core.c

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/*
 *  kernel/sched/core.c
 *
 *  Kernel scheduler and related syscalls
 *
 *  Copyright (C) 1991-2002  Linus Torvalds
 *
 *  1996-12-23  Modified by Dave Grothe to fix bugs in semaphores and
 *      make semaphores SMP safe
 *  1998-11-19  Implemented schedule_timeout() and related stuff
 *      by Andrea Arcangeli
 *  2002-01-04  New ultra-scalable O(1) scheduler by Ingo Molnar:
 *      hybrid priority-list and round-robin design with
 *      an array-switch method of distributing timeslices
 *      and per-CPU runqueues.  Cleanups and useful suggestions
 *      by Davide Libenzi, preemptible kernel bits by Robert Love.
 *  2003-09-03  Interactivity tuning by Con Kolivas.
 *  2004-04-02  Scheduler domains code by Nick Piggin
 *  2007-04-15  Work begun on replacing all interactivity tuning with a
 *              fair scheduling design by Con Kolivas.
 *  2007-05-05  Load balancing (smp-nice) and other improvements
 *              by Peter Williams
 *  2007-05-06  Interactivity improvements to CFS by Mike Galbraith
 *  2007-07-01  Group scheduling enhancements by Srivatsa Vaddagiri
 *  2007-11-29  RT balancing improvements by Steven Rostedt, Gregory Haskins,
 *              Thomas Gleixner, Mike Kravetz
 */

#include <linux/mm.h>
#include <linux/module.h>
#include <linux/nmi.h>
#include <linux/init.h>
#include <linux/uaccess.h>
#include <linux/highmem.h>
#include <asm/mmu_context.h>
#include <linux/interrupt.h>
#include <linux/capability.h>
#include <linux/completion.h>
#include <linux/kernel_stat.h>
#include <linux/debug_locks.h>
#include <linux/perf_event.h>
#include <linux/security.h>
#include <linux/notifier.h>
#include <linux/profile.h>
#include <linux/freezer.h>
#include <linux/vmalloc.h>
#include <linux/blkdev.h>
#include <linux/delay.h>
#include <linux/pid_namespace.h>
#include <linux/smp.h>
#include <linux/threads.h>
#include <linux/timer.h>
#include <linux/rcupdate.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/percpu.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/sysctl.h>
#include <linux/syscalls.h>
#include <linux/times.h>
#include <linux/tsacct_kern.h>
#include <linux/kprobes.h>
#include <linux/delayacct.h>
#include <linux/unistd.h>
#include <linux/pagemap.h>
#include <linux/hrtimer.h>
#include <linux/tick.h>
#include <linux/debugfs.h>
#include <linux/ctype.h>
#include <linux/ftrace.h>
#include <linux/slab.h>
#include <linux/init_task.h>
#include <linux/binfmts.h>

#include <asm/switch_to.h>
#include <asm/tlb.h>
#include <asm/irq_regs.h>
#include <asm/mutex.h>
#ifdef CONFIG_PARAVIRT
#include <asm/paravirt.h>
#endif

#include "sched.h"
#include "../workqueue_sched.h"
#include "../smpboot.h"

#define CREATE_TRACE_POINTS
#include <trace/events/sched.h>

void start_bandwidth_timer(struct hrtimer *period_timer, ktime_t period)
{
    unsigned long delta;
    ktime_t soft, hard, now;

    for (;;) {
        if (hrtimer_active(period_timer))
            break;

        now = hrtimer_cb_get_time(period_timer);
        hrtimer_forward(period_timer, now, period);

        soft = hrtimer_get_softexpires(period_timer);
        hard = hrtimer_get_expires(period_timer);
        delta = ktime_to_ns(ktime_sub(hard, soft));
        __hrtimer_start_range_ns(period_timer, soft, delta,
                     HRTIMER_MODE_ABS_PINNED, 0);
    }
}

DEFINE_MUTEX(sched_domains_mutex);
DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);

static void update_rq_clock_task(struct rq *rq, s64 delta);

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

    if (rq->skip_clock_update > 0)
        return;

    delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
    rq->clock += delta;
    update_rq_clock_task(rq, delta);
}

/*
 * Debugging: various feature bits
 */

#define SCHED_FEAT(name, enabled)   \
    (1UL << __SCHED_FEAT_##name) * enabled |

const_debug unsigned int sysctl_sched_features =
#include "features.h"
    0;

#undef SCHED_FEAT

#ifdef CONFIG_SCHED_DEBUG
#define SCHED_FEAT(name, enabled)   \
    #name ,

static const char * const sched_feat_names[] = {
#include "features.h"
};

#undef SCHED_FEAT

static int sched_feat_show(struct seq_file *m, void *v)
{
    int i;

    for (i = 0; i < __SCHED_FEAT_NR; i++) {
        if (!(sysctl_sched_features & (1UL << i)))
            seq_puts(m, "NO_");
        seq_printf(m, "%s ", sched_feat_names[i]);
    }
    seq_puts(m, "\n");

    return 0;
}

#ifdef HAVE_JUMP_LABEL

#define jump_label_key__true  STATIC_KEY_INIT_TRUE
#define jump_label_key__false STATIC_KEY_INIT_FALSE

#define SCHED_FEAT(name, enabled)   \
    jump_label_key__##enabled ,

struct static_key sched_feat_keys[__SCHED_FEAT_NR] = {
#include "features.h"
};

#undef SCHED_FEAT

static void sched_feat_disable(int i)
{
    if (static_key_enabled(&sched_feat_keys[i]))
        static_key_slow_dec(&sched_feat_keys[i]);
}

static void sched_feat_enable(int i)
{
    if (!static_key_enabled(&sched_feat_keys[i]))
        static_key_slow_inc(&sched_feat_keys[i]);
}
#else
static void sched_feat_disable(int i) { };
static void sched_feat_enable(int i) { };
#endif /* HAVE_JUMP_LABEL */

static ssize_t
sched_feat_write(struct file *filp, const char __user *ubuf,
        size_t cnt, loff_t *ppos)
{
    char buf[64];
    char *cmp;
    int neg = 0;
    int i;

    if (cnt > 63)
        cnt = 63;

    if (copy_from_user(&buf, ubuf, cnt))
        return -EFAULT;

    buf[cnt] = 0;
    cmp = strstrip(buf);

    if (strncmp(cmp, "NO_", 3) == 0) {
        neg = 1;
        cmp += 3;
    }

    for (i = 0; i < __SCHED_FEAT_NR; i++) {
        if (strcmp(cmp, sched_feat_names[i]) == 0) {
            if (neg) {
                sysctl_sched_features &= ~(1UL << i);
                sched_feat_disable(i);
            } else {
                sysctl_sched_features |= (1UL << i);
                sched_feat_enable(i);
            }
            break;
        }
    }

    if (i == __SCHED_FEAT_NR)
        return -EINVAL;

    *ppos += cnt;

    return cnt;
}

static int sched_feat_open(struct inode *inode, struct file *filp)
{
    return single_open(filp, sched_feat_show, NULL);
}

static const struct file_operations sched_feat_fops = {
    .open       = sched_feat_open,
    .write      = sched_feat_write,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = single_release,
};

static __init int sched_init_debug(void)
{
    debugfs_create_file("sched_features", 0644, NULL, NULL,
            &sched_feat_fops);

    return 0;
}
late_initcall(sched_init_debug);
#endif /* CONFIG_SCHED_DEBUG */

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

/*
 * period over which we average the RT time consumption, measured
 * in ms.
 *
 * default: 1s
 */
const_debug unsigned int sysctl_sched_time_avg = MSEC_PER_SEC;

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

__read_mostly int scheduler_running;

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



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

    lockdep_assert_held(&p->pi_lock);

    for (;;) {
        rq = task_rq(p);
        raw_spin_lock(&rq->lock);
        if (likely(rq == task_rq(p)))
            return rq;
        raw_spin_unlock(&rq->lock);
    }
}

/*
 * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
 */
static struct rq *task_rq_lock(struct task_struct *p, unsigned long *flags)
    __acquires(p->pi_lock)
    __acquires(rq->lock)
{
    struct rq *rq;

    for (;;) {
        raw_spin_lock_irqsave(&p->pi_lock, *flags);
        rq = task_rq(p);
        raw_spin_lock(&rq->lock);
        if (likely(rq == task_rq(p)))
            return rq;
        raw_spin_unlock(&rq->lock);
        raw_spin_unlock_irqrestore(&p->pi_lock, *flags);
    }
}

static void __task_rq_unlock(struct rq *rq)
    __releases(rq->lock)
{
    raw_spin_unlock(&rq->lock);
}

static inline void
task_rq_unlock(struct rq *rq, struct task_struct *p, unsigned long *flags)
    __releases(rq->lock)
    __releases(p->pi_lock)
{
    raw_spin_unlock(&rq->lock);
    raw_spin_unlock_irqrestore(&p->pi_lock, *flags);
}

/*
 * this_rq_lock - lock this runqueue and disable interrupts.
 */
static struct rq *this_rq_lock(void)
    __acquires(rq->lock)
{
    struct rq *rq;

    local_irq_disable();
    rq = this_rq();
    raw_spin_lock(&rq->lock);

    return rq;
}

#ifdef CONFIG_SCHED_HRTICK
/*
 * Use HR-timers to deliver accurate preemption points.
 *
 * Its all a bit involved since we cannot program an hrt while holding the
 * rq->lock. So what we do is store a state in in rq->hrtick_* and ask for a
 * reschedule event.
 *
 * When we get rescheduled we reprogram the hrtick_timer outside of the
 * rq->lock.
 */

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

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

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

    raw_spin_lock(&rq->lock);
    update_rq_clock(rq);
    rq->curr->sched_class->task_tick(rq, rq->curr, 1);
    raw_spin_unlock(&rq->lock);

    return HRTIMER_NORESTART;
}

#ifdef CONFIG_SMP
/*
 * called from hardirq (IPI) context
 */
static void __hrtick_start(void *arg)
{
    struct rq *rq = arg;

    raw_spin_lock(&rq->lock);
    hrtimer_restart(&rq->hrtick_timer);
    rq->hrtick_csd_pending = 0;
    raw_spin_unlock(&rq->lock);
}

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

    hrtimer_set_expires(timer, time);

    if (rq == this_rq()) {
        hrtimer_restart(timer);
    } else if (!rq->hrtick_csd_pending) {
        __smp_call_function_single(cpu_of(rq), &rq->hrtick_csd, 0);
        rq->hrtick_csd_pending = 1;
    }
}

static int
hotplug_hrtick(struct notifier_block *nfb, unsigned long action, void *hcpu)
{
    int cpu = (int)(long)hcpu;

    switch (action) {
    case CPU_UP_CANCELED:
    case CPU_UP_CANCELED_FROZEN:
    case CPU_DOWN_PREPARE:
    case CPU_DOWN_PREPARE_FROZEN:
    case CPU_DEAD:
    case CPU_DEAD_FROZEN:
        hrtick_clear(cpu_rq(cpu));
        return NOTIFY_OK;
    }

    return NOTIFY_DONE;
}

static __init void init_hrtick(void)
{
    hotcpu_notifier(hotplug_hrtick, 0);
}
#else
/*
 * Called to set the hrtick timer state.
 *
 * called with rq->lock held and irqs disabled
 */
void hrtick_start(struct rq *rq, u64 delay)
{
    __hrtimer_start_range_ns(&rq->hrtick_timer, ns_to_ktime(delay), 0,
            HRTIMER_MODE_REL_PINNED, 0);
}

static inline void init_hrtick(void)
{
}
#endif /* CONFIG_SMP */

static void init_rq_hrtick(struct rq *rq)
{
#ifdef CONFIG_SMP
    rq->hrtick_csd_pending = 0;

    rq->hrtick_csd.flags = 0;
    rq->hrtick_csd.func = __hrtick_start;
    rq->hrtick_csd.info = rq;
#endif

    hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
    rq->hrtick_timer.function = hrtick;
}
#else   /* CONFIG_SCHED_HRTICK */
static inline void hrtick_clear(struct rq *rq)
{
}

static inline void init_rq_hrtick(struct rq *rq)
{
}

static inline void init_hrtick(void)
{
}
#endif  /* CONFIG_SCHED_HRTICK */

/*
 * resched_task - mark a task 'to be rescheduled now'.
 *
 * On UP this means the setting of the need_resched flag, on SMP it
 * might also involve a cross-CPU call to trigger the scheduler on
 * the target CPU.
 */
#ifdef CONFIG_SMP

#ifndef tsk_is_polling
#define tsk_is_polling(t) 0
#endif

void resched_task(struct task_struct *p)
{
    int cpu;

    assert_raw_spin_locked(&task_rq(p)->lock);

    if (test_tsk_need_resched(p))
        return;

    set_tsk_need_resched(p);

    cpu = task_cpu(p);
    if (cpu == smp_processor_id())
        return;

    /* NEED_RESCHED must be visible before we test polling */
    smp_mb();
    if (!tsk_is_polling(p))
        smp_send_reschedule(cpu);
}

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

    if (!raw_spin_trylock_irqsave(&rq->lock, flags))
        return;
    resched_task(cpu_curr(cpu));
    raw_spin_unlock_irqrestore(&rq->lock, flags);
}

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

    rcu_read_lock();
    for_each_domain(cpu, sd) {
        for_each_cpu(i, sched_domain_span(sd)) {
            if (!idle_cpu(i)) {
                cpu = i;
                goto unlock;
            }
        }
    }
unlock:
    rcu_read_unlock();
    return cpu;
}
/*
 * When add_timer_on() enqueues a timer into the timer wheel of an
 * idle CPU then this timer might expire before the next timer event
 * which is scheduled to wake up that CPU. In case of a completely
 * idle system the next event might even be infinite time into the
 * future. wake_up_idle_cpu() ensures that the CPU is woken up and
 * leaves the inner idle loop so the newly added timer is taken into
 * account when the CPU goes back to idle and evaluates the timer
 * wheel for the next timer event.
 */
void wake_up_idle_cpu(int cpu)
{
    struct rq *rq = cpu_rq(cpu);

    if (cpu == smp_processor_id())
        return;

    /*
     * This is safe, as this function is called with the timer
     * wheel base lock of (cpu) held. When the CPU is on the way
     * to idle and has not yet set rq->curr to idle then it will
     * be serialized on the timer wheel base lock and take the new
     * timer into account automatically.
     */
    if (rq->curr != rq->idle)
        return;

    /*
     * We can set TIF_RESCHED on the idle task of the other CPU
     * lockless. The worst case is that the other CPU runs the
     * idle task through an additional NOOP schedule()
     */
    set_tsk_need_resched(rq->idle);

    /* NEED_RESCHED must be visible before we test polling */
    smp_mb();
    if (!tsk_is_polling(rq->idle))
        smp_send_reschedule(cpu);
}

static inline bool got_nohz_idle_kick(void)
{
    int cpu = smp_processor_id();
    return idle_cpu(cpu) && test_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu));
}

#else /* CONFIG_NO_HZ */

static inline bool got_nohz_idle_kick(void)
{
    return false;
}

#endif /* CONFIG_NO_HZ */

void sched_avg_update(struct rq *rq)
{
    s64 period = sched_avg_period();

    while ((s64)(rq->clock - rq->age_stamp) > period) {
        /*
         * Inline assembly required to prevent the compiler
         * optimising this loop into a divmod call.
         * See __iter_div_u64_rem() for another example of this.
         */
        asm("" : "+rm" (rq->age_stamp));
        rq->age_stamp += period;
        rq->rt_avg /= 2;
    }
}

#else /* !CONFIG_SMP */
void resched_task(struct task_struct *p)
{
    assert_raw_spin_locked(&task_rq(p)->lock);
    set_tsk_need_resched(p);
}
#endif /* CONFIG_SMP */

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

    parent = from;

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

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

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

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

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

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

    load->weight = scale_load(prio_to_weight[prio]);
    load->inv_weight = prio_to_wmult[prio];
}

static void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
{
    update_rq_clock(rq);
    sched_info_queued(p);
    p->sched_class->enqueue_task(rq, p, flags);
}

static void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
{
    update_rq_clock(rq);
    sched_info_dequeued(p);
    p->sched_class->dequeue_task(rq, p, flags);
}

void activate_task(struct rq *rq, struct task_struct *p, int flags)
{
    if (task_contributes_to_load(p))
        rq->nr_uninterruptible--;

    enqueue_task(rq, p, flags);
}

void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
{
    if (task_contributes_to_load(p))
        rq->nr_uninterruptible++;

    dequeue_task(rq, p, flags);
}

static void update_rq_clock_task(struct rq *rq, s64 delta)
{
/*
 * In theory, the compile should just see 0 here, and optimize out the call
 * to sched_rt_avg_update. But I don't trust it...
 */
#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
    s64 steal = 0, irq_delta = 0;
#endif
#ifdef CONFIG_IRQ_TIME_ACCOUNTING
    irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;

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

    rq->prev_irq_time += irq_delta;
    delta -= irq_delta;
#endif
#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
    if (static_key_false((&paravirt_steal_rq_enabled))) {
        u64 st;

        steal = paravirt_steal_clock(cpu_of(rq));
        steal -= rq->prev_steal_time_rq;

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

        st = steal_ticks(steal);
        steal = st * TICK_NSEC;

        rq->prev_steal_time_rq += steal;

        delta -= steal;
    }
#endif

    rq->clock_task += delta;

#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
    if ((irq_delta + steal) && sched_feat(NONTASK_POWER))
        sched_rt_avg_update(rq, irq_delta + steal);
#endif
}

void sched_set_stop_task(int cpu, struct task_struct *stop)
{
    struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
    struct task_struct *old_stop = cpu_rq(cpu)->stop;

    if (stop) {
        /*
         * Make it appear like a SCHED_FIFO task, its something
         * userspace knows about and won't get confused about.
         *
         * Also, it will make PI more or less work without too
         * much confusion -- but then, stop work should not
         * rely on PI working anyway.
         */
        sched_setscheduler_nocheck(stop, SCHED_FIFO, &param);

        stop->sched_class = &stop_sched_class;
    }

    cpu_rq(cpu)->stop = stop;

    if (old_stop) {
        /*
         * Reset it back to a normal scheduling class so that
         * it can die in pieces.
         */
        old_stop->sched_class = &rt_sched_class;
    }
}

/*
 * __normal_prio - return the priority that is based on the static prio
 */
static inline int __normal_prio(struct task_struct *p)
{
    return p->static_prio;
}

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

    if (task_has_rt_policy(p))
        prio = MAX_RT_PRIO-1 - p->rt_priority;
    else
        prio = __normal_prio(p);
    return prio;
}

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

inline int task_curr(const struct task_struct *p)
{
    return cpu_curr(task_cpu(p)) == p;
}

static inline void check_class_changed(struct rq *rq, struct task_struct *p,
                       const struct sched_class *prev_class,
                       int oldprio)
{
    if (prev_class != p->sched_class) {
        if (prev_class->switched_from)
            prev_class->switched_from(rq, p);
        p->sched_class->switched_to(rq, p);
    } else if (oldprio != p->prio)
        p->sched_class->prio_changed(rq, p, oldprio);
}

void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
{
    const struct sched_class *class;

    if (p->sched_class == rq->curr->sched_class) {
        rq->curr->sched_class->check_preempt_curr(rq, p, flags);
    } else {
        for_each_class(class) {
            if (class == rq->curr->sched_class)
                break;
            if (class == p->sched_class) {
                resched_task(rq->curr);
                break;
            }
        }
    }

    /*
     * A queue event has occurred, and we're going to schedule.  In
     * this case, we can save a useless back to back clock update.
     */
    if (rq->curr->on_rq && test_tsk_need_resched(rq->curr))
        rq->skip_clock_update = 1;
}

#ifdef CONFIG_SMP
void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
{
#ifdef CONFIG_SCHED_DEBUG
    /*
     * We should never call set_task_cpu() on a blocked task,
     * ttwu() will sort out the placement.
     */
    WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
            !(task_thread_info(p)->preempt_count & PREEMPT_ACTIVE));

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

    trace_sched_migrate_task(p, new_cpu);

    if (task_cpu(p) != new_cpu) {
        p->se.nr_migrations++;
        perf_sw_event(PERF_COUNT_SW_CPU_MIGRATIONS, 1, NULL, 0);
    }

    __set_task_cpu(p, new_cpu);
}

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

static int migration_cpu_stop(void *data);

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

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

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

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

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

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

        /*
         * It's not enough that it's not actively running,
         * it must be off the runqueue _entirely_, and not
         * preempted!
         *
         * So if it was still runnable (but just not actively
         * running right now), it's preempted, and we should
         * yield - it could be a while.
         */
        if (unlikely(on_rq)) {
            ktime_t to = ktime_set(0, NSEC_PER_SEC/HZ);

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

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

    return ncsw;
}

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

    preempt_disable();
    cpu = task_cpu(p);
    if ((cpu != smp_processor_id()) && task_curr(p))
        smp_send_reschedule(cpu);
    preempt_enable();
}
EXPORT_SYMBOL_GPL(kick_process);
#endif /* CONFIG_SMP */

#ifdef CONFIG_SMP
/*
 * ->cpus_allowed is protected by both rq->lock and p->pi_lock
 */
static int select_fallback_rq(int cpu, struct task_struct *p)
{
    const struct cpumask *nodemask = cpumask_of_node(cpu_to_node(cpu));
    enum { cpuset, possible, fail } state = cpuset;
    int dest_cpu;

    /* Look for allowed, online CPU in same node. */
    for_each_cpu(dest_cpu, nodemask) {
        if (!cpu_online(dest_cpu))
            continue;
        if (!cpu_active(dest_cpu))
            continue;
        if (cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
            return dest_cpu;
    }

    for (;;) {
        /* Any allowed, online CPU? */
        for_each_cpu(dest_cpu, tsk_cpus_allowed(p)) {
            if (!cpu_online(dest_cpu))
                continue;
            if (!cpu_active(dest_cpu))
                continue;
            goto out;
        }

        switch (state) {
        case cpuset:
            /* No more Mr. Nice Guy. */
            cpuset_cpus_allowed_fallback(p);
            state = possible;
            break;

        case possible:
            do_set_cpus_allowed(p, cpu_possible_mask);
            state = fail;
            break;

        case fail:
            BUG();
            break;
        }
    }

out:
    if (state != cpuset) {
        /*
         * Don't tell them about moving exiting tasks or
         * kernel threads (both mm NULL), since they never
         * leave kernel.
         */
        if (p->mm && printk_ratelimit()) {
            printk_sched("process %d (%s) no longer affine to cpu%d\n",
                    task_pid_nr(p), p->comm, cpu);
        }
    }

    return dest_cpu;
}

/*
 * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable.
 */
static inline
int select_task_rq(struct task_struct *p, int sd_flags, int wake_flags)
{
    int cpu = p->sched_class->select_task_rq(p, sd_flags, wake_flags);

    /*
     * In order not to call set_task_cpu() on a blocking task we need
     * to rely on ttwu() to place the task on a valid ->cpus_allowed
     * cpu.
     *
     * Since this is common to all placement strategies, this lives here.
     *
     * [ this allows ->select_task() to simply return task_cpu(p) and
     *   not worry about this generic constraint ]
     */
    if (unlikely(!cpumask_test_cpu(cpu, tsk_cpus_allowed(p)) ||
             !cpu_online(cpu)))
        cpu = select_fallback_rq(task_cpu(p), p);

    return cpu;
}

static void update_avg(u64 *avg, u64 sample)
{
    s64 diff = sample - *avg;
    *avg += diff >> 3;
}
#endif

static void
ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
{
#ifdef CONFIG_SCHEDSTATS
    struct rq *rq = this_rq();

#ifdef CONFIG_SMP
    int this_cpu = smp_processor_id();

    if (cpu == this_cpu) {
        schedstat_inc(rq, ttwu_local);
        schedstat_inc(p, se.statistics.nr_wakeups_local);
    } else {
        struct sched_domain *sd;

        schedstat_inc(p, se.statistics.nr_wakeups_remote);
        rcu_read_lock();
        for_each_domain(this_cpu, sd) {
            if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
                schedstat_inc(sd, ttwu_wake_remote);
                break;
            }
        }
        rcu_read_unlock();
    }

    if (wake_flags & WF_MIGRATED)
        schedstat_inc(p, se.statistics.nr_wakeups_migrate);

#endif /* CONFIG_SMP */

    schedstat_inc(rq, ttwu_count);
    schedstat_inc(p, se.statistics.nr_wakeups);

    if (wake_flags & WF_SYNC)
        schedstat_inc(p, se.statistics.nr_wakeups_sync);

#endif /* CONFIG_SCHEDSTATS */
}

static void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
{
    activate_task(rq, p, en_flags);
    p->on_rq = 1;

    /* if a worker is waking up, notify workqueue */
    if (p->flags & PF_WQ_WORKER)
        wq_worker_waking_up(p, cpu_of(rq));
}

/*
 * Mark the task runnable and perform wakeup-preemption.
 */
static void
ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
{
    trace_sched_wakeup(p, true);
    check_preempt_curr(rq, p, wake_flags);

    p->state = TASK_RUNNING;
#ifdef CONFIG_SMP
    if (p->sched_class->task_woken)
        p->sched_class->task_woken(rq, p);

    if (rq->idle_stamp) {
        u64 delta = rq->clock - rq->idle_stamp;
        u64 max = 2*sysctl_sched_migration_cost;

        if (delta > max)
            rq->avg_idle = max;
        else
            update_avg(&rq->avg_idle, delta);
        rq->idle_stamp = 0;
    }
#endif
}

static void
ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags)
{
#ifdef CONFIG_SMP
    if (p->sched_contributes_to_load)
        rq->nr_uninterruptible--;
#endif

    ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_WAKING);
    ttwu_do_wakeup(rq, p, wake_flags);
}

/*
 * Called in case the task @p isn't fully descheduled from its runqueue,
 * in this case we must do a remote wakeup. Its a 'light' wakeup though,
 * since all we need to do is flip p->state to TASK_RUNNING, since
 * the task is still ->on_rq.
 */
static int ttwu_remote(struct task_struct *p, int wake_flags)
{
    struct rq *rq;
    int ret = 0;

    rq = __task_rq_lock(p);
    if (p->on_rq) {
        ttwu_do_wakeup(rq, p, wake_flags);
        ret = 1;
    }
    __task_rq_unlock(rq);

    return ret;
}

#ifdef CONFIG_SMP
static void sched_ttwu_pending(void)
{
    struct rq *rq = this_rq();
    struct llist_node *llist = llist_del_all(&rq->wake_list);
    struct task_struct *p;

    raw_spin_lock(&rq->lock);

    while (llist) {
        p = llist_entry(llist, struct task_struct, wake_entry);
        llist = llist_next(llist);
        ttwu_do_activate(rq, p, 0);
    }

    raw_spin_unlock(&rq->lock);
}

void scheduler_ipi(void)
{
    if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick())
        return;

    /*
     * Not all reschedule IPI handlers call irq_enter/irq_exit, since
     * traditionally all their work was done from the interrupt return
     * path. Now that we actually do some work, we need to make sure
     * we do call them.
     *
     * Some archs already do call them, luckily irq_enter/exit nest
     * properly.
     *
     * Arguably we should visit all archs and update all handlers,
     * however a fair share of IPIs are still resched only so this would
     * somewhat pessimize the simple resched case.
     */
    irq_enter();
    sched_ttwu_pending();

    /*
     * Check if someone kicked us for doing the nohz idle load balance.
     */
    if (unlikely(got_nohz_idle_kick() && !need_resched())) {
        this_rq()->idle_balance = 1;
        raise_softirq_irqoff(SCHED_SOFTIRQ);
    }
    irq_exit();
}

static void ttwu_queue_remote(struct task_struct *p, int cpu)
{
    if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list))
        smp_send_reschedule(cpu);
}

bool cpus_share_cache(int this_cpu, int that_cpu)
{
    return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
}
#endif /* CONFIG_SMP */

static void ttwu_queue(struct task_struct *p, int cpu)
{
    struct rq *rq = cpu_rq(cpu);

#if defined(CONFIG_SMP)
    if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) {
        sched_clock_cpu(cpu); /* sync clocks x-cpu */
        ttwu_queue_remote(p, cpu);
        return;
    }
#endif

    raw_spin_lock(&rq->lock);
    ttwu_do_activate(rq, p, 0);
    raw_spin_unlock(&rq->lock);
}

static int
try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
{
    unsigned long flags;
    int cpu, success = 0;

    smp_wmb();
    raw_spin_lock_irqsave(&p->pi_lock, flags);
    if (!(p->state & state))
        goto out;

    success = 1; /* we're going to change ->state */
    cpu = task_cpu(p);

    if (p->on_rq && ttwu_remote(p, wake_flags))
        goto stat;

#ifdef CONFIG_SMP
    /*
     * If the owning (remote) cpu is still in the middle of schedule() with
     * this task as prev, wait until its done referencing the task.
     */
    while (p->on_cpu)
        cpu_relax();
    /*
     * Pairs with the smp_wmb() in finish_lock_switch().
     */
    smp_rmb();

    p->sched_contributes_to_load = !!task_contributes_to_load(p);
    p->state = TASK_WAKING;

    if (p->sched_class->task_waking)
        p->sched_class->task_waking(p);

    cpu = select_task_rq(p, SD_BALANCE_WAKE, wake_flags);
    if (task_cpu(p) != cpu) {
        wake_flags |= WF_MIGRATED;
        set_task_cpu(p, cpu);
    }
#endif /* CONFIG_SMP */

    ttwu_queue(p, cpu);
stat:
    ttwu_stat(p, cpu, wake_flags);
out:
    raw_spin_unlock_irqrestore(&p->pi_lock, flags);

    return success;
}

static void try_to_wake_up_local(struct task_struct *p)
{
    struct rq *rq = task_rq(p);

    BUG_ON(rq != this_rq());
    BUG_ON(p == current);
    lockdep_assert_held(&rq->lock);

    if (!raw_spin_trylock(&p->pi_lock)) {
        raw_spin_unlock(&rq->lock);
        raw_spin_lock(&p->pi_lock);
        raw_spin_lock(&rq->lock);
    }

    if (!(p->state & TASK_NORMAL))
        goto out;

    if (!p->on_rq)
        ttwu_activate(rq, p, ENQUEUE_WAKEUP);

    ttwu_do_wakeup(rq, p, 0);
    ttwu_stat(p, smp_processor_id(), 0);
out:
    raw_spin_unlock(&p->pi_lock);
}

int wake_up_process(struct task_struct *p)
{
    return try_to_wake_up(p, TASK_ALL, 0);
}
EXPORT_SYMBOL(wake_up_process);

int wake_up_state(struct task_struct *p, unsigned int state)
{
    return try_to_wake_up(p, state, 0);
}

/*
 * Perform scheduler related setup for a newly forked process p.
 * p is forked by current.
 *
 * __sched_fork() is basic setup used by init_idle() too:
 */
static void __sched_fork(struct task_struct *p)
{
    p->on_rq            = 0;

    p->se.on_rq         = 0;
    p->se.exec_start        = 0;
    p->se.sum_exec_runtime      = 0;
    p->se.prev_sum_exec_runtime = 0;
    p->se.nr_migrations     = 0;
    p->se.vruntime          = 0;
    INIT_LIST_HEAD(&p->se.group_node);

#ifdef CONFIG_SCHEDSTATS
    memset(&p->se.statistics, 0, sizeof(p->se.statistics));
#endif

    INIT_LIST_HEAD(&p->rt.run_list);

#ifdef CONFIG_PREEMPT_NOTIFIERS
    INIT_HLIST_HEAD(&p->preempt_notifiers);
#endif
}

/*
 * fork()/clone()-time setup:
 */
void sched_fork(struct task_struct *p)
{
    unsigned long flags;
    int cpu = get_cpu();

    __sched_fork(p);
    /*
     * We mark the process as running here. This guarantees that
     * nobody will actually run it, and a signal or other external
     * event cannot wake it up and insert it on the runqueue either.
     */
    p->state = TASK_RUNNING;

    /*
     * Make sure we do not leak PI boosting priority to the child.
     */
    p->prio = current->normal_prio;

    /*
     * Revert to default priority/policy on fork if requested.
     */
    if (unlikely(p->sched_reset_on_fork)) {
        if (task_has_rt_policy(p)) {
            p->policy = SCHED_NORMAL;
            p->static_prio = NICE_TO_PRIO(0);
            p->rt_priority = 0;
        } else if (PRIO_TO_NICE(p->static_prio) < 0)
            p->static_prio = NICE_TO_PRIO(0);

        p->prio = p->normal_prio = __normal_prio(p);
        set_load_weight(p);

        /*
         * We don't need the reset flag anymore after the fork. It has
         * fulfilled its duty:
         */
        p->sched_reset_on_fork = 0;
    }

    if (!rt_prio(p->prio))
        p->sched_class = &fair_sched_class;

    if (p->sched_class->task_fork)
        p->sched_class->task_fork(p);

    /*
     * The child is not yet in the pid-hash so no cgroup attach races,
     * and the cgroup is pinned to this child due to cgroup_fork()
     * is ran before sched_fork().
     *
     * Silence PROVE_RCU.
     */
    raw_spin_lock_irqsave(&p->pi_lock, flags);
    set_task_cpu(p, cpu);
    raw_spin_unlock_irqrestore(&p->pi_lock, flags);

#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
    if (likely(sched_info_on()))
        memset(&p->sched_info, 0, sizeof(p->sched_info));
#endif
#if defined(CONFIG_SMP)
    p->on_cpu = 0;
#endif
#ifdef CONFIG_PREEMPT_COUNT
    /* Want to start with kernel preemption disabled. */
    task_thread_info(p)->preempt_count = 1;
#endif
#ifdef CONFIG_SMP
    plist_node_init(&p->pushable_tasks, MAX_PRIO);
#endif

    put_cpu();
}

/*
 * wake_up_new_task - wake up a newly created task for the first time.
 *
 * This function will do some initial scheduler statistics housekeeping
 * that must be done for every newly created context, then puts the task
 * on the runqueue and wakes it.
 */
void wake_up_new_task(struct task_struct *p)
{
    unsigned long flags;
    struct rq *rq;

    raw_spin_lock_irqsave(&p->pi_lock, flags);
#ifdef CONFIG_SMP
    /*
     * Fork balancing, do it here and not earlier because:
     *  - cpus_allowed can change in the fork path
     *  - any previously selected cpu might disappear through hotplug
     */
    set_task_cpu(p, select_task_rq(p, SD_BALANCE_FORK, 0));
#endif

    rq = __task_rq_lock(p);
    activate_task(rq, p, 0);
    p->on_rq = 1;
    trace_sched_wakeup_new(p, true);
    check_preempt_curr(rq, p, WF_FORK);
#ifdef CONFIG_SMP
    if (p->sched_class->task_woken)
        p->sched_class->task_woken(rq, p);
#endif
    task_rq_unlock(rq, p, &flags);
}

#ifdef CONFIG_PREEMPT_NOTIFIERS

void preempt_notifier_register(struct preempt_notifier *notifier)
{
    hlist_add_head(&notifier->link, &current->preempt_notifiers);
}
EXPORT_SYMBOL_GPL(preempt_notifier_register);

void preempt_notifier_unregister(struct preempt_notifier *notifier)
{
    hlist_del(&notifier->link);
}
EXPORT_SYMBOL_GPL(preempt_notifier_unregister);

static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
{
    struct preempt_notifier *notifier;
    struct hlist_node *node;

    hlist_for_each_entry(notifier, node, &curr->preempt_notifiers, link)
        notifier->ops->sched_in(notifier, raw_smp_processor_id());
}

static void
fire_sched_out_preempt_notifiers(struct task_struct *curr,
                 struct task_struct *next)
{
    struct preempt_notifier *notifier;
    struct hlist_node *node;

    hlist_for_each_entry(notifier, node, &curr->preempt_notifiers, link)
        notifier->ops->sched_out(notifier, next);
}

#else /* !CONFIG_PREEMPT_NOTIFIERS */

static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
{
}

static void
fire_sched_out_preempt_notifiers(struct task_struct *curr,
                 struct task_struct *next)
{
}

#endif /* CONFIG_PREEMPT_NOTIFIERS */

static inline void
prepare_task_switch(struct rq *rq, struct task_struct *prev,
            struct task_struct *next)
{
    trace_sched_switch(prev, next);
    sched_info_switch(prev, next);
    perf_event_task_sched_out(prev, next);
    fire_sched_out_preempt_notifiers(prev, next);
    prepare_lock_switch(rq, next);
    prepare_arch_switch(next);
}

static void finish_task_switch(struct rq *rq, struct task_struct *prev)
    __releases(rq->lock)
{
    struct mm_struct *mm = rq->prev_mm;
    long prev_state;

    rq->prev_mm = NULL;

    /*
     * A task struct has one reference for the use as "current".
     * If a task dies, then it sets TASK_DEAD in tsk->state and calls
     * schedule one last time. The schedule call will never return, and
     * the scheduled task must drop that reference.
     * The test for TASK_DEAD must occur while the runqueue locks are
     * still held, otherwise prev could be scheduled on another cpu, die
     * there before we look at prev->state, and then the reference would
     * be dropped twice.
     *      Manfred Spraul <[email protected]>
     */
    prev_state = prev->state;
    vtime_task_switch(prev);
    finish_arch_switch(prev);
    perf_event_task_sched_in(prev, current);
    finish_lock_switch(rq, prev);
    finish_arch_post_lock_switch();

    fire_sched_in_preempt_notifiers(current);
    if (mm)
        mmdrop(mm);
    if (unlikely(prev_state == TASK_DEAD)) {
        /*
         * Remove function-return probe instances associated with this
         * task and put them back on the free list.
         */
        kprobe_flush_task(prev);
        put_task_struct(prev);
    }
}

#ifdef CONFIG_SMP

/* assumes rq->lock is held */
static inline void pre_schedule(struct rq *rq, struct task_struct *prev)
{
    if (prev->sched_class->pre_schedule)
        prev->sched_class->pre_schedule(rq, prev);
}

/* rq->lock is NOT held, but preemption is disabled */
static inline void post_schedule(struct rq *rq)
{
    if (rq->post_schedule) {
        unsigned long flags;

        raw_spin_lock_irqsave(&rq->lock, flags);
        if (rq->curr->sched_class->post_schedule)
            rq->curr->sched_class->post_schedule(rq);
        raw_spin_unlock_irqrestore(&rq->lock, flags);

        rq->post_schedule = 0;
    }
}

#else

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

static inline void post_schedule(struct rq *rq)
{
}

#endif

asmlinkage void schedule_tail(struct task_struct *prev)
    __releases(rq->lock)
{
    struct rq *rq = this_rq();

    finish_task_switch(rq, prev);

    /*
     * FIXME: do we need to worry about rq being invalidated by the
     * task_switch?
     */
    post_schedule(rq);

#ifdef __ARCH_WANT_UNLOCKED_CTXSW
    /* In this case, finish_task_switch does not reenable preemption */
    preempt_enable();
#endif
    if (current->set_child_tid)
        put_user(task_pid_vnr(current), current->set_child_tid);
}

/*
 * context_switch - switch to the new MM and the new
 * thread's register state.
 */
static inline void
context_switch(struct rq *rq, struct task_struct *prev,
           struct task_struct *next)
{
    struct mm_struct *mm, *oldmm;

    prepare_task_switch(rq, prev, next);

    mm = next->mm;
    oldmm = prev->active_mm;
    /*
     * For paravirt, this is coupled with an exit in switch_to to
     * combine the page table reload and the switch backend into
     * one hypercall.
     */
    arch_start_context_switch(prev);

    if (!mm) {
        next->active_mm = oldmm;
        atomic_inc(&oldmm->mm_count);
        enter_lazy_tlb(oldmm, next);
    } else
        switch_mm(oldmm, mm, next);

    if (!prev->mm) {
        prev->active_mm = NULL;
        rq->prev_mm = oldmm;
    }
    /*
     * Since the runqueue lock will be released by the next
     * task (which is an invalid locking op but in the case
     * of the scheduler it's an obvious special-case), so we
     * do an early lockdep release here:
     */
#ifndef __ARCH_WANT_UNLOCKED_CTXSW
    spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
#endif

    /* Here we just switch the register state and the stack. */
    rcu_switch(prev, next);
    switch_to(prev, next, prev);

    barrier();
    /*
     * this_rq must be evaluated again because prev may have moved
     * CPUs since it called schedule(), thus the 'rq' on its stack
     * frame will be invalid.
     */
    finish_task_switch(this_rq(), prev);
}

/*
 * nr_running, nr_uninterruptible and nr_context_switches:
 *
 * externally visible scheduler statistics: current number of runnable
 * threads, current number of uninterruptible-sleeping threads, total
 * number of context switches performed since bootup.
 */
unsigned long nr_running(void)
{
    unsigned long i, sum = 0;

    for_each_online_cpu(i)
        sum += cpu_rq(i)->nr_running;

    return sum;
}

unsigned long nr_uninterruptible(void)
{
    unsigned long i, sum = 0;

    for_each_possible_cpu(i)
        sum += cpu_rq(i)->nr_uninterruptible;

    /*
     * Since we read the counters lockless, it might be slightly
     * inaccurate. Do not allow it to go below zero though:
     */
    if (unlikely((long)sum < 0))
        sum = 0;

    return sum;
}

unsigned long long nr_context_switches(void)
{
    int i;
    unsigned long long sum = 0;

    for_each_possible_cpu(i)
        sum += cpu_rq(i)->nr_switches;

    return sum;
}

unsigned long nr_iowait(void)
{
    unsigned long i, sum = 0;

    for_each_possible_cpu(i)
        sum += atomic_read(&cpu_rq(i)->nr_iowait);

    return sum;
}

unsigned long nr_iowait_cpu(int cpu)
{
    struct rq *this = cpu_rq(cpu);
    return atomic_read(&this->nr_iowait);
}

unsigned long this_cpu_load(void)
{
    struct rq *this = this_rq();
    return this->cpu_load[0];
}


/*
 * Global load-average calculations
 *
 * We take a distributed and async approach to calculating the global load-avg
 * in order to minimize overhead.
 *
 * The global load average is an exponentially decaying average of nr_running +
 * nr_uninterruptible.
 *
 * Once every LOAD_FREQ:
 *
 *   nr_active = 0;
 *   for_each_possible_cpu(cpu)
 *      nr_active += cpu_of(cpu)->nr_running + cpu_of(cpu)->nr_uninterruptible;
 *
 *   avenrun[n] = avenrun[0] * exp_n + nr_active * (1 - exp_n)
 *
 * Due to a number of reasons the above turns in the mess below:
 *
 *  - for_each_possible_cpu() is prohibitively expensive on machines with
 *    serious number of cpus, therefore we need to take a distributed approach
 *    to calculating nr_active.
 *
 *        \Sum_i x_i(t) = \Sum_i x_i(t) - x_i(t_0) | x_i(t_0) := 0
 *                      = \Sum_i { \Sum_j=1 x_i(t_j) - x_i(t_j-1) }
 *
 *    So assuming nr_active := 0 when we start out -- true per definition, we
 *    can simply take per-cpu deltas and fold those into a global accumulate
 *    to obtain the same result. See calc_load_fold_active().
 *
 *    Furthermore, in order to avoid synchronizing all per-cpu delta folding
 *    across the machine, we assume 10 ticks is sufficient time for every
 *    cpu to have completed this task.
 *
 *    This places an upper-bound on the IRQ-off latency of the machine. Then
 *    again, being late doesn't loose the delta, just wrecks the sample.
 *
 *  - cpu_rq()->nr_uninterruptible isn't accurately tracked per-cpu because
 *    this would add another cross-cpu cacheline miss and atomic operation
 *    to the wakeup path. Instead we increment on whatever cpu the task ran
 *    when it went into uninterruptible state and decrement on whatever cpu
 *    did the wakeup. This means that only the sum of nr_uninterruptible over
 *    all cpus yields the correct result.
 *
 *  This covers the NO_HZ=n code, for extra head-aches, see the comment below.
 */

/* Variables and functions for calc_load */
static atomic_long_t calc_load_tasks;
static unsigned long calc_load_update;
unsigned long avenrun[3];
EXPORT_SYMBOL(avenrun); /* should be removed */

void get_avenrun(unsigned long *loads, unsigned long offset, int shift)
{
    loads[0] = (avenrun[0] + offset) << shift;
    loads[1] = (avenrun[1] + offset) << shift;
    loads[2] = (avenrun[2] + offset) << shift;
}

static long calc_load_fold_active(struct rq *this_rq)
{
    long nr_active, delta = 0;

    nr_active = this_rq->nr_running;
    nr_active += (long) this_rq->nr_uninterruptible;

    if (nr_active != this_rq->calc_load_active) {
        delta = nr_active - this_rq->calc_load_active;
        this_rq->calc_load_active = nr_active;
    }

    return delta;
}

/*
 * a1 = a0 * e + a * (1 - e)
 */
static unsigned long
calc_load(unsigned long load, unsigned long exp, unsigned long active)
{
    load *= exp;
    load += active * (FIXED_1 - exp);
    load += 1UL << (FSHIFT - 1);
    return load >> FSHIFT;
}

#ifdef CONFIG_NO_HZ
/*
 * Handle NO_HZ for the global load-average.
 *
 * Since the above described distributed algorithm to compute the global
 * load-average relies on per-cpu sampling from the tick, it is affected by
 * NO_HZ.
 *
 * The basic idea is to fold the nr_active delta into a global idle-delta upon
 * entering NO_HZ state such that we can include this as an 'extra' cpu delta
 * when we read the global state.
 *
 * Obviously reality has to ruin such a delightfully simple scheme:
 *
 *  - When we go NO_HZ idle during the window, we can negate our sample
 *    contribution, causing under-accounting.
 *
 *    We avoid this by keeping two idle-delta counters and flipping them
 *    when the window starts, thus separating old and new NO_HZ load.
 *
 *    The only trick is the slight shift in index flip for read vs write.
 *
 *        0s            5s            10s           15s
 *          +10           +10           +10           +10
 *        |-|-----------|-|-----------|-|-----------|-|
 *    r:0 0 1           1 0           0 1           1 0
 *    w:0 1 1           0 0           1 1           0 0
 *
 *    This ensures we'll fold the old idle contribution in this window while
 *    accumlating the new one.
 *
 *  - When we wake up from NO_HZ idle during the window, we push up our
 *    contribution, since we effectively move our sample point to a known
 *    busy state.
 *
 *    This is solved by pushing the window forward, and thus skipping the
 *    sample, for this cpu (effectively using the idle-delta for this cpu which
 *    was in effect at the time the window opened). This also solves the issue
 *    of having to deal with a cpu having been in NOHZ idle for multiple
 *    LOAD_FREQ intervals.
 *
 * When making the ILB scale, we should try to pull this in as well.
 */
static atomic_long_t calc_load_idle[2];
static int calc_load_idx;

static inline int calc_load_write_idx(void)
{
    int idx = calc_load_idx;

    /*
     * See calc_global_nohz(), if we observe the new index, we also
     * need to observe the new update time.
     */
    smp_rmb();

    /*
     * If the folding window started, make sure we start writing in the
     * next idle-delta.
     */
    if (!time_before(jiffies, calc_load_update))
        idx++;

    return idx & 1;
}

static inline int calc_load_read_idx(void)
{
    return calc_load_idx & 1;
}

void calc_load_enter_idle(void)
{
    struct rq *this_rq = this_rq();
    long delta;

    /*
     * We're going into NOHZ mode, if there's any pending delta, fold it
     * into the pending idle delta.
     */
    delta = calc_load_fold_active(this_rq);
    if (delta) {
        int idx = calc_load_write_idx();
        atomic_long_add(delta, &calc_load_idle[idx]);
    }
}

void calc_load_exit_idle(void)
{
    struct rq *this_rq = this_rq();

    /*
     * If we're still before the sample window, we're done.
     */
    if (time_before(jiffies, this_rq->calc_load_update))
        return;

    /*
     * We woke inside or after the sample window, this means we're already
     * accounted through the nohz accounting, so skip the entire deal and
     * sync up for the next window.
     */
    this_rq->calc_load_update = calc_load_update;
    if (time_before(jiffies, this_rq->calc_load_update + 10))
        this_rq->calc_load_update += LOAD_FREQ;
}

static long calc_load_fold_idle(void)
{
    int idx = calc_load_read_idx();
    long delta = 0;

    if (atomic_long_read(&calc_load_idle[idx]))
        delta = atomic_long_xchg(&calc_load_idle[idx], 0);

    return delta;
}

static unsigned long
fixed_power_int(unsigned long x, unsigned int frac_bits, unsigned int n)
{
    unsigned long result = 1UL << frac_bits;

    if (n) for (;;) {
        if (n & 1) {
            result *= x;
            result += 1UL << (frac_bits - 1);
            result >>= frac_bits;
        }
        n >>= 1;
        if (!n)
            break;
        x *= x;
        x += 1UL << (frac_bits - 1);
        x >>= frac_bits;
    }

    return result;
}

/*
 * a1 = a0 * e + a * (1 - e)
 *
 * a2 = a1 * e + a * (1 - e)
 *    = (a0 * e + a * (1 - e)) * e + a * (1 - e)
 *    = a0 * e^2 + a * (1 - e) * (1 + e)
 *
 * a3 = a2 * e + a * (1 - e)
 *    = (a0 * e^2 + a * (1 - e) * (1 + e)) * e + a * (1 - e)
 *    = a0 * e^3 + a * (1 - e) * (1 + e + e^2)
 *
 *  ...
 *
 * an = a0 * e^n + a * (1 - e) * (1 + e + ... + e^n-1) [1]
 *    = a0 * e^n + a * (1 - e) * (1 - e^n)/(1 - e)
 *    = a0 * e^n + a * (1 - e^n)
 *
 * [1] application of the geometric series:
 *
 *              n         1 - x^(n+1)
 *     S_n := \Sum x^i = -------------
 *             i=0          1 - x
 */
static unsigned long
calc_load_n(unsigned long load, unsigned long exp,
        unsigned long active, unsigned int n)
{

    return calc_load(load, fixed_power_int(exp, FSHIFT, n), active);
}

/*
 * NO_HZ can leave us missing all per-cpu ticks calling
 * calc_load_account_active(), but since an idle CPU folds its delta into
 * calc_load_tasks_idle per calc_load_account_idle(), all we need to do is fold
 * in the pending idle delta if our idle period crossed a load cycle boundary.
 *
 * Once we've updated the global active value, we need to apply the exponential
 * weights adjusted to the number of cycles missed.
 */
static void calc_global_nohz(void)
{
    long delta, active, n;

    if (!time_before(jiffies, calc_load_update + 10)) {
        /*
         * Catch-up, fold however many we are behind still
         */
        delta = jiffies - calc_load_update - 10;
        n = 1 + (delta / LOAD_FREQ);

        active = atomic_long_read(&calc_load_tasks);
        active = active > 0 ? active * FIXED_1 : 0;

        avenrun[0] = calc_load_n(avenrun[0], EXP_1, active, n);
        avenrun[1] = calc_load_n(avenrun[1], EXP_5, active, n);
        avenrun[2] = calc_load_n(avenrun[2], EXP_15, active, n);

        calc_load_update += n * LOAD_FREQ;
    }

    /*
     * Flip the idle index...
     *
     * Make sure we first write the new time then flip the index, so that
     * calc_load_write_idx() will see the new time when it reads the new
     * index, this avoids a double flip messing things up.
     */
    smp_wmb();
    calc_load_idx++;
}
#else /* !CONFIG_NO_HZ */

static inline long calc_load_fold_idle(void) { return 0; }
static inline void calc_global_nohz(void) { }

#endif /* CONFIG_NO_HZ */

/*
 * calc_load - update the avenrun load estimates 10 ticks after the
 * CPUs have updated calc_load_tasks.
 */
void calc_global_load(unsigned long ticks)
{
    long active, delta;

    if (time_before(jiffies, calc_load_update + 10))
        return;

    /*
     * Fold the 'old' idle-delta to include all NO_HZ cpus.
     */
    delta = calc_load_fold_idle();
    if (delta)
        atomic_long_add(delta, &calc_load_tasks);

    active = atomic_long_read(&calc_load_tasks);
    active = active > 0 ? active * FIXED_1 : 0;

    avenrun[0] = calc_load(avenrun[0], EXP_1, active);
    avenrun[1] = calc_load(avenrun[1], EXP_5, active);
    avenrun[2] = calc_load(avenrun[2], EXP_15, active);

    calc_load_update += LOAD_FREQ;

    /*
     * In case we idled for multiple LOAD_FREQ intervals, catch up in bulk.
     */
    calc_global_nohz();
}

/*
 * Called from update_cpu_load() to periodically update this CPU's
 * active count.
 */
static void calc_load_account_active(struct rq *this_rq)
{
    long delta;

    if (time_before(jiffies, this_rq->calc_load_update))
        return;

    delta  = calc_load_fold_active(this_rq);
    if (delta)
        atomic_long_add(delta, &calc_load_tasks);

    this_rq->calc_load_update += LOAD_FREQ;
}

/*
 * End of global load-average stuff
 */

/*
 * The exact cpuload at various idx values, calculated at every tick would be
 * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
 *
 * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
 * on nth tick when cpu may be busy, then we have:
 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
 * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
 *
 * decay_load_missed() below does efficient calculation of
 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
 * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
 *
 * The calculation is approximated on a 128 point scale.
 * degrade_zero_ticks is the number of ticks after which load at any
 * particular idx is approximated to be zero.
 * degrade_factor is a precomputed table, a row for each load idx.
 * Each column corresponds to degradation factor for a power of two ticks,
 * based on 128 point scale.
 * Example:
 * row 2, col 3 (=12) says that the degradation at load idx 2 after
 * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
 *
 * With this power of 2 load factors, we can degrade the load n times
 * by looking at 1 bits in n and doing as many mult/shift instead of
 * n mult/shifts needed by the exact degradation.
 */
#define DEGRADE_SHIFT       7
static const unsigned char
        degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
static const unsigned char
        degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
                    {0, 0, 0, 0, 0, 0, 0, 0},
                    {64, 32, 8, 0, 0, 0, 0, 0},
                    {96, 72, 40, 12, 1, 0, 0},
                    {112, 98, 75, 43, 15, 1, 0},
                    {120, 112, 98, 76, 45, 16, 2} };

/*
 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
 * would be when CPU is idle and so we just decay the old load without
 * adding any new load.
 */
static unsigned long
decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
{
    int j = 0;

    if (!missed_updates)
        return load;

    if (missed_updates >= degrade_zero_ticks[idx])
        return 0;

    if (idx == 1)
        return load >> missed_updates;

    while (missed_updates) {
        if (missed_updates % 2)
            load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;

        missed_updates >>= 1;
        j++;
    }
    return load;
}

/*
 * Update rq->cpu_load[] statistics. This function is usually called every
 * scheduler tick (TICK_NSEC). With tickless idle this will not be called
 * every tick. We fix it up based on jiffies.
 */
static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
                  unsigned long pending_updates)
{
    int i, scale;

    this_rq->nr_load_updates++;

    /* Update our load: */
    this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
    for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
        unsigned long old_load, new_load;

        /* scale is effectively 1 << i now, and >> i divides by scale */

        old_load = this_rq->cpu_load[i];
        old_load = decay_load_missed(old_load, pending_updates - 1, i);
        new_load = this_load;
        /*
         * Round up the averaging division if load is increasing. This
         * prevents us from getting stuck on 9 if the load is 10, for
         * example.
         */
        if (new_load > old_load)
            new_load += scale - 1;

        this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
    }

    sched_avg_update(this_rq);
}

#ifdef CONFIG_NO_HZ
/*
 * There is no sane way to deal with nohz on smp when using jiffies because the
 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
 *
 * Therefore we cannot use the delta approach from the regular tick since that
 * would seriously skew the load calculation. However we'll make do for those
 * updates happening while idle (nohz_idle_balance) or coming out of idle
 * (tick_nohz_idle_exit).
 *
 * This means we might still be one tick off for nohz periods.
 */

/*
 * Called from nohz_idle_balance() to update the load ratings before doing the
 * idle balance.
 */
void update_idle_cpu_load(struct rq *this_rq)
{
    unsigned long curr_jiffies = ACCESS_ONCE(jiffies);
    unsigned long load = this_rq->load.weight;
    unsigned long pending_updates;

    /*
     * bail if there's load or we're actually up-to-date.
     */
    if (load || curr_jiffies == this_rq->last_load_update_tick)
        return;

    pending_updates = curr_jiffies - this_rq->last_load_update_tick;
    this_rq->last_load_update_tick = curr_jiffies;

    __update_cpu_load(this_rq, load, pending_updates);
}

/*
 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
 */
void update_cpu_load_nohz(void)
{
    struct rq *this_rq = this_rq();
    unsigned long curr_jiffies = ACCESS_ONCE(jiffies);
    unsigned long pending_updates;

    if (curr_jiffies == this_rq->last_load_update_tick)
        return;

    raw_spin_lock(&this_rq->lock);
    pending_updates = curr_jiffies - this_rq->last_load_update_tick;
    if (pending_updates) {
        this_rq->last_load_update_tick = curr_jiffies;
        /*
         * We were idle, this means load 0, the current load might be
         * !0 due to remote wakeups and the sort.
         */
        __update_cpu_load(this_rq, 0, pending_updates);
    }
    raw_spin_unlock(&this_rq->lock);
}
#endif /* CONFIG_NO_HZ */

/*
 * Called from scheduler_tick()
 */
static void update_cpu_load_active(struct rq *this_rq)
{
    /*
     * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
     */
    this_rq->last_load_update_tick = jiffies;
    __update_cpu_load(this_rq, this_rq->load.weight, 1);

    calc_load_account_active(this_rq);
}

#ifdef CONFIG_SMP

/*
 * sched_exec - execve() is a valuable balancing opportunity, because at
 * this point the task has the smallest effective memory and cache footprint.
 */
void sched_exec(void)
{
    struct task_struct *p = current;
    unsigned long flags;
    int dest_cpu;

    raw_spin_lock_irqsave(&p->pi_lock, flags);
    dest_cpu = p->sched_class->select_task_rq(p, SD_BALANCE_EXEC, 0);
    if (dest_cpu == smp_processor_id())
        goto unlock;

    if (likely(cpu_active(dest_cpu))) {
        struct migration_arg arg = { p, dest_cpu };

        raw_spin_unlock_irqrestore(&p->pi_lock, flags);
        stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
        return;
    }
unlock:
    raw_spin_unlock_irqrestore(&p->pi_lock, flags);
}

#endif

DEFINE_PER_CPU(struct kernel_stat, kstat);
DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);

EXPORT_PER_CPU_SYMBOL(kstat);
EXPORT_PER_CPU_SYMBOL(kernel_cpustat);

/*
 * Return any ns on the sched_clock that have not yet been accounted in
 * @p in case that task is currently running.
 *
 * Called with task_rq_lock() held on @rq.
 */
static u64 do_task_delta_exec(struct task_struct *p, struct rq *rq)
{
    u64 ns = 0;

    if (task_current(rq, p)) {
        update_rq_clock(rq);
        ns = rq->clock_task - p->se.exec_start;
        if ((s64)ns < 0)
            ns = 0;
    }

    return ns;
}

unsigned long long task_delta_exec(struct task_struct *p)
{
    unsigned long flags;
    struct rq *rq;
    u64 ns = 0;

    rq = task_rq_lock(p, &flags);
    ns = do_task_delta_exec(p, rq);
    task_rq_unlock(rq, p, &flags);

    return ns;
}

/*
 * Return accounted runtime for the task.
 * In case the task is currently running, return the runtime plus current's
 * pending runtime that have not been accounted yet.
 */
unsigned long long task_sched_runtime(struct task_struct *p)
{
    unsigned long flags;
    struct rq *rq;
    u64 ns = 0;

    rq = task_rq_lock(p, &flags);
    ns = p->se.sum_exec_runtime + do_task_delta_exec(p, rq);
    task_rq_unlock(rq, p, &flags);

    return ns;
}

/*
 * This function gets called by the timer code, with HZ frequency.
 * We call it with interrupts disabled.
 */
void scheduler_tick(void)
{
    int cpu = smp_processor_id();
    struct rq *rq = cpu_rq(cpu);
    struct task_struct *curr = rq->curr;

    sched_clock_tick();

    raw_spin_lock(&rq->lock);
    update_rq_clock(rq);
    update_cpu_load_active(rq);
    curr->sched_class->task_tick(rq, curr, 0);
    raw_spin_unlock(&rq->lock);

    perf_event_task_tick();

#ifdef CONFIG_SMP
    rq->idle_balance = idle_cpu(cpu);
    trigger_load_balance(rq, cpu);
#endif
}

notrace unsigned long get_parent_ip(unsigned long addr)
{
    if (in_lock_functions(addr)) {
        addr = CALLER_ADDR2;
        if (in_lock_functions(addr))
            addr = CALLER_ADDR3;
    }
    return addr;
}

#if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
                defined(CONFIG_PREEMPT_TRACER))

void __kprobes add_preempt_count(int val)
{
#ifdef CONFIG_DEBUG_PREEMPT
    /*
     * Underflow?
     */
    if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
        return;
#endif
    preempt_count() += val;
#ifdef CONFIG_DEBUG_PREEMPT
    /*
     * Spinlock count overflowing soon?
     */
    DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
                PREEMPT_MASK - 10);
#endif
    if (preempt_count() == val)
        trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
}
EXPORT_SYMBOL(add_preempt_count);

void __kprobes sub_preempt_count(int val)
{
#ifdef CONFIG_DEBUG_PREEMPT
    /*
     * Underflow?
     */
    if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
        return;
    /*
     * Is the spinlock portion underflowing?
     */
    if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
            !(preempt_count() & PREEMPT_MASK)))
        return;
#endif

    if (preempt_count() == val)
        trace_preempt_on(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
    preempt_count() -= val;
}
EXPORT_SYMBOL(sub_preempt_count);

#endif

/*
 * Print scheduling while atomic bug:
 */
static noinline void __schedule_bug(struct task_struct *prev)
{
    if (oops_in_progress)
        return;

    printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
        prev->comm, prev->pid, preempt_count());

    debug_show_held_locks(prev);
    print_modules();
    if (irqs_disabled())
        print_irqtrace_events(prev);
    dump_stack();
    add_taint(TAINT_WARN);
}

/*
 * Various schedule()-time debugging checks and statistics:
 */
static inline void schedule_debug(struct task_struct *prev)
{
    /*
     * Test if we are atomic. Since do_exit() needs to call into
     * schedule() atomically, we ignore that path for now.
     * Otherwise, whine if we are scheduling when we should not be.
     */
    if (unlikely(in_atomic_preempt_off() && !prev->exit_state))
        __schedule_bug(prev);
    rcu_sleep_check();

    profile_hit(SCHED_PROFILING, __builtin_return_address(0));

    schedstat_inc(this_rq(), sched_count);
}

static void put_prev_task(struct rq *rq, struct task_struct *prev)
{
    if (prev->on_rq || rq->skip_clock_update < 0)
        update_rq_clock(rq);
    prev->sched_class->put_prev_task(rq, prev);
}

/*
 * Pick up the highest-prio task:
 */
static inline struct task_struct *
pick_next_task(struct rq *rq)
{
    const struct sched_class *class;
    struct task_struct *p;

    /*
     * Optimization: we know that if all tasks are in
     * the fair class we can call that function directly:
     */
    if (likely(rq->nr_running == rq->cfs.h_nr_running)) {
        p = fair_sched_class.pick_next_task(rq);
        if (likely(p))
            return p;
    }

    for_each_class(class) {
        p = class->pick_next_task(rq);
        if (p)
            return p;
    }

    BUG(); /* the idle class will always have a runnable task */
}

/*
 * __schedule() is the main scheduler function.
 *
 * The main means of driving the scheduler and thus entering this function are:
 *
 *   1. Explicit blocking: mutex, semaphore, waitqueue, etc.
 *
 *   2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
 *      paths. For example, see arch/x86/entry_64.S.
 *
 *      To drive preemption between tasks, the scheduler sets the flag in timer
 *      interrupt handler scheduler_tick().
 *
 *   3. Wakeups don't really cause entry into schedule(). They add a
 *      task to the run-queue and that's it.
 *
 *      Now, if the new task added to the run-queue preempts the current
 *      task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
 *      called on the nearest possible occasion:
 *
 *       - If the kernel is preemptible (CONFIG_PREEMPT=y):
 *
 *         - in syscall or exception context, at the next outmost
 *           preempt_enable(). (this might be as soon as the wake_up()'s
 *           spin_unlock()!)
 *
 *         - in IRQ context, return from interrupt-handler to
 *           preemptible context
 *
 *       - If the kernel is not preemptible (CONFIG_PREEMPT is not set)
 *         then at the next:
 *
 *          - cond_resched() call
 *          - explicit schedule() call
 *          - return from syscall or exception to user-space
 *          - return from interrupt-handler to user-space
 */
static void __sched __schedule(void)
{
    struct task_struct *prev, *next;
    unsigned long *switch_count;
    struct rq *rq;
    int cpu;

need_resched:
    preempt_disable();
    cpu = smp_processor_id();
    rq = cpu_rq(cpu);
    rcu_note_context_switch(cpu);
    prev = rq->curr;

    schedule_debug(prev);

    if (sched_feat(HRTICK))
        hrtick_clear(rq);

    raw_spin_lock_irq(&rq->lock);

    switch_count = &prev->nivcsw;
    if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
        if (unlikely(signal_pending_state(prev->state, prev))) {
            prev->state = TASK_RUNNING;
        } else {
            deactivate_task(rq, prev, DEQUEUE_SLEEP);
            prev->on_rq = 0;

            /*
             * If a worker went to sleep, notify and ask workqueue
             * whether it wants to wake up a task to maintain
             * concurrency.
             */
            if (prev->flags & PF_WQ_WORKER) {
                struct task_struct *to_wakeup;

                to_wakeup = wq_worker_sleeping(prev, cpu);
                if (to_wakeup)
                    try_to_wake_up_local(to_wakeup);
            }
        }
        switch_count = &prev->nvcsw;
    }

    pre_schedule(rq, prev);

    if (unlikely(!rq->nr_running))
        idle_balance(cpu, rq);

    put_prev_task(rq, prev);
    next = pick_next_task(rq);
    clear_tsk_need_resched(prev);
    rq->skip_clock_update = 0;

    if (likely(prev != next)) {
        rq->nr_switches++;
        rq->curr = next;
        ++*switch_count;

        context_switch(rq, prev, next); /* unlocks the rq */
        /*
         * The context switch have flipped the stack from under us
         * and restored the local variables which were saved when
         * this task called schedule() in the past. prev == current
         * is still correct, but it can be moved to another cpu/rq.
         */
        cpu = smp_processor_id();
        rq = cpu_rq(cpu);
    } else
        raw_spin_unlock_irq(&rq->lock);

    post_schedule(rq);

    sched_preempt_enable_no_resched();
    if (need_resched())
        goto need_resched;
}

static inline void sched_submit_work(struct task_struct *tsk)
{
    if (!tsk->state || tsk_is_pi_blocked(tsk))
        return;
    /*
     * If we are going to sleep and we have plugged IO queued,
     * make sure to submit it to avoid deadlocks.
     */
    if (blk_needs_flush_plug(tsk))
        blk_schedule_flush_plug(tsk);
}

asmlinkage void __sched schedule(void)
{
    struct task_struct *tsk = current;

    sched_submit_work(tsk);
    __schedule();
}
EXPORT_SYMBOL(schedule);

#ifdef CONFIG_RCU_USER_QS
asmlinkage void __sched schedule_user(void)
{
    /*
     * If we come here after a random call to set_need_resched(),
     * or we have been woken up remotely but the IPI has not yet arrived,
     * we haven't yet exited the RCU idle mode. Do it here manually until
     * we find a better solution.
     */
    rcu_user_exit();
    schedule();
    rcu_user_enter();
}
#endif

void __sched schedule_preempt_disabled(void)
{
    sched_preempt_enable_no_resched();
    schedule();
    preempt_disable();
}

#ifdef CONFIG_MUTEX_SPIN_ON_OWNER

static inline bool owner_running(struct mutex *lock, struct task_struct *owner)
{
    if (lock->owner != owner)
        return false;

    /*
     * Ensure we emit the owner->on_cpu, dereference _after_ checking
     * lock->owner still matches owner, if that fails, owner might
     * point to free()d memory, if it still matches, the rcu_read_lock()
     * ensures the memory stays valid.
     */
    barrier();

    return owner->on_cpu;
}

/*
 * Look out! "owner" is an entirely speculative pointer
 * access and not reliable.
 */
int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
{
    if (!sched_feat(OWNER_SPIN))
        return 0;

    rcu_read_lock();
    while (owner_running(lock, owner)) {
        if (need_resched())
            break;

        arch_mutex_cpu_relax();
    }
    rcu_read_unlock();

    /*
     * We break out the loop above on need_resched() and when the
     * owner changed, which is a sign for heavy contention. Return
     * success only when lock->owner is NULL.
     */
    return lock->owner == NULL;
}
#endif

#ifdef CONFIG_PREEMPT
/*
 * this is the entry point to schedule() from in-kernel preemption
 * off of preempt_enable. Kernel preemptions off return from interrupt
 * occur there and call schedule directly.
 */
asmlinkage void __sched notrace preempt_schedule(void)
{
    struct thread_info *ti = current_thread_info();

    /*
     * If there is a non-zero preempt_count or interrupts are disabled,
     * we do not want to preempt the current task. Just return..
     */
    if (likely(ti->preempt_count || irqs_disabled()))
        return;

    do {
        add_preempt_count_notrace(PREEMPT_ACTIVE);
        __schedule();
        sub_preempt_count_notrace(PREEMPT_ACTIVE);

        /*
         * Check again in case we missed a preemption opportunity
         * between schedule and now.
         */
        barrier();
    } while (need_resched());
}
EXPORT_SYMBOL(preempt_schedule);

/*
 * this is the entry point to schedule() from kernel preemption
 * off of irq context.
 * Note, that this is called and return with irqs disabled. This will
 * protect us against recursive calling from irq.
 */
asmlinkage void __sched preempt_schedule_irq(void)
{
    struct thread_info *ti = current_thread_info();

    /* Catch callers which need to be fixed */
    BUG_ON(ti->preempt_count || !irqs_disabled());

    rcu_user_exit();
    do {
        add_preempt_count(PREEMPT_ACTIVE);
        local_irq_enable();
        __schedule();
        local_irq_disable();
        sub_preempt_count(PREEMPT_ACTIVE);

        /*
         * Check again in case we missed a preemption opportunity
         * between schedule and now.
         */
        barrier();
    } while (need_resched());
}

#endif /* CONFIG_PREEMPT */

int default_wake_function(wait_queue_t *curr, unsigned mode, int wake_flags,
              void *key)
{
    return try_to_wake_up(curr->private, mode, wake_flags);
}
EXPORT_SYMBOL(default_wake_function);

/*
 * The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just
 * wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve
 * number) then we wake all the non-exclusive tasks and one exclusive task.
 *
 * There are circumstances in which we can try to wake a task which has already
 * started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
 * zero in this (rare) case, and we handle it by continuing to scan the queue.
 */
static void __wake_up_common(wait_queue_head_t *q, unsigned int mode,
            int nr_exclusive, int wake_flags, void *key)
{
    wait_queue_t *curr, *next;

    list_for_each_entry_safe(curr, next, &q->task_list, task_list) {
        unsigned flags = curr->flags;

        if (curr->func(curr, mode, wake_flags, key) &&
                (flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive)
            break;
    }
}

void __wake_up(wait_queue_head_t *q, unsigned int mode,
            int nr_exclusive, void *key)
{
    unsigned long flags;

    spin_lock_irqsave(&q->lock, flags);
    __wake_up_common(q, mode, nr_exclusive, 0, key);
    spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(__wake_up);

/*
 * Same as __wake_up but called with the spinlock in wait_queue_head_t held.
 */
void __wake_up_locked(wait_queue_head_t *q, unsigned int mode, int nr)
{
    __wake_up_common(q, mode, nr, 0, NULL);
}
EXPORT_SYMBOL_GPL(__wake_up_locked);

void __wake_up_locked_key(wait_queue_head_t *q, unsigned int mode, void *key)
{
    __wake_up_common(q, mode, 1, 0, key);
}
EXPORT_SYMBOL_GPL(__wake_up_locked_key);

void __wake_up_sync_key(wait_queue_head_t *q, unsigned int mode,
            int nr_exclusive, void *key)
{
    unsigned long flags;
    int wake_flags = WF_SYNC;

    if (unlikely(!q))
        return;

    if (unlikely(!nr_exclusive))
        wake_flags = 0;

    spin_lock_irqsave(&q->lock, flags);
    __wake_up_common(q, mode, nr_exclusive, wake_flags, key);
    spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL_GPL(__wake_up_sync_key);

/*
 * __wake_up_sync - see __wake_up_sync_key()
 */
void __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
{
    __wake_up_sync_key(q, mode, nr_exclusive, NULL);
}
EXPORT_SYMBOL_GPL(__wake_up_sync);  /* For internal use only */

void complete(struct completion *x)
{
    unsigned long flags;

    spin_lock_irqsave(&x->wait.lock, flags);
    x->done++;
    __wake_up_common(&x->wait, TASK_NORMAL, 1, 0, NULL);
    spin_unlock_irqrestore(&x->wait.lock, flags);
}
EXPORT_SYMBOL(complete);

void complete_all(struct completion *x)
{
    unsigned long flags;

    spin_lock_irqsave(&x->wait.lock, flags);
    x->done += UINT_MAX/2;
    __wake_up_common(&x->wait, TASK_NORMAL, 0, 0, NULL);
    spin_unlock_irqrestore(&x->wait.lock, flags);
}
EXPORT_SYMBOL(complete_all);

static inline long __sched
do_wait_for_common(struct completion *x, long timeout, int state)
{
    if (!x->done) {
        DECLARE_WAITQUEUE(wait, current);

        __add_wait_queue_tail_exclusive(&x->wait, &wait);
        do {
            if (signal_pending_state(state, current)) {
                timeout = -ERESTARTSYS;
                break;
            }
            __set_current_state(state);
            spin_unlock_irq(&x->wait.lock);
            timeout = schedule_timeout(timeout);
            spin_lock_irq(&x->wait.lock);
        } while (!x->done && timeout);
        __remove_wait_queue(&x->wait, &wait);
        if (!x->done)
            return timeout;
    }
    x->done--;
    return timeout ?: 1;
}

static long __sched
wait_for_common(struct completion *x, long timeout, int state)
{
    might_sleep();

    spin_lock_irq(&x->wait.lock);
    timeout = do_wait_for_common(x, timeout, state);
    spin_unlock_irq(&x->wait.lock);
    return timeout;
}

void __sched wait_for_completion(struct completion *x)
{
    wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(wait_for_completion);

unsigned long __sched
wait_for_completion_timeout(struct completion *x, unsigned long timeout)
{
    return wait_for_common(x, timeout, TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(wait_for_completion_timeout);

int __sched wait_for_completion_interruptible(struct completion *x)
{
    long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE);
    if (t == -ERESTARTSYS)
        return t;
    return 0;
}
EXPORT_SYMBOL(wait_for_completion_interruptible);

long __sched
wait_for_completion_interruptible_timeout(struct completion *x,
                      unsigned long timeout)
{
    return wait_for_common(x, timeout, TASK_INTERRUPTIBLE);
}
EXPORT_SYMBOL(wait_for_completion_interruptible_timeout);

int __sched wait_for_completion_killable(struct completion *x)
{
    long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_KILLABLE);
    if (t == -ERESTARTSYS)
        return t;
    return 0;
}
EXPORT_SYMBOL(wait_for_completion_killable);

long __sched
wait_for_completion_killable_timeout(struct completion *x,
                     unsigned long timeout)
{
    return wait_for_common(x, timeout, TASK_KILLABLE);
}
EXPORT_SYMBOL(wait_for_completion_killable_timeout);

bool try_wait_for_completion(struct completion *x)
{
    unsigned long flags;
    int ret = 1;

    spin_lock_irqsave(&x->wait.lock, flags);
    if (!x->done)
        ret = 0;
    else
        x->done--;
    spin_unlock_irqrestore(&x->wait.lock, flags);
    return ret;
}
EXPORT_SYMBOL(try_wait_for_completion);

bool completion_done(struct completion *x)
{
    unsigned long flags;
    int ret = 1;

    spin_lock_irqsave(&x->wait.lock, flags);
    if (!x->done)
        ret = 0;
    spin_unlock_irqrestore(&x->wait.lock, flags);
    return ret;
}
EXPORT_SYMBOL(completion_done);

static long __sched
sleep_on_common(wait_queue_head_t *q, int state, long timeout)
{
    unsigned long flags;
    wait_queue_t wait;

    init_waitqueue_entry(&wait, current);

    __set_current_state(state);

    spin_lock_irqsave(&q->lock, flags);
    __add_wait_queue(q, &wait);
    spin_unlock(&q->lock);
    timeout = schedule_timeout(timeout);
    spin_lock_irq(&q->lock);
    __remove_wait_queue(q, &wait);
    spin_unlock_irqrestore(&q->lock, flags);

    return timeout;
}

void __sched interruptible_sleep_on(wait_queue_head_t *q)
{
    sleep_on_common(q, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
}
EXPORT_SYMBOL(interruptible_sleep_on);

long __sched
interruptible_sleep_on_timeout(wait_queue_head_t *q, long timeout)
{
    return sleep_on_common(q, TASK_INTERRUPTIBLE, timeout);
}
EXPORT_SYMBOL(interruptible_sleep_on_timeout);

void __sched sleep_on(wait_queue_head_t *q)
{
    sleep_on_common(q, TASK_UNINTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
}
EXPORT_SYMBOL(sleep_on);

long __sched sleep_on_timeout(wait_queue_head_t *q, long timeout)
{
    return sleep_on_common(q, TASK_UNINTERRUPTIBLE, timeout);
}
EXPORT_SYMBOL(sleep_on_timeout);

#ifdef CONFIG_RT_MUTEXES

/*
 * rt_mutex_setprio - set the current priority of a task
 * @p: task
 * @prio: prio value (kernel-internal form)
 *
 * This function changes the 'effective' priority of a task. It does
 * not touch ->normal_prio like __setscheduler().
 *
 * Used by the rt_mutex code to implement priority inheritance logic.
 */
void rt_mutex_setprio(struct task_struct *p, int prio)
{
    int oldprio, on_rq, running;
    struct rq *rq;
    const struct sched_class *prev_class;

    BUG_ON(prio < 0 || prio > MAX_PRIO);

    rq = __task_rq_lock(p);

    /*
     * Idle task boosting is a nono in general. There is one
     * exception, when PREEMPT_RT and NOHZ is active:
     *
     * The idle task calls get_next_timer_interrupt() and holds
     * the timer wheel base->lock on the CPU and another CPU wants
     * to access the timer (probably to cancel it). We can safely
     * ignore the boosting request, as the idle CPU runs this code
     * with interrupts disabled and will complete the lock
     * protected section without being interrupted. So there is no
     * real need to boost.
     */
    if (unlikely(p == rq->idle)) {
        WARN_ON(p != rq->curr);
        WARN_ON(p->pi_blocked_on);
        goto out_unlock;
    }

    trace_sched_pi_setprio(p, prio);
    oldprio = p->prio;
    prev_class = p->sched_class;
    on_rq = p->on_rq;
    running = task_current(rq, p);
    if (on_rq)
        dequeue_task(rq, p, 0);
    if (running)
        p->sched_class->put_prev_task(rq, p);

    if (rt_prio(prio))
        p->sched_class = &rt_sched_class;
    else
        p->sched_class = &fair_sched_class;

    p->prio = prio;

    if (running)
        p->sched_class->set_curr_task(rq);
    if (on_rq)
        enqueue_task(rq, p, oldprio < prio ? ENQUEUE_HEAD : 0);

    check_class_changed(rq, p, prev_class, oldprio);
out_unlock:
    __task_rq_unlock(rq);
}
#endif
void set_user_nice(struct task_struct *p, long nice)
{
    int old_prio, delta, on_rq;
    unsigned long flags;
    struct rq *rq;

    if (TASK_NICE(p) == nice || nice < -20 || nice > 19)
        return;
    /*
     * We have to be careful, if called from sys_setpriority(),
     * the task might be in the middle of scheduling on another CPU.
     */
    rq = task_rq_lock(p, &flags);
    /*
     * The RT priorities are set via sched_setscheduler(), but we still
     * allow the 'normal' nice value to be set - but as expected
     * it wont have any effect on scheduling until the task is
     * SCHED_FIFO/SCHED_RR:
     */
    if (task_has_rt_policy(p)) {
        p->static_prio = NICE_TO_PRIO(nice);
        goto out_unlock;
    }
    on_rq = p->on_rq;
    if (on_rq)
        dequeue_task(rq, p, 0);

    p->static_prio = NICE_TO_PRIO(nice);
    set_load_weight(p);
    old_prio = p->prio;
    p->prio = effective_prio(p);
    delta = p->prio - old_prio;

    if (on_rq) {
        enqueue_task(rq, p, 0);
        /*
         * If the task increased its priority or is running and
         * lowered its priority, then reschedule its CPU:
         */
        if (delta < 0 || (delta > 0 && task_running(rq, p)))
            resched_task(rq->curr);
    }
out_unlock:
    task_rq_unlock(rq, p, &flags);
}
EXPORT_SYMBOL(set_user_nice);

/*
 * can_nice - check if a task can reduce its nice value
 * @p: task
 * @nice: nice value
 */
int can_nice(const struct task_struct *p, const int nice)
{
    /* convert nice value [19,-20] to rlimit style value [1,40] */
    int nice_rlim = 20 - nice;

    return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) ||
        capable(CAP_SYS_NICE));
}

#ifdef __ARCH_WANT_SYS_NICE

/*
 * sys_nice - change the priority of the current process.
 * @increment: priority increment
 *
 * sys_setpriority is a more generic, but much slower function that
 * does similar things.
 */
SYSCALL_DEFINE1(nice, int, increment)
{
    long nice, retval;

    /*
     * Setpriority might change our priority at the same moment.
     * We don't have to worry. Conceptually one call occurs first
     * and we have a single winner.
     */
    if (increment < -40)
        increment = -40;
    if (increment > 40)
        increment = 40;

    nice = TASK_NICE(current) + increment;
    if (nice < -20)
        nice = -20;
    if (nice > 19)
        nice = 19;

    if (increment < 0 && !can_nice(current, nice))
        return -EPERM;

    retval = security_task_setnice(current, nice);
    if (retval)
        return retval;

    set_user_nice(current, nice);
    return 0;
}

#endif

int task_prio(const struct task_struct *p)
{
    return p->prio - MAX_RT_PRIO;
}

int task_nice(const struct task_struct *p)
{
    return TASK_NICE(p);
}
EXPORT_SYMBOL(task_nice);

int idle_cpu(int cpu)
{
    struct rq *rq = cpu_rq(cpu);

    if (rq->curr != rq->idle)
        return 0;

    if (rq->nr_running)
        return 0;

#ifdef CONFIG_SMP
    if (!llist_empty(&rq->wake_list))
        return 0;
#endif

    return 1;
}

struct task_struct *idle_task(int cpu)
{
    return cpu_rq(cpu)->idle;
}

static struct task_struct *find_process_by_pid(pid_t pid)
{
    return pid ? find_task_by_vpid(pid) : current;
}

/* Actually do priority change: must hold rq lock. */
static void
__setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio)
{
    p->policy = policy;
    p->rt_priority = prio;
    p->normal_prio = normal_prio(p);
    /* we are holding p->pi_lock already */
    p->prio = rt_mutex_getprio(p);
    if (rt_prio(p->prio))
        p->sched_class = &rt_sched_class;
    else
        p->sched_class = &fair_sched_class;
    set_load_weight(p);
}

/*
 * check the target process has a UID that matches the current process's
 */
static bool check_same_owner(struct task_struct *p)
{
    const struct cred *cred = current_cred(), *pcred;
    bool match;

    rcu_read_lock();
    pcred = __task_cred(p);
    match = (uid_eq(cred->euid, pcred->euid) ||
         uid_eq(cred->euid, pcred->uid));
    rcu_read_unlock();
    return match;
}

static int __sched_setscheduler(struct task_struct *p, int policy,
                const struct sched_param *param, bool user)
{
    int retval, oldprio, oldpolicy = -1, on_rq, running;
    unsigned long flags;
    const struct sched_class *prev_class;
    struct rq *rq;
    int reset_on_fork;

    /* may grab non-irq protected spin_locks */
    BUG_ON(in_interrupt());
recheck:
    /* double check policy once rq lock held */
    if (policy < 0) {
        reset_on_fork = p->sched_reset_on_fork;
        policy = oldpolicy = p->policy;
    } else {
        reset_on_fork = !!(policy & SCHED_RESET_ON_FORK);
        policy &= ~SCHED_RESET_ON_FORK;

        if (policy != SCHED_FIFO && policy != SCHED_RR &&
                policy != SCHED_NORMAL && policy != SCHED_BATCH &&
                policy != SCHED_IDLE)
            return -EINVAL;
    }

    /*
     * Valid priorities for SCHED_FIFO and SCHED_RR are
     * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
     * SCHED_BATCH and SCHED_IDLE is 0.
     */
    if (param->sched_priority < 0 ||
        (p->mm && param->sched_priority > MAX_USER_RT_PRIO-1) ||
        (!p->mm && param->sched_priority > MAX_RT_PRIO-1))
        return -EINVAL;
    if (rt_policy(policy) != (param->sched_priority != 0))
        return -EINVAL;

    /*
     * Allow unprivileged RT tasks to decrease priority:
     */
    if (user && !capable(CAP_SYS_NICE)) {
        if (rt_policy(policy)) {
            unsigned long rlim_rtprio =
                    task_rlimit(p, RLIMIT_RTPRIO);

            /* can't set/change the rt policy */
            if (policy != p->policy && !rlim_rtprio)
                return -EPERM;

            /* can't increase priority */
            if (param->sched_priority > p->rt_priority &&
                param->sched_priority > rlim_rtprio)
                return -EPERM;
        }

        /*
         * Treat SCHED_IDLE as nice 20. Only allow a switch to
         * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
         */
        if (p->policy == SCHED_IDLE && policy != SCHED_IDLE) {
            if (!can_nice(p, TASK_NICE(p)))
                return -EPERM;
        }

        /* can't change other user's priorities */
        if (!check_same_owner(p))
            return -EPERM;

        /* Normal users shall not reset the sched_reset_on_fork flag */
        if (p->sched_reset_on_fork && !reset_on_fork)
            return -EPERM;
    }

    if (user) {
        retval = security_task_setscheduler(p);
        if (retval)
            return retval;
    }

    /*
     * make sure no PI-waiters arrive (or leave) while we are
     * changing the priority of the task:
     *
     * To be able to change p->policy safely, the appropriate
     * runqueue lock must be held.
     */
    rq = task_rq_lock(p, &flags);

    /*
     * Changing the policy of the stop threads its a very bad idea
     */
    if (p == rq->stop) {
        task_rq_unlock(rq, p, &flags);
        return -EINVAL;
    }

    /*
     * If not changing anything there's no need to proceed further:
     */
    if (unlikely(policy == p->policy && (!rt_policy(policy) ||
            param->sched_priority == p->rt_priority))) {
        task_rq_unlock(rq, p, &flags);
        return 0;
    }

#ifdef CONFIG_RT_GROUP_SCHED
    if (user) {
        /*
         * Do not allow realtime tasks into groups that have no runtime
         * assigned.
         */
        if (rt_bandwidth_enabled() && rt_policy(policy) &&
                task_group(p)->rt_bandwidth.rt_runtime == 0 &&
                !task_group_is_autogroup(task_group(p))) {
            task_rq_unlock(rq, p, &flags);
            return -EPERM;
        }
    }
#endif

    /* recheck policy now with rq lock held */
    if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
        policy = oldpolicy = -1;
        task_rq_unlock(rq, p, &flags);
        goto recheck;
    }
    on_rq = p->on_rq;
    running = task_current(rq, p);
    if (on_rq)
        dequeue_task(rq, p, 0);
    if (running)
        p->sched_class->put_prev_task(rq, p);

    p->sched_reset_on_fork = reset_on_fork;

    oldprio = p->prio;
    prev_class = p->sched_class;
    __setscheduler(rq, p, policy, param->sched_priority);

    if (running)
        p->sched_class->set_curr_task(rq);
    if (on_rq)
        enqueue_task(rq, p, 0);

    check_class_changed(rq, p, prev_class, oldprio);
    task_rq_unlock(rq, p, &flags);

    rt_mutex_adjust_pi(p);

    return 0;
}

int sched_setscheduler(struct task_struct *p, int policy,
               const struct sched_param *param)
{
    return __sched_setscheduler(p, policy, param, true);
}
EXPORT_SYMBOL_GPL(sched_setscheduler);

int sched_setscheduler_nocheck(struct task_struct *p, int policy,
                   const struct sched_param *param)
{
    return __sched_setscheduler(p, policy, param, false);
}

static int
do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
{
    struct sched_param lparam;
    struct task_struct *p;
    int retval;

    if (!param || pid < 0)
        return -EINVAL;
    if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
        return -EFAULT;

    rcu_read_lock();
    retval = -ESRCH;
    p = find_process_by_pid(pid);
    if (p != NULL)
        retval = sched_setscheduler(p, policy, &lparam);
    rcu_read_unlock();

    return retval;
}

SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy,
        struct sched_param __user *, param)
{
    /* negative values for policy are not valid */
    if (policy < 0)
        return -EINVAL;

    return do_sched_setscheduler(pid, policy, param);
}

SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
{
    return do_sched_setscheduler(pid, -1, param);
}

SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
{
    struct task_struct *p;
    int retval;

    if (pid < 0)
        return -EINVAL;

    retval = -ESRCH;
    rcu_read_lock();
    p = find_process_by_pid(pid);
    if (p) {
        retval = security_task_getscheduler(p);
        if (!retval)
            retval = p->policy
                | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
    }
    rcu_read_unlock();
    return retval;
}

SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
{
    struct sched_param lp;
    struct task_struct *p;
    int retval;

    if (!param || pid < 0)
        return -EINVAL;

    rcu_read_lock();
    p = find_process_by_pid(pid);
    retval = -ESRCH;
    if (!p)
        goto out_unlock;

    retval = security_task_getscheduler(p);
    if (retval)
        goto out_unlock;

    lp.sched_priority = p->rt_priority;
    rcu_read_unlock();

    /*
     * This one might sleep, we cannot do it with a spinlock held ...
     */
    retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;

    return retval;

out_unlock:
    rcu_read_unlock();
    return retval;
}

long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
{
    cpumask_var_t cpus_allowed, new_mask;
    struct task_struct *p;
    int retval;

    get_online_cpus();
    rcu_read_lock();

    p = find_process_by_pid(pid);
    if (!p) {
        rcu_read_unlock();
        put_online_cpus();
        return -ESRCH;
    }

    /* Prevent p going away */
    get_task_struct(p);
    rcu_read_unlock();

    if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
        retval = -ENOMEM;
        goto out_put_task;
    }
    if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
        retval = -ENOMEM;
        goto out_free_cpus_allowed;
    }
    retval = -EPERM;
    if (!check_same_owner(p) && !ns_capable(task_user_ns(p), CAP_SYS_NICE))
        goto out_unlock;

    retval = security_task_setscheduler(p);
    if (retval)
        goto out_unlock;

    cpuset_cpus_allowed(p, cpus_allowed);
    cpumask_and(new_mask, in_mask, cpus_allowed);
again:
    retval = set_cpus_allowed_ptr(p, new_mask);

    if (!retval) {
        cpuset_cpus_allowed(p, cpus_allowed);
        if (!cpumask_subset(new_mask, cpus_allowed)) {
            /*
             * We must have raced with a concurrent cpuset
             * update. Just reset the cpus_allowed to the
             * cpuset's cpus_allowed
             */
            cpumask_copy(new_mask, cpus_allowed);
            goto again;
        }
    }
out_unlock:
    free_cpumask_var(new_mask);
out_free_cpus_allowed:
    free_cpumask_var(cpus_allowed);
out_put_task:
    put_task_struct(p);
    put_online_cpus();
    return retval;
}

static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
                 struct cpumask *new_mask)
{
    if (len < cpumask_size())
        cpumask_clear(new_mask);
    else if (len > cpumask_size())
        len = cpumask_size();

    return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
}

SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
        unsigned long __user *, user_mask_ptr)
{
    cpumask_var_t new_mask;
    int retval;

    if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
        return -ENOMEM;

    retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
    if (retval == 0)
        retval = sched_setaffinity(pid, new_mask);
    free_cpumask_var(new_mask);
    return retval;
}

long sched_getaffinity(pid_t pid, struct cpumask *mask)
{
    struct task_struct *p;
    unsigned long flags;
    int retval;

    get_online_cpus();
    rcu_read_lock();

    retval = -ESRCH;
    p = find_process_by_pid(pid);
    if (!p)
        goto out_unlock;

    retval = security_task_getscheduler(p);
    if (retval)
        goto out_unlock;

    raw_spin_lock_irqsave(&p->pi_lock, flags);
    cpumask_and(mask, &p->cpus_allowed, cpu_online_mask);
    raw_spin_unlock_irqrestore(&p->pi_lock, flags);

out_unlock:
    rcu_read_unlock();
    put_online_cpus();

    return retval;
}

SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
        unsigned long __user *, user_mask_ptr)
{
    int ret;
    cpumask_var_t mask;

    if ((len * BITS_PER_BYTE) < nr_cpu_ids)
        return -EINVAL;
    if (len & (sizeof(unsigned long)-1))
        return -EINVAL;

    if (!alloc_cpumask_var(&mask, GFP_KERNEL))
        return -ENOMEM;

    ret = sched_getaffinity(pid, mask);
    if (ret == 0) {
        size_t retlen = min_t(size_t, len, cpumask_size());

        if (copy_to_user(user_mask_ptr, mask, retlen))
            ret = -EFAULT;
        else
            ret = retlen;
    }
    free_cpumask_var(mask);

    return ret;
}

SYSCALL_DEFINE0(sched_yield)
{
    struct rq *rq = this_rq_lock();

    schedstat_inc(rq, yld_count);
    current->sched_class->yield_task(rq);

    /*
     * Since we are going to call schedule() anyway, there's
     * no need to preempt or enable interrupts:
     */
    __release(rq->lock);
    spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
    do_raw_spin_unlock(&rq->lock);
    sched_preempt_enable_no_resched();

    schedule();

    return 0;
}

static inline int should_resched(void)
{
    return need_resched() && !(preempt_count() & PREEMPT_ACTIVE);
}

static void __cond_resched(void)
{
    add_preempt_count(PREEMPT_ACTIVE);
    __schedule();
    sub_preempt_count(PREEMPT_ACTIVE);
}

int __sched _cond_resched(void)
{
    if (should_resched()) {
        __cond_resched();
        return 1;
    }
    return 0;
}
EXPORT_SYMBOL(_cond_resched);

/*
 * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
 * call schedule, and on return reacquire the lock.
 *
 * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
 * operations here to prevent schedule() from being called twice (once via
 * spin_unlock(), once by hand).
 */
int __cond_resched_lock(spinlock_t *lock)
{
    int resched = should_resched();
    int ret = 0;

    lockdep_assert_held(lock);

    if (spin_needbreak(lock) || resched) {
        spin_unlock(lock);
        if (resched)
            __cond_resched();
        else
            cpu_relax();
        ret = 1;
        spin_lock(lock);
    }
    return ret;
}
EXPORT_SYMBOL(__cond_resched_lock);

int __sched __cond_resched_softirq(void)
{
    BUG_ON(!in_softirq());

    if (should_resched()) {
        local_bh_enable();
        __cond_resched();
        local_bh_disable();
        return 1;
    }
    return 0;
}
EXPORT_SYMBOL(__cond_resched_softirq);

void __sched yield(void)
{
    set_current_state(TASK_RUNNING);
    sys_sched_yield();
}
EXPORT_SYMBOL(yield);

bool __sched yield_to(struct task_struct *p, bool preempt)
{
    struct task_struct *curr = current;
    struct rq *rq, *p_rq;
    unsigned long flags;
    bool yielded = 0;

    local_irq_save(flags);
    rq = this_rq();

again:
    p_rq = task_rq(p);
    double_rq_lock(rq, p_rq);
    while (task_rq(p) != p_rq) {
        double_rq_unlock(rq, p_rq);
        goto again;
    }

    if (!curr->sched_class->yield_to_task)
        goto out;

    if (curr->sched_class != p->sched_class)
        goto out;

    if (task_running(p_rq, p) || p->state)
        goto out;

    yielded = curr->sched_class->yield_to_task(rq, p, preempt);
    if (yielded) {
        schedstat_inc(rq, yld_count);
        /*
         * Make p's CPU reschedule; pick_next_entity takes care of
         * fairness.
         */
        if (preempt && rq != p_rq)
            resched_task(p_rq->curr);
    }

out:
    double_rq_unlock(rq, p_rq);
    local_irq_restore(flags);

    if (yielded)
        schedule();

    return yielded;
}
EXPORT_SYMBOL_GPL(yield_to);

/*
 * This task is about to go to sleep on IO. Increment rq->nr_iowait so
 * that process accounting knows that this is a task in IO wait state.
 */
void __sched io_schedule(void)
{
    struct rq *rq = raw_rq();

    delayacct_blkio_start();
    atomic_inc(&rq->nr_iowait);
    blk_flush_plug(current);
    current->in_iowait = 1;
    schedule();
    current->in_iowait = 0;
    atomic_dec(&rq->nr_iowait);
    delayacct_blkio_end();
}
EXPORT_SYMBOL(io_schedule);

long __sched io_schedule_timeout(long timeout)
{
    struct rq *rq = raw_rq();
    long ret;

    delayacct_blkio_start();
    atomic_inc(&rq->nr_iowait);
    blk_flush_plug(current);
    current->in_iowait = 1;
    ret = schedule_timeout(timeout);
    current->in_iowait = 0;
    atomic_dec(&rq->nr_iowait);
    delayacct_blkio_end();
    return ret;
}

SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
{
    int ret = -EINVAL;

    switch (policy) {
    case SCHED_FIFO:
    case SCHED_RR:
        ret = MAX_USER_RT_PRIO-1;
        break;
    case SCHED_NORMAL:
    case SCHED_BATCH:
    case SCHED_IDLE:
        ret = 0;
        break;
    }
    return ret;
}

SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
{
    int ret = -EINVAL;

    switch (policy) {
    case SCHED_FIFO:
    case SCHED_RR:
        ret = 1;
        break;
    case SCHED_NORMAL:
    case SCHED_BATCH:
    case SCHED_IDLE:
        ret = 0;
    }
    return ret;
}

SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
        struct timespec __user *, interval)
{
    struct task_struct *p;
    unsigned int time_slice;
    unsigned long flags;
    struct rq *rq;
    int retval;
    struct timespec t;

    if (pid < 0)
        return -EINVAL;

    retval = -ESRCH;
    rcu_read_lock();
    p = find_process_by_pid(pid);
    if (!p)
        goto out_unlock;

    retval = security_task_getscheduler(p);
    if (retval)
        goto out_unlock;

    rq = task_rq_lock(p, &flags);
    time_slice = p->sched_class->get_rr_interval(rq, p);
    task_rq_unlock(rq, p, &flags);

    rcu_read_unlock();
    jiffies_to_timespec(time_slice, &t);
    retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
    return retval;

out_unlock:
    rcu_read_unlock();
    return retval;
}

static const char stat_nam[] = TASK_STATE_TO_CHAR_STR;

void sched_show_task(struct task_struct *p)
{
    unsigned long free = 0;
    unsigned state;

    state = p->state ? __ffs(p->state) + 1 : 0;
    printk(KERN_INFO "%-15.15s %c", p->comm,
        state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?');
#if BITS_PER_LONG == 32
    if (state == TASK_RUNNING)
        printk(KERN_CONT " running  ");
    else
        printk(KERN_CONT " %08lx ", thread_saved_pc(p));
#else
    if (state == TASK_RUNNING)
        printk(KERN_CONT "  running task    ");
    else
        printk(KERN_CONT " %016lx ", thread_saved_pc(p));
#endif
#ifdef CONFIG_DEBUG_STACK_USAGE
    free = stack_not_used(p);
#endif
    printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free,
        task_pid_nr(p), task_pid_nr(rcu_dereference(p->real_parent)),
        (unsigned long)task_thread_info(p)->flags);

    show_stack(p, NULL);
}

void show_state_filter(unsigned long state_filter)
{
    struct task_struct *g, *p;

#if BITS_PER_LONG == 32
    printk(KERN_INFO
        "  task                PC stack   pid father\n");
#else
    printk(KERN_INFO
        "  task                        PC stack   pid father\n");
#endif
    rcu_read_lock();
    do_each_thread(g, p) {
        /*
         * reset the NMI-timeout, listing all files on a slow
         * console might take a lot of time:
         */
        touch_nmi_watchdog();
        if (!state_filter || (p->state & state_filter))
            sched_show_task(p);
    } while_each_thread(g, p);

    touch_all_softlockup_watchdogs();

#ifdef CONFIG_SCHED_DEBUG
    sysrq_sched_debug_show();
#endif
    rcu_read_unlock();
    /*
     * Only show locks if all tasks are dumped:
     */
    if (!state_filter)
        debug_show_all_locks();
}

void __cpuinit init_idle_bootup_task(struct task_struct *idle)
{
    idle->sched_class = &idle_sched_class;
}

void __cpuinit init_idle(struct task_struct *idle, int cpu)
{
    struct rq *rq = cpu_rq(cpu);
    unsigned long flags;

    raw_spin_lock_irqsave(&rq->lock, flags);

    __sched_fork(idle);
    idle->state = TASK_RUNNING;
    idle->se.exec_start = sched_clock();

    do_set_cpus_allowed(idle, cpumask_of(cpu));
    /*
     * We're having a chicken and egg problem, even though we are
     * holding rq->lock, the cpu isn't yet set to this cpu so the
     * lockdep check in task_group() will fail.
     *
     * Similar case to sched_fork(). / Alternatively we could
     * use task_rq_lock() here and obtain the other rq->lock.
     *
     * Silence PROVE_RCU
     */
    rcu_read_lock();
    __set_task_cpu(idle, cpu);
    rcu_read_unlock();

    rq->curr = rq->idle = idle;
#if defined(CONFIG_SMP)
    idle->on_cpu = 1;
#endif
    raw_spin_unlock_irqrestore(&rq->lock, flags);

    /* Set the preempt count _outside_ the spinlocks! */
    task_thread_info(idle)->preempt_count = 0;

    /*
     * The idle tasks have their own, simple scheduling class:
     */
    idle->sched_class = &idle_sched_class;
    ftrace_graph_init_idle_task(idle, cpu);
#if defined(CONFIG_SMP)
    sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
#endif
}

#ifdef CONFIG_SMP
void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
{
    if (p->sched_class && p->sched_class->set_cpus_allowed)
        p->sched_class->set_cpus_allowed(p, new_mask);

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

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

/*
 * Change a given task's CPU affinity. Migrate the thread to a
 * proper CPU and schedule it away if the CPU it's executing on
 * is removed from the allowed bitmask.
 *
 * NOTE: the caller must have a valid reference to the task, the
 * task must not exit() & deallocate itself prematurely. The
 * call is not atomic; no spinlocks may be held.
 */
int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
{
    unsigned long flags;
    struct rq *rq;
    unsigned int dest_cpu;
    int ret = 0;

    rq = task_rq_lock(p, &flags);

    if (cpumask_equal(&p->cpus_allowed, new_mask))
        goto out;

    if (!cpumask_intersects(new_mask, cpu_active_mask)) {
        ret = -EINVAL;
        goto out;
    }

    if (unlikely((p->flags & PF_THREAD_BOUND) && p != current)) {
        ret = -EINVAL;
        goto out;
    }

    do_set_cpus_allowed(p, new_mask);

    /* Can the task run on the task's current CPU? If so, we're done */
    if (cpumask_test_cpu(task_cpu(p), new_mask))
        goto out;

    dest_cpu = cpumask_any_and(cpu_active_mask, new_mask);
    if (p->on_rq) {
        struct migration_arg arg = { p, dest_cpu };
        /* Need help from migration thread: drop lock and wait. */
        task_rq_unlock(rq, p, &flags);
        stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
        tlb_migrate_finish(p->mm);
        return 0;
    }
out:
    task_rq_unlock(rq, p, &flags);

    return ret;
}
EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);

/*
 * Move (not current) task off this cpu, onto dest cpu. We're doing
 * this because either it can't run here any more (set_cpus_allowed()
 * away from this CPU, or CPU going down), or because we're
 * attempting to rebalance this task on exec (sched_exec).
 *
 * So we race with normal scheduler movements, but that's OK, as long
 * as the task is no longer on this CPU.
 *
 * Returns non-zero if task was successfully migrated.
 */
static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
{
    struct rq *rq_dest, *rq_src;
    int ret = 0;

    if (unlikely(!cpu_active(dest_cpu)))
        return ret;

    rq_src = cpu_rq(src_cpu);
    rq_dest = cpu_rq(dest_cpu);

    raw_spin_lock(&p->pi_lock);
    double_rq_lock(rq_src, rq_dest);
    /* Already moved. */
    if (task_cpu(p) != src_cpu)
        goto done;
    /* Affinity changed (again). */
    if (!cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
        goto fail;

    /*
     * If we're not on a rq, the next wake-up will ensure we're
     * placed properly.
     */
    if (p->on_rq) {
        dequeue_task(rq_src, p, 0);
        set_task_cpu(p, dest_cpu);
        enqueue_task(rq_dest, p, 0);
        check_preempt_curr(rq_dest, p, 0);
    }
done:
    ret = 1;
fail:
    double_rq_unlock(rq_src, rq_dest);
    raw_spin_unlock(&p->pi_lock);
    return ret;
}

/*
 * migration_cpu_stop - this will be executed by a highprio stopper thread
 * and performs thread migration by bumping thread off CPU then
 * 'pushing' onto another runqueue.
 */
static int migration_cpu_stop(void *data)
{
    struct migration_arg *arg = data;

    /*
     * The original target cpu might have gone down and we might
     * be on another cpu but it doesn't matter.
     */
    local_irq_disable();
    __migrate_task(arg->task, raw_smp_processor_id(), arg->dest_cpu);
    local_irq_enable();
    return 0;
}

#ifdef CONFIG_HOTPLUG_CPU

/*
 * Ensures that the idle task is using init_mm right before its cpu goes
 * offline.
 */
void idle_task_exit(void)
{
    struct mm_struct *mm = current->active_mm;

    BUG_ON(cpu_online(smp_processor_id()));

    if (mm != &init_mm)
        switch_mm(mm, &init_mm, current);
    mmdrop(mm);
}

/*
 * Since this CPU is going 'away' for a while, fold any nr_active delta
 * we might have. Assumes we're called after migrate_tasks() so that the
 * nr_active count is stable.
 *
 * Also see the comment "Global load-average calculations".
 */
static void calc_load_migrate(struct rq *rq)
{
    long delta = calc_load_fold_active(rq);
    if (delta)
        atomic_long_add(delta, &calc_load_tasks);
}

/*
 * Migrate all tasks from the rq, sleeping tasks will be migrated by
 * try_to_wake_up()->select_task_rq().
 *
 * Called with rq->lock held even though we'er in stop_machine() and
 * there's no concurrency possible, we hold the required locks anyway
 * because of lock validation efforts.
 */
static void migrate_tasks(unsigned int dead_cpu)
{
    struct rq *rq = cpu_rq(dead_cpu);
    struct task_struct *next, *stop = rq->stop;
    int dest_cpu;

    /*
     * Fudge the rq selection such that the below task selection loop
     * doesn't get stuck on the currently eligible stop task.
     *
     * We're currently inside stop_machine() and the rq is either stuck
     * in the stop_machine_cpu_stop() loop, or we're executing this code,
     * either way we should never end up calling schedule() until we're
     * done here.
     */
    rq->stop = NULL;

    for ( ; ; ) {
        /*
         * There's this thread running, bail when that's the only
         * remaining thread.
         */
        if (rq->nr_running == 1)
            break;

        next = pick_next_task(rq);
        BUG_ON(!next);
        next->sched_class->put_prev_task(rq, next);

        /* Find suitable destination for @next, with force if needed. */
        dest_cpu = select_fallback_rq(dead_cpu, next);
        raw_spin_unlock(&rq->lock);

        __migrate_task(next, dead_cpu, dest_cpu);

        raw_spin_lock(&rq->lock);
    }

    rq->stop = stop;
}

#endif /* CONFIG_HOTPLUG_CPU */

#if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_SYSCTL)

static struct ctl_table sd_ctl_dir[] = {
    {
        .procname   = "sched_domain",
        .mode       = 0555,
    },
    {}
};

static struct ctl_table sd_ctl_root[] = {
    {
        .procname   = "kernel",
        .mode       = 0555,
        .child      = sd_ctl_dir,
    },
    {}
};

static struct ctl_table *sd_alloc_ctl_entry(int n)
{
    struct ctl_table *entry =
        kcalloc(n, sizeof(struct ctl_table), GFP_KERNEL);

    return entry;
}

static void sd_free_ctl_entry(struct ctl_table **tablep)
{
    struct ctl_table *entry;

    /*
     * In the intermediate directories, both the child directory and
     * procname are dynamically allocated and could fail but the mode
     * will always be set. In the lowest directory the names are
     * static strings and all have proc handlers.
     */
    for (entry = *tablep; entry->mode; entry++) {
        if (entry->child)
            sd_free_ctl_entry(&entry->child);
        if (entry->proc_handler == NULL)
            kfree(entry->procname);
    }

    kfree(*tablep);
    *tablep = NULL;
}

static int min_load_idx = 0;
static int max_load_idx = CPU_LOAD_IDX_MAX;

static void
set_table_entry(struct ctl_table *entry,
        const char *procname, void *data, int maxlen,
        umode_t mode, proc_handler *proc_handler,
        bool load_idx)
{
    entry->procname = procname;
    entry->data = data;
    entry->maxlen = maxlen;
    entry->mode = mode;
    entry->proc_handler = proc_handler;

    if (load_idx) {
        entry->extra1 = &min_load_idx;
        entry->extra2 = &max_load_idx;
    }
}

static struct ctl_table *
sd_alloc_ctl_domain_table(struct sched_domain *sd)
{
    struct ctl_table *table = sd_alloc_ctl_entry(13);

    if (table == NULL)
        return NULL;

    set_table_entry(&table[0], "min_interval", &sd->min_interval,
        sizeof(long), 0644, proc_doulongvec_minmax, false);
    set_table_entry(&table[1], "max_interval", &sd->max_interval,
        sizeof(long), 0644, proc_doulongvec_minmax, false);
    set_table_entry(&table[2], "busy_idx", &sd->busy_idx,
        sizeof(int), 0644, proc_dointvec_minmax, true);
    set_table_entry(&table[3], "idle_idx", &sd->idle_idx,
        sizeof(int), 0644, proc_dointvec_minmax, true);
    set_table_entry(&table[4], "newidle_idx", &sd->newidle_idx,
        sizeof(int), 0644, proc_dointvec_minmax, true);
    set_table_entry(&table[5], "wake_idx", &sd->wake_idx,
        sizeof(int), 0644, proc_dointvec_minmax, true);
    set_table_entry(&table[6], "forkexec_idx", &sd->forkexec_idx,
        sizeof(int), 0644, proc_dointvec_minmax, true);
    set_table_entry(&table[7], "busy_factor", &sd->busy_factor,
        sizeof(int), 0644, proc_dointvec_minmax, false);
    set_table_entry(&table[8], "imbalance_pct", &sd->imbalance_pct,
        sizeof(int), 0644, proc_dointvec_minmax, false);
    set_table_entry(&table[9], "cache_nice_tries",
        &sd->cache_nice_tries,
        sizeof(int), 0644, proc_dointvec_minmax, false);
    set_table_entry(&table[10], "flags", &sd->flags,
        sizeof(int), 0644, proc_dointvec_minmax, false);
    set_table_entry(&table[11], "name", sd->name,
        CORENAME_MAX_SIZE, 0444, proc_dostring, false);
    /* &table[12] is terminator */

    return table;
}

static ctl_table *sd_alloc_ctl_cpu_table(int cpu)
{
    struct ctl_table *entry, *table;
    struct sched_domain *sd;
    int domain_num = 0, i;
    char buf[32];

    for_each_domain(cpu, sd)
        domain_num++;
    entry = table = sd_alloc_ctl_entry(domain_num + 1);
    if (table == NULL)
        return NULL;

    i = 0;
    for_each_domain(cpu, sd) {
        snprintf(buf, 32, "domain%d", i);
        entry->procname = kstrdup(buf, GFP_KERNEL);
        entry->mode = 0555;
        entry->child = sd_alloc_ctl_domain_table(sd);
        entry++;
        i++;
    }
    return table;
}

static struct ctl_table_header *sd_sysctl_header;
static void register_sched_domain_sysctl(void)
{
    int i, cpu_num = num_possible_cpus();
    struct ctl_table *entry = sd_alloc_ctl_entry(cpu_num + 1);
    char buf[32];

    WARN_ON(sd_ctl_dir[0].child);
    sd_ctl_dir[0].child = entry;

    if (entry == NULL)
        return;

    for_each_possible_cpu(i) {
        snprintf(buf, 32, "cpu%d", i);
        entry->procname = kstrdup(buf, GFP_KERNEL);
        entry->mode = 0555;
        entry->child = sd_alloc_ctl_cpu_table(i);
        entry++;
    }

    WARN_ON(sd_sysctl_header);
    sd_sysctl_header = register_sysctl_table(sd_ctl_root);
}

/* may be called multiple times per register */
static void unregister_sched_domain_sysctl(void)
{
    if (sd_sysctl_header)
        unregister_sysctl_table(sd_sysctl_header);
    sd_sysctl_header = NULL;
    if (sd_ctl_dir[0].child)
        sd_free_ctl_entry(&sd_ctl_dir[0].child);
}
#else
static void register_sched_domain_sysctl(void)
{
}
static void unregister_sched_domain_sysctl(void)
{
}
#endif

static void set_rq_online(struct rq *rq)
{
    if (!rq->online) {
        const struct sched_class *class;

        cpumask_set_cpu(rq->cpu, rq->rd->online);
        rq->online = 1;

        for_each_class(class) {
            if (class->rq_online)
                class->rq_online(rq);
        }
    }
}

static void set_rq_offline(struct rq *rq)
{
    if (rq->online) {
        const struct sched_class *class;

        for_each_class(class) {
            if (class->rq_offline)
                class->rq_offline(rq);
        }

        cpumask_clear_cpu(rq->cpu, rq->rd->online);
        rq->online = 0;
    }
}

/*
 * migration_call - callback that gets triggered when a CPU is added.
 * Here we can start up the necessary migration thread for the new CPU.
 */
static int __cpuinit
migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
{
    int cpu = (long)hcpu;
    unsigned long flags;
    struct rq *rq = cpu_rq(cpu);

    switch (action & ~CPU_TASKS_FROZEN) {

    case CPU_UP_PREPARE:
        rq->calc_load_update = calc_load_update;
        break;

    case CPU_ONLINE:
        /* Update our root-domain */
        raw_spin_lock_irqsave(&rq->lock, flags);
        if (rq->rd) {
            BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));

            set_rq_online(rq);
        }
        raw_spin_unlock_irqrestore(&rq->lock, flags);
        break;

#ifdef CONFIG_HOTPLUG_CPU
    case CPU_DYING:
        sched_ttwu_pending();
        /* Update our root-domain */
        raw_spin_lock_irqsave(&rq->lock, flags);
        if (rq->rd) {
            BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
            set_rq_offline(rq);
        }
        migrate_tasks(cpu);
        BUG_ON(rq->nr_running != 1); /* the migration thread */
        raw_spin_unlock_irqrestore(&rq->lock, flags);
        break;

    case CPU_DEAD:
        calc_load_migrate(rq);
        break;
#endif
    }

    update_max_interval();

    return NOTIFY_OK;
}

/*
 * Register at high priority so that task migration (migrate_all_tasks)
 * happens before everything else.  This has to be lower priority than
 * the notifier in the perf_event subsystem, though.
 */
static struct notifier_block __cpuinitdata migration_notifier = {
    .notifier_call = migration_call,
    .priority = CPU_PRI_MIGRATION,
};

static int __cpuinit sched_cpu_active(struct notifier_block *nfb,
                      unsigned long action, void *hcpu)
{
    switch (action & ~CPU_TASKS_FROZEN) {
    case CPU_STARTING:
    case CPU_DOWN_FAILED:
        set_cpu_active((long)hcpu, true);
        return NOTIFY_OK;
    default:
        return NOTIFY_DONE;
    }
}

static int __cpuinit sched_cpu_inactive(struct notifier_block *nfb,
                    unsigned long action, void *hcpu)
{
    switch (action & ~CPU_TASKS_FROZEN) {
    case CPU_DOWN_PREPARE:
        set_cpu_active((long)hcpu, false);
        return NOTIFY_OK;
    default:
        return NOTIFY_DONE;
    }
}

static int __init migration_init(void)
{
    void *cpu = (void *)(long)smp_processor_id();
    int err;

    /* Initialize migration for the boot CPU */
    err = migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
    BUG_ON(err == NOTIFY_BAD);
    migration_call(&migration_notifier, CPU_ONLINE, cpu);
    register_cpu_notifier(&migration_notifier);

    /* Register cpu active notifiers */
    cpu_notifier(sched_cpu_active, CPU_PRI_SCHED_ACTIVE);
    cpu_notifier(sched_cpu_inactive, CPU_PRI_SCHED_INACTIVE);

    return 0;
}
early_initcall(migration_init);
#endif

#ifdef CONFIG_SMP

static cpumask_var_t sched_domains_tmpmask; /* sched_domains_mutex */

#ifdef CONFIG_SCHED_DEBUG

static __read_mostly int sched_debug_enabled;

static int __init sched_debug_setup(char *str)
{
    sched_debug_enabled = 1;

    return 0;
}
early_param("sched_debug", sched_debug_setup);

static inline bool sched_debug(void)
{
    return sched_debug_enabled;
}

static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
                  struct cpumask *groupmask)
{
    struct sched_group *group = sd->groups;
    char str[256];

    cpulist_scnprintf(str, sizeof(str), sched_domain_span(sd));
    cpumask_clear(groupmask);

    printk(KERN_DEBUG "%*s domain %d: ", level, "", level);

    if (!(sd->flags & SD_LOAD_BALANCE)) {
        printk("does not load-balance\n");
        if (sd->parent)
            printk(KERN_ERR "ERROR: !SD_LOAD_BALANCE domain"
                    " has parent");
        return -1;
    }

    printk(KERN_CONT "span %s level %s\n", str, sd->name);

    if (!cpumask_test_cpu(cpu, sched_domain_span(sd))) {
        printk(KERN_ERR "ERROR: domain->span does not contain "
                "CPU%d\n", cpu);
    }
    if (!cpumask_test_cpu(cpu, sched_group_cpus(group))) {
        printk(KERN_ERR "ERROR: domain->groups does not contain"
                " CPU%d\n", cpu);
    }

    printk(KERN_DEBUG "%*s groups:", level + 1, "");
    do {
        if (!group) {
            printk("\n");
            printk(KERN_ERR "ERROR: group is NULL\n");
            break;
        }

        /*
         * Even though we initialize ->power to something semi-sane,
         * we leave power_orig unset. This allows us to detect if
         * domain iteration is still funny without causing /0 traps.
         */
        if (!group->sgp->power_orig) {
            printk(KERN_CONT "\n");
            printk(KERN_ERR "ERROR: domain->cpu_power not "
                    "set\n");
            break;
        }

        if (!cpumask_weight(sched_group_cpus(group))) {
            printk(KERN_CONT "\n");
            printk(KERN_ERR "ERROR: empty group\n");
            break;
        }

        if (!(sd->flags & SD_OVERLAP) &&
            cpumask_intersects(groupmask, sched_group_cpus(group))) {
            printk(KERN_CONT "\n");
            printk(KERN_ERR "ERROR: repeated CPUs\n");
            break;
        }

        cpumask_or(groupmask, groupmask, sched_group_cpus(group));

        cpulist_scnprintf(str, sizeof(str), sched_group_cpus(group));

        printk(KERN_CONT " %s", str);
        if (group->sgp->power != SCHED_POWER_SCALE) {
            printk(KERN_CONT " (cpu_power = %d)",
                group->sgp->power);
        }

        group = group->next;
    } while (group != sd->groups);
    printk(KERN_CONT "\n");

    if (!cpumask_equal(sched_domain_span(sd), groupmask))
        printk(KERN_ERR "ERROR: groups don't span domain->span\n");

    if (sd->parent &&
        !cpumask_subset(groupmask, sched_domain_span(sd->parent)))
        printk(KERN_ERR "ERROR: parent span is not a superset "
            "of domain->span\n");
    return 0;
}

static void sched_domain_debug(struct sched_domain *sd, int cpu)
{
    int level = 0;

    if (!sched_debug_enabled)
        return;

    if (!sd) {
        printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu);
        return;
    }

    printk(KERN_DEBUG "CPU%d attaching sched-domain:\n", cpu);

    for (;;) {
        if (sched_domain_debug_one(sd, cpu, level, sched_domains_tmpmask))
            break;
        level++;
        sd = sd->parent;
        if (!sd)
            break;
    }
}
#else /* !CONFIG_SCHED_DEBUG */
# define sched_domain_debug(sd, cpu) do { } while (0)
static inline bool sched_debug(void)
{
    return false;
}
#endif /* CONFIG_SCHED_DEBUG */

static int sd_degenerate(struct sched_domain *sd)
{
    if (cpumask_weight(sched_domain_span(sd)) == 1)
        return 1;

    /* Following flags need at least 2 groups */
    if (sd->flags & (SD_LOAD_BALANCE |
             SD_BALANCE_NEWIDLE |
             SD_BALANCE_FORK |
             SD_BALANCE_EXEC |
             SD_SHARE_CPUPOWER |
             SD_SHARE_PKG_RESOURCES)) {
        if (sd->groups != sd->groups->next)
            return 0;
    }

    /* Following flags don't use groups */
    if (sd->flags & (SD_WAKE_AFFINE))
        return 0;

    return 1;
}

static int
sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
{
    unsigned long cflags = sd->flags, pflags = parent->flags;

    if (sd_degenerate(parent))
        return 1;

    if (!cpumask_equal(sched_domain_span(sd), sched_domain_span(parent)))
        return 0;

    /* Flags needing groups don't count if only 1 group in parent */
    if (parent->groups == parent->groups->next) {
        pflags &= ~(SD_LOAD_BALANCE |
                SD_BALANCE_NEWIDLE |
                SD_BALANCE_FORK |
                SD_BALANCE_EXEC |
                SD_SHARE_CPUPOWER |
                SD_SHARE_PKG_RESOURCES);
        if (nr_node_ids == 1)
            pflags &= ~SD_SERIALIZE;
    }
    if (~cflags & pflags)
        return 0;

    return 1;
}

static void free_rootdomain(struct rcu_head *rcu)
{
    struct root_domain *rd = container_of(rcu, struct root_domain, rcu);

    cpupri_cleanup(&rd->cpupri);
    free_cpumask_var(rd->rto_mask);
    free_cpumask_var(rd->online);
    free_cpumask_var(rd->span);
    kfree(rd);
}

static void rq_attach_root(struct rq *rq, struct root_domain *rd)
{
    struct root_domain *old_rd = NULL;
    unsigned long flags;

    raw_spin_lock_irqsave(&rq->lock, flags);

    if (rq->rd) {
        old_rd = rq->rd;

        if (cpumask_test_cpu(rq->cpu, old_rd->online))
            set_rq_offline(rq);

        cpumask_clear_cpu(rq->cpu, old_rd->span);

        /*
         * If we dont want to free the old_rt yet then
         * set old_rd to NULL to skip the freeing later
         * in this function:
         */
        if (!atomic_dec_and_test(&old_rd->refcount))
            old_rd = NULL;
    }

    atomic_inc(&rd->refcount);
    rq->rd = rd;

    cpumask_set_cpu(rq->cpu, rd->span);
    if (cpumask_test_cpu(rq->cpu, cpu_active_mask))
        set_rq_online(rq);

    raw_spin_unlock_irqrestore(&rq->lock, flags);

    if (old_rd)
        call_rcu_sched(&old_rd->rcu, free_rootdomain);
}

static int init_rootdomain(struct root_domain *rd)
{
    memset(rd, 0, sizeof(*rd));

    if (!alloc_cpumask_var(&rd->span, GFP_KERNEL))
        goto out;
    if (!alloc_cpumask_var(&rd->online, GFP_KERNEL))
        goto free_span;
    if (!alloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
        goto free_online;

    if (cpupri_init(&rd->cpupri) != 0)
        goto free_rto_mask;
    return 0;

free_rto_mask:
    free_cpumask_var(rd->rto_mask);
free_online:
    free_cpumask_var(rd->online);
free_span:
    free_cpumask_var(rd->span);
out:
    return -ENOMEM;
}

/*
 * By default the system creates a single root-domain with all cpus as
 * members (mimicking the global state we have today).
 */
struct root_domain def_root_domain;

static void init_defrootdomain(void)
{
    init_rootdomain(&def_root_domain);

    atomic_set(&def_root_domain.refcount, 1);
}

static struct root_domain *alloc_rootdomain(void)
{
    struct root_domain *rd;

    rd = kmalloc(sizeof(*rd), GFP_KERNEL);
    if (!rd)
        return NULL;

    if (init_rootdomain(rd) != 0) {
        kfree(rd);
        return NULL;
    }

    return rd;
}

static void free_sched_groups(struct sched_group *sg, int free_sgp)
{
    struct sched_group *tmp, *first;

    if (!sg)
        return;

    first = sg;
    do {
        tmp = sg->next;

        if (free_sgp && atomic_dec_and_test(&sg->sgp->ref))
            kfree(sg->sgp);

        kfree(sg);
        sg = tmp;
    } while (sg != first);
}

static void free_sched_domain(struct rcu_head *rcu)
{
    struct sched_domain *sd = container_of(rcu, struct sched_domain, rcu);

    /*
     * If its an overlapping domain it has private groups, iterate and
     * nuke them all.
     */
    if (sd->flags & SD_OVERLAP) {
        free_sched_groups(sd->groups, 1);
    } else if (atomic_dec_and_test(&sd->groups->ref)) {
        kfree(sd->groups->sgp);
        kfree(sd->groups);
    }
    kfree(sd);
}

static void destroy_sched_domain(struct sched_domain *sd, int cpu)
{
    call_rcu(&sd->rcu, free_sched_domain);
}

static void destroy_sched_domains(struct sched_domain *sd, int cpu)
{
    for (; sd; sd = sd->parent)
        destroy_sched_domain(sd, cpu);
}

/*
 * Keep a special pointer to the highest sched_domain that has
 * SD_SHARE_PKG_RESOURCE set (Last Level Cache Domain) for this
 * allows us to avoid some pointer chasing select_idle_sibling().
 *
 * Also keep a unique ID per domain (we use the first cpu number in
 * the cpumask of the domain), this allows us to quickly tell if
 * two cpus are in the same cache domain, see cpus_share_cache().
 */
DEFINE_PER_CPU(struct sched_domain *, sd_llc);
DEFINE_PER_CPU(int, sd_llc_id);

static void update_top_cache_domain(int cpu)
{
    struct sched_domain *sd;
    int id = cpu;

    sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES);
    if (sd)
        id = cpumask_first(sched_domain_span(sd));

    rcu_assign_pointer(per_cpu(sd_llc, cpu), sd);
    per_cpu(sd_llc_id, cpu) = id;
}

/*
 * Attach the domain 'sd' to 'cpu' as its base domain. Callers must
 * hold the hotplug lock.
 */
static void
cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
{
    struct rq *rq = cpu_rq(cpu);
    struct sched_domain *tmp;

    /* Remove the sched domains which do not contribute to scheduling. */
    for (tmp = sd; tmp; ) {
        struct sched_domain *parent = tmp->parent;
        if (!parent)
            break;

        if (sd_parent_degenerate(tmp, parent)) {
            tmp->parent = parent->parent;
            if (parent->parent)
                parent->parent->child = tmp;
            destroy_sched_domain(parent, cpu);
        } else
            tmp = tmp->parent;
    }

    if (sd && sd_degenerate(sd)) {
        tmp = sd;
        sd = sd->parent;
        destroy_sched_domain(tmp, cpu);
        if (sd)
            sd->child = NULL;
    }

    sched_domain_debug(sd, cpu);

    rq_attach_root(rq, rd);
    tmp = rq->sd;
    rcu_assign_pointer(rq->sd, sd);
    destroy_sched_domains(tmp, cpu);

    update_top_cache_domain(cpu);
}

/* cpus with isolated domains */
static cpumask_var_t cpu_isolated_map;

/* Setup the mask of cpus configured for isolated domains */
static int __init isolated_cpu_setup(char *str)
{
    alloc_bootmem_cpumask_var(&cpu_isolated_map);
    cpulist_parse(str, cpu_isolated_map);
    return 1;
}

__setup("isolcpus=", isolated_cpu_setup);

static const struct cpumask *cpu_cpu_mask(int cpu)
{
    return cpumask_of_node(cpu_to_node(cpu));
}

struct sd_data {
    struct sched_domain **__percpu sd;
    struct sched_group **__percpu sg;
    struct sched_group_power **__percpu sgp;
};

struct s_data {
    struct sched_domain ** __percpu sd;
    struct root_domain  *rd;
};

enum s_alloc {
    sa_rootdomain,
    sa_sd,
    sa_sd_storage,
    sa_none,
};

struct sched_domain_topology_level;

typedef struct sched_domain *(*sched_domain_init_f)(struct sched_domain_topology_level *tl, int cpu);
typedef const struct cpumask *(*sched_domain_mask_f)(int cpu);

#define SDTL_OVERLAP    0x01

struct sched_domain_topology_level {
    sched_domain_init_f init;
    sched_domain_mask_f mask;
    int         flags;
    int         numa_level;
    struct sd_data      data;
};

/*
 * Build an iteration mask that can exclude certain CPUs from the upwards
 * domain traversal.
 *
 * Asymmetric node setups can result in situations where the domain tree is of
 * unequal depth, make sure to skip domains that already cover the entire
 * range.
 *
 * In that case build_sched_domains() will have terminated the iteration early
 * and our sibling sd spans will be empty. Domains should always include the
 * cpu they're built on, so check that.
 *
 */
static void build_group_mask(struct sched_domain *sd, struct sched_group *sg)
{
    const struct cpumask *span = sched_domain_span(sd);
    struct sd_data *sdd = sd->private;
    struct sched_domain *sibling;
    int i;

    for_each_cpu(i, span) {
        sibling = *per_cpu_ptr(sdd->sd, i);
        if (!cpumask_test_cpu(i, sched_domain_span(sibling)))
            continue;

        cpumask_set_cpu(i, sched_group_mask(sg));
    }
}

/*
 * Return the canonical balance cpu for this group, this is the first cpu
 * of this group that's also in the iteration mask.
 */
int group_balance_cpu(struct sched_group *sg)
{
    return cpumask_first_and(sched_group_cpus(sg), sched_group_mask(sg));
}

static int
build_overlap_sched_groups(struct sched_domain *sd, int cpu)
{
    struct sched_group *first = NULL, *last = NULL, *groups = NULL, *sg;
    const struct cpumask *span = sched_domain_span(sd);
    struct cpumask *covered = sched_domains_tmpmask;
    struct sd_data *sdd = sd->private;
    struct sched_domain *child;
    int i;

    cpumask_clear(covered);

    for_each_cpu(i, span) {
        struct cpumask *sg_span;

        if (cpumask_test_cpu(i, covered))
            continue;

        child = *per_cpu_ptr(sdd->sd, i);

        /* See the comment near build_group_mask(). */
        if (!cpumask_test_cpu(i, sched_domain_span(child)))
            continue;

        sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
                GFP_KERNEL, cpu_to_node(cpu));

        if (!sg)
            goto fail;

        sg_span = sched_group_cpus(sg);
        if (child->child) {
            child = child->child;
            cpumask_copy(sg_span, sched_domain_span(child));
        } else
            cpumask_set_cpu(i, sg_span);

        cpumask_or(covered, covered, sg_span);

        sg->sgp = *per_cpu_ptr(sdd->sgp, i);
        if (atomic_inc_return(&sg->sgp->ref) == 1)
            build_group_mask(sd, sg);

        /*
         * Initialize sgp->power such that even if we mess up the
         * domains and no possible iteration will get us here, we won't
         * die on a /0 trap.
         */
        sg->sgp->power = SCHED_POWER_SCALE * cpumask_weight(sg_span);

        /*
         * Make sure the first group of this domain contains the
         * canonical balance cpu. Otherwise the sched_domain iteration
         * breaks. See update_sg_lb_stats().
         */
        if ((!groups && cpumask_test_cpu(cpu, sg_span)) ||
            group_balance_cpu(sg) == cpu)
            groups = sg;

        if (!first)
            first = sg;
        if (last)
            last->next = sg;
        last = sg;
        last->next = first;
    }
    sd->groups = groups;

    return 0;

fail:
    free_sched_groups(first, 0);

    return -ENOMEM;
}

static int get_group(int cpu, struct sd_data *sdd, struct sched_group **sg)
{
    struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu);
    struct sched_domain *child = sd->child;

    if (child)
        cpu = cpumask_first(sched_domain_span(child));

    if (sg) {
        *sg = *per_cpu_ptr(sdd->sg, cpu);
        (*sg)->sgp = *per_cpu_ptr(sdd->sgp, cpu);
        atomic_set(&(*sg)->sgp->ref, 1); /* for claim_allocations */
    }

    return cpu;
}

/*
 * build_sched_groups will build a circular linked list of the groups
 * covered by the given span, and will set each group's ->cpumask correctly,
 * and ->cpu_power to 0.
 *
 * Assumes the sched_domain tree is fully constructed
 */
static int
build_sched_groups(struct sched_domain *sd, int cpu)
{
    struct sched_group *first = NULL, *last = NULL;
    struct sd_data *sdd = sd->private;
    const struct cpumask *span = sched_domain_span(sd);
    struct cpumask *covered;
    int i;

    get_group(cpu, sdd, &sd->groups);
    atomic_inc(&sd->groups->ref);

    if (cpu != cpumask_first(sched_domain_span(sd)))
        return 0;

    lockdep_assert_held(&sched_domains_mutex);
    covered = sched_domains_tmpmask;

    cpumask_clear(covered);

    for_each_cpu(i, span) {
        struct sched_group *sg;
        int group = get_group(i, sdd, &sg);
        int j;

        if (cpumask_test_cpu(i, covered))
            continue;

        cpumask_clear(sched_group_cpus(sg));
        sg->sgp->power = 0;
        cpumask_setall(sched_group_mask(sg));

        for_each_cpu(j, span) {
            if (get_group(j, sdd, NULL) != group)
                continue;

            cpumask_set_cpu(j, covered);
            cpumask_set_cpu(j, sched_group_cpus(sg));
        }

        if (!first)
            first = sg;
        if (last)
            last->next = sg;
        last = sg;
    }
    last->next = first;

    return 0;
}

/*
 * Initialize sched groups cpu_power.
 *
 * cpu_power indicates the capacity of sched group, which is used while
 * distributing the load between different sched groups in a sched domain.
 * Typically cpu_power for all the groups in a sched domain will be same unless
 * there are asymmetries in the topology. If there are asymmetries, group
 * having more cpu_power will pickup more load compared to the group having
 * less cpu_power.
 */
static void init_sched_groups_power(int cpu, struct sched_domain *sd)
{
    struct sched_group *sg = sd->groups;

    WARN_ON(!sd || !sg);

    do {
        sg->group_weight = cpumask_weight(sched_group_cpus(sg));
        sg = sg->next;
    } while (sg != sd->groups);

    if (cpu != group_balance_cpu(sg))
        return;

    update_group_power(sd, cpu);
    atomic_set(&sg->sgp->nr_busy_cpus, sg->group_weight);
}

int __weak arch_sd_sibling_asym_packing(void)
{
       return 0*SD_ASYM_PACKING;
}

/*
 * Initializers for schedule domains
 * Non-inlined to reduce accumulated stack pressure in build_sched_domains()
 */

#ifdef CONFIG_SCHED_DEBUG
# define SD_INIT_NAME(sd, type)     sd->name = #type
#else
# define SD_INIT_NAME(sd, type)     do { } while (0)
#endif

#define SD_INIT_FUNC(type)                      \
static noinline struct sched_domain *                   \
sd_init_##type(struct sched_domain_topology_level *tl, int cpu)     \
{                                   \
    struct sched_domain *sd = *per_cpu_ptr(tl->data.sd, cpu);   \
    *sd = SD_##type##_INIT;                     \
    SD_INIT_NAME(sd, type);                     \
    sd->private = &tl->data;                    \
    return sd;                          \
}

SD_INIT_FUNC(CPU)
#ifdef CONFIG_SCHED_SMT
 SD_INIT_FUNC(SIBLING)
#endif
#ifdef CONFIG_SCHED_MC
 SD_INIT_FUNC(MC)
#endif
#ifdef CONFIG_SCHED_BOOK
 SD_INIT_FUNC(BOOK)
#endif

static int default_relax_domain_level = -1;
int sched_domain_level_max;

static int __init setup_relax_domain_level(char *str)
{
    if (kstrtoint(str, 0, &default_relax_domain_level))
        pr_warn("Unable to set relax_domain_level\n");

    return 1;
}
__setup("relax_domain_level=", setup_relax_domain_level);

static void set_domain_attribute(struct sched_domain *sd,
                 struct sched_domain_attr *attr)
{
    int request;

    if (!attr || attr->relax_domain_level < 0) {
        if (default_relax_domain_level < 0)
            return;
        else
            request = default_relax_domain_level;
    } else
        request = attr->relax_domain_level;
    if (request < sd->level) {
        /* turn off idle balance on this domain */
        sd->flags &= ~(SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
    } else {
        /* turn on idle balance on this domain */
        sd->flags |= (SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
    }
}

static void __sdt_free(const struct cpumask *cpu_map);
static int __sdt_alloc(const struct cpumask *cpu_map);

static void __free_domain_allocs(struct s_data *d, enum s_alloc what,
                 const struct cpumask *cpu_map)
{
    switch (what) {
    case sa_rootdomain:
        if (!atomic_read(&d->rd->refcount))
            free_rootdomain(&d->rd->rcu); /* fall through */
    case sa_sd:
        free_percpu(d->sd); /* fall through */
    case sa_sd_storage:
        __sdt_free(cpu_map); /* fall through */
    case sa_none:
        break;
    }
}

static enum s_alloc __visit_domain_allocation_hell(struct s_data *d,
                           const struct cpumask *cpu_map)
{
    memset(d, 0, sizeof(*d));

    if (__sdt_alloc(cpu_map))
        return sa_sd_storage;
    d->sd = alloc_percpu(struct sched_domain *);
    if (!d->sd)
        return sa_sd_storage;
    d->rd = alloc_rootdomain();
    if (!d->rd)
        return sa_sd;
    return sa_rootdomain;
}

/*
 * NULL the sd_data elements we've used to build the sched_domain and
 * sched_group structure so that the subsequent __free_domain_allocs()
 * will not free the data we're using.
 */
static void claim_allocations(int cpu, struct sched_domain *sd)
{
    struct sd_data *sdd = sd->private;

    WARN_ON_ONCE(*per_cpu_ptr(sdd->sd, cpu) != sd);
    *per_cpu_ptr(sdd->sd, cpu) = NULL;

    if (atomic_read(&(*per_cpu_ptr(sdd->sg, cpu))->ref))
        *per_cpu_ptr(sdd->sg, cpu) = NULL;

    if (atomic_read(&(*per_cpu_ptr(sdd->sgp, cpu))->ref))
        *per_cpu_ptr(sdd->sgp, cpu) = NULL;
}

#ifdef CONFIG_SCHED_SMT
static const struct cpumask *cpu_smt_mask(int cpu)
{
    return topology_thread_cpumask(cpu);
}
#endif

/*
 * Topology list, bottom-up.
 */
static struct sched_domain_topology_level default_topology[] = {
#ifdef CONFIG_SCHED_SMT
    { sd_init_SIBLING, cpu_smt_mask, },
#endif
#ifdef CONFIG_SCHED_MC
    { sd_init_MC, cpu_coregroup_mask, },
#endif
#ifdef CONFIG_SCHED_BOOK
    { sd_init_BOOK, cpu_book_mask, },
#endif
    { sd_init_CPU, cpu_cpu_mask, },
    { NULL, },
};

static struct sched_domain_topology_level *sched_domain_topology = default_topology;

#ifdef CONFIG_NUMA

static int sched_domains_numa_levels;
static int *sched_domains_numa_distance;
static struct cpumask ***sched_domains_numa_masks;
static int sched_domains_curr_level;

static inline int sd_local_flags(int level)
{
    if (sched_domains_numa_distance[level] > RECLAIM_DISTANCE)
        return 0;

    return SD_BALANCE_EXEC | SD_BALANCE_FORK | SD_WAKE_AFFINE;
}

static struct sched_domain *
sd_numa_init(struct sched_domain_topology_level *tl, int cpu)
{
    struct sched_domain *sd = *per_cpu_ptr(tl->data.sd, cpu);
    int level = tl->numa_level;
    int sd_weight = cpumask_weight(
            sched_domains_numa_masks[level][cpu_to_node(cpu)]);

    *sd = (struct sched_domain){
        .min_interval       = sd_weight,
        .max_interval       = 2*sd_weight,
        .busy_factor        = 32,
        .imbalance_pct      = 125,
        .cache_nice_tries   = 2,
        .busy_idx       = 3,
        .idle_idx       = 2,
        .newidle_idx        = 0,
        .wake_idx       = 0,
        .forkexec_idx       = 0,

        .flags          = 1*SD_LOAD_BALANCE
                    | 1*SD_BALANCE_NEWIDLE
                    | 0*SD_BALANCE_EXEC
                    | 0*SD_BALANCE_FORK
                    | 0*SD_BALANCE_WAKE
                    | 0*SD_WAKE_AFFINE
                    | 0*SD_SHARE_CPUPOWER
                    | 0*SD_SHARE_PKG_RESOURCES
                    | 1*SD_SERIALIZE
                    | 0*SD_PREFER_SIBLING
                    | sd_local_flags(level)
                    ,
        .last_balance       = jiffies,
        .balance_interval   = sd_weight,
    };
    SD_INIT_NAME(sd, NUMA);
    sd->private = &tl->data;

    /*
     * Ugly hack to pass state to sd_numa_mask()...
     */
    sched_domains_curr_level = tl->numa_level;

    return sd;
}

static const struct cpumask *sd_numa_mask(int cpu)
{
    return sched_domains_numa_masks[sched_domains_curr_level][cpu_to_node(cpu)];
}

static void sched_numa_warn(const char *str)
{
    static int done = false;
    int i,j;

    if (done)
        return;

    done = true;

    printk(KERN_WARNING "ERROR: %s\n\n", str);

    for (i = 0; i < nr_node_ids; i++) {
        printk(KERN_WARNING "  ");
        for (j = 0; j < nr_node_ids; j++)
            printk(KERN_CONT "%02d ", node_distance(i,j));
        printk(KERN_CONT "\n");
    }
    printk(KERN_WARNING "\n");
}

static bool find_numa_distance(int distance)
{
    int i;

    if (distance == node_distance(0, 0))
        return true;

    for (i = 0; i < sched_domains_numa_levels; i++) {
        if (sched_domains_numa_distance[i] == distance)
            return true;
    }

    return false;
}

static void sched_init_numa(void)
{
    int next_distance, curr_distance = node_distance(0, 0);
    struct sched_domain_topology_level *tl;
    int level = 0;
    int i, j, k;

    sched_domains_numa_distance = kzalloc(sizeof(int) * nr_node_ids, GFP_KERNEL);
    if (!sched_domains_numa_distance)
        return;

    /*
     * O(nr_nodes^2) deduplicating selection sort -- in order to find the
     * unique distances in the node_distance() table.
     *
     * Assumes node_distance(0,j) includes all distances in
     * node_distance(i,j) in order to avoid cubic time.
     */
    next_distance = curr_distance;
    for (i = 0; i < nr_node_ids; i++) {
        for (j = 0; j < nr_node_ids; j++) {
            for (k = 0; k < nr_node_ids; k++) {
                int distance = node_distance(i, k);

                if (distance > curr_distance &&
                    (distance < next_distance ||
                     next_distance == curr_distance))
                    next_distance = distance;

                /*
                 * While not a strong assumption it would be nice to know
                 * about cases where if node A is connected to B, B is not
                 * equally connected to A.
                 */
                if (sched_debug() && node_distance(k, i) != distance)
                    sched_numa_warn("Node-distance not symmetric");

                if (sched_debug() && i && !find_numa_distance(distance))
                    sched_numa_warn("Node-0 not representative");
            }
            if (next_distance != curr_distance) {
                sched_domains_numa_distance[level++] = next_distance;
                sched_domains_numa_levels = level;
                curr_distance = next_distance;
            } else break;
        }

        /*
         * In case of sched_debug() we verify the above assumption.
         */
        if (!sched_debug())
            break;
    }
    /*
     * 'level' contains the number of unique distances, excluding the
     * identity distance node_distance(i,i).
     *
     * The sched_domains_nume_distance[] array includes the actual distance
     * numbers.
     */

    /*
     * Here, we should temporarily reset sched_domains_numa_levels to 0.
     * If it fails to allocate memory for array sched_domains_numa_masks[][],
     * the array will contain less then 'level' members. This could be
     * dangerous when we use it to iterate array sched_domains_numa_masks[][]
     * in other functions.
     *
     * We reset it to 'level' at the end of this function.
     */
    sched_domains_numa_levels = 0;

    sched_domains_numa_masks = kzalloc(sizeof(void *) * level, GFP_KERNEL);
    if (!sched_domains_numa_masks)
        return;

    /*
     * Now for each level, construct a mask per node which contains all
     * cpus of nodes that are that many hops away from us.
     */
    for (i = 0; i < level; i++) {
        sched_domains_numa_masks[i] =
            kzalloc(nr_node_ids * sizeof(void *), GFP_KERNEL);
        if (!sched_domains_numa_masks[i])
            return;

        for (j = 0; j < nr_node_ids; j++) {
            struct cpumask *mask = kzalloc(cpumask_size(), GFP_KERNEL);
            if (!mask)
                return;

            sched_domains_numa_masks[i][j] = mask;

            for (k = 0; k < nr_node_ids; k++) {
                if (node_distance(j, k) > sched_domains_numa_distance[i])
                    continue;

                cpumask_or(mask, mask, cpumask_of_node(k));
            }
        }
    }

    tl = kzalloc((ARRAY_SIZE(default_topology) + level) *
            sizeof(struct sched_domain_topology_level), GFP_KERNEL);
    if (!tl)
        return;

    /*
     * Copy the default topology bits..
     */
    for (i = 0; default_topology[i].init; i++)
        tl[i] = default_topology[i];

    /*
     * .. and append 'j' levels of NUMA goodness.
     */
    for (j = 0; j < level; i++, j++) {
        tl[i] = (struct sched_domain_topology_level){
            .init = sd_numa_init,
            .mask = sd_numa_mask,
            .flags = SDTL_OVERLAP,
            .numa_level = j,
        };
    }

    sched_domain_topology = tl;

    sched_domains_numa_levels = level;
}

static void sched_domains_numa_masks_set(int cpu)
{
    int i, j;
    int node = cpu_to_node(cpu);

    for (i = 0; i < sched_domains_numa_levels; i++) {
        for (j = 0; j < nr_node_ids; j++) {
            if (node_distance(j, node) <= sched_domains_numa_distance[i])
                cpumask_set_cpu(cpu, sched_domains_numa_masks[i][j]);
        }
    }
}

static void sched_domains_numa_masks_clear(int cpu)
{
    int i, j;
    for (i = 0; i < sched_domains_numa_levels; i++) {
        for (j = 0; j < nr_node_ids; j++)
            cpumask_clear_cpu(cpu, sched_domains_numa_masks[i][j]);
    }
}

/*
 * Update sched_domains_numa_masks[level][node] array when new cpus
 * are onlined.
 */
static int sched_domains_numa_masks_update(struct notifier_block *nfb,
                       unsigned long action,
                       void *hcpu)
{
    int cpu = (long)hcpu;

    switch (action & ~CPU_TASKS_FROZEN) {
    case CPU_ONLINE:
        sched_domains_numa_masks_set(cpu);
        break;

    case CPU_DEAD:
        sched_domains_numa_masks_clear(cpu);
        break;

    default:
        return NOTIFY_DONE;
    }

    return NOTIFY_OK;
}
#else
static inline void sched_init_numa(void)
{
}

static int sched_domains_numa_masks_update(struct notifier_block *nfb,
                       unsigned long action,
                       void *hcpu)
{
    return 0;
}
#endif /* CONFIG_NUMA */

static int __sdt_alloc(const struct cpumask *cpu_map)
{
    struct sched_domain_topology_level *tl;
    int j;

    for (tl = sched_domain_topology; tl->init; tl++) {
        struct sd_data *sdd = &tl->data;

        sdd->sd = alloc_percpu(struct sched_domain *);
        if (!sdd->sd)
            return -ENOMEM;

        sdd->sg = alloc_percpu(struct sched_group *);
        if (!sdd->sg)
            return -ENOMEM;

        sdd->sgp = alloc_percpu(struct sched_group_power *);
        if (!sdd->sgp)
            return -ENOMEM;

        for_each_cpu(j, cpu_map) {
            struct sched_domain *sd;
            struct sched_group *sg;
            struct sched_group_power *sgp;

                sd = kzalloc_node(sizeof(struct sched_domain) + cpumask_size(),
                    GFP_KERNEL, cpu_to_node(j));
            if (!sd)
                return -ENOMEM;

            *per_cpu_ptr(sdd->sd, j) = sd;

            sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
                    GFP_KERNEL, cpu_to_node(j));
            if (!sg)
                return -ENOMEM;

            sg->next = sg;

            *per_cpu_ptr(sdd->sg, j) = sg;

            sgp = kzalloc_node(sizeof(struct sched_group_power) + cpumask_size(),
                    GFP_KERNEL, cpu_to_node(j));
            if (!sgp)
                return -ENOMEM;

            *per_cpu_ptr(sdd->sgp, j) = sgp;
        }
    }

    return 0;
}

static void __sdt_free(const struct cpumask *cpu_map)
{
    struct sched_domain_topology_level *tl;
    int j;

    for (tl = sched_domain_topology; tl->init; tl++) {
        struct sd_data *sdd = &tl->data;

        for_each_cpu(j, cpu_map) {
            struct sched_domain *sd;

            if (sdd->sd) {
                sd = *per_cpu_ptr(sdd->sd, j);
                if (sd && (sd->flags & SD_OVERLAP))
                    free_sched_groups(sd->groups, 0);
                kfree(*per_cpu_ptr(sdd->sd, j));
            }

            if (sdd->sg)
                kfree(*per_cpu_ptr(sdd->sg, j));
            if (sdd->sgp)
                kfree(*per_cpu_ptr(sdd->sgp, j));
        }
        free_percpu(sdd->sd);
        sdd->sd = NULL;
        free_percpu(sdd->sg);
        sdd->sg = NULL;
        free_percpu(sdd->sgp);
        sdd->sgp = NULL;
    }
}

struct sched_domain *build_sched_domain(struct sched_domain_topology_level *tl,
        struct s_data *d, const struct cpumask *cpu_map,
        struct sched_domain_attr *attr, struct sched_domain *child,
        int cpu)
{
    struct sched_domain *sd = tl->init(tl, cpu);
    if (!sd)
        return child;

    cpumask_and(sched_domain_span(sd), cpu_map, tl->mask(cpu));
    if (child) {
        sd->level = child->level + 1;
        sched_domain_level_max = max(sched_domain_level_max, sd->level);
        child->parent = sd;
    }
    sd->child = child;
    set_domain_attribute(sd, attr);

    return sd;
}

/*
 * Build sched domains for a given set of cpus and attach the sched domains
 * to the individual cpus
 */
static int build_sched_domains(const struct cpumask *cpu_map,
                   struct sched_domain_attr *attr)
{
    enum s_alloc alloc_state = sa_none;
    struct sched_domain *sd;
    struct s_data d;
    int i, ret = -ENOMEM;

    alloc_state = __visit_domain_allocation_hell(&d, cpu_map);
    if (alloc_state != sa_rootdomain)
        goto error;

    /* Set up domains for cpus specified by the cpu_map. */
    for_each_cpu(i, cpu_map) {
        struct sched_domain_topology_level *tl;

        sd = NULL;
        for (tl = sched_domain_topology; tl->init; tl++) {
            sd = build_sched_domain(tl, &d, cpu_map, attr, sd, i);
            if (tl->flags & SDTL_OVERLAP || sched_feat(FORCE_SD_OVERLAP))
                sd->flags |= SD_OVERLAP;
            if (cpumask_equal(cpu_map, sched_domain_span(sd)))
                break;
        }

        while (sd->child)
            sd = sd->child;

        *per_cpu_ptr(d.sd, i) = sd;
    }

    /* Build the groups for the domains */
    for_each_cpu(i, cpu_map) {
        for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
            sd->span_weight = cpumask_weight(sched_domain_span(sd));
            if (sd->flags & SD_OVERLAP) {
                if (build_overlap_sched_groups(sd, i))
                    goto error;
            } else {
                if (build_sched_groups(sd, i))
                    goto error;
            }
        }
    }

    /* Calculate CPU power for physical packages and nodes */
    for (i = nr_cpumask_bits-1; i >= 0; i--) {
        if (!cpumask_test_cpu(i, cpu_map))
            continue;

        for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
            claim_allocations(i, sd);
            init_sched_groups_power(i, sd);
        }
    }

    /* Attach the domains */
    rcu_read_lock();
    for_each_cpu(i, cpu_map) {
        sd = *per_cpu_ptr(d.sd, i);
        cpu_attach_domain(sd, d.rd, i);
    }
    rcu_read_unlock();

    ret = 0;
error:
    __free_domain_allocs(&d, alloc_state, cpu_map);
    return ret;
}

static cpumask_var_t *doms_cur; /* current sched domains */
static int ndoms_cur;       /* number of sched domains in 'doms_cur' */
static struct sched_domain_attr *dattr_cur;
                /* attribues of custom domains in 'doms_cur' */

/*
 * Special case: If a kmalloc of a doms_cur partition (array of
 * cpumask) fails, then fallback to a single sched domain,
 * as determined by the single cpumask fallback_doms.
 */
static cpumask_var_t fallback_doms;

/*
 * arch_update_cpu_topology lets virtualized architectures update the
 * cpu core maps. It is supposed to return 1 if the topology changed
 * or 0 if it stayed the same.
 */
int __attribute__((weak)) arch_update_cpu_topology(void)
{
    return 0;
}

cpumask_var_t *alloc_sched_domains(unsigned int ndoms)
{
    int i;
    cpumask_var_t *doms;

    doms = kmalloc(sizeof(*doms) * ndoms, GFP_KERNEL);
    if (!doms)
        return NULL;
    for (i = 0; i < ndoms; i++) {
        if (!alloc_cpumask_var(&doms[i], GFP_KERNEL)) {
            free_sched_domains(doms, i);
            return NULL;
        }
    }
    return doms;
}

void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms)
{
    unsigned int i;
    for (i = 0; i < ndoms; i++)
        free_cpumask_var(doms[i]);
    kfree(doms);
}

/*
 * Set up scheduler domains and groups. Callers must hold the hotplug lock.
 * For now this just excludes isolated cpus, but could be used to
 * exclude other special cases in the future.
 */
static int init_sched_domains(const struct cpumask *cpu_map)
{
    int err;

    arch_update_cpu_topology();
    ndoms_cur = 1;
    doms_cur = alloc_sched_domains(ndoms_cur);
    if (!doms_cur)
        doms_cur = &fallback_doms;
    cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map);
    err = build_sched_domains(doms_cur[0], NULL);
    register_sched_domain_sysctl();

    return err;
}

/*
 * Detach sched domains from a group of cpus specified in cpu_map
 * These cpus will now be attached to the NULL domain
 */
static void detach_destroy_domains(const struct cpumask *cpu_map)
{
    int i;

    rcu_read_lock();
    for_each_cpu(i, cpu_map)
        cpu_attach_domain(NULL, &def_root_domain, i);
    rcu_read_unlock();
}

/* handle null as "default" */
static int dattrs_equal(struct sched_domain_attr *cur, int idx_cur,
            struct sched_domain_attr *new, int idx_new)
{
    struct sched_domain_attr tmp;

    /* fast path */
    if (!new && !cur)
        return 1;

    tmp = SD_ATTR_INIT;
    return !memcmp(cur ? (cur + idx_cur) : &tmp,
            new ? (new + idx_new) : &tmp,
            sizeof(struct sched_domain_attr));
}

/*
 * Partition sched domains as specified by the 'ndoms_new'
 * cpumasks in the array doms_new[] of cpumasks. This compares
 * doms_new[] to the current sched domain partitioning, doms_cur[].
 * It destroys each deleted domain and builds each new domain.
 *
 * 'doms_new' is an array of cpumask_var_t's of length 'ndoms_new'.
 * The masks don't intersect (don't overlap.) We should setup one
 * sched domain for each mask. CPUs not in any of the cpumasks will
 * not be load balanced. If the same cpumask appears both in the
 * current 'doms_cur' domains and in the new 'doms_new', we can leave
 * it as it is.
 *
 * The passed in 'doms_new' should be allocated using
 * alloc_sched_domains.  This routine takes ownership of it and will
 * free_sched_domains it when done with it. If the caller failed the
 * alloc call, then it can pass in doms_new == NULL && ndoms_new == 1,
 * and partition_sched_domains() will fallback to the single partition
 * 'fallback_doms', it also forces the domains to be rebuilt.
 *
 * If doms_new == NULL it will be replaced with cpu_online_mask.
 * ndoms_new == 0 is a special case for destroying existing domains,
 * and it will not create the default domain.
 *
 * Call with hotplug lock held
 */
void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
                 struct sched_domain_attr *dattr_new)
{
    int i, j, n;
    int new_topology;

    mutex_lock(&sched_domains_mutex);

    /* always unregister in case we don't destroy any domains */
    unregister_sched_domain_sysctl();