kernel/sched.c

/*
 *  kernel/sched.c
 *
 *  Kernel scheduler and related syscalls
 *
 *  Copyright (C) 1991-2002  Linus Torvalds
 *
 *  1996-12-23  Modified by Dave Grothe to fix bugs in semaphores and
 *		make semaphores SMP safe
 *  1998-11-19	Implemented schedule_timeout() and related stuff
 *		by Andrea Arcangeli
 *  2002-01-04	New ultra-scalable O(1) scheduler by Ingo Molnar:
 *		hybrid priority-list and round-robin design with
 *		an array-switch method of distributing timeslices
 *		and per-CPU runqueues.  Cleanups and useful suggestions
 *		by Davide Libenzi, preemptible kernel bits by Robert Love.
 *  2003-09-03	Interactivity tuning by Con Kolivas.
 *  2004-04-02	Scheduler domains code by Nick Piggin
 */

#include <linux/mm.h>
#include <linux/module.h>
#include <linux/nmi.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <linux/highmem.h>
#include <linux/smp_lock.h>
#include <asm/mmu_context.h>
#include <linux/interrupt.h>
#include <linux/capability.h>
#include <linux/completion.h>
#include <linux/kernel_stat.h>
#include <linux/security.h>
#include <linux/notifier.h>
#include <linux/profile.h>
#include <linux/suspend.h>
#include <linux/vmalloc.h>
#include <linux/blkdev.h>
#include <linux/delay.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/syscalls.h>
#include <linux/times.h>
#include <linux/acct.h>
#include <asm/tlb.h>

#include <asm/unistd.h>

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

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

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

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

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

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

#define GRANULARITY	(10 * HZ / 1000 ? : 1)

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

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

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

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

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

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

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

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

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

void __put_task_struct_cb(struct rcu_head *rhp)
{
	__put_task_struct(container_of(rhp, struct task_struct, rcu));
}

EXPORT_SYMBOL_GPL(__put_task_struct_cb);

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

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

typedef struct runqueue runqueue_t;

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

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

	/*
	 * nr_running and cpu_load should be in the same cacheline because
	 * remote CPUs use both these fields when doing load calculation.
	 */
	unsigned long nr_running;
#ifdef CONFIG_SMP
	unsigned long prio_bias;
	unsigned long cpu_load[3];
#endif
	unsigned long long nr_switches;

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

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

#ifdef CONFIG_SMP
	struct sched_domain *sd;

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

	task_t *migration_thread;
	struct list_head migration_queue;
#endif

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

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

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

	/* try_to_wake_up() stats */
	unsigned long ttwu_cnt;
	unsigned long ttwu_local;
#endif
};

static DEFINE_PER_CPU(struct runqueue, runqueues);

/*
 * 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, domain) \
for (domain = rcu_dereference(cpu_rq(cpu)->sd); domain; domain = domain->parent)

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

#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

#ifndef __ARCH_WANT_UNLOCKED_CTXSW
static inline int task_running(runqueue_t *rq, task_t *p)
{
	return rq->curr == p;
}

static inline void prepare_lock_switch(runqueue_t *rq, task_t *next)
{
}

static inline void finish_lock_switch(runqueue_t *rq, task_t *prev)
{
#ifdef CONFIG_DEBUG_SPINLOCK
	/* this is a valid case when another task releases the spinlock */
	rq->lock.owner = current;
#endif
	spin_unlock_irq(&rq->lock);
}

#else /* __ARCH_WANT_UNLOCKED_CTXSW */
static inline int task_running(runqueue_t *rq, task_t *p)
{
#ifdef CONFIG_SMP
	return p->oncpu;
#else
	return rq->curr == p;
#endif
}

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

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

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

#ifdef CONFIG_SCHEDSTATS
/*
 * bump this up when changing the output format or the meaning of an existing
 * format, so that tools can adapt (or abort)
 */
#define SCHEDSTAT_VERSION 12

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

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

		/* runqueue-specific stats */
		seq_printf(seq,
		    "cpu%d %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu",
		    cpu, rq->yld_both_empty,
		    rq->yld_act_empty, rq->yld_exp_empty, rq->yld_cnt,
		    rq->sched_switch, rq->sched_cnt, rq->sched_goidle,
		    rq->ttwu_cnt, rq->ttwu_local,
		    rq->rq_sched_info.cpu_time,
		    rq->rq_sched_info.run_delay, rq->rq_sched_info.pcnt);

		seq_printf(seq, "\n");

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

			cpumask_scnprintf(mask_str, NR_CPUS, sd->span);
			seq_printf(seq, "domain%d %s", dcnt++, mask_str);
			for (itype = SCHED_IDLE; itype < MAX_IDLE_TYPES;
					itype++) {
				seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu %lu",
				    sd->lb_cnt[itype],
				    sd->lb_balanced[itype],
				    sd->lb_failed[itype],
				    sd->lb_imbalance[itype],
				    sd->lb_gained[itype],
				    sd->lb_hot_gained[itype],
				    sd->lb_nobusyq[itype],
				    sd->lb_nobusyg[itype]);
			}
			seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu\n",
			    sd->alb_cnt, sd->alb_failed, sd->alb_pushed,
			    sd->sbe_cnt, sd->sbe_balanced, sd->sbe_pushed,
			    sd->sbf_cnt, sd->sbf_balanced, sd->sbf_pushed,
			    sd->ttwu_wake_remote, sd->ttwu_move_affine, sd->ttwu_move_balance);
		}
		preempt_enable();
#endif
	}
	return 0;
}

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

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

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

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

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

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

	return rq;
}

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

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

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

	if (!rq)
		return;

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

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

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

	t->sched_info.cpu_time += diff;

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

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

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

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

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

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

/*
 * Put task to the end of the run list without the overhead of dequeue
 * followed by enqueue.
 */
static void requeue_task(struct task_struct *p, prio_array_t *array)
{
	list_move_tail(&p->run_list, array->queue + p->prio);
}

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

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

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

	bonus = CURRENT_BONUS(p) - MAX_BONUS / 2;

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

#ifdef CONFIG_SMP
static inline void inc_prio_bias(runqueue_t *rq, int prio)
{
	rq->prio_bias += MAX_PRIO - prio;
}

static inline void dec_prio_bias(runqueue_t *rq, int prio)
{
	rq->prio_bias -= MAX_PRIO - prio;
}

static inline void inc_nr_running(task_t *p, runqueue_t *rq)
{
	rq->nr_running++;
	if (rt_task(p)) {
		if (p != rq->migration_thread)
			/*
			 * The migration thread does the actual balancing. Do
			 * not bias by its priority as the ultra high priority
			 * will skew balancing adversely.
			 */
			inc_prio_bias(rq, p->prio);
	} else
		inc_prio_bias(rq, p->static_prio);
}

static inline void dec_nr_running(task_t *p, runqueue_t *rq)
{
	rq->nr_running--;
	if (rt_task(p)) {
		if (p != rq->migration_thread)
			dec_prio_bias(rq, p->prio);
	} else
		dec_prio_bias(rq, p->static_prio);
}
#else
static inline void inc_prio_bias(runqueue_t *rq, int prio)
{
}

static inline void dec_prio_bias(runqueue_t *rq, int prio)
{
}

static inline void inc_nr_running(task_t *p, runqueue_t *rq)
{
	rq->nr_running++;
}

static inline void dec_nr_running(task_t *p, runqueue_t *rq)
{
	rq->nr_running--;
}
#endif

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

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

static int recalc_task_prio(task_t *p, unsigned long long now)
{
	/* Caller must always ensure 'now >= p->timestamp' */
	unsigned long long __sleep_time = now - p->timestamp;
	unsigned long sleep_time;

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

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

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

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

			if (p->sleep_avg > NS_MAX_SLEEP_AVG)
				p->sleep_avg = NS_MAX_SLEEP_AVG;
		}
	}

	return effective_prio(p);
}

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

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

	if (!rt_task(p))
		p->prio = recalc_task_prio(p, now);

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

	__activate_task(p, rq);
}

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

/*
 * resched_task - mark a task 'to be rescheduled now'.
 *
 * On UP this means the setting of the need_resched flag, on SMP it
 * might also involve a cross-CPU call to trigger the scheduler on
 * the target CPU.
 */
#ifdef CONFIG_SMP
static void resched_task(task_t *p)
{
	int cpu;

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

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

	set_tsk_thread_flag(p, TIF_NEED_RESCHED);

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

	/* NEED_RESCHED must be visible before we test POLLING_NRFLAG */
	smp_mb();
	if (!test_tsk_thread_flag(p, TIF_POLLING_NRFLAG))
		smp_send_reschedule(cpu);
}
#else
static inline void resched_task(task_t *p)
{
	assert_spin_locked(&task_rq(p)->lock);
	set_tsk_need_resched(p);
}
#endif

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

#ifdef CONFIG_SMP
typedef struct {
	struct list_head list;

	task_t *task;
	int dest_cpu;

	struct completion done;
} migration_req_t;

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

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

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

/*
 * wait_task_inactive - wait for a thread to unschedule.
 *
 * The caller must ensure that the task *will* unschedule sometime soon,
 * else this function might spin for a *long* time. This function can't
 * be called with interrupts off, or it may introduce deadlock with
 * smp_call_function() if an IPI is sent by the same process we are
 * waiting to become inactive.
 */
void wait_task_inactive(task_t *p)
{
	unsigned long flags;
	runqueue_t *rq;
	int preempted;

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

/***
 * kick_process - kick a running thread to enter/exit the kernel
 * @p: the to-be-kicked thread
 *
 * Cause a process which is running on another CPU to enter
 * kernel-mode, without any delay. (to get signals handled.)
 *
 * 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(task_t *p)
{
	int cpu;

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

/*
 * Return a low guess at the load of a migration-source cpu.
 *
 * We want to under-estimate the load of migration sources, to
 * balance conservatively.
 */
static inline unsigned long __source_load(int cpu, int type, enum idle_type idle)
{
	runqueue_t *rq = cpu_rq(cpu);
	unsigned long running = rq->nr_running;
	unsigned long source_load, cpu_load = rq->cpu_load[type-1],
		load_now = running * SCHED_LOAD_SCALE;

	if (type == 0)
		source_load = load_now;
	else
		source_load = min(cpu_load, load_now);

	if (running > 1 || (idle == NOT_IDLE && running))
		/*
		 * If we are busy rebalancing the load is biased by
		 * priority to create 'nice' support across cpus. When
		 * idle rebalancing we should only bias the source_load if
		 * there is more than one task running on that queue to
		 * prevent idle rebalance from trying to pull tasks from a
		 * queue with only one running task.
		 */
		source_load = source_load * rq->prio_bias / running;

	return source_load;
}

static inline unsigned long source_load(int cpu, int type)
{
	return __source_load(cpu, type, NOT_IDLE);
}

/*
 * Return a high guess at the load of a migration-target cpu
 */
static inline unsigned long __target_load(int cpu, int type, enum idle_type idle)
{
	runqueue_t *rq = cpu_rq(cpu);
	unsigned long running = rq->nr_running;
	unsigned long target_load, cpu_load = rq->cpu_load[type-1],
		load_now = running * SCHED_LOAD_SCALE;

	if (type == 0)
		target_load = load_now;
	else
		target_load = max(cpu_load, load_now);

	if (running > 1 || (idle == NOT_IDLE && running))
		target_load = target_load * rq->prio_bias / running;

	return target_load;
}

static inline unsigned long target_load(int cpu, int type)
{
	return __target_load(cpu, type, NOT_IDLE);
}

/*
 * 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))
			goto nextgroup;

		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 = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;

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

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

/*
 * find_idlest_queue - find the idlest runqueue 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 = source_load(i, 0);

		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 (tmp->flags & flag)
			sd = tmp;

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

		span = sd->span;
		group = find_idlest_group(sd, t, cpu);
		if (!group)
			goto nextlevel;

		new_cpu = find_idlest_cpu(group, t, cpu);
		if (new_cpu == -1 || new_cpu == cpu)
			goto nextlevel;

		/* Now try balancing at a lower domain level */
		cpu = new_cpu;
nextlevel:
		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 */

/*
 * wake_idle() will wake a task on an idle cpu if task->cpu is
 * not idle and an idle cpu is available.  The span of cpus to
 * search starts with cpus closest then further out as needed,
 * so we always favor a closer, idle cpu.
 *
 * Returns the CPU we should wake onto.
 */
#if defined(ARCH_HAS_SCHED_WAKE_IDLE)
static int wake_idle(int cpu, task_t *p)
{
	cpumask_t tmp;
	struct sched_domain *sd;
	int i;

	if (idle_cpu(cpu))
		return cpu;

	for_each_domain(cpu, sd) {
		if (sd->flags & SD_WAKE_IDLE) {
			cpus_and(tmp, sd->span, p->cpus_allowed);
			for_each_cpu_mask(i, tmp) {
				if (idle_cpu(i))
					return i;
			}
		}
		else
			break;
	}
	return cpu;
}
#else
static inline int wake_idle(int cpu, task_t *p)
{
	return cpu;
}
#endif

/***
 * try_to_wake_up - wake up a thread
 * @p: the to-be-woken-up thread
 * @state: the mask of task states that can be woken
 * @sync: do a synchronous wakeup?
 *
 * Put it on the run-queue if it's not already there. The "current"
 * thread is always on the run-queue (except when the actual
 * re-schedule is in progress), and as such you're allowed to do
 * the simpler "current->state = TASK_RUNNING" to mark yourself
 * runnable without the overhead of this.
 *
 * returns failure only if the task is already active.
 */
static int try_to_wake_up(task_t *p, unsigned int state, int sync)
{
	int cpu, this_cpu, success = 0;
	unsigned long flags;
	long old_state;
	runqueue_t *rq;
#ifdef CONFIG_SMP
	unsigned long load, this_load;
	struct sched_domain *sd, *this_sd = NULL;
	int new_cpu;
#endif

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

	if (p->array)
		goto out_running;

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

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

	new_cpu = cpu;

	schedstat_inc(rq, ttwu_cnt);
	if (cpu == this_cpu) {
		schedstat_inc(rq, ttwu_local);
		goto out_set_cpu;
	}

	for_each_domain(this_cpu, sd) {
		if (cpu_isset(cpu, sd->span)) {
			schedstat_inc(sd, ttwu_wake_remote);
			this_sd = sd;
			break;
		}
	}

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

	/*
	 * Check for affine wakeup and passive balancing possibilities.
	 */
	if (this_sd) {
		int idx = this_sd->wake_idx;
		unsigned int imbalance;

		imbalance = 100 + (this_sd->imbalance_pct - 100) / 2;

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

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

		if (this_sd->flags & SD_WAKE_AFFINE) {
			unsigned long tl = this_load;
			/*
			 * If sync wakeup then subtract the (maximum possible)
			 * effect of the currently running task from the load
			 * of the current CPU:
			 */
			if (sync)
				tl -= SCHED_LOAD_SCALE;

			if ((tl <= load &&
				tl + target_load(cpu, idx) <= SCHED_LOAD_SCALE) ||
				100*(tl + SCHED_LOAD_SCALE) <= imbalance*load) {
				/*
				 * This domain has SD_WAKE_AFFINE and
				 * p is cache cold in this domain, and
				 * there is no bad imbalance.
				 */
				schedstat_inc(this_sd, ttwu_move_affine);
				goto out_set_cpu;
			}
		}

		/*
		 * Start passive balancing when half the imbalance_pct
		 * limit is reached.
		 */
		if (this_sd->flags & SD_WAKE_BALANCE) {
			if (imbalance*this_load <= 100*load) {
				schedstat_inc(this_sd, ttwu_move_balance);
				goto out_set_cpu;
			}
		}
	}

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

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

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

	/*
	 * Tasks that have marked their sleep as noninteractive get
	 * woken up without updating their sleep average. (i.e. their
	 * sleep is handled in a priority-neutral manner, no priority
	 * boost and no penalty.)
	 */
	if (old_state & TASK_NONINTERACTIVE)
		__activate_task(p, rq);
	else
		activate_task(p, rq, cpu == this_cpu);
	/*
	 * Sync wakeups (i.e. those types of wakeups where the waker
	 * has indicated that it will leave the CPU in short order)
	 * don't trigger a preemption, if the woken up task will run on
	 * this cpu. (in this case the 'I will reschedule' promise of
	 * the waker guarantees that the freshly woken up task is going
	 * to be considered on this CPU.)
	 */
	if (!sync || cpu != this_cpu) {
		if (TASK_PREEMPTS_CURR(p, rq))
			resched_task(rq->curr);
	}
	success = 1;

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

	return success;
}

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

EXPORT_SYMBOL(wake_up_process);

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

/*
 * Perform scheduler related setup for a newly forked process p.
 * p is forked by current.
 */
void fastcall sched_fork(task_t *p, int clone_flags)
{
	int cpu = get_cpu();

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

	/*
	 * We mark the process as running here, but have not actually
	 * inserted it onto the runqueue yet. This guarantees that
	 * nobody will actually run it, and a signal or other external
	 * event cannot wake it up and insert it on the runqueue either.
	 */
	p->state = TASK_RUNNING;
	INIT_LIST_HEAD(&p->run_list);
	p->array = NULL;
#ifdef CONFIG_SCHEDSTATS
	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
	/*
	 * Share the timeslice between parent and child, thus the
	 * total amount of pending timeslices in the system doesn't change,
	 * resulting in more scheduling fairness.
	 */
	local_irq_disable();
	p->time_slice = (current->time_slice + 1) >> 1;
	/*
	 * The remainder of the first timeslice might be recovered by
	 * the parent if the child exits early enough.
	 */
	p->first_time_slice = 1;
	current->time_slice >>= 1;
	p->timestamp = sched_clock();
	if (unlikely(!current->time_slice)) {
		/*
		 * This case is rare, it happens when the parent has only
		 * a single jiffy left from its timeslice. Taking the
		 * runqueue lock is not a problem.
		 */
		current->time_slice = 1;
		scheduler_tick();
	}
	local_irq_enable();
	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(task_t *p, unsigned long clone_flags)
{
	unsigned long flags;
	int this_cpu, cpu;
	runqueue_t *rq, *this_rq;

	rq = task_rq_lock(p, &flags);
	BUG_ON(p->state != TASK_RUNNING);
	this_cpu = smp_processor_id();
	cpu = task_cpu(p);

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

	p->prio = effective_prio(p);

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

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

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

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

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

/**
 * prepare_task_switch - prepare to switch tasks
 * @rq: the runqueue preparing to switch
 * @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(runqueue_t *rq, task_t *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 inline void finish_task_switch(runqueue_t *rq, task_t *prev)
	__releases(rq->lock)
{
	struct mm_struct *mm = rq->prev_mm;
	unsigned long prev_task_flags;

	rq->prev_mm = NULL;

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

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

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

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

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

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

	return prev;
}

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

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

	return sum;
}

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

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

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

	return sum;
}

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

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

	return sum;
}

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

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

	return sum;
}

#ifdef CONFIG_SMP

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

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

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

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

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

	/* 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 inline
void pull_task(runqueue_t *src_rq, prio_array_t *src_array, task_t *p,
	       runqueue_t *this_rq, prio_array_t *this_array, int this_cpu)
{
	dequeue_task(p, src_array);
	dec_nr_running(p, src_rq);
	set_task_cpu(p, this_cpu);
	inc_nr_running(p, this_rq);
	enqueue_task(p, this_array);
	p->timestamp = (p->timestamp - src_rq->timestamp_last_tick)
				+ this_rq->timestamp_last_tick;
	/*
	 * Note that idle threads have a prio of MAX_PRIO, for this test
	 * to be always true for them.
	 */
	if (TASK_PREEMPTS_CURR(p, this_rq))
		resched_task(this_rq->curr);
}

/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static inline
int can_migrate_task(task_t *p, runqueue_t *rq, int this_cpu,
		     struct sched_domain *sd, enum idle_type idle,
		     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))
		return 0;
	*all_pinned = 0;

	if (task_running(rq, p))
		return 0;

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

	if (sd->nr_balance_failed > sd->cache_nice_tries)
		return 1;

	if (task_hot(p, rq->timestamp_last_tick, sd))
		return 0;
	return 1;
}

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

	if (max_nr_move == 0)
		goto out;

	pinned = 1;

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

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

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

	curr = curr->prev;

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

#ifdef CONFIG_SCHEDSTATS
	if (task_hot(tmp, busiest->timestamp_last_tick, sd))
		schedstat_inc(sd, lb_hot_gained[idle]);
#endif

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

	/* We only want to steal up to the prescribed number of tasks. */
	if (pulled < max_nr_move) {
		if (curr != head)
			goto skip_queue;
		idx++;
		goto skip_bitmap;
	}
out:
	/*
	 * Right now, this is the only place pull_task() is called,
	 * so we can safely collect pull_task() stats here rather than
	 * inside pull_task().
	 */
	schedstat_add(sd, lb_gained[idle], pulled);

	if (all_pinned)
		*all_pinned = pinned;
	return pulled;
}

/*
 * find_busiest_group finds and returns the busiest CPU group within the
 * domain. It calculates and returns the number of tasks which should be
 * moved to restore balance via the imbalance parameter.
 */
static struct sched_group *
find_busiest_group(struct sched_domain *sd, int this_cpu,
		   unsigned long *imbalance, enum idle_type idle, int *sd_idle)
{
	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;
	int load_idx;

	max_load = this_load = total_load = total_pwr = 0;
	if (idle == NOT_IDLE)
		load_idx = sd->busy_idx;
	else if (idle == NEWLY_IDLE)
		load_idx = sd->newidle_idx;
	else
		load_idx = sd->idle_idx;

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

		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) {
			if (*sd_idle && !idle_cpu(i))
				*sd_idle = 0;

			/* Bias balancing toward cpus of our domain */
			if (local_group)
				load = __target_load(i, load_idx, idle);
			else
				load = __source_load(i, load_idx, idle);

			avg_load += load;
		}

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

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

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

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

	avg_load = (SCHED_LOAD_SCALE * total_load) / total_pwr;

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

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

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

	/* 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 < SCHED_LOAD_SCALE) {
		unsigned long pwr_now = 0, pwr_move = 0;
		unsigned long tmp;

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

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

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

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

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

		/* Move if we gain throughput */
		if (pwr_move <= pwr_now)
			goto out_balanced;

		*imbalance = 1;
		return busiest;
	}

	/* Get rid of the scaling factor, rounding down as we divide */
	*imbalance = *imbalance / SCHED_LOAD_SCALE;
	return busiest;

out_balanced:

	*imbalance = 0;
	return NULL;
}

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

	for_each_cpu_mask(i, group->cpumask) {
		load = __source_load(i, 0, idle);

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

	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.
 *
 * Called with this_rq unlocked.
 */
static int load_balance(int this_cpu, runqueue_t *this_rq,
			struct sched_domain *sd, enum idle_type idle)
{
	struct sched_group *group;
	runqueue_t *busiest;
	unsigned long imbalance;
	int nr_moved, all_pinned = 0;
	int active_balance = 0;
	int sd_idle = 0;

	if (idle != NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER)
		sd_idle = 1;

	schedstat_inc(sd, lb_cnt[idle]);

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

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

	BUG_ON(busiest == this_rq);

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

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

		/* All tasks on this runqueue were pinned by CPU affinity */
		if (unlikely(all_pinned))
			goto out_balanced;
	}

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

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

			spin_lock(&busiest->lock);

			/* 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(&busiest->lock);
				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(&busiest->lock);
			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 (!nr_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER)
		return -1;
	return nr_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)
		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 (NEWLY_IDLE).
 * this_rq is locked.
 */
static int load_balance_newidle(int this_cpu, runqueue_t *this_rq,
				struct sched_domain *sd)
{
	struct sched_group *group;
	runqueue_t *busiest = NULL;
	unsigned long imbalance;
	int nr_moved = 0;
	int sd_idle = 0;

	if (sd->flags & SD_SHARE_CPUPOWER)
		sd_idle = 1;

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

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

	BUG_ON(busiest == this_rq);

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

	nr_moved = 0;
	if (busiest->nr_running > 1) {
		/* Attempt to move tasks */
		double_lock_balance(this_rq, busiest);
		nr_moved = move_tasks(this_rq, this_cpu, busiest,
					imbalance, sd, NEWLY_IDLE, NULL);
		spin_unlock(&busiest->lock);
	}

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

	return nr_moved;

out_balanced:
	schedstat_inc(sd, lb_balanced[NEWLY_IDLE]);
	if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER)
		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 inline void idle_balance(int this_cpu, runqueue_t *this_rq)
{
	struct sched_domain *sd;

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

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

	if (busiest_rq->nr_running <= 1)
		/* no task to move */
		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);

	/* 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 (unlikely(sd == NULL))
		goto out;

	schedstat_inc(sd, alb_cnt);

	if (move_tasks(target_rq, target_cpu, busiest_rq, 1, sd, SCHED_IDLE, NULL))
		schedstat_inc(sd, alb_pushed);
	else
		schedstat_inc(sd, alb_failed);
out:
	spin_unlock(&target_rq->lock);
}

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

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

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

	this_load = this_rq->nr_running * SCHED_LOAD_SCALE;
	/* Update our load */
	for (i = 0; i < 3; i++) {
		unsigned long new_load = this_load;
		int scale = 1 << i;
		old_load = this_rq->cpu_load[i];
		/*
		 * 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) / scale;
	}

	for_each_domain(this_cpu, sd) {
		unsigned long interval;

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

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

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

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

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

DEFINE_PER_CPU(struct kernel_stat, kstat);

EXPORT_PER_CPU_SYMBOL(kstat);

/*
 * This is called on clock ticks and on context switches.
 * Bank in p->sched_time the ns elapsed since the last tick or switch.
 */
static inline void update_cpu_clock(task_t *p, runqueue_t *rq,
				    unsigned long long now)
{
	unsigned long long last = max(p->timestamp, rq->timestamp_last_tick);
	p->sched_time += now - last;
}

/*
 * Return current->sched_time plus any more ns on the sched_clock
 * that have not yet been banked.
 */
unsigned long long current_sched_time(const task_t *tsk)
{
	unsigned long long ns;
	unsigned long flags;
	local_irq_save(flags);
	ns = max(tsk->timestamp, task_rq(tsk)->timestamp_last_tick);
	ns = tsk->sched_time + (sched_clock() - ns);
	local_irq_restore(flags);
	return ns;
}

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

/*
 * Account user 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 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 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;
	runqueue_t *rq = this_rq();
	cputime64_t tmp;

	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 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);
	runqueue_t *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();
	runqueue_t *rq = this_rq();
	task_t *p = current;
	unsigned long long now = sched_clock();

	update_cpu_clock(p, rq, now);

	rq->timestamp_last_tick = now;

	if (p == rq->idle) {
		if (wake_priority_sleeper(rq))
			goto out;
		rebalance_tick(cpu, rq, SCHED_IDLE);
		return;
	}

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

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

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

			requeue_task(p, rq->active);
			set_tsk_need_resched(p);
		}
	}
out_unlock:
	spin_unlock(&rq->lock);
out:
	rebalance_tick(cpu, rq, NOT_IDLE);
}

#ifdef CONFIG_SCHED_SMT
static inline void wakeup_busy_runqueue(runqueue_t *rq)
{
	/* If an SMT runqueue is sleeping due to priority reasons wake it up */
	if (rq->curr == rq->idle && rq->nr_running)
		resched_task(rq->idle);
}

static inline void wake_sleeping_dependent(int this_cpu, runqueue_t *this_rq)
{
	struct sched_domain *tmp, *sd = NULL;
	cpumask_t sibling_map;
	int i;

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

	if (!sd)
		return;

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

	sibling_map = sd->span;

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

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

		wakeup_busy_runqueue(smt_rq);
	}

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

/*
 * number of 'lost' timeslices this task wont be able to fully
 * utilize, if another task runs on a sibling. This models the
 * slowdown effect of other tasks running on siblings:
 */
static inline unsigned long smt_slice(task_t *p, struct sched_domain *sd)
{
	return p->time_slice * (100 - sd->per_cpu_gain) / 100;
}

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

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

	if (!sd)
		return 0;

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

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

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

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

		/* Kernel threads do not participate in dependent sleeping */
		if (!p->mm || !smt_curr->mm || rt_task(p))
			goto check_smt_task;

		/*
		 * If a user task with lower static priority than the
		 * running task on the SMT sibling is trying to schedule,
		 * delay it till there is proportionately less timeslice
		 * left of the sibling task to prevent a lower priority
		 * task from using an unfair proportion of the
		 * physical cpu's resources. -ck
		 */
		if (rt_task(smt_curr)) {
			/*
			 * With real time tasks we run non-rt tasks only
			 * per_cpu_gain% of the time.
			 */
			if ((jiffies % DEF_TIMESLICE) >
				(sd->per_cpu_gain * DEF_TIMESLICE / 100))
					ret = 1;
		} else
			if (smt_curr->static_prio < p->static_prio &&
				!TASK_PREEMPTS_CURR(p, smt_rq) &&
				smt_slice(smt_curr, sd) > task_timeslice(p))
					ret = 1;

check_smt_task:
		if ((!smt_curr->mm && smt_curr != smt_rq->idle) ||
			rt_task(smt_curr))
				continue;
		if (!p->mm) {
			wakeup_busy_runqueue(smt_rq);
			continue;
		}

		/*
		 * Reschedule a lower priority task on the SMT sibling for
		 * it to be put to sleep, or wake it up if it has been put to
		 * sleep for priority reasons to see if it should run now.
		 */
		if (rt_task(p)) {
			if ((jiffies % DEF_TIMESLICE) >
				(sd->per_cpu_gain * DEF_TIMESLICE / 100))
					resched_task(smt_curr);
		} else {
			if (TASK_PREEMPTS_CURR(p, smt_rq) &&
				smt_slice(p, sd) > task_timeslice(smt_curr))
					resched_task(smt_curr);
			else
				wakeup_busy_runqueue(smt_rq);
		}
	}
out_unlock:
	for_each_cpu_mask(i, sibling_map)
		spin_unlock(&cpu_rq(i)->lock);
	return ret;
}
#else
static inline void wake_sleeping_dependent(int this_cpu, runqueue_t *this_rq)
{
}

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

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

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

void fastcall sub_preempt_count(int val)
{
	/*
	 * Underflow?
	 */
	BUG_ON(val > preempt_count());
	/*
	 * Is the spinlock portion underflowing?
	 */
	BUG_ON((val < PREEMPT_MASK) && !(preempt_count() & PREEMPT_MASK));
	preempt_count() -= val;
}
EXPORT_SYMBOL(sub_preempt_count);

#endif

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

	/*
	 * Test if we are atomic.  Since do_exit() needs to call into
	 * schedule() atomically, we ignore that path for now.
	 * Otherwise, whine if we are scheduling when we should not be.
	 */
	if (likely(!current->exit_state)) {
		if (unlikely(in_atomic())) {
			printk(KERN_ERR "scheduling while atomic: "
				"%s/0x%08x/%d\n",
				current->comm, preempt_count(), current->pid);
			dump_stack();
		}
	}
	profile_hit(SCHED_PROFILING, __builtin_return_address(0));

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

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

	schedstat_inc(rq, sched_cnt);
	now = sched_clock();
	if (likely((long long)(now - prev->timestamp) < NS_MAX_SLEEP_AVG)) {
		run_time = now - prev->timestamp;
		if (unlikely((long long)(now - prev->timestamp) < 0))
			run_time = 0;
	} else
		run_time = NS_MAX_SLEEP_AVG;

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

	spin_lock_irq(&rq->lock);

	if (unlikely(prev->flags & PF_DEAD))
		prev->state = EXIT_DEAD;

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

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

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

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

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

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

		array = next->array;
		new_prio = recalc_task_prio(next, next->timestamp + delta);

		if (unlikely(next->prio != new_prio)) {
			dequeue_task(next, array);
			next->prio = new_prio;
			enqueue_task(next, array);
		} else
			requeue_task(next, array);
	}
	next->activated = 0;
switch_tasks:
	if (next == rq->idle)
		schedstat_inc(rq, sched_goidle);
	prefetch(next);
	prefetch_stack(next);
	clear_tsk_need_resched(prev);
	rcu_qsctr_inc(task_cpu(prev));

	update_cpu_clock(prev, rq, now);

	prev->sleep_avg -= run_time;
	if ((long)prev->sleep_avg <= 0)
		prev->sleep_avg = 0;
	prev->timestamp = prev->last_ran = now;

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

		prepare_task_switch(rq, next);
		prev = context_switch(rq, prev, next);
		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);
	} else
		spin_unlock_irq(&rq->lock);

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

EXPORT_SYMBOL(schedule);

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

need_resched:
	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);

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

EXPORT_SYMBOL(preempt_schedule);

/*
 * this is 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());

need_resched:
	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);

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

#endif /* CONFIG_PREEMPT */

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

EXPORT_SYMBOL(default_wake_function);

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

	list_for_each_safe(tmp, next, &q->task_list) {
		wait_queue_t *curr;
		unsigned flags;
		curr = list_entry(tmp, wait_queue_t, task_list);
		flags = curr->flags;
		if (curr->func(curr, mode, sync, key) &&
		    (flags & WQ_FLAG_EXCLUSIVE) &&
		    !--nr_exclusive)
			break;
	}
}

/**
 * __wake_up - wake up threads blocked on a waitqueue.
 * @q: the waitqueue
 * @mode: which threads
 * @nr_exclusive: how many wake-one or wake-many threads to wake up
 * @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 fastcall complete(struct completion *x)
{
	unsigned long flags;

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

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

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

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

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

unsigned long fastcall __sched
wait_for_completion_timeout(struct completion *x, unsigned long timeout)
{
	might_sleep();

	spin_lock_irq(&x->wait.lock);
	if (!x->done) {
		DECLARE_WAITQUEUE(wait, current);

		wait.flags |= WQ_FLAG_EXCLUSIVE;
		__add_wait_queue_tail(&x->wait, &wait);
		do {
			__set_current_state(TASK_UNINTERRUPTIBLE);
			spin_unlock_irq(&x->wait.lock);
			timeout = schedule_timeout(timeout);
			spin_lock_irq(&x->wait.lock);
			if (!timeout) {
				__remove_wait_queue(&x->wait, &wait);
				goto out;
			}
		} while (!x->done);
		__remove_wait_queue(&x->wait, &wait);
	}
	x->done--;
out:
	spin_unlock_irq(&x->wait.lock);
	return timeout;
}
EXPORT_SYMBOL(wait_for_completion_timeout);

int fastcall __sched wait_for_completion_interruptible(struct completion *x)
{
	int ret = 0;

	might_sleep();

	spin_lock_irq(&x->wait.lock);
	if (!x->done) {
		DECLARE_WAITQUEUE(wait, current);

		wait.flags |= WQ_FLAG_EXCLUSIVE;
		__add_wait_queue_tail(&x->wait, &wait);
		do {
			if (signal_pending(current)) {
				ret = -ERESTARTSYS;
				__remove_wait_queue(&x->wait, &wait);
				goto out;
			}
			__set_current_state(TASK_INTERRUPTIBLE);
			spin_unlock_irq(&x->wait.lock);
			schedule();
			spin_lock_irq(&x->wait.lock);
		} while (!x->done);
		__remove_wait_queue(&x->wait, &wait);
	}
	x->done--;
out:
	spin_unlock_irq(&x->wait.lock);

	return ret;
}
EXPORT_SYMBOL(wait_for_completion_interruptible);

unsigned long fastcall __sched
wait_for_completion_interruptible_timeout(struct completion *x,
					  unsigned long timeout)
{
	might_sleep();

	spin_lock_irq(&x->wait.lock);
	if (!x->done) {
		DECLARE_WAITQUEUE(wait, current);

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


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

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

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

void fastcall __sched interruptible_sleep_on(wait_queue_head_t *q)
{
	SLEEP_ON_VAR

	current->state = TASK_INTERRUPTIBLE;

	SLEEP_ON_HEAD
	schedule();
	SLEEP_ON_TAIL
}

EXPORT_SYMBOL(interruptible_sleep_on);

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

	current->state = TASK_INTERRUPTIBLE;

	SLEEP_ON_HEAD
	timeout = schedule_timeout(timeout);
	SLEEP_ON_TAIL

	return timeout;
}

EXPORT_SYMBOL(interruptible_sleep_on_timeout);

void fastcall __sched sleep_on(wait_queue_head_t *q)
{
	SLEEP_ON_VAR

	current->state = TASK_UNINTERRUPTIBLE;

	SLEEP_ON_HEAD
	schedule();
	SLEEP_ON_TAIL
}

EXPORT_SYMBOL(sleep_on);

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

	current->state = TASK_UNINTERRUPTIBLE;

	SLEEP_ON_HEAD
	timeout = schedule_timeout(timeout);
	SLEEP_ON_TAIL

	return timeout;
}

EXPORT_SYMBOL(sleep_on_timeout);

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

	if (TASK_NICE(p) == nice || nice < -20 || nice > 19)
		return;
	/*
	 * We have to be careful, if called from sys_setpriority(),
	 * the task might be in the middle of scheduling on another CPU.
	 */
	rq = task_rq_lock(p, &flags);
	/*
	 * The RT priorities are set via 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
	 * not SCHED_NORMAL:
	 */
	if (rt_task(p)) {
		p->static_prio = NICE_TO_PRIO(nice);
		goto out_unlock;
	}
	array = p->array;
	if (array) {
		dequeue_task(p, array);
		dec_prio_bias(rq, p->static_prio);
	}

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

	if (array) {
		enqueue_task(p, array);
		inc_prio_bias(rq, p->static_prio);
		/*
		 * 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 task_t *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)
{
	int retval;
	long nice;

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

/**
 * task_nice - return the nice value of a given task.
 * @p: the task in question.
 */
int task_nice(const task_t *p)
{
	return TASK_NICE(p);
}
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.
 */
task_t *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 inline task_t *find_process_by_pid(pid_t pid)
{
	return pid ? find_task_by_pid(pid) : current;
}

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

/**
 * 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.
 */
int sched_setscheduler(struct task_struct *p, int policy,
		       struct sched_param *param)
{
	int retval;
	int oldprio, oldpolicy = -1;
	prio_array_t *array;
	unsigned long flags;
	runqueue_t *rq;

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)
			return -EINVAL;
	/*
	 * Valid priorities for SCHED_FIFO and SCHED_RR are
	 * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL 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 ((policy == SCHED_NORMAL) != (param->sched_priority == 0))
		return -EINVAL;

	/*
	 * Allow unprivileged RT tasks to decrease priority:
	 */
	if (!capable(CAP_SYS_NICE)) {
		/* can't change policy */
		if (policy != p->policy &&
			!p->signal->rlim[RLIMIT_RTPRIO].rlim_cur)
			return -EPERM;
		/* can't increase priority */
		if (policy != SCHED_NORMAL &&
		    param->sched_priority > p->rt_priority &&
		    param->sched_priority >
				p->signal->rlim[RLIMIT_RTPRIO].rlim_cur)
			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;
	/*
	 * To be able to change p->policy safely, the apropriate
	 * runqueue lock must be held.
	 */
	rq = task_rq_lock(p, &flags);
	/* recheck policy now with rq lock held */
	if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
		policy = oldpolicy = -1;
		task_rq_unlock(rq, &flags);
		goto recheck;
	}
	array = p->array;
	if (array)
		deactivate_task(p, rq);
	oldprio = p->prio;
	__setscheduler(p, policy, param->sched_priority);
	if (array) {
		__activate_task(p, rq);
		/*
		 * Reschedule if we are currently running on this runqueue and
		 * our priority decreased, or if we are not currently running on
		 * this runqueue and our priority is higher than the current's
		 */
		if (task_running(rq, p)) {
			if (p->prio > oldprio)
				resched_task(rq->curr);
		} else if (TASK_PREEMPTS_CURR(p, rq))
			resched_task(rq->curr);
	}
	task_rq_unlock(rq, &flags);
	return 0;
}
EXPORT_SYMBOL_GPL(sched_setscheduler);

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

	if (!param || pid < 0)
		return -EINVAL;
	if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
		return -EFAULT;
	read_lock_irq(&tasklist_lock);
	p = find_process_by_pid(pid);
	if (!p) {
		read_unlock_irq(&tasklist_lock);
		return -ESRCH;
	}
	retval = sched_setscheduler(p, policy, &lparam);
	read_unlock_irq(&tasklist_lock);
	return retval;
}

/**
 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
 * @pid: the pid in question.
 * @policy: new policy.
 * @param: structure containing the new RT priority.
 */
asmlinkage long sys_sched_setscheduler(pid_t pid, int policy,
				       struct sched_param __user *param)
{
	return 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)
{
	int retval = -EINVAL;
	task_t *p;

	if (pid < 0)
		goto out_nounlock;

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

out_nounlock:
	return retval;
}

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

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

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

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

	lp.sched_priority = p->rt_priority;
	read_unlock(&tasklist_lock);

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

out_nounlock:
	return retval;

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

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

	lock_cpu_hotplug();
	read_lock(&tasklist_lock);

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

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

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

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

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

static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
			     cpumask_t *new_mask)
{
	if (len < sizeof(cpumask_t)) {
		memset(new_mask, 0, sizeof(cpumask_t));
	} else if (len > sizeof(cpumask_t)) {
		len = sizeof(cpumask_t);
	}
	return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
}

/**
 * sys_sched_setaffinity - set the cpu affinity of a process
 * @pid: pid of the process
 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
 * @user_mask_ptr: user-space pointer to the new cpu mask
 */
asmlinkage long sys_sched_setaffinity(pid_t pid, unsigned int len,
				      unsigned long __user *user_mask_ptr)
{
	cpumask_t new_mask;
	int retval;

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

	return sched_setaffinity(pid, new_mask);
}

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

cpumask_t cpu_present_map __read_mostly;
EXPORT_SYMBOL(cpu_present_map);

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

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

	lock_cpu_hotplug();
	read_lock(&tasklist_lock);

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

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

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

	return 0;
}

/**
 * sys_sched_getaffinity - get the cpu affinity of a process
 * @pid: pid of the process
 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
 * @user_mask_ptr: user-space pointer to hold the current cpu mask
 */
asmlinkage long sys_sched_getaffinity(pid_t pid, unsigned int len,
				      unsigned long __user *user_mask_ptr)
{
	int ret;
	cpumask_t mask;

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

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

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

	return sizeof(cpumask_t);
}

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

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

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

	if (array != target) {
		dequeue_task(current, array);
		enqueue_task(current, target);
	} else
		/*
		 * requeue_task is cheaper so perform that if possible.
		 */
		requeue_task(current, array);

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

	schedule();

	return 0;
}

static inline void __cond_resched(void)
{
	/*
	 * The BKS might be reacquired before we have dropped
	 * PREEMPT_ACTIVE, which could trigger a second
	 * cond_resched() call.
	 */
	if (unlikely(preempt_count()))
		return;
	do {
		add_preempt_count(PREEMPT_ACTIVE);
		schedule();
		sub_preempt_count(PREEMPT_ACTIVE);
	} while (need_resched());
}

int __sched cond_resched(void)
{
	if (need_resched()) {
		__cond_resched();
		return 1;
	}
	return 0;
}

EXPORT_SYMBOL(cond_resched);

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

	if (need_lockbreak(lock)) {
		spin_unlock(lock);
		cpu_relax();
		ret = 1;
		spin_lock(lock);
	}
	if (need_resched()) {
		_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()) {
		__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 runqueue *rq = &per_cpu(runqueues, raw_smp_processor_id());

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

EXPORT_SYMBOL(io_schedule);

long __sched io_schedule_timeout(long timeout)
{
	struct runqueue *rq = &per_cpu(runqueues, raw_smp_processor_id());
	long ret;

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

/**
 * sys_sched_get_priority_max - return maximum RT priority.
 * @policy: scheduling class.
 *
 * this syscall returns the maximum rt_priority that can be used
 * by a given scheduling class.
 */
asmlinkage long sys_sched_get_priority_max(int policy)
{
	int ret = -EINVAL;

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

/**
 * sys_sched_get_priority_min - return minimum RT priority.
 * @policy: scheduling class.
 *
 * this syscall returns the minimum rt_priority that can be used
 * by a given scheduling class.
 */
asmlinkage long sys_sched_get_priority_min(int policy)
{
	int ret = -EINVAL;

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

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

	if (pid < 0)
		goto out_nounlock;

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

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

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

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

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

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

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

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

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

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

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

	read_unlock(&tasklist_lock);
	mutex_debug_show_all_locks();
}

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

	idle->sleep_avg = 0;
	idle->array = NULL;
	idle->prio = MAX_PRIO;
	idle->state = TASK_RUNNING;
	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
}

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

#ifdef CONFIG_SMP
/*
 * This is how migration works:
 *
 * 1) we queue a migration_req_t structure in the source CPU's
 *    runqueue and wake up that CPU's migration thread.
 * 2) we down() the locked semaphore => thread blocks.
 * 3) migration thread wakes up (implicitly it forces the migrated
 *    thread off the CPU)
 * 4) it gets the migration request and checks whether the migrated
 *    task is still in the wrong runqueue.
 * 5) if it's in the wrong runqueue then the migration thread removes
 *    it and puts it into the right queue.
 * 6) migration thread up()s the semaphore.
 * 7) we wake up and the migration is done.
 */

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

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

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

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

EXPORT_SYMBOL_GPL(set_cpus_allowed);

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

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

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

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

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

out:
	double_rq_unlock(rq_src, rq_dest);
}

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

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

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

		try_to_freeze();

		spin_lock_irq(&rq->lock);

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

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

		head = &rq->migration_queue;

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

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

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

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

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

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

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

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

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

	write_lock_irq(&tasklist_lock);

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

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

	write_unlock_irq(&tasklist_lock);
}

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

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

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

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

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

/* 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);
}

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

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

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

	get_task_struct(tsk);

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

	put_task_struct(tsk);
}

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

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

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

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

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

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

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

#ifdef CONFIG_SMP
#undef SCHED_DOMAIN_DEBUG
#ifdef SCHED_DOMAIN_DEBUG
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);

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

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

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

		printk("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);
		for (i = 0; i < level + 2; i++)
			printk(" ");
		printk("groups:");
		do {
			if (!group) {
				printk("\n");
				printk(KERN_ERR "ERROR: group is NULL\n");
				break;
			}

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

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

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

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

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

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

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

		level++;
		sd = sd->parent;

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

	} while (sd);
}
#else
#define sched_domain_debug(sd, cpu) {}
#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)) {
		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);
	}
	if (~cflags & pflags)
		return 0;

	return 1;
}

/*
 * 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, int cpu)
{
	runqueue_t *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 (sd && sd_degenerate(sd))
		sd = sd->parent;

	sched_domain_debug(sd, cpu);

	rcu_assign_pointer(rq->sd, sd);
}

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

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

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

__setup ("isolcpus=", isolated_cpu_setup);

/*
 * init_sched_build_groups takes an array of groups, the cpumask we wish
 * to span, and a pointer to a function which identifies what group a CPU
 * belongs to. The return value of group_fn must be a valid index into the
 * groups[] array, and must be >= 0 and < NR_CPUS (due to the fact that we
 * keep track of groups covered with a cpumask_t).
 *
 * init_sched_build_groups will build a circular linked list of the groups
 * covered by the given span, and will set each group's ->cpumask correctly,
 * and ->cpu_power to 0.
 */
static void init_sched_build_groups(struct sched_group groups[], cpumask_t span,
				    int (*group_fn)(int cpu))
{
	struct sched_group *first = NULL, *last = NULL;
	cpumask_t covered = CPU_MASK_NONE;
	int i;

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

		if (cpu_isset(i, covered))
			continue;

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

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

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

#define SD_NODES_PER_DOMAIN 16

/*
 * Self-tuning task migration cost measurement between source and target CPUs.
 *
 * This is done by measuring the cost of manipulating buffers of varying
 * sizes. For a given buffer-size here are the steps that are taken:
 *
 * 1) the source CPU reads+dirties a shared buffer
 * 2) the target CPU reads+dirties the same shared buffer
 *
 * We measure how long they take, in the following 4 scenarios:
 *
 *  - source: CPU1, target: CPU2 | cost1
 *  - source: CPU2, target: CPU1 | cost2
 *  - source: CPU1, target: CPU1 | cost3
 *  - source: CPU2, target: CPU2 | cost4
 *
 * We then calculate the cost3+cost4-cost1-cost2 difference - this is
 * the cost of migration.
 *
 * We then start off from a small buffer-size and iterate up to larger
 * buffer sizes, in 5% steps - measuring each buffer-size separately, and
 * doing a maximum search for the cost. (The maximum cost for a migration
 * normally occurs when the working set size is around the effective cache
 * size.)
 */
#define SEARCH_SCOPE		2
#define MIN_CACHE_SIZE		(64*1024U)
#define DEFAULT_CACHE_SIZE	(5*1024*1024U)
#define ITERATIONS		2
#define SIZE_THRESH		130
#define COST_THRESH		130

/*
 * The migration cost is a function of 'domain distance'. Domain
 * distance is the number of steps a CPU has to iterate down its
 * domain tree to share a domain with the other CPU. The farther
 * two CPUs are from each other, the larger the distance gets.
 *
 * Note that we use the distance only to cache measurement results,
 * the distance value is not used numerically otherwise. When two
 * CPUs have the same distance it is assumed that the migration
 * cost is the same. (this is a simplification but quite practical)
 */
#define MAX_DOMAIN_DISTANCE 32

static unsigned long long migration_cost[MAX_DOMAIN_DISTANCE] =
		{ [ 0 ... MAX_DOMAIN_DISTANCE-1 ] = -1LL };

/*
 * Allow override of migration cost - in units of microseconds.
 * E.g. migration_cost=1000,2000,3000 will set up a level-1 cost
 * of 1 msec, level-2 cost of 2 msecs and level3 cost of 3 msecs:
 */
static int __init migration_cost_setup(char *str)
{
	int ints[MAX_DOMAIN_DISTANCE+1], i;

	str = get_options(str, ARRAY_SIZE(ints), ints);

	printk("#ints: %d\n", ints[0]);
	for (i = 1; i <= ints[0]; i++) {
		migration_cost[i-1] = (unsigned long long)ints[i]*1000;
		printk("migration_cost[%d]: %Ld\n", i-1, migration_cost[i-1]);
	}
	return 1;
}

__setup ("migration_cost=", migration_cost_setup);

/*
 * Global multiplier (divisor) for migration-cutoff values,
 * in percentiles. E.g. use a value of 150 to get 1.5 times
 * longer cache-hot cutoff times.
 *
 * (We scale it from 100 to 128 to long long handling easier.)
 */

#define MIGRATION_FACTOR_SCALE 128

static unsigned int migration_factor = MIGRATION_FACTOR_SCALE;

static int __init setup_migration_factor(char *str)
{
	get_option(&str, &migration_factor);
	migration_factor = migration_factor * MIGRATION_FACTOR_SCALE / 100;
	return 1;
}

__setup("migration_factor=", setup_migration_factor);

/*
 * Estimated distance of two CPUs, measured via the number of domains
 * we have to pass for the two CPUs to be in the same span:
 */
static unsigned long domain_distance(int cpu1, int cpu2)
{
	unsigned long distance = 0;
	struct sched_domain *sd;

	for_each_domain(cpu1, sd) {
		WARN_ON(!cpu_isset(cpu1, sd->span));
		if (cpu_isset(cpu2, sd->span))
			return distance;
		distance++;
	}
	if (distance >= MAX_DOMAIN_DISTANCE) {
		WARN_ON(1);
		distance = MAX_DOMAIN_DISTANCE-1;
	}

	return distance;
}

static unsigned int migration_debug;

static int __init setup_migration_debug(char *str)
{
	get_option(&str, &migration_debug);
	return 1;
}

__setup("migration_debug=", setup_migration_debug);

/*
 * Maximum cache-size that the scheduler should try to measure.
 * Architectures with larger caches should tune this up during
 * bootup. Gets used in the domain-setup code (i.e. during SMP
 * bootup).
 */
unsigned int max_cache_size;

static int __init setup_max_cache_size(char *str)
{
	get_option(&str, &max_cache_size);
	return 1;
}

__setup("max_cache_size=", setup_max_cache_size);

/*
 * Dirty a big buffer in a hard-to-predict (for the L2 cache) way. This
 * is the operation that is timed, so we try to generate unpredictable
 * cachemisses that still end up filling the L2 cache:
 */
static void touch_cache(void *__cache, unsigned long __size)
{
	unsigned long size = __size/sizeof(long), chunk1 = size/3,
			chunk2 = 2*size/3;
	unsigned long *cache = __cache;
	int i;

	for (i = 0; i < size/6; i += 8) {
		switch (i % 6) {
			case 0: cache[i]++;
			case 1: cache[size-1-i]++;
			case 2: cache[chunk1-i]++;
			case 3: cache[chunk1+i]++;
			case 4: cache[chunk2-i]++;
			case 5: cache[chunk2+i]++;
		}
	}
}

/*
 * Measure the cache-cost of one task migration. Returns in units of nsec.
 */
static unsigned long long measure_one(void *cache, unsigned long size,
				      int source, int target)
{
	cpumask_t mask, saved_mask;
	unsigned long long t0, t1, t2, t3, cost;

	saved_mask = current->cpus_allowed;

	/*
	 * Flush source caches to RAM and invalidate them:
	 */
	sched_cacheflush();

	/*
	 * Migrate to the source CPU:
	 */
	mask = cpumask_of_cpu(source);
	set_cpus_allowed(current, mask);
	WARN_ON(smp_processor_id() != source);

	/*
	 * Dirty the working set:
	 */
	t0 = sched_clock();
	touch_cache(cache, size);
	t1 = sched_clock();

	/*
	 * Migrate to the target CPU, dirty the L2 cache and access
	 * the shared buffer. (which represents the working set
	 * of a migrated task.)
	 */
	mask = cpumask_of_cpu(target);
	set_cpus_allowed(current, mask);
	WARN_ON(smp_processor_id() != target);

	t2 = sched_clock();
	touch_cache(cache, size);
	t3 = sched_clock();

	cost = t1-t0 + t3-t2;

	if (migration_debug >= 2)
		printk("[%d->%d]: %8Ld %8Ld %8Ld => %10Ld.\n",
			source, target, t1-t0, t1-t0, t3-t2, cost);
	/*
	 * Flush target caches to RAM and invalidate them:
	 */
	sched_cacheflush();

	set_cpus_allowed(current, saved_mask);

	return cost;
}

/*
 * Measure a series of task migrations and return the average
 * result. Since this code runs early during bootup the system
 * is 'undisturbed' and the average latency makes sense.
 *
 * The algorithm in essence auto-detects the relevant cache-size,
 * so it will properly detect different cachesizes for different
 * cache-hierarchies, depending on how the CPUs are connected.
 *
 * Architectures can prime the upper limit of the search range via
 * max_cache_size, otherwise the search range defaults to 20MB...64K.
 */
static unsigned long long
measure_cost(int cpu1, int cpu2, void *cache, unsigned int size)
{
	unsigned long long cost1, cost2;
	int i;

	/*
	 * Measure the migration cost of 'size' bytes, over an
	 * average of 10 runs:
	 *
	 * (We perturb the cache size by a small (0..4k)
	 *  value to compensate size/alignment related artifacts.
	 *  We also subtract the cost of the operation done on
	 *  the same CPU.)
	 */
	cost1 = 0;

	/*
	 * dry run, to make sure we start off cache-cold on cpu1,
	 * and to get any vmalloc pagefaults in advance:
	 */
	measure_one(cache, size, cpu1, cpu2);
	for (i = 0; i < ITERATIONS; i++)
		cost1 += measure_one(cache, size - i*1024, cpu1, cpu2);

	measure_one(cache, size, cpu2, cpu1);
	for (i = 0; i < ITERATIONS; i++)
		cost1 += measure_one(cache, size - i*1024, cpu2, cpu1);

	/*
	 * (We measure the non-migrating [cached] cost on both
	 *  cpu1 and cpu2, to handle CPUs with different speeds)
	 */
	cost2 = 0;

	measure_one(cache, size, cpu1, cpu1);
	for (i = 0; i < ITERATIONS; i++)
		cost2 += measure_one(cache, size - i*1024, cpu1, cpu1);

	measure_one(cache, size, cpu2, cpu2);
	for (i = 0; i < ITERATIONS; i++)
		cost2 += measure_one(cache, size - i*1024, cpu2, cpu2);

	/*
	 * Get the per-iteration migration cost:
	 */
	do_div(cost1, 2*ITERATIONS);
	do_div(cost2, 2*ITERATIONS);

	return cost1 - cost2;
}

static unsigned long long measure_migration_cost(int cpu1, int cpu2)
{
	unsigned long long max_cost = 0, fluct = 0, avg_fluct = 0;
	unsigned int max_size, size, size_found = 0;
	long long cost = 0, prev_cost;
	void *cache;

	/*
	 * Search from max_cache_size*5 down to 64K - the real relevant
	 * cachesize has to lie somewhere inbetween.
	 */
	if (max_cache_size) {
		max_size = max(max_cache_size * SEARCH_SCOPE, MIN_CACHE_SIZE);
		size = max(max_cache_size / SEARCH_SCOPE, MIN_CACHE_SIZE);
	} else {
		/*
		 * Since we have no estimation about the relevant
		 * search range
		 */
		max_size = DEFAULT_CACHE_SIZE * SEARCH_SCOPE;
		size = MIN_CACHE_SIZE;
	}

	if (!cpu_online(cpu1) || !cpu_online(cpu2)) {
		printk("cpu %d and %d not both online!\n", cpu1, cpu2);
		return 0;
	}

	/*
	 * Allocate the working set:
	 */
	cache = vmalloc(max_size);
	if (!cache) {
		printk("could not vmalloc %d bytes for cache!\n", 2*max_size);
		return 1000000; // return 1 msec on very small boxen
	}

	while (size <= max_size) {
		prev_cost = cost;
		cost = measure_cost(cpu1, cpu2, cache, size);

		/*
		 * Update the max:
		 */
		if (cost > 0) {
			if (max_cost < cost) {
				max_cost = cost;
				size_found = size;
			}
		}
		/*
		 * Calculate average fluctuation, we use this to prevent
		 * noise from triggering an early break out of the loop:
		 */
		fluct = abs(cost - prev_cost);
		avg_fluct = (avg_fluct + fluct)/2;

		if (migration_debug)
			printk("-> [%d][%d][%7d] %3ld.%ld [%3ld.%ld] (%ld): (%8Ld %8Ld)\n",
				cpu1, cpu2, size,
				(long)cost / 1000000,
				((long)cost / 100000) % 10,
				(long)max_cost / 1000000,
				((long)max_cost / 100000) % 10,
				domain_distance(cpu1, cpu2),
				cost, avg_fluct);

		/*
		 * If we iterated at least 20% past the previous maximum,
		 * and the cost has dropped by more than 20% already,
		 * (taking fluctuations into account) then we assume to
		 * have found the maximum and break out of the loop early:
		 */
		if (size_found && (size*100 > size_found*SIZE_THRESH))
			if (cost+avg_fluct <= 0 ||
				max_cost*100 > (cost+avg_fluct)*COST_THRESH) {

				if (migration_debug)
					printk("-> found max.\n");
				break;
			}
		/*
		 * Increase the cachesize in 5% steps:
		 */
		size = size * 20 / 19;
	}

	if (migration_debug)
		printk("[%d][%d] working set size found: %d, cost: %Ld\n",
			cpu1, cpu2, size_found, max_cost);

	vfree(cache);

	/*
	 * A task is considered 'cache cold' if at least 2 times
	 * the worst-case cost of migration has passed.
	 *
	 * (this limit is only listened to if the load-balancing
	 * situation is 'nice' - if there is a large imbalance we
	 * ignore it for the sake of CPU utilization and
	 * processing fairness.)
	 */
	return 2 * max_cost * migration_factor / MIGRATION_FACTOR_SCALE;
}

static void calibrate_migration_costs(const cpumask_t *cpu_map)
{
	int cpu1 = -1, cpu2 = -1, cpu, orig_cpu = raw_smp_processor_id();
	unsigned long j0, j1, distance, max_distance = 0;
	struct sched_domain *sd;

	j0 = jiffies;

	/*
	 * First pass - calculate the cacheflush times:
	 */
	for_each_cpu_mask(cpu1, *cpu_map) {
		for_each_cpu_mask(cpu2, *cpu_map) {
			if (cpu1 == cpu2)
				continue;
			distance = domain_distance(cpu1, cpu2);
			max_distance = max(max_distance, distance);
			/*
			 * No result cached yet?
			 */
			if (migration_cost[distance] == -1LL)
				migration_cost[distance] =
					measure_migration_cost(cpu1, cpu2);
		}
	}
	/*
	 * Second pass - update the sched domain hierarchy with
	 * the new cache-hot-time estimations:
	 */
	for_each_cpu_mask(cpu, *cpu_map) {
		distance = 0;
		for_each_domain(cpu, sd) {
			sd->cache_hot_time = migration_cost[distance];
			distance++;
		}
	}
	/*
	 * Print the matrix:
	 */
	if (migration_debug)
		printk("migration: max_cache_size: %d, cpu: %d MHz:\n",
			max_cache_size,
#ifdef CONFIG_X86
			cpu_khz/1000
#else
			-1
#endif
		);
	printk("migration_cost=");
	for (distance = 0; distance <= max_distance; distance++) {
		if (distance)
			printk(",");
		printk("%ld", (long)migration_cost[distance] / 1000);
	}
	printk("\n");
	j1 = jiffies;
	if (migration_debug)
		printk("migration: %ld seconds\n", (j1-j0)/HZ);

	/*
	 * Move back to the original CPU. NUMA-Q gets confused
	 * if we migrate to another quad during bootup.
	 */
	if (raw_smp_processor_id() != orig_cpu) {
		cpumask_t mask = cpumask_of_cpu(orig_cpu),
			saved_mask = current->cpus_allowed;

		set_cpus_allowed(current, mask);
		set_cpus_allowed(current, saved_mask);
	}
}

#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)
{
	int i;
	cpumask_t span, nodemask;
	DECLARE_BITMAP(used_nodes, MAX_NUMNODES);

	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

/*
 * At the moment, CONFIG_SCHED_SMT is never defined, but leave it in so we
 * can switch it on easily if needed.
 */
#ifdef CONFIG_SCHED_SMT
static DEFINE_PER_CPU(struct sched_domain, cpu_domains);
static struct sched_group sched_group_cpus[NR_CPUS];
static int cpu_to_cpu_group(int cpu)
{
	return cpu;
}
#endif

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

#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 struct sched_group *sched_group_allnodes_bycpu[NR_CPUS];

static int cpu_to_allnodes_group(int cpu)
{
	return cpu_to_node(cpu);
}
#endif

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

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

	/*
	 * Set up domains for cpus specified by the cpu_map.
	 */
	for_each_cpu_mask(i, *cpu_map) {
		int group;
		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)) {
			if (!sched_group_allnodes) {
				sched_group_allnodes
					= kmalloc(sizeof(struct sched_group)
							* MAX_NUMNODES,
						  GFP_KERNEL);
				if (!sched_group_allnodes) {
					printk(KERN_WARNING
					"Can not alloc allnodes sched group\n");
					break;
				}
				sched_group_allnodes_bycpu[i]
						= sched_group_allnodes;
			}
			sd = &per_cpu(allnodes_domains, i);
			*sd = SD_ALLNODES_INIT;
			sd->span = *cpu_map;
			group = cpu_to_allnodes_group(i);
			sd->groups = &sched_group_allnodes[group];
			p = sd;
		} 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;
		cpus_and(sd->span, sd->span, *cpu_map);
#endif

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

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

#ifdef CONFIG_SCHED_SMT
	/* Set up CPU (sibling) groups */
	for_each_cpu_mask(i, *cpu_map) {
		cpumask_t this_sibling_map = 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(sched_group_cpus, this_sibling_map,
						&cpu_to_cpu_group);
	}
#endif

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

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

		init_sched_build_groups(sched_group_phys, nodemask,
						&cpu_to_phys_group);
	}

#ifdef CONFIG_NUMA
	/* Set up node groups */
	if (sched_group_allnodes)
		init_sched_build_groups(sched_group_allnodes, *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(sizeof(struct sched_group), GFP_KERNEL);
		sched_group_nodes[i] = sg;
		for_each_cpu_mask(j, nodemask) {
			struct sched_domain *sd;
			sd = &per_cpu(node_domains, j);
			sd->groups = sg;
			if (sd->groups == NULL) {
				/* Turn off balancing if we have no groups */
				sd->flags = 0;
			}
		}
		if (!sg) {
			printk(KERN_WARNING
			"Can not alloc domain group for node %d\n", i);
			continue;
		}
		sg->cpu_power = 0;
		sg->cpumask = nodemask;
		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(sizeof(struct sched_group), GFP_KERNEL);
			if (!sg) {
				printk(KERN_WARNING
				"Can not alloc domain group for node %d\n", j);
				break;
			}
			sg->cpu_power = 0;
			sg->cpumask = tmp;
			cpus_or(covered, covered, tmp);
			prev->next = sg;
			prev = sg;
		}
		prev->next = sched_group_nodes[i];
	}
#endif

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

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

#ifdef CONFIG_NUMA
		sd = &per_cpu(allnodes_domains, i);
		if (sd->groups) {
			power = SCHED_LOAD_SCALE + SCHED_LOAD_SCALE *
				(cpus_weight(sd->groups->cpumask)-1) / 10;
			sd->groups->cpu_power = power;
		}
#endif
	}

#ifdef CONFIG_NUMA
	for (i = 0; i < MAX_NUMNODES; i++) {
		struct sched_group *sg = sched_group_nodes[i];
		int j;

		if (sg == NULL)
			continue;
next_sg:
		for_each_cpu_mask(j, sg->cpumask) {
			struct sched_domain *sd;
			int power;

			sd = &per_cpu(phys_domains, j);
			if (j != first_cpu(sd->groups->cpumask)) {
				/*
				 * Only add "power" once for each
				 * physical package.
				 */
				continue;
			}
			power = SCHED_LOAD_SCALE + SCHED_LOAD_SCALE *
				(cpus_weight(sd->groups->cpumask)-1) / 10;

			sg->cpu_power += power;
		}
		sg = sg->next;
		if (sg != sched_group_nodes[i])
			goto next_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);
#else
		sd = &per_cpu(phys_domains, i);
#endif
		cpu_attach_domain(sd, i);
	}
	/*
	 * Tune cache-hot values:
	 */
	calibrate_migration_costs(cpu_map);
}
/*
 * Set up scheduler domains and groups.  Callers must hold the hotplug lock.
 */
static void arch_init_sched_domains(const cpumask_t *cpu_map)
{
	cpumask_t cpu_default_map;

	/*
	 * Setup mask for cpus without special case scheduling requirements.
	 * For now this just excludes isolated cpus, but could be used to
	 * exclude other special cases in the future.
	 */
	cpus_andnot(cpu_default_map, *cpu_map, cpu_isolated_map);

	build_sched_domains(&cpu_default_map);
}

static void arch_destroy_sched_domains(const cpumask_t *cpu_map)
{
#ifdef CONFIG_NUMA
	int i;
	int cpu;

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

		if (sched_group_allnodes) {
			kfree(sched_group_allnodes);
			sched_group_allnodes_bycpu[cpu] = NULL;
		}

		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;
	}
#endif
}

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

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

/*
 * Partition sched domains as specified by the cpumasks below.
 * This attaches all cpus from the cpumasks to the NULL domain,
 * waits for a RCU quiescent period, recalculates sched
 * domain information and then attaches them back to the
 * correct sched domains
 * Call with hotplug lock held
 */
void partition_sched_domains(cpumask_t *partition1, cpumask_t *partition2)
{
	cpumask_t change_map;

	cpus_and(*partition1, *partition1, cpu_online_map);
	cpus_and(*partition2, *partition2, cpu_online_map);
	cpus_or(change_map, *partition1, *partition2);

	/* Detach sched domains from all of the affected cpus */
	detach_destroy_domains(&change_map);
	if (!cpus_empty(*partition1))
		build_sched_domains(partition1);
	if (!cpus_empty(*partition2))
		build_sched_domains(partition2);
}

#ifdef CONFIG_HOTPLUG_CPU
/*
 * Force a reinitialization of the sched domains hierarchy.  The domains
 * and groups cannot be updated in place without racing with the balancing
 * code, so we temporarily attach all running cpus to 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_DOWN_PREPARE:
		detach_destroy_domains(&cpu_online_map);
		return NOTIFY_OK;

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

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

	return NOTIFY_OK;
}
#endif

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

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

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

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

		rq = cpu_rq(i);
		spin_lock_init(&rq->lock);
		rq->nr_running = 0;
		rq->active = rq->arrays;
		rq->expired = rq->arrays + 1;
		rq->best_expired_prio = MAX_PRIO;

#ifdef CONFIG_SMP
		rq->sd = NULL;
		for (j = 1; j < 3; j++)
			rq->cpu_load[j] = 0;
		rq->active_balance = 0;
		rq->push_cpu = 0;
		rq->migration_thread = NULL;
		INIT_LIST_HEAD(&rq->migration_queue);
#endif
		atomic_set(&rq->nr_iowait, 0);

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

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

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

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

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

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

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

		rq = task_rq_lock(p, &flags);

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

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

#endif /* CONFIG_MAGIC_SYSRQ */

#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!
 */
task_t *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, task_t *p)
{
	cpu_curr(cpu) = p;
}

#endif