SUNRPC: If the rpcbind channel is disconnected, fail the call to unregister

[linux-imx.git] / kernel / sched / core.c

/*
 *  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 <linux/context_tracking.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_internal.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 int sched_feat_set(char *cmp)
{
        int i;
        int neg = 0;

        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;
                }
        }

        return i;
}

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 i;

        if (cnt > 63)
                cnt = 63;

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

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

        i = sched_feat_set(cmp);
        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.
 */

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

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

        return __hrtimer_start_range_ns(timer, time, 0, HRTIMER_MODE_ABS_PINNED, 0);
}

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

        raw_spin_lock(&rq->lock);
        __hrtick_restart(rq);
        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()) {
                __hrtick_restart(rq);
        } 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
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_COMMON
/*
 * In the semi idle case, use the nearest busy cpu for migrating timers
 * from an idle cpu.  This is good for power-savings.
 *
 * We don't do similar optimization for completely idle system, as
 * selecting an idle cpu will add more delays to the timers than intended
 * (as that cpu's timer base may not be uptodate wrt jiffies etc).
 */
int get_nohz_timer_target(void)
{
        int 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.
 */
static 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 bool wake_up_full_nohz_cpu(int cpu)
{
        if (tick_nohz_full_cpu(cpu)) {
                if (cpu != smp_processor_id() ||
                    tick_nohz_tick_stopped())
                        smp_send_reschedule(cpu);
                return true;
        }

        return false;
}

void wake_up_nohz_cpu(int cpu)
{
        if (!wake_up_full_nohz_cpu(cpu))
                wake_up_idle_cpu(cpu);
}

static inline bool got_nohz_idle_kick(void)
{
        int cpu = smp_processor_id();

        if (!test_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu)))
                return false;

        if (idle_cpu(cpu) && !need_resched())
                return true;

        /*
         * We can't run Idle Load Balance on this CPU for this time so we
         * cancel it and clear NOHZ_BALANCE_KICK
         */
        clear_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu));
        return false;
}

#else /* CONFIG_NO_HZ_COMMON */

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

#endif /* CONFIG_NO_HZ_COMMON */

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

       rq = this_rq();

       /* Make sure rq->nr_running update is visible after the IPI */
       smp_rmb();

       /* More than one running task need preemption */
       if (rq->nr_running > 1)
               return false;

       return true;
}
#endif /* CONFIG_NO_HZ_FULL */

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

        while ((s64)(rq_clock(rq) - 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;
}

/**
 * task_curr - is this task currently executing on a CPU?
 * @p: the task in question.
 */
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;
}

static ATOMIC_NOTIFIER_HEAD(task_migration_notifier);

void register_task_migration_notifier(struct notifier_block *n)
{
        atomic_notifier_chain_register(&task_migration_notifier, n);
}

#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) {
                struct task_migration_notifier tmn;

                if (p->sched_class->migrate_task_rq)
                        p->sched_class->migrate_task_rq(p, new_cpu);
                p->se.nr_migrations++;
                perf_sw_event(PERF_COUNT_SW_CPU_MIGRATIONS, 1, NULL, 0);

                tmn.task = p;
                tmn.from_cpu = task_cpu(p);
                tmn.to_cpu = new_cpu;

                atomic_notifier_call_chain(&task_migration_notifier, 0, &tmn);
        }

        __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)
{
        int nid = cpu_to_node(cpu);
        const struct cpumask *nodemask = NULL;
        enum { cpuset, possible, fail } state = cpuset;
        int dest_cpu;

        /*
         * If the node that the cpu is on has been offlined, cpu_to_node()
         * will return -1. There is no cpu on the node, and we should
         * select the cpu on the other node.
         */
        if (nid != -1) {
                nodemask = cpumask_of_node(nid);

                /* 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)
{
        check_preempt_curr(rq, p, wake_flags);
        trace_sched_wakeup(p, true);

        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) - 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) {
                /* check_preempt_curr() may use rq clock */
                update_rq_clock(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)
                        && !tick_nohz_full_cpu(smp_processor_id())
                        && !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();
        tick_nohz_full_check();
        sched_ttwu_pending();

        /*
         * Check if someone kicked us for doing the nohz idle load balance.
         */
        if (unlikely(got_nohz_idle_kick())) {
                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);
}

/**
 * try_to_wake_up - wake up a thread
 * @p: the thread to be awakened
 * @state: the mask of task states that can be woken
 * @wake_flags: wake modifier flags (WF_*)
 *
 * Put it on the run-queue if it's not already there. The "current"
 * thread is always on the run-queue (except when the actual
 * re-schedule is in progress), and as such you're allowed to do
 * the simpler "current->state = TASK_RUNNING" to mark yourself
 * runnable without the overhead of this.
 *
 * Returns %true if @p was woken up, %false if it was already running
 * or @state didn't match @p's state.
 */
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;
}

/**
 * try_to_wake_up_local - try to wake up a local task with rq lock held
 * @p: the thread to be awakened
 *
 * Put @p on the run-queue if it's not already there. The caller must
 * ensure that this_rq() is locked, @p is bound to this_rq() and not
 * the current task.
 */
static void try_to_wake_up_local(struct task_struct *p)
{
        struct rq *rq = task_rq(p);

        if (WARN_ON_ONCE(rq != this_rq()) ||
            WARN_ON_ONCE(p == current))
                return;

        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);
}

/**
 * wake_up_process - Wake up a specific process
 * @p: The process to be woken up.
 *
 * Attempt to wake up the nominated process and move it to the set of runnable
 * processes.  Returns 1 if the process was woken up, 0 if it was already
 * running.
 *
 * It may be assumed that this function implies a write memory barrier before
 * changing the task state if and only if any tasks are woken up.
 */
int wake_up_process(struct task_struct *p)
{
        WARN_ON(task_is_stopped_or_traced(p));
        return try_to_wake_up(p, TASK_NORMAL, 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

#ifdef CONFIG_NUMA_BALANCING
        if (p->mm && atomic_read(&p->mm->mm_users) == 1) {
                p->mm->numa_next_scan = jiffies;
                p->mm->numa_next_reset = jiffies;
                p->mm->numa_scan_seq = 0;
        }

        p->node_stamp = 0ULL;
        p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0;
        p->numa_migrate_seq = p->mm ? p->mm->numa_scan_seq - 1 : 0;
        p->numa_scan_period = sysctl_numa_balancing_scan_delay;
        p->numa_work.next = &p->numa_work;
#endif /* CONFIG_NUMA_BALANCING */
}

#ifdef CONFIG_NUMA_BALANCING
#ifdef CONFIG_SCHED_DEBUG
void set_numabalancing_state(bool enabled)
{
        if (enabled)
                sched_feat_set("NUMA");
        else
                sched_feat_set("NO_NUMA");
}
#else
__read_mostly bool numabalancing_enabled;

void set_numabalancing_state(bool enabled)
{
        numabalancing_enabled = enabled;
}
#endif /* CONFIG_SCHED_DEBUG */
#endif /* CONFIG_NUMA_BALANCING */

/*
 * 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

        /* Initialize new task's runnable average */
        init_task_runnable_average(p);
        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

/**
 * preempt_notifier_register - tell me when current is being preempted & rescheduled
 * @notifier: notifier struct to register
 */
void preempt_notifier_register(struct preempt_notifier *notifier)
{
        hlist_add_head(&notifier->link, &current->preempt_notifiers);
}
EXPORT_SYMBOL_GPL(preempt_notifier_register);

/**
 * preempt_notifier_unregister - no longer interested in preemption notifications
 * @notifier: notifier struct to unregister
 *
 * This is safe to call from within a preemption notifier.
 */
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;

        hlist_for_each_entry(notifier, &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;

        hlist_for_each_entry(notifier, &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 */

/**
 * prepare_task_switch - prepare to switch tasks
 * @rq: the runqueue preparing to switch
 * @prev: the current task that is being switched out
 * @next: the task we are going to switch to.
 *
 * This is called with the rq lock held and interrupts off. It must
 * be paired with a subsequent finish_task_switch after the context
 * switch.
 *
 * prepare_task_switch sets up locking and calls architecture specific
 * hooks.
 */
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);
}

/**
 * finish_task_switch - clean up after a task-switch
 * @rq: runqueue associated with task-switch
 * @prev: the thread we just switched away from.
 *
 * finish_task_switch must be called after the context switch, paired
 * with a prepare_task_switch call before the context switch.
 * finish_task_switch will reconcile locking set up by prepare_task_switch,
 * and do any other architecture-specific cleanup actions.
 *
 * Note that we may have delayed dropping an mm in context_switch(). If
 * so, we finish that here outside of the runqueue lock. (Doing it
 * with the lock held can cause deadlocks; see schedule() for
 * details.)
 */
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 <manfred@colorfullife.com>
         */
        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);
        }

        tick_nohz_task_switch(current);
}

#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

/**
 * schedule_tail - first thing a freshly forked thread must call.
 * @prev: the thread we just switched away from.
 */
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

        context_tracking_task_switch(prev, next);
        /* Here we just switch the register state and the stack. */
        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 and nr_context_switches:
 *
 * externally visible scheduler statistics: current number of runnable
 * 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 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);
}

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

        perf_event_task_tick();

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

#ifdef CONFIG_NO_HZ_FULL
/**
 * scheduler_tick_max_deferment
 *
 * Keep at least one tick per second when a single
 * active task is running because the scheduler doesn't
 * yet completely support full dynticks environment.
 *
 * This makes sure that uptime, CFS vruntime, load
 * balancing, etc... continue to move forward, even
 * with a very low granularity.
 */
u64 scheduler_tick_max_deferment(void)
{
        struct rq *rq = this_rq();
        unsigned long next, now = ACCESS_ONCE(jiffies);

        next = rq->last_sched_tick + HZ;

        if (time_before_eq(next, now))
                return 0;

        return jiffies_to_usecs(next - now) * NSEC_PER_USEC;
}
#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, LOCKDEP_STILL_OK);
}

/*
 * 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_CONTEXT_TRACKING
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.
         */
        user_exit();
        schedule();
        user_enter();
}
#endif

/**
 * schedule_preempt_disabled - called with preemption disabled
 *
 * Returns with preemption disabled. Note: preempt_count must be 1
 */
void __sched schedule_preempt_disabled(void)
{
        sched_preempt_enable_no_resched();
        schedule();
        preempt_disable();
}

#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();
        enum ctx_state prev_state;

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

        prev_state = exception_enter();

        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());

        exception_exit(prev_state);
}

#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;
        }
}

/**
 * __wake_up - wake up threads blocked on a waitqueue.
 * @q: the waitqueue
 * @mode: which threads
 * @nr_exclusive: how many wake-one or wake-many threads to wake up
 * @key: is directly passed to the wakeup function
 *
 * It may be assumed that this function implies a write memory barrier before
 * changing the task state if and only if any tasks are woken up.
 */
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);

/**
 * __wake_up_sync_key - wake up threads blocked on a waitqueue.
 * @q: the waitqueue
 * @mode: which threads
 * @nr_exclusive: how many wake-one or wake-many threads to wake up
 * @key: opaque value to be passed to wakeup targets
 *
 * The sync wakeup differs that the waker knows that it will schedule
 * away soon, so while the target thread will be woken up, it will not
 * be migrated to another CPU - ie. the two threads are 'synchronized'
 * with each other. This can prevent needless bouncing between CPUs.
 *
 * On UP it can prevent extra preemption.
 *
 * It may be assumed that this function implies a write memory barrier before
 * changing the task state if and only if any tasks are woken up.
 */
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 */

/**
 * complete: - signals a single thread waiting on this completion
 * @x:  holds the state of this particular completion
 *
 * This will wake up a single thread waiting on this completion. Threads will be
 * awakened in the same order in which they were queued.
 *
 * See also complete_all(), wait_for_completion() and related routines.
 *
 * It may be assumed that this function implies a write memory barrier before
 * changing the task state if and only if any tasks are woken up.
 */
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);

/**
 * complete_all: - signals all threads waiting on this completion
 * @x:  holds the state of this particular completion
 *
 * This will wake up all threads waiting on this particular completion event.
 *
 * It may be assumed that this function implies a write memory barrier before
 * changing the task state if and only if any tasks are woken up.
 */
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 (*action)(long), 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 = action(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 inline long __sched
__wait_for_common(struct completion *x,
                  long (*action)(long), long timeout, int state)
{
        might_sleep();

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

static long __sched
wait_for_common(struct completion *x, long timeout, int state)
{
        return __wait_for_common(x, schedule_timeout, timeout, state);
}

static long __sched
wait_for_common_io(struct completion *x, long timeout, int state)
{
        return __wait_for_common(x, io_schedule_timeout, timeout, state);
}

/**
 * wait_for_completion: - waits for completion of a task
 * @x:  holds the state of this particular completion
 *
 * This waits to be signaled for completion of a specific task. It is NOT
 * interruptible and there is no timeout.
 *
 * See also similar routines (i.e. wait_for_completion_timeout()) with timeout
 * and interrupt capability. Also see complete().
 */
void __sched wait_for_completion(struct completion *x)
{
        wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(wait_for_completion);

/**
 * wait_for_completion_timeout: - waits for completion of a task (w/timeout)
 * @x:  holds the state of this particular completion
 * @timeout:  timeout value in jiffies
 *
 * This waits for either a completion of a specific task to be signaled or for a
 * specified timeout to expire. The timeout is in jiffies. It is not
 * interruptible.
 *
 * The return value is 0 if timed out, and positive (at least 1, or number of
 * jiffies left till timeout) if completed.
 */
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);

/**
 * wait_for_completion_io: - waits for completion of a task
 * @x:  holds the state of this particular completion
 *
 * This waits to be signaled for completion of a specific task. It is NOT
 * interruptible and there is no timeout. The caller is accounted as waiting
 * for IO.
 */
void __sched wait_for_completion_io(struct completion *x)
{
        wait_for_common_io(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(wait_for_completion_io);

/**
 * wait_for_completion_io_timeout: - waits for completion of a task (w/timeout)
 * @x:  holds the state of this particular completion
 * @timeout:  timeout value in jiffies
 *
 * This waits for either a completion of a specific task to be signaled or for a
 * specified timeout to expire. The timeout is in jiffies. It is not
 * interruptible. The caller is accounted as waiting for IO.
 *
 * The return value is 0 if timed out, and positive (at least 1, or number of
 * jiffies left till timeout) if completed.
 */
unsigned long __sched
wait_for_completion_io_timeout(struct completion *x, unsigned long timeout)
{
        return wait_for_common_io(x, timeout, TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(wait_for_completion_io_timeout);

/**
 * wait_for_completion_interruptible: - waits for completion of a task (w/intr)
 * @x:  holds the state of this particular completion
 *
 * This waits for completion of a specific task to be signaled. It is
 * interruptible.
 *
 * The return value is -ERESTARTSYS if interrupted, 0 if completed.
 */
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);

/**
 * wait_for_completion_interruptible_timeout: - waits for completion (w/(to,intr))
 * @x:  holds the state of this particular completion
 * @timeout:  timeout value in jiffies
 *
 * This waits for either a completion of a specific task to be signaled or for a
 * specified timeout to expire. It is interruptible. The timeout is in jiffies.
 *
 * The return value is -ERESTARTSYS if interrupted, 0 if timed out,
 * positive (at least 1, or number of jiffies left till timeout) if completed.
 */
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);

/**
 * wait_for_completion_killable: - waits for completion of a task (killable)
 * @x:  holds the state of this particular completion
 *
 * This waits to be signaled for completion of a specific task. It can be
 * interrupted by a kill signal.
 *
 * The return value is -ERESTARTSYS if interrupted, 0 if completed.
 */
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);

/**
 * wait_for_completion_killable_timeout: - waits for completion of a task (w/(to,killable))
 * @x:  holds the state of this particular completion
 * @timeout:  timeout value in jiffies
 *
 * This waits for either a completion of a specific task to be
 * signaled or for a specified timeout to expire. It can be
 * interrupted by a kill signal. The timeout is in jiffies.
 *
 * The return value is -ERESTARTSYS if interrupted, 0 if timed out,
 * positive (at least 1, or number of jiffies left till timeout) if completed.
 */
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);

/**
 *      try_wait_for_completion - try to decrement a completion without blocking
 *      @x:     completion structure
 *
 *      Returns: 0 if a decrement cannot be done without blocking
 *               1 if a decrement succeeded.
 *
 *      If a completion is being used as a counting completion,
 *      attempt to decrement the counter without blocking. This
 *      enables us to avoid waiting if the resource the completion
 *      is protecting is not available.
 */
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);

/**
 *      completion_done - Test to see if a completion has any waiters
 *      @x:     completion structure
 *
 *      Returns: 0 if there are waiters (wait_for_completion() in progress)
 *               1 if there are no waiters.
 *
 */
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

/**
 * task_prio - return the priority value of a given task.
 * @p: the task in question.
 *
 * This is the priority value as seen by users in /proc.
 * RT tasks are offset by -200. Normal tasks are centered
 * around 0, value goes from -16 to +15.
 */
int task_prio(const struct task_struct *p)
{
        return p->prio - MAX_RT_PRIO;
}

/**
 * task_nice - return the nice value of a given task.
 * @p: the task in question.
 */
int task_nice(const struct task_struct *p)
{
        return TASK_NICE(p);
}
EXPORT_SYMBOL(task_nice);

/**
 * idle_cpu - is a given cpu idle currently?
 * @cpu: the processor in question.
 */
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;
}

/**
 * idle_task - return the idle task for a given cpu.
 * @cpu: the processor in question.
 */
struct task_struct *idle_task(int cpu)
{
        return cpu_rq(cpu)->idle;
}

/**
 * find_process_by_pid - find a process with a matching PID value.
 * @pid: the pid in question.
 */
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;
}

/**
 * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
 * @p: the task in question.
 * @policy: new policy.
 * @param: structure containing the new RT priority.
 *
 * NOTE that the task may be already dead.
 */
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);

/**
 * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
 * @p: the task in question.
 * @policy: new policy.
 * @param: structure containing the new RT priority.
 *
 * Just like sched_setscheduler, only don't bother checking if the
 * current context has permission.  For example, this is needed in
 * stop_machine(): we create temporary high priority worker threads,
 * but our caller might not have that capability.
 */
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;
}

/**
 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
 * @pid: the pid in question.
 * @policy: new policy.
 * @param: structure containing the new RT priority.
 */
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);
}

/**
 * sys_sched_setparam - set/change the RT priority of a thread
 * @pid: the pid in question.
 * @param: structure containing the new RT priority.
 */
SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
{
        return do_sched_setscheduler(pid, -1, param);
}

/**
 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
 * @pid: the pid in question.
 */
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;
}

/**
 * sys_sched_getparam - get the RT priority of a thread
 * @pid: the pid in question.
 * @param: structure containing the RT priority.
 */
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 (p->flags & PF_NO_SETAFFINITY) {
                retval = -EINVAL;
                goto out_put_task;
        }
        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)) {
                rcu_read_lock();
                if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
                        rcu_read_unlock();
                        goto out_unlock;
                }
                rcu_read_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;
}

/**
 * sys_sched_setaffinity - set the cpu affinity of a process
 * @pid: pid of the process
 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
 * @user_mask_ptr: user-space pointer to the new cpu mask
 */
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;
}

/**
 * sys_sched_getaffinity - get the cpu affinity of a process
 * @pid: pid of the process
 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
 * @user_mask_ptr: user-space pointer to hold the current cpu mask
 */
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;
}

/**
 * sys_sched_yield - yield the current processor to other threads.
 *
 * This function yields the current CPU to other tasks. If there are no
 * other threads running on this CPU then this function will return.
 */
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);

/**
 * yield - yield the current processor to other threads.
 *
 * Do not ever use this function, there's a 99% chance you're doing it wrong.
 *
 * The scheduler is at all times free to pick the calling task as the most
 * eligible task to run, if removing the yield() call from your code breaks
 * it, its already broken.
 *
 * Typical broken usage is:
 *
 * while (!event)
 *      yield();
 *
 * where one assumes that yield() will let 'the other' process run that will
 * make event true. If the current task is a SCHED_FIFO task that will never
 * happen. Never use yield() as a progress guarantee!!
 *
 * If you want to use yield() to wait for something, use wait_event().
 * If you want to use yield() to be 'nice' for others, use cond_resched().
 * If you still want to use yield(), do not!
 */
void __sched yield(void)
{
        set_current_state(TASK_RUNNING);
        sys_sched_yield();
}
EXPORT_SYMBOL(yield);

/**
 * yield_to - yield the current processor to another thread in
 * your thread group, or accelerate that thread toward the
 * processor it's on.
 * @p: target task
 * @preempt: whether task preemption is allowed or not
 *
 * It's the caller's job to ensure that the target task struct
 * can't go away on us before we can do any checks.
 *
 * Returns:
 *      true (>0) if we indeed boosted the target task.
 *      false (0) if we failed to boost the target.
 *      -ESRCH if there's no task to yield to.
 */
bool __sched yield_to(struct task_struct *p, bool preempt)
{
        struct task_struct *curr = current;
        struct rq *rq, *p_rq;
        unsigned long flags;
        int yielded = 0;

        local_irq_save(flags);
        rq = this_rq();

again:
        p_rq = task_rq(p);
        /*
         * If we're the only runnable task on the rq and target rq also
         * has only one task, there's absolutely no point in yielding.
         */
        if (rq->nr_running == 1 && p_rq->nr_running == 1) {
                yielded = -ESRCH;
                goto out_irq;
        }

        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_unlock;

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

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

        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_unlock:
        double_rq_unlock(rq, p_rq);
out_irq:
        local_irq_restore(flags);

        if (yielded > 0)
                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;
}

/**
 * sys_sched_get_priority_max - return maximum RT priority.
 * @policy: scheduling class.
 *
 * this syscall returns the maximum rt_priority that can be used
 * by a given scheduling class.
 */
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;
}

/**
 * sys_sched_get_priority_min - return minimum RT priority.
 * @policy: scheduling class.
 *
 * this syscall returns the minimum rt_priority that can be used
 * by a given scheduling class.
 */
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;
}

/**
 * sys_sched_rr_get_interval - return the default timeslice of a process.
 * @pid: pid of the process.
 * @interval: userspace pointer to the timeslice value.
 *
 * this syscall writes the default timeslice value of a given process
 * into the user-space timespec buffer. A value of '0' means infinity.
 */
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;
        int ppid;
        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
        rcu_read_lock();
        ppid = task_pid_nr(rcu_dereference(p->real_parent));
        rcu_read_unlock();
        printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free,
                task_pid_nr(p), ppid,
                (unsigned long)task_thread_info(p)->flags);

        print_worker_info(KERN_INFO, p);
        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 init_idle_bootup_task(struct task_struct *idle)
{
        idle->sched_class = &idle_sched_class;
}

/**
 * init_idle - set up an idle thread for a given CPU
 * @idle: task in question
 * @cpu: cpu the idle task belongs to
 *
 * NOTE: this function does not set the idle thread's NEED_RESCHED
 * flag, to make booting more robust.
 */
void 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);
        vtime_init_idle(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;
        }

        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;

        /*
         * put_prev_task() and pick_next_task() sched
         * class method both need to have an up-to-date
         * value of rq->clock[_task]
         */
        update_rq_clock(rq);

        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-1;

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 struct 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
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 migration_notifier = {
        .notifier_call = migration_call,
        .priority = CPU_PRI_MIGRATION,
};

static int 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 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(span))
                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, j;

                if (cpumask_test_cpu(i, covered))
                        continue;

                group = get_group(i, sdd, &sg);
                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(!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;

#define for_each_sd_topology(tl)                        \
        for (tl = sched_domain_topology; tl->init; tl++)

#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_numa_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_each_sd_topology(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_each_sd_topology(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,
                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;
        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_each_sd_topology(tl) {
                        sd = build_sched_domain(tl, cpu_map, attr, sd, i);
                        if (tl == sched_domain_topology)
                                *per_cpu_ptr(d.sd, i) = sd;
                        if (tl->flags & SDTL_OVERLAP || sched_feat(FORCE_SD_OVERLAP))
                                sd->flags |= SD_OVERLAP;
                        if (cpumask_equal(cpu_map, sched_domain_span(sd)))
                                break;
                }
        }

        /* 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();

        /* Let architecture update cpu core mappings. */
        new_topology = arch_update_cpu_topology();

        n = doms_new ? ndoms_new : 0;

        /* Destroy deleted domains */
        for (i = 0; i < ndoms_cur; i++) {
                for (j = 0; j < n && !new_topology; j++) {
                        if (cpumask_equal(doms_cur[i], doms_new[j])
                            && dattrs_equal(dattr_cur, i, dattr_new, j))
                                goto match1;
                }
                /* no match - a current sched domain not in new doms_new[] */
                detach_destroy_domains(doms_cur[i]);
match1:
                ;
        }

        if (doms_new == NULL) {
                ndoms_cur = 0;
                doms_new = &fallback_doms;
                cpumask_andnot(doms_new[0], cpu_active_mask, cpu_isolated_map);
                WARN_ON_ONCE(dattr_new);
        }

        /* Build new domains */
        for (i = 0; i < ndoms_new; i++) {
                for (j = 0; j < ndoms_cur && !new_topology; j++) {
                        if (cpumask_equal(doms_new[i], doms_cur[j])
                            && dattrs_equal(dattr_new, i, dattr_cur, j))
                                goto match2;
                }
                /* no match - add a new doms_new */
                build_sched_domains(doms_new[i], dattr_new ? dattr_new + i : NULL);
match2:
                ;
        }

        /* Remember the new sched domains */
        if (doms_cur != &fallback_doms)
                free_sched_domains(doms_cur, ndoms_cur);
        kfree(dattr_cur);       /* kfree(NULL) is safe */
        doms_cur = doms_new;
        dattr_cur = dattr_new;
        ndoms_cur = ndoms_new;

        register_sched_domain_sysctl();

        mutex_unlock(&sched_domains_mutex);
}

static int num_cpus_frozen;     /* used to mark begin/end of suspend/resume */

/*
 * Update cpusets according to cpu_active mask.  If cpusets are
 * disabled, cpuset_update_active_cpus() becomes a simple wrapper
 * around partition_sched_domains().
 *
 * If we come here as part of a suspend/resume, don't touch cpusets because we
 * want to restore it back to its original state upon resume anyway.
 */
static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
                             void *hcpu)
{
        switch (action) {
        case CPU_ONLINE_FROZEN:
        case CPU_DOWN_FAILED_FROZEN:

                /*
                 * num_cpus_frozen tracks how many CPUs are involved in suspend
                 * resume sequence. As long as this is not the last online
                 * operation in the resume sequence, just build a single sched
                 * domain, ignoring cpusets.
                 */
                num_cpus_frozen--;
                if (likely(num_cpus_frozen)) {
                        partition_sched_domains(1, NULL, NULL);
                        break;
                }

                /*
                 * This is the last CPU online operation. So fall through and
                 * restore the original sched domains by considering the
                 * cpuset configurations.
                 */

        case CPU_ONLINE:
        case CPU_DOWN_FAILED:
                cpuset_update_active_cpus(true);
                break;
        default:
                return NOTIFY_DONE;
        }
        return NOTIFY_OK;
}

static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,
                               void *hcpu)
{
        switch (action) {
        case CPU_DOWN_PREPARE:
                cpuset_update_active_cpus(false);
                break;
        case CPU_DOWN_PREPARE_FROZEN:
                num_cpus_frozen++;
                partition_sched_domains(1, NULL, NULL);
                break;
        default:
                return NOTIFY_DONE;
        }
        return NOTIFY_OK;
}

void __init sched_init_smp(void)
{
        cpumask_var_t non_isolated_cpus;

        alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL);
        alloc_cpumask_var(&fallback_doms, GFP_KERNEL);

        sched_init_numa();

        get_online_cpus();
        mutex_lock(&sched_domains_mutex);
        init_sched_domains(cpu_active_mask);
        cpumask_andnot(non_isolated_cpus, cpu_possible_mask, cpu_isolated_map);
        if (cpumask_empty(non_isolated_cpus))
                cpumask_set_cpu(smp_processor_id(), non_isolated_cpus);
        mutex_unlock(&sched_domains_mutex);
        put_online_cpus();

        hotcpu_notifier(sched_domains_numa_masks_update, CPU_PRI_SCHED_ACTIVE);
        hotcpu_notifier(cpuset_cpu_active, CPU_PRI_CPUSET_ACTIVE);
        hotcpu_notifier(cpuset_cpu_inactive, CPU_PRI_CPUSET_INACTIVE);

        init_hrtick();

        /* Move init over to a non-isolated CPU */
        if (set_cpus_allowed_ptr(current, non_isolated_cpus) < 0)
                BUG();
        sched_init_granularity();
        free_cpumask_var(non_isolated_cpus);

        init_sched_rt_class();
}
#else
void __init sched_init_smp(void)
{
        sched_init_granularity();
}
#endif /* CONFIG_SMP */

const_debug unsigned int sysctl_timer_migration = 1;

int in_sched_functions(unsigned long addr)
{
        return in_lock_functions(addr) ||
                (addr >= (unsigned long)__sched_text_start
                && addr < (unsigned long)__sched_text_end);
}

#ifdef CONFIG_CGROUP_SCHED
/*
 * Default task group.
 * Every task in system belongs to this group at bootup.
 */
struct task_group root_task_group;
LIST_HEAD(task_groups);
#endif

DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);

void __init sched_init(void)
{
        int i, j;
        unsigned long alloc_size = 0, ptr;

#ifdef CONFIG_FAIR_GROUP_SCHED
        alloc_size += 2 * nr_cpu_ids * sizeof(void **);
#endif
#ifdef CONFIG_RT_GROUP_SCHED
        alloc_size += 2 * nr_cpu_ids * sizeof(void **);
#endif
#ifdef CONFIG_CPUMASK_OFFSTACK
        alloc_size += num_possible_cpus() * cpumask_size();
#endif
        if (alloc_size) {
                ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT);

#ifdef CONFIG_FAIR_GROUP_SCHED
                root_task_group.se = (struct sched_entity **)ptr;
                ptr += nr_cpu_ids * sizeof(void **);

                root_task_group.cfs_rq = (struct cfs_rq **)ptr;
                ptr += nr_cpu_ids * sizeof(void **);

#endif /* CONFIG_FAIR_GROUP_SCHED */
#ifdef CONFIG_RT_GROUP_SCHED
                root_task_group.rt_se = (struct sched_rt_entity **)ptr;
                ptr += nr_cpu_ids * sizeof(void **);

                root_task_group.rt_rq = (struct rt_rq **)ptr;
                ptr += nr_cpu_ids * sizeof(void **);

#endif /* CONFIG_RT_GROUP_SCHED */
#ifdef CONFIG_CPUMASK_OFFSTACK
                for_each_possible_cpu(i) {
                        per_cpu(load_balance_mask, i) = (void *)ptr;
                        ptr += cpumask_size();
                }
#endif /* CONFIG_CPUMASK_OFFSTACK */
        }

#ifdef CONFIG_SMP
        init_defrootdomain();
#endif

        init_rt_bandwidth(&def_rt_bandwidth,
                        global_rt_period(), global_rt_runtime());

#ifdef CONFIG_RT_GROUP_SCHED
        init_rt_bandwidth(&root_task_group.rt_bandwidth,
                        global_rt_period(), global_rt_runtime());
#endif /* CONFIG_RT_GROUP_SCHED */

#ifdef CONFIG_CGROUP_SCHED
        list_add(&root_task_group.list, &task_groups);
        INIT_LIST_HEAD(&root_task_group.children);
        INIT_LIST_HEAD(&root_task_group.siblings);
        autogroup_init(&init_task);

#endif /* CONFIG_CGROUP_SCHED */

        for_each_possible_cpu(i) {
                struct rq *rq;

                rq = cpu_rq(i);
                raw_spin_lock_init(&rq->lock);
                rq->nr_running = 0;
                rq->calc_load_active = 0;
                rq->calc_load_update = jiffies + LOAD_FREQ;
                init_cfs_rq(&rq->cfs);
                init_rt_rq(&rq->rt, rq);
#ifdef CONFIG_FAIR_GROUP_SCHED
                root_task_group.shares = ROOT_TASK_GROUP_LOAD;
                INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
                /*
                 * How much cpu bandwidth does root_task_group get?
                 *
                 * In case of task-groups formed thr' the cgroup filesystem, it
                 * gets 100% of the cpu resources in the system. This overall
                 * system cpu resource is divided among the tasks of
                 * root_task_group and its child task-groups in a fair manner,
                 * based on each entity's (task or task-group's) weight
                 * (se->load.weight).
                 *
                 * In other words, if root_task_group has 10 tasks of weight
                 * 1024) and two child groups A0 and A1 (of weight 1024 each),
                 * then A0's share of the cpu resource is:
                 *
                 *      A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
                 *
                 * We achieve this by letting root_task_group's tasks sit
                 * directly in rq->cfs (i.e root_task_group->se[] = NULL).
                 */
                init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
                init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
#endif /* CONFIG_FAIR_GROUP_SCHED */

                rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
#ifdef CONFIG_RT_GROUP_SCHED
                INIT_LIST_HEAD(&rq->leaf_rt_rq_list);
                init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
#endif

                for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
                        rq->cpu_load[j] = 0;

                rq->last_load_update_tick = jiffies;

#ifdef CONFIG_SMP
                rq->sd = NULL;
                rq->rd = NULL;
                rq->cpu_power = SCHED_POWER_SCALE;
                rq->post_schedule = 0;
                rq->active_balance = 0;
                rq->next_balance = jiffies;
                rq->push_cpu = 0;
                rq->cpu = i;
                rq->online = 0;
                rq->idle_stamp = 0;
                rq->avg_idle = 2*sysctl_sched_migration_cost;

                INIT_LIST_HEAD(&rq->cfs_tasks);

                rq_attach_root(rq, &def_root_domain);
#ifdef CONFIG_NO_HZ_COMMON
                rq->nohz_flags = 0;
#endif
#ifdef CONFIG_NO_HZ_FULL
                rq->last_sched_tick = 0;
#endif
#endif
                init_rq_hrtick(rq);
                atomic_set(&rq->nr_iowait, 0);
        }

        set_load_weight(&init_task);

#ifdef CONFIG_PREEMPT_NOTIFIERS
        INIT_HLIST_HEAD(&init_task.preempt_notifiers);
#endif

#ifdef CONFIG_RT_MUTEXES
        plist_head_init(&init_task.pi_waiters);
#endif

        /*
         * The boot idle thread does lazy MMU switching as well:
         */
        atomic_inc(&init_mm.mm_count);
        enter_lazy_tlb(&init_mm, current);

        /*
         * Make us the idle thread. Technically, schedule() should not be
         * called from this thread, however somewhere below it might be,
         * but because we are the idle thread, we just pick up running again
         * when this runqueue becomes "idle".
         */
        init_idle(current, smp_processor_id());

        calc_load_update = jiffies + LOAD_FREQ;

        /*
         * During early bootup we pretend to be a normal task:
         */
        current->sched_class = &fair_sched_class;

#ifdef CONFIG_SMP
        zalloc_cpumask_var(&sched_domains_tmpmask, GFP_NOWAIT);
        /* May be allocated at isolcpus cmdline parse time */
        if (cpu_isolated_map == NULL)
                zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT);
        idle_thread_set_boot_cpu();
#endif
        init_sched_fair_class();

        scheduler_running = 1;
}

#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
static inline int preempt_count_equals(int preempt_offset)
{
        int nested = (preempt_count() & ~PREEMPT_ACTIVE) + rcu_preempt_depth();

        return (nested == preempt_offset);
}

void __might_sleep(const char *file, int line, int preempt_offset)
{
        static unsigned long prev_jiffy;        /* ratelimiting */

        rcu_sleep_check(); /* WARN_ON_ONCE() by default, no rate limit reqd. */
        if ((preempt_count_equals(preempt_offset) && !irqs_disabled()) ||
            system_state != SYSTEM_RUNNING || oops_in_progress)
                return;
        if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
                return;
        prev_jiffy = jiffies;

        printk(KERN_ERR
                "BUG: sleeping function called from invalid context at %s:%d\n",
                        file, line);
        printk(KERN_ERR
                "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
                        in_atomic(), irqs_disabled(),
                        current->pid, current->comm);

        debug_show_held_locks(current);
        if (irqs_disabled())
                print_irqtrace_events(current);
        dump_stack();
}
EXPORT_SYMBOL(__might_sleep);
#endif

#ifdef CONFIG_MAGIC_SYSRQ
static void normalize_task(struct rq *rq, struct task_struct *p)
{
        const struct sched_class *prev_class = p->sched_class;
        int old_prio = p->prio;
        int on_rq;

        on_rq = p->on_rq;
        if (on_rq)
                dequeue_task(rq, p, 0);
        __setscheduler(rq, p, SCHED_NORMAL, 0);
        if (on_rq) {
                enqueue_task(rq, p, 0);
                resched_task(rq->curr);
        }

        check_class_changed(rq, p, prev_class, old_prio);
}

void normalize_rt_tasks(void)
{
        struct task_struct *g, *p;
        unsigned long flags;
        struct rq *rq;

        read_lock_irqsave(&tasklist_lock, flags);
        do_each_thread(g, p) {
                /*
                 * Only normalize user tasks:
                 */
                if (!p->mm)
                        continue;

                p->se.exec_start                = 0;
#ifdef CONFIG_SCHEDSTATS
                p->se.statistics.wait_start     = 0;
                p->se.statistics.sleep_start    = 0;
                p->se.statistics.block_start    = 0;
#endif

                if (!rt_task(p)) {
                        /*
                         * Renice negative nice level userspace
                         * tasks back to 0:
                         */
                        if (TASK_NICE(p) < 0 && p->mm)
                                set_user_nice(p, 0);
                        continue;
                }

                raw_spin_lock(&p->pi_lock);
                rq = __task_rq_lock(p);

                normalize_task(rq, p);

                __task_rq_unlock(rq);
                raw_spin_unlock(&p->pi_lock);
        } while_each_thread(g, p);

        read_unlock_irqrestore(&tasklist_lock, flags);
}

#endif /* CONFIG_MAGIC_SYSRQ */

#if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
/*
 * These functions are only useful for the IA64 MCA handling, or kdb.
 *
 * They can only be called when the whole system has been
 * stopped - every CPU needs to be quiescent, and no scheduling
 * activity can take place. Using them for anything else would
 * be a serious bug, and as a result, they aren't even visible
 * under any other configuration.
 */

/**
 * curr_task - return the current task for a given cpu.
 * @cpu: the processor in question.
 *
 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
 */
struct task_struct *curr_task(int cpu)
{
        return cpu_curr(cpu);
}

#endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */

#ifdef CONFIG_IA64
/**
 * set_curr_task - set the current task for a given cpu.
 * @cpu: the processor in question.
 * @p: the task pointer to set.
 *
 * Description: This function must only be used when non-maskable interrupts
 * are serviced on a separate stack. It allows the architecture to switch the
 * notion of the current task on a cpu in a non-blocking manner. This function
 * must be called with all CPU's synchronized, and interrupts disabled, the
 * and caller must save the original value of the current task (see
 * curr_task() above) and restore that value before reenabling interrupts and
 * re-starting the system.
 *
 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
 */
void set_curr_task(int cpu, struct task_struct *p)
{
        cpu_curr(cpu) = p;
}

#endif

#ifdef CONFIG_CGROUP_SCHED
/* task_group_lock serializes the addition/removal of task groups */
static DEFINE_SPINLOCK(task_group_lock);

static void free_sched_group(struct task_group *tg)
{
        free_fair_sched_group(tg);
        free_rt_sched_group(tg);
        autogroup_free(tg);
        kfree(tg);
}

/* allocate runqueue etc for a new task group */
struct task_group *sched_create_group(struct task_group *parent)
{
        struct task_group *tg;

        tg = kzalloc(sizeof(*tg), GFP_KERNEL);
        if (!tg)
                return ERR_PTR(-ENOMEM);

        if (!alloc_fair_sched_group(tg, parent))
                goto err;

        if (!alloc_rt_sched_group(tg, parent))
                goto err;

        return tg;

err:
        free_sched_group(tg);
        return ERR_PTR(-ENOMEM);
}

void sched_online_group(struct task_group *tg, struct task_group *parent)
{
        unsigned long flags;

        spin_lock_irqsave(&task_group_lock, flags);
        list_add_rcu(&tg->list, &task_groups);

        WARN_ON(!parent); /* root should already exist */

        tg->parent = parent;
        INIT_LIST_HEAD(&tg->children);
        list_add_rcu(&tg->siblings, &parent->children);
        spin_unlock_irqrestore(&task_group_lock, flags);
}

/* rcu callback to free various structures associated with a task group */
static void free_sched_group_rcu(struct rcu_head *rhp)
{
        /* now it should be safe to free those cfs_rqs */
        free_sched_group(container_of(rhp, struct task_group, rcu));
}

/* Destroy runqueue etc associated with a task group */
void sched_destroy_group(struct task_group *tg)
{
        /* wait for possible concurrent references to cfs_rqs complete */
        call_rcu(&tg->rcu, free_sched_group_rcu);
}

void sched_offline_group(struct task_group *tg)
{
        unsigned long flags;
        int i;

        /* end participation in shares distribution */
        for_each_possible_cpu(i)
                unregister_fair_sched_group(tg, i);

        spin_lock_irqsave(&task_group_lock, flags);
        list_del_rcu(&tg->list);
        list_del_rcu(&tg->siblings);
        spin_unlock_irqrestore(&task_group_lock, flags);
}

/* change task's runqueue when it moves between groups.
 *      The caller of this function should have put the task in its new group
 *      by now. This function just updates tsk->se.cfs_rq and tsk->se.parent to
 *      reflect its new group.
 */
void sched_move_task(struct task_struct *tsk)
{
        struct task_group *tg;
        int on_rq, running;
        unsigned long flags;
        struct rq *rq;

        rq = task_rq_lock(tsk, &flags);

        running = task_current(rq, tsk);
        on_rq = tsk->on_rq;

        if (on_rq)
                dequeue_task(rq, tsk, 0);
        if (unlikely(running))
                tsk->sched_class->put_prev_task(rq, tsk);

        tg = container_of(task_subsys_state_check(tsk, cpu_cgroup_subsys_id,
                                lockdep_is_held(&tsk->sighand->siglock)),
                          struct task_group, css);
        tg = autogroup_task_group(tsk, tg);
        tsk->sched_task_group = tg;

#ifdef CONFIG_FAIR_GROUP_SCHED
        if (tsk->sched_class->task_move_group)
                tsk->sched_class->task_move_group(tsk, on_rq);
        else
#endif
                set_task_rq(tsk, task_cpu(tsk));

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

        task_rq_unlock(rq, tsk, &flags);
}
#endif /* CONFIG_CGROUP_SCHED */

#if defined(CONFIG_RT_GROUP_SCHED) || defined(CONFIG_CFS_BANDWIDTH)
static unsigned long to_ratio(u64 period, u64 runtime)
{
        if (runtime == RUNTIME_INF)
                return 1ULL << 20;

        return div64_u64(runtime << 20, period);
}
#endif

#ifdef CONFIG_RT_GROUP_SCHED
/*
 * Ensure that the real time constraints are schedulable.
 */
static DEFINE_MUTEX(rt_constraints_mutex);

/* Must be called with tasklist_lock held */
static inline int tg_has_rt_tasks(struct task_group *tg)
{
        struct task_struct *g, *p;

        do_each_thread(g, p) {
                if (rt_task(p) && task_rq(p)->rt.tg == tg)
                        return 1;
        } while_each_thread(g, p);

        return 0;
}

struct rt_schedulable_data {
        struct task_group *tg;
        u64 rt_period;
        u64 rt_runtime;
};

static int tg_rt_schedulable(struct task_group *tg, void *data)
{
        struct rt_schedulable_data *d = data;
        struct task_group *child;
        unsigned long total, sum = 0;
        u64 period, runtime;

        period = ktime_to_ns(tg->rt_bandwidth.rt_period);
        runtime = tg->rt_bandwidth.rt_runtime;

        if (tg == d->tg) {
                period = d->rt_period;
                runtime = d->rt_runtime;
        }

        /*
         * Cannot have more runtime than the period.
         */
        if (runtime > period && runtime != RUNTIME_INF)
                return -EINVAL;

        /*
         * Ensure we don't starve existing RT tasks.
         */
        if (rt_bandwidth_enabled() && !runtime && tg_has_rt_tasks(tg))
                return -EBUSY;

        total = to_ratio(period, runtime);

        /*
         * Nobody can have more than the global setting allows.
         */
        if (total > to_ratio(global_rt_period(), global_rt_runtime()))
                return -EINVAL;

        /*
         * The sum of our children's runtime should not exceed our own.
         */
        list_for_each_entry_rcu(child, &tg->children, siblings) {
                period = ktime_to_ns(child->rt_bandwidth.rt_period);
                runtime = child->rt_bandwidth.rt_runtime;

                if (child == d->tg) {
                        period = d->rt_period;
                        runtime = d->rt_runtime;
                }

                sum += to_ratio(period, runtime);
        }

        if (sum > total)
                return -EINVAL;

        return 0;
}

static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
{
        int ret;

        struct rt_schedulable_data data = {
                .tg = tg,
                .rt_period = period,
                .rt_runtime = runtime,
        };

        rcu_read_lock();
        ret = walk_tg_tree(tg_rt_schedulable, tg_nop, &data);
        rcu_read_unlock();

        return ret;
}

static int tg_set_rt_bandwidth(struct task_group *tg,
                u64 rt_period, u64 rt_runtime)
{
        int i, err = 0;

        mutex_lock(&rt_constraints_mutex);
        read_lock(&tasklist_lock);
        err = __rt_schedulable(tg, rt_period, rt_runtime);
        if (err)
                goto unlock;

        raw_spin_lock_irq(&tg->rt_bandwidth.rt_runtime_lock);
        tg->rt_bandwidth.rt_period = ns_to_ktime(rt_period);
        tg->rt_bandwidth.rt_runtime = rt_runtime;

        for_each_possible_cpu(i) {
                struct rt_rq *rt_rq = tg->rt_rq[i];

                raw_spin_lock(&rt_rq->rt_runtime_lock);
                rt_rq->rt_runtime = rt_runtime;
                raw_spin_unlock(&rt_rq->rt_runtime_lock);
        }
        raw_spin_unlock_irq(&tg->rt_bandwidth.rt_runtime_lock);
unlock:
        read_unlock(&tasklist_lock);
        mutex_unlock(&rt_constraints_mutex);

        return err;
}

static int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)
{
        u64 rt_runtime, rt_period;

        rt_period = ktime_to_ns(tg->rt_bandwidth.rt_period);
        rt_runtime = (u64)rt_runtime_us * NSEC_PER_USEC;
        if (rt_runtime_us < 0)
                rt_runtime = RUNTIME_INF;

        return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
}

static long sched_group_rt_runtime(struct task_group *tg)
{
        u64 rt_runtime_us;

        if (tg->rt_bandwidth.rt_runtime == RUNTIME_INF)
                return -1;

        rt_runtime_us = tg->rt_bandwidth.rt_runtime;
        do_div(rt_runtime_us, NSEC_PER_USEC);
        return rt_runtime_us;
}

static int sched_group_set_rt_period(struct task_group *tg, long rt_period_us)
{
        u64 rt_runtime, rt_period;

        rt_period = (u64)rt_period_us * NSEC_PER_USEC;
        rt_runtime = tg->rt_bandwidth.rt_runtime;

        if (rt_period == 0)
                return -EINVAL;

        return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
}

static long sched_group_rt_period(struct task_group *tg)
{
        u64 rt_period_us;

        rt_period_us = ktime_to_ns(tg->rt_bandwidth.rt_period);
        do_div(rt_period_us, NSEC_PER_USEC);
        return rt_period_us;
}

static int sched_rt_global_constraints(void)
{
        u64 runtime, period;
        int ret = 0;

        if (sysctl_sched_rt_period <= 0)
                return -EINVAL;

        runtime = global_rt_runtime();
        period = global_rt_period();

        /*
         * Sanity check on the sysctl variables.
         */
        if (runtime > period && runtime != RUNTIME_INF)
                return -EINVAL;

        mutex_lock(&rt_constraints_mutex);
        read_lock(&tasklist_lock);
        ret = __rt_schedulable(NULL, 0, 0);
        read_unlock(&tasklist_lock);
        mutex_unlock(&rt_constraints_mutex);

        return ret;
}

static int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
{
        /* Don't accept realtime tasks when there is no way for them to run */
        if (rt_task(tsk) && tg->rt_bandwidth.rt_runtime == 0)
                return 0;

        return 1;
}

#else /* !CONFIG_RT_GROUP_SCHED */
static int sched_rt_global_constraints(void)
{
        unsigned long flags;
        int i;

        if (sysctl_sched_rt_period <= 0)
                return -EINVAL;

        /*
         * There's always some RT tasks in the root group
         * -- migration, kstopmachine etc..
         */
        if (sysctl_sched_rt_runtime == 0)
                return -EBUSY;

        raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
        for_each_possible_cpu(i) {
                struct rt_rq *rt_rq = &cpu_rq(i)->rt;

                raw_spin_lock(&rt_rq->rt_runtime_lock);
                rt_rq->rt_runtime = global_rt_runtime();
                raw_spin_unlock(&rt_rq->rt_runtime_lock);
        }
        raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);

        return 0;
}
#endif /* CONFIG_RT_GROUP_SCHED */

int sched_rr_handler(struct ctl_table *table, int write,
                void __user *buffer, size_t *lenp,
                loff_t *ppos)
{
        int ret;
        static DEFINE_MUTEX(mutex);

        mutex_lock(&mutex);
        ret = proc_dointvec(table, write, buffer, lenp, ppos);
        /* make sure that internally we keep jiffies */
        /* also, writing zero resets timeslice to default */
        if (!ret && write) {
                sched_rr_timeslice = sched_rr_timeslice <= 0 ?
                        RR_TIMESLICE : msecs_to_jiffies(sched_rr_timeslice);
        }
        mutex_unlock(&mutex);
        return ret;
}

int sched_rt_handler(struct ctl_table *table, int write,
                void __user *buffer, size_t *lenp,
                loff_t *ppos)
{
        int ret;
        int old_period, old_runtime;
        static DEFINE_MUTEX(mutex);

        mutex_lock(&mutex);
        old_period = sysctl_sched_rt_period;
        old_runtime = sysctl_sched_rt_runtime;

        ret = proc_dointvec(table, write, buffer, lenp, ppos);

        if (!ret && write) {
                ret = sched_rt_global_constraints();
                if (ret) {
                        sysctl_sched_rt_period = old_period;
                        sysctl_sched_rt_runtime = old_runtime;
                } else {
                        def_rt_bandwidth.rt_runtime = global_rt_runtime();
                        def_rt_bandwidth.rt_period =
                                ns_to_ktime(global_rt_period());
                }
        }
        mutex_unlock(&mutex);

        return ret;
}

#ifdef CONFIG_CGROUP_SCHED

/* return corresponding task_group object of a cgroup */
static inline struct task_group *cgroup_tg(struct cgroup *cgrp)
{
        return container_of(cgroup_subsys_state(cgrp, cpu_cgroup_subsys_id),
                            struct task_group, css);
}

static struct cgroup_subsys_state *cpu_cgroup_css_alloc(struct cgroup *cgrp)
{
        struct task_group *tg, *parent;

        if (!cgrp->parent) {
                /* This is early initialization for the top cgroup */
                return &root_task_group.css;
        }

        parent = cgroup_tg(cgrp->parent);
        tg = sched_create_group(parent);
        if (IS_ERR(tg))
                return ERR_PTR(-ENOMEM);

        return &tg->css;
}

static int cpu_cgroup_css_online(struct cgroup *cgrp)
{
        struct task_group *tg = cgroup_tg(cgrp);
        struct task_group *parent;

        if (!cgrp->parent)
                return 0;

        parent = cgroup_tg(cgrp->parent);
        sched_online_group(tg, parent);
        return 0;
}

static void cpu_cgroup_css_free(struct cgroup *cgrp)
{
        struct task_group *tg = cgroup_tg(cgrp);

        sched_destroy_group(tg);
}

static void cpu_cgroup_css_offline(struct cgroup *cgrp)
{
        struct task_group *tg = cgroup_tg(cgrp);

        sched_offline_group(tg);
}

static int cpu_cgroup_can_attach(struct cgroup *cgrp,
                                 struct cgroup_taskset *tset)
{
        struct task_struct *task;

        cgroup_taskset_for_each(task, cgrp, tset) {
#ifdef CONFIG_RT_GROUP_SCHED
                if (!sched_rt_can_attach(cgroup_tg(cgrp), task))
                        return -EINVAL;
#else
                /* We don't support RT-tasks being in separate groups */
                if (task->sched_class != &fair_sched_class)
                        return -EINVAL;
#endif
        }
        return 0;
}

static void cpu_cgroup_attach(struct cgroup *cgrp,
                              struct cgroup_taskset *tset)
{
        struct task_struct *task;

        cgroup_taskset_for_each(task, cgrp, tset)
                sched_move_task(task);
}

static void
cpu_cgroup_exit(struct cgroup *cgrp, struct cgroup *old_cgrp,
                struct task_struct *task)
{
        /*
         * cgroup_exit() is called in the copy_process() failure path.
         * Ignore this case since the task hasn't ran yet, this avoids
         * trying to poke a half freed task state from generic code.
         */
        if (!(task->flags & PF_EXITING))
                return;

        sched_move_task(task);
}

#ifdef CONFIG_FAIR_GROUP_SCHED
static int cpu_shares_write_u64(struct cgroup *cgrp, struct cftype *cftype,
                                u64 shareval)
{
        return sched_group_set_shares(cgroup_tg(cgrp), scale_load(shareval));
}

static u64 cpu_shares_read_u64(struct cgroup *cgrp, struct cftype *cft)
{
        struct task_group *tg = cgroup_tg(cgrp);

        return (u64) scale_load_down(tg->shares);
}

#ifdef CONFIG_CFS_BANDWIDTH
static DEFINE_MUTEX(cfs_constraints_mutex);

const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */

static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);

static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
{
        int i, ret = 0, runtime_enabled, runtime_was_enabled;
        struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;

        if (tg == &root_task_group)
                return -EINVAL;

        /*
         * Ensure we have at some amount of bandwidth every period.  This is
         * to prevent reaching a state of large arrears when throttled via
         * entity_tick() resulting in prolonged exit starvation.
         */
        if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
                return -EINVAL;

        /*
         * Likewise, bound things on the otherside by preventing insane quota
         * periods.  This also allows us to normalize in computing quota
         * feasibility.
         */
        if (period > max_cfs_quota_period)
                return -EINVAL;

        mutex_lock(&cfs_constraints_mutex);
        ret = __cfs_schedulable(tg, period, quota);
        if (ret)
                goto out_unlock;

        runtime_enabled = quota != RUNTIME_INF;
        runtime_was_enabled = cfs_b->quota != RUNTIME_INF;
        account_cfs_bandwidth_used(runtime_enabled, runtime_was_enabled);
        raw_spin_lock_irq(&cfs_b->lock);
        cfs_b->period = ns_to_ktime(period);
        cfs_b->quota = quota;

        __refill_cfs_bandwidth_runtime(cfs_b);
        /* restart the period timer (if active) to handle new period expiry */
        if (runtime_enabled && cfs_b->timer_active) {
                /* force a reprogram */
                cfs_b->timer_active = 0;
                __start_cfs_bandwidth(cfs_b);
        }
        raw_spin_unlock_irq(&cfs_b->lock);

        for_each_possible_cpu(i) {
                struct cfs_rq *cfs_rq = tg->cfs_rq[i];
                struct rq *rq = cfs_rq->rq;

                raw_spin_lock_irq(&rq->lock);
                cfs_rq->runtime_enabled = runtime_enabled;
                cfs_rq->runtime_remaining = 0;

                if (cfs_rq->throttled)
                        unthrottle_cfs_rq(cfs_rq);
                raw_spin_unlock_irq(&rq->lock);
        }
out_unlock:
        mutex_unlock(&cfs_constraints_mutex);

        return ret;
}

int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
{
        u64 quota, period;

        period = ktime_to_ns(tg->cfs_bandwidth.period);
        if (cfs_quota_us < 0)
                quota = RUNTIME_INF;
        else
                quota = (u64)cfs_quota_us * NSEC_PER_USEC;

        return tg_set_cfs_bandwidth(tg, period, quota);
}

long tg_get_cfs_quota(struct task_group *tg)
{
        u64 quota_us;

        if (tg->cfs_bandwidth.quota == RUNTIME_INF)
                return -1;

        quota_us = tg->cfs_bandwidth.quota;
        do_div(quota_us, NSEC_PER_USEC);

        return quota_us;
}

int tg_set_cfs_period(struct task_group *tg, long cfs_period_us)
{
        u64 quota, period;

        period = (u64)cfs_period_us * NSEC_PER_USEC;
        quota = tg->cfs_bandwidth.quota;

        return tg_set_cfs_bandwidth(tg, period, quota);
}

long tg_get_cfs_period(struct task_group *tg)
{
        u64 cfs_period_us;

        cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period);
        do_div(cfs_period_us, NSEC_PER_USEC);

        return cfs_period_us;
}

static s64 cpu_cfs_quota_read_s64(struct cgroup *cgrp, struct cftype *cft)
{
        return tg_get_cfs_quota(cgroup_tg(cgrp));
}

static int cpu_cfs_quota_write_s64(struct cgroup *cgrp, struct cftype *cftype,
                                s64 cfs_quota_us)
{
        return tg_set_cfs_quota(cgroup_tg(cgrp), cfs_quota_us);
}

static u64 cpu_cfs_period_read_u64(struct cgroup *cgrp, struct cftype *cft)
{
        return tg_get_cfs_period(cgroup_tg(cgrp));
}

static int cpu_cfs_period_write_u64(struct cgroup *cgrp, struct cftype *cftype,
                                u64 cfs_period_us)
{
        return tg_set_cfs_period(cgroup_tg(cgrp), cfs_period_us);
}

struct cfs_schedulable_data {
        struct task_group *tg;
        u64 period, quota;
};

/*
 * normalize group quota/period to be quota/max_period
 * note: units are usecs
 */
static u64 normalize_cfs_quota(struct task_group *tg,
                               struct cfs_schedulable_data *d)
{
        u64 quota, period;

        if (tg == d->tg) {
                period = d->period;
                quota = d->quota;
        } else {
                period = tg_get_cfs_period(tg);
                quota = tg_get_cfs_quota(tg);
        }

        /* note: these should typically be equivalent */
        if (quota == RUNTIME_INF || quota == -1)
                return RUNTIME_INF;

        return to_ratio(period, quota);
}

static int tg_cfs_schedulable_down(struct task_group *tg, void *data)
{
        struct cfs_schedulable_data *d = data;
        struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
        s64 quota = 0, parent_quota = -1;

        if (!tg->parent) {
                quota = RUNTIME_INF;
        } else {
                struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth;

                quota = normalize_cfs_quota(tg, d);
                parent_quota = parent_b->hierarchal_quota;

                /*
                 * ensure max(child_quota) <= parent_quota, inherit when no
                 * limit is set
                 */
                if (quota == RUNTIME_INF)
                        quota = parent_quota;
                else if (parent_quota != RUNTIME_INF && quota > parent_quota)
                        return -EINVAL;
        }
        cfs_b->hierarchal_quota = quota;

        return 0;
}

static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
{
        int ret;
        struct cfs_schedulable_data data = {
                .tg = tg,
                .period = period,
                .quota = quota,
        };

        if (quota != RUNTIME_INF) {
                do_div(data.period, NSEC_PER_USEC);
                do_div(data.quota, NSEC_PER_USEC);
        }

        rcu_read_lock();
        ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
        rcu_read_unlock();

        return ret;
}

static int cpu_stats_show(struct cgroup *cgrp, struct cftype *cft,
                struct cgroup_map_cb *cb)
{
        struct task_group *tg = cgroup_tg(cgrp);
        struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;

        cb->fill(cb, "nr_periods", cfs_b->nr_periods);
        cb->fill(cb, "nr_throttled", cfs_b->nr_throttled);
        cb->fill(cb, "throttled_time", cfs_b->throttled_time);

        return 0;
}
#endif /* CONFIG_CFS_BANDWIDTH */
#endif /* CONFIG_FAIR_GROUP_SCHED */

#ifdef CONFIG_RT_GROUP_SCHED
static int cpu_rt_runtime_write(struct cgroup *cgrp, struct cftype *cft,
                                s64 val)
{
        return sched_group_set_rt_runtime(cgroup_tg(cgrp), val);
}

static s64 cpu_rt_runtime_read(struct cgroup *cgrp, struct cftype *cft)
{
        return sched_group_rt_runtime(cgroup_tg(cgrp));
}

static int cpu_rt_period_write_uint(struct cgroup *cgrp, struct cftype *cftype,
                u64 rt_period_us)
{
        return sched_group_set_rt_period(cgroup_tg(cgrp), rt_period_us);
}

static u64 cpu_rt_period_read_uint(struct cgroup *cgrp, struct cftype *cft)
{
        return sched_group_rt_period(cgroup_tg(cgrp));
}
#endif /* CONFIG_RT_GROUP_SCHED */

static struct cftype cpu_files[] = {
#ifdef CONFIG_FAIR_GROUP_SCHED
        {
                .name = "shares",
                .read_u64 = cpu_shares_read_u64,
                .write_u64 = cpu_shares_write_u64,
        },
#endif
#ifdef CONFIG_CFS_BANDWIDTH
        {
                .name = "cfs_quota_us",
                .read_s64 = cpu_cfs_quota_read_s64,
                .write_s64 = cpu_cfs_quota_write_s64,
        },
        {
                .name = "cfs_period_us",
                .read_u64 = cpu_cfs_period_read_u64,
                .write_u64 = cpu_cfs_period_write_u64,
        },
        {
                .name = "stat",
                .read_map = cpu_stats_show,
        },
#endif
#ifdef CONFIG_RT_GROUP_SCHED
        {
                .name = "rt_runtime_us",
                .read_s64 = cpu_rt_runtime_read,
                .write_s64 = cpu_rt_runtime_write,
        },
        {
                .name = "rt_period_us",
                .read_u64 = cpu_rt_period_read_uint,
                .write_u64 = cpu_rt_period_write_uint,
        },
#endif
        { }     /* terminate */
};

struct cgroup_subsys cpu_cgroup_subsys = {
        .name           = "cpu",
        .css_alloc      = cpu_cgroup_css_alloc,
        .css_free       = cpu_cgroup_css_free,
        .css_online     = cpu_cgroup_css_online,
        .css_offline    = cpu_cgroup_css_offline,
        .can_attach     = cpu_cgroup_can_attach,
        .attach         = cpu_cgroup_attach,
        .exit           = cpu_cgroup_exit,
        .subsys_id      = cpu_cgroup_subsys_id,
        .base_cftypes   = cpu_files,
        .early_init     = 1,
};

#endif  /* CONFIG_CGROUP_SCHED */

void dump_cpu_task(int cpu)
{
        pr_info("Task dump for CPU %d:\n", cpu);
        sched_show_task(cpu_curr(cpu));
}