/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
 */

#include <linux/latencytop.h>
#include <linux/sched.h>
#include <linux/cpumask.h>
#include <linux/slab.h>
#include <linux/profile.h>
#include <linux/interrupt.h>
#include <linux/mempolicy.h>
#include <linux/migrate.h>
#include <linux/task_work.h>

#include <trace/events/sched.h>

#include "sched.h"

/*
 * Targeted preemption latency for CPU-bound tasks:
 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
 *
 * NOTE: this latency value is not the same as the concept of
 * 'timeslice length' - timeslices in CFS are of variable length
 * and have no persistent notion like in traditional, time-slice
 * based scheduling concepts.
 *
 * (to see the precise effective timeslice length of your workload,
 *  run vmstat and monitor the context-switches (cs) field)
 */
unsigned int sysctl_sched_latency = 6000000ULL;
unsigned int normalized_sysctl_sched_latency = 6000000ULL;

/*
 * The initial- and re-scaling of tunables is configurable
 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
 *
 * Options are:
 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
 */
enum sched_tunable_scaling sysctl_sched_tunable_scaling
        = SCHED_TUNABLESCALING_LOG;

/*
 * Minimal preemption granularity for CPU-bound tasks:
 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
 */
unsigned int sysctl_sched_min_granularity = 750000ULL;
unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;

/*
 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
 */
static unsigned int sched_nr_latency = 8;

/*
 * After fork, child runs first. If set to 0 (default) then
 * parent will (try to) run first.
 */
unsigned int sysctl_sched_child_runs_first __read_mostly;

/*
 * SCHED_OTHER wake-up granularity.
 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
 *
 * This option delays the preemption effects of decoupled workloads
 * and reduces their over-scheduling. Synchronous workloads will still
 * have immediate wakeup/sleep latencies.
 */
unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;

const_debug unsigned int sysctl_sched_migration_cost = 500000UL;

/*
 * The exponential sliding  window over which load is averaged for shares
 * distribution.
 * (default: 10msec)
 */
unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;

#ifdef CONFIG_CFS_BANDWIDTH
/*
 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
 * each time a cfs_rq requests quota.
 *
 * Note: in the case that the slice exceeds the runtime remaining (either due
 * to consumption or the quota being specified to be smaller than the slice)
 * we will always only issue the remaining available time.
 *
 * default: 5 msec, units: microseconds
  */
unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
#endif

static inline void update_load_add(struct load_weight *lw, unsigned long inc)
{
        lw->weight += inc;
        lw->inv_weight = 0;
}

static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
{
        lw->weight -= dec;
        lw->inv_weight = 0;
}

static inline void update_load_set(struct load_weight *lw, unsigned long w)
{
        lw->weight = w;
        lw->inv_weight = 0;
}

/*
 * Increase the granularity value when there are more CPUs,
 * because with more CPUs the 'effective latency' as visible
 * to users decreases. But the relationship is not linear,
 * so pick a second-best guess by going with the log2 of the
 * number of CPUs.
 *
 * This idea comes from the SD scheduler of Con Kolivas:
 */
static int get_update_sysctl_factor(void)
{
        unsigned int cpus = min_t(int, num_online_cpus(), 8);
        unsigned int factor;

        switch (sysctl_sched_tunable_scaling) {
        case SCHED_TUNABLESCALING_NONE:
                factor = 1;
                break;
        case SCHED_TUNABLESCALING_LINEAR:
                factor = cpus;
                break;
        case SCHED_TUNABLESCALING_LOG:
        default:
                factor = 1 + ilog2(cpus);
                break;
        }

        return factor;
}

static void update_sysctl(void)
{
        unsigned int factor = get_update_sysctl_factor();

#define SET_SYSCTL(name) \
        (sysctl_##name = (factor) * normalized_sysctl_##name)
        SET_SYSCTL(sched_min_granularity);
        SET_SYSCTL(sched_latency);
        SET_SYSCTL(sched_wakeup_granularity);
#undef SET_SYSCTL
}

void sched_init_granularity(void)
{
        update_sysctl();
}

#if BITS_PER_LONG == 32
# define WMULT_CONST    (~0UL)
#else
# define WMULT_CONST    (1UL << 32)
#endif

#define WMULT_SHIFT     32

/*
 * Shift right and round:
 */
#define SRR(x, y) (((x) + (1UL << ((y) - 1))) >> (y))

/*
 * delta *= weight / lw
 */
static unsigned long
calc_delta_mine(unsigned long delta_exec, unsigned long weight,
                struct load_weight *lw)
{
        u64 tmp;

        /*
         * weight can be less than 2^SCHED_LOAD_RESOLUTION for task group sched
         * entities since MIN_SHARES = 2. Treat weight as 1 if less than
         * 2^SCHED_LOAD_RESOLUTION.
         */
        if (likely(weight > (1UL << SCHED_LOAD_RESOLUTION)))
                tmp = (u64)delta_exec * scale_load_down(weight);
        else
                tmp = (u64)delta_exec;

        if (!lw->inv_weight) {
                unsigned long w = scale_load_down(lw->weight);

                if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
                        lw->inv_weight = 1;
                else if (unlikely(!w))
                        lw->inv_weight = WMULT_CONST;
                else
                        lw->inv_weight = WMULT_CONST / w;
        }

        /*
         * Check whether we'd overflow the 64-bit multiplication:
         */
        if (unlikely(tmp > WMULT_CONST))
                tmp = SRR(SRR(tmp, WMULT_SHIFT/2) * lw->inv_weight,
                        WMULT_SHIFT/2);
        else
                tmp = SRR(tmp * lw->inv_weight, WMULT_SHIFT);

        return (unsigned long)min(tmp, (u64)(unsigned long)LONG_MAX);
}


const struct sched_class fair_sched_class;

/**************************************************************
 * CFS operations on generic schedulable entities:
 */

#ifdef CONFIG_FAIR_GROUP_SCHED

/* cpu runqueue to which this cfs_rq is attached */
static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
        return cfs_rq->rq;
}

/* An entity is a task if it doesn't "own" a runqueue */
#define entity_is_task(se)      (!se->my_q)

static inline struct task_struct *task_of(struct sched_entity *se)
{
#ifdef CONFIG_SCHED_DEBUG
        WARN_ON_ONCE(!entity_is_task(se));
#endif
        return container_of(se, struct task_struct, se);
}

/* Walk up scheduling entities hierarchy */
#define for_each_sched_entity(se) \
                for (; se; se = se->parent)

static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
{
        return p->se.cfs_rq;
}

/* runqueue on which this entity is (to be) queued */
static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
{
        return se->cfs_rq;
}

/* runqueue "owned" by this group */
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
{
        return grp->my_q;
}

static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
                                       int force_update);

static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
        if (!cfs_rq->on_list) {
                /*
                 * Ensure we either appear before our parent (if already
                 * enqueued) or force our parent to appear after us when it is
                 * enqueued.  The fact that we always enqueue bottom-up
                 * reduces this to two cases.
                 */
                if (cfs_rq->tg->parent &&
                    cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
                        list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
                                &rq_of(cfs_rq)->leaf_cfs_rq_list);
                } else {
                        list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
                                &rq_of(cfs_rq)->leaf_cfs_rq_list);
                }

                cfs_rq->on_list = 1;
                /* We should have no load, but we need to update last_decay. */
                update_cfs_rq_blocked_load(cfs_rq, 0);
        }
}

static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
        if (cfs_rq->on_list) {
                list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
                cfs_rq->on_list = 0;
        }
}

/* Iterate thr' all leaf cfs_rq's on a runqueue */
#define for_each_leaf_cfs_rq(rq, cfs_rq) \
        list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)

/* Do the two (enqueued) entities belong to the same group ? */
static inline int
is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
        if (se->cfs_rq == pse->cfs_rq)
                return 1;

        return 0;
}

static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
        return se->parent;
}

/* return depth at which a sched entity is present in the hierarchy */
static inline int depth_se(struct sched_entity *se)
{
        int depth = 0;

        for_each_sched_entity(se)
                depth++;

        return depth;
}

static void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
        int se_depth, pse_depth;

        /*
         * preemption test can be made between sibling entities who are in the
         * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
         * both tasks until we find their ancestors who are siblings of common
         * parent.
         */

        /* First walk up until both entities are at same depth */
        se_depth = depth_se(*se);
        pse_depth = depth_se(*pse);

        while (se_depth > pse_depth) {
                se_depth--;
                *se = parent_entity(*se);
        }

        while (pse_depth > se_depth) {
                pse_depth--;
                *pse = parent_entity(*pse);
        }

        while (!is_same_group(*se, *pse)) {
                *se = parent_entity(*se);
                *pse = parent_entity(*pse);
        }
}

#else   /* !CONFIG_FAIR_GROUP_SCHED */

static inline struct task_struct *task_of(struct sched_entity *se)
{
        return container_of(se, struct task_struct, se);
}

static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
        return container_of(cfs_rq, struct rq, cfs);
}

#define entity_is_task(se)      1

#define for_each_sched_entity(se) \
                for (; se; se = NULL)

static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
{
        return &task_rq(p)->cfs;
}

static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
{
        struct task_struct *p = task_of(se);
        struct rq *rq = task_rq(p);

        return &rq->cfs;
}

/* runqueue "owned" by this group */
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
{
        return NULL;
}

static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
}

static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
}

#define for_each_leaf_cfs_rq(rq, cfs_rq) \
                for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)

static inline int
is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
        return 1;
}

static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
        return NULL;
}

static inline void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
}

#endif  /* CONFIG_FAIR_GROUP_SCHED */

static __always_inline
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec);

/**************************************************************
 * Scheduling class tree data structure manipulation methods:
 */

static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
{
        s64 delta = (s64)(vruntime - max_vruntime);
        if (delta > 0)
                max_vruntime = vruntime;

        return max_vruntime;
}

static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
{
        s64 delta = (s64)(vruntime - min_vruntime);
        if (delta < 0)
                min_vruntime = vruntime;

        return min_vruntime;
}

static inline int entity_before(struct sched_entity *a,
                                struct sched_entity *b)
{
        return (s64)(a->vruntime - b->vruntime) < 0;
}

static void update_min_vruntime(struct cfs_rq *cfs_rq)
{
        u64 vruntime = cfs_rq->min_vruntime;

        if (cfs_rq->curr)
                vruntime = cfs_rq->curr->vruntime;

        if (cfs_rq->rb_leftmost) {
                struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
                                                   struct sched_entity,
                                                   run_node);

                if (!cfs_rq->curr)
                        vruntime = se->vruntime;
                else
                        vruntime = min_vruntime(vruntime, se->vruntime);
        }

        /* ensure we never gain time by being placed backwards. */
        cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
#ifndef CONFIG_64BIT
        smp_wmb();
        cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
}

/*
 * Enqueue an entity into the rb-tree:
 */
static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
        struct rb_node *parent = NULL;
        struct sched_entity *entry;
        int leftmost = 1;

        /*
         * Find the right place in the rbtree:
         */
        while (*link) {
                parent = *link;
                entry = rb_entry(parent, struct sched_entity, run_node);
                /*
                 * We dont care about collisions. Nodes with
                 * the same key stay together.
                 */
                if (entity_before(se, entry)) {
                        link = &parent->rb_left;
                } else {
                        link = &parent->rb_right;
                        leftmost = 0;
                }
        }

        /*
         * Maintain a cache of leftmost tree entries (it is frequently
         * used):
         */
        if (leftmost)
                cfs_rq->rb_leftmost = &se->run_node;

        rb_link_node(&se->run_node, parent, link);
        rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
}

static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        if (cfs_rq->rb_leftmost == &se->run_node) {
                struct rb_node *next_node;

                next_node = rb_next(&se->run_node);
                cfs_rq->rb_leftmost = next_node;
        }

        rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
}

struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
{
        struct rb_node *left = cfs_rq->rb_leftmost;

        if (!left)
                return NULL;

        return rb_entry(left, struct sched_entity, run_node);
}

static struct sched_entity *__pick_next_entity(struct sched_entity *se)
{
        struct rb_node *next = rb_next(&se->run_node);

        if (!next)
                return NULL;

        return rb_entry(next, struct sched_entity, run_node);
}

#ifdef CONFIG_SCHED_DEBUG
struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
{
        struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);

        if (!last)
                return NULL;

        return rb_entry(last, struct sched_entity, run_node);
}

/**************************************************************
 * Scheduling class statistics methods:
 */

int sched_proc_update_handler(struct ctl_table *table, int write,
                void __user *buffer, size_t *lenp,
                loff_t *ppos)
{
        int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
        int factor = get_update_sysctl_factor();

        if (ret || !write)
                return ret;

        sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
                                        sysctl_sched_min_granularity);

#define WRT_SYSCTL(name) \
        (normalized_sysctl_##name = sysctl_##name / (factor))
        WRT_SYSCTL(sched_min_granularity);
        WRT_SYSCTL(sched_latency);
        WRT_SYSCTL(sched_wakeup_granularity);
#undef WRT_SYSCTL

        return 0;
}
#endif

/*
 * delta /= w
 */
static inline unsigned long
calc_delta_fair(unsigned long delta, struct sched_entity *se)
{
        if (unlikely(se->load.weight != NICE_0_LOAD))
                delta = calc_delta_mine(delta, NICE_0_LOAD, &se->load);

        return delta;
}

/*
 * The idea is to set a period in which each task runs once.
 *
 * When there are too many tasks (sched_nr_latency) we have to stretch
 * this period because otherwise the slices get too small.
 *
 * p = (nr <= nl) ? l : l*nr/nl
 */
static u64 __sched_period(unsigned long nr_running)
{
        u64 period = sysctl_sched_latency;
        unsigned long nr_latency = sched_nr_latency;

        if (unlikely(nr_running > nr_latency)) {
                period = sysctl_sched_min_granularity;
                period *= nr_running;
        }

        return period;
}

/*
 * We calculate the wall-time slice from the period by taking a part
 * proportional to the weight.
 *
 * s = p*P[w/rw]
 */
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);

        for_each_sched_entity(se) {
                struct load_weight *load;
                struct load_weight lw;

                cfs_rq = cfs_rq_of(se);
                load = &cfs_rq->load;

                if (unlikely(!se->on_rq)) {
                        lw = cfs_rq->load;

                        update_load_add(&lw, se->load.weight);
                        load = &lw;
                }
                slice = calc_delta_mine(slice, se->load.weight, load);
        }
        return slice;
}

/*
 * We calculate the vruntime slice of a to-be-inserted task.
 *
 * vs = s/w
 */
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        return calc_delta_fair(sched_slice(cfs_rq, se), se);
}

#ifdef CONFIG_SMP
static inline void __update_task_entity_contrib(struct sched_entity *se);

/* Give new task start runnable values to heavy its load in infant time */
void init_task_runnable_average(struct task_struct *p)
{
        u32 slice;

        p->se.avg.decay_count = 0;
        slice = sched_slice(task_cfs_rq(p), &p->se) >> 10;
        p->se.avg.runnable_avg_sum = slice;
        p->se.avg.runnable_avg_period = slice;
        __update_task_entity_contrib(&p->se);
}
#else
void init_task_runnable_average(struct task_struct *p)
{
}
#endif

/*
 * Update the current task's runtime statistics. Skip current tasks that
 * are not in our scheduling class.
 */
static inline void
__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
              unsigned long delta_exec)
{
        unsigned long delta_exec_weighted;

        schedstat_set(curr->statistics.exec_max,
                      max((u64)delta_exec, curr->statistics.exec_max));

        curr->sum_exec_runtime += delta_exec;
        schedstat_add(cfs_rq, exec_clock, delta_exec);
        delta_exec_weighted = calc_delta_fair(delta_exec, curr);

        curr->vruntime += delta_exec_weighted;
        update_min_vruntime(cfs_rq);
}

static void update_curr(struct cfs_rq *cfs_rq)
{
        struct sched_entity *curr = cfs_rq->curr;
        u64 now = rq_clock_task(rq_of(cfs_rq));
        unsigned long delta_exec;

        if (unlikely(!curr))
                return;

        /*
         * Get the amount of time the current task was running
         * since the last time we changed load (this cannot
         * overflow on 32 bits):
         */
        delta_exec = (unsigned long)(now - curr->exec_start);
        if (!delta_exec)
                return;

        __update_curr(cfs_rq, curr, delta_exec);
        curr->exec_start = now;

        if (entity_is_task(curr)) {
                struct task_struct *curtask = task_of(curr);

                trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
                cpuacct_charge(curtask, delta_exec);
                account_group_exec_runtime(curtask, delta_exec);
        }

        account_cfs_rq_runtime(cfs_rq, delta_exec);
}

static inline void
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
}

/*
 * Task is being enqueued - update stats:
 */
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        /*
         * Are we enqueueing a waiting task? (for current tasks
         * a dequeue/enqueue event is a NOP)
         */
        if (se != cfs_rq->curr)
                update_stats_wait_start(cfs_rq, se);
}

static void
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
                        rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
        schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
        schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
                        rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
#ifdef CONFIG_SCHEDSTATS
        if (entity_is_task(se)) {
                trace_sched_stat_wait(task_of(se),
                        rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
        }
#endif
        schedstat_set(se->statistics.wait_start, 0);
}

static inline void
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        /*
         * Mark the end of the wait period if dequeueing a
         * waiting task:
         */
        if (se != cfs_rq->curr)
                update_stats_wait_end(cfs_rq, se);
}

/*
 * We are picking a new current task - update its stats:
 */
static inline void
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        /*
         * We are starting a new run period:
         */
        se->exec_start = rq_clock_task(rq_of(cfs_rq));
}

/**************************************************
 * Scheduling class queueing methods:
 */

#ifdef CONFIG_NUMA_BALANCING
/*
 * numa task sample period in ms
 */
unsigned int sysctl_numa_balancing_scan_period_min = 100;
unsigned int sysctl_numa_balancing_scan_period_max = 100*50;
unsigned int sysctl_numa_balancing_scan_period_reset = 100*600;

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;

/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

static void task_numa_placement(struct task_struct *p)
{
        int seq;

        if (!p->mm)     /* for example, ksmd faulting in a user's mm */
                return;
        seq = ACCESS_ONCE(p->mm->numa_scan_seq);
        if (p->numa_scan_seq == seq)
                return;
        p->numa_scan_seq = seq;

        /* FIXME: Scheduling placement policy hints go here */
}

/*
 * Got a PROT_NONE fault for a page on @node.
 */
void task_numa_fault(int node, int pages, bool migrated)
{
        struct task_struct *p = current;

        if (!numabalancing_enabled)
                return;

        /* FIXME: Allocate task-specific structure for placement policy here */

        /*
         * If pages are properly placed (did not migrate) then scan slower.
         * This is reset periodically in case of phase changes
         */
        if (!migrated)
                p->numa_scan_period = min(sysctl_numa_balancing_scan_period_max,
                        p->numa_scan_period + jiffies_to_msecs(10));

        task_numa_placement(p);
}

static void reset_ptenuma_scan(struct task_struct *p)
{
        ACCESS_ONCE(p->mm->numa_scan_seq)++;
        p->mm->numa_scan_offset = 0;
}

/*
 * The expensive part of numa migration is done from task_work context.
 * Triggered from task_tick_numa().
 */
void task_numa_work(struct callback_head *work)
{
        unsigned long migrate, next_scan, now = jiffies;
        struct task_struct *p = current;
        struct mm_struct *mm = p->mm;
        struct vm_area_struct *vma;
        unsigned long start, end;
        long pages;

        WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));

        work->next = work; /* protect against double add */
        /*
         * Who cares about NUMA placement when they're dying.
         *
         * NOTE: make sure not to dereference p->mm before this check,
         * exit_task_work() happens _after_ exit_mm() so we could be called
         * without p->mm even though we still had it when we enqueued this
         * work.
         */
        if (p->flags & PF_EXITING)
                return;

        /*
         * We do not care about task placement until a task runs on a node
         * other than the first one used by the address space. This is
         * largely because migrations are driven by what CPU the task
         * is running on. If it's never scheduled on another node, it'll
         * not migrate so why bother trapping the fault.
         */
        if (mm->first_nid == NUMA_PTE_SCAN_INIT)
                mm->first_nid = numa_node_id();
        if (mm->first_nid != NUMA_PTE_SCAN_ACTIVE) {
                /* Are we running on a new node yet? */
                if (numa_node_id() == mm->first_nid &&
                    !sched_feat_numa(NUMA_FORCE))
                        return;

                mm->first_nid = NUMA_PTE_SCAN_ACTIVE;
        }

        /*
         * Reset the scan period if enough time has gone by. Objective is that
         * scanning will be reduced if pages are properly placed. As tasks
         * can enter different phases this needs to be re-examined. Lacking
         * proper tracking of reference behaviour, this blunt hammer is used.
         */
        migrate = mm->numa_next_reset;
        if (time_after(now, migrate)) {
                p->numa_scan_period = sysctl_numa_balancing_scan_period_min;
                next_scan = now + msecs_to_jiffies(sysctl_numa_balancing_scan_period_reset);
                xchg(&mm->numa_next_reset, next_scan);
        }

        /*
         * Enforce maximal scan/migration frequency..
         */
        migrate = mm->numa_next_scan;
        if (time_before(now, migrate))
                return;

        if (p->numa_scan_period == 0)
                p->numa_scan_period = sysctl_numa_balancing_scan_period_min;

        next_scan = now + msecs_to_jiffies(p->numa_scan_period);
        if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
                return;

        /*
         * Do not set pte_numa if the current running node is rate-limited.
         * This loses statistics on the fault but if we are unwilling to
         * migrate to this node, it is less likely we can do useful work
         */
        if (migrate_ratelimited(numa_node_id()))
                return;

        start = mm->numa_scan_offset;
        pages = sysctl_numa_balancing_scan_size;
        pages <<= 20 - PAGE_SHIFT; /* MB in pages */
        if (!pages)
                return;

        down_read(&mm->mmap_sem);
        vma = find_vma(mm, start);
        if (!vma) {
                reset_ptenuma_scan(p);
                start = 0;
                vma = mm->mmap;
        }
        for (; vma; vma = vma->vm_next) {
                if (!vma_migratable(vma))
                        continue;

                /* Skip small VMAs. They are not likely to be of relevance */
                if (vma->vm_end - vma->vm_start < HPAGE_SIZE)
                        continue;

                do {
                        start = max(start, vma->vm_start);
                        end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
                        end = min(end, vma->vm_end);
                        pages -= change_prot_numa(vma, start, end);

                        start = end;
                        if (pages <= 0)
                                goto out;
                } while (end != vma->vm_end);
        }

out:
        /*
         * It is possible to reach the end of the VMA list but the last few VMAs are
         * not guaranteed to the vma_migratable. If they are not, we would find the
         * !migratable VMA on the next scan but not reset the scanner to the start
         * so check it now.
         */
        if (vma)
                mm->numa_scan_offset = start;
        else
                reset_ptenuma_scan(p);
        up_read(&mm->mmap_sem);

}

/*
 * Drive the periodic memory faults..
 */
void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
        struct callback_head *work = &curr->numa_work;
        u64 period, now;

        /*
         * We don't care about NUMA placement if we don't have memory.
         */
        if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
                return;

        /*
         * Using runtime rather than walltime has the dual advantage that
         * we (mostly) drive the selection from busy threads and that the
         * task needs to have done some actual work before we bother with
         * NUMA placement.
         */
        now = curr->se.sum_exec_runtime;
        period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;

        if (now - curr->node_stamp > period) {
                if (!curr->node_stamp)
                        curr->numa_scan_period = sysctl_numa_balancing_scan_period_min;
                curr->node_stamp = now;

                if (!time_before(jiffies, curr->mm->numa_next_scan)) {
                        init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
                        task_work_add(curr, work, true);
                }
        }
}
#else
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
}
#endif /* CONFIG_NUMA_BALANCING */

static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        update_load_add(&cfs_rq->load, se->load.weight);
        if (!parent_entity(se))
                update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
#ifdef CONFIG_SMP
        if (entity_is_task(se))
                list_add(&se->group_node, &rq_of(cfs_rq)->cfs_tasks);
#endif
        cfs_rq->nr_running++;
}

static void
account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        update_load_sub(&cfs_rq->load, se->load.weight);
        if (!parent_entity(se))
                update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
        if (entity_is_task(se))
                list_del_init(&se->group_node);
        cfs_rq->nr_running--;
}

#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
{
        long tg_weight;

        /*
         * Use this CPU's actual weight instead of the last load_contribution
         * to gain a more accurate current total weight. See
         * update_cfs_rq_load_contribution().
         */
        tg_weight = atomic_long_read(&tg->load_avg);
        tg_weight -= cfs_rq->tg_load_contrib;
        tg_weight += cfs_rq->load.weight;

        return tg_weight;
}

static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
{
        long tg_weight, load, shares;

        tg_weight = calc_tg_weight(tg, cfs_rq);
        load = cfs_rq->load.weight;

        shares = (tg->shares * load);
        if (tg_weight)
                shares /= tg_weight;

        if (shares < MIN_SHARES)
                shares = MIN_SHARES;
        if (shares > tg->shares)
                shares = tg->shares;

        return shares;
}
# else /* CONFIG_SMP */
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
{
        return tg->shares;
}
# endif /* CONFIG_SMP */
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
                            unsigned long weight)
{
        if (se->on_rq) {
                /* commit outstanding execution time */
                if (cfs_rq->curr == se)
                        update_curr(cfs_rq);
                account_entity_dequeue(cfs_rq, se);
        }

        update_load_set(&se->load, weight);

        if (se->on_rq)
                account_entity_enqueue(cfs_rq, se);
}

static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

static void update_cfs_shares(struct cfs_rq *cfs_rq)
{
        struct task_group *tg;
        struct sched_entity *se;
        long shares;

        tg = cfs_rq->tg;
        se = tg->se[cpu_of(rq_of(cfs_rq))];
        if (!se || throttled_hierarchy(cfs_rq))
                return;
#ifndef CONFIG_SMP
        if (likely(se->load.weight == tg->shares))
                return;
#endif
        shares = calc_cfs_shares(cfs_rq, tg);

        reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

#ifdef CONFIG_SMP
/*
 * We choose a half-life close to 1 scheduling period.
 * Note: The tables below are dependent on this value.
 */
#define LOAD_AVG_PERIOD 32
#define LOAD_AVG_MAX 47742 /* maximum possible load avg */
#define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */

/* Precomputed fixed inverse multiplies for multiplication by y^n */
static const u32 runnable_avg_yN_inv[] = {
        0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
        0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
        0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
        0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
        0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
        0x85aac367, 0x82cd8698,
};

/*
 * Precomputed \Sum y^k { 1<=k<=n }.  These are floor(true_value) to prevent
 * over-estimates when re-combining.
 */
static const u32 runnable_avg_yN_sum[] = {
            0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
         9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
        17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
};

/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
        unsigned int local_n;

        if (!n)
                return val;
        else if (unlikely(n > LOAD_AVG_PERIOD * 63))
                return 0;

        /* after bounds checking we can collapse to 32-bit */
        local_n = n;

        /*
         * As y^PERIOD = 1/2, we can combine
         *    y^n = 1/2^(n/PERIOD) * k^(n%PERIOD)
         * With a look-up table which covers k^n (n<PERIOD)
         *
         * To achieve constant time decay_load.
         */
        if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
                val >>= local_n / LOAD_AVG_PERIOD;
                local_n %= LOAD_AVG_PERIOD;
        }

        val *= runnable_avg_yN_inv[local_n];
        /* We don't use SRR here since we always want to round down. */
        return val >> 32;
}

/*
 * For updates fully spanning n periods, the contribution to runnable
 * average will be: \Sum 1024*y^n
 *
 * We can compute this reasonably efficiently by combining:
 *   y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for  n <PERIOD}
 */
static u32 __compute_runnable_contrib(u64 n)
{
        u32 contrib = 0;

        if (likely(n <= LOAD_AVG_PERIOD))
                return runnable_avg_yN_sum[n];
        else if (unlikely(n >= LOAD_AVG_MAX_N))
                return LOAD_AVG_MAX;

        /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
        do {
                contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
                contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];

                n -= LOAD_AVG_PERIOD;
        } while (n > LOAD_AVG_PERIOD);

        contrib = decay_load(contrib, n);
        return contrib + runnable_avg_yN_sum[n];
}

/*
 * We can represent the historical contribution to runnable average as the
 * coefficients of a geometric series.  To do this we sub-divide our runnable
 * history into segments of approximately 1ms (1024us); label the segment that
 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
 *
 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
 *      p0            p1           p2
 *     (now)       (~1ms ago)  (~2ms ago)
 *
 * Let u_i denote the fraction of p_i that the entity was runnable.
 *
 * We then designate the fractions u_i as our co-efficients, yielding the
 * following representation of historical load:
 *   u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
 *
 * We choose y based on the with of a reasonably scheduling period, fixing:
 *   y^32 = 0.5
 *
 * This means that the contribution to load ~32ms ago (u_32) will be weighted
 * approximately half as much as the contribution to load within the last ms
 * (u_0).
 *
 * When a period "rolls over" and we have new u_0`, multiplying the previous
 * sum again by y is sufficient to update:
 *   load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
 *            = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
 */
static __always_inline int __update_entity_runnable_avg(u64 now,
                                                        struct sched_avg *sa,
                                                        int runnable)
{
        u64 delta, periods;
        u32 runnable_contrib;
        int delta_w, decayed = 0;

        delta = now - sa->last_runnable_update;
        /*
         * This should only happen when time goes backwards, which it
         * unfortunately does during sched clock init when we swap over to TSC.
         */
        if ((s64)delta < 0) {
                sa->last_runnable_update = now;
                return 0;
        }

        /*
         * Use 1024ns as the unit of measurement since it's a reasonable
         * approximation of 1us and fast to compute.
         */
        delta >>= 10;
        if (!delta)
                return 0;
        sa->last_runnable_update = now;

        /* delta_w is the amount already accumulated against our next period */
        delta_w = sa->runnable_avg_period % 1024;
        if (delta + delta_w >= 1024) {
                /* period roll-over */
                decayed = 1;

                /*
                 * Now that we know we're crossing a period boundary, figure
                 * out how much from delta we need to complete the current
                 * period and accrue it.
                 */
                delta_w = 1024 - delta_w;
                if (runnable)
                        sa->runnable_avg_sum += delta_w;
                sa->runnable_avg_period += delta_w;

                delta -= delta_w;

                /* Figure out how many additional periods this update spans */
                periods = delta / 1024;
                delta %= 1024;

                sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum,
                                                  periods + 1);
                sa->runnable_avg_period = decay_load(sa->runnable_avg_period,
                                                     periods + 1);

                /* Efficiently calculate \sum (1..n_period) 1024*y^i */
                runnable_contrib = __compute_runnable_contrib(periods);
                if (runnable)
                        sa->runnable_avg_sum += runnable_contrib;
                sa->runnable_avg_period += runnable_contrib;
        }

        /* Remainder of delta accrued against u_0` */
        if (runnable)
                sa->runnable_avg_sum += delta;
        sa->runnable_avg_period += delta;

        return decayed;
}

/* Synchronize an entity's decay with its parenting cfs_rq.*/
static inline u64 __synchronize_entity_decay(struct sched_entity *se)
{
        struct cfs_rq *cfs_rq = cfs_rq_of(se);
        u64 decays = atomic64_read(&cfs_rq->decay_counter);

        decays -= se->avg.decay_count;
        if (!decays)
                return 0;

        se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
        se->avg.decay_count = 0;

        return decays;
}

#ifdef CONFIG_FAIR_GROUP_SCHED
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
                                                 int force_update)
{
        struct task_group *tg = cfs_rq->tg;
        long tg_contrib;

        tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg;
        tg_contrib -= cfs_rq->tg_load_contrib;

        if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) {
                atomic_long_add(tg_contrib, &tg->load_avg);
                cfs_rq->tg_load_contrib += tg_contrib;
        }
}

/*
 * Aggregate cfs_rq runnable averages into an equivalent task_group
 * representation for computing load contributions.
 */
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
                                                  struct cfs_rq *cfs_rq)
{
        struct task_group *tg = cfs_rq->tg;
        long contrib;

        /* The fraction of a cpu used by this cfs_rq */
        contrib = div_u64(sa->runnable_avg_sum << NICE_0_SHIFT,
                          sa->runnable_avg_period + 1);
        contrib -= cfs_rq->tg_runnable_contrib;

        if (abs(contrib) > cfs_rq->tg_runnable_contrib / 64) {
                atomic_add(contrib, &tg->runnable_avg);
                cfs_rq->tg_runnable_contrib += contrib;
        }
}

static inline void __update_group_entity_contrib(struct sched_entity *se)
{
        struct cfs_rq *cfs_rq = group_cfs_rq(se);
        struct task_group *tg = cfs_rq->tg;
        int runnable_avg;

        u64 contrib;

        contrib = cfs_rq->tg_load_contrib * tg->shares;
        se->avg.load_avg_contrib = div_u64(contrib,
                                     atomic_long_read(&tg->load_avg) + 1);

        /*
         * For group entities we need to compute a correction term in the case
         * that they are consuming <1 cpu so that we would contribute the same
         * load as a task of equal weight.
         *
         * Explicitly co-ordinating this measurement would be expensive, but
         * fortunately the sum of each cpus contribution forms a usable
         * lower-bound on the true value.
         *
         * Consider the aggregate of 2 contributions.  Either they are disjoint
         * (and the sum represents true value) or they are disjoint and we are
         * understating by the aggregate of their overlap.
         *
         * Extending this to N cpus, for a given overlap, the maximum amount we
         * understand is then n_i(n_i+1)/2 * w_i where n_i is the number of
         * cpus that overlap for this interval and w_i is the interval width.
         *
         * On a small machine; the first term is well-bounded which bounds the
         * total error since w_i is a subset of the period.  Whereas on a
         * larger machine, while this first term can be larger, if w_i is the
         * of consequential size guaranteed to see n_i*w_i quickly converge to
         * our upper bound of 1-cpu.
         */
        runnable_avg = atomic_read(&tg->runnable_avg);
        if (runnable_avg < NICE_0_LOAD) {
                se->avg.load_avg_contrib *= runnable_avg;
                se->avg.load_avg_contrib >>= NICE_0_SHIFT;
        }
}
#else
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
                                                 int force_update) {}
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
                                                  struct cfs_rq *cfs_rq) {}
static inline void __update_group_entity_contrib(struct sched_entity *se) {}
#endif

static inline void __update_task_entity_contrib(struct sched_entity *se)
{
        u32 contrib;

        /* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
        contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight);
        contrib /= (se->avg.runnable_avg_period + 1);
        se->avg.load_avg_contrib = scale_load(contrib);
}

/* Compute the current contribution to load_avg by se, return any delta */
static long __update_entity_load_avg_contrib(struct sched_entity *se)
{
        long old_contrib = se->avg.load_avg_contrib;

        if (entity_is_task(se)) {
                __update_task_entity_contrib(se);
        } else {
                __update_tg_runnable_avg(&se->avg, group_cfs_rq(se));
                __update_group_entity_contrib(se);
        }

        return se->avg.load_avg_contrib - old_contrib;
}

static inline void subtract_blocked_load_contrib(struct cfs_rq *cfs_rq,
                                                 long load_contrib)
{
        if (likely(load_contrib < cfs_rq->blocked_load_avg))
                cfs_rq->blocked_load_avg -= load_contrib;
        else
                cfs_rq->blocked_load_avg = 0;
}

static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);

/* Update a sched_entity's runnable average */
static inline void update_entity_load_avg(struct sched_entity *se,
                                          int update_cfs_rq)
{
        struct cfs_rq *cfs_rq = cfs_rq_of(se);
        long contrib_delta;
        u64 now;

        /*
         * For a group entity we need to use their owned cfs_rq_clock_task() in
         * case they are the parent of a throttled hierarchy.
         */
        if (entity_is_task(se))
                now = cfs_rq_clock_task(cfs_rq);
        else
                now = cfs_rq_clock_task(group_cfs_rq(se));

        if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq))
                return;

        contrib_delta = __update_entity_load_avg_contrib(se);

        if (!update_cfs_rq)
                return;

        if (se->on_rq)
                cfs_rq->runnable_load_avg += contrib_delta;
        else
                subtract_blocked_load_contrib(cfs_rq, -contrib_delta);
}

/*
 * Decay the load contributed by all blocked children and account this so that
 * their contribution may appropriately discounted when they wake up.
 */
static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
{
        u64 now = cfs_rq_clock_task(cfs_rq) >> 20;
        u64 decays;

        decays = now - cfs_rq->last_decay;
        if (!decays && !force_update)
                return;

        if (atomic_long_read(&cfs_rq->removed_load)) {
                unsigned long removed_load;
                removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0);
                subtract_blocked_load_contrib(cfs_rq, removed_load);
        }

        if (decays) {
                cfs_rq->blocked_load_avg = decay_load(cfs_rq->blocked_load_avg,
                                                      decays);
                atomic64_add(decays, &cfs_rq->decay_counter);
                cfs_rq->last_decay = now;
        }

        __update_cfs_rq_tg_load_contrib(cfs_rq, force_update);
}

static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
{
        __update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable);
        __update_tg_runnable_avg(&rq->avg, &rq->cfs);
}

/* Add the load generated by se into cfs_rq's child load-average */
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
                                                  struct sched_entity *se,
                                                  int wakeup)
{
        /*
         * We track migrations using entity decay_count <= 0, on a wake-up
         * migration we use a negative decay count to track the remote decays
         * accumulated while sleeping.
         *
         * Newly forked tasks are enqueued with se->avg.decay_count == 0, they
         * are seen by enqueue_entity_load_avg() as a migration with an already
         * constructed load_avg_contrib.
         */
        if (unlikely(se->avg.decay_count <= 0)) {
                se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq));
                if (se->avg.decay_count) {
                        /*
                         * In a wake-up migration we have to approximate the
                         * time sleeping.  This is because we can't synchronize
                         * clock_task between the two cpus, and it is not
                         * guaranteed to be read-safe.  Instead, we can
                         * approximate this using our carried decays, which are
                         * explicitly atomically readable.
                         */
                        se->avg.last_runnable_update -= (-se->avg.decay_count)
                                                        << 20;
                        update_entity_load_avg(se, 0);
                        /* Indicate that we're now synchronized and on-rq */
                        se->avg.decay_count = 0;
                }
                wakeup = 0;
        } else {
                /*
                 * Task re-woke on same cpu (or else migrate_task_rq_fair()
                 * would have made count negative); we must be careful to avoid
                 * double-accounting blocked time after synchronizing decays.
                 */
                se->avg.last_runnable_update += __synchronize_entity_decay(se)
                                                        << 20;
        }

        /* migrated tasks did not contribute to our blocked load */
        if (wakeup) {
                subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
                update_entity_load_avg(se, 0);
        }

        cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
        /* we force update consideration on load-balancer moves */
        update_cfs_rq_blocked_load(cfs_rq, !wakeup);
}

/*
 * Remove se's load from this cfs_rq child load-average, if the entity is
 * transitioning to a blocked state we track its projected decay using
 * blocked_load_avg.
 */
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
                                                  struct sched_entity *se,
                                                  int sleep)
{
        update_entity_load_avg(se, 1);
        /* we force update consideration on load-balancer moves */
        update_cfs_rq_blocked_load(cfs_rq, !sleep);

        cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
        if (sleep) {
                cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
                se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
        } /* migrations, e.g. sleep=0 leave decay_count == 0 */
}

/*
 * Update the rq's load with the elapsed running time before entering
 * idle. if the last scheduled task is not a CFS task, idle_enter will
 * be the only way to update the runnable statistic.
 */
void idle_enter_fair(struct rq *this_rq)
{
        update_rq_runnable_avg(this_rq, 1);
}

/*
 * Update the rq's load with the elapsed idle time before a task is
 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
 * be the only way to update the runnable statistic.
 */
void idle_exit_fair(struct rq *this_rq)
{
        update_rq_runnable_avg(this_rq, 0);
}

#else
static inline void update_entity_load_avg(struct sched_entity *se,
                                          int update_cfs_rq) {}
static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
                                           struct sched_entity *se,
                                           int wakeup) {}
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
                                           struct sched_entity *se,
                                           int sleep) {}
static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
                                              int force_update) {}
#endif

static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
#ifdef CONFIG_SCHEDSTATS
        struct task_struct *tsk = NULL;

        if (entity_is_task(se))
                tsk = task_of(se);

        if (se->statistics.sleep_start) {
                u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;

                if ((s64)delta < 0)
                        delta = 0;

                if (unlikely(delta > se->statistics.sleep_max))
                        se->statistics.sleep_max = delta;

                se->statistics.sleep_start = 0;
                se->statistics.sum_sleep_runtime += delta;

                if (tsk) {
                        account_scheduler_latency(tsk, delta >> 10, 1);
                        trace_sched_stat_sleep(tsk, delta);
                }
        }
        if (se->statistics.block_start) {
                u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;

                if ((s64)delta < 0)
                        delta = 0;

                if (unlikely(delta > se->statistics.block_max))
                        se->statistics.block_max = delta;

                se->statistics.block_start = 0;
                se->statistics.sum_sleep_runtime += delta;

                if (tsk) {
                        if (tsk->in_iowait) {
                                se->statistics.iowait_sum += delta;
                                se->statistics.iowait_count++;
                                trace_sched_stat_iowait(tsk, delta);
                        }

                        trace_sched_stat_blocked(tsk, delta);

                        /*
                         * Blocking time is in units of nanosecs, so shift by
                         * 20 to get a milliseconds-range estimation of the
                         * amount of time that the task spent sleeping:
                         */
                        if (unlikely(prof_on == SLEEP_PROFILING)) {
                                profile_hits(SLEEP_PROFILING,
                                                (void *)get_wchan(tsk),
                                                delta >> 20);
                        }
                        account_scheduler_latency(tsk, delta >> 10, 0);
                }
        }
#endif
}

static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
#ifdef CONFIG_SCHED_DEBUG
        s64 d = se->vruntime - cfs_rq->min_vruntime;

        if (d < 0)
                d = -d;

        if (d > 3*sysctl_sched_latency)
                schedstat_inc(cfs_rq, nr_spread_over);
#endif
}

static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
        u64 vruntime = cfs_rq->min_vruntime;

        /*
         * The 'current' period is already promised to the current tasks,
         * however the extra weight of the new task will slow them down a
         * little, place the new task so that it fits in the slot that
         * stays open at the end.
         */
        if (initial && sched_feat(START_DEBIT))
                vruntime += sched_vslice(cfs_rq, se);

        /* sleeps up to a single latency don't count. */
        if (!initial) {
                unsigned long thresh = sysctl_sched_latency;

                /*
                 * Halve their sleep time's effect, to allow
                 * for a gentler effect of sleepers:
                 */
                if (sched_feat(GENTLE_FAIR_SLEEPERS))
                        thresh >>= 1;

                vruntime -= thresh;
        }

        /* ensure we never gain time by being placed backwards. */
        se->vruntime = max_vruntime(se->vruntime, vruntime);
}

static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

static void
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
        /*
         * Update the normalized vruntime before updating min_vruntime
         * through calling update_curr().
         */
        if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
                se->vruntime += cfs_rq->min_vruntime;

        /*
         * Update run-time statistics of the 'current'.
         */
        update_curr(cfs_rq);
        enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
        account_entity_enqueue(cfs_rq, se);
        update_cfs_shares(cfs_rq);

        if (flags & ENQUEUE_WAKEUP) {
                place_entity(cfs_rq, se, 0);
                enqueue_sleeper(cfs_rq, se);
        }

        update_stats_enqueue(cfs_rq, se);
        check_spread(cfs_rq, se);
        if (se != cfs_rq->curr)
                __enqueue_entity(cfs_rq, se);
        se->on_rq = 1;

        if (cfs_rq->nr_running == 1) {
                list_add_leaf_cfs_rq(cfs_rq);
                check_enqueue_throttle(cfs_rq);
        }
}

static void __clear_buddies_last(struct sched_entity *se)
{
        for_each_sched_entity(se) {
                struct cfs_rq *cfs_rq = cfs_rq_of(se);
                if (cfs_rq->last == se)
                        cfs_rq->last = NULL;
                else
                        break;
        }
}

static void __clear_buddies_next(struct sched_entity *se)
{
        for_each_sched_entity(se) {
                struct cfs_rq *cfs_rq = cfs_rq_of(se);
                if (cfs_rq->next == se)
                        cfs_rq->next = NULL;
                else
                        break;
        }
}

static void __clear_buddies_skip(struct sched_entity *se)
{
        for_each_sched_entity(se) {
                struct cfs_rq *cfs_rq = cfs_rq_of(se);
                if (cfs_rq->skip == se)
                        cfs_rq->skip = NULL;
                else
                        break;
        }
}

static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        if (cfs_rq->last == se)
                __clear_buddies_last(se);

        if (cfs_rq->next == se)
                __clear_buddies_next(se);

        if (cfs_rq->skip == se)
                __clear_buddies_skip(se);
}

static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);

static void
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
        /*
         * Update run-time statistics of the 'current'.
         */
        update_curr(cfs_rq);
        dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);

        update_stats_dequeue(cfs_rq, se);
        if (flags & DEQUEUE_SLEEP) {
#ifdef CONFIG_SCHEDSTATS
                if (entity_is_task(se)) {
                        struct task_struct *tsk = task_of(se);

                        if (tsk->state & TASK_INTERRUPTIBLE)
                                se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
                        if (tsk->state & TASK_UNINTERRUPTIBLE)
                                se->statistics.block_start = rq_clock(rq_of(cfs_rq));
                }
#endif
        }

        clear_buddies(cfs_rq, se);

        if (se != cfs_rq->curr)
                __dequeue_entity(cfs_rq, se);
        se->on_rq = 0;
        account_entity_dequeue(cfs_rq, se);

        /*
         * Normalize the entity after updating the min_vruntime because the
         * update can refer to the ->curr item and we need to reflect this
         * movement in our normalized position.
         */
        if (!(flags & DEQUEUE_SLEEP))
                se->vruntime -= cfs_rq->min_vruntime;

        /* return excess runtime on last dequeue */
        return_cfs_rq_runtime(cfs_rq);

        update_min_vruntime(cfs_rq);
        update_cfs_shares(cfs_rq);
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
static void
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
{
        unsigned long ideal_runtime, delta_exec;
        struct sched_entity *se;
        s64 delta;

        ideal_runtime = sched_slice(cfs_rq, curr);
        delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
        if (delta_exec > ideal_runtime) {
                resched_task(rq_of(cfs_rq)->curr);
                /*
                 * The current task ran long enough, ensure it doesn't get
                 * re-elected due to buddy favours.
                 */
                clear_buddies(cfs_rq, curr);
                return;
        }

        /*
         * Ensure that a task that missed wakeup preemption by a
         * narrow margin doesn't have to wait for a full slice.
         * This also mitigates buddy induced latencies under load.
         */
        if (delta_exec < sysctl_sched_min_granularity)
                return;

        se = __pick_first_entity(cfs_rq);
        delta = curr->vruntime - se->vruntime;

        if (delta < 0)
                return;

        if (delta > ideal_runtime)
                resched_task(rq_of(cfs_rq)->curr);
}

static void
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        /* 'current' is not kept within the tree. */
        if (se->on_rq) {
                /*
                 * Any task has to be enqueued before it get to execute on
                 * a CPU. So account for the time it spent waiting on the
                 * runqueue.
                 */
                update_stats_wait_end(cfs_rq, se);
                __dequeue_entity(cfs_rq, se);
        }

        update_stats_curr_start(cfs_rq, se);
        cfs_rq->curr = se;
#ifdef CONFIG_SCHEDSTATS
        /*
         * Track our maximum slice length, if the CPU's load is at
         * least twice that of our own weight (i.e. dont track it
         * when there are only lesser-weight tasks around):
         */
        if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
                se->statistics.slice_max = max(se->statistics.slice_max,
                        se->sum_exec_runtime - se->prev_sum_exec_runtime);
        }
#endif
        se->prev_sum_exec_runtime = se->sum_exec_runtime;
}

static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

/*
 * Pick the next process, keeping these things in mind, in this order:
 * 1) keep things fair between processes/task groups
 * 2) pick the "next" process, since someone really wants that to run
 * 3) pick the "last" process, for cache locality
 * 4) do not run the "skip" process, if something else is available
 */
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
{
        struct sched_entity *se = __pick_first_entity(cfs_rq);
        struct sched_entity *left = se;

        /*
         * Avoid running the skip buddy, if running something else can
         * be done without getting too unfair.
         */
        if (cfs_rq->skip == se) {
                struct sched_entity *second = __pick_next_entity(se);
                if (second && wakeup_preempt_entity(second, left) < 1)
                        se = second;
        }

        /*
         * Prefer last buddy, try to return the CPU to a preempted task.
         */
        if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
                se = cfs_rq->last;

        /*
         * Someone really wants this to run. If it's not unfair, run it.
         */
        if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
                se = cfs_rq->next;

        clear_buddies(cfs_rq, se);

        return se;
}

static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq);

static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
{

        /*
         * If still on the runqueue then deactivate_task()
         * was not called and update_curr() has to be done:
         */
        if (prev->on_rq)
                update_curr(cfs_rq);

        /* throttle cfs_rqs exceeding runtime */
        check_cfs_rq_runtime(cfs_rq);

        check_spread(cfs_rq, prev);
        if (prev->on_rq) {
                update_stats_wait_start(cfs_rq, prev);
                /* Put 'current' back into the tree. */
                __enqueue_entity(cfs_rq, prev);
                /* in !on_rq case, update occurred at dequeue */
                update_entity_load_avg(prev, 1);
        }
        cfs_rq->curr = NULL;
}

static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
{
        /*
         * Update run-time statistics of the 'current'.
         */
        update_curr(cfs_rq);

        /*
         * Ensure that runnable average is periodically updated.
         */
        update_entity_load_avg(curr, 1);
        update_cfs_rq_blocked_load(cfs_rq, 1);
        update_cfs_shares(cfs_rq);

#ifdef CONFIG_SCHED_HRTICK
        /*
         * queued ticks are scheduled to match the slice, so don't bother
         * validating it and just reschedule.
         */
        if (queued) {
                resched_task(rq_of(cfs_rq)->curr);
                return;
        }
        /*
         * don't let the period tick interfere with the hrtick preemption
         */
        if (!sched_feat(DOUBLE_TICK) &&
                        hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
                return;
#endif

        if (cfs_rq->nr_running > 1)
                check_preempt_tick(cfs_rq, curr);
}


/**************************************************
 * CFS bandwidth control machinery
 */

#ifdef CONFIG_CFS_BANDWIDTH

#ifdef HAVE_JUMP_LABEL
static struct static_key __cfs_bandwidth_used;

static inline bool cfs_bandwidth_used(void)
{
        return static_key_false(&__cfs_bandwidth_used);
}

void account_cfs_bandwidth_used(int enabled, int was_enabled)
{
        /* only need to count groups transitioning between enabled/!enabled */
        if (enabled && !was_enabled)
                static_key_slow_inc(&__cfs_bandwidth_used);
        else if (!enabled && was_enabled)
                static_key_slow_dec(&__cfs_bandwidth_used);
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
        return true;
}

void account_cfs_bandwidth_used(int enabled, int was_enabled) {}
#endif /* HAVE_JUMP_LABEL */

/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
        return 100000000ULL;
}

static inline u64 sched_cfs_bandwidth_slice(void)
{
        return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
}

/*
 * Replenish runtime according to assigned quota and update expiration time.
 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
 * additional synchronization around rq->lock.
 *
 * requires cfs_b->lock
 */
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
{
        u64 now;

        if (cfs_b->quota == RUNTIME_INF)
                return;

        now = sched_clock_cpu(smp_processor_id());
        cfs_b->runtime = cfs_b->quota;
        cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
}

static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
        return &tg->cfs_bandwidth;
}

/* rq->task_clock normalized against any time this cfs_rq has spent throttled */
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
        if (unlikely(cfs_rq->throttle_count))
                return cfs_rq->throttled_clock_task;

        return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
}

/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
        struct task_group *tg = cfs_rq->tg;
        struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
        u64 amount = 0, min_amount, expires;

        /* note: this is a positive sum as runtime_remaining <= 0 */
        min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;

        raw_spin_lock(&cfs_b->lock);
        if (cfs_b->quota == RUNTIME_INF)
                amount = min_amount;
        else {
                /*
                 * If the bandwidth pool has become inactive, then at least one
                 * period must have elapsed since the last consumption.
                 * Refresh the global state and ensure bandwidth timer becomes
                 * active.
                 */
                if (!cfs_b->timer_active) {
                        __refill_cfs_bandwidth_runtime(cfs_b);
                        __start_cfs_bandwidth(cfs_b);
                }

                if (cfs_b->runtime > 0) {
                        amount = min(cfs_b->runtime, min_amount);
                        cfs_b->runtime -= amount;
                        cfs_b->idle = 0;
                }
        }
        expires = cfs_b->runtime_expires;
        raw_spin_unlock(&cfs_b->lock);

        cfs_rq->runtime_remaining += amount;
        /*
         * we may have advanced our local expiration to account for allowed
         * spread between our sched_clock and the one on which runtime was
         * issued.
         */
        if ((s64)(expires - cfs_rq->runtime_expires) > 0)
                cfs_rq->runtime_expires = expires;

        return cfs_rq->runtime_remaining > 0;
}

/*
 * Note: This depends on the synchronization provided by sched_clock and the
 * fact that rq->clock snapshots this value.
 */
static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
        struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

        /* if the deadline is ahead of our clock, nothing to do */
        if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
                return;

        if (cfs_rq->runtime_remaining < 0)
                return;

        /*
         * If the local deadline has passed we have to consider the
         * possibility that our sched_clock is 'fast' and the global deadline
         * has not truly expired.
         *
         * Fortunately we can check determine whether this the case by checking
         * whether the global deadline has advanced.
         */

        if ((s64)(cfs_rq->runtime_expires - cfs_b->runtime_expires) >= 0) {
                /* extend local deadline, drift is bounded above by 2 ticks */
                cfs_rq->runtime_expires += TICK_NSEC;
        } else {
                /* global deadline is ahead, expiration has passed */
                cfs_rq->runtime_remaining = 0;
        }
}

static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
                                     unsigned long delta_exec)
{
        /* dock delta_exec before expiring quota (as it could span periods) */
        cfs_rq->runtime_remaining -= delta_exec;
        expire_cfs_rq_runtime(cfs_rq);

        if (likely(cfs_rq->runtime_remaining > 0))
                return;

        /*
         * if we're unable to extend our runtime we resched so that the active
         * hierarchy can be throttled
         */
        if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
                resched_task(rq_of(cfs_rq)->curr);
}

static __always_inline
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec)
{
        if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
                return;

        __account_cfs_rq_runtime(cfs_rq, delta_exec);
}

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
        return cfs_bandwidth_used() && cfs_rq->throttled;
}

/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
        return cfs_bandwidth_used() && cfs_rq->throttle_count;
}

/*
 * Ensure that neither of the group entities corresponding to src_cpu or
 * dest_cpu are members of a throttled hierarchy when performing group
 * load-balance operations.
 */
static inline int throttled_lb_pair(struct task_group *tg,
                                    int src_cpu, int dest_cpu)
{
        struct cfs_rq *src_cfs_rq, *dest_cfs_rq;

        src_cfs_rq = tg->cfs_rq[src_cpu];
        dest_cfs_rq = tg->cfs_rq[dest_cpu];

        return throttled_hierarchy(src_cfs_rq) ||
               throttled_hierarchy(dest_cfs_rq);
}

/* updated child weight may affect parent so we have to do this bottom up */
static int tg_unthrottle_up(struct task_group *tg, void *data)
{
        struct rq *rq = data;
        struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];

        cfs_rq->throttle_count--;
#ifdef CONFIG_SMP
        if (!cfs_rq->throttle_count) {
                /* adjust cfs_rq_clock_task() */
                cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
                                             cfs_rq->throttled_clock_task;
        }
#endif

        return 0;
}

static int tg_throttle_down(struct task_group *tg, void *data)
{
        struct rq *rq = data;
        struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];

        /* group is entering throttled state, stop time */
        if (!cfs_rq->throttle_count)
                cfs_rq->throttled_clock_task = rq_clock_task(rq);
        cfs_rq->throttle_count++;

        return 0;
}

static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
{
        struct rq *rq = rq_of(cfs_rq);
        struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
        struct sched_entity *se;
        long task_delta, dequeue = 1;

        se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];

        /* freeze hierarchy runnable averages while throttled */
        rcu_read_lock();
        walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
        rcu_read_unlock();

        task_delta = cfs_rq->h_nr_running;
        for_each_sched_entity(se) {
                struct cfs_rq *qcfs_rq = cfs_rq_of(se);
                /* throttled entity or throttle-on-deactivate */
                if (!se->on_rq)
                        break;

                if (dequeue)
                        dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
                qcfs_rq->h_nr_running -= task_delta;

                if (qcfs_rq->load.weight)
                        dequeue = 0;
        }

        if (!se)
                rq->nr_running -= task_delta;

        cfs_rq->throttled = 1;
        cfs_rq->throttled_clock = rq_clock(rq);
        raw_spin_lock(&cfs_b->lock);
        list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
        raw_spin_unlock(&cfs_b->lock);
}

void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
{
        struct rq *rq = rq_of(cfs_rq);
        struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
        struct sched_entity *se;
        int enqueue = 1;
        long task_delta;

        se = cfs_rq->tg->se[cpu_of(rq)];

        cfs_rq->throttled = 0;

        update_rq_clock(rq);

        raw_spin_lock(&cfs_b->lock);
        cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
        list_del_rcu(&cfs_rq->throttled_list);
        raw_spin_unlock(&cfs_b->lock);

        /* update hierarchical throttle state */
        walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

        if (!cfs_rq->load.weight)
                return;

        task_delta = cfs_rq->h_nr_running;
        for_each_sched_entity(se) {
                if (se->on_rq)
                        enqueue = 0;

                cfs_rq = cfs_rq_of(se);
                if (enqueue)
                        enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
                cfs_rq->h_nr_running += task_delta;

                if (cfs_rq_throttled(cfs_rq))
                        break;
        }

        if (!se)
                rq->nr_running += task_delta;

        /* determine whether we need to wake up potentially idle cpu */
        if (rq->curr == rq->idle && rq->cfs.nr_running)
                resched_task(rq->curr);
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
                u64 remaining, u64 expires)
{
        struct cfs_rq *cfs_rq;
        u64 runtime = remaining;

        rcu_read_lock();
        list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
                                throttled_list) {
                struct rq *rq = rq_of(cfs_rq);

                raw_spin_lock(&rq->lock);
                if (!cfs_rq_throttled(cfs_rq))
                        goto next;

                runtime = -cfs_rq->runtime_remaining + 1;
                if (runtime > remaining)
                        runtime = remaining;
                remaining -= runtime;

                cfs_rq->runtime_remaining += runtime;
                cfs_rq->runtime_expires = expires;

                /* we check whether we're throttled above */
                if (cfs_rq->runtime_remaining > 0)
                        unthrottle_cfs_rq(cfs_rq);

next:
                raw_spin_unlock(&rq->lock);

                if (!remaining)
                        break;
        }
        rcu_read_unlock();

        return remaining;
}

/*
 * Responsible for refilling a task_group's bandwidth and unthrottling its
 * cfs_rqs as appropriate. If there has been no activity within the last
 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
 * used to track this state.
 */
static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
{
        u64 runtime, runtime_expires;
        int idle = 1, throttled;

        raw_spin_lock(&cfs_b->lock);
        /* no need to continue the timer with no bandwidth constraint */
        if (cfs_b->quota == RUNTIME_INF)
                goto out_unlock;

        throttled = !list_empty(&cfs_b->throttled_cfs_rq);
        /* idle depends on !throttled (for the case of a large deficit) */
        idle = cfs_b->idle && !throttled;
        cfs_b->nr_periods += overrun;

        /* if we're going inactive then everything else can be deferred */
        if (idle)
                goto out_unlock;

        __refill_cfs_bandwidth_runtime(cfs_b);

        if (!throttled) {
                /* mark as potentially idle for the upcoming period */
                cfs_b->idle = 1;
                goto out_unlock;
        }

        /* account preceding periods in which throttling occurred */
        cfs_b->nr_throttled += overrun;

        /*
         * There are throttled entities so we must first use the new bandwidth
         * to unthrottle them before making it generally available.  This
         * ensures that all existing debts will be paid before a new cfs_rq is
         * allowed to run.
         */
        runtime = cfs_b->runtime;
        runtime_expires = cfs_b->runtime_expires;
        cfs_b->runtime = 0;

        /*
         * This check is repeated as we are holding onto the new bandwidth
         * while we unthrottle.  This can potentially race with an unthrottled
         * group trying to acquire new bandwidth from the global pool.
         */
        while (throttled && runtime > 0) {
                raw_spin_unlock(&cfs_b->lock);
                /* we can't nest cfs_b->lock while distributing bandwidth */
                runtime = distribute_cfs_runtime(cfs_b, runtime,
                                                 runtime_expires);
                raw_spin_lock(&cfs_b->lock);

                throttled = !list_empty(&cfs_b->throttled_cfs_rq);
        }

        /* return (any) remaining runtime */
        cfs_b->runtime = runtime;
        /*
         * While we are ensured activity in the period following an
         * unthrottle, this also covers the case in which the new bandwidth is
         * insufficient to cover the existing bandwidth deficit.  (Forcing the
         * timer to remain active while there are any throttled entities.)
         */
        cfs_b->idle = 0;
out_unlock:
        if (idle)
                cfs_b->timer_active = 0;
        raw_spin_unlock(&cfs_b->lock);

        return idle;
}

/* a cfs_rq won't donate quota below this amount */
static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
/* minimum remaining period time to redistribute slack quota */
static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
/* how long we wait to gather additional slack before distributing */
static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;

/* are we near the end of the current quota period? */
static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
{
        struct hrtimer *refresh_timer = &cfs_b->period_timer;
        u64 remaining;

        /* if the call-back is running a quota refresh is already occurring */
        if (hrtimer_callback_running(refresh_timer))
                return 1;

        /* is a quota refresh about to occur? */
        remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
        if (remaining < min_expire)
                return 1;

        return 0;
}

static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
{
        u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;

        /* if there's a quota refresh soon don't bother with slack */
        if (runtime_refresh_within(cfs_b, min_left))
                return;

        start_bandwidth_timer(&cfs_b->slack_timer,
                                ns_to_ktime(cfs_bandwidth_slack_period));
}

/* we know any runtime found here is valid as update_curr() precedes return */
static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
        struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
        s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;

        if (slack_runtime <= 0)
                return;

        raw_spin_lock(&cfs_b->lock);
        if (cfs_b->quota != RUNTIME_INF &&
            cfs_rq->runtime_expires == cfs_b->runtime_expires) {
                cfs_b->runtime += slack_runtime;

                /* we are under rq->lock, defer unthrottling using a timer */
                if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
                    !list_empty(&cfs_b->throttled_cfs_rq))
                        start_cfs_slack_bandwidth(cfs_b);
        }
        raw_spin_unlock(&cfs_b->lock);

        /* even if it's not valid for return we don't want to try again */
        cfs_rq->runtime_remaining -= slack_runtime;
}

static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
        if (!cfs_bandwidth_used())
                return;

        if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
                return;

        __return_cfs_rq_runtime(cfs_rq);
}

/*
 * This is done with a timer (instead of inline with bandwidth return) since
 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
 */
static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
{
        u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
        u64 expires;

        /* confirm we're still not at a refresh boundary */
        if (runtime_refresh_within(cfs_b, min_bandwidth_expiration))
                return;

        raw_spin_lock(&cfs_b->lock);
        if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
                runtime = cfs_b->runtime;
                cfs_b->runtime = 0;
        }
        expires = cfs_b->runtime_expires;
        raw_spin_unlock(&cfs_b->lock);

        if (!runtime)
                return;

        runtime = distribute_cfs_runtime(cfs_b, runtime, expires);

        raw_spin_lock(&cfs_b->lock);
        if (expires == cfs_b->runtime_expires)
                cfs_b->runtime = runtime;
        raw_spin_unlock(&cfs_b->lock);
}

/*
 * When a group wakes up we want to make sure that its quota is not already
 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
 * runtime as update_curr() throttling can not not trigger until it's on-rq.
 */
static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
{
        if (!cfs_bandwidth_used())
                return;

        /* an active group must be handled by the update_curr()->put() path */
        if (!cfs_rq->runtime_enabled || cfs_rq->curr)
                return;

        /* ensure the group is not already throttled */
        if (cfs_rq_throttled(cfs_rq))
                return;

        /* update runtime allocation */
        account_cfs_rq_runtime(cfs_rq, 0);
        if (cfs_rq->runtime_remaining <= 0)
                throttle_cfs_rq(cfs_rq);
}

/* conditionally throttle active cfs_rq's from put_prev_entity() */
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
        if (!cfs_bandwidth_used())
                return;

        if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
                return;

        /*
         * it's possible for a throttled entity to be forced into a running
         * state (e.g. set_curr_task), in this case we're finished.
         */
        if (cfs_rq_throttled(cfs_rq))
                return;

        throttle_cfs_rq(cfs_rq);
}

static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
{
        struct cfs_bandwidth *cfs_b =
                container_of(timer, struct cfs_bandwidth, slack_timer);
        do_sched_cfs_slack_timer(cfs_b);

        return HRTIMER_NORESTART;
}

static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
{
        struct cfs_bandwidth *cfs_b =
                container_of(timer, struct cfs_bandwidth, period_timer);
        ktime_t now;
        int overrun;
        int idle = 0;

        for (;;) {
                now = hrtimer_cb_get_time(timer);
                overrun = hrtimer_forward(timer, now, cfs_b->period);

                if (!overrun)
                        break;

                idle = do_sched_cfs_period_timer(cfs_b, overrun);
        }

        return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
}

void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
        raw_spin_lock_init(&cfs_b->lock);
        cfs_b->runtime = 0;
        cfs_b->quota = RUNTIME_INF;
        cfs_b->period = ns_to_ktime(default_cfs_period());

        INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
        hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
        cfs_b->period_timer.function = sched_cfs_period_timer;
        hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
        cfs_b->slack_timer.function = sched_cfs_slack_timer;
}

static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
        cfs_rq->runtime_enabled = 0;
        INIT_LIST_HEAD(&cfs_rq->throttled_list);
}

/* requires cfs_b->lock, may release to reprogram timer */
void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
        /*
         * The timer may be active because we're trying to set a new bandwidth
         * period or because we're racing with the tear-down path
         * (timer_active==0 becomes visible before the hrtimer call-back
         * terminates).  In either case we ensure that it's re-programmed
         */
        while (unlikely(hrtimer_active(&cfs_b->period_timer))) {
                raw_spin_unlock(&cfs_b->lock);
                /* ensure cfs_b->lock is available while we wait */
                hrtimer_cancel(&cfs_b->period_timer);

                raw_spin_lock(&cfs_b->lock);
                /* if someone else restarted the timer then we're done */
                if (cfs_b->timer_active)
                        return;
        }

        cfs_b->timer_active = 1;
        start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period);
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
        hrtimer_cancel(&cfs_b->period_timer);
        hrtimer_cancel(&cfs_b->slack_timer);
}

static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
{
        struct cfs_rq *cfs_rq;

        for_each_leaf_cfs_rq(rq, cfs_rq) {
                struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

                if (!cfs_rq->runtime_enabled)
                        continue;

                /*
                 * clock_task is not advancing so we just need to make sure
                 * there's some valid quota amount
                 */
                cfs_rq->runtime_remaining = cfs_b->quota;
                if (cfs_rq_throttled(cfs_rq))
                        unthrottle_cfs_rq(cfs_rq);
        }
}

#else /* CONFIG_CFS_BANDWIDTH */
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
        return rq_clock_task(rq_of(cfs_rq));
}

static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
                                     unsigned long delta_exec) {}
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
        return 0;
}

static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
        return 0;
}

static inline int throttled_lb_pair(struct task_group *tg,
                                    int src_cpu, int dest_cpu)
{
        return 0;
}

void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}

#ifdef CONFIG_FAIR_GROUP_SCHED
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
#endif

static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
        return NULL;
}
static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}

#endif /* CONFIG_CFS_BANDWIDTH */

/**************************************************
 * CFS operations on tasks:
 */

#ifdef CONFIG_SCHED_HRTICK
static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
        struct sched_entity *se = &p->se;
        struct cfs_rq *cfs_rq = cfs_rq_of(se);

        WARN_ON(task_rq(p) != rq);

        if (cfs_rq->nr_running > 1) {
                u64 slice = sched_slice(cfs_rq, se);
                u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
                s64 delta = slice - ran;

                if (delta < 0) {
                        if (rq->curr == p)
                                resched_task(p);
                        return;
                }

                /*
                 * Don't schedule slices shorter than 10000ns, that just
                 * doesn't make sense. Rely on vruntime for fairness.
                 */
                if (rq->curr != p)
                        delta = max_t(s64, 10000LL, delta);

                hrtick_start(rq, delta);
        }
}

/*
 * called from enqueue/dequeue and updates the hrtick when the
 * current task is from our class and nr_running is low enough
 * to matter.
 */
static void hrtick_update(struct rq *rq)
{
        struct task_struct *curr = rq->curr;

        if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
                return;

        if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
                hrtick_start_fair(rq, curr);
}
#else /* !CONFIG_SCHED_HRTICK */
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}

static inline void hrtick_update(struct rq *rq)
{
}
#endif

/*
 * The enqueue_task method is called before nr_running is
 * increased. Here we update the fair scheduling stats and
 * then put the task into the rbtree:
 */
static void
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
{
        struct cfs_rq *cfs_rq;
        struct sched_entity *se = &p->se;

        for_each_sched_entity(se) {
                if (se->on_rq)
                        break;
                cfs_rq = cfs_rq_of(se);
                enqueue_entity(cfs_rq, se, flags);

                /*
                 * end evaluation on encountering a throttled cfs_rq
                 *
                 * note: in the case of encountering a throttled cfs_rq we will
                 * post the final h_nr_running increment below.
                */
                if (cfs_rq_throttled(cfs_rq))
                        break;
                cfs_rq->h_nr_running++;

                flags = ENQUEUE_WAKEUP;
        }

        for_each_sched_entity(se) {
                cfs_rq = cfs_rq_of(se);
                cfs_rq->h_nr_running++;

                if (cfs_rq_throttled(cfs_rq))
                        break;

                update_cfs_shares(cfs_rq);
                update_entity_load_avg(se, 1);
        }

        if (!se) {
                update_rq_runnable_avg(rq, rq->nr_running);
                inc_nr_running(rq);
        }
        hrtick_update(rq);
}

static void set_next_buddy(struct sched_entity *se);

/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
{
        struct cfs_rq *cfs_rq;
        struct sched_entity *se = &p->se;
        int task_sleep = flags & DEQUEUE_SLEEP;

        for_each_sched_entity(se) {
                cfs_rq = cfs_rq_of(se);
                dequeue_entity(cfs_rq, se, flags);

                /*
                 * end evaluation on encountering a throttled cfs_rq
                 *
                 * note: in the case of encountering a throttled cfs_rq we will
                 * post the final h_nr_running decrement below.
                */
                if (cfs_rq_throttled(cfs_rq))
                        break;
                cfs_rq->h_nr_running--;

                /* Don't dequeue parent if it has other entities besides us */
                if (cfs_rq->load.weight) {
                        /*
                         * Bias pick_next to pick a task from this cfs_rq, as
                         * p is sleeping when it is within its sched_slice.
                         */
                        if (task_sleep && parent_entity(se))
                                set_next_buddy(parent_entity(se));

                        /* avoid re-evaluating load for this entity */
                        se = parent_entity(se);
                        break;
                }
                flags |= DEQUEUE_SLEEP;
        }

        for_each_sched_entity(se) {
                cfs_rq = cfs_rq_of(se);
                cfs_rq->h_nr_running--;

                if (cfs_rq_throttled(cfs_rq))
                        break;

                update_cfs_shares(cfs_rq);
                update_entity_load_avg(se, 1);
        }

        if (!se) {
                dec_nr_running(rq);
                update_rq_runnable_avg(rq, 1);
        }
        hrtick_update(rq);
}

#ifdef CONFIG_SMP
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
        return cpu_rq(cpu)->cfs.runnable_load_avg;
}

/*
 * Return a low guess at the load of a migration-source cpu weighted
 * according to the scheduling class and "nice" value.
 *
 * We want to under-estimate the load of migration sources, to
 * balance conservatively.
 */
static unsigned long source_load(int cpu, int type)
{
        struct rq *rq = cpu_rq(cpu);
        unsigned long total = weighted_cpuload(cpu);

        if (type == 0 || !sched_feat(LB_BIAS))
                return total;

        return min(rq->cpu_load[type-1], total);
}

/*
 * Return a high guess at the load of a migration-target cpu weighted
 * according to the scheduling class and "nice" value.
 */
static unsigned long target_load(int cpu, int type)
{
        struct rq *rq = cpu_rq(cpu);
        unsigned long total = weighted_cpuload(cpu);

        if (type == 0 || !sched_feat(LB_BIAS))
                return total;

        return max(rq->cpu_load[type-1], total);
}

static unsigned long power_of(int cpu)
{
        return cpu_rq(cpu)->cpu_power;
}

static unsigned long cpu_avg_load_per_task(int cpu)
{
        struct rq *rq = cpu_rq(cpu);
        unsigned long nr_running = ACCESS_ONCE(rq->nr_running);
        unsigned long load_avg = rq->cfs.runnable_load_avg;

        if (nr_running)
                return load_avg / nr_running;

        return 0;
}


static void task_waking_fair(struct task_struct *p)
{
        struct sched_entity *se = &p->se;
        struct cfs_rq *cfs_rq = cfs_rq_of(se);
        u64 min_vruntime;

#ifndef CONFIG_64BIT
        u64 min_vruntime_copy;

        do {
                min_vruntime_copy = cfs_rq->min_vruntime_copy;
                smp_rmb();
                min_vruntime = cfs_rq->min_vruntime;
        } while (min_vruntime != min_vruntime_copy);
#else
        min_vruntime = cfs_rq->min_vruntime;
#endif

        se->vruntime -= min_vruntime;
}

#ifdef CONFIG_FAIR_GROUP_SCHED
/*
 * effective_load() calculates the load change as seen from the root_task_group
 *
 * Adding load to a group doesn't make a group heavier, but can cause movement
 * of group shares between cpus. Assuming the shares were perfectly aligned one
 * can calculate the shift in shares.
 *
 * Calculate the effective load difference if @wl is added (subtracted) to @tg
 * on this @cpu and results in a total addition (subtraction) of @wg to the
 * total group weight.
 *
 * Given a runqueue weight distribution (rw_i) we can compute a shares
 * distribution (s_i) using:
 *
 *   s_i = rw_i / \Sum rw_j                                             (1)
 *
 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
 * shares distribution (s_i):
 *
 *   rw_i = {   2,   4,   1,   0 }
 *   s_i  = { 2/7, 4/7, 1/7,   0 }
 *
 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
 * task used to run on and the CPU the waker is running on), we need to
 * compute the effect of waking a task on either CPU and, in case of a sync
 * wakeup, compute the effect of the current task going to sleep.
 *
 * So for a change of @wl to the local @cpu with an overall group weight change
 * of @wl we can compute the new shares distribution (s'_i) using:
 *
 *   s'_i = (rw_i + @wl) / (@wg + \Sum rw_j)                            (2)
 *
 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
 * differences in waking a task to CPU 0. The additional task changes the
 * weight and shares distributions like:
 *
 *   rw'_i = {   3,   4,   1,   0 }
 *   s'_i  = { 3/8, 4/8, 1/8,   0 }
 *
 * We can then compute the difference in effective weight by using:
 *
 *   dw_i = S * (s'_i - s_i)                                            (3)
 *
 * Where 'S' is the group weight as seen by its parent.
 *
 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
 * 4/7) times the weight of the group.
 */
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
{
        struct sched_entity *se = tg->se[cpu];

        if (!tg->parent)        /* the trivial, non-cgroup case */
                return wl;

        for_each_sched_entity(se) {
                long w, W;

                tg = se->my_q->tg;

                /*
                 * W = @wg + \Sum rw_j
                 */
                W = wg + calc_tg_weight(tg, se->my_q);

                /*
                 * w = rw_i + @wl
                 */
                w = se->my_q->load.weight + wl;

                /*
                 * wl = S * s'_i; see (2)
                 */
                if (W > 0 && w < W)
                        wl = (w * tg->shares) / W;
                else
                        wl = tg->shares;

                /*
                 * Per the above, wl is the new se->load.weight value; since
                 * those are clipped to [MIN_SHARES, ...) do so now. See
                 * calc_cfs_shares().
                 */
                if (wl < MIN_SHARES)
                        wl = MIN_SHARES;

                /*
                 * wl = dw_i = S * (s'_i - s_i); see (3)
                 */
                wl -= se->load.weight;

                /*
                 * Recursively apply this logic to all parent groups to compute
                 * the final effective load change on the root group. Since
                 * only the @tg group gets extra weight, all parent groups can
                 * only redistribute existing shares. @wl is the shift in shares
                 * resulting from this level per the above.
                 */
                wg = 0;
        }

        return wl;
}
#else

static inline unsigned long effective_load(struct task_group *tg, int cpu,
                unsigned long wl, unsigned long wg)
{
        return wl;
}

#endif

static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
{
        s64 this_load, load;
        int idx, this_cpu, prev_cpu;
        unsigned long tl_per_task;
        struct task_group *tg;
        unsigned long weight;
        int balanced;

        idx       = sd->wake_idx;
        this_cpu  = smp_processor_id();
        prev_cpu  = task_cpu(p);
        load      = source_load(prev_cpu, idx);
        this_load = target_load(this_cpu, idx);

        /*
         * If sync wakeup then subtract the (maximum possible)
         * effect of the currently running task from the load
         * of the current CPU:
         */
        if (sync) {
                tg = task_group(current);
                weight = current->se.load.weight;

                this_load += effective_load(tg, this_cpu, -weight, -weight);
                load += effective_load(tg, prev_cpu, 0, -weight);
        }

        tg = task_group(p);
        weight = p->se.load.weight;

        /*
         * In low-load situations, where prev_cpu is idle and this_cpu is idle
         * due to the sync cause above having dropped this_load to 0, we'll
         * always have an imbalance, but there's really nothing you can do
         * about that, so that's good too.
         *
         * Otherwise check if either cpus are near enough in load to allow this
         * task to be woken on this_cpu.
         */
        if (this_load > 0) {
                s64 this_eff_load, prev_eff_load;

                this_eff_load = 100;
                this_eff_load *= power_of(prev_cpu);
                this_eff_load *= this_load +
                        effective_load(tg, this_cpu, weight, weight);

                prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
                prev_eff_load *= power_of(this_cpu);
                prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);

                balanced = this_eff_load <= prev_eff_load;
        } else
                balanced = true;

        /*
         * If the currently running task will sleep within
         * a reasonable amount of time then attract this newly
         * woken task:
         */
        if (sync && balanced)
                return 1;

        schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
        tl_per_task = cpu_avg_load_per_task(this_cpu);

        if (balanced ||
            (this_load <= load &&
             this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
                /*
                 * This domain has SD_WAKE_AFFINE and
                 * p is cache cold in this domain, and
                 * there is no bad imbalance.
                 */
                schedstat_inc(sd, ttwu_move_affine);
                schedstat_inc(p, se.statistics.nr_wakeups_affine);

                return 1;
        }
        return 0;
}

/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
                  int this_cpu, int load_idx)
{
        struct sched_group *idlest = NULL, *group = sd->groups;
        unsigned long min_load = ULONG_MAX, this_load = 0;
        int imbalance = 100 + (sd->imbalance_pct-100)/2;

        do {
                unsigned long load, avg_load;
                int local_group;
                int i;

                /* Skip over this group if it has no CPUs allowed */
                if (!cpumask_intersects(sched_group_cpus(group),
                                        tsk_cpus_allowed(p)))
                        continue;

                local_group = cpumask_test_cpu(this_cpu,
                                               sched_group_cpus(group));

                /* Tally up the load of all CPUs in the group */
                avg_load = 0;

                for_each_cpu(i, sched_group_cpus(group)) {
                        /* Bias balancing toward cpus of our domain */
                        if (local_group)
                                load = source_load(i, load_idx);
                        else
                                load = target_load(i, load_idx);

                        avg_load += load;
                }

                /* Adjust by relative CPU power of the group */
                avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power;

                if (local_group) {
                        this_load = avg_load;
                } else if (avg_load < min_load) {
                        min_load = avg_load;
                        idlest = group;
                }
        } while (group = group->next, group != sd->groups);

        if (!idlest || 100*this_load < imbalance*min_load)
                return NULL;
        return idlest;
}

/*
 * find_idlest_cpu - find the idlest cpu among the cpus in group.
 */
static int
find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
{
        unsigned long load, min_load = ULONG_MAX;
        int idlest = -1;
        int i;

        /* Traverse only the allowed CPUs */
        for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
                load = weighted_cpuload(i);

                if (load < min_load || (load == min_load && i == this_cpu)) {
                        min_load = load;
                        idlest = i;
                }
        }

        return idlest;
}

/*
 * Try and locate an idle CPU in the sched_domain.
 */
static int select_idle_sibling(struct task_struct *p, int target)
{
        struct sched_domain *sd;
        struct sched_group *sg;
        int i = task_cpu(p);

        if (idle_cpu(target))
                return target;

        /*
         * If the prevous cpu is cache affine and idle, don't be stupid.
         */
        if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
                return i;

        /*
         * Otherwise, iterate the domains and find an elegible idle cpu.
         */
        sd = rcu_dereference(per_cpu(sd_llc, target));
        for_each_lower_domain(sd) {
                sg = sd->groups;
                do {
                        if (!cpumask_intersects(sched_group_cpus(sg),
                                                tsk_cpus_allowed(p)))
                                goto next;

                        for_each_cpu(i, sched_group_cpus(sg)) {
                                if (i == target || !idle_cpu(i))
                                        goto next;
                        }

                        target = cpumask_first_and(sched_group_cpus(sg),
                                        tsk_cpus_allowed(p));
                        goto done;
next:
                        sg = sg->next;
                } while (sg != sd->groups);
        }
done:
        return target;
}

/*
 * sched_balance_self: balance the current task (running on cpu) in domains
 * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
 * SD_BALANCE_EXEC.
 *
 * Balance, ie. select the least loaded group.
 *
 * Returns the target CPU number, or the same CPU if no balancing is needed.
 *
 * preempt must be disabled.
 */
static int
select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
{
        struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
        int cpu = smp_processor_id();
        int prev_cpu = task_cpu(p);
        int new_cpu = cpu;
        int want_affine = 0;
        int sync = wake_flags & WF_SYNC;

        if (p->nr_cpus_allowed == 1)
                return prev_cpu;

        if (sd_flag & SD_BALANCE_WAKE) {
                if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
                        want_affine = 1;
                new_cpu = prev_cpu;
        }

        rcu_read_lock();
        for_each_domain(cpu, tmp) {
                if (!(tmp->flags & SD_LOAD_BALANCE))
                        continue;

                /*
                 * If both cpu and prev_cpu are part of this domain,
                 * cpu is a valid SD_WAKE_AFFINE target.
                 */
                if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
                    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
                        affine_sd = tmp;
                        break;
                }

                if (tmp->flags & sd_flag)
                        sd = tmp;
        }

        if (affine_sd) {
                if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
                        prev_cpu = cpu;

                new_cpu = select_idle_sibling(p, prev_cpu);
                goto unlock;
        }

        while (sd) {
                int load_idx = sd->forkexec_idx;
                struct sched_group *group;
                int weight;

                if (!(sd->flags & sd_flag)) {
                        sd = sd->child;
                        continue;
                }

                if (sd_flag & SD_BALANCE_WAKE)
                        load_idx = sd->wake_idx;

                group = find_idlest_group(sd, p, cpu, load_idx);
                if (!group) {
                        sd = sd->child;
                        continue;
                }

                new_cpu = find_idlest_cpu(group, p, cpu);
                if (new_cpu == -1 || new_cpu == cpu) {
                        /* Now try balancing at a lower domain level of cpu */
                        sd = sd->child;
                        continue;
                }

                /* Now try balancing at a lower domain level of new_cpu */
                cpu = new_cpu;
                weight = sd->span_weight;
                sd = NULL;
                for_each_domain(cpu, tmp) {
                        if (weight <= tmp->span_weight)
                                break;
                        if (tmp->flags & sd_flag)
                                sd = tmp;
                }
                /* while loop will break here if sd == NULL */
        }
unlock:
        rcu_read_unlock();

        return new_cpu;
}

/*
 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
 * cfs_rq_of(p) references at time of call are still valid and identify the
 * previous cpu.  However, the caller only guarantees p->pi_lock is held; no
 * other assumptions, including the state of rq->lock, should be made.
 */
static void
migrate_task_rq_fair(struct task_struct *p, int next_cpu)
{
        struct sched_entity *se = &p->se;
        struct cfs_rq *cfs_rq = cfs_rq_of(se);

        /*
         * Load tracking: accumulate removed load so that it can be processed
         * when we next update owning cfs_rq under rq->lock.  Tasks contribute
         * to blocked load iff they have a positive decay-count.  It can never
         * be negative here since on-rq tasks have decay-count == 0.
         */
        if (se->avg.decay_count) {
                se->avg.decay_count = -__synchronize_entity_decay(se);
                atomic_long_add(se->avg.load_avg_contrib,
                                                &cfs_rq->removed_load);
        }
}
#endif /* CONFIG_SMP */

static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
{
        unsigned long gran = sysctl_sched_wakeup_granularity;

        /*
         * Since its curr running now, convert the gran from real-time
         * to virtual-time in his units.
         *
         * By using 'se' instead of 'curr' we penalize light tasks, so
         * they get preempted easier. That is, if 'se' < 'curr' then
         * the resulting gran will be larger, therefore penalizing the
         * lighter, if otoh 'se' > 'curr' then the resulting gran will
         * be smaller, again penalizing the lighter task.
         *
         * This is especially important for buddies when the leftmost
         * task is higher priority than the buddy.
         */
        return calc_delta_fair(gran, se);
}

/*
 * Should 'se' preempt 'curr'.
 *
 *             |s1
 *        |s2
 *   |s3
 *         g
 *      |<--->|c
 *
 *  w(c, s1) = -1
 *  w(c, s2) =  0
 *  w(c, s3) =  1
 *
 */
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
{
        s64 gran, vdiff = curr->vruntime - se->vruntime;

        if (vdiff <= 0)
                return -1;

        gran = wakeup_gran(curr, se);
        if (vdiff > gran)
                return 1;

        return 0;
}

static void set_last_buddy(struct sched_entity *se)
{
        if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
                return;

        for_each_sched_entity(se)
                cfs_rq_of(se)->last = se;
}

static void set_next_buddy(struct sched_entity *se)
{
        if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
                return;

        for_each_sched_entity(se)
                cfs_rq_of(se)->next = se;
}

static void set_skip_buddy(struct sched_entity *se)
{
        for_each_sched_entity(se)
                cfs_rq_of(se)->skip = se;
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
{
        struct task_struct *curr = rq->curr;
        struct sched_entity *se = &curr->se, *pse = &p->se;
        struct cfs_rq *cfs_rq = task_cfs_rq(curr);
        int scale = cfs_rq->nr_running >= sched_nr_latency;
        int next_buddy_marked = 0;

        if (unlikely(se == pse))
                return;

        /*
         * This is possible from callers such as move_task(), in which we
         * unconditionally check_prempt_curr() after an enqueue (which may have
         * lead to a throttle).  This both saves work and prevents false
         * next-buddy nomination below.
         */
        if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
                return;

        if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
                set_next_buddy(pse);
                next_buddy_marked = 1;
        }

        /*
         * We can come here with TIF_NEED_RESCHED already set from new task
         * wake up path.
         *
         * Note: this also catches the edge-case of curr being in a throttled
         * group (e.g. via set_curr_task), since update_curr() (in the
         * enqueue of curr) will have resulted in resched being set.  This
         * prevents us from potentially nominating it as a false LAST_BUDDY
         * below.
         */
        if (test_tsk_need_resched(curr))
                return;

        /* Idle tasks are by definition preempted by non-idle tasks. */
        if (unlikely(curr->policy == SCHED_IDLE) &&
            likely(p->policy != SCHED_IDLE))
                goto preempt;

        /*
         * Batch and idle tasks do not preempt non-idle tasks (their preemption
         * is driven by the tick):
         */
        if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
                return;

        find_matching_se(&se, &pse);
        update_curr(cfs_rq_of(se));
        BUG_ON(!pse);
        if (wakeup_preempt_entity(se, pse) == 1) {
                /*
                 * Bias pick_next to pick the sched entity that is
                 * triggering this preemption.
                 */
                if (!next_buddy_marked)
                        set_next_buddy(pse);
                goto preempt;
        }

        return;

preempt:
        resched_task(curr);
        /*
         * Only set the backward buddy when the current task is still
         * on the rq. This can happen when a wakeup gets interleaved
         * with schedule on the ->pre_schedule() or idle_balance()
         * point, either of which can * drop the rq lock.
         *
         * Also, during early boot the idle thread is in the fair class,
         * for obvious reasons its a bad idea to schedule back to it.
         */
        if (unlikely(!se->on_rq || curr == rq->idle))
                return;

        if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
                set_last_buddy(se);
}

static struct task_struct *pick_next_task_fair(struct rq *rq)
{
        struct task_struct *p;
        struct cfs_rq *cfs_rq = &rq->cfs;
        struct sched_entity *se;

        if (!cfs_rq->nr_running)
                return NULL;

        do {
                se = pick_next_entity(cfs_rq);
                set_next_entity(cfs_rq, se);
                cfs_rq = group_cfs_rq(se);
        } while (cfs_rq);

        p = task_of(se);
        if (hrtick_enabled(rq))
                hrtick_start_fair(rq, p);

        return p;
}

/*
 * Account for a descheduled task:
 */
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
{
        struct sched_entity *se = &prev->se;
        struct cfs_rq *cfs_rq;

        for_each_sched_entity(se) {
                cfs_rq = cfs_rq_of(se);
                put_prev_entity(cfs_rq, se);
        }
}

/*
 * sched_yield() is very simple
 *
 * The magic of dealing with the ->skip buddy is in pick_next_entity.
 */
static void yield_task_fair(struct rq *rq)
{
        struct task_struct *curr = rq->curr;
        struct cfs_rq *cfs_rq = task_cfs_rq(curr);
        struct sched_entity *se = &curr->se;

        /*
         * Are we the only task in the tree?
         */
        if (unlikely(rq->nr_running == 1))
                return;

        clear_buddies(cfs_rq, se);

        if (curr->policy != SCHED_BATCH) {
                update_rq_clock(rq);
                /*
                 * Update run-time statistics of the 'current'.
                 */
                update_curr(cfs_rq);
                /*
                 * Tell update_rq_clock() that we've just updated,
                 * so we don't do microscopic update in schedule()
                 * and double the fastpath cost.
                 */
                 rq->skip_clock_update = 1;
        }

        set_skip_buddy(se);
}

static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
        struct sched_entity *se = &p->se;

        /* throttled hierarchies are not runnable */
        if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
                return false;

        /* Tell the scheduler that we'd really like pse to run next. */
        set_next_buddy(se);

        yield_task_fair(rq);

        return true;
}

#ifdef CONFIG_SMP
/**************************************************
 * Fair scheduling class load-balancing methods.
 *
 * BASICS
 *
 * The purpose of load-balancing is to achieve the same basic fairness the
 * per-cpu scheduler provides, namely provide a proportional amount of compute
 * time to each task. This is expressed in the following equation:
 *
 *   W_i,n/P_i == W_j,n/P_j for all i,j                               (1)
 *
 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
 * W_i,0 is defined as:
 *
 *   W_i,0 = \Sum_j w_i,j                                             (2)
 *
 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
 * is derived from the nice value as per prio_to_weight[].
 *
 * The weight average is an exponential decay average of the instantaneous
 * weight:
 *
 *   W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0               (3)
 *
 * P_i is the cpu power (or compute capacity) of cpu i, typically it is the
 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
 * can also include other factors [XXX].
 *
 * To achieve this balance we define a measure of imbalance which follows
 * directly from (1):
 *
 *   imb_i,j = max{ avg(W/P), W_i/P_i } - min{ avg(W/P), W_j/P_j }    (4)
 *
 * We them move tasks around to minimize the imbalance. In the continuous
 * function space it is obvious this converges, in the discrete case we get
 * a few fun cases generally called infeasible weight scenarios.
 *
 * [XXX expand on:
 *     - infeasible weights;
 *     - local vs global optima in the discrete case. ]
 *
 *
 * SCHED DOMAINS
 *
 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
 * for all i,j solution, we create a tree of cpus that follows the hardware
 * topology where each level pairs two lower groups (or better). This results
 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
 * tree to only the first of the previous level and we decrease the frequency
 * of load-balance at each level inv. proportional to the number of cpus in
 * the groups.
 *
 * This yields:
 *
 *     log_2 n     1     n
 *   \Sum       { --- * --- * 2^i } = O(n)                            (5)
 *     i = 0      2^i   2^i
 *                               `- size of each group
 *         |         |     `- number of cpus doing load-balance
 *         |         `- freq
 *         `- sum over all levels
 *
 * Coupled with a limit on how many tasks we can migrate every balance pass,
 * this makes (5) the runtime complexity of the balancer.
 *
 * An important property here is that each CPU is still (indirectly) connected
 * to every other cpu in at most O(log n) steps:
 *
 * The adjacency matrix of the resulting graph is given by:
 *
 *             log_2 n     
 *   A_i,j = \Union     (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1)  (6)
 *             k = 0
 *
 * And you'll find that:
 *
 *   A^(log_2 n)_i,j != 0  for all i,j                                (7)
 *
 * Showing there's indeed a path between every cpu in at most O(log n) steps.
 * The task movement gives a factor of O(m), giving a convergence complexity
 * of:
 *
 *   O(nm log n),  n := nr_cpus, m := nr_tasks                        (8)
 *
 *
 * WORK CONSERVING
 *
 * In order to avoid CPUs going idle while there's still work to do, new idle
 * balancing is more aggressive and has the newly idle cpu iterate up the domain
 * tree itself instead of relying on other CPUs to bring it work.
 *
 * This adds some complexity to both (5) and (8) but it reduces the total idle
 * time.
 *
 * [XXX more?]
 *
 *
 * CGROUPS
 *
 * Cgroups make a horror show out of (2), instead of a simple sum we get:
 *
 *                                s_k,i
 *   W_i,0 = \Sum_j \Prod_k w_k * -----                               (9)
 *                                 S_k
 *
 * Where
 *
 *   s_k,i = \Sum_j w_i,j,k  and  S_k = \Sum_i s_k,i                 (10)
 *
 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
 *
 * The big problem is S_k, its a global sum needed to compute a local (W_i)
 * property.
 *
 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
 *      rewrite all of this once again.]
 */ 

static unsigned long __read_mostly max_load_balance_interval = HZ/10;

#define LBF_ALL_PINNED  0x01
#define LBF_NEED_BREAK  0x02
#define LBF_SOME_PINNED 0x04

struct lb_env {
        struct sched_domain     *sd;

        struct rq               *src_rq;
        int                     src_cpu;

        int                     dst_cpu;
        struct rq               *dst_rq;

        struct cpumask          *dst_grpmask;
        int                     new_dst_cpu;
        enum cpu_idle_type      idle;
        long                    imbalance;
        /* The set of CPUs under consideration for load-balancing */
        struct cpumask          *cpus;

        unsigned int            flags;

        unsigned int            loop;
        unsigned int            loop_break;
        unsigned int            loop_max;
};

/*
 * move_task - move a task from one runqueue to another runqueue.
 * Both runqueues must be locked.
 */
static void move_task(struct task_struct *p, struct lb_env *env)
{
        deactivate_task(env->src_rq, p, 0);
        set_task_cpu(p, env->dst_cpu);
        activate_task(env->dst_rq, p, 0);
        check_preempt_curr(env->dst_rq, p, 0);
}

/*
 * Is this task likely cache-hot:
 */
static int
task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
{
        s64 delta;

        if (p->sched_class != &fair_sched_class)
                return 0;

        if (unlikely(p->policy == SCHED_IDLE))
                return 0;

        /*
         * Buddy candidates are cache hot:
         */
        if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running &&
                        (&p->se == cfs_rq_of(&p->se)->next ||
                         &p->se == cfs_rq_of(&p->se)->last))
                return 1;

        if (sysctl_sched_migration_cost == -1)
                return 1;
        if (sysctl_sched_migration_cost == 0)
                return 0;

        delta = now - p->se.exec_start;

        return delta < (s64)sysctl_sched_migration_cost;
}

/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
int can_migrate_task(struct task_struct *p, struct lb_env *env)
{
        int tsk_cache_hot = 0;
        /*
         * We do not migrate tasks that are:
         * 1) throttled_lb_pair, or
         * 2) cannot be migrated to this CPU due to cpus_allowed, or
         * 3) running (obviously), or
         * 4) are cache-hot on their current CPU.
         */
        if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
                return 0;

        if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
                int cpu;

                schedstat_inc(p, se.statistics.nr_failed_migrations_affine);

                /*
                 * Remember if this task can be migrated to any other cpu in
                 * our sched_group. We may want to revisit it if we couldn't
                 * meet load balance goals by pulling other tasks on src_cpu.
                 *
                 * Also avoid computing new_dst_cpu if we have already computed
                 * one in current iteration.
                 */
                if (!env->dst_grpmask || (env->flags & LBF_SOME_PINNED))
                        return 0;

                /* Prevent to re-select dst_cpu via env's cpus */
                for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
                        if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
                                env->flags |= LBF_SOME_PINNED;
                                env->new_dst_cpu = cpu;
                                break;
                        }
                }

                return 0;
        }

        /* Record that we found atleast one task that could run on dst_cpu */
        env->flags &= ~LBF_ALL_PINNED;

        if (task_running(env->src_rq, p)) {
                schedstat_inc(p, se.statistics.nr_failed_migrations_running);
                return 0;
        }

        /*
         * Aggressive migration if:
         * 1) task is cache cold, or
         * 2) too many balance attempts have failed.
         */

        tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq), env->sd);
        if (!tsk_cache_hot ||
                env->sd->nr_balance_failed > env->sd->cache_nice_tries) {

                if (tsk_cache_hot) {
                        schedstat_inc(env->sd, lb_hot_gained[env->idle]);
                        schedstat_inc(p, se.statistics.nr_forced_migrations);
                }

                return 1;
        }