpuset_cpus_allowed(p, new_mask);
	override_mask = new_mask;

out_set_mask:
	if (printk_ratelimit()) {
		printk_deferred("Overriding affinity for process %d (%s) to CPUs %*pbl\n",
				task_pid_nr(p), p->comm,
				cpumask_pr_args(override_mask));
	}

	WARN_ON(set_cpus_allowed_ptr(p, override_mask));
out_free_mask:
	cpus_read_unlock();
	trace_android_vh_force_compatible_post(NULL);
	free_cpumask_var(new_mask);
}

static int
__sched_setaffinity(struct task_struct *p, const struct cpumask *mask);

/*
 * Restore the affinity of a task @p which was previously restricted by a
 * call to force_compatible_cpus_allowed_ptr(). This will clear (and free)
 * @p->user_cpus_ptr.
 *
 * It is the caller's responsibility to serialise this with any calls to
 * force_compatible_cpus_allowed_ptr(@p).
 */
void relax_compatible_cpus_allowed_ptr(struct task_struct *p)
{
	struct cpumask *user_mask = p->user_cpus_ptr;
	unsigned long flags;

	/*
	 * Try to restore the old affinity mask. If this fails, then
	 * we free the mask explicitly to avoid it being inherited across
	 * a subsequent fork().
	 */
	if (!user_mask || !__sched_setaffinity(p, user_mask))
		return;

	raw_spin_lock_irqsave(&p->pi_lock, flags);
	user_mask = clear_user_cpus_ptr(p);
	raw_spin_unlock_irqrestore(&p->pi_lock, flags);

	kfree(user_mask);
}

void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
{
#ifdef CONFIG_SCHED_DEBUG
	unsigned int state = READ_ONCE(p->__state);

	/*
	 * We should never call set_task_cpu() on a blocked task,
	 * ttwu() will sort out the placement.
	 */
	WARN_ON_ONCE(state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq);

	/*
	 * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
	 * because schedstat_wait_{start,end} rebase migrating task's wait_start
	 * time relying on p->on_rq.
	 */
	WARN_ON_ONCE(state == TASK_RUNNING &&
		     p->sched_class == &fair_sched_class &&
		     (p->on_rq && !task_on_rq_migrating(p)));

#ifdef CONFIG_LOCKDEP
	/*
	 * The caller should hold either p->pi_lock or rq->lock, when changing
	 * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
	 *
	 * sched_move_task() holds both and thus holding either pins the cgroup,
	 * see task_group().
	 *
	 * Furthermore, all task_rq users should acquire both locks, see
	 * task_rq_lock().
	 */
	WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
				      lockdep_is_held(__rq_lockp(task_rq(p)))));
#endif
	/*
	 * Clearly, migrating tasks to offline CPUs is a fairly daft thing.
	 */
	WARN_ON_ONCE(!cpu_online(new_cpu));

	WARN_ON_ONCE(is_migration_disabled(p));
#endif

	trace_sched_migrate_task(p, new_cpu);

	if (task_cpu(p) != new_cpu) {
		if (p->sched_class->migrate_task_rq)
			p->sched_class->migrate_task_rq(p, new_cpu);
		p->se.nr_migrations++;
		rseq_migrate(p);
		perf_event_task_migrate(p);
		trace_android_rvh_set_task_cpu(p, new_cpu);
	}

	__set_task_cpu(p, new_cpu);
}
EXPORT_SYMBOL_GPL(set_task_cpu);

static void __migrate_swap_task(struct task_struct *p, int cpu)
{
	if (task_on_rq_queued(p)) {
		struct rq *src_rq, *dst_rq;
		struct rq_flags srf, drf;

		src_rq = task_rq(p);
		dst_rq = cpu_rq(cpu);

		rq_pin_lock(src_rq, &srf);
		rq_pin_lock(dst_rq, &drf);

		deactivate_task(src_rq, p, 0);
		set_task_cpu(p, cpu);
		activate_task(dst_rq, p, 0);
		check_preempt_curr(dst_rq, p, 0);

		rq_unpin_lock(dst_rq, &drf);
		rq_unpin_lock(src_rq, &srf);

	} else {
		/*
		 * Task isn't running anymore; make it appear like we migrated
		 * it before it went to sleep. This means on wakeup we make the
		 * previous CPU our target instead of where it really is.
		 */
		p->wake_cpu = cpu;
	}
}

struct migration_swap_arg {
	struct task_struct *src_task, *dst_task;
	int src_cpu, dst_cpu;
};

static int migrate_swap_stop(void *data)
{
	struct migration_swap_arg *arg = data;
	struct rq *src_rq, *dst_rq;
	int ret = -EAGAIN;

	if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu))
		return -EAGAIN;

	src_rq = cpu_rq(arg->src_cpu);
	dst_rq = cpu_rq(arg->dst_cpu);

	double_raw_lock(&arg->src_task->pi_lock,
			&arg->dst_task->pi_lock);
	double_rq_lock(src_rq, dst_rq);

	if (task_cpu(arg->dst_task) != arg->dst_cpu)
		goto unlock;

	if (task_cpu(arg->src_task) != arg->src_cpu)
		goto unlock;

	if (!cpumask_test_cpu(arg->dst_cpu, arg->src_task->cpus_ptr))
		goto unlock;

	if (!cpumask_test_cpu(arg->src_cpu, arg->dst_task->cpus_ptr))
		goto unlock;

	__migrate_swap_task(arg->src_task, arg->dst_cpu);
	__migrate_swap_task(arg->dst_task, arg->src_cpu);

	ret = 0;

unlock:
	double_rq_unlock(src_rq, dst_rq);
	raw_spin_unlock(&arg->dst_task->pi_lock);
	raw_spin_unlock(&arg->src_task->pi_lock);

	return ret;
}

/*
 * Cross migrate two tasks
 */
int migrate_swap(struct task_struct *cur, struct task_struct *p,
		int target_cpu, int curr_cpu)
{
	struct migration_swap_arg arg;
	int ret = -EINVAL;

	arg = (struct migration_swap_arg){
		.src_task = cur,
		.src_cpu = curr_cpu,
		.dst_task = p,
		.dst_cpu = target_cpu,
	};

	if (arg.src_cpu == arg.dst_cpu)
		goto out;

	/*
	 * These three tests are all lockless; this is OK since all of them
	 * will be re-checked with proper locks held further down the line.
	 */
	if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu))
		goto out;

	if (!cpumask_test_cpu(arg.dst_cpu, arg.src_task->cpus_ptr))
		goto out;

	if (!cpumask_test_cpu(arg.src_cpu, arg.dst_task->cpus_ptr))
		goto out;

	trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
	ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);

out:
	return ret;
}
EXPORT_SYMBOL_GPL(migrate_swap);

/*
 * wait_task_inactive - wait for a thread to unschedule.
 *
 * If @match_state is nonzero, it's the @p->state value just checked and
 * not expected to change.  If it changes, i.e. @p might have woken up,
 * then return zero.  When we succeed in waiting for @p to be off its CPU,
 * we return a positive number (its total switch count).  If a second call
 * a short while later returns the same number, the caller can be sure that
 * @p has remained unscheduled the whole time.
 *
 * The caller must ensure that the task *will* unschedule sometime soon,
 * else this function might spin for a *long* time. This function can't
 * be called with interrupts off, or it may introduce deadlock with
 * smp_call_function() if an IPI is sent by the same process we are
 * waiting to become inactive.
 */
unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state)
{
	int running, queued;
	struct rq_flags rf;
	unsigned long ncsw;
	struct rq *rq;

	for (;;) {
		/*
		 * We do the initial early heuristics without holding
		 * any task-queue locks at all. We'll only try to get
		 * the runqueue lock when things look like they will
		 * work out!
		 */
		rq = task_rq(p);

		/*
		 * If the task is actively running on another CPU
		 * still, just relax and busy-wait without holding
		 * any locks.
		 *
		 * NOTE! Since we don't hold any locks, it's not
		 * even sure that "rq" stays as the right runqueue!
		 * But we don't care, since "task_running()" will
		 * return false if the runqueue has changed and p
		 * is actually now running somewhere else!
		 */
		while (task_running(rq, p)) {
			if (match_state && unlikely(READ_ONCE(p->__state) != match_state))
				return 0;
			cpu_relax();
		}

		/*
		 * Ok, time to look more closely! We need the rq
		 * lock now, to be *sure*. If we're wrong, we'll
		 * just go back and repeat.
		 */
		rq = task_rq_lock(p, &rf);
		trace_sched_wait_task(p);
		running = task_running(rq, p);
		queued = task_on_rq_queued(p);
		ncsw = 0;
		if (!match_state || READ_ONCE(p->__state) == match_state)
			ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
		task_rq_unlock(rq, p, &rf);

		/*
		 * If it changed from the expected state, bail out now.
		 */
		if (unlikely(!ncsw))
			break;

		/*
		 * Was it really running after all now that we
		 * checked with the proper locks actually held?
		 *
		 * Oops. Go back and try again..
		 */
		if (unlikely(running)) {
			cpu_relax();
			continue;
		}

		/*
		 * It's not enough that it's not actively running,
		 * it must be off the runqueue _entirely_, and not
		 * preempted!
		 *
		 * So if it was still runnable (but just not actively
		 * running right now), it's preempted, and we should
		 * yield - it could be a while.
		 */
		if (unlikely(queued)) {
			ktime_t to = NSEC_PER_SEC / HZ;

			set_current_state(TASK_UNINTERRUPTIBLE);
			schedule_hrtimeout(&to, HRTIMER_MODE_REL);
			continue;
		}

		/*
		 * Ahh, all good. It wasn't running, and it wasn't
		 * runnable, which means that it will never become
		 * running in the future either. We're all done!
		 */
		break;
	}

	return ncsw;
}

/***
 * kick_process - kick a running thread to enter/exit the kernel
 * @p: the to-be-kicked thread
 *
 * Cause a process which is running on another CPU to enter
 * kernel-mode, without any delay. (to get signals handled.)
 *
 * NOTE: this function doesn't have to take the runqueue lock,
 * because all it wants to ensure is that the remote task enters
 * the kernel. If the IPI races and the task has been migrated
 * to another CPU then no harm is done and the purpose has been
 * achieved as well.
 */
void kick_process(struct task_struct *p)
{
	int cpu;

	preempt_disable();
	cpu = task_cpu(p);