kernel.org linux-2.6.10

[linux-2.6.git] / kernel / sched.c

/*
 *  kernel/sched.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
 */

#include <linux/mm.h>
#include <linux/module.h>
#include <linux/nmi.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <linux/highmem.h>
#include <linux/smp_lock.h>
#include <asm/mmu_context.h>
#include <linux/interrupt.h>
#include <linux/completion.h>
#include <linux/kernel_stat.h>
#include <linux/security.h>
#include <linux/notifier.h>
#include <linux/profile.h>
#include <linux/suspend.h>
#include <linux/blkdev.h>
#include <linux/delay.h>
#include <linux/smp.h>
#include <linux/timer.h>
#include <linux/rcupdate.h>
#include <linux/cpu.h>
#include <linux/percpu.h>
#include <linux/kthread.h>
#include <linux/seq_file.h>
#include <linux/syscalls.h>
#include <linux/times.h>
#include <asm/tlb.h>

#include <asm/unistd.h>

#ifdef CONFIG_NUMA
#define cpu_to_node_mask(cpu) node_to_cpumask(cpu_to_node(cpu))
#else
#define cpu_to_node_mask(cpu) (cpu_online_map)
#endif

/*
 * Convert user-nice values [ -20 ... 0 ... 19 ]
 * to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],
 * and back.
 */
#define NICE_TO_PRIO(nice)      (MAX_RT_PRIO + (nice) + 20)
#define PRIO_TO_NICE(prio)      ((prio) - MAX_RT_PRIO - 20)
#define TASK_NICE(p)            PRIO_TO_NICE((p)->static_prio)

/*
 * 'User priority' is the nice value converted to something we
 * can work with better when scaling various scheduler parameters,
 * it's a [ 0 ... 39 ] range.
 */
#define USER_PRIO(p)            ((p)-MAX_RT_PRIO)
#define TASK_USER_PRIO(p)       USER_PRIO((p)->static_prio)
#define MAX_USER_PRIO           (USER_PRIO(MAX_PRIO))

/*
 * Some helpers for converting nanosecond timing to jiffy resolution
 */
#define NS_TO_JIFFIES(TIME)     ((TIME) / (1000000000 / HZ))
#define JIFFIES_TO_NS(TIME)     ((TIME) * (1000000000 / HZ))

/*
 * These are the 'tuning knobs' of the scheduler:
 *
 * Minimum timeslice is 5 msecs (or 1 jiffy, whichever is larger),
 * default timeslice is 100 msecs, maximum timeslice is 800 msecs.
 * Timeslices get refilled after they expire.
 */
#define MIN_TIMESLICE           max(5 * HZ / 1000, 1)
#define DEF_TIMESLICE           (100 * HZ / 1000)
#define ON_RUNQUEUE_WEIGHT       30
#define CHILD_PENALTY            95
#define PARENT_PENALTY          100
#define EXIT_WEIGHT               3
#define PRIO_BONUS_RATIO         25
#define MAX_BONUS               (MAX_USER_PRIO * PRIO_BONUS_RATIO / 100)
#define INTERACTIVE_DELTA         2
#define MAX_SLEEP_AVG           (DEF_TIMESLICE * MAX_BONUS)
#define STARVATION_LIMIT        (MAX_SLEEP_AVG)
#define NS_MAX_SLEEP_AVG        (JIFFIES_TO_NS(MAX_SLEEP_AVG))
#define CREDIT_LIMIT            100

/*
 * If a task is 'interactive' then we reinsert it in the active
 * array after it has expired its current timeslice. (it will not
 * continue to run immediately, it will still roundrobin with
 * other interactive tasks.)
 *
 * This part scales the interactivity limit depending on niceness.
 *
 * We scale it linearly, offset by the INTERACTIVE_DELTA delta.
 * Here are a few examples of different nice levels:
 *
 *  TASK_INTERACTIVE(-20): [1,1,1,1,1,1,1,1,1,0,0]
 *  TASK_INTERACTIVE(-10): [1,1,1,1,1,1,1,0,0,0,0]
 *  TASK_INTERACTIVE(  0): [1,1,1,1,0,0,0,0,0,0,0]
 *  TASK_INTERACTIVE( 10): [1,1,0,0,0,0,0,0,0,0,0]
 *  TASK_INTERACTIVE( 19): [0,0,0,0,0,0,0,0,0,0,0]
 *
 * (the X axis represents the possible -5 ... 0 ... +5 dynamic
 *  priority range a task can explore, a value of '1' means the
 *  task is rated interactive.)
 *
 * Ie. nice +19 tasks can never get 'interactive' enough to be
 * reinserted into the active array. And only heavily CPU-hog nice -20
 * tasks will be expired. Default nice 0 tasks are somewhere between,
 * it takes some effort for them to get interactive, but it's not
 * too hard.
 */

#define CURRENT_BONUS(p) \
        (NS_TO_JIFFIES((p)->sleep_avg) * MAX_BONUS / \
                MAX_SLEEP_AVG)

#ifdef CONFIG_SMP
#define TIMESLICE_GRANULARITY(p)        (MIN_TIMESLICE * \
                (1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)) * \
                        num_online_cpus())
#else
#define TIMESLICE_GRANULARITY(p)        (MIN_TIMESLICE * \
                (1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)))
#endif

#define SCALE(v1,v1_max,v2_max) \
        (v1) * (v2_max) / (v1_max)

#define DELTA(p) \
        (SCALE(TASK_NICE(p), 40, MAX_BONUS) + INTERACTIVE_DELTA)

#define TASK_INTERACTIVE(p) \
        ((p)->prio <= (p)->static_prio - DELTA(p))

#define INTERACTIVE_SLEEP(p) \
        (JIFFIES_TO_NS(MAX_SLEEP_AVG * \
                (MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1))

#define HIGH_CREDIT(p) \
        ((p)->interactive_credit > CREDIT_LIMIT)

#define LOW_CREDIT(p) \
        ((p)->interactive_credit < -CREDIT_LIMIT)

#define TASK_PREEMPTS_CURR(p, rq) \
        ((p)->prio < (rq)->curr->prio)

/*
 * task_timeslice() scales user-nice values [ -20 ... 0 ... 19 ]
 * to time slice values: [800ms ... 100ms ... 5ms]
 *
 * The higher a thread's priority, the bigger timeslices
 * it gets during one round of execution. But even the lowest
 * priority thread gets MIN_TIMESLICE worth of execution time.
 */

#define SCALE_PRIO(x, prio) \
        max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO/2), MIN_TIMESLICE)

static unsigned int task_timeslice(task_t *p)
{
        if (p->static_prio < NICE_TO_PRIO(0))
                return SCALE_PRIO(DEF_TIMESLICE*4, p->static_prio);
        else
                return SCALE_PRIO(DEF_TIMESLICE, p->static_prio);
}
#define task_hot(p, now, sd) ((long long) ((now) - (p)->last_ran)       \
                                < (long long) (sd)->cache_hot_time)

/*
 * These are the runqueue data structures:
 */

#define BITMAP_SIZE ((((MAX_PRIO+1+7)/8)+sizeof(long)-1)/sizeof(long))

typedef struct runqueue runqueue_t;

struct prio_array {
        unsigned int nr_active;
        unsigned long bitmap[BITMAP_SIZE];
        struct list_head queue[MAX_PRIO];
};

/*
 * This is the main, per-CPU runqueue data structure.
 *
 * Locking rule: those places that want to lock multiple runqueues
 * (such as the load balancing or the thread migration code), lock
 * acquire operations must be ordered by ascending &runqueue.
 */
struct runqueue {
        spinlock_t lock;

        /*
         * nr_running and cpu_load should be in the same cacheline because
         * remote CPUs use both these fields when doing load calculation.
         */
        unsigned long nr_running;
#ifdef CONFIG_SMP
        unsigned long cpu_load;
#endif
        unsigned long long nr_switches;

        /*
         * This is part of a global counter where only the total sum
         * over all CPUs matters. A task can increase this counter on
         * one CPU and if it got migrated afterwards it may decrease
         * it on another CPU. Always updated under the runqueue lock:
         */
        unsigned long nr_uninterruptible;

        unsigned long expired_timestamp;
        unsigned long long timestamp_last_tick;
        task_t *curr, *idle;
        struct mm_struct *prev_mm;
        prio_array_t *active, *expired, arrays[2];
        int best_expired_prio;
        atomic_t nr_iowait;

#ifdef CONFIG_SMP
        struct sched_domain *sd;

        /* For active balancing */
        int active_balance;
        int push_cpu;

        task_t *migration_thread;
        struct list_head migration_queue;
#endif

#ifdef CONFIG_SCHEDSTATS
        /* latency stats */
        struct sched_info rq_sched_info;

        /* sys_sched_yield() stats */
        unsigned long yld_exp_empty;
        unsigned long yld_act_empty;
        unsigned long yld_both_empty;
        unsigned long yld_cnt;

        /* schedule() stats */
        unsigned long sched_noswitch;
        unsigned long sched_switch;
        unsigned long sched_cnt;
        unsigned long sched_goidle;

        /* pull_task() stats */
        unsigned long pt_gained[MAX_IDLE_TYPES];
        unsigned long pt_lost[MAX_IDLE_TYPES];

        /* active_load_balance() stats */
        unsigned long alb_cnt;
        unsigned long alb_lost;
        unsigned long alb_gained;
        unsigned long alb_failed;

        /* try_to_wake_up() stats */
        unsigned long ttwu_cnt;
        unsigned long ttwu_attempts;
        unsigned long ttwu_moved;

        /* wake_up_new_task() stats */
        unsigned long wunt_cnt;
        unsigned long wunt_moved;

        /* sched_migrate_task() stats */
        unsigned long smt_cnt;

        /* sched_balance_exec() stats */
        unsigned long sbe_cnt;
#endif
};

static DEFINE_PER_CPU(struct runqueue, runqueues);

#define for_each_domain(cpu, domain) \
        for (domain = cpu_rq(cpu)->sd; domain; domain = domain->parent)

#define cpu_rq(cpu)             (&per_cpu(runqueues, (cpu)))
#define this_rq()               (&__get_cpu_var(runqueues))
#define task_rq(p)              cpu_rq(task_cpu(p))
#define cpu_curr(cpu)           (cpu_rq(cpu)->curr)

/*
 * Default context-switch locking:
 */
#ifndef prepare_arch_switch
# define prepare_arch_switch(rq, next)  do { } while (0)
# define finish_arch_switch(rq, next)   spin_unlock_irq(&(rq)->lock)
# define task_running(rq, p)            ((rq)->curr == (p))
#endif

/*
 * task_rq_lock - lock the runqueue a given task resides on and disable
 * interrupts.  Note the ordering: we can safely lookup the task_rq without
 * explicitly disabling preemption.
 */
static runqueue_t *task_rq_lock(task_t *p, unsigned long *flags)
        __acquires(rq->lock)
{
        struct runqueue *rq;

repeat_lock_task:
        local_irq_save(*flags);
        rq = task_rq(p);
        spin_lock(&rq->lock);
        if (unlikely(rq != task_rq(p))) {
                spin_unlock_irqrestore(&rq->lock, *flags);
                goto repeat_lock_task;
        }
        return rq;
}

static inline void task_rq_unlock(runqueue_t *rq, unsigned long *flags)
        __releases(rq->lock)
{
        spin_unlock_irqrestore(&rq->lock, *flags);
}

#ifdef CONFIG_SCHEDSTATS
/*
 * bump this up when changing the output format or the meaning of an existing
 * format, so that tools can adapt (or abort)
 */
#define SCHEDSTAT_VERSION 10

static int show_schedstat(struct seq_file *seq, void *v)
{
        int cpu;
        enum idle_type itype;

        seq_printf(seq, "version %d\n", SCHEDSTAT_VERSION);
        seq_printf(seq, "timestamp %lu\n", jiffies);
        for_each_online_cpu(cpu) {
                runqueue_t *rq = cpu_rq(cpu);
#ifdef CONFIG_SMP
                struct sched_domain *sd;
                int dcnt = 0;
#endif

                /* runqueue-specific stats */
                seq_printf(seq,
                    "cpu%d %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu "
                    "%lu %lu %lu %lu %lu %lu %lu %lu %lu %lu",
                    cpu, rq->yld_both_empty,
                    rq->yld_act_empty, rq->yld_exp_empty,
                    rq->yld_cnt, rq->sched_noswitch,
                    rq->sched_switch, rq->sched_cnt, rq->sched_goidle,
                    rq->alb_cnt, rq->alb_gained, rq->alb_lost,
                    rq->alb_failed,
                    rq->ttwu_cnt, rq->ttwu_moved, rq->ttwu_attempts,
                    rq->wunt_cnt, rq->wunt_moved,
                    rq->smt_cnt, rq->sbe_cnt, rq->rq_sched_info.cpu_time,
                    rq->rq_sched_info.run_delay, rq->rq_sched_info.pcnt);

                for (itype = SCHED_IDLE; itype < MAX_IDLE_TYPES; itype++)
                        seq_printf(seq, " %lu %lu", rq->pt_gained[itype],
                                                    rq->pt_lost[itype]);
                seq_printf(seq, "\n");

#ifdef CONFIG_SMP
                /* domain-specific stats */
                for_each_domain(cpu, sd) {
                        char mask_str[NR_CPUS];

                        cpumask_scnprintf(mask_str, NR_CPUS, sd->span);
                        seq_printf(seq, "domain%d %s", dcnt++, mask_str);
                        for (itype = SCHED_IDLE; itype < MAX_IDLE_TYPES;
                                                itype++) {
                                seq_printf(seq, " %lu %lu %lu %lu %lu",
                                    sd->lb_cnt[itype],
                                    sd->lb_failed[itype],
                                    sd->lb_imbalance[itype],
                                    sd->lb_nobusyq[itype],
                                    sd->lb_nobusyg[itype]);
                        }
                        seq_printf(seq, " %lu %lu %lu %lu\n",
                            sd->sbe_pushed, sd->sbe_attempts,
                            sd->ttwu_wake_affine, sd->ttwu_wake_balance);
                }
#endif
        }
        return 0;
}

static int schedstat_open(struct inode *inode, struct file *file)
{
        unsigned int size = PAGE_SIZE * (1 + num_online_cpus() / 32);
        char *buf = kmalloc(size, GFP_KERNEL);
        struct seq_file *m;
        int res;

        if (!buf)
                return -ENOMEM;
        res = single_open(file, show_schedstat, NULL);
        if (!res) {
                m = file->private_data;
                m->buf = buf;
                m->size = size;
        } else
                kfree(buf);
        return res;
}

struct file_operations proc_schedstat_operations = {
        .open    = schedstat_open,
        .read    = seq_read,
        .llseek  = seq_lseek,
        .release = single_release,
};

# define schedstat_inc(rq, field)       rq->field++;
# define schedstat_add(rq, field, amt)  rq->field += amt;
#else /* !CONFIG_SCHEDSTATS */
# define schedstat_inc(rq, field)       do { } while (0);
# define schedstat_add(rq, field, amt)  do { } while (0);
#endif

/*
 * rq_lock - lock a given runqueue and disable interrupts.
 */
static runqueue_t *this_rq_lock(void)
        __acquires(rq->lock)
{
        runqueue_t *rq;

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

        return rq;
}

static inline void rq_unlock(runqueue_t *rq)
        __releases(rq->lock)
{
        spin_unlock_irq(&rq->lock);
}

#ifdef CONFIG_SCHEDSTATS
/*
 * Called when a process is dequeued from the active array and given
 * the cpu.  We should note that with the exception of interactive
 * tasks, the expired queue will become the active queue after the active
 * queue is empty, without explicitly dequeuing and requeuing tasks in the
 * expired queue.  (Interactive tasks may be requeued directly to the
 * active queue, thus delaying tasks in the expired queue from running;
 * see scheduler_tick()).
 *
 * This function is only called from sched_info_arrive(), rather than
 * dequeue_task(). Even though a task may be queued and dequeued multiple
 * times as it is shuffled about, we're really interested in knowing how
 * long it was from the *first* time it was queued to the time that it
 * finally hit a cpu.
 */
static inline void sched_info_dequeued(task_t *t)
{
        t->sched_info.last_queued = 0;
}

/*
 * Called when a task finally hits the cpu.  We can now calculate how
 * long it was waiting to run.  We also note when it began so that we
 * can keep stats on how long its timeslice is.
 */
static inline void sched_info_arrive(task_t *t)
{
        unsigned long now = jiffies, diff = 0;
        struct runqueue *rq = task_rq(t);

        if (t->sched_info.last_queued)
                diff = now - t->sched_info.last_queued;
        sched_info_dequeued(t);
        t->sched_info.run_delay += diff;
        t->sched_info.last_arrival = now;
        t->sched_info.pcnt++;

        if (!rq)
                return;

        rq->rq_sched_info.run_delay += diff;
        rq->rq_sched_info.pcnt++;
}

/*
 * Called when a process is queued into either the active or expired
 * array.  The time is noted and later used to determine how long we
 * had to wait for us to reach the cpu.  Since the expired queue will
 * become the active queue after active queue is empty, without dequeuing
 * and requeuing any tasks, we are interested in queuing to either. It
 * is unusual but not impossible for tasks to be dequeued and immediately
 * requeued in the same or another array: this can happen in sched_yield(),
 * set_user_nice(), and even load_balance() as it moves tasks from runqueue
 * to runqueue.
 *
 * This function is only called from enqueue_task(), but also only updates
 * the timestamp if it is already not set.  It's assumed that
 * sched_info_dequeued() will clear that stamp when appropriate.
 */
static inline void sched_info_queued(task_t *t)
{
        if (!t->sched_info.last_queued)
                t->sched_info.last_queued = jiffies;
}

/*
 * Called when a process ceases being the active-running process, either
 * voluntarily or involuntarily.  Now we can calculate how long we ran.
 */
static inline void sched_info_depart(task_t *t)
{
        struct runqueue *rq = task_rq(t);
        unsigned long diff = jiffies - t->sched_info.last_arrival;

        t->sched_info.cpu_time += diff;

        if (rq)
                rq->rq_sched_info.cpu_time += diff;
}

/*
 * Called when tasks are switched involuntarily due, typically, to expiring
 * their time slice.  (This may also be called when switching to or from
 * the idle task.)  We are only called when prev != next.
 */
static inline void sched_info_switch(task_t *prev, task_t *next)
{
        struct runqueue *rq = task_rq(prev);

        /*
         * prev now departs the cpu.  It's not interesting to record
         * stats about how efficient we were at scheduling the idle
         * process, however.
         */
        if (prev != rq->idle)
                sched_info_depart(prev);

        if (next != rq->idle)
                sched_info_arrive(next);
}
#else
#define sched_info_queued(t)            do { } while (0)
#define sched_info_switch(t, next)      do { } while (0)
#endif /* CONFIG_SCHEDSTATS */

/*
 * Adding/removing a task to/from a priority array:
 */
static void dequeue_task(struct task_struct *p, prio_array_t *array)
{
        array->nr_active--;
        list_del(&p->run_list);
        if (list_empty(array->queue + p->prio))
                __clear_bit(p->prio, array->bitmap);
}

static void enqueue_task(struct task_struct *p, prio_array_t *array)
{
        sched_info_queued(p);
        list_add_tail(&p->run_list, array->queue + p->prio);
        __set_bit(p->prio, array->bitmap);
        array->nr_active++;
        p->array = array;
}

/*
 * Used by the migration code - we pull tasks from the head of the
 * remote queue so we want these tasks to show up at the head of the
 * local queue:
 */
static inline void enqueue_task_head(struct task_struct *p, prio_array_t *array)
{
        list_add(&p->run_list, array->queue + p->prio);
        __set_bit(p->prio, array->bitmap);
        array->nr_active++;
        p->array = array;
}

/*
 * effective_prio - return the priority that is based on the static
 * priority but is modified by bonuses/penalties.
 *
 * We scale the actual sleep average [0 .... MAX_SLEEP_AVG]
 * into the -5 ... 0 ... +5 bonus/penalty range.
 *
 * We use 25% of the full 0...39 priority range so that:
 *
 * 1) nice +19 interactive tasks do not preempt nice 0 CPU hogs.
 * 2) nice -20 CPU hogs do not get preempted by nice 0 tasks.
 *
 * Both properties are important to certain workloads.
 */
static int effective_prio(task_t *p)
{
        int bonus, prio;

        if (rt_task(p))
                return p->prio;

        bonus = CURRENT_BONUS(p) - MAX_BONUS / 2;

        prio = p->static_prio - bonus;
        if (prio < MAX_RT_PRIO)
                prio = MAX_RT_PRIO;
        if (prio > MAX_PRIO-1)
                prio = MAX_PRIO-1;
        return prio;
}

/*
 * __activate_task - move a task to the runqueue.
 */
static inline void __activate_task(task_t *p, runqueue_t *rq)
{
        enqueue_task(p, rq->active);
        rq->nr_running++;
}

/*
 * __activate_idle_task - move idle task to the _front_ of runqueue.
 */
static inline void __activate_idle_task(task_t *p, runqueue_t *rq)
{
        enqueue_task_head(p, rq->active);
        rq->nr_running++;
}

static void recalc_task_prio(task_t *p, unsigned long long now)
{
        unsigned long long __sleep_time = now - p->timestamp;
        unsigned long sleep_time;

        if (__sleep_time > NS_MAX_SLEEP_AVG)
                sleep_time = NS_MAX_SLEEP_AVG;
        else
                sleep_time = (unsigned long)__sleep_time;

        if (likely(sleep_time > 0)) {
                /*
                 * User tasks that sleep a long time are categorised as
                 * idle and will get just interactive status to stay active &
                 * prevent them suddenly becoming cpu hogs and starving
                 * other processes.
                 */
                if (p->mm && p->activated != -1 &&
                        sleep_time > INTERACTIVE_SLEEP(p)) {
                                p->sleep_avg = JIFFIES_TO_NS(MAX_SLEEP_AVG -
                                                DEF_TIMESLICE);
                                if (!HIGH_CREDIT(p))
                                        p->interactive_credit++;
                } else {
                        /*
                         * The lower the sleep avg a task has the more
                         * rapidly it will rise with sleep time.
                         */
                        sleep_time *= (MAX_BONUS - CURRENT_BONUS(p)) ? : 1;

                        /*
                         * Tasks with low interactive_credit are limited to
                         * one timeslice worth of sleep avg bonus.
                         */
                        if (LOW_CREDIT(p) &&
                            sleep_time > JIFFIES_TO_NS(task_timeslice(p)))
                                sleep_time = JIFFIES_TO_NS(task_timeslice(p));

                        /*
                         * Non high_credit tasks waking from uninterruptible
                         * sleep are limited in their sleep_avg rise as they
                         * are likely to be cpu hogs waiting on I/O
                         */
                        if (p->activated == -1 && !HIGH_CREDIT(p) && p->mm) {
                                if (p->sleep_avg >= INTERACTIVE_SLEEP(p))
                                        sleep_time = 0;
                                else if (p->sleep_avg + sleep_time >=
                                                INTERACTIVE_SLEEP(p)) {
                                        p->sleep_avg = INTERACTIVE_SLEEP(p);
                                        sleep_time = 0;
                                }
                        }

                        /*
                         * This code gives a bonus to interactive tasks.
                         *
                         * The boost works by updating the 'average sleep time'
                         * value here, based on ->timestamp. The more time a
                         * task spends sleeping, the higher the average gets -
                         * and the higher the priority boost gets as well.
                         */
                        p->sleep_avg += sleep_time;

                        if (p->sleep_avg > NS_MAX_SLEEP_AVG) {
                                p->sleep_avg = NS_MAX_SLEEP_AVG;
                                if (!HIGH_CREDIT(p))
                                        p->interactive_credit++;
                        }
                }
        }

        p->prio = effective_prio(p);
}

/*
 * activate_task - move a task to the runqueue and do priority recalculation
 *
 * Update all the scheduling statistics stuff. (sleep average
 * calculation, priority modifiers, etc.)
 */
static void activate_task(task_t *p, runqueue_t *rq, int local)
{
        unsigned long long now;

        now = sched_clock();
#ifdef CONFIG_SMP
        if (!local) {
                /* Compensate for drifting sched_clock */
                runqueue_t *this_rq = this_rq();
                now = (now - this_rq->timestamp_last_tick)
                        + rq->timestamp_last_tick;
        }
#endif

        recalc_task_prio(p, now);

        /*
         * This checks to make sure it's not an uninterruptible task
         * that is now waking up.
         */
        if (!p->activated) {
                /*
                 * Tasks which were woken up by interrupts (ie. hw events)
                 * are most likely of interactive nature. So we give them
                 * the credit of extending their sleep time to the period
                 * of time they spend on the runqueue, waiting for execution
                 * on a CPU, first time around:
                 */
                if (in_interrupt())
                        p->activated = 2;
                else {
                        /*
                         * Normal first-time wakeups get a credit too for
                         * on-runqueue time, but it will be weighted down:
                         */
                        p->activated = 1;
                }
        }
        p->timestamp = now;

        __activate_task(p, rq);
}

/*
 * deactivate_task - remove a task from the runqueue.
 */
static void deactivate_task(struct task_struct *p, runqueue_t *rq)
{
        rq->nr_running--;
        dequeue_task(p, p->array);
        p->array = NULL;
}

/*
 * 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
static void resched_task(task_t *p)
{
        int need_resched, nrpolling;

        BUG_ON(!spin_is_locked(&task_rq(p)->lock));

        /* minimise the chance of sending an interrupt to poll_idle() */
        nrpolling = test_tsk_thread_flag(p,TIF_POLLING_NRFLAG);
        need_resched = test_and_set_tsk_thread_flag(p,TIF_NEED_RESCHED);
        nrpolling |= test_tsk_thread_flag(p,TIF_POLLING_NRFLAG);

        if (!need_resched && !nrpolling && (task_cpu(p) != smp_processor_id()))
                smp_send_reschedule(task_cpu(p));
}
#else
static inline void resched_task(task_t *p)
{
        set_tsk_need_resched(p);
}
#endif

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

#ifdef CONFIG_SMP
enum request_type {
        REQ_MOVE_TASK,
        REQ_SET_DOMAIN,
};

typedef struct {
        struct list_head list;
        enum request_type type;

        /* For REQ_MOVE_TASK */
        task_t *task;
        int dest_cpu;

        /* For REQ_SET_DOMAIN */
        struct sched_domain *sd;

        struct completion done;
} migration_req_t;

/*
 * The task's runqueue lock must be held.
 * Returns true if you have to wait for migration thread.
 */
static int migrate_task(task_t *p, int dest_cpu, migration_req_t *req)
{
        runqueue_t *rq = task_rq(p);

        /*
         * If the task is not on a runqueue (and not running), then
         * it is sufficient to simply update the task's cpu field.
         */
        if (!p->array && !task_running(rq, p)) {
                set_task_cpu(p, dest_cpu);
                return 0;
        }

        init_completion(&req->done);
        req->type = REQ_MOVE_TASK;
        req->task = p;
        req->dest_cpu = dest_cpu;
        list_add(&req->list, &rq->migration_queue);
        return 1;
}

/*
 * wait_task_inactive - wait for a thread to unschedule.
 *
 * 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.
 */
void wait_task_inactive(task_t * p)
{
        unsigned long flags;
        runqueue_t *rq;
        int preempted;

repeat:
        rq = task_rq_lock(p, &flags);
        /* Must be off runqueue entirely, not preempted. */
        if (unlikely(p->array)) {
                /* If it's preempted, we yield.  It could be a while. */
                preempted = !task_running(rq, p);
                task_rq_unlock(rq, &flags);
                cpu_relax();
                if (preempted)
                        yield();
                goto repeat;
        }
        task_rq_unlock(rq, &flags);
}

/***
 * 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.)
 */
void kick_process(task_t *p)
{
        int cpu;

        preempt_disable();
        cpu = task_cpu(p);
        if ((cpu != smp_processor_id()) && task_curr(p))
                smp_send_reschedule(cpu);
        preempt_enable();
}

/*
 * Return a low guess at the load of a migration-source cpu.
 *
 * We want to under-estimate the load of migration sources, to
 * balance conservatively.
 */
static inline unsigned long source_load(int cpu)
{
        runqueue_t *rq = cpu_rq(cpu);
        unsigned long load_now = rq->nr_running * SCHED_LOAD_SCALE;

        return min(rq->cpu_load, load_now);
}

/*
 * Return a high guess at the load of a migration-target cpu
 */
static inline unsigned long target_load(int cpu)
{
        runqueue_t *rq = cpu_rq(cpu);
        unsigned long load_now = rq->nr_running * SCHED_LOAD_SCALE;

        return max(rq->cpu_load, load_now);
}

#endif

/*
 * wake_idle() is useful especially on SMT architectures to wake a
 * task onto an idle sibling if we would otherwise wake it onto a
 * busy sibling.
 *
 * Returns the CPU we should wake onto.
 */
#if defined(ARCH_HAS_SCHED_WAKE_IDLE)
static int wake_idle(int cpu, task_t *p)
{
        cpumask_t tmp;
        runqueue_t *rq = cpu_rq(cpu);
        struct sched_domain *sd;
        int i;

        if (idle_cpu(cpu))
                return cpu;

        sd = rq->sd;
        if (!(sd->flags & SD_WAKE_IDLE))
                return cpu;

        cpus_and(tmp, sd->span, p->cpus_allowed);

        for_each_cpu_mask(i, tmp) {
                if (idle_cpu(i))
                        return i;
        }

        return cpu;
}
#else
static inline int wake_idle(int cpu, task_t *p)
{
        return cpu;
}
#endif

/***
 * try_to_wake_up - wake up a thread
 * @p: the to-be-woken-up thread
 * @state: the mask of task states that can be woken
 * @sync: do a synchronous wakeup?
 *
 * 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 failure only if the task is already active.
 */
static int try_to_wake_up(task_t * p, unsigned int state, int sync)
{
        int cpu, this_cpu, success = 0;
        unsigned long flags;
        long old_state;
        runqueue_t *rq;
#ifdef CONFIG_SMP
        unsigned long load, this_load;
        struct sched_domain *sd;
        int new_cpu;
#endif

        rq = task_rq_lock(p, &flags);
        schedstat_inc(rq, ttwu_cnt);
        old_state = p->state;
        if (!(old_state & state))
                goto out;

        if (p->array)
                goto out_running;

        cpu = task_cpu(p);
        this_cpu = smp_processor_id();

#ifdef CONFIG_SMP
        if (unlikely(task_running(rq, p)))
                goto out_activate;

        new_cpu = cpu;

        if (cpu == this_cpu || unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
                goto out_set_cpu;

        load = source_load(cpu);
        this_load = target_load(this_cpu);

        /*
         * If sync wakeup then subtract the (maximum possible) effect of
         * the currently running task from the load of the current CPU:
         */
        if (sync)
                this_load -= SCHED_LOAD_SCALE;

        /* Don't pull the task off an idle CPU to a busy one */
        if (load < SCHED_LOAD_SCALE/2 && this_load > SCHED_LOAD_SCALE/2)
                goto out_set_cpu;

        new_cpu = this_cpu; /* Wake to this CPU if we can */

        /*
         * Scan domains for affine wakeup and passive balancing
         * possibilities.
         */
        for_each_domain(this_cpu, sd) {
                unsigned int imbalance;
                /*
                 * Start passive balancing when half the imbalance_pct
                 * limit is reached.
                 */
                imbalance = sd->imbalance_pct + (sd->imbalance_pct - 100) / 2;

                if ((sd->flags & SD_WAKE_AFFINE) &&
                                !task_hot(p, rq->timestamp_last_tick, sd)) {
                        /*
                         * This domain has SD_WAKE_AFFINE and p is cache cold
                         * in this domain.
                         */
                        if (cpu_isset(cpu, sd->span)) {
                                schedstat_inc(sd, ttwu_wake_affine);
                                goto out_set_cpu;
                        }
                } else if ((sd->flags & SD_WAKE_BALANCE) &&
                                imbalance*this_load <= 100*load) {
                        /*
                         * This domain has SD_WAKE_BALANCE and there is
                         * an imbalance.
                         */
                        if (cpu_isset(cpu, sd->span)) {
                                schedstat_inc(sd, ttwu_wake_balance);
                                goto out_set_cpu;
                        }
                }
        }

        new_cpu = cpu; /* Could not wake to this_cpu. Wake to cpu instead */
out_set_cpu:
        schedstat_inc(rq, ttwu_attempts);
        new_cpu = wake_idle(new_cpu, p);
        if (new_cpu != cpu && cpu_isset(new_cpu, p->cpus_allowed)) {
                schedstat_inc(rq, ttwu_moved);
                set_task_cpu(p, new_cpu);
                task_rq_unlock(rq, &flags);
                /* might preempt at this point */
                rq = task_rq_lock(p, &flags);
                old_state = p->state;
                if (!(old_state & state))
                        goto out;
                if (p->array)
                        goto out_running;

                this_cpu = smp_processor_id();
                cpu = task_cpu(p);
        }

out_activate:
#endif /* CONFIG_SMP */
        if (old_state == TASK_UNINTERRUPTIBLE) {
                rq->nr_uninterruptible--;
                /*
                 * Tasks on involuntary sleep don't earn
                 * sleep_avg beyond just interactive state.
                 */
                p->activated = -1;
        }

        /*
         * Sync wakeups (i.e. those types of wakeups where the waker
         * has indicated that it will leave the CPU in short order)
         * don't trigger a preemption, if the woken up task will run on
         * this cpu. (in this case the 'I will reschedule' promise of
         * the waker guarantees that the freshly woken up task is going
         * to be considered on this CPU.)
         */
        activate_task(p, rq, cpu == this_cpu);
        if (!sync || cpu != this_cpu) {
                if (TASK_PREEMPTS_CURR(p, rq))
                        resched_task(rq->curr);
        }
        success = 1;

out_running:
        p->state = TASK_RUNNING;
out:
        task_rq_unlock(rq, &flags);

        return success;
}

int fastcall wake_up_process(task_t * p)
{
        return try_to_wake_up(p, TASK_STOPPED | TASK_TRACED |
                                 TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE, 0);
}

EXPORT_SYMBOL(wake_up_process);

int fastcall wake_up_state(task_t *p, unsigned int state)
{
        return try_to_wake_up(p, state, 0);
}

#ifdef CONFIG_SMP
static int find_idlest_cpu(struct task_struct *p, int this_cpu,
                           struct sched_domain *sd);
#endif

/*
 * Perform scheduler related setup for a newly forked process p.
 * p is forked by current.
 */
void fastcall sched_fork(task_t *p)
{
        /*
         * We mark the process as running here, but have not actually
         * inserted it onto the runqueue yet. 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;
        INIT_LIST_HEAD(&p->run_list);
        p->array = NULL;
        spin_lock_init(&p->switch_lock);
#ifdef CONFIG_SCHEDSTATS
        memset(&p->sched_info, 0, sizeof(p->sched_info));
#endif
#ifdef CONFIG_PREEMPT
        /*
         * During context-switch we hold precisely one spinlock, which
         * schedule_tail drops. (in the common case it's this_rq()->lock,
         * but it also can be p->switch_lock.) So we compensate with a count
         * of 1. Also, we want to start with kernel preemption disabled.
         */
        p->thread_info->preempt_count = 1;
#endif
        /*
         * Share the timeslice between parent and child, thus the
         * total amount of pending timeslices in the system doesn't change,
         * resulting in more scheduling fairness.
         */
        local_irq_disable();
        p->time_slice = (current->time_slice + 1) >> 1;
        /*
         * The remainder of the first timeslice might be recovered by
         * the parent if the child exits early enough.
         */
        p->first_time_slice = 1;
        current->time_slice >>= 1;
        p->timestamp = sched_clock();
        if (unlikely(!current->time_slice)) {
                /*
                 * This case is rare, it happens when the parent has only
                 * a single jiffy left from its timeslice. Taking the
                 * runqueue lock is not a problem.
                 */
                current->time_slice = 1;
                preempt_disable();
                scheduler_tick(0, 0);
                local_irq_enable();
                preempt_enable();
        } else
                local_irq_enable();
}

/*
 * 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 fastcall wake_up_new_task(task_t * p, unsigned long clone_flags)
{
        unsigned long flags;
        int this_cpu, cpu;
        runqueue_t *rq, *this_rq;

        rq = task_rq_lock(p, &flags);
        cpu = task_cpu(p);
        this_cpu = smp_processor_id();

        BUG_ON(p->state != TASK_RUNNING);

        schedstat_inc(rq, wunt_cnt);
        /*
         * We decrease the sleep average of forking parents
         * and children as well, to keep max-interactive tasks
         * from forking tasks that are max-interactive. The parent
         * (current) is done further down, under its lock.
         */
        p->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(p) *
                CHILD_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);

        p->interactive_credit = 0;

        p->prio = effective_prio(p);

        if (likely(cpu == this_cpu)) {
                if (!(clone_flags & CLONE_VM)) {
                        /*
                         * The VM isn't cloned, so we're in a good position to
                         * do child-runs-first in anticipation of an exec. This
                         * usually avoids a lot of COW overhead.
                         */
                        if (unlikely(!current->array))
                                __activate_task(p, rq);
                        else {
                                p->prio = current->prio;
                                list_add_tail(&p->run_list, &current->run_list);
                                p->array = current->array;
                                p->array->nr_active++;
                                rq->nr_running++;
                        }
                        set_need_resched();
                } else
                        /* Run child last */
                        __activate_task(p, rq);
                /*
                 * We skip the following code due to cpu == this_cpu
                 *
                 *   task_rq_unlock(rq, &flags);
                 *   this_rq = task_rq_lock(current, &flags);
                 */
                this_rq = rq;
        } else {
                this_rq = cpu_rq(this_cpu);

                /*
                 * Not the local CPU - must adjust timestamp. This should
                 * get optimised away in the !CONFIG_SMP case.
                 */
                p->timestamp = (p->timestamp - this_rq->timestamp_last_tick)
                                        + rq->timestamp_last_tick;
                __activate_task(p, rq);
                if (TASK_PREEMPTS_CURR(p, rq))
                        resched_task(rq->curr);

                schedstat_inc(rq, wunt_moved);
                /*
                 * Parent and child are on different CPUs, now get the
                 * parent runqueue to update the parent's ->sleep_avg:
                 */
                task_rq_unlock(rq, &flags);
                this_rq = task_rq_lock(current, &flags);
        }
        current->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(current) *
                PARENT_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
        task_rq_unlock(this_rq, &flags);
}

/*
 * Potentially available exiting-child timeslices are
 * retrieved here - this way the parent does not get
 * penalized for creating too many threads.
 *
 * (this cannot be used to 'generate' timeslices
 * artificially, because any timeslice recovered here
 * was given away by the parent in the first place.)
 */
void fastcall sched_exit(task_t * p)
{
        unsigned long flags;
        runqueue_t *rq;

        /*
         * If the child was a (relative-) CPU hog then decrease
         * the sleep_avg of the parent as well.
         */
        rq = task_rq_lock(p->parent, &flags);
        if (p->first_time_slice) {
                p->parent->time_slice += p->time_slice;
                if (unlikely(p->parent->time_slice > task_timeslice(p)))
                        p->parent->time_slice = task_timeslice(p);
        }
        if (p->sleep_avg < p->parent->sleep_avg)
                p->parent->sleep_avg = p->parent->sleep_avg /
                (EXIT_WEIGHT + 1) * EXIT_WEIGHT + p->sleep_avg /
                (EXIT_WEIGHT + 1);
        task_rq_unlock(rq, &flags);
}

/**
 * finish_task_switch - clean up after a task-switch
 * @prev: the thread we just switched away from.
 *
 * We enter this with the runqueue still locked, and finish_arch_switch()
 * will unlock it along with doing 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(task_t *prev)
        __releases(rq->lock)
{
        runqueue_t *rq = this_rq();
        struct mm_struct *mm = rq->prev_mm;
        unsigned long prev_task_flags;

        rq->prev_mm = NULL;

        /*
         * A task struct has one reference for the use as "current".
         * If a task dies, then it sets EXIT_ZOMBIE in tsk->exit_state and
         * calls schedule one last time. The schedule call will never return,
         * and the scheduled task must drop that reference.
         * The test for EXIT_ZOMBIE 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_task_flags = prev->flags;
        finish_arch_switch(rq, prev);
        if (mm)
                mmdrop(mm);
        if (unlikely(prev_task_flags & PF_DEAD))
                put_task_struct(prev);
}

/**
 * schedule_tail - first thing a freshly forked thread must call.
 * @prev: the thread we just switched away from.
 */
asmlinkage void schedule_tail(task_t *prev)
        __releases(rq->lock)
{
        finish_task_switch(prev);

        if (current->set_child_tid)
                put_user(current->pid, current->set_child_tid);
}

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

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

        if (unlikely(!prev->mm)) {
                prev->active_mm = NULL;
                WARN_ON(rq->prev_mm);
                rq->prev_mm = oldmm;
        }

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

        return prev;
}

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

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

        return sum;
}

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

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

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

        return sum;
}

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

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

        return sum;
}

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

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

        return sum;
}

#ifdef CONFIG_SMP

/*
 * double_rq_lock - safely lock two runqueues
 *
 * Note this does not disable interrupts like task_rq_lock,
 * you need to do so manually before calling.
 */
static void double_rq_lock(runqueue_t *rq1, runqueue_t *rq2)
        __acquires(rq1->lock)
        __acquires(rq2->lock)
{
        if (rq1 == rq2) {
                spin_lock(&rq1->lock);
                __acquire(rq2->lock);   /* Fake it out ;) */
        } else {
                if (rq1 < rq2) {
                        spin_lock(&rq1->lock);
                        spin_lock(&rq2->lock);
                } else {
                        spin_lock(&rq2->lock);
                        spin_lock(&rq1->lock);
                }
        }
}

/*
 * double_rq_unlock - safely unlock two runqueues
 *
 * Note this does not restore interrupts like task_rq_unlock,
 * you need to do so manually after calling.
 */
static void double_rq_unlock(runqueue_t *rq1, runqueue_t *rq2)
        __releases(rq1->lock)
        __releases(rq2->lock)
{
        spin_unlock(&rq1->lock);
        if (rq1 != rq2)
                spin_unlock(&rq2->lock);
        else
                __release(rq2->lock);
}

/*
 * double_lock_balance - lock the busiest runqueue, this_rq is locked already.
 */
static void double_lock_balance(runqueue_t *this_rq, runqueue_t *busiest)
        __releases(this_rq->lock)
        __acquires(busiest->lock)
        __acquires(this_rq->lock)
{
        if (unlikely(!spin_trylock(&busiest->lock))) {
                if (busiest < this_rq) {
                        spin_unlock(&this_rq->lock);
                        spin_lock(&busiest->lock);
                        spin_lock(&this_rq->lock);
                } else
                        spin_lock(&busiest->lock);
        }
}

/*
 * find_idlest_cpu - find the least busy runqueue.
 */
static int find_idlest_cpu(struct task_struct *p, int this_cpu,
                           struct sched_domain *sd)
{
        unsigned long load, min_load, this_load;
        int i, min_cpu;
        cpumask_t mask;

        min_cpu = UINT_MAX;
        min_load = ULONG_MAX;

        cpus_and(mask, sd->span, p->cpus_allowed);

        for_each_cpu_mask(i, mask) {
                load = target_load(i);

                if (load < min_load) {
                        min_cpu = i;
                        min_load = load;

                        /* break out early on an idle CPU: */
                        if (!min_load)
                                break;
                }
        }

        /* add +1 to account for the new task */
        this_load = source_load(this_cpu) + SCHED_LOAD_SCALE;

        /*
         * Would with the addition of the new task to the
         * current CPU there be an imbalance between this
         * CPU and the idlest CPU?
         *
         * Use half of the balancing threshold - new-context is
         * a good opportunity to balance.
         */
        if (min_load*(100 + (sd->imbalance_pct-100)/2) < this_load*100)
                return min_cpu;

        return this_cpu;
}

/*
 * If dest_cpu is allowed for this process, migrate the task to it.
 * This is accomplished by forcing the cpu_allowed mask to only
 * allow dest_cpu, which will force the cpu onto dest_cpu.  Then
 * the cpu_allowed mask is restored.
 */
static void sched_migrate_task(task_t *p, int dest_cpu)
{
        migration_req_t req;
        runqueue_t *rq;
        unsigned long flags;

        rq = task_rq_lock(p, &flags);
        if (!cpu_isset(dest_cpu, p->cpus_allowed)
            || unlikely(cpu_is_offline(dest_cpu)))
                goto out;

        schedstat_inc(rq, smt_cnt);
        /* force the process onto the specified CPU */
        if (migrate_task(p, dest_cpu, &req)) {
                /* Need to wait for migration thread (might exit: take ref). */
                struct task_struct *mt = rq->migration_thread;
                get_task_struct(mt);
                task_rq_unlock(rq, &flags);
                wake_up_process(mt);
                put_task_struct(mt);
                wait_for_completion(&req.done);
                return;
        }
out:
        task_rq_unlock(rq, &flags);
}

/*
 * sched_exec(): find the highest-level, exec-balance-capable
 * domain and try to migrate the task to the least loaded CPU.
 *
 * 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 sched_domain *tmp, *sd = NULL;
        int new_cpu, this_cpu = get_cpu();

        schedstat_inc(this_rq(), sbe_cnt);
        /* Prefer the current CPU if there's only this task running */
        if (this_rq()->nr_running <= 1)
                goto out;

        for_each_domain(this_cpu, tmp)
                if (tmp->flags & SD_BALANCE_EXEC)
                        sd = tmp;

        if (sd) {
                schedstat_inc(sd, sbe_attempts);
                new_cpu = find_idlest_cpu(current, this_cpu, sd);
                if (new_cpu != this_cpu) {
                        schedstat_inc(sd, sbe_pushed);
                        put_cpu();
                        sched_migrate_task(current, new_cpu);
                        return;
                }
        }
out:
        put_cpu();
}

/*
 * pull_task - move a task from a remote runqueue to the local runqueue.
 * Both runqueues must be locked.
 */
static inline
void pull_task(runqueue_t *src_rq, prio_array_t *src_array, task_t *p,
               runqueue_t *this_rq, prio_array_t *this_array, int this_cpu)
{
        dequeue_task(p, src_array);
        src_rq->nr_running--;
        set_task_cpu(p, this_cpu);
        this_rq->nr_running++;
        enqueue_task(p, this_array);
        p->timestamp = (p->timestamp - src_rq->timestamp_last_tick)
                                + this_rq->timestamp_last_tick;
        /*
         * Note that idle threads have a prio of MAX_PRIO, for this test
         * to be always true for them.
         */
        if (TASK_PREEMPTS_CURR(p, this_rq))
                resched_task(this_rq->curr);
}

/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static inline
int can_migrate_task(task_t *p, runqueue_t *rq, int this_cpu,
                     struct sched_domain *sd, enum idle_type idle)
{
        /*
         * We do not migrate tasks that are:
         * 1) running (obviously), or
         * 2) cannot be migrated to this CPU due to cpus_allowed, or
         * 3) are cache-hot on their current CPU.
         */
        if (task_running(rq, p))
                return 0;
        if (!cpu_isset(this_cpu, p->cpus_allowed))
                return 0;

        /* Aggressive migration if we've failed balancing */
        if (idle == NEWLY_IDLE ||
                        sd->nr_balance_failed < sd->cache_nice_tries) {
                if (task_hot(p, rq->timestamp_last_tick, sd))
                        return 0;
        }

        return 1;
}

/*
 * move_tasks tries to move up to max_nr_move tasks from busiest to this_rq,
 * as part of a balancing operation within "domain". Returns the number of
 * tasks moved.
 *
 * Called with both runqueues locked.
 */
static int move_tasks(runqueue_t *this_rq, int this_cpu, runqueue_t *busiest,
                      unsigned long max_nr_move, struct sched_domain *sd,
                      enum idle_type idle)
{
        prio_array_t *array, *dst_array;
        struct list_head *head, *curr;
        int idx, pulled = 0;
        task_t *tmp;

        if (max_nr_move <= 0 || busiest->nr_running <= 1)
                goto out;

        /*
         * We first consider expired tasks. Those will likely not be
         * executed in the near future, and they are most likely to
         * be cache-cold, thus switching CPUs has the least effect
         * on them.
         */
        if (busiest->expired->nr_active) {
                array = busiest->expired;
                dst_array = this_rq->expired;
        } else {
                array = busiest->active;
                dst_array = this_rq->active;
        }

new_array:
        /* Start searching at priority 0: */
        idx = 0;
skip_bitmap:
        if (!idx)
                idx = sched_find_first_bit(array->bitmap);
        else
                idx = find_next_bit(array->bitmap, MAX_PRIO, idx);
        if (idx >= MAX_PRIO) {
                if (array == busiest->expired && busiest->active->nr_active) {
                        array = busiest->active;
                        dst_array = this_rq->active;
                        goto new_array;
                }
                goto out;
        }

        head = array->queue + idx;
        curr = head->prev;
skip_queue:
        tmp = list_entry(curr, task_t, run_list);

        curr = curr->prev;

        if (!can_migrate_task(tmp, busiest, this_cpu, sd, idle)) {
                if (curr != head)
                        goto skip_queue;
                idx++;
                goto skip_bitmap;
        }

        /*
         * Right now, this is the only place pull_task() is called,
         * so we can safely collect pull_task() stats here rather than
         * inside pull_task().
         */
        schedstat_inc(this_rq, pt_gained[idle]);
        schedstat_inc(busiest, pt_lost[idle]);

        pull_task(busiest, array, tmp, this_rq, dst_array, this_cpu);
        pulled++;

        /* We only want to steal up to the prescribed number of tasks. */
        if (pulled < max_nr_move) {
                if (curr != head)
                        goto skip_queue;
                idx++;
                goto skip_bitmap;
        }
out:
        return pulled;
}

/*
 * find_busiest_group finds and returns the busiest CPU group within the
 * domain. It calculates and returns the number of tasks which should be
 * moved to restore balance via the imbalance parameter.
 */
static struct sched_group *
find_busiest_group(struct sched_domain *sd, int this_cpu,
                   unsigned long *imbalance, enum idle_type idle)
{
        struct sched_group *busiest = NULL, *this = NULL, *group = sd->groups;
        unsigned long max_load, avg_load, total_load, this_load, total_pwr;

        max_load = this_load = total_load = total_pwr = 0;

        do {
                unsigned long load;
                int local_group;
                int i, nr_cpus = 0;

                local_group = cpu_isset(this_cpu, group->cpumask);

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

                for_each_cpu_mask(i, group->cpumask) {
                        /* Bias balancing toward cpus of our domain */
                        if (local_group)
                                load = target_load(i);
                        else
                                load = source_load(i);

                        nr_cpus++;
                        avg_load += load;
                }

                if (!nr_cpus)
                        goto nextgroup;

                total_load += avg_load;
                total_pwr += group->cpu_power;

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

                if (local_group) {
                        this_load = avg_load;
                        this = group;
                        goto nextgroup;
                } else if (avg_load > max_load) {
                        max_load = avg_load;
                        busiest = group;
                }
nextgroup:
                group = group->next;
        } while (group != sd->groups);

        if (!busiest || this_load >= max_load)
                goto out_balanced;

        avg_load = (SCHED_LOAD_SCALE * total_load) / total_pwr;

        if (this_load >= avg_load ||
                        100*max_load <= sd->imbalance_pct*this_load)
                goto out_balanced;

        /*
         * We're trying to get all the cpus to the average_load, so we don't
         * want to push ourselves above the average load, nor do we wish to
         * reduce the max loaded cpu below the average load, as either of these
         * actions would just result in more rebalancing later, and ping-pong
         * tasks around. Thus we look for the minimum possible imbalance.
         * Negative imbalances (*we* are more loaded than anyone else) will
         * be counted as no imbalance for these purposes -- we can't fix that
         * by pulling tasks to us.  Be careful of negative numbers as they'll
         * appear as very large values with unsigned longs.
         */
        *imbalance = min(max_load - avg_load, avg_load - this_load);

        /* How much load to actually move to equalise the imbalance */
        *imbalance = (*imbalance * min(busiest->cpu_power, this->cpu_power))
                                / SCHED_LOAD_SCALE;

        if (*imbalance < SCHED_LOAD_SCALE - 1) {
                unsigned long pwr_now = 0, pwr_move = 0;
                unsigned long tmp;

                if (max_load - this_load >= SCHED_LOAD_SCALE*2) {
                        *imbalance = 1;
                        return busiest;
                }

                /*
                 * OK, we don't have enough imbalance to justify moving tasks,
                 * however we may be able to increase total CPU power used by
                 * moving them.
                 */

                pwr_now += busiest->cpu_power*min(SCHED_LOAD_SCALE, max_load);
                pwr_now += this->cpu_power*min(SCHED_LOAD_SCALE, this_load);
                pwr_now /= SCHED_LOAD_SCALE;

                /* Amount of load we'd subtract */
                tmp = SCHED_LOAD_SCALE*SCHED_LOAD_SCALE/busiest->cpu_power;
                if (max_load > tmp)
                        pwr_move += busiest->cpu_power*min(SCHED_LOAD_SCALE,
                                                        max_load - tmp);

                /* Amount of load we'd add */
                tmp = SCHED_LOAD_SCALE*SCHED_LOAD_SCALE/this->cpu_power;
                if (max_load < tmp)
                        tmp = max_load;
                pwr_move += this->cpu_power*min(SCHED_LOAD_SCALE, this_load + tmp);
                pwr_move /= SCHED_LOAD_SCALE;

                /* Move if we gain another 8th of a CPU worth of throughput */
                if (pwr_move < pwr_now + SCHED_LOAD_SCALE / 8)
                        goto out_balanced;

                *imbalance = 1;
                return busiest;
        }

        /* Get rid of the scaling factor, rounding down as we divide */
        *imbalance = (*imbalance + 1) / SCHED_LOAD_SCALE;

        return busiest;

out_balanced:
        if (busiest && (idle == NEWLY_IDLE ||
                        (idle == SCHED_IDLE && max_load > SCHED_LOAD_SCALE)) ) {
                *imbalance = 1;
                return busiest;
        }

        *imbalance = 0;
        return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
static runqueue_t *find_busiest_queue(struct sched_group *group)
{
        unsigned long load, max_load = 0;
        runqueue_t *busiest = NULL;
        int i;

        for_each_cpu_mask(i, group->cpumask) {
                load = source_load(i);

                if (load > max_load) {
                        max_load = load;
                        busiest = cpu_rq(i);
                }
        }

        return busiest;
}

/*
 * Check this_cpu to ensure it is balanced within domain. Attempt to move
 * tasks if there is an imbalance.
 *
 * Called with this_rq unlocked.
 */
static int load_balance(int this_cpu, runqueue_t *this_rq,
                        struct sched_domain *sd, enum idle_type idle)
{
        struct sched_group *group;
        runqueue_t *busiest;
        unsigned long imbalance;
        int nr_moved;

        spin_lock(&this_rq->lock);
        schedstat_inc(sd, lb_cnt[idle]);

        group = find_busiest_group(sd, this_cpu, &imbalance, idle);
        if (!group) {
                schedstat_inc(sd, lb_nobusyg[idle]);
                goto out_balanced;
        }

        busiest = find_busiest_queue(group);
        if (!busiest) {
                schedstat_inc(sd, lb_nobusyq[idle]);
                goto out_balanced;
        }

        /*
         * This should be "impossible", but since load
         * balancing is inherently racy and statistical,
         * it could happen in theory.
         */
        if (unlikely(busiest == this_rq)) {
                WARN_ON(1);
                goto out_balanced;
        }

        schedstat_add(sd, lb_imbalance[idle], imbalance);

        nr_moved = 0;
        if (busiest->nr_running > 1) {
                /*
                 * Attempt to move tasks. If find_busiest_group has found
                 * an imbalance but busiest->nr_running <= 1, the group is
                 * still unbalanced. nr_moved simply stays zero, so it is
                 * correctly treated as an imbalance.
                 */
                double_lock_balance(this_rq, busiest);
                nr_moved = move_tasks(this_rq, this_cpu, busiest,
                                                imbalance, sd, idle);
                spin_unlock(&busiest->lock);
        }
        spin_unlock(&this_rq->lock);

        if (!nr_moved) {
                schedstat_inc(sd, lb_failed[idle]);
                sd->nr_balance_failed++;

                if (unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2)) {
                        int wake = 0;

                        spin_lock(&busiest->lock);
                        if (!busiest->active_balance) {
                                busiest->active_balance = 1;
                                busiest->push_cpu = this_cpu;
                                wake = 1;
                        }
                        spin_unlock(&busiest->lock);
                        if (wake)
                                wake_up_process(busiest->migration_thread);

                        /*
                         * We've kicked active balancing, reset the failure
                         * counter.
                         */
                        sd->nr_balance_failed = sd->cache_nice_tries;
                }

                /*
                 * We were unbalanced, but unsuccessful in move_tasks(),
                 * so bump the balance_interval to lessen the lock contention.
                 */
                if (sd->balance_interval < sd->max_interval)
                        sd->balance_interval++;
        } else {
                sd->nr_balance_failed = 0;

                /* We were unbalanced, so reset the balancing interval */
                sd->balance_interval = sd->min_interval;
        }

        return nr_moved;

out_balanced:
        spin_unlock(&this_rq->lock);

        /* tune up the balancing interval */
        if (sd->balance_interval < sd->max_interval)
                sd->balance_interval *= 2;

        return 0;
}

/*
 * Check this_cpu to ensure it is balanced within domain. Attempt to move
 * tasks if there is an imbalance.
 *
 * Called from schedule when this_rq is about to become idle (NEWLY_IDLE).
 * this_rq is locked.
 */
static int load_balance_newidle(int this_cpu, runqueue_t *this_rq,
                                struct sched_domain *sd)
{
        struct sched_group *group;
        runqueue_t *busiest = NULL;
        unsigned long imbalance;
        int nr_moved = 0;

        schedstat_inc(sd, lb_cnt[NEWLY_IDLE]);
        group = find_busiest_group(sd, this_cpu, &imbalance, NEWLY_IDLE);
        if (!group) {
                schedstat_inc(sd, lb_nobusyg[NEWLY_IDLE]);
                goto out;
        }

        busiest = find_busiest_queue(group);
        if (!busiest || busiest == this_rq) {
                schedstat_inc(sd, lb_nobusyq[NEWLY_IDLE]);
                goto out;
        }

        /* Attempt to move tasks */
        double_lock_balance(this_rq, busiest);

        schedstat_add(sd, lb_imbalance[NEWLY_IDLE], imbalance);
        nr_moved = move_tasks(this_rq, this_cpu, busiest,
                                        imbalance, sd, NEWLY_IDLE);
        if (!nr_moved)
                schedstat_inc(sd, lb_failed[NEWLY_IDLE]);

        spin_unlock(&busiest->lock);

out:
        return nr_moved;
}

/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
static inline void idle_balance(int this_cpu, runqueue_t *this_rq)
{
        struct sched_domain *sd;

        for_each_domain(this_cpu, sd) {
                if (sd->flags & SD_BALANCE_NEWIDLE) {
                        if (load_balance_newidle(this_cpu, this_rq, sd)) {
                                /* We've pulled tasks over so stop searching */
                                break;
                        }
                }
        }
}

#ifdef CONFIG_SCHED_SMT
static int cpu_and_siblings_are_idle(int cpu)
{
        int sib;
        for_each_cpu_mask(sib, cpu_sibling_map[cpu]) {
                if (idle_cpu(sib))
                        continue;
                return 0;
        }

        return 1;
}
#else
#define cpu_and_siblings_are_idle(A) idle_cpu(A)
#endif


/*
 * active_load_balance is run by migration threads. It pushes running tasks
 * off the busiest CPU onto idle CPUs. It requires at least 1 task to be
 * running on each physical CPU where possible, and avoids physical /
 * logical imbalances.
 *
 * Called with busiest_rq locked.
 */
static void active_load_balance(runqueue_t *busiest_rq, int busiest_cpu)
{
        struct sched_domain *sd;
        struct sched_group *cpu_group;
        cpumask_t visited_cpus;

        schedstat_inc(busiest_rq, alb_cnt);
        /*
         * Search for suitable CPUs to push tasks to in successively higher
         * domains with SD_LOAD_BALANCE set.
         */
        visited_cpus = CPU_MASK_NONE;
        for_each_domain(busiest_cpu, sd) {
                if (!(sd->flags & SD_LOAD_BALANCE) || busiest_rq->nr_running <= 1)
                        break; /* no more domains to search or no more tasks to move */

                cpu_group = sd->groups;
                do { /* sched_groups should either use list_heads or be merged into the domains structure */
                        int cpu, target_cpu = -1;
                        runqueue_t *target_rq;

                        for_each_cpu_mask(cpu, cpu_group->cpumask) {
                                if (cpu_isset(cpu, visited_cpus) || cpu == busiest_cpu ||
                                    !cpu_and_siblings_are_idle(cpu)) {
                                        cpu_set(cpu, visited_cpus);
                                        continue;
                                }
                                target_cpu = cpu;
                                break;
                        }
                        if (target_cpu == -1)
                                goto next_group; /* failed to find a suitable target cpu in this domain */

                        target_rq = cpu_rq(target_cpu);

                        /*
                         * This condition is "impossible", if it occurs we need to fix it
                         * Reported by Bjorn Helgaas on a 128-cpu setup.
                         */
                        BUG_ON(busiest_rq == target_rq);

                        /* move a task from busiest_rq to target_rq */
                        double_lock_balance(busiest_rq, target_rq);
                        if (move_tasks(target_rq, target_cpu, busiest_rq, 1, sd, SCHED_IDLE)) {
                                schedstat_inc(busiest_rq, alb_lost);
                                schedstat_inc(target_rq, alb_gained);
                        } else {
                                schedstat_inc(busiest_rq, alb_failed);
                        }
                        spin_unlock(&target_rq->lock);
next_group:
                        cpu_group = cpu_group->next;
                } while (cpu_group != sd->groups && busiest_rq->nr_running > 1);
        }
}

/*
 * rebalance_tick will get called every timer tick, on every CPU.
 *
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
 * Balancing parameters are set up in arch_init_sched_domains.
 */

/* Don't have all balancing operations going off at once */
#define CPU_OFFSET(cpu) (HZ * cpu / NR_CPUS)

static void rebalance_tick(int this_cpu, runqueue_t *this_rq,
                           enum idle_type idle)
{
        unsigned long old_load, this_load;
        unsigned long j = jiffies + CPU_OFFSET(this_cpu);
        struct sched_domain *sd;

        /* Update our load */
        old_load = this_rq->cpu_load;
        this_load = this_rq->nr_running * SCHED_LOAD_SCALE;
        /*
         * Round up the averaging division if load is increasing. This
         * prevents us from getting stuck on 9 if the load is 10, for
         * example.
         */
        if (this_load > old_load)
                old_load++;
        this_rq->cpu_load = (old_load + this_load) / 2;

        for_each_domain(this_cpu, sd) {
                unsigned long interval;

                if (!(sd->flags & SD_LOAD_BALANCE))
                        continue;

                interval = sd->balance_interval;
                if (idle != SCHED_IDLE)
                        interval *= sd->busy_factor;

                /* scale ms to jiffies */
                interval = msecs_to_jiffies(interval);
                if (unlikely(!interval))
                        interval = 1;

                if (j - sd->last_balance >= interval) {
                        if (load_balance(this_cpu, this_rq, sd, idle)) {
                                /* We've pulled tasks over so no longer idle */
                                idle = NOT_IDLE;
                        }
                        sd->last_balance += interval;
                }
        }
}
#else
/*
 * on UP we do not need to balance between CPUs:
 */
static inline void rebalance_tick(int cpu, runqueue_t *rq, enum idle_type idle)
{
}
static inline void idle_balance(int cpu, runqueue_t *rq)
{
}
#endif

static inline int wake_priority_sleeper(runqueue_t *rq)
{
        int ret = 0;
#ifdef CONFIG_SCHED_SMT
        spin_lock(&rq->lock);
        /*
         * If an SMT sibling task has been put to sleep for priority
         * reasons reschedule the idle task to see if it can now run.
         */
        if (rq->nr_running) {
                resched_task(rq->idle);
                ret = 1;
        }
        spin_unlock(&rq->lock);
#endif
        return ret;
}

DEFINE_PER_CPU(struct kernel_stat, kstat);

EXPORT_PER_CPU_SYMBOL(kstat);

/*
 * We place interactive tasks back into the active array, if possible.
 *
 * To guarantee that this does not starve expired tasks we ignore the
 * interactivity of a task if the first expired task had to wait more
 * than a 'reasonable' amount of time. This deadline timeout is
 * load-dependent, as the frequency of array switched decreases with
 * increasing number of running tasks. We also ignore the interactivity
 * if a better static_prio task has expired:
 */
#define EXPIRED_STARVING(rq) \
        ((STARVATION_LIMIT && ((rq)->expired_timestamp && \
                (jiffies - (rq)->expired_timestamp >= \
                        STARVATION_LIMIT * ((rq)->nr_running) + 1))) || \
                        ((rq)->curr->static_prio > (rq)->best_expired_prio))

/*
 * This function gets called by the timer code, with HZ frequency.
 * We call it with interrupts disabled.
 *
 * It also gets called by the fork code, when changing the parent's
 * timeslices.
 */
void scheduler_tick(int user_ticks, int sys_ticks)
{
        int cpu = smp_processor_id();
        struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
        runqueue_t *rq = this_rq();
        task_t *p = current;

        rq->timestamp_last_tick = sched_clock();

        if (rcu_pending(cpu))
                rcu_check_callbacks(cpu, user_ticks);

        /* note: this timer irq context must be accounted for as well */
        if (hardirq_count() - HARDIRQ_OFFSET) {
                cpustat->irq += sys_ticks;
                sys_ticks = 0;
        } else if (softirq_count()) {
                cpustat->softirq += sys_ticks;
                sys_ticks = 0;
        }

        if (p == rq->idle) {
                if (atomic_read(&rq->nr_iowait) > 0)
                        cpustat->iowait += sys_ticks;
                else
                        cpustat->idle += sys_ticks;
                if (wake_priority_sleeper(rq))
                        goto out;
                rebalance_tick(cpu, rq, SCHED_IDLE);
                return;
        }
        if (TASK_NICE(p) > 0)
                cpustat->nice += user_ticks;
        else
                cpustat->user += user_ticks;
        cpustat->system += sys_ticks;

        /* Task might have expired already, but not scheduled off yet */
        if (p->array != rq->active) {
                set_tsk_need_resched(p);
                goto out;
        }
        spin_lock(&rq->lock);
        /*
         * The task was running during this tick - update the
         * time slice counter. Note: we do not update a thread's
         * priority until it either goes to sleep or uses up its
         * timeslice. This makes it possible for interactive tasks
         * to use up their timeslices at their highest priority levels.
         */
        if (rt_task(p)) {
                /*
                 * RR tasks need a special form of timeslice management.
                 * FIFO tasks have no timeslices.
                 */
                if ((p->policy == SCHED_RR) && !--p->time_slice) {
                        p->time_slice = task_timeslice(p);
                        p->first_time_slice = 0;
                        set_tsk_need_resched(p);

                        /* put it at the end of the queue: */
                        dequeue_task(p, rq->active);
                        enqueue_task(p, rq->active);
                }
                goto out_unlock;
        }
        if (!--p->time_slice) {
                dequeue_task(p, rq->active);
                set_tsk_need_resched(p);
                p->prio = effective_prio(p);
                p->time_slice = task_timeslice(p);
                p->first_time_slice = 0;

                if (!rq->expired_timestamp)
                        rq->expired_timestamp = jiffies;
                if (!TASK_INTERACTIVE(p) || EXPIRED_STARVING(rq)) {
                        enqueue_task(p, rq->expired);
                        if (p->static_prio < rq->best_expired_prio)
                                rq->best_expired_prio = p->static_prio;
                } else
                        enqueue_task(p, rq->active);
        } else {
                /*
                 * Prevent a too long timeslice allowing a task to monopolize
                 * the CPU. We do this by splitting up the timeslice into
                 * smaller pieces.
                 *
                 * Note: this does not mean the task's timeslices expire or
                 * get lost in any way, they just might be preempted by
                 * another task of equal priority. (one with higher
                 * priority would have preempted this task already.) We
                 * requeue this task to the end of the list on this priority
                 * level, which is in essence a round-robin of tasks with
                 * equal priority.
                 *
                 * This only applies to tasks in the interactive
                 * delta range with at least TIMESLICE_GRANULARITY to requeue.
                 */
                if (TASK_INTERACTIVE(p) && !((task_timeslice(p) -
                        p->time_slice) % TIMESLICE_GRANULARITY(p)) &&
                        (p->time_slice >= TIMESLICE_GRANULARITY(p)) &&
                        (p->array == rq->active)) {

                        dequeue_task(p, rq->active);
                        set_tsk_need_resched(p);
                        p->prio = effective_prio(p);
                        enqueue_task(p, rq->active);
                }
        }
out_unlock:
        spin_unlock(&rq->lock);
out:
        rebalance_tick(cpu, rq, NOT_IDLE);
}

#ifdef CONFIG_SCHED_SMT
static inline void wake_sleeping_dependent(int this_cpu, runqueue_t *this_rq)
{
        struct sched_domain *sd = this_rq->sd;
        cpumask_t sibling_map;
        int i;

        if (!(sd->flags & SD_SHARE_CPUPOWER))
                return;

        /*
         * Unlock the current runqueue because we have to lock in
         * CPU order to avoid deadlocks. Caller knows that we might
         * unlock. We keep IRQs disabled.
         */
        spin_unlock(&this_rq->lock);

        sibling_map = sd->span;

        for_each_cpu_mask(i, sibling_map)
                spin_lock(&cpu_rq(i)->lock);
        /*
         * We clear this CPU from the mask. This both simplifies the
         * inner loop and keps this_rq locked when we exit:
         */
        cpu_clear(this_cpu, sibling_map);

        for_each_cpu_mask(i, sibling_map) {
                runqueue_t *smt_rq = cpu_rq(i);

                /*
                 * If an SMT sibling task is sleeping due to priority
                 * reasons wake it up now.
                 */
                if (smt_rq->curr == smt_rq->idle && smt_rq->nr_running)
                        resched_task(smt_rq->idle);
        }

        for_each_cpu_mask(i, sibling_map)
                spin_unlock(&cpu_rq(i)->lock);
        /*
         * We exit with this_cpu's rq still held and IRQs
         * still disabled:
         */
}

static inline int dependent_sleeper(int this_cpu, runqueue_t *this_rq)
{
        struct sched_domain *sd = this_rq->sd;
        cpumask_t sibling_map;
        prio_array_t *array;
        int ret = 0, i;
        task_t *p;

        if (!(sd->flags & SD_SHARE_CPUPOWER))
                return 0;

        /*
         * The same locking rules and details apply as for
         * wake_sleeping_dependent():
         */
        spin_unlock(&this_rq->lock);
        sibling_map = sd->span;
        for_each_cpu_mask(i, sibling_map)
                spin_lock(&cpu_rq(i)->lock);
        cpu_clear(this_cpu, sibling_map);

        /*
         * Establish next task to be run - it might have gone away because
         * we released the runqueue lock above:
         */
        if (!this_rq->nr_running)
                goto out_unlock;
        array = this_rq->active;
        if (!array->nr_active)
                array = this_rq->expired;
        BUG_ON(!array->nr_active);

        p = list_entry(array->queue[sched_find_first_bit(array->bitmap)].next,
                task_t, run_list);

        for_each_cpu_mask(i, sibling_map) {
                runqueue_t *smt_rq = cpu_rq(i);
                task_t *smt_curr = smt_rq->curr;

                /*
                 * If a user task with lower static priority than the
                 * running task on the SMT sibling is trying to schedule,
                 * delay it till there is proportionately less timeslice
                 * left of the sibling task to prevent a lower priority
                 * task from using an unfair proportion of the
                 * physical cpu's resources. -ck
                 */
                if (((smt_curr->time_slice * (100 - sd->per_cpu_gain) / 100) >
                        task_timeslice(p) || rt_task(smt_curr)) &&
                        p->mm && smt_curr->mm && !rt_task(p))
                                ret = 1;

                /*
                 * Reschedule a lower priority task on the SMT sibling,
                 * or wake it up if it has been put to sleep for priority
                 * reasons.
                 */
                if ((((p->time_slice * (100 - sd->per_cpu_gain) / 100) >
                        task_timeslice(smt_curr) || rt_task(p)) &&
                        smt_curr->mm && p->mm && !rt_task(smt_curr)) ||
                        (smt_curr == smt_rq->idle && smt_rq->nr_running))
                                resched_task(smt_curr);
        }
out_unlock:
        for_each_cpu_mask(i, sibling_map)
                spin_unlock(&cpu_rq(i)->lock);
        return ret;
}
#else
static inline void wake_sleeping_dependent(int this_cpu, runqueue_t *this_rq)
{
}

static inline int dependent_sleeper(int this_cpu, runqueue_t *this_rq)
{
        return 0;
}
#endif

/*
 * schedule() is the main scheduler function.
 */
asmlinkage void __sched schedule(void)
{
        long *switch_count;
        task_t *prev, *next;
        runqueue_t *rq;
        prio_array_t *array;
        struct list_head *queue;
        unsigned long long now;
        unsigned long run_time;
        int cpu, idx;

        /*
         * 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 (likely(!(current->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)))) {
                if (unlikely(in_atomic())) {
                        printk(KERN_ERR "scheduling while atomic: "
                                "%s/0x%08x/%d\n",
                                current->comm, preempt_count(), current->pid);
                        dump_stack();
                }
        }
        profile_hit(SCHED_PROFILING, __builtin_return_address(0));

need_resched:
        preempt_disable();
        prev = current;
        release_kernel_lock(prev);
need_resched_nonpreemptible:
        rq = this_rq();

        /*
         * The idle thread is not allowed to schedule!
         * Remove this check after it has been exercised a bit.
         */
        if (unlikely(current == rq->idle) && current->state != TASK_RUNNING) {
                printk(KERN_ERR "bad: scheduling from the idle thread!\n");
                dump_stack();
        }

        schedstat_inc(rq, sched_cnt);
        now = sched_clock();
        if (likely(now - prev->timestamp < NS_MAX_SLEEP_AVG))
                run_time = now - prev->timestamp;
        else
                run_time = NS_MAX_SLEEP_AVG;

        /*
         * Tasks with interactive credits get charged less run_time
         * at high sleep_avg to delay them losing their interactive
         * status
         */
        if (HIGH_CREDIT(prev))
                run_time /= (CURRENT_BONUS(prev) ? : 1);

        spin_lock_irq(&rq->lock);

        if (unlikely(current->flags & PF_DEAD))
                current->state = EXIT_DEAD;
        /*
         * if entering off of a kernel preemption go straight
         * to picking the next task.
         */
        switch_count = &prev->nivcsw;
        if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
                switch_count = &prev->nvcsw;
                if (unlikely((prev->state & TASK_INTERRUPTIBLE) &&
                                unlikely(signal_pending(prev))))
                        prev->state = TASK_RUNNING;
                else {
                        if (prev->state == TASK_UNINTERRUPTIBLE)
                                rq->nr_uninterruptible++;
                        deactivate_task(prev, rq);
                }
        }

        cpu = smp_processor_id();
        if (unlikely(!rq->nr_running)) {
go_idle:
                idle_balance(cpu, rq);
                if (!rq->nr_running) {
                        next = rq->idle;
                        rq->expired_timestamp = 0;
                        wake_sleeping_dependent(cpu, rq);
                        /*
                         * wake_sleeping_dependent() might have released
                         * the runqueue, so break out if we got new
                         * tasks meanwhile:
                         */
                        if (!rq->nr_running)
                                goto switch_tasks;
                }
        } else {
                if (dependent_sleeper(cpu, rq)) {
                        next = rq->idle;
                        goto switch_tasks;
                }
                /*
                 * dependent_sleeper() releases and reacquires the runqueue
                 * lock, hence go into the idle loop if the rq went
                 * empty meanwhile:
                 */
                if (unlikely(!rq->nr_running))
                        goto go_idle;
        }

        array = rq->active;
        if (unlikely(!array->nr_active)) {
                /*
                 * Switch the active and expired arrays.
                 */
                schedstat_inc(rq, sched_switch);
                rq->active = rq->expired;
                rq->expired = array;
                array = rq->active;
                rq->expired_timestamp = 0;
                rq->best_expired_prio = MAX_PRIO;
        } else
                schedstat_inc(rq, sched_noswitch);

        idx = sched_find_first_bit(array->bitmap);
        queue = array->queue + idx;
        next = list_entry(queue->next, task_t, run_list);

        if (!rt_task(next) && next->activated > 0) {
                unsigned long long delta = now - next->timestamp;

                if (next->activated == 1)
                        delta = delta * (ON_RUNQUEUE_WEIGHT * 128 / 100) / 128;

                array = next->array;
                dequeue_task(next, array);
                recalc_task_prio(next, next->timestamp + delta);
                enqueue_task(next, array);
        }
        next->activated = 0;
switch_tasks:
        if (next == rq->idle)
                schedstat_inc(rq, sched_goidle);
        prefetch(next);
        clear_tsk_need_resched(prev);
        rcu_qsctr_inc(task_cpu(prev));

        prev->sleep_avg -= run_time;
        if ((long)prev->sleep_avg <= 0) {
                prev->sleep_avg = 0;
                if (!(HIGH_CREDIT(prev) || LOW_CREDIT(prev)))
                        prev->interactive_credit--;
        }
        prev->timestamp = prev->last_ran = now;

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

                prepare_arch_switch(rq, next);
                prev = context_switch(rq, prev, next);
                barrier();

                finish_task_switch(prev);
        } else
                spin_unlock_irq(&rq->lock);

        prev = current;
        if (unlikely(reacquire_kernel_lock(prev) < 0))
                goto need_resched_nonpreemptible;
        preempt_enable_no_resched();
        if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
                goto need_resched;
}

EXPORT_SYMBOL(schedule);

#ifdef CONFIG_PREEMPT
/*
 * this is 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 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 (unlikely(ti->preempt_count || irqs_disabled()))
                return;

need_resched:
        ti->preempt_count = PREEMPT_ACTIVE;
        schedule();
        ti->preempt_count = 0;

        /* we could miss a preemption opportunity between schedule and now */
        barrier();
        if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
                goto need_resched;
}

EXPORT_SYMBOL(preempt_schedule);
#endif /* CONFIG_PREEMPT */

int default_wake_function(wait_queue_t *curr, unsigned mode, int sync, void *key)
{
        task_t *p = curr->task;
        return try_to_wake_up(p, mode, sync);
}

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 sync, void *key)
{
        struct list_head *tmp, *next;

        list_for_each_safe(tmp, next, &q->task_list) {
                wait_queue_t *curr;
                unsigned flags;
                curr = list_entry(tmp, wait_queue_t, task_list);
                flags = curr->flags;
                if (curr->func(curr, mode, sync, 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
 */
void fastcall __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 fastcall __wake_up_locked(wait_queue_head_t *q, unsigned int mode)
{
        __wake_up_common(q, mode, 1, 0, NULL);
}

/**
 * __wake_up - sync- 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
 *
 * 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.
 */
void fastcall __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
{
        unsigned long flags;
        int sync = 1;

        if (unlikely(!q))
                return;

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

        spin_lock_irqsave(&q->lock, flags);
        __wake_up_common(q, mode, nr_exclusive, sync, NULL);
        spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL_GPL(__wake_up_sync);      /* For internal use only */

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

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

void fastcall 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_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
                         0, 0, NULL);
        spin_unlock_irqrestore(&x->wait.lock, flags);
}
EXPORT_SYMBOL(complete_all);

void fastcall __sched wait_for_completion(struct completion *x)
{
        might_sleep();
        spin_lock_irq(&x->wait.lock);
        if (!x->done) {
                DECLARE_WAITQUEUE(wait, current);

                wait.flags |= WQ_FLAG_EXCLUSIVE;
                __add_wait_queue_tail(&x->wait, &wait);
                do {
                        __set_current_state(TASK_UNINTERRUPTIBLE);
                        spin_unlock_irq(&x->wait.lock);
                        schedule();
                        spin_lock_irq(&x->wait.lock);
                } while (!x->done);
                __remove_wait_queue(&x->wait, &wait);
        }
        x->done--;
        spin_unlock_irq(&x->wait.lock);
}
EXPORT_SYMBOL(wait_for_completion);

#define SLEEP_ON_VAR                                    \
        unsigned long flags;                            \
        wait_queue_t wait;                              \
        init_waitqueue_entry(&wait, current);

#define SLEEP_ON_HEAD                                   \
        spin_lock_irqsave(&q->lock,flags);              \
        __add_wait_queue(q, &wait);                     \
        spin_unlock(&q->lock);

#define SLEEP_ON_TAIL                                   \
        spin_lock_irq(&q->lock);                        \
        __remove_wait_queue(q, &wait);                  \
        spin_unlock_irqrestore(&q->lock, flags);

void fastcall __sched interruptible_sleep_on(wait_queue_head_t *q)
{
        SLEEP_ON_VAR

        current->state = TASK_INTERRUPTIBLE;

        SLEEP_ON_HEAD
        schedule();
        SLEEP_ON_TAIL
}

EXPORT_SYMBOL(interruptible_sleep_on);

long fastcall __sched interruptible_sleep_on_timeout(wait_queue_head_t *q, long timeout)
{
        SLEEP_ON_VAR

        current->state = TASK_INTERRUPTIBLE;

        SLEEP_ON_HEAD
        timeout = schedule_timeout(timeout);
        SLEEP_ON_TAIL

        return timeout;
}

EXPORT_SYMBOL(interruptible_sleep_on_timeout);

void fastcall __sched sleep_on(wait_queue_head_t *q)
{
        SLEEP_ON_VAR

        current->state = TASK_UNINTERRUPTIBLE;

        SLEEP_ON_HEAD
        schedule();
        SLEEP_ON_TAIL
}

EXPORT_SYMBOL(sleep_on);

long fastcall __sched sleep_on_timeout(wait_queue_head_t *q, long timeout)
{
        SLEEP_ON_VAR

        current->state = TASK_UNINTERRUPTIBLE;

        SLEEP_ON_HEAD
        timeout = schedule_timeout(timeout);
        SLEEP_ON_TAIL

        return timeout;
}

EXPORT_SYMBOL(sleep_on_timeout);

void set_user_nice(task_t *p, long nice)
{
        unsigned long flags;
        prio_array_t *array;
        runqueue_t *rq;
        int old_prio, new_prio, delta;

        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 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
         * not SCHED_NORMAL:
         */
        if (rt_task(p)) {
                p->static_prio = NICE_TO_PRIO(nice);
                goto out_unlock;
        }
        array = p->array;
        if (array)
                dequeue_task(p, array);

        old_prio = p->prio;
        new_prio = NICE_TO_PRIO(nice);
        delta = new_prio - old_prio;
        p->static_prio = NICE_TO_PRIO(nice);
        p->prio += delta;

        if (array) {
                enqueue_task(p, array);
                /*
                 * 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, &flags);
}

EXPORT_SYMBOL(set_user_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.
 */
asmlinkage long sys_nice(int increment)
{
        int retval;
        long nice;

        /*
         * 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 < 0) {
                if (!capable(CAP_SYS_NICE))
                        return -EPERM;
                if (increment < -40)
                        increment = -40;
        }
        if (increment > 40)
                increment = 40;

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

        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 task_t *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 task_t *p)
{
        return TASK_NICE(p);
}

/**
 * idle_cpu - is a given cpu idle currently?
 * @cpu: the processor in question.
 */
int idle_cpu(int cpu)
{
        return cpu_curr(cpu) == cpu_rq(cpu)->idle;
}

EXPORT_SYMBOL_GPL(idle_cpu);

/**
 * find_process_by_pid - find a process with a matching PID value.
 * @pid: the pid in question.
 */
static inline task_t *find_process_by_pid(pid_t pid)
{
        return pid ? find_task_by_pid(pid) : current;
}

/* Actually do priority change: must hold rq lock. */
static void __setscheduler(struct task_struct *p, int policy, int prio)
{
        BUG_ON(p->array);
        p->policy = policy;
        p->rt_priority = prio;
        if (policy != SCHED_NORMAL)
                p->prio = MAX_USER_RT_PRIO-1 - p->rt_priority;
        else
                p->prio = p->static_prio;
}

/*
 * setscheduler - change the scheduling policy and/or RT priority of a thread.
 */
static int setscheduler(pid_t pid, int policy, struct sched_param __user *param)
{
        struct sched_param lp;
        int retval = -EINVAL;
        int oldprio, oldpolicy = -1;
        prio_array_t *array;
        unsigned long flags;
        runqueue_t *rq;
        task_t *p;

        if (!param || pid < 0)
                goto out_nounlock;

        retval = -EFAULT;
        if (copy_from_user(&lp, param, sizeof(struct sched_param)))
                goto out_nounlock;

        /*
         * We play safe to avoid deadlocks.
         */
        read_lock_irq(&tasklist_lock);

        p = find_process_by_pid(pid);

        retval = -ESRCH;
        if (!p)
                goto out_unlock;
recheck:
        /* double check policy once rq lock held */
        if (policy < 0)
                policy = oldpolicy = p->policy;
        else {
                retval = -EINVAL;
                if (policy != SCHED_FIFO && policy != SCHED_RR &&
                                policy != SCHED_NORMAL)
                        goto out_unlock;
        }
        /*
         * Valid priorities for SCHED_FIFO and SCHED_RR are
         * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL is 0.
         */
        retval = -EINVAL;
        if (lp.sched_priority < 0 || lp.sched_priority > MAX_USER_RT_PRIO-1)
                goto out_unlock;
        if ((policy == SCHED_NORMAL) != (lp.sched_priority == 0))
                goto out_unlock;

        retval = -EPERM;
        if ((policy == SCHED_FIFO || policy == SCHED_RR) &&
            !capable(CAP_SYS_NICE))
                goto out_unlock;
        if ((current->euid != p->euid) && (current->euid != p->uid) &&
            !capable(CAP_SYS_NICE))
                goto out_unlock;

        retval = security_task_setscheduler(p, policy, &lp);
        if (retval)
                goto out_unlock;
        /*
         * To be able to change p->policy safely, the apropriate
         * runqueue lock must be held.
         */
        rq = task_rq_lock(p, &flags);
        /* recheck policy now with rq lock held */
        if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
                policy = oldpolicy = -1;
                task_rq_unlock(rq, &flags);
                goto recheck;
        }
        array = p->array;
        if (array)
                deactivate_task(p, task_rq(p));
        retval = 0;
        oldprio = p->prio;
        __setscheduler(p, policy, lp.sched_priority);
        if (array) {
                __activate_task(p, task_rq(p));
                /*
                 * Reschedule if we are currently running on this runqueue and
                 * our priority decreased, or if we are not currently running on
                 * this runqueue and our priority is higher than the current's
                 */
                if (task_running(rq, p)) {
                        if (p->prio > oldprio)
                                resched_task(rq->curr);
                } else if (TASK_PREEMPTS_CURR(p, rq))
                        resched_task(rq->curr);
        }
        task_rq_unlock(rq, &flags);
out_unlock:
        read_unlock_irq(&tasklist_lock);
out_nounlock:
        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.
 */
asmlinkage long sys_sched_setscheduler(pid_t pid, int policy,
                                       struct sched_param __user *param)
{
        return 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.
 */
asmlinkage long sys_sched_setparam(pid_t pid, struct sched_param __user *param)
{
        return setscheduler(pid, -1, param);
}

/**
 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
 * @pid: the pid in question.
 */
asmlinkage long sys_sched_getscheduler(pid_t pid)
{
        int retval = -EINVAL;
        task_t *p;

        if (pid < 0)
                goto out_nounlock;

        retval = -ESRCH;
        read_lock(&tasklist_lock);
        p = find_process_by_pid(pid);
        if (p) {
                retval = security_task_getscheduler(p);
                if (!retval)
                        retval = p->policy;
        }
        read_unlock(&tasklist_lock);

out_nounlock:
        return retval;
}

/**
 * sys_sched_getscheduler - get the RT priority of a thread
 * @pid: the pid in question.
 * @param: structure containing the RT priority.
 */
asmlinkage long sys_sched_getparam(pid_t pid, struct sched_param __user *param)
{
        struct sched_param lp;
        int retval = -EINVAL;
        task_t *p;

        if (!param || pid < 0)
                goto out_nounlock;

        read_lock(&tasklist_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;
        read_unlock(&tasklist_lock);

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

out_nounlock:
        return retval;

out_unlock:
        read_unlock(&tasklist_lock);
        return retval;
}

long sched_setaffinity(pid_t pid, cpumask_t new_mask)
{
        task_t *p;
        int retval;

        lock_cpu_hotplug();
        read_lock(&tasklist_lock);

        p = find_process_by_pid(pid);
        if (!p) {
                read_unlock(&tasklist_lock);
                unlock_cpu_hotplug();
                return -ESRCH;
        }

        /*
         * It is not safe to call set_cpus_allowed with the
         * tasklist_lock held.  We will bump the task_struct's
         * usage count and then drop tasklist_lock.
         */
        get_task_struct(p);
        read_unlock(&tasklist_lock);

        retval = -EPERM;
        if ((current->euid != p->euid) && (current->euid != p->uid) &&
                        !capable(CAP_SYS_NICE))
                goto out_unlock;

        retval = set_cpus_allowed(p, new_mask);

out_unlock:
        put_task_struct(p);
        unlock_cpu_hotplug();
        return retval;
}

static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
                             cpumask_t *new_mask)
{
        if (len < sizeof(cpumask_t)) {
                memset(new_mask, 0, sizeof(cpumask_t));
        } else if (len > sizeof(cpumask_t)) {
                len = sizeof(cpumask_t);
        }
        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
 */
asmlinkage long sys_sched_setaffinity(pid_t pid, unsigned int len,
                                      unsigned long __user *user_mask_ptr)
{
        cpumask_t new_mask;
        int retval;

        retval = get_user_cpu_mask(user_mask_ptr, len, &new_mask);
        if (retval)
                return retval;

        return sched_setaffinity(pid, new_mask);
}

/*
 * Represents all cpu's present in the system
 * In systems capable of hotplug, this map could dynamically grow
 * as new cpu's are detected in the system via any platform specific
 * method, such as ACPI for e.g.
 */

cpumask_t cpu_present_map;
EXPORT_SYMBOL(cpu_present_map);

#ifndef CONFIG_SMP
cpumask_t cpu_online_map = CPU_MASK_ALL;
cpumask_t cpu_possible_map = CPU_MASK_ALL;
#endif

long sched_getaffinity(pid_t pid, cpumask_t *mask)
{
        int retval;
        task_t *p;

        lock_cpu_hotplug();
        read_lock(&tasklist_lock);

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

        retval = 0;
        cpus_and(*mask, p->cpus_allowed, cpu_possible_map);

out_unlock:
        read_unlock(&tasklist_lock);
        unlock_cpu_hotplug();
        if (retval)
                return retval;

        return 0;
}

/**
 * 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
 */
asmlinkage long sys_sched_getaffinity(pid_t pid, unsigned int len,
                                      unsigned long __user *user_mask_ptr)
{
        int ret;
        cpumask_t mask;

        if (len < sizeof(cpumask_t))
                return -EINVAL;

        ret = sched_getaffinity(pid, &mask);
        if (ret < 0)
                return ret;

        if (copy_to_user(user_mask_ptr, &mask, sizeof(cpumask_t)))
                return -EFAULT;

        return sizeof(cpumask_t);
}

/**
 * sys_sched_yield - yield the current processor to other threads.
 *
 * this function yields the current CPU by moving the calling thread
 * to the expired array. If there are no other threads running on this
 * CPU then this function will return.
 */
asmlinkage long sys_sched_yield(void)
{
        runqueue_t *rq = this_rq_lock();
        prio_array_t *array = current->array;
        prio_array_t *target = rq->expired;

        schedstat_inc(rq, yld_cnt);
        /*
         * We implement yielding by moving the task into the expired
         * queue.
         *
         * (special rule: RT tasks will just roundrobin in the active
         *  array.)
         */
        if (rt_task(current))
                target = rq->active;

        if (current->array->nr_active == 1) {
                schedstat_inc(rq, yld_act_empty);
                if (!rq->expired->nr_active)
                        schedstat_inc(rq, yld_both_empty);
        } else if (!rq->expired->nr_active)
                schedstat_inc(rq, yld_exp_empty);

        dequeue_task(current, array);
        enqueue_task(current, target);

        /*
         * Since we are going to call schedule() anyway, there's
         * no need to preempt or enable interrupts:
         */
        __release(rq->lock);
        _raw_spin_unlock(&rq->lock);
        preempt_enable_no_resched();

        schedule();

        return 0;
}

void __sched __cond_resched(void)
{
        set_current_state(TASK_RUNNING);
        schedule();
}

EXPORT_SYMBOL(__cond_resched);

/**
 * yield - yield the current processor to other threads.
 *
 * this is a shortcut for kernel-space yielding - it marks the
 * thread runnable and calls sys_sched_yield().
 */
void __sched yield(void)
{
        set_current_state(TASK_RUNNING);
        sys_sched_yield();
}

EXPORT_SYMBOL(yield);

/*
 * 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.
 *
 * But don't do that if it is a deliberate, throttling IO wait (this task
 * has set its backing_dev_info: the queue against which it should throttle)
 */
void __sched io_schedule(void)
{
        struct runqueue *rq = this_rq();

        atomic_inc(&rq->nr_iowait);
        schedule();
        atomic_dec(&rq->nr_iowait);
}

EXPORT_SYMBOL(io_schedule);

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

        atomic_inc(&rq->nr_iowait);
        ret = schedule_timeout(timeout);
        atomic_dec(&rq->nr_iowait);
        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.
 */
asmlinkage long sys_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:
                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.
 */
asmlinkage long sys_sched_get_priority_min(int policy)
{
        int ret = -EINVAL;

        switch (policy) {
        case SCHED_FIFO:
        case SCHED_RR:
                ret = 1;
                break;
        case SCHED_NORMAL:
                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.
 */
asmlinkage
long sys_sched_rr_get_interval(pid_t pid, struct timespec __user *interval)
{
        int retval = -EINVAL;
        struct timespec t;
        task_t *p;

        if (pid < 0)
                goto out_nounlock;

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

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

        jiffies_to_timespec(p->policy & SCHED_FIFO ?
                                0 : task_timeslice(p), &t);
        read_unlock(&tasklist_lock);
        retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
out_nounlock:
        return retval;
out_unlock:
        read_unlock(&tasklist_lock);
        return retval;
}

static inline struct task_struct *eldest_child(struct task_struct *p)
{
        if (list_empty(&p->children)) return NULL;
        return list_entry(p->children.next,struct task_struct,sibling);
}

static inline struct task_struct *older_sibling(struct task_struct *p)
{
        if (p->sibling.prev==&p->parent->children) return NULL;
        return list_entry(p->sibling.prev,struct task_struct,sibling);
}

static inline struct task_struct *younger_sibling(struct task_struct *p)
{
        if (p->sibling.next==&p->parent->children) return NULL;
        return list_entry(p->sibling.next,struct task_struct,sibling);
}

static void show_task(task_t * p)
{
        task_t *relative;
        unsigned state;
        unsigned long free = 0;
        static const char *stat_nam[] = { "R", "S", "D", "T", "t", "Z", "X" };

        printk("%-13.13s ", p->comm);
        state = p->state ? __ffs(p->state) + 1 : 0;
        if (state < ARRAY_SIZE(stat_nam))
                printk(stat_nam[state]);
        else
                printk("?");
#if (BITS_PER_LONG == 32)
        if (state == TASK_RUNNING)
                printk(" running ");
        else
                printk(" %08lX ", thread_saved_pc(p));
#else
        if (state == TASK_RUNNING)
                printk("  running task   ");
        else
                printk(" %016lx ", thread_saved_pc(p));
#endif
#ifdef CONFIG_DEBUG_STACK_USAGE
        {
                unsigned long * n = (unsigned long *) (p->thread_info+1);
                while (!*n)
                        n++;
                free = (unsigned long) n - (unsigned long)(p->thread_info+1);
        }
#endif
        printk("%5lu %5d %6d ", free, p->pid, p->parent->pid);
        if ((relative = eldest_child(p)))
                printk("%5d ", relative->pid);
        else
                printk("      ");
        if ((relative = younger_sibling(p)))
                printk("%7d", relative->pid);
        else
                printk("       ");
        if ((relative = older_sibling(p)))
                printk(" %5d", relative->pid);
        else
                printk("      ");
        if (!p->mm)
                printk(" (L-TLB)\n");
        else
                printk(" (NOTLB)\n");

        if (state != TASK_RUNNING)
                show_stack(p, NULL);
}

void show_state(void)
{
        task_t *g, *p;

#if (BITS_PER_LONG == 32)
        printk("\n"
               "                                               sibling\n");
        printk("  task             PC      pid father child younger older\n");
#else
        printk("\n"
               "                                                       sibling\n");
        printk("  task                 PC          pid father child younger older\n");
#endif
        read_lock(&tasklist_lock);
        do_each_thread(g, p) {
                /*
                 * reset the NMI-timeout, listing all files on a slow
                 * console might take alot of time:
                 */
                touch_nmi_watchdog();
                show_task(p);
        } while_each_thread(g, p);

        read_unlock(&tasklist_lock);
}

void __devinit init_idle(task_t *idle, int cpu)
{
        runqueue_t *rq = cpu_rq(cpu);
        unsigned long flags;

        idle->sleep_avg = 0;
        idle->interactive_credit = 0;
        idle->array = NULL;
        idle->prio = MAX_PRIO;
        idle->state = TASK_RUNNING;
        set_task_cpu(idle, cpu);

        spin_lock_irqsave(&rq->lock, flags);
        rq->curr = rq->idle = idle;
        set_tsk_need_resched(idle);
        spin_unlock_irqrestore(&rq->lock, flags);

        /* Set the preempt count _outside_ the spinlocks! */
#ifdef CONFIG_PREEMPT
        idle->thread_info->preempt_count = (idle->lock_depth >= 0);
#else
        idle->thread_info->preempt_count = 0;
#endif
}

/*
 * In a system that switches off the HZ timer nohz_cpu_mask
 * indicates which cpus entered this state. This is used
 * in the rcu update to wait only for active cpus. For system
 * which do not switch off the HZ timer nohz_cpu_mask should
 * always be CPU_MASK_NONE.
 */
cpumask_t nohz_cpu_mask = CPU_MASK_NONE;

#ifdef CONFIG_SMP
/*
 * This is how migration works:
 *
 * 1) we queue a migration_req_t structure in the source CPU's
 *    runqueue and wake up that CPU's migration thread.
 * 2) we down() the locked semaphore => thread blocks.
 * 3) migration thread wakes up (implicitly it forces the migrated
 *    thread off the CPU)
 * 4) it gets the migration request and checks whether the migrated
 *    task is still in the wrong runqueue.
 * 5) if it's in the wrong runqueue then the migration thread removes
 *    it and puts it into the right queue.
 * 6) migration thread up()s the semaphore.
 * 7) we wake up 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(task_t *p, cpumask_t new_mask)
{
        unsigned long flags;
        int ret = 0;
        migration_req_t req;
        runqueue_t *rq;

        rq = task_rq_lock(p, &flags);
        if (!cpus_intersects(new_mask, cpu_online_map)) {
                ret = -EINVAL;
                goto out;
        }

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

        if (migrate_task(p, any_online_cpu(new_mask), &req)) {
                /* Need help from migration thread: drop lock and wait. */
                task_rq_unlock(rq, &flags);
                wake_up_process(rq->migration_thread);
                wait_for_completion(&req.done);
                tlb_migrate_finish(p->mm);
                return 0;
        }
out:
        task_rq_unlock(rq, &flags);
        return ret;
}

EXPORT_SYMBOL_GPL(set_cpus_allowed);

/*
 * 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.
 */
static void __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
{
        runqueue_t *rq_dest, *rq_src;

        if (unlikely(cpu_is_offline(dest_cpu)))
                return;

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

        double_rq_lock(rq_src, rq_dest);
        /* Already moved. */
        if (task_cpu(p) != src_cpu)
                goto out;
        /* Affinity changed (again). */
        if (!cpu_isset(dest_cpu, p->cpus_allowed))
                goto out;

        set_task_cpu(p, dest_cpu);
        if (p->array) {
                /*
                 * Sync timestamp with rq_dest's before activating.
                 * The same thing could be achieved by doing this step
                 * afterwards, and pretending it was a local activate.
                 * This way is cleaner and logically correct.
                 */
                p->timestamp = p->timestamp - rq_src->timestamp_last_tick
                                + rq_dest->timestamp_last_tick;
                deactivate_task(p, rq_src);
                activate_task(p, rq_dest, 0);
                if (TASK_PREEMPTS_CURR(p, rq_dest))
                        resched_task(rq_dest->curr);
        }

out:
        double_rq_unlock(rq_src, rq_dest);
}

/*
 * migration_thread - this is a highprio system thread that performs
 * thread migration by bumping thread off CPU then 'pushing' onto
 * another runqueue.
 */
static int migration_thread(void * data)
{
        runqueue_t *rq;
        int cpu = (long)data;

        rq = cpu_rq(cpu);
        BUG_ON(rq->migration_thread != current);

        set_current_state(TASK_INTERRUPTIBLE);
        while (!kthread_should_stop()) {
                struct list_head *head;
                migration_req_t *req;

                if (current->flags & PF_FREEZE)
                        refrigerator(PF_FREEZE);

                spin_lock_irq(&rq->lock);

                if (cpu_is_offline(cpu)) {
                        spin_unlock_irq(&rq->lock);
                        goto wait_to_die;
                }

                if (rq->active_balance) {
                        active_load_balance(rq, cpu);
                        rq->active_balance = 0;
                }

                head = &rq->migration_queue;

                if (list_empty(head)) {
                        spin_unlock_irq(&rq->lock);
                        schedule();
                        set_current_state(TASK_INTERRUPTIBLE);
                        continue;
                }
                req = list_entry(head->next, migration_req_t, list);
                list_del_init(head->next);

                if (req->type == REQ_MOVE_TASK) {
                        spin_unlock(&rq->lock);
                        __migrate_task(req->task, smp_processor_id(),
                                        req->dest_cpu);
                        local_irq_enable();
                } else if (req->type == REQ_SET_DOMAIN) {
                        rq->sd = req->sd;
                        spin_unlock_irq(&rq->lock);
                } else {
                        spin_unlock_irq(&rq->lock);
                        WARN_ON(1);
                }

                complete(&req->done);
        }
        __set_current_state(TASK_RUNNING);
        return 0;

wait_to_die:
        /* Wait for kthread_stop */
        set_current_state(TASK_INTERRUPTIBLE);
        while (!kthread_should_stop()) {
                schedule();
                set_current_state(TASK_INTERRUPTIBLE);
        }
        __set_current_state(TASK_RUNNING);
        return 0;
}

#ifdef CONFIG_HOTPLUG_CPU
/* Figure out where task on dead CPU should go, use force if neccessary. */
static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *tsk)
{
        int dest_cpu;
        cpumask_t mask;

        /* On same node? */
        mask = node_to_cpumask(cpu_to_node(dead_cpu));
        cpus_and(mask, mask, tsk->cpus_allowed);
        dest_cpu = any_online_cpu(mask);

        /* On any allowed CPU? */
        if (dest_cpu == NR_CPUS)
                dest_cpu = any_online_cpu(tsk->cpus_allowed);

        /* No more Mr. Nice Guy. */
        if (dest_cpu == NR_CPUS) {
                cpus_setall(tsk->cpus_allowed);
                dest_cpu = any_online_cpu(tsk->cpus_allowed);

                /*
                 * Don't tell them about moving exiting tasks or
                 * kernel threads (both mm NULL), since they never
                 * leave kernel.
                 */
                if (tsk->mm && printk_ratelimit())
                        printk(KERN_INFO "process %d (%s) no "
                               "longer affine to cpu%d\n",
                               tsk->pid, tsk->comm, dead_cpu);
        }
        __migrate_task(tsk, dead_cpu, dest_cpu);
}

/*
 * While a dead CPU has no uninterruptible tasks queued at this point,
 * it might still have a nonzero ->nr_uninterruptible counter, because
 * for performance reasons the counter is not stricly tracking tasks to
 * their home CPUs. So we just add the counter to another CPU's counter,
 * to keep the global sum constant after CPU-down:
 */
static void migrate_nr_uninterruptible(runqueue_t *rq_src)
{
        runqueue_t *rq_dest = cpu_rq(any_online_cpu(CPU_MASK_ALL));
        unsigned long flags;

        local_irq_save(flags);
        double_rq_lock(rq_src, rq_dest);
        rq_dest->nr_uninterruptible += rq_src->nr_uninterruptible;
        rq_src->nr_uninterruptible = 0;
        double_rq_unlock(rq_src, rq_dest);
        local_irq_restore(flags);
}

/* Run through task list and migrate tasks from the dead cpu. */
static void migrate_live_tasks(int src_cpu)
{
        struct task_struct *tsk, *t;

        write_lock_irq(&tasklist_lock);

        do_each_thread(t, tsk) {
                if (tsk == current)
                        continue;

                if (task_cpu(tsk) == src_cpu)
                        move_task_off_dead_cpu(src_cpu, tsk);
        } while_each_thread(t, tsk);

        write_unlock_irq(&tasklist_lock);
}

/* Schedules idle task to be the next runnable task on current CPU.
 * It does so by boosting its priority to highest possible and adding it to
 * the _front_ of runqueue. Used by CPU offline code.
 */
void sched_idle_next(void)
{
        int cpu = smp_processor_id();
        runqueue_t *rq = this_rq();
        struct task_struct *p = rq->idle;
        unsigned long flags;

        /* cpu has to be offline */
        BUG_ON(cpu_online(cpu));

        /* Strictly not necessary since rest of the CPUs are stopped by now
         * and interrupts disabled on current cpu.
         */
        spin_lock_irqsave(&rq->lock, flags);

        __setscheduler(p, SCHED_FIFO, MAX_RT_PRIO-1);
        /* Add idle task to _front_ of it's priority queue */
        __activate_idle_task(p, rq);

        spin_unlock_irqrestore(&rq->lock, flags);
}

static void migrate_dead(unsigned int dead_cpu, task_t *tsk)
{
        struct runqueue *rq = cpu_rq(dead_cpu);

        /* Must be exiting, otherwise would be on tasklist. */
        BUG_ON(tsk->exit_state != EXIT_ZOMBIE && tsk->exit_state != EXIT_DEAD);

        /* Cannot have done final schedule yet: would have vanished. */
        BUG_ON(tsk->flags & PF_DEAD);

        get_task_struct(tsk);

        /*
         * Drop lock around migration; if someone else moves it,
         * that's OK.  No task can be added to this CPU, so iteration is
         * fine.
         */
        spin_unlock_irq(&rq->lock);
        move_task_off_dead_cpu(dead_cpu, tsk);
        spin_lock_irq(&rq->lock);

        put_task_struct(tsk);
}

/* release_task() removes task from tasklist, so we won't find dead tasks. */
static void migrate_dead_tasks(unsigned int dead_cpu)
{
        unsigned arr, i;
        struct runqueue *rq = cpu_rq(dead_cpu);

        for (arr = 0; arr < 2; arr++) {
                for (i = 0; i < MAX_PRIO; i++) {
                        struct list_head *list = &rq->arrays[arr].queue[i];
                        while (!list_empty(list))
                                migrate_dead(dead_cpu,
                                             list_entry(list->next, task_t,
                                                        run_list));
                }
        }
}
#endif /* CONFIG_HOTPLUG_CPU */

/*
 * 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;
        struct task_struct *p;
        struct runqueue *rq;
        unsigned long flags;

        switch (action) {
        case CPU_UP_PREPARE:
                p = kthread_create(migration_thread, hcpu, "migration/%d",cpu);
                if (IS_ERR(p))
                        return NOTIFY_BAD;
                p->flags |= PF_NOFREEZE;
                kthread_bind(p, cpu);
                /* Must be high prio: stop_machine expects to yield to it. */
                rq = task_rq_lock(p, &flags);
                __setscheduler(p, SCHED_FIFO, MAX_RT_PRIO-1);
                task_rq_unlock(rq, &flags);
                cpu_rq(cpu)->migration_thread = p;
                break;
        case CPU_ONLINE:
                /* Strictly unneccessary, as first user will wake it. */
                wake_up_process(cpu_rq(cpu)->migration_thread);
                break;
#ifdef CONFIG_HOTPLUG_CPU
        case CPU_UP_CANCELED:
                /* Unbind it from offline cpu so it can run.  Fall thru. */
                kthread_bind(cpu_rq(cpu)->migration_thread,smp_processor_id());
                kthread_stop(cpu_rq(cpu)->migration_thread);
                cpu_rq(cpu)->migration_thread = NULL;
                break;
        case CPU_DEAD:
                migrate_live_tasks(cpu);
                rq = cpu_rq(cpu);
                kthread_stop(rq->migration_thread);
                rq->migration_thread = NULL;
                /* Idle task back to normal (off runqueue, low prio) */
                rq = task_rq_lock(rq->idle, &flags);
                deactivate_task(rq->idle, rq);
                rq->idle->static_prio = MAX_PRIO;
                __setscheduler(rq->idle, SCHED_NORMAL, 0);
                migrate_dead_tasks(cpu);
                task_rq_unlock(rq, &flags);
                migrate_nr_uninterruptible(rq);
                BUG_ON(rq->nr_running != 0);

                /* No need to migrate the tasks: it was best-effort if
                 * they didn't do lock_cpu_hotplug().  Just wake up
                 * the requestors. */
                spin_lock_irq(&rq->lock);
                while (!list_empty(&rq->migration_queue)) {
                        migration_req_t *req;
                        req = list_entry(rq->migration_queue.next,
                                         migration_req_t, list);
                        BUG_ON(req->type != REQ_MOVE_TASK);
                        list_del_init(&req->list);
                        complete(&req->done);
                }
                spin_unlock_irq(&rq->lock);
                break;
#endif
        }
        return NOTIFY_OK;
}

/* Register at highest priority so that task migration (migrate_all_tasks)
 * happens before everything else.
 */
static struct notifier_block __devinitdata migration_notifier = {
        .notifier_call = migration_call,
        .priority = 10
};

int __init migration_init(void)
{
        void *cpu = (void *)(long)smp_processor_id();
        /* Start one for boot CPU. */
        migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
        migration_call(&migration_notifier, CPU_ONLINE, cpu);
        register_cpu_notifier(&migration_notifier);
        return 0;
}
#endif

#ifdef CONFIG_SMP
/*
 * Attach the domain 'sd' to 'cpu' as its base domain.  Callers must
 * hold the hotplug lock.
 */
void __devinit cpu_attach_domain(struct sched_domain *sd, int cpu)
{
        migration_req_t req;
        unsigned long flags;
        runqueue_t *rq = cpu_rq(cpu);
        int local = 1;

        spin_lock_irqsave(&rq->lock, flags);

        if (cpu == smp_processor_id() || !cpu_online(cpu)) {
                rq->sd = sd;
        } else {
                init_completion(&req.done);
                req.type = REQ_SET_DOMAIN;
                req.sd = sd;
                list_add(&req.list, &rq->migration_queue);
                local = 0;
        }

        spin_unlock_irqrestore(&rq->lock, flags);

        if (!local) {
                wake_up_process(rq->migration_thread);
                wait_for_completion(&req.done);
        }
}

/* cpus with isolated domains */
cpumask_t __devinitdata cpu_isolated_map = CPU_MASK_NONE;

/* Setup the mask of cpus configured for isolated domains */
static int __init isolated_cpu_setup(char *str)
{
        int ints[NR_CPUS], i;

        str = get_options(str, ARRAY_SIZE(ints), ints);
        cpus_clear(cpu_isolated_map);
        for (i = 1; i <= ints[0]; i++)
                cpu_set(ints[i], cpu_isolated_map);
        return 1;
}

__setup ("isolcpus=", isolated_cpu_setup);

/*
 * init_sched_build_groups takes an array of groups, the cpumask we wish
 * to span, and a pointer to a function which identifies what group a CPU
 * belongs to. The return value of group_fn must be a valid index into the
 * groups[] array, and must be >= 0 and < NR_CPUS (due to the fact that we
 * keep track of groups covered with a cpumask_t).
 *
 * init_sched_build_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.
 */
void __devinit init_sched_build_groups(struct sched_group groups[],
                        cpumask_t span, int (*group_fn)(int cpu))
{
        struct sched_group *first = NULL, *last = NULL;
        cpumask_t covered = CPU_MASK_NONE;
        int i;

        for_each_cpu_mask(i, span) {
                int group = group_fn(i);
                struct sched_group *sg = &groups[group];
                int j;

                if (cpu_isset(i, covered))
                        continue;

                sg->cpumask = CPU_MASK_NONE;
                sg->cpu_power = 0;

                for_each_cpu_mask(j, span) {
                        if (group_fn(j) != group)
                                continue;

                        cpu_set(j, covered);
                        cpu_set(j, sg->cpumask);
                }
                if (!first)
                        first = sg;
                if (last)
                        last->next = sg;
                last = sg;
        }
        last->next = first;
}


#ifdef ARCH_HAS_SCHED_DOMAIN
extern void __devinit arch_init_sched_domains(void);
extern void __devinit arch_destroy_sched_domains(void);
#else
#ifdef CONFIG_SCHED_SMT
static DEFINE_PER_CPU(struct sched_domain, cpu_domains);
static struct sched_group sched_group_cpus[NR_CPUS];
static int __devinit cpu_to_cpu_group(int cpu)
{
        return cpu;
}
#endif

static DEFINE_PER_CPU(struct sched_domain, phys_domains);
static struct sched_group sched_group_phys[NR_CPUS];
static int __devinit cpu_to_phys_group(int cpu)
{
#ifdef CONFIG_SCHED_SMT
        return first_cpu(cpu_sibling_map[cpu]);
#else
        return cpu;
#endif
}

#ifdef CONFIG_NUMA

static DEFINE_PER_CPU(struct sched_domain, node_domains);
static struct sched_group sched_group_nodes[MAX_NUMNODES];
static int __devinit cpu_to_node_group(int cpu)
{
        return cpu_to_node(cpu);
}
#endif

#if defined(CONFIG_SCHED_SMT) && defined(CONFIG_NUMA)
/*
 * The domains setup code relies on siblings not spanning
 * multiple nodes. Make sure the architecture has a proper
 * siblings map:
 */
static void check_sibling_maps(void)
{
        int i, j;

        for_each_online_cpu(i) {
                for_each_cpu_mask(j, cpu_sibling_map[i]) {
                        if (cpu_to_node(i) != cpu_to_node(j)) {
                                printk(KERN_INFO "warning: CPU %d siblings map "
                                        "to different node - isolating "
                                        "them.\n", i);
                                cpu_sibling_map[i] = cpumask_of_cpu(i);
                                break;
                        }
                }
        }
}
#endif

/*
 * Set up scheduler domains and groups.  Callers must hold the hotplug lock.
 */
static void __devinit arch_init_sched_domains(void)
{
        int i;
        cpumask_t cpu_default_map;

#if defined(CONFIG_SCHED_SMT) && defined(CONFIG_NUMA)
        check_sibling_maps();
#endif
        /*
         * Setup mask for cpus without special case scheduling requirements.
         * For now this just excludes isolated cpus, but could be used to
         * exclude other special cases in the future.
         */
        cpus_complement(cpu_default_map, cpu_isolated_map);
        cpus_and(cpu_default_map, cpu_default_map, cpu_online_map);

        /*
         * Set up domains. Isolated domains just stay on the dummy domain.
         */
        for_each_cpu_mask(i, cpu_default_map) {
                int group;
                struct sched_domain *sd = NULL, *p;
                cpumask_t nodemask = node_to_cpumask(cpu_to_node(i));

                cpus_and(nodemask, nodemask, cpu_default_map);

#ifdef CONFIG_NUMA
                sd = &per_cpu(node_domains, i);
                group = cpu_to_node_group(i);
                *sd = SD_NODE_INIT;
                sd->span = cpu_default_map;
                sd->groups = &sched_group_nodes[group];
#endif

                p = sd;
                sd = &per_cpu(phys_domains, i);
                group = cpu_to_phys_group(i);
                *sd = SD_CPU_INIT;
                sd->span = nodemask;
                sd->parent = p;
                sd->groups = &sched_group_phys[group];

#ifdef CONFIG_SCHED_SMT
                p = sd;
                sd = &per_cpu(cpu_domains, i);
                group = cpu_to_cpu_group(i);
                *sd = SD_SIBLING_INIT;
                sd->span = cpu_sibling_map[i];
                cpus_and(sd->span, sd->span, cpu_default_map);
                sd->parent = p;
                sd->groups = &sched_group_cpus[group];
#endif
        }

#ifdef CONFIG_SCHED_SMT
        /* Set up CPU (sibling) groups */
        for_each_online_cpu(i) {
                cpumask_t this_sibling_map = cpu_sibling_map[i];
                cpus_and(this_sibling_map, this_sibling_map, cpu_default_map);
                if (i != first_cpu(this_sibling_map))
                        continue;

                init_sched_build_groups(sched_group_cpus, this_sibling_map,
                                                &cpu_to_cpu_group);
        }
#endif

        /* Set up physical groups */
        for (i = 0; i < MAX_NUMNODES; i++) {
                cpumask_t nodemask = node_to_cpumask(i);

                cpus_and(nodemask, nodemask, cpu_default_map);
                if (cpus_empty(nodemask))
                        continue;

                init_sched_build_groups(sched_group_phys, nodemask,
                                                &cpu_to_phys_group);
        }

#ifdef CONFIG_NUMA
        /* Set up node groups */
        init_sched_build_groups(sched_group_nodes, cpu_default_map,
                                        &cpu_to_node_group);
#endif

        /* Calculate CPU power for physical packages and nodes */
        for_each_cpu_mask(i, cpu_default_map) {
                int power;
                struct sched_domain *sd;
#ifdef CONFIG_SCHED_SMT
                sd = &per_cpu(cpu_domains, i);
                power = SCHED_LOAD_SCALE;
                sd->groups->cpu_power = power;
#endif

                sd = &per_cpu(phys_domains, i);
                power = SCHED_LOAD_SCALE + SCHED_LOAD_SCALE *
                                (cpus_weight(sd->groups->cpumask)-1) / 10;
                sd->groups->cpu_power = power;

#ifdef CONFIG_NUMA
                if (i == first_cpu(sd->groups->cpumask)) {
                        /* Only add "power" once for each physical package. */
                        sd = &per_cpu(node_domains, i);
                        sd->groups->cpu_power += power;
                }
#endif
        }

        /* Attach the domains */
        for_each_online_cpu(i) {
                struct sched_domain *sd;
#ifdef CONFIG_SCHED_SMT
                sd = &per_cpu(cpu_domains, i);
#else
                sd = &per_cpu(phys_domains, i);
#endif
                cpu_attach_domain(sd, i);
        }
}

#ifdef CONFIG_HOTPLUG_CPU
static void __devinit arch_destroy_sched_domains(void)
{
        /* Do nothing: everything is statically allocated. */
}
#endif

#endif /* ARCH_HAS_SCHED_DOMAIN */

#define SCHED_DOMAIN_DEBUG
#ifdef SCHED_DOMAIN_DEBUG
static void sched_domain_debug(void)
{
        int i;

        for_each_online_cpu(i) {
                runqueue_t *rq = cpu_rq(i);
                struct sched_domain *sd;
                int level = 0;

                sd = rq->sd;

                printk(KERN_DEBUG "CPU%d:\n", i);

                do {
                        int j;
                        char str[NR_CPUS];
                        struct sched_group *group = sd->groups;
                        cpumask_t groupmask;

                        cpumask_scnprintf(str, NR_CPUS, sd->span);
                        cpus_clear(groupmask);

                        printk(KERN_DEBUG);
                        for (j = 0; j < level + 1; j++)
                                printk(" ");
                        printk("domain %d: ", level);

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

                        printk("span %s\n", str);

                        if (!cpu_isset(i, sd->span))
                                printk(KERN_DEBUG "ERROR domain->span does not contain CPU%d\n", i);
                        if (!cpu_isset(i, group->cpumask))
                                printk(KERN_DEBUG "ERROR domain->groups does not contain CPU%d\n", i);

                        printk(KERN_DEBUG);
                        for (j = 0; j < level + 2; j++)
                                printk(" ");
                        printk("groups:");
                        do {
                                if (!group) {
                                        printk(" ERROR: NULL");
                                        break;
                                }
                                
                                if (!group->cpu_power)
                                        printk(KERN_DEBUG "ERROR group->cpu_power not set\n");

                                if (!cpus_weight(group->cpumask))
                                        printk(" ERROR empty group:");

                                if (cpus_intersects(groupmask, group->cpumask))
                                        printk(" ERROR repeated CPUs:");

                                cpus_or(groupmask, groupmask, group->cpumask);

                                cpumask_scnprintf(str, NR_CPUS, group->cpumask);
                                printk(" %s", str);

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

                        if (!cpus_equal(sd->span, groupmask))
                                printk(KERN_DEBUG "ERROR groups don't span domain->span\n");

                        level++;
                        sd = sd->parent;

                        if (sd) {
                                if (!cpus_subset(groupmask, sd->span))
                                        printk(KERN_DEBUG "ERROR parent span is not a superset of domain->span\n");
                        }

                } while (sd);
        }
}
#else
#define sched_domain_debug() {}
#endif

/*
 * Initial dummy domain for early boot and for hotplug cpu. Being static,
 * it is initialized to zero, so all balancing flags are cleared which is
 * what we want.
 */
static struct sched_domain sched_domain_dummy;

#ifdef CONFIG_HOTPLUG_CPU
/*
 * Force a reinitialization of the sched domains hierarchy.  The domains
 * and groups cannot be updated in place without racing with the balancing
 * code, so we temporarily attach all running cpus to a "dummy" domain
 * which will prevent rebalancing while the sched domains are recalculated.
 */
static int update_sched_domains(struct notifier_block *nfb,
                                unsigned long action, void *hcpu)
{
        int i;

        switch (action) {
        case CPU_UP_PREPARE:
        case CPU_DOWN_PREPARE:
                for_each_online_cpu(i)
                        cpu_attach_domain(&sched_domain_dummy, i);
                arch_destroy_sched_domains();
                return NOTIFY_OK;

        case CPU_UP_CANCELED:
        case CPU_DOWN_FAILED:
        case CPU_ONLINE:
        case CPU_DEAD:
                /*
                 * Fall through and re-initialise the domains.
                 */
                break;
        default:
                return NOTIFY_DONE;
        }

        /* The hotplug lock is already held by cpu_up/cpu_down */
        arch_init_sched_domains();

        sched_domain_debug();

        return NOTIFY_OK;
}
#endif

void __init sched_init_smp(void)
{
        lock_cpu_hotplug();
        arch_init_sched_domains();
        sched_domain_debug();
        unlock_cpu_hotplug();
        /* XXX: Theoretical race here - CPU may be hotplugged now */
        hotcpu_notifier(update_sched_domains, 0);
}
#else
void __init sched_init_smp(void)
{
}
#endif /* CONFIG_SMP */

int in_sched_functions(unsigned long addr)
{
        /* Linker adds these: start and end of __sched functions */
        extern char __sched_text_start[], __sched_text_end[];
        return in_lock_functions(addr) ||
                (addr >= (unsigned long)__sched_text_start
                && addr < (unsigned long)__sched_text_end);
}

void __init sched_init(void)
{
        runqueue_t *rq;
        int i, j, k;

        for (i = 0; i < NR_CPUS; i++) {
                prio_array_t *array;

                rq = cpu_rq(i);
                spin_lock_init(&rq->lock);
                rq->active = rq->arrays;
                rq->expired = rq->arrays + 1;
                rq->best_expired_prio = MAX_PRIO;

#ifdef CONFIG_SMP
                rq->sd = &sched_domain_dummy;
                rq->cpu_load = 0;
                rq->active_balance = 0;
                rq->push_cpu = 0;
                rq->migration_thread = NULL;
                INIT_LIST_HEAD(&rq->migration_queue);
#endif
                atomic_set(&rq->nr_iowait, 0);

                for (j = 0; j < 2; j++) {
                        array = rq->arrays + j;
                        for (k = 0; k < MAX_PRIO; k++) {
                                INIT_LIST_HEAD(array->queue + k);
                                __clear_bit(k, array->bitmap);
                        }
                        // delimiter for bitsearch
                        __set_bit(MAX_PRIO, array->bitmap);
                }
        }

        /*
         * 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());
}

#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
void __might_sleep(char *file, int line)
{
#if defined(in_atomic)
        static unsigned long prev_jiffy;        /* ratelimiting */

        if ((in_atomic() || irqs_disabled()) &&
            system_state == SYSTEM_RUNNING) {
                if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
                        return;
                prev_jiffy = jiffies;
                printk(KERN_ERR "Debug: sleeping function called from invalid"
                                " context at %s:%d\n", file, line);
                printk("in_atomic():%d, irqs_disabled():%d\n",
                        in_atomic(), irqs_disabled());
                dump_stack();
        }
#endif
}
EXPORT_SYMBOL(__might_sleep);
#endif

#ifdef CONFIG_MAGIC_SYSRQ
void normalize_rt_tasks(void)
{
        struct task_struct *p;
        prio_array_t *array;
        unsigned long flags;
        runqueue_t *rq;

        read_lock_irq(&tasklist_lock);
        for_each_process (p) {
                if (!rt_task(p))
                        continue;

                rq = task_rq_lock(p, &flags);

                array = p->array;
                if (array)
                        deactivate_task(p, task_rq(p));
                __setscheduler(p, SCHED_NORMAL, 0);
                if (array) {
                        __activate_task(p, task_rq(p));
                        resched_task(rq->curr);
                }

                task_rq_unlock(rq, &flags);
        }
        read_unlock_irq(&tasklist_lock);
}

#endif /* CONFIG_MAGIC_SYSRQ */