sched: high-res preemption tick

[linux-2.6] / 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
 *  2007-04-15  Work begun on replacing all interactivity tuning with a
 *              fair scheduling design by Con Kolivas.
 *  2007-05-05  Load balancing (smp-nice) and other improvements
 *              by Peter Williams
 *  2007-05-06  Interactivity improvements to CFS by Mike Galbraith
 *  2007-07-01  Group scheduling enhancements by Srivatsa Vaddagiri
 *  2007-11-29  RT balancing improvements by Steven Rostedt, Gregory Haskins,
 *              Thomas Gleixner, Mike Kravetz
 */

#include <linux/mm.h>
#include <linux/module.h>
#include <linux/nmi.h>
#include <linux/init.h>
#include <linux/uaccess.h>
#include <linux/highmem.h>
#include <linux/smp_lock.h>
#include <asm/mmu_context.h>
#include <linux/interrupt.h>
#include <linux/capability.h>
#include <linux/completion.h>
#include <linux/kernel_stat.h>
#include <linux/debug_locks.h>
#include <linux/security.h>
#include <linux/notifier.h>
#include <linux/profile.h>
#include <linux/freezer.h>
#include <linux/vmalloc.h>
#include <linux/blkdev.h>
#include <linux/delay.h>
#include <linux/pid_namespace.h>
#include <linux/smp.h>
#include <linux/threads.h>
#include <linux/timer.h>
#include <linux/rcupdate.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/percpu.h>
#include <linux/kthread.h>
#include <linux/seq_file.h>
#include <linux/sysctl.h>
#include <linux/syscalls.h>
#include <linux/times.h>
#include <linux/tsacct_kern.h>
#include <linux/kprobes.h>
#include <linux/delayacct.h>
#include <linux/reciprocal_div.h>
#include <linux/unistd.h>
#include <linux/pagemap.h>
#include <linux/hrtimer.h>

#include <asm/tlb.h>
#include <asm/irq_regs.h>

/*
 * Scheduler clock - returns current time in nanosec units.
 * This is default implementation.
 * Architectures and sub-architectures can override this.
 */
unsigned long long __attribute__((weak)) sched_clock(void)
{
        return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ);
}

/*
 * 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))

/*
 * Helpers for converting nanosecond timing to jiffy resolution
 */
#define NS_TO_JIFFIES(TIME)     ((unsigned long)(TIME) / (NSEC_PER_SEC / HZ))

#define NICE_0_LOAD             SCHED_LOAD_SCALE
#define NICE_0_SHIFT            SCHED_LOAD_SHIFT

/*
 * These are the 'tuning knobs' of the scheduler:
 *
 * default timeslice is 100 msecs (used only for SCHED_RR tasks).
 * Timeslices get refilled after they expire.
 */
#define DEF_TIMESLICE           (100 * HZ / 1000)

#ifdef CONFIG_SMP
/*
 * Divide a load by a sched group cpu_power : (load / sg->__cpu_power)
 * Since cpu_power is a 'constant', we can use a reciprocal divide.
 */
static inline u32 sg_div_cpu_power(const struct sched_group *sg, u32 load)
{
        return reciprocal_divide(load, sg->reciprocal_cpu_power);
}

/*
 * Each time a sched group cpu_power is changed,
 * we must compute its reciprocal value
 */
static inline void sg_inc_cpu_power(struct sched_group *sg, u32 val)
{
        sg->__cpu_power += val;
        sg->reciprocal_cpu_power = reciprocal_value(sg->__cpu_power);
}
#endif

static inline int rt_policy(int policy)
{
        if (unlikely(policy == SCHED_FIFO) || unlikely(policy == SCHED_RR))
                return 1;
        return 0;
}

static inline int task_has_rt_policy(struct task_struct *p)
{
        return rt_policy(p->policy);
}

/*
 * This is the priority-queue data structure of the RT scheduling class:
 */
struct rt_prio_array {
        DECLARE_BITMAP(bitmap, MAX_RT_PRIO+1); /* include 1 bit for delimiter */
        struct list_head queue[MAX_RT_PRIO];
};

#ifdef CONFIG_FAIR_GROUP_SCHED

#include <linux/cgroup.h>

struct cfs_rq;

/* task group related information */
struct task_group {
#ifdef CONFIG_FAIR_CGROUP_SCHED
        struct cgroup_subsys_state css;
#endif
        /* schedulable entities of this group on each cpu */
        struct sched_entity **se;
        /* runqueue "owned" by this group on each cpu */
        struct cfs_rq **cfs_rq;

        /*
         * shares assigned to a task group governs how much of cpu bandwidth
         * is allocated to the group. The more shares a group has, the more is
         * the cpu bandwidth allocated to it.
         *
         * For ex, lets say that there are three task groups, A, B and C which
         * have been assigned shares 1000, 2000 and 3000 respectively. Then,
         * cpu bandwidth allocated by the scheduler to task groups A, B and C
         * should be:
         *
         *      Bw(A) = 1000/(1000+2000+3000) * 100 = 16.66%
         *      Bw(B) = 2000/(1000+2000+3000) * 100 = 33.33%
         *      Bw(C) = 3000/(1000+2000+3000) * 100 = 50%
         *
         * The weight assigned to a task group's schedulable entities on every
         * cpu (task_group.se[a_cpu]->load.weight) is derived from the task
         * group's shares. For ex: lets say that task group A has been
         * assigned shares of 1000 and there are two CPUs in a system. Then,
         *
         *  tg_A->se[0]->load.weight = tg_A->se[1]->load.weight = 1000;
         *
         * Note: It's not necessary that each of a task's group schedulable
         *       entity have the same weight on all CPUs. If the group
         *       has 2 of its tasks on CPU0 and 1 task on CPU1, then a
         *       better distribution of weight could be:
         *
         *      tg_A->se[0]->load.weight = 2/3 * 2000 = 1333
         *      tg_A->se[1]->load.weight = 1/2 * 2000 =  667
         *
         * rebalance_shares() is responsible for distributing the shares of a
         * task groups like this among the group's schedulable entities across
         * cpus.
         *
         */
        unsigned long shares;

        struct rcu_head rcu;
};

/* Default task group's sched entity on each cpu */
static DEFINE_PER_CPU(struct sched_entity, init_sched_entity);
/* Default task group's cfs_rq on each cpu */
static DEFINE_PER_CPU(struct cfs_rq, init_cfs_rq) ____cacheline_aligned_in_smp;

static struct sched_entity *init_sched_entity_p[NR_CPUS];
static struct cfs_rq *init_cfs_rq_p[NR_CPUS];

/* task_group_mutex serializes add/remove of task groups and also changes to
 * a task group's cpu shares.
 */
static DEFINE_MUTEX(task_group_mutex);

/* doms_cur_mutex serializes access to doms_cur[] array */
static DEFINE_MUTEX(doms_cur_mutex);

#ifdef CONFIG_SMP
/* kernel thread that runs rebalance_shares() periodically */
static struct task_struct *lb_monitor_task;
static int load_balance_monitor(void *unused);
#endif

static void set_se_shares(struct sched_entity *se, unsigned long shares);

/* Default task group.
 *      Every task in system belong to this group at bootup.
 */
struct task_group init_task_group = {
        .se     = init_sched_entity_p,
        .cfs_rq = init_cfs_rq_p,
};

#ifdef CONFIG_FAIR_USER_SCHED
# define INIT_TASK_GROUP_LOAD   (2*NICE_0_LOAD)
#else
# define INIT_TASK_GROUP_LOAD   NICE_0_LOAD
#endif

#define MIN_GROUP_SHARES        2

static int init_task_group_load = INIT_TASK_GROUP_LOAD;

/* return group to which a task belongs */
static inline struct task_group *task_group(struct task_struct *p)
{
        struct task_group *tg;

#ifdef CONFIG_FAIR_USER_SCHED
        tg = p->user->tg;
#elif defined(CONFIG_FAIR_CGROUP_SCHED)
        tg = container_of(task_subsys_state(p, cpu_cgroup_subsys_id),
                                struct task_group, css);
#else
        tg = &init_task_group;
#endif
        return tg;
}

/* Change a task's cfs_rq and parent entity if it moves across CPUs/groups */
static inline void set_task_cfs_rq(struct task_struct *p, unsigned int cpu)
{
        p->se.cfs_rq = task_group(p)->cfs_rq[cpu];
        p->se.parent = task_group(p)->se[cpu];
}

static inline void lock_task_group_list(void)
{
        mutex_lock(&task_group_mutex);
}

static inline void unlock_task_group_list(void)
{
        mutex_unlock(&task_group_mutex);
}

static inline void lock_doms_cur(void)
{
        mutex_lock(&doms_cur_mutex);
}

static inline void unlock_doms_cur(void)
{
        mutex_unlock(&doms_cur_mutex);
}

#else

static inline void set_task_cfs_rq(struct task_struct *p, unsigned int cpu) { }
static inline void lock_task_group_list(void) { }
static inline void unlock_task_group_list(void) { }
static inline void lock_doms_cur(void) { }
static inline void unlock_doms_cur(void) { }

#endif  /* CONFIG_FAIR_GROUP_SCHED */

/* CFS-related fields in a runqueue */
struct cfs_rq {
        struct load_weight load;
        unsigned long nr_running;

        u64 exec_clock;
        u64 min_vruntime;

        struct rb_root tasks_timeline;
        struct rb_node *rb_leftmost;
        struct rb_node *rb_load_balance_curr;
        /* 'curr' points to currently running entity on this cfs_rq.
         * It is set to NULL otherwise (i.e when none are currently running).
         */
        struct sched_entity *curr;

        unsigned long nr_spread_over;

#ifdef CONFIG_FAIR_GROUP_SCHED
        struct rq *rq;  /* cpu runqueue to which this cfs_rq is attached */

        /*
         * leaf cfs_rqs are those that hold tasks (lowest schedulable entity in
         * a hierarchy). Non-leaf lrqs hold other higher schedulable entities
         * (like users, containers etc.)
         *
         * leaf_cfs_rq_list ties together list of leaf cfs_rq's in a cpu. This
         * list is used during load balance.
         */
        struct list_head leaf_cfs_rq_list;
        struct task_group *tg;  /* group that "owns" this runqueue */
#endif
};

/* Real-Time classes' related field in a runqueue: */
struct rt_rq {
        struct rt_prio_array active;
        int rt_load_balance_idx;
        struct list_head *rt_load_balance_head, *rt_load_balance_curr;
        unsigned long rt_nr_running;
        unsigned long rt_nr_migratory;
        /* highest queued rt task prio */
        int highest_prio;
        int overloaded;
};

#ifdef CONFIG_SMP

/*
 * We add the notion of a root-domain which will be used to define per-domain
 * variables. Each exclusive cpuset essentially defines an island domain by
 * fully partitioning the member cpus from any other cpuset. Whenever a new
 * exclusive cpuset is created, we also create and attach a new root-domain
 * object.
 *
 */
struct root_domain {
        atomic_t refcount;
        cpumask_t span;
        cpumask_t online;

        /*
         * The "RT overload" flag: it gets set if a CPU has more than
         * one runnable RT task.
         */
        cpumask_t rto_mask;
        atomic_t rto_count;
};

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

#endif

/*
 * 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 rq {
        /* runqueue lock: */
        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;
        #define CPU_LOAD_IDX_MAX 5
        unsigned long cpu_load[CPU_LOAD_IDX_MAX];
        unsigned char idle_at_tick;
#ifdef CONFIG_NO_HZ
        unsigned char in_nohz_recently;
#endif
        /* capture load from *all* tasks on this cpu: */
        struct load_weight load;
        unsigned long nr_load_updates;
        u64 nr_switches;

        struct cfs_rq cfs;
#ifdef CONFIG_FAIR_GROUP_SCHED
        /* list of leaf cfs_rq on this cpu: */
        struct list_head leaf_cfs_rq_list;
#endif
        struct rt_rq rt;

        /*
         * 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;

        struct task_struct *curr, *idle;
        unsigned long next_balance;
        struct mm_struct *prev_mm;

        u64 clock, prev_clock_raw;
        s64 clock_max_delta;

        unsigned int clock_warps, clock_overflows;
        u64 idle_clock;
        unsigned int clock_deep_idle_events;
        u64 tick_timestamp;

        atomic_t nr_iowait;

#ifdef CONFIG_SMP
        struct root_domain *rd;
        struct sched_domain *sd;

        /* For active balancing */
        int active_balance;
        int push_cpu;
        /* cpu of this runqueue: */
        int cpu;

        struct task_struct *migration_thread;
        struct list_head migration_queue;
#endif

#ifdef CONFIG_SCHED_HRTICK
        unsigned long hrtick_flags;
        ktime_t hrtick_expire;
        struct hrtimer hrtick_timer;
#endif

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

        /* sys_sched_yield() stats */
        unsigned int yld_exp_empty;
        unsigned int yld_act_empty;
        unsigned int yld_both_empty;
        unsigned int yld_count;

        /* schedule() stats */
        unsigned int sched_switch;
        unsigned int sched_count;
        unsigned int sched_goidle;

        /* try_to_wake_up() stats */
        unsigned int ttwu_count;
        unsigned int ttwu_local;

        /* BKL stats */
        unsigned int bkl_count;
#endif
        struct lock_class_key rq_lock_key;
};

static DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);

static inline void check_preempt_curr(struct rq *rq, struct task_struct *p)
{
        rq->curr->sched_class->check_preempt_curr(rq, p);
}

static inline int cpu_of(struct rq *rq)
{
#ifdef CONFIG_SMP
        return rq->cpu;
#else
        return 0;
#endif
}

/*
 * Update the per-runqueue clock, as finegrained as the platform can give
 * us, but without assuming monotonicity, etc.:
 */
static void __update_rq_clock(struct rq *rq)
{
        u64 prev_raw = rq->prev_clock_raw;
        u64 now = sched_clock();
        s64 delta = now - prev_raw;
        u64 clock = rq->clock;

#ifdef CONFIG_SCHED_DEBUG
        WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
#endif
        /*
         * Protect against sched_clock() occasionally going backwards:
         */
        if (unlikely(delta < 0)) {
                clock++;
                rq->clock_warps++;
        } else {
                /*
                 * Catch too large forward jumps too:
                 */
                if (unlikely(clock + delta > rq->tick_timestamp + TICK_NSEC)) {
                        if (clock < rq->tick_timestamp + TICK_NSEC)
                                clock = rq->tick_timestamp + TICK_NSEC;
                        else
                                clock++;
                        rq->clock_overflows++;
                } else {
                        if (unlikely(delta > rq->clock_max_delta))
                                rq->clock_max_delta = delta;
                        clock += delta;
                }
        }

        rq->prev_clock_raw = now;
        rq->clock = clock;
}

static void update_rq_clock(struct rq *rq)
{
        if (likely(smp_processor_id() == cpu_of(rq)))
                __update_rq_clock(rq);
}

/*
 * The domain tree (rq->sd) is protected by RCU's quiescent state transition.
 * See detach_destroy_domains: synchronize_sched for details.
 *
 * The domain tree of any CPU may only be accessed from within
 * preempt-disabled sections.
 */
#define for_each_domain(cpu, __sd) \
        for (__sd = rcu_dereference(cpu_rq(cpu)->sd); __sd; __sd = __sd->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)

/*
 * Tunables that become constants when CONFIG_SCHED_DEBUG is off:
 */
#ifdef CONFIG_SCHED_DEBUG
# define const_debug __read_mostly
#else
# define const_debug static const
#endif

/*
 * Debugging: various feature bits
 */
enum {
        SCHED_FEAT_NEW_FAIR_SLEEPERS    = 1,
        SCHED_FEAT_WAKEUP_PREEMPT       = 2,
        SCHED_FEAT_START_DEBIT          = 4,
        SCHED_FEAT_TREE_AVG             = 8,
        SCHED_FEAT_APPROX_AVG           = 16,
        SCHED_FEAT_HRTICK               = 32,
        SCHED_FEAT_DOUBLE_TICK          = 64,
};

const_debug unsigned int sysctl_sched_features =
                SCHED_FEAT_NEW_FAIR_SLEEPERS    * 1 |
                SCHED_FEAT_WAKEUP_PREEMPT       * 1 |
                SCHED_FEAT_START_DEBIT          * 1 |
                SCHED_FEAT_TREE_AVG             * 0 |
                SCHED_FEAT_APPROX_AVG           * 0 |
                SCHED_FEAT_HRTICK               * 1 |
                SCHED_FEAT_DOUBLE_TICK          * 0;

#define sched_feat(x) (sysctl_sched_features & SCHED_FEAT_##x)

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

/*
 * For kernel-internal use: high-speed (but slightly incorrect) per-cpu
 * clock constructed from sched_clock():
 */
unsigned long long cpu_clock(int cpu)
{
        unsigned long long now;
        unsigned long flags;
        struct rq *rq;

        local_irq_save(flags);
        rq = cpu_rq(cpu);
        /*
         * Only call sched_clock() if the scheduler has already been
         * initialized (some code might call cpu_clock() very early):
         */
        if (rq->idle)
                update_rq_clock(rq);
        now = rq->clock;
        local_irq_restore(flags);

        return now;
}
EXPORT_SYMBOL_GPL(cpu_clock);

#ifndef prepare_arch_switch
# define prepare_arch_switch(next)      do { } while (0)
#endif
#ifndef finish_arch_switch
# define finish_arch_switch(prev)       do { } while (0)
#endif

static inline int task_current(struct rq *rq, struct task_struct *p)
{
        return rq->curr == p;
}

#ifndef __ARCH_WANT_UNLOCKED_CTXSW
static inline int task_running(struct rq *rq, struct task_struct *p)
{
        return task_current(rq, p);
}

static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
{
}

static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
{
#ifdef CONFIG_DEBUG_SPINLOCK
        /* this is a valid case when another task releases the spinlock */
        rq->lock.owner = current;
#endif
        /*
         * If we are tracking spinlock dependencies then we have to
         * fix up the runqueue lock - which gets 'carried over' from
         * prev into current:
         */
        spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_);

        spin_unlock_irq(&rq->lock);
}

#else /* __ARCH_WANT_UNLOCKED_CTXSW */
static inline int task_running(struct rq *rq, struct task_struct *p)
{
#ifdef CONFIG_SMP
        return p->oncpu;
#else
        return task_current(rq, p);
#endif
}

static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
{
#ifdef CONFIG_SMP
        /*
         * We can optimise this out completely for !SMP, because the
         * SMP rebalancing from interrupt is the only thing that cares
         * here.
         */
        next->oncpu = 1;
#endif
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
        spin_unlock_irq(&rq->lock);
#else
        spin_unlock(&rq->lock);
#endif
}

static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
{
#ifdef CONFIG_SMP
        /*
         * After ->oncpu is cleared, the task can be moved to a different CPU.
         * We must ensure this doesn't happen until the switch is completely
         * finished.
         */
        smp_wmb();
        prev->oncpu = 0;
#endif
#ifndef __ARCH_WANT_INTERRUPTS_ON_CTXSW
        local_irq_enable();
#endif
}
#endif /* __ARCH_WANT_UNLOCKED_CTXSW */

/*
 * __task_rq_lock - lock the runqueue a given task resides on.
 * Must be called interrupts disabled.
 */
static inline struct rq *__task_rq_lock(struct task_struct *p)
        __acquires(rq->lock)
{
        for (;;) {
                struct rq *rq = task_rq(p);
                spin_lock(&rq->lock);
                if (likely(rq == task_rq(p)))
                        return rq;
                spin_unlock(&rq->lock);
        }
}

/*
 * 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 struct rq *task_rq_lock(struct task_struct *p, unsigned long *flags)
        __acquires(rq->lock)
{
        struct rq *rq;

        for (;;) {
                local_irq_save(*flags);
                rq = task_rq(p);
                spin_lock(&rq->lock);
                if (likely(rq == task_rq(p)))
                        return rq;
                spin_unlock_irqrestore(&rq->lock, *flags);
        }
}

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

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

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

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

        return rq;
}

/*
 * We are going deep-idle (irqs are disabled):
 */
void sched_clock_idle_sleep_event(void)
{
        struct rq *rq = cpu_rq(smp_processor_id());

        spin_lock(&rq->lock);
        __update_rq_clock(rq);
        spin_unlock(&rq->lock);
        rq->clock_deep_idle_events++;
}
EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event);

/*
 * We just idled delta nanoseconds (called with irqs disabled):
 */
void sched_clock_idle_wakeup_event(u64 delta_ns)
{
        struct rq *rq = cpu_rq(smp_processor_id());
        u64 now = sched_clock();

        touch_softlockup_watchdog();
        rq->idle_clock += delta_ns;
        /*
         * Override the previous timestamp and ignore all
         * sched_clock() deltas that occured while we idled,
         * and use the PM-provided delta_ns to advance the
         * rq clock:
         */
        spin_lock(&rq->lock);
        rq->prev_clock_raw = now;
        rq->clock += delta_ns;
        spin_unlock(&rq->lock);
}
EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);

static void __resched_task(struct task_struct *p, int tif_bit);

static inline void resched_task(struct task_struct *p)
{
        __resched_task(p, TIF_NEED_RESCHED);
}

#ifdef CONFIG_SCHED_HRTICK
/*
 * Use HR-timers to deliver accurate preemption points.
 *
 * Its all a bit involved since we cannot program an hrt while holding the
 * rq->lock. So what we do is store a state in in rq->hrtick_* and ask for a
 * reschedule event.
 *
 * When we get rescheduled we reprogram the hrtick_timer outside of the
 * rq->lock.
 */
static inline void resched_hrt(struct task_struct *p)
{
        __resched_task(p, TIF_HRTICK_RESCHED);
}

static inline void resched_rq(struct rq *rq)
{
        unsigned long flags;

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

enum {
        HRTICK_SET,             /* re-programm hrtick_timer */
        HRTICK_RESET,           /* not a new slice */
};

/*
 * Use hrtick when:
 *  - enabled by features
 *  - hrtimer is actually high res
 */
static inline int hrtick_enabled(struct rq *rq)
{
        if (!sched_feat(HRTICK))
                return 0;
        return hrtimer_is_hres_active(&rq->hrtick_timer);
}

/*
 * Called to set the hrtick timer state.
 *
 * called with rq->lock held and irqs disabled
 */
static void hrtick_start(struct rq *rq, u64 delay, int reset)
{
        assert_spin_locked(&rq->lock);

        /*
         * preempt at: now + delay
         */
        rq->hrtick_expire =
                ktime_add_ns(rq->hrtick_timer.base->get_time(), delay);
        /*
         * indicate we need to program the timer
         */
        __set_bit(HRTICK_SET, &rq->hrtick_flags);
        if (reset)
                __set_bit(HRTICK_RESET, &rq->hrtick_flags);

        /*
         * New slices are called from the schedule path and don't need a
         * forced reschedule.
         */
        if (reset)
                resched_hrt(rq->curr);
}

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

/*
 * Update the timer from the possible pending state.
 */
static void hrtick_set(struct rq *rq)
{
        ktime_t time;
        int set, reset;
        unsigned long flags;

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

        spin_lock_irqsave(&rq->lock, flags);
        set = __test_and_clear_bit(HRTICK_SET, &rq->hrtick_flags);
        reset = __test_and_clear_bit(HRTICK_RESET, &rq->hrtick_flags);
        time = rq->hrtick_expire;
        clear_thread_flag(TIF_HRTICK_RESCHED);
        spin_unlock_irqrestore(&rq->lock, flags);

        if (set) {
                hrtimer_start(&rq->hrtick_timer, time, HRTIMER_MODE_ABS);
                if (reset && !hrtimer_active(&rq->hrtick_timer))
                        resched_rq(rq);
        } else
                hrtick_clear(rq);
}

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

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

        spin_lock(&rq->lock);
        __update_rq_clock(rq);
        rq->curr->sched_class->task_tick(rq, rq->curr, 1);
        spin_unlock(&rq->lock);

        return HRTIMER_NORESTART;
}

static inline void init_rq_hrtick(struct rq *rq)
{
        rq->hrtick_flags = 0;
        hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
        rq->hrtick_timer.function = hrtick;
        rq->hrtick_timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ;
}

void hrtick_resched(void)
{
        struct rq *rq;
        unsigned long flags;

        if (!test_thread_flag(TIF_HRTICK_RESCHED))
                return;

        local_irq_save(flags);
        rq = cpu_rq(smp_processor_id());
        hrtick_set(rq);
        local_irq_restore(flags);
}
#else
static inline void hrtick_clear(struct rq *rq)
{
}

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

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

void hrtick_resched(void)
{
}
#endif

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

#ifndef tsk_is_polling
#define tsk_is_polling(t) test_tsk_thread_flag(t, TIF_POLLING_NRFLAG)
#endif

static void __resched_task(struct task_struct *p, int tif_bit)
{
        int cpu;

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

        if (unlikely(test_tsk_thread_flag(p, tif_bit)))
                return;

        set_tsk_thread_flag(p, tif_bit);

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

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

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

        if (!spin_trylock_irqsave(&rq->lock, flags))
                return;
        resched_task(cpu_curr(cpu));
        spin_unlock_irqrestore(&rq->lock, flags);
}
#else
static void __resched_task(struct task_struct *p, int tif_bit)
{
        assert_spin_locked(&task_rq(p)->lock);
        set_tsk_thread_flag(p, tif_bit);
}
#endif

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

#define WMULT_SHIFT     32

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

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

        if (unlikely(!lw->inv_weight))
                lw->inv_weight = (WMULT_CONST - lw->weight/2) / lw->weight + 1;

        tmp = (u64)delta_exec * weight;
        /*
         * Check whether we'd overflow the 64-bit multiplication:
         */
        if (unlikely(tmp > WMULT_CONST))
                tmp = SRR(SRR(tmp, WMULT_SHIFT/2) * lw->inv_weight,
                        WMULT_SHIFT/2);
        else
                tmp = SRR(tmp * lw->inv_weight, WMULT_SHIFT);

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

static inline unsigned long
calc_delta_fair(unsigned long delta_exec, struct load_weight *lw)
{
        return calc_delta_mine(delta_exec, NICE_0_LOAD, lw);
}

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

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

/*
 * To aid in avoiding the subversion of "niceness" due to uneven distribution
 * of tasks with abnormal "nice" values across CPUs the contribution that
 * each task makes to its run queue's load is weighted according to its
 * scheduling class and "nice" value. For SCHED_NORMAL tasks this is just a
 * scaled version of the new time slice allocation that they receive on time
 * slice expiry etc.
 */

#define WEIGHT_IDLEPRIO         2
#define WMULT_IDLEPRIO          (1 << 31)

/*
 * Nice levels are multiplicative, with a gentle 10% change for every
 * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
 * nice 1, it will get ~10% less CPU time than another CPU-bound task
 * that remained on nice 0.
 *
 * The "10% effect" is relative and cumulative: from _any_ nice level,
 * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
 * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
 * If a task goes up by ~10% and another task goes down by ~10% then
 * the relative distance between them is ~25%.)
 */
static const int prio_to_weight[40] = {
 /* -20 */     88761,     71755,     56483,     46273,     36291,
 /* -15 */     29154,     23254,     18705,     14949,     11916,
 /* -10 */      9548,      7620,      6100,      4904,      3906,
 /*  -5 */      3121,      2501,      1991,      1586,      1277,
 /*   0 */      1024,       820,       655,       526,       423,
 /*   5 */       335,       272,       215,       172,       137,
 /*  10 */       110,        87,        70,        56,        45,
 /*  15 */        36,        29,        23,        18,        15,
};

/*
 * Inverse (2^32/x) values of the prio_to_weight[] array, precalculated.
 *
 * In cases where the weight does not change often, we can use the
 * precalculated inverse to speed up arithmetics by turning divisions
 * into multiplications:
 */
static const u32 prio_to_wmult[40] = {
 /* -20 */     48388,     59856,     76040,     92818,    118348,
 /* -15 */    147320,    184698,    229616,    287308,    360437,
 /* -10 */    449829,    563644,    704093,    875809,   1099582,
 /*  -5 */   1376151,   1717300,   2157191,   2708050,   3363326,
 /*   0 */   4194304,   5237765,   6557202,   8165337,  10153587,
 /*   5 */  12820798,  15790321,  19976592,  24970740,  31350126,
 /*  10 */  39045157,  49367440,  61356676,  76695844,  95443717,
 /*  15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
};

static void activate_task(struct rq *rq, struct task_struct *p, int wakeup);

/*
 * runqueue iterator, to support SMP load-balancing between different
 * scheduling classes, without having to expose their internal data
 * structures to the load-balancing proper:
 */
struct rq_iterator {
        void *arg;
        struct task_struct *(*start)(void *);
        struct task_struct *(*next)(void *);
};

#ifdef CONFIG_SMP
static unsigned long
balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
              unsigned long max_load_move, struct sched_domain *sd,
              enum cpu_idle_type idle, int *all_pinned,
              int *this_best_prio, struct rq_iterator *iterator);

static int
iter_move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
                   struct sched_domain *sd, enum cpu_idle_type idle,
                   struct rq_iterator *iterator);
#endif

#ifdef CONFIG_CGROUP_CPUACCT
static void cpuacct_charge(struct task_struct *tsk, u64 cputime);
#else
static inline void cpuacct_charge(struct task_struct *tsk, u64 cputime) {}
#endif

static inline void inc_cpu_load(struct rq *rq, unsigned long load)
{
        update_load_add(&rq->load, load);
}

static inline void dec_cpu_load(struct rq *rq, unsigned long load)
{
        update_load_sub(&rq->load, load);
}

#ifdef CONFIG_SMP
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
static unsigned long cpu_avg_load_per_task(int cpu);
static int task_hot(struct task_struct *p, u64 now, struct sched_domain *sd);
#endif /* CONFIG_SMP */

#include "sched_stats.h"
#include "sched_idletask.c"
#include "sched_fair.c"
#include "sched_rt.c"
#ifdef CONFIG_SCHED_DEBUG
# include "sched_debug.c"
#endif

#define sched_class_highest (&rt_sched_class)

static void inc_nr_running(struct task_struct *p, struct rq *rq)
{
        rq->nr_running++;
}

static void dec_nr_running(struct task_struct *p, struct rq *rq)
{
        rq->nr_running--;
}

static void set_load_weight(struct task_struct *p)
{
        if (task_has_rt_policy(p)) {
                p->se.load.weight = prio_to_weight[0] * 2;
                p->se.load.inv_weight = prio_to_wmult[0] >> 1;
                return;
        }

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

        p->se.load.weight = prio_to_weight[p->static_prio - MAX_RT_PRIO];
        p->se.load.inv_weight = prio_to_wmult[p->static_prio - MAX_RT_PRIO];
}

static void enqueue_task(struct rq *rq, struct task_struct *p, int wakeup)
{
        sched_info_queued(p);
        p->sched_class->enqueue_task(rq, p, wakeup);
        p->se.on_rq = 1;
}

static void dequeue_task(struct rq *rq, struct task_struct *p, int sleep)
{
        p->sched_class->dequeue_task(rq, p, sleep);
        p->se.on_rq = 0;
}

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

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

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

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

/*
 * activate_task - move a task to the runqueue.
 */
static void activate_task(struct rq *rq, struct task_struct *p, int wakeup)
{
        if (p->state == TASK_UNINTERRUPTIBLE)
                rq->nr_uninterruptible--;

        enqueue_task(rq, p, wakeup);
        inc_nr_running(p, rq);
}

/*
 * deactivate_task - remove a task from the runqueue.
 */
static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep)
{
        if (p->state == TASK_UNINTERRUPTIBLE)
                rq->nr_uninterruptible++;

        dequeue_task(rq, p, sleep);
        dec_nr_running(p, rq);
}

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

/* Used instead of source_load when we know the type == 0 */
unsigned long weighted_cpuload(const int cpu)
{
        return cpu_rq(cpu)->load.weight;
}

static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)
{
        set_task_cfs_rq(p, cpu);
#ifdef CONFIG_SMP
        /*
         * After ->cpu is set up to a new value, task_rq_lock(p, ...) can be
         * successfuly executed on another CPU. We must ensure that updates of
         * per-task data have been completed by this moment.
         */
        smp_wmb();
        task_thread_info(p)->cpu = cpu;
#endif
}

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

#ifdef CONFIG_SMP

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

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

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

        delta = now - p->se.exec_start;

        return delta < (s64)sysctl_sched_migration_cost;
}


void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
{
        int old_cpu = task_cpu(p);
        struct rq *old_rq = cpu_rq(old_cpu), *new_rq = cpu_rq(new_cpu);
        struct cfs_rq *old_cfsrq = task_cfs_rq(p),
                      *new_cfsrq = cpu_cfs_rq(old_cfsrq, new_cpu);
        u64 clock_offset;

        clock_offset = old_rq->clock - new_rq->clock;

#ifdef CONFIG_SCHEDSTATS
        if (p->se.wait_start)
                p->se.wait_start -= clock_offset;
        if (p->se.sleep_start)
                p->se.sleep_start -= clock_offset;
        if (p->se.block_start)
                p->se.block_start -= clock_offset;
        if (old_cpu != new_cpu) {
                schedstat_inc(p, se.nr_migrations);
                if (task_hot(p, old_rq->clock, NULL))
                        schedstat_inc(p, se.nr_forced2_migrations);
        }
#endif
        p->se.vruntime -= old_cfsrq->min_vruntime -
                                         new_cfsrq->min_vruntime;

        __set_task_cpu(p, new_cpu);
}

struct migration_req {
        struct list_head list;

        struct task_struct *task;
        int dest_cpu;

        struct completion done;
};

/*
 * The task's runqueue lock must be held.
 * Returns true if you have to wait for migration thread.
 */
static int
migrate_task(struct task_struct *p, int dest_cpu, struct migration_req *req)
{
        struct rq *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->se.on_rq && !task_running(rq, p)) {
                set_task_cpu(p, dest_cpu);
                return 0;
        }

        init_completion(&req->done);
        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(struct task_struct *p)
{
        unsigned long flags;
        int running, on_rq;
        struct rq *rq;

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

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

                /*
                 * Ok, time to look more closely! We need the rq
                 * lock now, to be *sure*. If we're wrong, we'll
                 * just go back and repeat.
                 */
                rq = task_rq_lock(p, &flags);
                running = task_running(rq, p);
                on_rq = p->se.on_rq;
                task_rq_unlock(rq, &flags);

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

                /*
                 * It's not enough that it's not actively running,
                 * it must be off the runqueue _entirely_, and not
                 * preempted!
                 *
                 * So if it wa still runnable (but just not actively
                 * running right now), it's preempted, and we should
                 * yield - it could be a while.
                 */
                if (unlikely(on_rq)) {
                        schedule_timeout_uninterruptible(1);
                        continue;
                }

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

/***
 * kick_process - kick a running thread to enter/exit the kernel
 * @p: the to-be-kicked thread
 *
 * Cause a process which is running on another CPU to enter
 * kernel-mode, without any delay. (to get signals handled.)
 *
 * NOTE: this function doesnt have to take the runqueue lock,
 * because all it wants to ensure is that the remote task enters
 * the kernel. If the IPI races and the task has been migrated
 * to another CPU then no harm is done and the purpose has been
 * achieved as well.
 */
void kick_process(struct task_struct *p)
{
        int cpu;

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

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

        if (type == 0)
                return total;

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

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

        if (type == 0)
                return total;

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

/*
 * Return the average load per task on the cpu's run queue
 */
static unsigned long cpu_avg_load_per_task(int cpu)
{
        struct rq *rq = cpu_rq(cpu);
        unsigned long total = weighted_cpuload(cpu);
        unsigned long n = rq->nr_running;

        return n ? total / n : SCHED_LOAD_SCALE;
}

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

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

                /* Skip over this group if it has no CPUs allowed */
                if (!cpus_intersects(group->cpumask, p->cpus_allowed))
                        continue;

                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 = source_load(i, load_idx);
                        else
                                load = target_load(i, load_idx);

                        avg_load += load;
                }

                /* Adjust by relative CPU power of the group */
                avg_load = sg_div_cpu_power(group,
                                avg_load * SCHED_LOAD_SCALE);

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

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

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

        /* Traverse only the allowed CPUs */
        cpus_and(tmp, group->cpumask, p->cpus_allowed);

        for_each_cpu_mask(i, tmp) {
                load = weighted_cpuload(i);

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

        return idlest;
}

/*
 * sched_balance_self: balance the current task (running on cpu) in domains
 * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
 * SD_BALANCE_EXEC.
 *
 * Balance, ie. select the least loaded group.
 *
 * Returns the target CPU number, or the same CPU if no balancing is needed.
 *
 * preempt must be disabled.
 */
static int sched_balance_self(int cpu, int flag)
{
        struct task_struct *t = current;
        struct sched_domain *tmp, *sd = NULL;

        for_each_domain(cpu, tmp) {
                /*
                 * If power savings logic is enabled for a domain, stop there.
                 */
                if (tmp->flags & SD_POWERSAVINGS_BALANCE)
                        break;
                if (tmp->flags & flag)
                        sd = tmp;
        }

        while (sd) {
                cpumask_t span;
                struct sched_group *group;
                int new_cpu, weight;

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

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

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

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

        return cpu;
}

#endif /* CONFIG_SMP */

/***
 * 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(struct task_struct *p, unsigned int state, int sync)
{
        int cpu, orig_cpu, this_cpu, success = 0;
        unsigned long flags;
        long old_state;
        struct rq *rq;

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

        if (p->se.on_rq)
                goto out_running;

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

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

        cpu = p->sched_class->select_task_rq(p, sync);
        if (cpu != orig_cpu) {
                set_task_cpu(p, 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->se.on_rq)
                        goto out_running;

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

#ifdef CONFIG_SCHEDSTATS
        schedstat_inc(rq, ttwu_count);
        if (cpu == this_cpu)
                schedstat_inc(rq, ttwu_local);
        else {
                struct sched_domain *sd;
                for_each_domain(this_cpu, sd) {
                        if (cpu_isset(cpu, sd->span)) {
                                schedstat_inc(sd, ttwu_wake_remote);
                                break;
                        }
                }
        }
#endif

out_activate:
#endif /* CONFIG_SMP */
        schedstat_inc(p, se.nr_wakeups);
        if (sync)
                schedstat_inc(p, se.nr_wakeups_sync);
        if (orig_cpu != cpu)
                schedstat_inc(p, se.nr_wakeups_migrate);
        if (cpu == this_cpu)
                schedstat_inc(p, se.nr_wakeups_local);
        else
                schedstat_inc(p, se.nr_wakeups_remote);
        update_rq_clock(rq);
        activate_task(rq, p, 1);
        check_preempt_curr(rq, p);
        success = 1;

out_running:
        p->state = TASK_RUNNING;
#ifdef CONFIG_SMP
        if (p->sched_class->task_wake_up)
                p->sched_class->task_wake_up(rq, p);
#endif
out:
        task_rq_unlock(rq, &flags);

        return success;
}

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

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

#ifdef CONFIG_SCHEDSTATS
        p->se.wait_start                = 0;
        p->se.sum_sleep_runtime         = 0;
        p->se.sleep_start               = 0;
        p->se.block_start               = 0;
        p->se.sleep_max                 = 0;
        p->se.block_max                 = 0;
        p->se.exec_max                  = 0;
        p->se.slice_max                 = 0;
        p->se.wait_max                  = 0;
#endif

        INIT_LIST_HEAD(&p->rt.run_list);
        p->se.on_rq = 0;

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

        /*
         * 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;
}

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

        __sched_fork(p);

#ifdef CONFIG_SMP
        cpu = sched_balance_self(cpu, SD_BALANCE_FORK);
#endif
        set_task_cpu(p, cpu);

        /*
         * Make sure we do not leak PI boosting priority to the child:
         */
        p->prio = current->normal_prio;
        if (!rt_prio(p->prio))
                p->sched_class = &fair_sched_class;

#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
        if (likely(sched_info_on()))
                memset(&p->sched_info, 0, sizeof(p->sched_info));
#endif
#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
        p->oncpu = 0;
#endif
#ifdef CONFIG_PREEMPT
        /* Want to start with kernel preemption disabled. */
        task_thread_info(p)->preempt_count = 1;
#endif
        put_cpu();
}

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

        rq = task_rq_lock(p, &flags);
        BUG_ON(p->state != TASK_RUNNING);
        update_rq_clock(rq);

        p->prio = effective_prio(p);

        if (!p->sched_class->task_new || !current->se.on_rq) {
                activate_task(rq, p, 0);
        } else {
                /*
                 * Let the scheduling class do new task startup
                 * management (if any):
                 */
                p->sched_class->task_new(rq, p);
                inc_nr_running(p, rq);
        }
        check_preempt_curr(rq, p);
#ifdef CONFIG_SMP
        if (p->sched_class->task_wake_up)
                p->sched_class->task_wake_up(rq, p);
#endif
        task_rq_unlock(rq, &flags);
}

#ifdef CONFIG_PREEMPT_NOTIFIERS

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

/**
 * preempt_notifier_unregister - no longer interested in preemption notifications
 * @notifier: notifier struct to unregister
 *
 * This is safe to call from within a preemption notifier.
 */
void preempt_notifier_unregister(struct preempt_notifier *notifier)
{
        hlist_del(&notifier->link);
}
EXPORT_SYMBOL_GPL(preempt_notifier_unregister);

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

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

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

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

#else

static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
{
}

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

#endif

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

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

        rq->prev_mm = NULL;

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

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

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

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

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

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

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

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

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

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

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

        return sum;
}

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

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

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

        return sum;
}

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

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

        return sum;
}

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

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

        return sum;
}

unsigned long nr_active(void)
{
        unsigned long i, running = 0, uninterruptible = 0;

        for_each_online_cpu(i) {
                running += cpu_rq(i)->nr_running;
                uninterruptible += cpu_rq(i)->nr_uninterruptible;
        }

        if (unlikely((long)uninterruptible < 0))
                uninterruptible = 0;

        return running + uninterruptible;
}

/*
 * Update rq->cpu_load[] statistics. This function is usually called every
 * scheduler tick (TICK_NSEC).
 */
static void update_cpu_load(struct rq *this_rq)
{
        unsigned long this_load = this_rq->load.weight;
        int i, scale;

        this_rq->nr_load_updates++;

        /* Update our load: */
        for (i = 0, scale = 1; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
                unsigned long old_load, new_load;

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

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

#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(struct rq *rq1, struct rq *rq2)
        __acquires(rq1->lock)
        __acquires(rq2->lock)
{
        BUG_ON(!irqs_disabled());
        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);
                }
        }
        update_rq_clock(rq1);
        update_rq_clock(rq2);
}

/*
 * 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(struct rq *rq1, struct rq *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 int double_lock_balance(struct rq *this_rq, struct rq *busiest)
        __releases(this_rq->lock)
        __acquires(busiest->lock)
        __acquires(this_rq->lock)
{
        int ret = 0;

        if (unlikely(!irqs_disabled())) {
                /* printk() doesn't work good under rq->lock */
                spin_unlock(&this_rq->lock);
                BUG_ON(1);
        }
        if (unlikely(!spin_trylock(&busiest->lock))) {
                if (busiest < this_rq) {
                        spin_unlock(&this_rq->lock);
                        spin_lock(&busiest->lock);
                        spin_lock(&this_rq->lock);
                        ret = 1;
                } else
                        spin_lock(&busiest->lock);
        }
        return ret;
}

/*
 * 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(struct task_struct *p, int dest_cpu)
{
        struct migration_req req;
        unsigned long flags;
        struct rq *rq;

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

        /* 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 - execve() is a valuable balancing opportunity, because at
 * this point the task has the smallest effective memory and cache footprint.
 */
void sched_exec(void)
{
        int new_cpu, this_cpu = get_cpu();
        new_cpu = sched_balance_self(this_cpu, SD_BALANCE_EXEC);
        put_cpu();
        if (new_cpu != this_cpu)
                sched_migrate_task(current, new_cpu);
}

/*
 * pull_task - move a task from a remote runqueue to the local runqueue.
 * Both runqueues must be locked.
 */
static void pull_task(struct rq *src_rq, struct task_struct *p,
                      struct rq *this_rq, int this_cpu)
{
        deactivate_task(src_rq, p, 0);
        set_task_cpu(p, this_cpu);
        activate_task(this_rq, p, 0);
        /*
         * Note that idle threads have a prio of MAX_PRIO, for this test
         * to be always true for them.
         */
        check_preempt_curr(this_rq, p);
}

/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
                     struct sched_domain *sd, enum cpu_idle_type idle,
                     int *all_pinned)
{
        /*
         * 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 (!cpu_isset(this_cpu, p->cpus_allowed)) {
                schedstat_inc(p, se.nr_failed_migrations_affine);
                return 0;
        }
        *all_pinned = 0;

        if (task_running(rq, p)) {
                schedstat_inc(p, se.nr_failed_migrations_running);
                return 0;
        }

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

        if (!task_hot(p, rq->clock, sd) ||
                        sd->nr_balance_failed > sd->cache_nice_tries) {
#ifdef CONFIG_SCHEDSTATS
                if (task_hot(p, rq->clock, sd)) {
                        schedstat_inc(sd, lb_hot_gained[idle]);
                        schedstat_inc(p, se.nr_forced_migrations);
                }
#endif
                return 1;
        }

        if (task_hot(p, rq->clock, sd)) {
                schedstat_inc(p, se.nr_failed_migrations_hot);
                return 0;
        }
        return 1;
}

static unsigned long
balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
              unsigned long max_load_move, struct sched_domain *sd,
              enum cpu_idle_type idle, int *all_pinned,
              int *this_best_prio, struct rq_iterator *iterator)
{
        int loops = 0, pulled = 0, pinned = 0, skip_for_load;
        struct task_struct *p;
        long rem_load_move = max_load_move;

        if (max_load_move == 0)
                goto out;

        pinned = 1;

        /*
         * Start the load-balancing iterator:
         */
        p = iterator->start(iterator->arg);
next:
        if (!p || loops++ > sysctl_sched_nr_migrate)
                goto out;
        /*
         * To help distribute high priority tasks across CPUs we don't
         * skip a task if it will be the highest priority task (i.e. smallest
         * prio value) on its new queue regardless of its load weight
         */
        skip_for_load = (p->se.load.weight >> 1) > rem_load_move +
                                                         SCHED_LOAD_SCALE_FUZZ;
        if ((skip_for_load && p->prio >= *this_best_prio) ||
            !can_migrate_task(p, busiest, this_cpu, sd, idle, &pinned)) {
                p = iterator->next(iterator->arg);
                goto next;
        }

        pull_task(busiest, p, this_rq, this_cpu);
        pulled++;
        rem_load_move -= p->se.load.weight;

        /*
         * We only want to steal up to the prescribed amount of weighted load.
         */
        if (rem_load_move > 0) {
                if (p->prio < *this_best_prio)
                        *this_best_prio = p->prio;
                p = iterator->next(iterator->arg);
                goto next;
        }
out:
        /*
         * Right now, this is one of only two places pull_task() is called,
         * so we can safely collect pull_task() stats here rather than
         * inside pull_task().
         */
        schedstat_add(sd, lb_gained[idle], pulled);

        if (all_pinned)
                *all_pinned = pinned;

        return max_load_move - rem_load_move;
}

/*
 * move_tasks tries to move up to max_load_move weighted load from busiest to
 * this_rq, as part of a balancing operation within domain "sd".
 * Returns 1 if successful and 0 otherwise.
 *
 * Called with both runqueues locked.
 */
static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
                      unsigned long max_load_move,
                      struct sched_domain *sd, enum cpu_idle_type idle,
                      int *all_pinned)
{
        const struct sched_class *class = sched_class_highest;
        unsigned long total_load_moved = 0;
        int this_best_prio = this_rq->curr->prio;

        do {
                total_load_moved +=
                        class->load_balance(this_rq, this_cpu, busiest,
                                max_load_move - total_load_moved,
                                sd, idle, all_pinned, &this_best_prio);
                class = class->next;
        } while (class && max_load_move > total_load_moved);

        return total_load_moved > 0;
}

static int
iter_move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
                   struct sched_domain *sd, enum cpu_idle_type idle,
                   struct rq_iterator *iterator)
{
        struct task_struct *p = iterator->start(iterator->arg);
        int pinned = 0;

        while (p) {
                if (can_migrate_task(p, busiest, this_cpu, sd, idle, &pinned)) {
                        pull_task(busiest, p, this_rq, this_cpu);
                        /*
                         * Right now, this is only the second place pull_task()
                         * is called, so we can safely collect pull_task()
                         * stats here rather than inside pull_task().
                         */
                        schedstat_inc(sd, lb_gained[idle]);

                        return 1;
                }
                p = iterator->next(iterator->arg);
        }

        return 0;
}

/*
 * move_one_task tries to move exactly one task from busiest to this_rq, as
 * part of active balancing operations within "domain".
 * Returns 1 if successful and 0 otherwise.
 *
 * Called with both runqueues locked.
 */
static int move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
                         struct sched_domain *sd, enum cpu_idle_type idle)
{
        const struct sched_class *class;

        for (class = sched_class_highest; class; class = class->next)
                if (class->move_one_task(this_rq, this_cpu, busiest, sd, idle))
                        return 1;

        return 0;
}

/*
 * find_busiest_group finds and returns the busiest CPU group within the
 * domain. It calculates and returns the amount of weighted load 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 cpu_idle_type idle,
                   int *sd_idle, cpumask_t *cpus, int *balance)
{
        struct sched_group *busiest = NULL, *this = NULL, *group = sd->groups;
        unsigned long max_load, avg_load, total_load, this_load, total_pwr;
        unsigned long max_pull;
        unsigned long busiest_load_per_task, busiest_nr_running;
        unsigned long this_load_per_task, this_nr_running;
        int load_idx, group_imb = 0;
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
        int power_savings_balance = 1;
        unsigned long leader_nr_running = 0, min_load_per_task = 0;
        unsigned long min_nr_running = ULONG_MAX;
        struct sched_group *group_min = NULL, *group_leader = NULL;
#endif

        max_load = this_load = total_load = total_pwr = 0;
        busiest_load_per_task = busiest_nr_running = 0;
        this_load_per_task = this_nr_running = 0;
        if (idle == CPU_NOT_IDLE)
                load_idx = sd->busy_idx;
        else if (idle == CPU_NEWLY_IDLE)
                load_idx = sd->newidle_idx;
        else
                load_idx = sd->idle_idx;

        do {
                unsigned long load, group_capacity, max_cpu_load, min_cpu_load;
                int local_group;
                int i;
                int __group_imb = 0;
                unsigned int balance_cpu = -1, first_idle_cpu = 0;
                unsigned long sum_nr_running, sum_weighted_load;

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

                if (local_group)
                        balance_cpu = first_cpu(group->cpumask);

                /* Tally up the load of all CPUs in the group */
                sum_weighted_load = sum_nr_running = avg_load = 0;
                max_cpu_load = 0;
                min_cpu_load = ~0UL;

                for_each_cpu_mask(i, group->cpumask) {
                        struct rq *rq;

                        if (!cpu_isset(i, *cpus))
                                continue;

                        rq = cpu_rq(i);

                        if (*sd_idle && rq->nr_running)
                                *sd_idle = 0;

                        /* Bias balancing toward cpus of our domain */
                        if (local_group) {
                                if (idle_cpu(i) && !first_idle_cpu) {
                                        first_idle_cpu = 1;
                                        balance_cpu = i;
                                }

                                load = target_load(i, load_idx);
                        } else {
                                load = source_load(i, load_idx);
                                if (load > max_cpu_load)
                                        max_cpu_load = load;
                                if (min_cpu_load > load)
                                        min_cpu_load = load;
                        }

                        avg_load += load;
                        sum_nr_running += rq->nr_running;
                        sum_weighted_load += weighted_cpuload(i);
                }

                /*
                 * First idle cpu or the first cpu(busiest) in this sched group
                 * is eligible for doing load balancing at this and above
                 * domains. In the newly idle case, we will allow all the cpu's
                 * to do the newly idle load balance.
                 */
                if (idle != CPU_NEWLY_IDLE && local_group &&
                    balance_cpu != this_cpu && balance) {
                        *balance = 0;
                        goto ret;
                }

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

                /* Adjust by relative CPU power of the group */
                avg_load = sg_div_cpu_power(group,
                                avg_load * SCHED_LOAD_SCALE);

                if ((max_cpu_load - min_cpu_load) > SCHED_LOAD_SCALE)
                        __group_imb = 1;

                group_capacity = group->__cpu_power / SCHED_LOAD_SCALE;

                if (local_group) {
                        this_load = avg_load;
                        this = group;
                        this_nr_running = sum_nr_running;
                        this_load_per_task = sum_weighted_load;
                } else if (avg_load > max_load &&
                           (sum_nr_running > group_capacity || __group_imb)) {
                        max_load = avg_load;
                        busiest = group;
                        busiest_nr_running = sum_nr_running;
                        busiest_load_per_task = sum_weighted_load;
                        group_imb = __group_imb;
                }

#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
                /*
                 * Busy processors will not participate in power savings
                 * balance.
                 */
                if (idle == CPU_NOT_IDLE ||
                                !(sd->flags & SD_POWERSAVINGS_BALANCE))
                        goto group_next;

                /*
                 * If the local group is idle or completely loaded
                 * no need to do power savings balance at this domain
                 */
                if (local_group && (this_nr_running >= group_capacity ||
                                    !this_nr_running))
                        power_savings_balance = 0;

                /*
                 * If a group is already running at full capacity or idle,
                 * don't include that group in power savings calculations
                 */
                if (!power_savings_balance || sum_nr_running >= group_capacity
                    || !sum_nr_running)
                        goto group_next;

                /*
                 * Calculate the group which has the least non-idle load.
                 * This is the group from where we need to pick up the load
                 * for saving power
                 */
                if ((sum_nr_running < min_nr_running) ||
                    (sum_nr_running == min_nr_running &&
                     first_cpu(group->cpumask) <
                     first_cpu(group_min->cpumask))) {
                        group_min = group;
                        min_nr_running = sum_nr_running;
                        min_load_per_task = sum_weighted_load /
                                                sum_nr_running;
                }

                /*
                 * Calculate the group which is almost near its
                 * capacity but still has some space to pick up some load
                 * from other group and save more power
                 */
                if (sum_nr_running <= group_capacity - 1) {
                        if (sum_nr_running > leader_nr_running ||
                            (sum_nr_running == leader_nr_running &&
                             first_cpu(group->cpumask) >
                              first_cpu(group_leader->cpumask))) {
                                group_leader = group;
                                leader_nr_running = sum_nr_running;
                        }
                }
group_next:
#endif
                group = group->next;
        } while (group != sd->groups);

        if (!busiest || this_load >= max_load || busiest_nr_running == 0)
                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;

        busiest_load_per_task /= busiest_nr_running;
        if (group_imb)
                busiest_load_per_task = min(busiest_load_per_task, avg_load);

        /*
         * 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.
         */
        if (max_load <= busiest_load_per_task)
                goto out_balanced;

        /*
         * In the presence of smp nice balancing, certain scenarios can have
         * max load less than avg load(as we skip the groups at or below
         * its cpu_power, while calculating max_load..)
         */
        if (max_load < avg_load) {
                *imbalance = 0;
                goto small_imbalance;
        }

        /* Don't want to pull so many tasks that a group would go idle */
        max_pull = min(max_load - avg_load, max_load - busiest_load_per_task);

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

        /*
         * if *imbalance is less than the average load per runnable task
         * there is no gaurantee that any tasks will be moved so we'll have
         * a think about bumping its value to force at least one task to be
         * moved
         */
        if (*imbalance < busiest_load_per_task) {
                unsigned long tmp, pwr_now, pwr_move;
                unsigned int imbn;

small_imbalance:
                pwr_move = pwr_now = 0;
                imbn = 2;
                if (this_nr_running) {
                        this_load_per_task /= this_nr_running;
                        if (busiest_load_per_task > this_load_per_task)
                                imbn = 1;
                } else
                        this_load_per_task = SCHED_LOAD_SCALE;

                if (max_load - this_load + SCHED_LOAD_SCALE_FUZZ >=
                                        busiest_load_per_task * imbn) {
                        *imbalance = busiest_load_per_task;
                        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(busiest_load_per_task, max_load);
                pwr_now += this->__cpu_power *
                                min(this_load_per_task, this_load);
                pwr_now /= SCHED_LOAD_SCALE;

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

                /* Amount of load we'd add */
                if (max_load * busiest->__cpu_power <
                                busiest_load_per_task * SCHED_LOAD_SCALE)
                        tmp = sg_div_cpu_power(this,
                                        max_load * busiest->__cpu_power);
                else
                        tmp = sg_div_cpu_power(this,
                                busiest_load_per_task * SCHED_LOAD_SCALE);
                pwr_move += this->__cpu_power *
                                min(this_load_per_task, this_load + tmp);
                pwr_move /= SCHED_LOAD_SCALE;

                /* Move if we gain throughput */
                if (pwr_move > pwr_now)
                        *imbalance = busiest_load_per_task;
        }

        return busiest;

out_balanced:
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
        if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
                goto ret;

        if (this == group_leader && group_leader != group_min) {
                *imbalance = min_load_per_task;
                return group_min;
        }
#endif
ret:
        *imbalance = 0;
        return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
static struct rq *
find_busiest_queue(struct sched_group *group, enum cpu_idle_type idle,
                   unsigned long imbalance, cpumask_t *cpus)
{
        struct rq *busiest = NULL, *rq;
        unsigned long max_load = 0;
        int i;

        for_each_cpu_mask(i, group->cpumask) {
                unsigned long wl;

                if (!cpu_isset(i, *cpus))
                        continue;

                rq = cpu_rq(i);
                wl = weighted_cpuload(i);

                if (rq->nr_running == 1 && wl > imbalance)
                        continue;

                if (wl > max_load) {
                        max_load = wl;
                        busiest = rq;
                }
        }

        return busiest;
}

/*
 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
 * so long as it is large enough.
 */
#define MAX_PINNED_INTERVAL     512

/*
 * Check this_cpu to ensure it is balanced within domain. Attempt to move
 * tasks if there is an imbalance.
 */
static int load_balance(int this_cpu, struct rq *this_rq,
                        struct sched_domain *sd, enum cpu_idle_type idle,
                        int *balance)
{
        int ld_moved, all_pinned = 0, active_balance = 0, sd_idle = 0;
        struct sched_group *group;
        unsigned long imbalance;
        struct rq *busiest;
        cpumask_t cpus = CPU_MASK_ALL;
        unsigned long flags;

        /*
         * When power savings policy is enabled for the parent domain, idle
         * sibling can pick up load irrespective of busy siblings. In this case,
         * let the state of idle sibling percolate up as CPU_IDLE, instead of
         * portraying it as CPU_NOT_IDLE.
         */
        if (idle != CPU_NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER &&
            !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
                sd_idle = 1;

        schedstat_inc(sd, lb_count[idle]);

redo:
        group = find_busiest_group(sd, this_cpu, &imbalance, idle, &sd_idle,
                                   &cpus, balance);

        if (*balance == 0)
                goto out_balanced;

        if (!group) {
                schedstat_inc(sd, lb_nobusyg[idle]);
                goto out_balanced;
        }

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

        BUG_ON(busiest == this_rq);

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

        ld_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. ld_moved simply stays zero, so it is
                 * correctly treated as an imbalance.
                 */
                local_irq_save(flags);
                double_rq_lock(this_rq, busiest);
                ld_moved = move_tasks(this_rq, this_cpu, busiest,
                                      imbalance, sd, idle, &all_pinned);
                double_rq_unlock(this_rq, busiest);
                local_irq_restore(flags);

                /*
                 * some other cpu did the load balance for us.
                 */
                if (ld_moved && this_cpu != smp_processor_id())
                        resched_cpu(this_cpu);

                /* All tasks on this runqueue were pinned by CPU affinity */
                if (unlikely(all_pinned)) {
                        cpu_clear(cpu_of(busiest), cpus);
                        if (!cpus_empty(cpus))
                                goto redo;
                        goto out_balanced;
                }
        }

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

                if (unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2)) {

                        spin_lock_irqsave(&busiest->lock, flags);

                        /* don't kick the migration_thread, if the curr
                         * task on busiest cpu can't be moved to this_cpu
                         */
                        if (!cpu_isset(this_cpu, busiest->curr->cpus_allowed)) {
                                spin_unlock_irqrestore(&busiest->lock, flags);
                                all_pinned = 1;
                                goto out_one_pinned;
                        }

                        if (!busiest->active_balance) {
                                busiest->active_balance = 1;
                                busiest->push_cpu = this_cpu;
                                active_balance = 1;
                        }
                        spin_unlock_irqrestore(&busiest->lock, flags);
                        if (active_balance)
                                wake_up_process(busiest->migration_thread);

                        /*
                         * We've kicked active balancing, reset the failure
                         * counter.
                         */
                        sd->nr_balance_failed = sd->cache_nice_tries+1;
                }
        } else
                sd->nr_balance_failed = 0;

        if (likely(!active_balance)) {
                /* We were unbalanced, so reset the balancing interval */
                sd->balance_interval = sd->min_interval;
        } else {
                /*
                 * If we've begun active balancing, start to back off. This
                 * case may not be covered by the all_pinned logic if there
                 * is only 1 task on the busy runqueue (because we don't call
                 * move_tasks).
                 */
                if (sd->balance_interval < sd->max_interval)
                        sd->balance_interval *= 2;
        }

        if (!ld_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
            !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
                return -1;
        return ld_moved;

out_balanced:
        schedstat_inc(sd, lb_balanced[idle]);

        sd->nr_balance_failed = 0;

out_one_pinned:
        /* tune up the balancing interval */
        if ((all_pinned && sd->balance_interval < MAX_PINNED_INTERVAL) ||
                        (sd->balance_interval < sd->max_interval))
                sd->balance_interval *= 2;

        if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
            !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
                return -1;
        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 (CPU_NEWLY_IDLE).
 * this_rq is locked.
 */
static int
load_balance_newidle(int this_cpu, struct rq *this_rq, struct sched_domain *sd)
{
        struct sched_group *group;
        struct rq *busiest = NULL;
        unsigned long imbalance;
        int ld_moved = 0;
        int sd_idle = 0;
        int all_pinned = 0;
        cpumask_t cpus = CPU_MASK_ALL;

        /*
         * When power savings policy is enabled for the parent domain, idle
         * sibling can pick up load irrespective of busy siblings. In this case,
         * let the state of idle sibling percolate up as IDLE, instead of
         * portraying it as CPU_NOT_IDLE.
         */
        if (sd->flags & SD_SHARE_CPUPOWER &&
            !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
                sd_idle = 1;

        schedstat_inc(sd, lb_count[CPU_NEWLY_IDLE]);
redo:
        group = find_busiest_group(sd, this_cpu, &imbalance, CPU_NEWLY_IDLE,
                                   &sd_idle, &cpus, NULL);
        if (!group) {
                schedstat_inc(sd, lb_nobusyg[CPU_NEWLY_IDLE]);
                goto out_balanced;
        }

        busiest = find_busiest_queue(group, CPU_NEWLY_IDLE, imbalance,
                                &cpus);
        if (!busiest) {
                schedstat_inc(sd, lb_nobusyq[CPU_NEWLY_IDLE]);
                goto out_balanced;
        }

        BUG_ON(busiest == this_rq);

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

        ld_moved = 0;
        if (busiest->nr_running > 1) {
                /* Attempt to move tasks */
                double_lock_balance(this_rq, busiest);
                /* this_rq->clock is already updated */
                update_rq_clock(busiest);
                ld_moved = move_tasks(this_rq, this_cpu, busiest,
                                        imbalance, sd, CPU_NEWLY_IDLE,
                                        &all_pinned);
                spin_unlock(&busiest->lock);

                if (unlikely(all_pinned)) {
                        cpu_clear(cpu_of(busiest), cpus);
                        if (!cpus_empty(cpus))
                                goto redo;
                }
        }

        if (!ld_moved) {
                schedstat_inc(sd, lb_failed[CPU_NEWLY_IDLE]);
                if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
                    !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
                        return -1;
        } else
                sd->nr_balance_failed = 0;

        return ld_moved;

out_balanced:
        schedstat_inc(sd, lb_balanced[CPU_NEWLY_IDLE]);
        if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
            !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
                return -1;
        sd->nr_balance_failed = 0;

        return 0;
}

/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
static void idle_balance(int this_cpu, struct rq *this_rq)
{
        struct sched_domain *sd;
        int pulled_task = -1;
        unsigned long next_balance = jiffies + HZ;

        for_each_domain(this_cpu, sd) {
                unsigned long interval;

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

                if (sd->flags & SD_BALANCE_NEWIDLE)
                        /* If we've pulled tasks over stop searching: */
                        pulled_task = load_balance_newidle(this_cpu,
                                                                this_rq, sd);

                interval = msecs_to_jiffies(sd->balance_interval);
                if (time_after(next_balance, sd->last_balance + interval))
                        next_balance = sd->last_balance + interval;
                if (pulled_task)
                        break;
        }
        if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
                /*
                 * We are going idle. next_balance may be set based on
                 * a busy processor. So reset next_balance.
                 */
                this_rq->next_balance = next_balance;
        }
}

/*
 * 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(struct rq *busiest_rq, int busiest_cpu)
{
        int target_cpu = busiest_rq->push_cpu;
        struct sched_domain *sd;
        struct rq *target_rq;

        /* Is there any task to move? */
        if (busiest_rq->nr_running <= 1)
                return;

        target_rq = cpu_rq(target_cpu);

        /*
         * This condition is "impossible", if it occurs
         * we need to fix it. Originally 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);
        update_rq_clock(busiest_rq);
        update_rq_clock(target_rq);

        /* Search for an sd spanning us and the target CPU. */
        for_each_domain(target_cpu, sd) {
                if ((sd->flags & SD_LOAD_BALANCE) &&
                    cpu_isset(busiest_cpu, sd->span))
                                break;
        }

        if (likely(sd)) {
                schedstat_inc(sd, alb_count);

                if (move_one_task(target_rq, target_cpu, busiest_rq,
                                  sd, CPU_IDLE))
                        schedstat_inc(sd, alb_pushed);
                else
                        schedstat_inc(sd, alb_failed);
        }
        spin_unlock(&target_rq->lock);
}

#ifdef CONFIG_NO_HZ
static struct {
        atomic_t load_balancer;
        cpumask_t cpu_mask;
} nohz ____cacheline_aligned = {
        .load_balancer = ATOMIC_INIT(-1),
        .cpu_mask = CPU_MASK_NONE,
};

/*
 * This routine will try to nominate the ilb (idle load balancing)
 * owner among the cpus whose ticks are stopped. ilb owner will do the idle
 * load balancing on behalf of all those cpus. If all the cpus in the system
 * go into this tickless mode, then there will be no ilb owner (as there is
 * no need for one) and all the cpus will sleep till the next wakeup event
 * arrives...
 *
 * For the ilb owner, tick is not stopped. And this tick will be used
 * for idle load balancing. ilb owner will still be part of
 * nohz.cpu_mask..
 *
 * While stopping the tick, this cpu will become the ilb owner if there
 * is no other owner. And will be the owner till that cpu becomes busy
 * or if all cpus in the system stop their ticks at which point
 * there is no need for ilb owner.
 *
 * When the ilb owner becomes busy, it nominates another owner, during the
 * next busy scheduler_tick()
 */
int select_nohz_load_balancer(int stop_tick)
{
        int cpu = smp_processor_id();

        if (stop_tick) {
                cpu_set(cpu, nohz.cpu_mask);
                cpu_rq(cpu)->in_nohz_recently = 1;

                /*
                 * If we are going offline and still the leader, give up!
                 */
                if (cpu_is_offline(cpu) &&
                    atomic_read(&nohz.load_balancer) == cpu) {
                        if (atomic_cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
                                BUG();
                        return 0;
                }

                /* time for ilb owner also to sleep */
                if (cpus_weight(nohz.cpu_mask) == num_online_cpus()) {
                        if (atomic_read(&nohz.load_balancer) == cpu)
                                atomic_set(&nohz.load_balancer, -1);
                        return 0;
                }

                if (atomic_read(&nohz.load_balancer) == -1) {
                        /* make me the ilb owner */
                        if (atomic_cmpxchg(&nohz.load_balancer, -1, cpu) == -1)
                                return 1;
                } else if (atomic_read(&nohz.load_balancer) == cpu)
                        return 1;
        } else {
                if (!cpu_isset(cpu, nohz.cpu_mask))
                        return 0;

                cpu_clear(cpu, nohz.cpu_mask);

                if (atomic_read(&nohz.load_balancer) == cpu)
                        if (atomic_cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
                                BUG();
        }
        return 0;
}
#endif

static DEFINE_SPINLOCK(balancing);

/*
 * 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.
 */
static void rebalance_domains(int cpu, enum cpu_idle_type idle)
{
        int balance = 1;
        struct rq *rq = cpu_rq(cpu);
        unsigned long interval;
        struct sched_domain *sd;
        /* Earliest time when we have to do rebalance again */
        unsigned long next_balance = jiffies + 60*HZ;
        int update_next_balance = 0;

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

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

                /* scale ms to jiffies */
                interval = msecs_to_jiffies(interval);
                if (unlikely(!interval))
                        interval = 1;
                if (interval > HZ*NR_CPUS/10)
                        interval = HZ*NR_CPUS/10;


                if (sd->flags & SD_SERIALIZE) {
                        if (!spin_trylock(&balancing))
                                goto out;
                }

                if (time_after_eq(jiffies, sd->last_balance + interval)) {
                        if (load_balance(cpu, rq, sd, idle, &balance)) {
                                /*
                                 * We've pulled tasks over so either we're no
                                 * longer idle, or one of our SMT siblings is
                                 * not idle.
                                 */
                                idle = CPU_NOT_IDLE;
                        }
                        sd->last_balance = jiffies;
                }
                if (sd->flags & SD_SERIALIZE)
                        spin_unlock(&balancing);
out:
                if (time_after(next_balance, sd->last_balance + interval)) {
                        next_balance = sd->last_balance + interval;
                        update_next_balance = 1;
                }

                /*
                 * Stop the load balance at this level. There is another
                 * CPU in our sched group which is doing load balancing more
                 * actively.
                 */
                if (!balance)
                        break;
        }

        /*
         * next_balance will be updated only when there is a need.
         * When the cpu is attached to null domain for ex, it will not be
         * updated.
         */
        if (likely(update_next_balance))
                rq->next_balance = next_balance;
}

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * In CONFIG_NO_HZ case, the idle load balance owner will do the
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
static void run_rebalance_domains(struct softirq_action *h)
{
        int this_cpu = smp_processor_id();
        struct rq *this_rq = cpu_rq(this_cpu);
        enum cpu_idle_type idle = this_rq->idle_at_tick ?
                                                CPU_IDLE : CPU_NOT_IDLE;

        rebalance_domains(this_cpu, idle);

#ifdef CONFIG_NO_HZ
        /*
         * If this cpu is the owner for idle load balancing, then do the
         * balancing on behalf of the other idle cpus whose ticks are
         * stopped.
         */
        if (this_rq->idle_at_tick &&
            atomic_read(&nohz.load_balancer) == this_cpu) {
                cpumask_t cpus = nohz.cpu_mask;
                struct rq *rq;
                int balance_cpu;

                cpu_clear(this_cpu, cpus);
                for_each_cpu_mask(balance_cpu, cpus) {
                        /*
                         * If this cpu gets work to do, stop the load balancing
                         * work being done for other cpus. Next load
                         * balancing owner will pick it up.
                         */
                        if (need_resched())
                                break;

                        rebalance_domains(balance_cpu, CPU_IDLE);

                        rq = cpu_rq(balance_cpu);
                        if (time_after(this_rq->next_balance, rq->next_balance))
                                this_rq->next_balance = rq->next_balance;
                }
        }
#endif
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 *
 * In case of CONFIG_NO_HZ, this is the place where we nominate a new
 * idle load balancing owner or decide to stop the periodic load balancing,
 * if the whole system is idle.
 */
static inline void trigger_load_balance(struct rq *rq, int cpu)
{
#ifdef CONFIG_NO_HZ
        /*
         * If we were in the nohz mode recently and busy at the current
         * scheduler tick, then check if we need to nominate new idle
         * load balancer.
         */
        if (rq->in_nohz_recently && !rq->idle_at_tick) {
                rq->in_nohz_recently = 0;

                if (atomic_read(&nohz.load_balancer) == cpu) {
                        cpu_clear(cpu, nohz.cpu_mask);
                        atomic_set(&nohz.load_balancer, -1);
                }

                if (atomic_read(&nohz.load_balancer) == -1) {
                        /*
                         * simple selection for now: Nominate the
                         * first cpu in the nohz list to be the next
                         * ilb owner.
                         *
                         * TBD: Traverse the sched domains and nominate
                         * the nearest cpu in the nohz.cpu_mask.
                         */
                        int ilb = first_cpu(nohz.cpu_mask);

                        if (ilb != NR_CPUS)
                                resched_cpu(ilb);
                }
        }

        /*
         * If this cpu is idle and doing idle load balancing for all the
         * cpus with ticks stopped, is it time for that to stop?
         */
        if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) == cpu &&
            cpus_weight(nohz.cpu_mask) == num_online_cpus()) {
                resched_cpu(cpu);
                return;
        }

        /*
         * If this cpu is idle and the idle load balancing is done by
         * someone else, then no need raise the SCHED_SOFTIRQ
         */
        if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) != cpu &&
            cpu_isset(cpu, nohz.cpu_mask))
                return;
#endif
        if (time_after_eq(jiffies, rq->next_balance))
                raise_softirq(SCHED_SOFTIRQ);
}

#else   /* CONFIG_SMP */

/*
 * on UP we do not need to balance between CPUs:
 */
static inline void idle_balance(int cpu, struct rq *rq)
{
}

#endif

DEFINE_PER_CPU(struct kernel_stat, kstat);

EXPORT_PER_CPU_SYMBOL(kstat);

/*
 * Return p->sum_exec_runtime plus any more ns on the sched_clock
 * that have not yet been banked in case the task is currently running.
 */
unsigned long long task_sched_runtime(struct task_struct *p)
{
        unsigned long flags;
        u64 ns, delta_exec;
        struct rq *rq;

        rq = task_rq_lock(p, &flags);
        ns = p->se.sum_exec_runtime;
        if (task_current(rq, p)) {
                update_rq_clock(rq);
                delta_exec = rq->clock - p->se.exec_start;
                if ((s64)delta_exec > 0)
                        ns += delta_exec;
        }
        task_rq_unlock(rq, &flags);

        return ns;
}

/*
 * Account user cpu time to a process.
 * @p: the process that the cpu time gets accounted to
 * @cputime: the cpu time spent in user space since the last update
 */
void account_user_time(struct task_struct *p, cputime_t cputime)
{
        struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
        cputime64_t tmp;

        p->utime = cputime_add(p->utime, cputime);

        /* Add user time to cpustat. */
        tmp = cputime_to_cputime64(cputime);
        if (TASK_NICE(p) > 0)
                cpustat->nice = cputime64_add(cpustat->nice, tmp);
        else
                cpustat->user = cputime64_add(cpustat->user, tmp);
}

/*
 * Account guest cpu time to a process.
 * @p: the process that the cpu time gets accounted to
 * @cputime: the cpu time spent in virtual machine since the last update
 */
static void account_guest_time(struct task_struct *p, cputime_t cputime)
{
        cputime64_t tmp;
        struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;

        tmp = cputime_to_cputime64(cputime);

        p->utime = cputime_add(p->utime, cputime);
        p->gtime = cputime_add(p->gtime, cputime);

        cpustat->user = cputime64_add(cpustat->user, tmp);
        cpustat->guest = cputime64_add(cpustat->guest, tmp);
}

/*
 * Account scaled user cpu time to a process.
 * @p: the process that the cpu time gets accounted to
 * @cputime: the cpu time spent in user space since the last update
 */
void account_user_time_scaled(struct task_struct *p, cputime_t cputime)
{
        p->utimescaled = cputime_add(p->utimescaled, cputime);
}

/*
 * Account system cpu time to a process.
 * @p: the process that the cpu time gets accounted to
 * @hardirq_offset: the offset to subtract from hardirq_count()
 * @cputime: the cpu time spent in kernel space since the last update
 */
void account_system_time(struct task_struct *p, int hardirq_offset,
                         cputime_t cputime)
{
        struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
        struct rq *rq = this_rq();
        cputime64_t tmp;

        if ((p->flags & PF_VCPU) && (irq_count() - hardirq_offset == 0))
                return account_guest_time(p, cputime);

        p->stime = cputime_add(p->stime, cputime);

        /* Add system time to cpustat. */
        tmp = cputime_to_cputime64(cputime);
        if (hardirq_count() - hardirq_offset)
                cpustat->irq = cputime64_add(cpustat->irq, tmp);
        else if (softirq_count())
                cpustat->softirq = cputime64_add(cpustat->softirq, tmp);
        else if (p != rq->idle)
                cpustat->system = cputime64_add(cpustat->system, tmp);
        else if (atomic_read(&rq->nr_iowait) > 0)
                cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
        else
                cpustat->idle = cputime64_add(cpustat->idle, tmp);
        /* Account for system time used */
        acct_update_integrals(p);
}

/*
 * Account scaled system cpu time to a process.
 * @p: the process that the cpu time gets accounted to
 * @hardirq_offset: the offset to subtract from hardirq_count()
 * @cputime: the cpu time spent in kernel space since the last update
 */
void account_system_time_scaled(struct task_struct *p, cputime_t cputime)
{
        p->stimescaled = cputime_add(p->stimescaled, cputime);
}

/*
 * Account for involuntary wait time.
 * @p: the process from which the cpu time has been stolen
 * @steal: the cpu time spent in involuntary wait
 */
void account_steal_time(struct task_struct *p, cputime_t steal)
{
        struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
        cputime64_t tmp = cputime_to_cputime64(steal);
        struct rq *rq = this_rq();

        if (p == rq->idle) {
                p->stime = cputime_add(p->stime, steal);
                if (atomic_read(&rq->nr_iowait) > 0)
                        cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
                else
                        cpustat->idle = cputime64_add(cpustat->idle, tmp);
        } else
                cpustat->steal = cputime64_add(cpustat->steal, tmp);
}

/*
 * 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(void)
{
        int cpu = smp_processor_id();
        struct rq *rq = cpu_rq(cpu);
        struct task_struct *curr = rq->curr;
        u64 next_tick = rq->tick_timestamp + TICK_NSEC;

        spin_lock(&rq->lock);
        __update_rq_clock(rq);
        /*
         * Let rq->clock advance by at least TICK_NSEC:
         */
        if (unlikely(rq->clock < next_tick))
                rq->clock = next_tick;
        rq->tick_timestamp = rq->clock;
        update_cpu_load(rq);
        if (curr != rq->idle) /* FIXME: needed? */
                curr->sched_class->task_tick(rq, curr, 0);
        spin_unlock(&rq->lock);

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

#if defined(CONFIG_PREEMPT) && defined(CONFIG_DEBUG_PREEMPT)

void fastcall add_preempt_count(int val)
{
        /*
         * Underflow?
         */
        if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
                return;
        preempt_count() += val;
        /*
         * Spinlock count overflowing soon?
         */
        DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
                                PREEMPT_MASK - 10);
}
EXPORT_SYMBOL(add_preempt_count);

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

        preempt_count() -= val;
}
EXPORT_SYMBOL(sub_preempt_count);

#endif

/*
 * Print scheduling while atomic bug:
 */
static noinline void __schedule_bug(struct task_struct *prev)
{
        struct pt_regs *regs = get_irq_regs();

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

        debug_show_held_locks(prev);
        if (irqs_disabled())
                print_irqtrace_events(prev);

        if (regs)
                show_regs(regs);
        else
                dump_stack();
}

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

        profile_hit(SCHED_PROFILING, __builtin_return_address(0));

        schedstat_inc(this_rq(), sched_count);
#ifdef CONFIG_SCHEDSTATS
        if (unlikely(prev->lock_depth >= 0)) {
                schedstat_inc(this_rq(), bkl_count);
                schedstat_inc(prev, sched_info.bkl_count);
        }
#endif
}

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

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

        class = sched_class_highest;
        for ( ; ; ) {
                p = class->pick_next_task(rq);
                if (p)
                        return p;
                /*
                 * Will never be NULL as the idle class always
                 * returns a non-NULL p:
                 */
                class = class->next;
        }
}

/*
 * schedule() is the main scheduler function.
 */
asmlinkage void __sched schedule(void)
{
        struct task_struct *prev, *next;
        long *switch_count;
        struct rq *rq;
        int cpu;

need_resched:
        preempt_disable();
        cpu = smp_processor_id();
        rq = cpu_rq(cpu);
        rcu_qsctr_inc(cpu);
        prev = rq->curr;
        switch_count = &prev->nivcsw;

        release_kernel_lock(prev);
need_resched_nonpreemptible:

        schedule_debug(prev);

        hrtick_clear(rq);

        /*
         * Do the rq-clock update outside the rq lock:
         */
        local_irq_disable();
        __update_rq_clock(rq);
        spin_lock(&rq->lock);
        clear_tsk_need_resched(prev);

        if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
                if (unlikely((prev->state & TASK_INTERRUPTIBLE) &&
                                unlikely(signal_pending(prev)))) {
                        prev->state = TASK_RUNNING;
                } else {
                        deactivate_task(rq, prev, 1);
                }
                switch_count = &prev->nvcsw;
        }

#ifdef CONFIG_SMP
        if (prev->sched_class->pre_schedule)
                prev->sched_class->pre_schedule(rq, prev);
#endif

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

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

        sched_info_switch(prev, next);

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

                context_switch(rq, prev, next); /* unlocks the rq */
                /*
                 * the context switch might have flipped the stack from under
                 * us, hence refresh the local variables.
                 */
                cpu = smp_processor_id();
                rq = cpu_rq(cpu);
        } else
                spin_unlock_irq(&rq->lock);

        hrtick_set(rq);

        if (unlikely(reacquire_kernel_lock(current) < 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 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();
#ifdef CONFIG_PREEMPT_BKL
        struct task_struct *task = current;
        int saved_lock_depth;
#endif
        /*
         * If there is a non-zero preempt_count or interrupts are disabled,
         * we do not want to preempt the current task. Just return..
         */
        if (likely(ti->preempt_count || irqs_disabled()))
                return;

        do {
                add_preempt_count(PREEMPT_ACTIVE);

                /*
                 * We keep the big kernel semaphore locked, but we
                 * clear ->lock_depth so that schedule() doesnt
                 * auto-release the semaphore:
                 */
#ifdef CONFIG_PREEMPT_BKL
                saved_lock_depth = task->lock_depth;
                task->lock_depth = -1;
#endif
                schedule();
#ifdef CONFIG_PREEMPT_BKL
                task->lock_depth = saved_lock_depth;
#endif
                sub_preempt_count(PREEMPT_ACTIVE);

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

/*
 * this is the entry point to schedule() from kernel preemption
 * off of irq context.
 * Note, that this is called and return with irqs disabled. This will
 * protect us against recursive calling from irq.
 */
asmlinkage void __sched preempt_schedule_irq(void)
{
        struct thread_info *ti = current_thread_info();
#ifdef CONFIG_PREEMPT_BKL
        struct task_struct *task = current;
        int saved_lock_depth;
#endif
        /* Catch callers which need to be fixed */
        BUG_ON(ti->preempt_count || !irqs_disabled());

        do {
                add_preempt_count(PREEMPT_ACTIVE);

                /*
                 * We keep the big kernel semaphore locked, but we
                 * clear ->lock_depth so that schedule() doesnt
                 * auto-release the semaphore:
                 */
#ifdef CONFIG_PREEMPT_BKL
                saved_lock_depth = task->lock_depth;
                task->lock_depth = -1;
#endif
                local_irq_enable();
                schedule();
                local_irq_disable();
#ifdef CONFIG_PREEMPT_BKL
                task->lock_depth = saved_lock_depth;
#endif
                sub_preempt_count(PREEMPT_ACTIVE);

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

#endif /* CONFIG_PREEMPT */

int default_wake_function(wait_queue_t *curr, unsigned mode, int sync,
                          void *key)
{
        return try_to_wake_up(curr->private, 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)
{
        wait_queue_t *curr, *next;

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

                if (curr->func(curr, mode, 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
 * @key: is directly passed to the wakeup function
 */
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 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 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);

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

                wait.flags |= WQ_FLAG_EXCLUSIVE;
                __add_wait_queue_tail(&x->wait, &wait);
                do {
                        if (state == TASK_INTERRUPTIBLE &&
                            signal_pending(current)) {
                                __remove_wait_queue(&x->wait, &wait);
                                return -ERESTARTSYS;
                        }
                        __set_current_state(state);
                        spin_unlock_irq(&x->wait.lock);
                        timeout = schedule_timeout(timeout);
                        spin_lock_irq(&x->wait.lock);
                        if (!timeout) {
                                __remove_wait_queue(&x->wait, &wait);
                                return timeout;
                        }
                } while (!x->done);
                __remove_wait_queue(&x->wait, &wait);
        }
        x->done--;
        return timeout;
}

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

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

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

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

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

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

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

        init_waitqueue_entry(&wait, current);

        __set_current_state(state);

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

        return timeout;
}

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

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

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

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

#ifdef CONFIG_RT_MUTEXES

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

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

        rq = task_rq_lock(p, &flags);
        update_rq_clock(rq);

        oldprio = p->prio;
        on_rq = p->se.on_rq;
        running = task_current(rq, p);
        if (on_rq) {
                dequeue_task(rq, p, 0);
                if (running)
                        p->sched_class->put_prev_task(rq, p);
        }

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

        p->prio = prio;

        if (on_rq) {
                if (running)
                        p->sched_class->set_curr_task(rq);

                enqueue_task(rq, p, 0);

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

#endif

void set_user_nice(struct task_struct *p, long nice)
{
        int old_prio, delta, on_rq;
        unsigned long flags;
        struct rq *rq;

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

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

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

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

        return (nice_rlim <= p->signal->rlim[RLIMIT_NICE].rlim_cur ||
                capable(CAP_SYS_NICE));
}

#ifdef __ARCH_WANT_SYS_NICE

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

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

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

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

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

        set_user_nice(current, nice);
        return 0;
}

#endif

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

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

/**
 * 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;
}

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

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

/* Actually do priority change: must hold rq lock. */
static void
__setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio)
{
        BUG_ON(p->se.on_rq);

        p->policy = policy;
        switch (p->policy) {
        case SCHED_NORMAL:
        case SCHED_BATCH:
        case SCHED_IDLE:
                p->sched_class = &fair_sched_class;
                break;
        case SCHED_FIFO:
        case SCHED_RR:
                p->sched_class = &rt_sched_class;
                break;
        }

        p->rt_priority = prio;
        p->normal_prio = normal_prio(p);
        /* we are holding p->pi_lock already */
        p->prio = rt_mutex_getprio(p);
        set_load_weight(p);
}

/**
 * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
 * @p: the task in question.
 * @policy: new policy.
 * @param: structure containing the new RT priority.
 *
 * NOTE that the task may be already dead.
 */
int sched_setscheduler(struct task_struct *p, int policy,
                       struct sched_param *param)
{
        int retval, oldprio, oldpolicy = -1, on_rq, running;
        unsigned long flags;
        const struct sched_class *prev_class = p->sched_class;
        struct rq *rq;

        /* may grab non-irq protected spin_locks */
        BUG_ON(in_interrupt());
recheck:
        /* double check policy once rq lock held */
        if (policy < 0)
                policy = oldpolicy = p->policy;
        else if (policy != SCHED_FIFO && policy != SCHED_RR &&
                        policy != SCHED_NORMAL && policy != SCHED_BATCH &&
                        policy != SCHED_IDLE)
                return -EINVAL;
        /*
         * Valid priorities for SCHED_FIFO and SCHED_RR are
         * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
         * SCHED_BATCH and SCHED_IDLE is 0.
         */
        if (param->sched_priority < 0 ||
            (p->mm && param->sched_priority > MAX_USER_RT_PRIO-1) ||
            (!p->mm && param->sched_priority > MAX_RT_PRIO-1))
                return -EINVAL;
        if (rt_policy(policy) != (param->sched_priority != 0))
                return -EINVAL;

        /*
         * Allow unprivileged RT tasks to decrease priority:
         */
        if (!capable(CAP_SYS_NICE)) {
                if (rt_policy(policy)) {
                        unsigned long rlim_rtprio;

                        if (!lock_task_sighand(p, &flags))
                                return -ESRCH;
                        rlim_rtprio = p->signal->rlim[RLIMIT_RTPRIO].rlim_cur;
                        unlock_task_sighand(p, &flags);

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

                        /* can't increase priority */
                        if (param->sched_priority > p->rt_priority &&
                            param->sched_priority > rlim_rtprio)
                                return -EPERM;
                }
                /*
                 * Like positive nice levels, dont allow tasks to
                 * move out of SCHED_IDLE either:
                 */
                if (p->policy == SCHED_IDLE && policy != SCHED_IDLE)
                        return -EPERM;

                /* can't change other user's priorities */
                if ((current->euid != p->euid) &&
                    (current->euid != p->uid))
                        return -EPERM;
        }

        retval = security_task_setscheduler(p, policy, param);
        if (retval)
                return retval;
        /*
         * make sure no PI-waiters arrive (or leave) while we are
         * changing the priority of the task:
         */
        spin_lock_irqsave(&p->pi_lock, flags);
        /*
         * To be able to change p->policy safely, the apropriate
         * runqueue lock must be held.
         */
        rq = __task_rq_lock(p);
        /* recheck policy now with rq lock held */
        if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
                policy = oldpolicy = -1;
                __task_rq_unlock(rq);
                spin_unlock_irqrestore(&p->pi_lock, flags);
                goto recheck;
        }
        update_rq_clock(rq);
        on_rq = p->se.on_rq;
        running = task_current(rq, p);
        if (on_rq) {
                deactivate_task(rq, p, 0);
                if (running)
                        p->sched_class->put_prev_task(rq, p);
        }

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

        if (on_rq) {
                if (running)
                        p->sched_class->set_curr_task(rq);

                activate_task(rq, p, 0);

                check_class_changed(rq, p, prev_class, oldprio, running);
        }
        __task_rq_unlock(rq);
        spin_unlock_irqrestore(&p->pi_lock, flags);

        rt_mutex_adjust_pi(p);

        return 0;
}
EXPORT_SYMBOL_GPL(sched_setscheduler);

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

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

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

        return retval;
}

/**
 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
 * @pid: the pid in question.
 * @policy: new policy.
 * @param: structure containing the new RT priority.
 */
asmlinkage long
sys_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
{
        /* negative values for policy are not valid */
        if (policy < 0)
                return -EINVAL;

        return do_sched_setscheduler(pid, policy, param);
}

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

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

        if (pid < 0)
                return -EINVAL;

        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);
        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;
        struct task_struct *p;
        int retval;

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

        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;

        return retval;

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

long sched_setaffinity(pid_t pid, cpumask_t new_mask)
{
        cpumask_t cpus_allowed;
        struct task_struct *p;
        int retval;

        get_online_cpus();
        read_lock(&tasklist_lock);

        p = find_process_by_pid(pid);
        if (!p) {
                read_unlock(&tasklist_lock);
                put_online_cpus();
                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 = security_task_setscheduler(p, 0, NULL);
        if (retval)
                goto out_unlock;

        cpus_allowed = cpuset_cpus_allowed(p);
        cpus_and(new_mask, new_mask, cpus_allowed);
 again:
        retval = set_cpus_allowed(p, new_mask);

        if (!retval) {
                cpus_allowed = cpuset_cpus_allowed(p);
                if (!cpus_subset(new_mask, cpus_allowed)) {
                        /*
                         * We must have raced with a concurrent cpuset
                         * update. Just reset the cpus_allowed to the
                         * cpuset's cpus_allowed
                         */
                        new_mask = cpus_allowed;
                        goto again;
                }
        }
out_unlock:
        put_task_struct(p);
        put_online_cpus();
        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 __read_mostly;
EXPORT_SYMBOL(cpu_present_map);

#ifndef CONFIG_SMP
cpumask_t cpu_online_map __read_mostly = CPU_MASK_ALL;
EXPORT_SYMBOL(cpu_online_map);

cpumask_t cpu_possible_map __read_mostly = CPU_MASK_ALL;
EXPORT_SYMBOL(cpu_possible_map);
#endif

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

        get_online_cpus();
        read_lock(&tasklist_lock);

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

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

        cpus_and(*mask, p->cpus_allowed, cpu_online_map);

out_unlock:
        read_unlock(&tasklist_lock);
        put_online_cpus();

        return retval;
}

/**
 * sys_sched_getaffinity - get the cpu affinity of a process
 * @pid: pid of the process
 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
 * @user_mask_ptr: user-space pointer to hold the current cpu mask
 */
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 to other tasks. If there are no
 * other threads running on this CPU then this function will return.
 */
asmlinkage long sys_sched_yield(void)
{
        struct rq *rq = this_rq_lock();

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

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

        schedule();

        return 0;
}

static void __cond_resched(void)
{
#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
        __might_sleep(__FILE__, __LINE__);
#endif
        /*
         * The BKS might be reacquired before we have dropped
         * PREEMPT_ACTIVE, which could trigger a second
         * cond_resched() call.
         */
        do {
                add_preempt_count(PREEMPT_ACTIVE);
                schedule();
                sub_preempt_count(PREEMPT_ACTIVE);
        } while (need_resched());
}

#if !defined(CONFIG_PREEMPT) || defined(CONFIG_PREEMPT_VOLUNTARY)
int __sched _cond_resched(void)
{
        if (need_resched() && !(preempt_count() & PREEMPT_ACTIVE) &&
                                        system_state == SYSTEM_RUNNING) {
                __cond_resched();
                return 1;
        }
        return 0;
}
EXPORT_SYMBOL(_cond_resched);
#endif

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

        if (need_lockbreak(lock)) {
                spin_unlock(lock);
                cpu_relax();
                ret = 1;
                spin_lock(lock);
        }
        if (need_resched() && system_state == SYSTEM_RUNNING) {
                spin_release(&lock->dep_map, 1, _THIS_IP_);
                _raw_spin_unlock(lock);
                preempt_enable_no_resched();
                __cond_resched();
                ret = 1;
                spin_lock(lock);
        }
        return ret;
}
EXPORT_SYMBOL(cond_resched_lock);

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

        if (need_resched() && system_state == SYSTEM_RUNNING) {
                local_bh_enable();
                __cond_resched();
                local_bh_disable();
                return 1;
        }
        return 0;
}
EXPORT_SYMBOL(cond_resched_softirq);

/**
 * yield - yield the current processor to other threads.
 *
 * 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 rq *rq = &__raw_get_cpu_var(runqueues);

        delayacct_blkio_start();
        atomic_inc(&rq->nr_iowait);
        schedule();
        atomic_dec(&rq->nr_iowait);
        delayacct_blkio_end();
}
EXPORT_SYMBOL(io_schedule);

long __sched io_schedule_timeout(long timeout)
{
        struct rq *rq = &__raw_get_cpu_var(runqueues);
        long ret;

        delayacct_blkio_start();
        atomic_inc(&rq->nr_iowait);
        ret = schedule_timeout(timeout);
        atomic_dec(&rq->nr_iowait);
        delayacct_blkio_end();
        return ret;
}

/**
 * sys_sched_get_priority_max - return maximum RT priority.
 * @policy: scheduling class.
 *
 * this syscall returns the maximum rt_priority that can be used
 * by a given scheduling class.
 */
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:
        case SCHED_BATCH:
        case SCHED_IDLE:
                ret = 0;
                break;
        }
        return ret;
}

/**
 * sys_sched_get_priority_min - return minimum RT priority.
 * @policy: scheduling class.
 *
 * this syscall returns the minimum rt_priority that can be used
 * by a given scheduling class.
 */
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:
        case SCHED_BATCH:
        case SCHED_IDLE:
                ret = 0;
        }
        return ret;
}

/**
 * sys_sched_rr_get_interval - return the default timeslice of a process.
 * @pid: pid of the process.
 * @interval: userspace pointer to the timeslice value.
 *
 * this syscall writes the default timeslice value of a given process
 * into the user-space timespec buffer. A value of '0' means infinity.
 */
asmlinkage
long sys_sched_rr_get_interval(pid_t pid, struct timespec __user *interval)
{
        struct task_struct *p;
        unsigned int time_slice;
        int retval;
        struct timespec t;

        if (pid < 0)
                return -EINVAL;

        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;

        /*
         * Time slice is 0 for SCHED_FIFO tasks and for SCHED_OTHER
         * tasks that are on an otherwise idle runqueue:
         */
        time_slice = 0;
        if (p->policy == SCHED_RR) {
                time_slice = DEF_TIMESLICE;
        } else {
                struct sched_entity *se = &p->se;
                unsigned long flags;
                struct rq *rq;

                rq = task_rq_lock(p, &flags);
                if (rq->cfs.load.weight)
                        time_slice = NS_TO_JIFFIES(sched_slice(&rq->cfs, se));
                task_rq_unlock(rq, &flags);
        }
        read_unlock(&tasklist_lock);
        jiffies_to_timespec(time_slice, &t);
        retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
        return retval;

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

static const char stat_nam[] = "RSDTtZX";

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

        state = p->state ? __ffs(p->state) + 1 : 0;
        printk(KERN_INFO "%-13.13s %c", p->comm,
                state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?');
#if BITS_PER_LONG == 32
        if (state == TASK_RUNNING)
                printk(KERN_CONT " running  ");
        else
                printk(KERN_CONT " %08lx ", thread_saved_pc(p));
#else
        if (state == TASK_RUNNING)
                printk(KERN_CONT "  running task    ");
        else
                printk(KERN_CONT " %016lx ", thread_saved_pc(p));
#endif
#ifdef CONFIG_DEBUG_STACK_USAGE
        {
                unsigned long *n = end_of_stack(p);
                while (!*n)
                        n++;
                free = (unsigned long)n - (unsigned long)end_of_stack(p);
        }
#endif
        printk(KERN_CONT "%5lu %5d %6d\n", free,
                task_pid_nr(p), task_pid_nr(p->real_parent));

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

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

#if BITS_PER_LONG == 32
        printk(KERN_INFO
                "  task                PC stack   pid father\n");
#else
        printk(KERN_INFO
                "  task                        PC stack   pid father\n");
#endif
        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();
                if (!state_filter || (p->state & state_filter))
                        sched_show_task(p);
        } while_each_thread(g, p);

        touch_all_softlockup_watchdogs();

#ifdef CONFIG_SCHED_DEBUG
        sysrq_sched_debug_show();
#endif
        read_unlock(&tasklist_lock);
        /*
         * Only show locks if all tasks are dumped:
         */
        if (state_filter == -1)
                debug_show_all_locks();
}

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

/**
 * init_idle - set up an idle thread for a given CPU
 * @idle: task in question
 * @cpu: cpu the idle task belongs to
 *
 * NOTE: this function does not set the idle thread's NEED_RESCHED
 * flag, to make booting more robust.
 */
void __cpuinit init_idle(struct task_struct *idle, int cpu)
{
        struct rq *rq = cpu_rq(cpu);
        unsigned long flags;

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

        idle->prio = idle->normal_prio = MAX_PRIO;
        idle->cpus_allowed = cpumask_of_cpu(cpu);
        __set_task_cpu(idle, cpu);

        spin_lock_irqsave(&rq->lock, flags);
        rq->curr = rq->idle = idle;
#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
        idle->oncpu = 1;
#endif
        spin_unlock_irqrestore(&rq->lock, flags);

        /* Set the preempt count _outside_ the spinlocks! */
#if defined(CONFIG_PREEMPT) && !defined(CONFIG_PREEMPT_BKL)
        task_thread_info(idle)->preempt_count = (idle->lock_depth >= 0);
#else
        task_thread_info(idle)->preempt_count = 0;
#endif
        /*
         * The idle tasks have their own, simple scheduling class:
         */
        idle->sched_class = &idle_sched_class;
}

/*
 * 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;

/*
 * Increase the granularity value when there are more CPUs,
 * because with more CPUs the 'effective latency' as visible
 * to users decreases. But the relationship is not linear,
 * so pick a second-best guess by going with the log2 of the
 * number of CPUs.
 *
 * This idea comes from the SD scheduler of Con Kolivas:
 */
static inline void sched_init_granularity(void)
{
        unsigned int factor = 1 + ilog2(num_online_cpus());
        const unsigned long limit = 200000000;

        sysctl_sched_min_granularity *= factor;
        if (sysctl_sched_min_granularity > limit)
                sysctl_sched_min_granularity = limit;

        sysctl_sched_latency *= factor;
        if (sysctl_sched_latency > limit)
                sysctl_sched_latency = limit;

        sysctl_sched_wakeup_granularity *= factor;
        sysctl_sched_batch_wakeup_granularity *= factor;
}

#ifdef CONFIG_SMP
/*
 * This is how migration works:
 *
 * 1) we queue a struct migration_req 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(struct task_struct *p, cpumask_t new_mask)
{
        struct migration_req req;
        unsigned long flags;
        struct rq *rq;
        int ret = 0;

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

        if (p->sched_class->set_cpus_allowed)
                p->sched_class->set_cpus_allowed(p, &new_mask);
        else {
                p->cpus_allowed = new_mask;
                p->nr_cpus_allowed = cpus_weight(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.
 *
 * Returns non-zero if task was successfully migrated.
 */
static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
{
        struct rq *rq_dest, *rq_src;
        int ret = 0, on_rq;

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

        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;

        on_rq = p->se.on_rq;
        if (on_rq)
                deactivate_task(rq_src, p, 0);

        set_task_cpu(p, dest_cpu);
        if (on_rq) {
                activate_task(rq_dest, p, 0);
                check_preempt_curr(rq_dest, p);
        }
        ret = 1;
out:
        double_rq_unlock(rq_src, rq_dest);
        return ret;
}

/*
 * 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)
{
        int cpu = (long)data;
        struct rq *rq;

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

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

                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, struct migration_req, list);
                list_del_init(head->next);

                spin_unlock(&rq->lock);
                __migrate_task(req->task, cpu, req->dest_cpu);
                local_irq_enable();

                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

static int __migrate_task_irq(struct task_struct *p, int src_cpu, int dest_cpu)
{
        int ret;

        local_irq_disable();
        ret = __migrate_task(p, src_cpu, dest_cpu);
        local_irq_enable();
        return ret;
}

/*
 * Figure out where task on dead CPU should go, use force if necessary.
 * NOTE: interrupts should be disabled by the caller
 */
static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
{
        unsigned long flags;
        cpumask_t mask;
        struct rq *rq;
        int dest_cpu;

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

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

                /* No more Mr. Nice Guy. */
                if (dest_cpu == NR_CPUS) {
                        cpumask_t cpus_allowed = cpuset_cpus_allowed_locked(p);
                        /*
                         * Try to stay on the same cpuset, where the
                         * current cpuset may be a subset of all cpus.
                         * The cpuset_cpus_allowed_locked() variant of
                         * cpuset_cpus_allowed() will not block. It must be
                         * called within calls to cpuset_lock/cpuset_unlock.
                         */
                        rq = task_rq_lock(p, &flags);
                        p->cpus_allowed = cpus_allowed;
                        dest_cpu = any_online_cpu(p->cpus_allowed);
                        task_rq_unlock(rq, &flags);

                        /*
                         * Don't tell them about moving exiting tasks or
                         * kernel threads (both mm NULL), since they never
                         * leave kernel.
                         */
                        if (p->mm && printk_ratelimit()) {
                                printk(KERN_INFO "process %d (%s) no "
                                       "longer affine to cpu%d\n",
                                        task_pid_nr(p), p->comm, dead_cpu);
                        }
                }
        } while (!__migrate_task_irq(p, 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(struct rq *rq_src)
{
        struct rq *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 *p, *t;

        read_lock(&tasklist_lock);

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

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

        read_unlock(&tasklist_lock);
}

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

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

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

        __setscheduler(rq, p, SCHED_FIFO, MAX_RT_PRIO-1);

        update_rq_clock(rq);
        activate_task(rq, p, 0);

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

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

        BUG_ON(cpu_online(smp_processor_id()));

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

/* called under rq->lock with disabled interrupts */
static void migrate_dead(unsigned int dead_cpu, struct task_struct *p)
{
        struct rq *rq = cpu_rq(dead_cpu);

        /* Must be exiting, otherwise would be on tasklist. */
        BUG_ON(!p->exit_state);

        /* Cannot have done final schedule yet: would have vanished. */
        BUG_ON(p->state == TASK_DEAD);

        get_task_struct(p);

        /*
         * 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, p);
        spin_lock_irq(&rq->lock);

        put_task_struct(p);
}

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

        for ( ; ; ) {
                if (!rq->nr_running)
                        break;
                update_rq_clock(rq);
                next = pick_next_task(rq, rq->curr);
                if (!next)
                        break;
                migrate_dead(dead_cpu, next);

        }
}
#endif /* CONFIG_HOTPLUG_CPU */

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

static struct ctl_table sd_ctl_dir[] = {
        {
                .procname       = "sched_domain",
                .mode           = 0555,
        },
        {0, },
};

static struct ctl_table sd_ctl_root[] = {
        {
                .ctl_name       = CTL_KERN,
                .procname       = "kernel",
                .mode           = 0555,
                .child          = sd_ctl_dir,
        },
        {0, },
};

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

        return entry;
}

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

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

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

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

static struct ctl_table *
sd_alloc_ctl_domain_table(struct sched_domain *sd)
{
        struct ctl_table *table = sd_alloc_ctl_entry(12);

        if (table == NULL)
                return NULL;

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

        return table;
}

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

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

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

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

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

        if (entry == NULL)
                return;

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

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

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

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

        switch (action) {

        case CPU_UP_PREPARE:
        case CPU_UP_PREPARE_FROZEN:
                p = kthread_create(migration_thread, hcpu, "migration/%d", cpu);
                if (IS_ERR(p))
                        return NOTIFY_BAD;
                kthread_bind(p, cpu);
                /* Must be high prio: stop_machine expects to yield to it. */
                rq = task_rq_lock(p, &flags);
                __setscheduler(rq, p, SCHED_FIFO, MAX_RT_PRIO-1);
                task_rq_unlock(rq, &flags);
                cpu_rq(cpu)->migration_thread = p;
                break;

        case CPU_ONLINE:
        case CPU_ONLINE_FROZEN:
                /* Strictly unnecessary, as first user will wake it. */
                wake_up_process(cpu_rq(cpu)->migration_thread);

                /* Update our root-domain */
                rq = cpu_rq(cpu);
                spin_lock_irqsave(&rq->lock, flags);
                if (rq->rd) {
                        BUG_ON(!cpu_isset(cpu, rq->rd->span));
                        cpu_set(cpu, rq->rd->online);
                }
                spin_unlock_irqrestore(&rq->lock, flags);
                break;

#ifdef CONFIG_HOTPLUG_CPU
        case CPU_UP_CANCELED:
        case CPU_UP_CANCELED_FROZEN:
                if (!cpu_rq(cpu)->migration_thread)
                        break;
                /* Unbind it from offline cpu so it can run. Fall thru. */
                kthread_bind(cpu_rq(cpu)->migration_thread,
                             any_online_cpu(cpu_online_map));
                kthread_stop(cpu_rq(cpu)->migration_thread);
                cpu_rq(cpu)->migration_thread = NULL;
                break;

        case CPU_DEAD:
        case CPU_DEAD_FROZEN:
                cpuset_lock(); /* around calls to cpuset_cpus_allowed_lock() */
                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) */
                spin_lock_irq(&rq->lock);
                update_rq_clock(rq);
                deactivate_task(rq, rq->idle, 0);
                rq->idle->static_prio = MAX_PRIO;
                __setscheduler(rq, rq->idle, SCHED_NORMAL, 0);
                rq->idle->sched_class = &idle_sched_class;
                migrate_dead_tasks(cpu);
                spin_unlock_irq(&rq->lock);
                cpuset_unlock();
                migrate_nr_uninterruptible(rq);
                BUG_ON(rq->nr_running != 0);

                /*
                 * No need to migrate the tasks: it was best-effort if
                 * they didn't take sched_hotcpu_mutex. Just wake up
                 * the requestors.
                 */
                spin_lock_irq(&rq->lock);
                while (!list_empty(&rq->migration_queue)) {
                        struct migration_req *req;

                        req = list_entry(rq->migration_queue.next,
                                         struct migration_req, list);
                        list_del_init(&req->list);
                        complete(&req->done);
                }
                spin_unlock_irq(&rq->lock);
                break;

        case CPU_DOWN_PREPARE:
                /* Update our root-domain */
                rq = cpu_rq(cpu);
                spin_lock_irqsave(&rq->lock, flags);
                if (rq->rd) {
                        BUG_ON(!cpu_isset(cpu, rq->rd->span));
                        cpu_clear(cpu, rq->rd->online);
                }
                spin_unlock_irqrestore(&rq->lock, flags);
                break;
#endif
        }
        return NOTIFY_OK;
}

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

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

        /* Start one for the boot CPU: */
        err = migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
        BUG_ON(err == NOTIFY_BAD);
        migration_call(&migration_notifier, CPU_ONLINE, cpu);
        register_cpu_notifier(&migration_notifier);
}
#endif

#ifdef CONFIG_SMP

/* Number of possible processor ids */
int nr_cpu_ids __read_mostly = NR_CPUS;
EXPORT_SYMBOL(nr_cpu_ids);

#ifdef CONFIG_SCHED_DEBUG

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

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

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

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

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

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

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

                if (!group->__cpu_power) {
                        printk(KERN_CONT "\n");
                        printk(KERN_ERR "ERROR: domain->cpu_power not "
                                        "set\n");
                        break;
                }

                if (!cpus_weight(group->cpumask)) {
                        printk(KERN_CONT "\n");
                        printk(KERN_ERR "ERROR: empty group\n");
                        break;
                }

                if (cpus_intersects(groupmask, group->cpumask)) {
                        printk(KERN_CONT "\n");
                        printk(KERN_ERR "ERROR: repeated CPUs\n");
                        break;
                }

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

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

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

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

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

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

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

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

        for (;;) {
                if (sched_domain_debug_one(sd, cpu, level))
                        break;
                level++;
                sd = sd->parent;
                if (!sd)
                        break;
        }
}
#else
# define sched_domain_debug(sd, cpu) do { } while (0)
#endif

static int sd_degenerate(struct sched_domain *sd)
{
        if (cpus_weight(sd->span) == 1)
                return 1;

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

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

        return 1;
}

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

        if (sd_degenerate(parent))
                return 1;

        if (!cpus_equal(sd->span, parent->span))
                return 0;

        /* Does parent contain flags not in child? */
        /* WAKE_BALANCE is a subset of WAKE_AFFINE */
        if (cflags & SD_WAKE_AFFINE)
                pflags &= ~SD_WAKE_BALANCE;
        /* Flags needing groups don't count if only 1 group in parent */
        if (parent->groups == parent->groups->next) {
                pflags &= ~(SD_LOAD_BALANCE |
                                SD_BALANCE_NEWIDLE |
                                SD_BALANCE_FORK |
                                SD_BALANCE_EXEC |
                                SD_SHARE_CPUPOWER |
                                SD_SHARE_PKG_RESOURCES);
        }
        if (~cflags & pflags)
                return 0;

        return 1;
}

static void rq_attach_root(struct rq *rq, struct root_domain *rd)
{
        unsigned long flags;
        const struct sched_class *class;

        spin_lock_irqsave(&rq->lock, flags);

        if (rq->rd) {
                struct root_domain *old_rd = rq->rd;

                for (class = sched_class_highest; class; class = class->next) {
                        if (class->leave_domain)
                                class->leave_domain(rq);
                }

                cpu_clear(rq->cpu, old_rd->span);
                cpu_clear(rq->cpu, old_rd->online);

                if (atomic_dec_and_test(&old_rd->refcount))
                        kfree(old_rd);
        }

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

        cpu_set(rq->cpu, rd->span);
        if (cpu_isset(rq->cpu, cpu_online_map))
                cpu_set(rq->cpu, rd->online);

        for (class = sched_class_highest; class; class = class->next) {
                if (class->join_domain)
                        class->join_domain(rq);
        }

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

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

        cpus_clear(rd->span);
        cpus_clear(rd->online);
}

static void init_defrootdomain(void)
{
        init_rootdomain(&def_root_domain);
        atomic_set(&def_root_domain.refcount, 1);
}

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

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

        init_rootdomain(rd);

        return rd;
}

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

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

        if (sd && sd_degenerate(sd)) {
                sd = sd->parent;
                if (sd)
                        sd->child = NULL;
        }

        sched_domain_debug(sd, cpu);

        rq_attach_root(rq, rd);
        rcu_assign_pointer(rq->sd, sd);
}

/* cpus with isolated domains */
static cpumask_t 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++)
                if (ints[i] < NR_CPUS)
                        cpu_set(ints[i], cpu_isolated_map);
        return 1;
}

__setup("isolcpus=", isolated_cpu_setup);

/*
 * init_sched_build_groups takes the cpumask we wish to span, and a pointer
 * to a function which identifies what group(along with sched group) a CPU
 * belongs to. The return value of group_fn must be a >= 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.
 */
static void
init_sched_build_groups(cpumask_t span, const cpumask_t *cpu_map,
                        int (*group_fn)(int cpu, const cpumask_t *cpu_map,
                                        struct sched_group **sg))
{
        struct sched_group *first = NULL, *last = NULL;
        cpumask_t covered = CPU_MASK_NONE;
        int i;

        for_each_cpu_mask(i, span) {
                struct sched_group *sg;
                int group = group_fn(i, cpu_map, &sg);
                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, cpu_map, NULL) != 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;
}

#define SD_NODES_PER_DOMAIN 16

#ifdef CONFIG_NUMA

/**
 * find_next_best_node - find the next node to include in a sched_domain
 * @node: node whose sched_domain we're building
 * @used_nodes: nodes already in the sched_domain
 *
 * Find the next node to include in a given scheduling domain. Simply
 * finds the closest node not already in the @used_nodes map.
 *
 * Should use nodemask_t.
 */
static int find_next_best_node(int node, unsigned long *used_nodes)
{
        int i, n, val, min_val, best_node = 0;

        min_val = INT_MAX;

        for (i = 0; i < MAX_NUMNODES; i++) {
                /* Start at @node */
                n = (node + i) % MAX_NUMNODES;

                if (!nr_cpus_node(n))
                        continue;

                /* Skip already used nodes */
                if (test_bit(n, used_nodes))
                        continue;

                /* Simple min distance search */
                val = node_distance(node, n);

                if (val < min_val) {
                        min_val = val;
                        best_node = n;
                }
        }

        set_bit(best_node, used_nodes);
        return best_node;
}

/**
 * sched_domain_node_span - get a cpumask for a node's sched_domain
 * @node: node whose cpumask we're constructing
 * @size: number of nodes to include in this span
 *
 * Given a node, construct a good cpumask for its sched_domain to span. It
 * should be one that prevents unnecessary balancing, but also spreads tasks
 * out optimally.
 */
static cpumask_t sched_domain_node_span(int node)
{
        DECLARE_BITMAP(used_nodes, MAX_NUMNODES);
        cpumask_t span, nodemask;
        int i;

        cpus_clear(span);
        bitmap_zero(used_nodes, MAX_NUMNODES);

        nodemask = node_to_cpumask(node);
        cpus_or(span, span, nodemask);
        set_bit(node, used_nodes);

        for (i = 1; i < SD_NODES_PER_DOMAIN; i++) {
                int next_node = find_next_best_node(node, used_nodes);

                nodemask = node_to_cpumask(next_node);
                cpus_or(span, span, nodemask);
        }

        return span;
}
#endif

int sched_smt_power_savings = 0, sched_mc_power_savings = 0;

/*
 * SMT sched-domains:
 */
#ifdef CONFIG_SCHED_SMT
static DEFINE_PER_CPU(struct sched_domain, cpu_domains);
static DEFINE_PER_CPU(struct sched_group, sched_group_cpus);

static int
cpu_to_cpu_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg)
{
        if (sg)
                *sg = &per_cpu(sched_group_cpus, cpu);
        return cpu;
}
#endif

/*
 * multi-core sched-domains:
 */
#ifdef CONFIG_SCHED_MC
static DEFINE_PER_CPU(struct sched_domain, core_domains);
static DEFINE_PER_CPU(struct sched_group, sched_group_core);
#endif

#if defined(CONFIG_SCHED_MC) && defined(CONFIG_SCHED_SMT)
static int
cpu_to_core_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg)
{
        int group;
        cpumask_t mask = per_cpu(cpu_sibling_map, cpu);
        cpus_and(mask, mask, *cpu_map);
        group = first_cpu(mask);
        if (sg)
                *sg = &per_cpu(sched_group_core, group);
        return group;
}
#elif defined(CONFIG_SCHED_MC)
static int
cpu_to_core_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg)
{
        if (sg)
                *sg = &per_cpu(sched_group_core, cpu);
        return cpu;
}
#endif

static DEFINE_PER_CPU(struct sched_domain, phys_domains);
static DEFINE_PER_CPU(struct sched_group, sched_group_phys);

static int
cpu_to_phys_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg)
{
        int group;
#ifdef CONFIG_SCHED_MC
        cpumask_t mask = cpu_coregroup_map(cpu);
        cpus_and(mask, mask, *cpu_map);
        group = first_cpu(mask);
#elif defined(CONFIG_SCHED_SMT)
        cpumask_t mask = per_cpu(cpu_sibling_map, cpu);
        cpus_and(mask, mask, *cpu_map);
        group = first_cpu(mask);
#else
        group = cpu;
#endif
        if (sg)
                *sg = &per_cpu(sched_group_phys, group);
        return group;
}

#ifdef CONFIG_NUMA
/*
 * The init_sched_build_groups can't handle what we want to do with node
 * groups, so roll our own. Now each node has its own list of groups which
 * gets dynamically allocated.
 */
static DEFINE_PER_CPU(struct sched_domain, node_domains);
static struct sched_group **sched_group_nodes_bycpu[NR_CPUS];

static DEFINE_PER_CPU(struct sched_domain, allnodes_domains);
static DEFINE_PER_CPU(struct sched_group, sched_group_allnodes);

static int cpu_to_allnodes_group(int cpu, const cpumask_t *cpu_map,
                                 struct sched_group **sg)
{
        cpumask_t nodemask = node_to_cpumask(cpu_to_node(cpu));
        int group;

        cpus_and(nodemask, nodemask, *cpu_map);
        group = first_cpu(nodemask);

        if (sg)
                *sg = &per_cpu(sched_group_allnodes, group);
        return group;
}

static void init_numa_sched_groups_power(struct sched_group *group_head)
{
        struct sched_group *sg = group_head;
        int j;

        if (!sg)
                return;
        do {
                for_each_cpu_mask(j, sg->cpumask) {
                        struct sched_domain *sd;

                        sd = &per_cpu(phys_domains, j);
                        if (j != first_cpu(sd->groups->cpumask)) {
                                /*
                                 * Only add "power" once for each
                                 * physical package.
                                 */
                                continue;
                        }

                        sg_inc_cpu_power(sg, sd->groups->__cpu_power);
                }
                sg = sg->next;
        } while (sg != group_head);
}
#endif

#ifdef CONFIG_NUMA
/* Free memory allocated for various sched_group structures */
static void free_sched_groups(const cpumask_t *cpu_map)
{
        int cpu, i;

        for_each_cpu_mask(cpu, *cpu_map) {
                struct sched_group **sched_group_nodes
                        = sched_group_nodes_bycpu[cpu];

                if (!sched_group_nodes)
                        continue;

                for (i = 0; i < MAX_NUMNODES; i++) {
                        cpumask_t nodemask = node_to_cpumask(i);
                        struct sched_group *oldsg, *sg = sched_group_nodes[i];

                        cpus_and(nodemask, nodemask, *cpu_map);
                        if (cpus_empty(nodemask))
                                continue;

                        if (sg == NULL)
                                continue;
                        sg = sg->next;
next_sg:
                        oldsg = sg;
                        sg = sg->next;
                        kfree(oldsg);
                        if (oldsg != sched_group_nodes[i])
                                goto next_sg;
                }
                kfree(sched_group_nodes);
                sched_group_nodes_bycpu[cpu] = NULL;
        }
}
#else
static void free_sched_groups(const cpumask_t *cpu_map)
{
}
#endif

/*
 * Initialize sched groups cpu_power.
 *
 * cpu_power indicates the capacity of sched group, which is used while
 * distributing the load between different sched groups in a sched domain.
 * Typically cpu_power for all the groups in a sched domain will be same unless
 * there are asymmetries in the topology. If there are asymmetries, group
 * having more cpu_power will pickup more load compared to the group having
 * less cpu_power.
 *
 * cpu_power will be a multiple of SCHED_LOAD_SCALE. This multiple represents
 * the maximum number of tasks a group can handle in the presence of other idle
 * or lightly loaded groups in the same sched domain.
 */
static void init_sched_groups_power(int cpu, struct sched_domain *sd)
{
        struct sched_domain *child;
        struct sched_group *group;

        WARN_ON(!sd || !sd->groups);

        if (cpu != first_cpu(sd->groups->cpumask))
                return;

        child = sd->child;

        sd->groups->__cpu_power = 0;

        /*
         * For perf policy, if the groups in child domain share resources
         * (for example cores sharing some portions of the cache hierarchy
         * or SMT), then set this domain groups cpu_power such that each group
         * can handle only one task, when there are other idle groups in the
         * same sched domain.
         */
        if (!child || (!(sd->flags & SD_POWERSAVINGS_BALANCE) &&
                       (child->flags &
                        (SD_SHARE_CPUPOWER | SD_SHARE_PKG_RESOURCES)))) {
                sg_inc_cpu_power(sd->groups, SCHED_LOAD_SCALE);
                return;
        }

        /*
         * add cpu_power of each child group to this groups cpu_power
         */
        group = child->groups;
        do {
                sg_inc_cpu_power(sd->groups, group->__cpu_power);
                group = group->next;
        } while (group != child->groups);
}

/*
 * Build sched domains for a given set of cpus and attach the sched domains
 * to the individual cpus
 */
static int build_sched_domains(const cpumask_t *cpu_map)
{
        int i;
        struct root_domain *rd;
#ifdef CONFIG_NUMA
        struct sched_group **sched_group_nodes = NULL;
        int sd_allnodes = 0;

        /*
         * Allocate the per-node list of sched groups
         */
        sched_group_nodes = kcalloc(MAX_NUMNODES, sizeof(struct sched_group *),
                                    GFP_KERNEL);
        if (!sched_group_nodes) {
                printk(KERN_WARNING "Can not alloc sched group node list\n");
                return -ENOMEM;
        }
        sched_group_nodes_bycpu[first_cpu(*cpu_map)] = sched_group_nodes;
#endif

        rd = alloc_rootdomain();
        if (!rd) {
                printk(KERN_WARNING "Cannot alloc root domain\n");
                return -ENOMEM;
        }

        /*
         * Set up domains for cpus specified by the cpu_map.
         */
        for_each_cpu_mask(i, *cpu_map) {
                struct sched_domain *sd = NULL, *p;
                cpumask_t nodemask = node_to_cpumask(cpu_to_node(i));

                cpus_and(nodemask, nodemask, *cpu_map);

#ifdef CONFIG_NUMA
                if (cpus_weight(*cpu_map) >
                                SD_NODES_PER_DOMAIN*cpus_weight(nodemask)) {
                        sd = &per_cpu(allnodes_domains, i);
                        *sd = SD_ALLNODES_INIT;
                        sd->span = *cpu_map;
                        cpu_to_allnodes_group(i, cpu_map, &sd->groups);
                        p = sd;
                        sd_allnodes = 1;
                } else
                        p = NULL;

                sd = &per_cpu(node_domains, i);
                *sd = SD_NODE_INIT;
                sd->span = sched_domain_node_span(cpu_to_node(i));
                sd->parent = p;
                if (p)
                        p->child = sd;
                cpus_and(sd->span, sd->span, *cpu_map);
#endif

                p = sd;
                sd = &per_cpu(phys_domains, i);
                *sd = SD_CPU_INIT;
                sd->span = nodemask;
                sd->parent = p;
                if (p)
                        p->child = sd;
                cpu_to_phys_group(i, cpu_map, &sd->groups);

#ifdef CONFIG_SCHED_MC
                p = sd;
                sd = &per_cpu(core_domains, i);
                *sd = SD_MC_INIT;
                sd->span = cpu_coregroup_map(i);
                cpus_and(sd->span, sd->span, *cpu_map);
                sd->parent = p;
                p->child = sd;
                cpu_to_core_group(i, cpu_map, &sd->groups);
#endif

#ifdef CONFIG_SCHED_SMT
                p = sd;
                sd = &per_cpu(cpu_domains, i);
                *sd = SD_SIBLING_INIT;
                sd->span = per_cpu(cpu_sibling_map, i);
                cpus_and(sd->span, sd->span, *cpu_map);
                sd->parent = p;
                p->child = sd;
                cpu_to_cpu_group(i, cpu_map, &sd->groups);
#endif
        }

#ifdef CONFIG_SCHED_SMT
        /* Set up CPU (sibling) groups */
        for_each_cpu_mask(i, *cpu_map) {
                cpumask_t this_sibling_map = per_cpu(cpu_sibling_map, i);
                cpus_and(this_sibling_map, this_sibling_map, *cpu_map);
                if (i != first_cpu(this_sibling_map))
                        continue;

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

#ifdef CONFIG_SCHED_MC
        /* Set up multi-core groups */
        for_each_cpu_mask(i, *cpu_map) {
                cpumask_t this_core_map = cpu_coregroup_map(i);
                cpus_and(this_core_map, this_core_map, *cpu_map);
                if (i != first_cpu(this_core_map))
                        continue;
                init_sched_build_groups(this_core_map, cpu_map,
                                        &cpu_to_core_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_map);
                if (cpus_empty(nodemask))
                        continue;

                init_sched_build_groups(nodemask, cpu_map, &cpu_to_phys_group);
        }

#ifdef CONFIG_NUMA
        /* Set up node groups */
        if (sd_allnodes)
                init_sched_build_groups(*cpu_map, cpu_map,
                                        &cpu_to_allnodes_group);

        for (i = 0; i < MAX_NUMNODES; i++) {
                /* Set up node groups */
                struct sched_group *sg, *prev;
                cpumask_t nodemask = node_to_cpumask(i);
                cpumask_t domainspan;
                cpumask_t covered = CPU_MASK_NONE;
                int j;

                cpus_and(nodemask, nodemask, *cpu_map);
                if (cpus_empty(nodemask)) {
                        sched_group_nodes[i] = NULL;
                        continue;
                }

                domainspan = sched_domain_node_span(i);
                cpus_and(domainspan, domainspan, *cpu_map);

                sg = kmalloc_node(sizeof(struct sched_group), GFP_KERNEL, i);
                if (!sg) {
                        printk(KERN_WARNING "Can not alloc domain group for "
                                "node %d\n", i);
                        goto error;
                }
                sched_group_nodes[i] = sg;
                for_each_cpu_mask(j, nodemask) {
                        struct sched_domain *sd;

                        sd = &per_cpu(node_domains, j);
                        sd->groups = sg;
                }
                sg->__cpu_power = 0;
                sg->cpumask = nodemask;
                sg->next = sg;
                cpus_or(covered, covered, nodemask);
                prev = sg;

                for (j = 0; j < MAX_NUMNODES; j++) {
                        cpumask_t tmp, notcovered;
                        int n = (i + j) % MAX_NUMNODES;

                        cpus_complement(notcovered, covered);
                        cpus_and(tmp, notcovered, *cpu_map);
                        cpus_and(tmp, tmp, domainspan);
                        if (cpus_empty(tmp))
                                break;

                        nodemask = node_to_cpumask(n);
                        cpus_and(tmp, tmp, nodemask);
                        if (cpus_empty(tmp))
                                continue;

                        sg = kmalloc_node(sizeof(struct sched_group),
                                          GFP_KERNEL, i);
                        if (!sg) {
                                printk(KERN_WARNING
                                "Can not alloc domain group for node %d\n", j);
                                goto error;
                        }
                        sg->__cpu_power = 0;
                        sg->cpumask = tmp;
                        sg->next = prev->next;
                        cpus_or(covered, covered, tmp);
                        prev->next = sg;
                        prev = sg;
                }
        }
#endif

        /* Calculate CPU power for physical packages and nodes */
#ifdef CONFIG_SCHED_SMT
        for_each_cpu_mask(i, *cpu_map) {
                struct sched_domain *sd = &per_cpu(cpu_domains, i);

                init_sched_groups_power(i, sd);
        }
#endif
#ifdef CONFIG_SCHED_MC
        for_each_cpu_mask(i, *cpu_map) {
                struct sched_domain *sd = &per_cpu(core_domains, i);

                init_sched_groups_power(i, sd);
        }
#endif

        for_each_cpu_mask(i, *cpu_map) {
                struct sched_domain *sd = &per_cpu(phys_domains, i);

                init_sched_groups_power(i, sd);
        }

#ifdef CONFIG_NUMA
        for (i = 0; i < MAX_NUMNODES; i++)
                init_numa_sched_groups_power(sched_group_nodes[i]);

        if (sd_allnodes) {
                struct sched_group *sg;

                cpu_to_allnodes_group(first_cpu(*cpu_map), cpu_map, &sg);
                init_numa_sched_groups_power(sg);
        }
#endif

        /* Attach the domains */
        for_each_cpu_mask(i, *cpu_map) {
                struct sched_domain *sd;
#ifdef CONFIG_SCHED_SMT
                sd = &per_cpu(cpu_domains, i);
#elif defined(CONFIG_SCHED_MC)
                sd = &per_cpu(core_domains, i);
#else
                sd = &per_cpu(phys_domains, i);
#endif
                cpu_attach_domain(sd, rd, i);
        }

        return 0;

#ifdef CONFIG_NUMA
error:
        free_sched_groups(cpu_map);
        return -ENOMEM;
#endif
}

static cpumask_t *doms_cur;     /* current sched domains */
static int ndoms_cur;           /* number of sched domains in 'doms_cur' */

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

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

        ndoms_cur = 1;
        doms_cur = kmalloc(sizeof(cpumask_t), GFP_KERNEL);
        if (!doms_cur)
                doms_cur = &fallback_doms;
        cpus_andnot(*doms_cur, *cpu_map, cpu_isolated_map);
        err = build_sched_domains(doms_cur);
        register_sched_domain_sysctl();

        return err;
}

static void arch_destroy_sched_domains(const cpumask_t *cpu_map)
{
        free_sched_groups(cpu_map);
}

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

        unregister_sched_domain_sysctl();

        for_each_cpu_mask(i, *cpu_map)
                cpu_attach_domain(NULL, &def_root_domain, i);
        synchronize_sched();
        arch_destroy_sched_domains(cpu_map);
}

/*
 * Partition sched domains as specified by the 'ndoms_new'
 * cpumasks in the array doms_new[] of cpumasks. This compares
 * doms_new[] to the current sched domain partitioning, doms_cur[].
 * It destroys each deleted domain and builds each new domain.
 *
 * 'doms_new' is an array of cpumask_t's of length 'ndoms_new'.
 * The masks don't intersect (don't overlap.) We should setup one
 * sched domain for each mask. CPUs not in any of the cpumasks will
 * not be load balanced. If the same cpumask appears both in the
 * current 'doms_cur' domains and in the new 'doms_new', we can leave
 * it as it is.
 *
 * The passed in 'doms_new' should be kmalloc'd. This routine takes
 * ownership of it and will kfree it when done with it. If the caller
 * failed the kmalloc call, then it can pass in doms_new == NULL,
 * and partition_sched_domains() will fallback to the single partition
 * 'fallback_doms'.
 *
 * Call with hotplug lock held
 */
void partition_sched_domains(int ndoms_new, cpumask_t *doms_new)
{
        int i, j;

        lock_doms_cur();

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

        if (doms_new == NULL) {
                ndoms_new = 1;
                doms_new = &fallback_doms;
                cpus_andnot(doms_new[0], cpu_online_map, cpu_isolated_map);
        }

        /* Destroy deleted domains */
        for (i = 0; i < ndoms_cur; i++) {
                for (j = 0; j < ndoms_new; j++) {
                        if (cpus_equal(doms_cur[i], doms_new[j]))
                                goto match1;
                }
                /* no match - a current sched domain not in new doms_new[] */
                detach_destroy_domains(doms_cur + i);
match1:
                ;
        }

        /* Build new domains */
        for (i = 0; i < ndoms_new; i++) {
                for (j = 0; j < ndoms_cur; j++) {
                        if (cpus_equal(doms_new[i], doms_cur[j]))
                                goto match2;
                }
                /* no match - add a new doms_new */
                build_sched_domains(doms_new + i);
match2:
                ;
        }

        /* Remember the new sched domains */
        if (doms_cur != &fallback_doms)
                kfree(doms_cur);
        doms_cur = doms_new;
        ndoms_cur = ndoms_new;

        register_sched_domain_sysctl();

        unlock_doms_cur();
}

#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
static int arch_reinit_sched_domains(void)
{
        int err;

        get_online_cpus();
        detach_destroy_domains(&cpu_online_map);
        err = arch_init_sched_domains(&cpu_online_map);
        put_online_cpus();

        return err;
}

static ssize_t sched_power_savings_store(const char *buf, size_t count, int smt)
{
        int ret;

        if (buf[0] != '0' && buf[0] != '1')
                return -EINVAL;

        if (smt)
                sched_smt_power_savings = (buf[0] == '1');
        else
                sched_mc_power_savings = (buf[0] == '1');

        ret = arch_reinit_sched_domains();

        return ret ? ret : count;
}

#ifdef CONFIG_SCHED_MC
static ssize_t sched_mc_power_savings_show(struct sys_device *dev, char *page)
{
        return sprintf(page, "%u\n", sched_mc_power_savings);
}
static ssize_t sched_mc_power_savings_store(struct sys_device *dev,
                                            const char *buf, size_t count)
{
        return sched_power_savings_store(buf, count, 0);
}
static SYSDEV_ATTR(sched_mc_power_savings, 0644, sched_mc_power_savings_show,
                   sched_mc_power_savings_store);
#endif

#ifdef CONFIG_SCHED_SMT
static ssize_t sched_smt_power_savings_show(struct sys_device *dev, char *page)
{
        return sprintf(page, "%u\n", sched_smt_power_savings);
}
static ssize_t sched_smt_power_savings_store(struct sys_device *dev,
                                             const char *buf, size_t count)
{
        return sched_power_savings_store(buf, count, 1);
}
static SYSDEV_ATTR(sched_smt_power_savings, 0644, sched_smt_power_savings_show,
                   sched_smt_power_savings_store);
#endif

int sched_create_sysfs_power_savings_entries(struct sysdev_class *cls)
{
        int err = 0;

#ifdef CONFIG_SCHED_SMT
        if (smt_capable())
                err = sysfs_create_file(&cls->kset.kobj,
                                        &attr_sched_smt_power_savings.attr);
#endif
#ifdef CONFIG_SCHED_MC
        if (!err && mc_capable())
                err = sysfs_create_file(&cls->kset.kobj,
                                        &attr_sched_mc_power_savings.attr);
#endif
        return err;
}
#endif

/*
 * 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 the NULL 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)
{
        switch (action) {
        case CPU_UP_PREPARE:
        case CPU_UP_PREPARE_FROZEN:
        case CPU_DOWN_PREPARE:
        case CPU_DOWN_PREPARE_FROZEN:
                detach_destroy_domains(&cpu_online_map);
                return NOTIFY_OK;

        case CPU_UP_CANCELED:
        case CPU_UP_CANCELED_FROZEN:
        case CPU_DOWN_FAILED:
        case CPU_DOWN_FAILED_FROZEN:
        case CPU_ONLINE:
        case CPU_ONLINE_FROZEN:
        case CPU_DEAD:
        case CPU_DEAD_FROZEN:
                /*
                 * 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(&cpu_online_map);

        return NOTIFY_OK;
}

void __init sched_init_smp(void)
{
        cpumask_t non_isolated_cpus;

        get_online_cpus();
        arch_init_sched_domains(&cpu_online_map);
        cpus_andnot(non_isolated_cpus, cpu_possible_map, cpu_isolated_map);
        if (cpus_empty(non_isolated_cpus))
                cpu_set(smp_processor_id(), non_isolated_cpus);
        put_online_cpus();
        /* XXX: Theoretical race here - CPU may be hotplugged now */
        hotcpu_notifier(update_sched_domains, 0);

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

#ifdef CONFIG_FAIR_GROUP_SCHED
        if (nr_cpu_ids == 1)
                return;

        lb_monitor_task = kthread_create(load_balance_monitor, NULL,
                                         "group_balance");
        if (!IS_ERR(lb_monitor_task)) {
                lb_monitor_task->flags |= PF_NOFREEZE;
                wake_up_process(lb_monitor_task);
        } else {
                printk(KERN_ERR "Could not create load balance monitor thread"
                        "(error = %ld) \n", PTR_ERR(lb_monitor_task));
        }
#endif
}
#else
void __init sched_init_smp(void)
{
        sched_init_granularity();
}
#endif /* CONFIG_SMP */

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

static void init_cfs_rq(struct cfs_rq *cfs_rq, struct rq *rq)
{
        cfs_rq->tasks_timeline = RB_ROOT;
#ifdef CONFIG_FAIR_GROUP_SCHED
        cfs_rq->rq = rq;
#endif
        cfs_rq->min_vruntime = (u64)(-(1LL << 20));
}

void __init sched_init(void)
{
        int highest_cpu = 0;
        int i, j;

#ifdef CONFIG_SMP
        init_defrootdomain();
#endif

        for_each_possible_cpu(i) {
                struct rt_prio_array *array;
                struct rq *rq;

                rq = cpu_rq(i);
                spin_lock_init(&rq->lock);
                lockdep_set_class(&rq->lock, &rq->rq_lock_key);
                rq->nr_running = 0;
                rq->clock = 1;
                init_cfs_rq(&rq->cfs, rq);
#ifdef CONFIG_FAIR_GROUP_SCHED
                INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
                {
                        struct cfs_rq *cfs_rq = &per_cpu(init_cfs_rq, i);
                        struct sched_entity *se =
                                         &per_cpu(init_sched_entity, i);

                        init_cfs_rq_p[i] = cfs_rq;
                        init_cfs_rq(cfs_rq, rq);
                        cfs_rq->tg = &init_task_group;
                        list_add(&cfs_rq->leaf_cfs_rq_list,
                                                         &rq->leaf_cfs_rq_list);

                        init_sched_entity_p[i] = se;
                        se->cfs_rq = &rq->cfs;
                        se->my_q = cfs_rq;
                        se->load.weight = init_task_group_load;
                        se->load.inv_weight =
                                 div64_64(1ULL<<32, init_task_group_load);
                        se->parent = NULL;
                }
                init_task_group.shares = init_task_group_load;
#endif

                for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
                        rq->cpu_load[j] = 0;
#ifdef CONFIG_SMP
                rq->sd = NULL;
                rq->rd = NULL;
                rq->active_balance = 0;
                rq->next_balance = jiffies;
                rq->push_cpu = 0;
                rq->cpu = i;
                rq->migration_thread = NULL;
                INIT_LIST_HEAD(&rq->migration_queue);
                rq->rt.highest_prio = MAX_RT_PRIO;
                rq->rt.overloaded = 0;
                rq_attach_root(rq, &def_root_domain);
#endif
                init_rq_hrtick(rq);

                atomic_set(&rq->nr_iowait, 0);

                array = &rq->rt.active;
                for (j = 0; j < MAX_RT_PRIO; j++) {
                        INIT_LIST_HEAD(array->queue + j);
                        __clear_bit(j, array->bitmap);
                }
                highest_cpu = i;
                /* delimiter for bitsearch: */
                __set_bit(MAX_RT_PRIO, array->bitmap);
        }

        set_load_weight(&init_task);

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

#ifdef CONFIG_SMP
        nr_cpu_ids = highest_cpu + 1;
        open_softirq(SCHED_SOFTIRQ, run_rebalance_domains, NULL);
#endif

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

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

        /*
         * Make us the idle thread. Technically, schedule() should not be
         * called from this thread, however somewhere below it might be,
         * but because we are the idle thread, we just pick up running again
         * when this runqueue becomes "idle".
         */
        init_idle(current, smp_processor_id());
        /*
         * During early bootup we pretend to be a normal task:
         */
        current->sched_class = &fair_sched_class;
}

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

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

#ifdef CONFIG_MAGIC_SYSRQ
static void normalize_task(struct rq *rq, struct task_struct *p)
{
        int on_rq;
        update_rq_clock(rq);
        on_rq = p->se.on_rq;
        if (on_rq)
                deactivate_task(rq, p, 0);
        __setscheduler(rq, p, SCHED_NORMAL, 0);
        if (on_rq) {
                activate_task(rq, p, 0);
                resched_task(rq->curr);
        }
}

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

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

                p->se.exec_start                = 0;
#ifdef CONFIG_SCHEDSTATS
                p->se.wait_start                = 0;
                p->se.sleep_start               = 0;
                p->se.block_start               = 0;
#endif
                task_rq(p)->clock               = 0;

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

                spin_lock_irqsave(&p->pi_lock, flags);
                rq = __task_rq_lock(p);

                normalize_task(rq, p);

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

        read_unlock_irq(&tasklist_lock);
}

#endif /* CONFIG_MAGIC_SYSRQ */

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

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

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

#endif

#ifdef CONFIG_FAIR_GROUP_SCHED

#ifdef CONFIG_SMP
/*
 * distribute shares of all task groups among their schedulable entities,
 * to reflect load distrbution across cpus.
 */
static int rebalance_shares(struct sched_domain *sd, int this_cpu)
{
        struct cfs_rq *cfs_rq;
        struct rq *rq = cpu_rq(this_cpu);
        cpumask_t sdspan = sd->span;
        int balanced = 1;

        /* Walk thr' all the task groups that we have */
        for_each_leaf_cfs_rq(rq, cfs_rq) {
                int i;
                unsigned long total_load = 0, total_shares;
                struct task_group *tg = cfs_rq->tg;

                /* Gather total task load of this group across cpus */
                for_each_cpu_mask(i, sdspan)
                        total_load += tg->cfs_rq[i]->load.weight;

                /* Nothing to do if this group has no load */
                if (!total_load)
                        continue;

                /*
                 * tg->shares represents the number of cpu shares the task group
                 * is eligible to hold on a single cpu. On N cpus, it is
                 * eligible to hold (N * tg->shares) number of cpu shares.
                 */
                total_shares = tg->shares * cpus_weight(sdspan);

                /*
                 * redistribute total_shares across cpus as per the task load
                 * distribution.
                 */
                for_each_cpu_mask(i, sdspan) {
                        unsigned long local_load, local_shares;

                        local_load = tg->cfs_rq[i]->load.weight;
                        local_shares = (local_load * total_shares) / total_load;
                        if (!local_shares)
                                local_shares = MIN_GROUP_SHARES;
                        if (local_shares == tg->se[i]->load.weight)
                                continue;

                        spin_lock_irq(&cpu_rq(i)->lock);
                        set_se_shares(tg->se[i], local_shares);
                        spin_unlock_irq(&cpu_rq(i)->lock);
                        balanced = 0;
                }
        }

        return balanced;
}

/*
 * How frequently should we rebalance_shares() across cpus?
 *
 * The more frequently we rebalance shares, the more accurate is the fairness
 * of cpu bandwidth distribution between task groups. However higher frequency
 * also implies increased scheduling overhead.
 *
 * sysctl_sched_min_bal_int_shares represents the minimum interval between
 * consecutive calls to rebalance_shares() in the same sched domain.
 *
 * sysctl_sched_max_bal_int_shares represents the maximum interval between
 * consecutive calls to rebalance_shares() in the same sched domain.
 *
 * These settings allows for the appropriate tradeoff between accuracy of
 * fairness and the associated overhead.
 *
 */

/* default: 8ms, units: milliseconds */
const_debug unsigned int sysctl_sched_min_bal_int_shares = 8;

/* default: 128ms, units: milliseconds */
const_debug unsigned int sysctl_sched_max_bal_int_shares = 128;

/* kernel thread that runs rebalance_shares() periodically */
static int load_balance_monitor(void *unused)
{
        unsigned int timeout = sysctl_sched_min_bal_int_shares;
        struct sched_param schedparm;
        int ret;

        /*
         * We don't want this thread's execution to be limited by the shares
         * assigned to default group (init_task_group). Hence make it run
         * as a SCHED_RR RT task at the lowest priority.
         */
        schedparm.sched_priority = 1;
        ret = sched_setscheduler(current, SCHED_RR, &schedparm);
        if (ret)
                printk(KERN_ERR "Couldn't set SCHED_RR policy for load balance"
                                " monitor thread (error = %d) \n", ret);

        while (!kthread_should_stop()) {
                int i, cpu, balanced = 1;

                /* Prevent cpus going down or coming up */
                get_online_cpus();
                /* lockout changes to doms_cur[] array */
                lock_doms_cur();
                /*
                 * Enter a rcu read-side critical section to safely walk rq->sd
                 * chain on various cpus and to walk task group list
                 * (rq->leaf_cfs_rq_list) in rebalance_shares().
                 */
                rcu_read_lock();

                for (i = 0; i < ndoms_cur; i++) {
                        cpumask_t cpumap = doms_cur[i];
                        struct sched_domain *sd = NULL, *sd_prev = NULL;

                        cpu = first_cpu(cpumap);

                        /* Find the highest domain at which to balance shares */
                        for_each_domain(cpu, sd) {
                                if (!(sd->flags & SD_LOAD_BALANCE))
                                        continue;
                                sd_prev = sd;
                        }

                        sd = sd_prev;
                        /* sd == NULL? No load balance reqd in this domain */
                        if (!sd)
                                continue;

                        balanced &= rebalance_shares(sd, cpu);
                }

                rcu_read_unlock();

                unlock_doms_cur();
                put_online_cpus();

                if (!balanced)
                        timeout = sysctl_sched_min_bal_int_shares;
                else if (timeout < sysctl_sched_max_bal_int_shares)
                        timeout *= 2;

                msleep_interruptible(timeout);
        }

        return 0;
}
#endif  /* CONFIG_SMP */

/* allocate runqueue etc for a new task group */
struct task_group *sched_create_group(void)
{
        struct task_group *tg;
        struct cfs_rq *cfs_rq;
        struct sched_entity *se;
        struct rq *rq;
        int i;

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

        tg->cfs_rq = kzalloc(sizeof(cfs_rq) * NR_CPUS, GFP_KERNEL);
        if (!tg->cfs_rq)
                goto err;
        tg->se = kzalloc(sizeof(se) * NR_CPUS, GFP_KERNEL);
        if (!tg->se)
                goto err;

        for_each_possible_cpu(i) {
                rq = cpu_rq(i);

                cfs_rq = kmalloc_node(sizeof(struct cfs_rq), GFP_KERNEL,
                                                         cpu_to_node(i));
                if (!cfs_rq)
                        goto err;

                se = kmalloc_node(sizeof(struct sched_entity), GFP_KERNEL,
                                                        cpu_to_node(i));
                if (!se)
                        goto err;

                memset(cfs_rq, 0, sizeof(struct cfs_rq));
                memset(se, 0, sizeof(struct sched_entity));

                tg->cfs_rq[i] = cfs_rq;
                init_cfs_rq(cfs_rq, rq);
                cfs_rq->tg = tg;

                tg->se[i] = se;
                se->cfs_rq = &rq->cfs;
                se->my_q = cfs_rq;
                se->load.weight = NICE_0_LOAD;
                se->load.inv_weight = div64_64(1ULL<<32, NICE_0_LOAD);
                se->parent = NULL;
        }

        tg->shares = NICE_0_LOAD;

        lock_task_group_list();
        for_each_possible_cpu(i) {
                rq = cpu_rq(i);
                cfs_rq = tg->cfs_rq[i];
                list_add_rcu(&cfs_rq->leaf_cfs_rq_list, &rq->leaf_cfs_rq_list);
        }
        unlock_task_group_list();

        return tg;

err:
        for_each_possible_cpu(i) {
                if (tg->cfs_rq)
                        kfree(tg->cfs_rq[i]);
                if (tg->se)
                        kfree(tg->se[i]);
        }
        kfree(tg->cfs_rq);
        kfree(tg->se);
        kfree(tg);

        return ERR_PTR(-ENOMEM);
}

/* rcu callback to free various structures associated with a task group */
static void free_sched_group(struct rcu_head *rhp)
{
        struct task_group *tg = container_of(rhp, struct task_group, rcu);
        struct cfs_rq *cfs_rq;
        struct sched_entity *se;
        int i;

        /* now it should be safe to free those cfs_rqs */
        for_each_possible_cpu(i) {
                cfs_rq = tg->cfs_rq[i];
                kfree(cfs_rq);

                se = tg->se[i];
                kfree(se);
        }

        kfree(tg->cfs_rq);
        kfree(tg->se);
        kfree(tg);
}

/* Destroy runqueue etc associated with a task group */
void sched_destroy_group(struct task_group *tg)
{
        struct cfs_rq *cfs_rq = NULL;
        int i;

        lock_task_group_list();
        for_each_possible_cpu(i) {
                cfs_rq = tg->cfs_rq[i];
                list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
        }
        unlock_task_group_list();

        BUG_ON(!cfs_rq);

        /* wait for possible concurrent references to cfs_rqs complete */
        call_rcu(&tg->rcu, free_sched_group);
}

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

        rq = task_rq_lock(tsk, &flags);

        if (tsk->sched_class != &fair_sched_class) {
                set_task_cfs_rq(tsk, task_cpu(tsk));
                goto done;
        }

        update_rq_clock(rq);

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

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

        set_task_cfs_rq(tsk, task_cpu(tsk));

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

done:
        task_rq_unlock(rq, &flags);
}

/* rq->lock to be locked by caller */
static void set_se_shares(struct sched_entity *se, unsigned long shares)
{
        struct cfs_rq *cfs_rq = se->cfs_rq;
        struct rq *rq = cfs_rq->rq;
        int on_rq;

        if (!shares)
                shares = MIN_GROUP_SHARES;

        on_rq = se->on_rq;
        if (on_rq) {
                dequeue_entity(cfs_rq, se, 0);
                dec_cpu_load(rq, se->load.weight);
        }

        se->load.weight = shares;
        se->load.inv_weight = div64_64((1ULL<<32), shares);

        if (on_rq) {
                enqueue_entity(cfs_rq, se, 0);
                inc_cpu_load(rq, se->load.weight);
        }
}

int sched_group_set_shares(struct task_group *tg, unsigned long shares)
{
        int i;
        struct cfs_rq *cfs_rq;
        struct rq *rq;

        lock_task_group_list();
        if (tg->shares == shares)
                goto done;

        if (shares < MIN_GROUP_SHARES)
                shares = MIN_GROUP_SHARES;

        /*
         * Prevent any load balance activity (rebalance_shares,
         * load_balance_fair) from referring to this group first,
         * by taking it off the rq->leaf_cfs_rq_list on each cpu.
         */
        for_each_possible_cpu(i) {
                cfs_rq = tg->cfs_rq[i];
                list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
        }

        /* wait for any ongoing reference to this group to finish */
        synchronize_sched();

        /*
         * Now we are free to modify the group's share on each cpu
         * w/o tripping rebalance_share or load_balance_fair.
         */
        tg->shares = shares;
        for_each_possible_cpu(i) {
                spin_lock_irq(&cpu_rq(i)->lock);
                set_se_shares(tg->se[i], shares);
                spin_unlock_irq(&cpu_rq(i)->lock);
        }

        /*
         * Enable load balance activity on this group, by inserting it back on
         * each cpu's rq->leaf_cfs_rq_list.
         */
        for_each_possible_cpu(i) {
                rq = cpu_rq(i);
                cfs_rq = tg->cfs_rq[i];
                list_add_rcu(&cfs_rq->leaf_cfs_rq_list, &rq->leaf_cfs_rq_list);
        }
done:
        unlock_task_group_list();
        return 0;
}

unsigned long sched_group_shares(struct task_group *tg)
{
        return tg->shares;
}

#endif  /* CONFIG_FAIR_GROUP_SCHED */

#ifdef CONFIG_FAIR_CGROUP_SCHED

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

static struct cgroup_subsys_state *
cpu_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cgrp)
{
        struct task_group *tg;

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

        /* we support only 1-level deep hierarchical scheduler atm */
        if (cgrp->parent->parent)
                return ERR_PTR(-EINVAL);

        tg = sched_create_group();
        if (IS_ERR(tg))
                return ERR_PTR(-ENOMEM);

        /* Bind the cgroup to task_group object we just created */
        tg->css.cgroup = cgrp;

        return &tg->css;
}

static void
cpu_cgroup_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp)
{
        struct task_group *tg = cgroup_tg(cgrp);

        sched_destroy_group(tg);
}

static int
cpu_cgroup_can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
                      struct task_struct *tsk)
{
        /* We don't support RT-tasks being in separate groups */
        if (tsk->sched_class != &fair_sched_class)
                return -EINVAL;

        return 0;
}

static void
cpu_cgroup_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
                        struct cgroup *old_cont, struct task_struct *tsk)
{
        sched_move_task(tsk);
}

static int cpu_shares_write_uint(struct cgroup *cgrp, struct cftype *cftype,
                                u64 shareval)
{
        return sched_group_set_shares(cgroup_tg(cgrp), shareval);
}

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

        return (u64) tg->shares;
}

static struct cftype cpu_files[] = {
        {
                .name = "shares",
                .read_uint = cpu_shares_read_uint,
                .write_uint = cpu_shares_write_uint,
        },
};

static int cpu_cgroup_populate(struct cgroup_subsys *ss, struct cgroup *cont)
{
        return cgroup_add_files(cont, ss, cpu_files, ARRAY_SIZE(cpu_files));
}

struct cgroup_subsys cpu_cgroup_subsys = {
        .name           = "cpu",
        .create         = cpu_cgroup_create,
        .destroy        = cpu_cgroup_destroy,
        .can_attach     = cpu_cgroup_can_attach,
        .attach         = cpu_cgroup_attach,
        .populate       = cpu_cgroup_populate,
        .subsys_id      = cpu_cgroup_subsys_id,
        .early_init     = 1,
};

#endif  /* CONFIG_FAIR_CGROUP_SCHED */

#ifdef CONFIG_CGROUP_CPUACCT

/*
 * CPU accounting code for task groups.
 *
 * Based on the work by Paul Menage (menage@google.com) and Balbir Singh
 * (balbir@in.ibm.com).
 */

/* track cpu usage of a group of tasks */
struct cpuacct {
        struct cgroup_subsys_state css;
        /* cpuusage holds pointer to a u64-type object on every cpu */
        u64 *cpuusage;
};

struct cgroup_subsys cpuacct_subsys;

/* return cpu accounting group corresponding to this container */
static inline struct cpuacct *cgroup_ca(struct cgroup *cont)
{
        return container_of(cgroup_subsys_state(cont, cpuacct_subsys_id),
                            struct cpuacct, css);
}

/* return cpu accounting group to which this task belongs */
static inline struct cpuacct *task_ca(struct task_struct *tsk)
{
        return container_of(task_subsys_state(tsk, cpuacct_subsys_id),
                            struct cpuacct, css);
}

/* create a new cpu accounting group */
static struct cgroup_subsys_state *cpuacct_create(
        struct cgroup_subsys *ss, struct cgroup *cont)
{
        struct cpuacct *ca = kzalloc(sizeof(*ca), GFP_KERNEL);

        if (!ca)
                return ERR_PTR(-ENOMEM);

        ca->cpuusage = alloc_percpu(u64);
        if (!ca->cpuusage) {
                kfree(ca);
                return ERR_PTR(-ENOMEM);
        }

        return &ca->css;
}

/* destroy an existing cpu accounting group */
static void
cpuacct_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
{
        struct cpuacct *ca = cgroup_ca(cont);

        free_percpu(ca->cpuusage);
        kfree(ca);
}

/* return total cpu usage (in nanoseconds) of a group */
static u64 cpuusage_read(struct cgroup *cont, struct cftype *cft)
{
        struct cpuacct *ca = cgroup_ca(cont);
        u64 totalcpuusage = 0;
        int i;

        for_each_possible_cpu(i) {
                u64 *cpuusage = percpu_ptr(ca->cpuusage, i);

                /*
                 * Take rq->lock to make 64-bit addition safe on 32-bit
                 * platforms.
                 */
                spin_lock_irq(&cpu_rq(i)->lock);
                totalcpuusage += *cpuusage;
                spin_unlock_irq(&cpu_rq(i)->lock);
        }

        return totalcpuusage;
}

static struct cftype files[] = {
        {
                .name = "usage",
                .read_uint = cpuusage_read,
        },
};

static int cpuacct_populate(struct cgroup_subsys *ss, struct cgroup *cont)
{
        return cgroup_add_files(cont, ss, files, ARRAY_SIZE(files));
}

/*
 * charge this task's execution time to its accounting group.
 *
 * called with rq->lock held.
 */
static void cpuacct_charge(struct task_struct *tsk, u64 cputime)
{
        struct cpuacct *ca;

        if (!cpuacct_subsys.active)
                return;

        ca = task_ca(tsk);
        if (ca) {
                u64 *cpuusage = percpu_ptr(ca->cpuusage, task_cpu(tsk));

                *cpuusage += cputime;
        }
}

struct cgroup_subsys cpuacct_subsys = {
        .name = "cpuacct",
        .create = cpuacct_create,
        .destroy = cpuacct_destroy,
        .populate = cpuacct_populate,
        .subsys_id = cpuacct_subsys_id,
};
#endif  /* CONFIG_CGROUP_CPUACCT */