// 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 "../../fs/io-wq.h"
#include "../smpboot.h"

#include "pelt.h"
#include "smp.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(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);

DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, 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;
#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);
        }
}

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));
}

#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))
                return;

        raw_spin_rq_lock_nested(rq2, SINGLE_DEPTH_NESTING);
}
#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();
        }
}

/*
 * 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();
        }
}

/*
 * 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);
}

#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;
        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;

                /*
                 * 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);
                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);
}

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;

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

        rcu_read_lock();
        for_each_domain(cpu, sd) {
                for_each_cpu_and(i, sched_domain_span(sd),
                        housekeeping_cpumask(HK_FLAG_TIMER)) {
                        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);

/* 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;

        WRITE_ONCE(rq->uclamp[clamp_id].value, 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];

        /* 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;
}

/*
 * 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 > READ_ONCE(uc_rq->value))
                WRITE_ONCE(uc_rq->value, 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 = READ_ONCE(uc_rq->value);
        /*
         * 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);
                WRITE_ONCE(uc_rq->value, 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_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) {
                if (p->uclamp[clamp_id].active) {
                        uclamp_rq_dec_id(rq, p, clamp_id);
                        uclamp_rq_inc_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);
        }

        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);
        }
}

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 = 0;
}

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

void activate_task(struct rq *rq, struct task_struct *p, int flags)
{
        enqueue_task(rq, p, flags);

        p->on_rq = TASK_ON_RQ_QUEUED;
}

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);
}

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