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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/debug_locks.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 <linux/kprobes.h>
#include <linux/delayacct.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) + 20, 40, MAX_BONUS) - 20 * MAX_BONUS / 40 + \
            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 static_prio_timeslice(int static_prio)
{
      if (static_prio < NICE_TO_PRIO(0))
            return SCALE_PRIO(DEF_TIMESLICE * 4, static_prio);
      else
            return SCALE_PRIO(DEF_TIMESLICE, static_prio);
}

static inline unsigned int task_timeslice(struct task_struct *p)
{
      return static_prio_timeslice(p->static_prio);
}

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

struct prio_array {
      unsigned int nr_active;
      DECLARE_BITMAP(bitmap, MAX_PRIO+1); /* include 1 bit for delimiter */
      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 rq {
      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;
      unsigned long raw_weighted_load;
#ifdef CONFIG_SMP
      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;
      struct task_struct *curr, *idle;
      struct mm_struct *prev_mm;
      struct prio_array *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;

      struct task_struct *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
      struct lock_class_key rq_lock_key;
};

static DEFINE_PER_CPU(struct rq, 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, __sd) \
      for (__sd = rcu_dereference(cpu_rq(cpu)->sd); __sd; __sd = __sd->parent)

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

#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(struct rq *rq, struct task_struct *p)
{
      return rq->curr == p;
}

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

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

      spin_unlock_irq(&rq->lock);
}

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

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

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

/*
 * __task_rq_lock - lock the runqueue a given task resides on.
 * Must be called interrupts disabled.
 */
static inline struct rq *__task_rq_lock(struct task_struct *p)
      __acquires(rq->lock)
{
      struct rq *rq;

repeat_lock_task:
      rq = task_rq(p);
      spin_lock(&rq->lock);
      if (unlikely(rq != task_rq(p))) {
            spin_unlock(&rq->lock);
            goto repeat_lock_task;
      }
      return rq;
}

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

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

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

#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) {
            struct rq *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,
};

/*
 * Expects runqueue lock to be held for atomicity of update
 */
static inline void
rq_sched_info_arrive(struct rq *rq, unsigned long delta_jiffies)
{
      if (rq) {
            rq->rq_sched_info.run_delay += delta_jiffies;
            rq->rq_sched_info.pcnt++;
      }
}

/*
 * Expects runqueue lock to be held for atomicity of update
 */
static inline void
rq_sched_info_depart(struct rq *rq, unsigned long delta_jiffies)
{
      if (rq)
            rq->rq_sched_info.cpu_time += delta_jiffies;
}
# 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 */
static inline void
rq_sched_info_arrive(struct rq *rq, unsigned long delta_jiffies)
{}
static inline void
rq_sched_info_depart(struct rq *rq, unsigned long delta_jiffies)
{}
# 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 struct rq *this_rq_lock(void)
      __acquires(rq->lock)
{
      struct rq *rq;

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

      return rq;
}

#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
/*
 * 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(struct task_struct *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 void sched_info_arrive(struct task_struct *t)
{
      unsigned long now = jiffies, delta_jiffies = 0;

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

      rq_sched_info_arrive(task_rq(t), delta_jiffies);
}

/*
 * 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(struct task_struct *t)
{
      if (unlikely(sched_info_on()))
            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(struct task_struct *t)
{
      unsigned long delta_jiffies = jiffies - t->sched_info.last_arrival;

      t->sched_info.cpu_time += delta_jiffies;
      rq_sched_info_depart(task_rq(t), delta_jiffies);
}

/*
 * 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(struct task_struct *prev, struct task_struct *next)
{
      struct rq *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);
}
static inline void
sched_info_switch(struct task_struct *prev, struct task_struct *next)
{
      if (unlikely(sched_info_on()))
            __sched_info_switch(prev, next);
}
#else
#define sched_info_queued(t)        do { } while (0)
#define sched_info_switch(t, next)  do { } while (0)
#endif /* CONFIG_SCHEDSTATS || CONFIG_TASK_DELAY_ACCT */

/*
 * Adding/removing a task to/from a priority array:
 */
static void dequeue_task(struct task_struct *p, struct prio_array *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, struct prio_array *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, struct prio_array *array)
{
      list_move_tail(&p->run_list, array->queue + p->prio);
}

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

/*
 * __normal_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 inline int __normal_prio(struct task_struct *p)
{
      int bonus, 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;
}

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

/*
 * Assume: static_prio_timeslice(NICE_TO_PRIO(0)) == DEF_TIMESLICE
 * If static_prio_timeslice() is ever changed to break this assumption then
 * this code will need modification
 */
#define TIME_SLICE_NICE_ZERO DEF_TIMESLICE
#define LOAD_WEIGHT(lp) \
      (((lp) * SCHED_LOAD_SCALE) / TIME_SLICE_NICE_ZERO)
#define PRIO_TO_LOAD_WEIGHT(prio) \
      LOAD_WEIGHT(static_prio_timeslice(prio))
#define RTPRIO_TO_LOAD_WEIGHT(rp) \
      (PRIO_TO_LOAD_WEIGHT(MAX_RT_PRIO) + LOAD_WEIGHT(rp))

static void set_load_weight(struct task_struct *p)
{
      if (has_rt_policy(p)) {
#ifdef CONFIG_SMP
            if (p == task_rq(p)->migration_thread)
                  /*
                   * The migration thread does the actual balancing.
                   * Giving its load any weight will skew balancing
                   * adversely.
                   */
                  p->load_weight = 0;
            else
#endif
                  p->load_weight = RTPRIO_TO_LOAD_WEIGHT(p->rt_priority);
      } else
            p->load_weight = PRIO_TO_LOAD_WEIGHT(p->static_prio);
}

static inline void
inc_raw_weighted_load(struct rq *rq, const struct task_struct *p)
{
      rq->raw_weighted_load += p->load_weight;
}

static inline void
dec_raw_weighted_load(struct rq *rq, const struct task_struct *p)
{
      rq->raw_weighted_load -= p->load_weight;
}

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

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

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

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

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

/*
 * __activate_task - move a task to the runqueue.
 */
static void __activate_task(struct task_struct *p, struct rq *rq)
{
      struct prio_array *target = rq->active;

      if (batch_task(p))
            target = rq->expired;
      enqueue_task(p, target);
      inc_nr_running(p, rq);
}

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

/*
 * Recalculate p->normal_prio and p->prio after having slept,
 * updating the sleep-average too:
 */
static int recalc_task_prio(struct task_struct *p, unsigned long long now)
{
      /* Caller must always ensure 'now >= p->timestamp' */
      unsigned long sleep_time = now - p->timestamp;

      if (batch_task(p))
            sleep_time = 0;

      if (likely(sleep_time > 0)) {
            /*
             * This ceiling is set to the lowest priority that would allow
             * a task to be reinserted into the active array on timeslice
             * completion.
             */
            unsigned long ceiling = INTERACTIVE_SLEEP(p);

            if (p->mm && sleep_time > ceiling && p->sleep_avg < ceiling) {
                  /*
                   * Prevents user tasks from achieving best priority
                   * with one single large enough sleep.
                   */
                  p->sleep_avg = ceiling;
                  /*
                   * Using INTERACTIVE_SLEEP() as a ceiling places a
                   * nice(0) task 1ms sleep away from promotion, and
                   * gives it 700ms to round-robin with no chance of
                   * being demoted.  This is more than generous, so
                   * mark this sleep as non-interactive to prevent the
                   * on-runqueue bonus logic from intervening should
                   * this task not receive cpu immediately.
                   */
                  p->sleep_type = SLEEP_NONINTERACTIVE;
            } else {
                  /*
                   * Tasks waking from uninterruptible sleep are
                   * limited in their sleep_avg rise as they
                   * are likely to be waiting on I/O
                   */
                  if (p->sleep_type == SLEEP_NONINTERACTIVE && p->mm) {
                        if (p->sleep_avg >= ceiling)
                              sleep_time = 0;
                        else if (p->sleep_avg + sleep_time >=
                               ceiling) {
                                    p->sleep_avg = ceiling;
                                    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(struct task_struct *p, struct rq *rq, int local)
{
      unsigned long long now;

      now = sched_clock();
#ifdef CONFIG_SMP
      if (!local) {
            /* Compensate for drifting sched_clock */
            struct rq *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->sleep_type == SLEEP_NORMAL) {
            /*
             * 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->sleep_type = SLEEP_INTERRUPTED;
            else {
                  /*
                   * Normal first-time wakeups get a credit too for
                   * on-runqueue time, but it will be weighted down:
                   */
                  p->sleep_type = SLEEP_INTERACTIVE;
            }
      }
      p->timestamp = now;

      __activate_task(p, rq);
}

/*
 * deactivate_task - remove a task from the runqueue.
 */
static void deactivate_task(struct task_struct *p, struct rq *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

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

static void resched_task(struct task_struct *p)
{
      int 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 */
      smp_mb();
      if (!tsk_is_polling(p))
            smp_send_reschedule(cpu);
}
#else
static inline void resched_task(struct task_struct *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 struct task_struct *p)
{
      return cpu_curr(task_cpu(p)) == p;
}

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

#ifdef CONFIG_SMP
struct migration_req {
      struct list_head list;

      struct task_struct *task;
      int dest_cpu;

      struct completion done;
};

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

      /*
       * If the task is not on a runqueue (and not running), then
       * it is sufficient to simply update the task's cpu field.
       */
      if (!p->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(struct task_struct *p)
{
      unsigned long flags;
      struct rq *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(struct task_struct *p)
{
      int cpu;

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

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

      if (type == 0)
            return rq->raw_weighted_load;

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

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

      if (type == 0)
            return rq->raw_weighted_load;

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

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

      return n ? rq->raw_weighted_load / n : SCHED_LOAD_SCALE;
}

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

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

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

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

      return idlest;
}

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

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

      while (sd) {
            cpumask_t span;
            struct sched_group *group;
            int new_cpu;
            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, struct task_struct *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, struct task_struct *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(struct task_struct *p, unsigned int state, int sync)
{
      int cpu, this_cpu, success = 0;
      unsigned long flags;
      long old_state;
      struct rq *rq;
#ifdef CONFIG_SMP
      struct sched_domain *sd, *this_sd = NULL;
      unsigned long load, this_load;
      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;
                  unsigned long tl_per_task = cpu_avg_load_per_task(this_cpu);

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

                  if ((tl <= load &&
                        tl + target_load(cpu, idx) <= tl_per_task) ||
                        100*(tl + p->load_weight) <= 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->sleep_type = SLEEP_NONINTERACTIVE;
      } else

      /*
       * Tasks that have marked their sleep as noninteractive get
       * woken up with their sleep average not weighted in an
       * interactive way.
       */
            if (old_state & TASK_NONINTERACTIVE)
                  p->sleep_type = SLEEP_NONINTERACTIVE;


      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(struct task_struct *p)
{
      return try_to_wake_up(p, TASK_STOPPED | TASK_TRACED |
                         TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE, 0);
}
EXPORT_SYMBOL(wake_up_process);

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

/*
 * Perform scheduler related setup for a newly forked process p.
 * p is forked by current.
 */
void fastcall sched_fork(struct task_struct *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;

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

      INIT_LIST_HEAD(&p->run_list);
      p->array = NULL;
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
      if (unlikely(sched_info_on()))
            memset(&p->sched_info, 0, sizeof(p->sched_info));
#endif
#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
      p->oncpu = 0;
#endif
#ifdef CONFIG_PREEMPT
      /* Want to start with kernel preemption disabled. */
      task_thread_info(p)->preempt_count = 1;
#endif
      /*
       * 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(struct task_struct *p, unsigned long clone_flags)
{
      struct rq *rq, *this_rq;
      unsigned long flags;
      int this_cpu, cpu;

      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;
                        p->normal_prio = current->normal_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(struct task_struct *p)
{
      unsigned long flags;
      struct rq *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(struct rq *rq, struct task_struct *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(struct rq *rq, struct task_struct *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)) {
            /*
             * Remove function-return probe instances associated with this
             * task and put them back on the free list.
             */
            kprobe_flush_task(prev);
            put_task_struct(prev);
      }
}

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

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

/*
 * context_switch - switch to the new MM and the new
 * thread's register state.
 */
static inline struct task_struct *
context_switch(struct rq *rq, struct task_struct *prev,
             struct task_struct *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;
      }
      /*
       * Since the runqueue lock will be released by the next
       * task (which is an invalid locking op but in the case
       * of the scheduler it's an obvious special-case), so we
       * do an early lockdep release here:
       */
#ifndef __ARCH_WANT_UNLOCKED_CTXSW
      spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
#endif

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

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

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

      return sum;
}

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

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

      return sum;
}

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

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

      return sum;
}

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

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

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

      return running + uninterruptible;
}

#ifdef CONFIG_SMP

/*
 * Is this task likely cache-hot:
 */
static inline int
task_hot(struct task_struct *p, unsigned long long now, struct sched_domain *sd)
{
      return (long long)(now - p->last_ran) < (long long)sd->cache_hot_time;
}

/*
 * double_rq_lock - safely lock two runqueues
 *
 * Note this does not disable interrupts like task_rq_lock,
 * you need to do so manually before calling.
 */
static void double_rq_lock(struct rq *rq1, struct rq *rq2)
      __acquires(rq1->lock)
      __acquires(rq2->lock)
{
      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(struct rq *rq1, struct rq *rq2)
      __releases(rq1->lock)
      __releases(rq2->lock)
{
      spin_unlock(&rq1->lock);
      if (rq1 != rq2)
            spin_unlock(&rq2->lock);
      else
            __release(rq2->lock);
}

/*
 * double_lock_balance - lock the busiest runqueue, this_rq is locked already.
 */
static void double_lock_balance(struct rq *this_rq, struct rq *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(struct task_struct *p, int dest_cpu)
{
      struct migration_req req;
      unsigned long flags;
      struct rq *rq;

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

      /* force the process onto the specified CPU */
      if (migrate_task(p, dest_cpu, &req)) {
            /* Need to wait for migration thread (might exit: take ref). */
            struct task_struct *mt = rq->migration_thread;

            get_task_struct(mt);
            task_rq_unlock(rq, &flags);
            wake_up_process(mt);
            put_task_struct(mt);
            wait_for_completion(&req.done);

            return;
      }
out:
      task_rq_unlock(rq, &flags);
}

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

/*
 * pull_task - move a task from a remote runqueue to the local runqueue.
 * Both runqueues must be locked.
 */
static void pull_task(struct rq *src_rq, struct prio_array *src_array,
                  struct task_struct *p, struct rq *this_rq,
                  struct prio_array *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
int can_migrate_task(struct task_struct *p, struct rq *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;
}

#define rq_best_prio(rq) min((rq)->curr->prio, (rq)->best_expired_prio)

/*
 * move_tasks tries to move up to max_nr_move tasks and max_load_move weighted
 * load 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(struct rq *this_rq, int this_cpu, struct rq *busiest,
                  unsigned long max_nr_move, unsigned long max_load_move,
                  struct sched_domain *sd, enum idle_type idle,
                  int *all_pinned)
{
      int idx, pulled = 0, pinned = 0, this_best_prio, best_prio,
          best_prio_seen, skip_for_load;
      struct prio_array *array, *dst_array;
      struct list_head *head, *curr;
      struct task_struct *tmp;
      long rem_load_move;

      if (max_nr_move == 0 || max_load_move == 0)
            goto out;

      rem_load_move = max_load_move;
      pinned = 1;
      this_best_prio = rq_best_prio(this_rq);
      best_prio = rq_best_prio(busiest);
      /*
       * Enable handling of the case where there is more than one task
       * with the best priority.   If the current running task is one
       * of those with prio==best_prio we know it won't be moved
       * and therefore it's safe to override the skip (based on load) of
       * any task we find with that prio.
       */
      best_prio_seen = best_prio == busiest->curr->prio;

      /*
       * 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, struct task_struct, run_list);

      curr = curr->prev;

      /*
       * To help distribute high priority tasks accross CPUs we don't
       * skip a task if it will be the highest priority task (i.e. smallest
       * prio value) on its new queue regardless of its load weight
       */
      skip_for_load = tmp->load_weight > rem_load_move;
      if (skip_for_load && idx < this_best_prio)
            skip_for_load = !best_prio_seen && idx == best_prio;
      if (skip_for_load ||
          !can_migrate_task(tmp, busiest, this_cpu, sd, idle, &pinned)) {

            best_prio_seen |= idx == best_prio;
            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++;
      rem_load_move -= tmp->load_weight;

      /*
       * We only want to steal up to the prescribed number of tasks
       * and the prescribed amount of weighted load.
       */
      if (pulled < max_nr_move && rem_load_move > 0) {
            if (idx < this_best_prio)
                  this_best_prio = idx;
            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 amount of weighted load which
 * should be moved to restore balance via the imbalance parameter.
 */
static struct sched_group *
find_busiest_group(struct sched_domain *sd, int this_cpu,
               unsigned long *imbalance, enum 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;
      unsigned long busiest_load_per_task, busiest_nr_running;
      unsigned long this_load_per_task, this_nr_running;
      int load_idx;
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
      int power_savings_balance = 1;
      unsigned long leader_nr_running = 0, min_load_per_task = 0;
      unsigned long min_nr_running = ULONG_MAX;
      struct sched_group *group_min = NULL, *group_leader = NULL;
#endif

      max_load = this_load = total_load = total_pwr = 0;
      busiest_load_per_task = busiest_nr_running = 0;
      this_load_per_task = this_nr_running = 0;
      if (idle == 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, group_capacity;
            int local_group;
            int i;
            unsigned long sum_nr_running, sum_weighted_load;

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

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

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

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

                  avg_load += load;
                  sum_nr_running += rq->nr_running;
                  sum_weighted_load += rq->raw_weighted_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;

            group_capacity = group->cpu_power / SCHED_LOAD_SCALE;

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

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

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

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

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

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

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

      avg_load = (SCHED_LOAD_SCALE * total_load) / total_pwr;

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

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

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

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

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

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

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

            if (max_load - this_load >= busiest_load_per_task * imbn) {
                  *imbalance = busiest_load_per_task;
                  return busiest;
            }

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

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

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

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

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

            *imbalance = busiest_load_per_task;
      }

      return busiest;

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

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

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

      for_each_cpu_mask(i, group->cpumask) {
            rq = cpu_rq(i);

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

            if (rq->raw_weighted_load > max_load) {
                  max_load = rq->raw_weighted_load;
                  busiest = rq;
            }
      }

      return busiest;
}

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

static inline unsigned long minus_1_or_zero(unsigned long n)
{
      return n > 0 ? n - 1 : 0;
}

/*
 * 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, struct rq *this_rq,
                  struct sched_domain *sd, enum idle_type idle)
{
      int nr_moved, all_pinned = 0, active_balance = 0, sd_idle = 0;
      struct sched_group *group;
      unsigned long imbalance;
      struct rq *busiest;

      if (idle != NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER &&
          !sched_smt_power_savings)
            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, imbalance);
      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,
                              minus_1_or_zero(busiest->nr_running),
                              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 &&
          !sched_smt_power_savings)
            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 &&
                  !sched_smt_power_savings)
            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, struct rq *this_rq, struct sched_domain *sd)
{
      struct sched_group *group;
      struct rq *busiest = NULL;
      unsigned long imbalance;
      int nr_moved = 0;
      int sd_idle = 0;

      if (sd->flags & SD_SHARE_CPUPOWER && !sched_smt_power_savings)
            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, imbalance);
      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,
                              minus_1_or_zero(busiest->nr_running),
                              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 &&
                              !sched_smt_power_savings)
            return -1;
      sd->nr_balance_failed = 0;

      return 0;
}

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

      for_each_domain(this_cpu, sd) {
            if (sd->flags & SD_BALANCE_NEWIDLE) {
                  /* If we've pulled tasks over stop searching: */
                  if (load_balance_newidle(this_cpu, this_rq, sd))
                        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(struct rq *busiest_rq, int busiest_cpu)
{
      int target_cpu = busiest_rq->push_cpu;
      struct sched_domain *sd;
      struct rq *target_rq;

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

      target_rq = cpu_rq(target_cpu);

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

      /* move a task from busiest_rq to target_rq */
      double_lock_balance(busiest_rq, target_rq);

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

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

            if (move_tasks(target_rq, target_cpu, busiest_rq, 1,
                         RTPRIO_TO_LOAD_WEIGHT(100), sd, SCHED_IDLE,
                         NULL))
                  schedstat_inc(sd, alb_pushed);
            else
                  schedstat_inc(sd, alb_failed);
      }
      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: */
static inline unsigned long cpu_offset(int cpu)
{
      return jiffies + cpu * HZ / NR_CPUS;
}

static void
rebalance_tick(int this_cpu, struct rq *this_rq, enum idle_type idle)
{
      unsigned long this_load, interval, j = cpu_offset(this_cpu);
      struct sched_domain *sd;
      int i, scale;

      this_load = this_rq->raw_weighted_load;

      /* Update our load: */
      for (i = 0, scale = 1; i < 3; i++, scale <<= 1) {
            unsigned long old_load, new_load;

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

      for_each_domain(this_cpu, sd) {
            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, struct rq *rq, enum idle_type idle)
{
}
static inline void idle_balance(int cpu, struct rq *rq)
{
}
#endif

static inline int wake_priority_sleeper(struct rq *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(struct task_struct *p, struct rq *rq, unsigned long long now)
{
      p->sched_time += now - max(p->timestamp, rq->timestamp_last_tick);
}

/*
 * 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 struct task_struct *p)
{
      unsigned long long ns;
      unsigned long flags;

      local_irq_save(flags);
      ns = max(p->timestamp, task_rq(p)->timestamp_last_tick);
      ns = p->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:
 */
static inline int expired_starving(struct rq *rq)
{
      if (rq->curr->static_prio > rq->best_expired_prio)
            return 1;
      if (!STARVATION_LIMIT || !rq->expired_timestamp)
            return 0;
      if (jiffies - rq->expired_timestamp > STARVATION_LIMIT * rq->nr_running)
            return 1;
      return 0;
}

/*
 * 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;
      struct rq *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);
      struct rq *rq = this_rq();

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

/*
 * This function gets called by the timer code, with HZ frequency.
 * We call it with interrupts disabled.
 *
 * It also gets called by the fork code, when changing the parent's
 * timeslices.
 */
void scheduler_tick(void)
{
      unsigned long long now = sched_clock();
      struct task_struct *p = current;
      int cpu = smp_processor_id();
      struct rq *rq = cpu_rq(cpu);

      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(struct rq *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);
}

/*
 * Called with interrupt disabled and this_rq's runqueue locked.
 */
static void wake_sleeping_dependent(int this_cpu)
{
      struct sched_domain *tmp, *sd = NULL;
      int i;

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

      if (!sd)
            return;

      for_each_cpu_mask(i, sd->span) {
            struct rq *smt_rq = cpu_rq(i);

            if (i == this_cpu)
                  continue;
            if (unlikely(!spin_trylock(&smt_rq->lock)))
                  continue;

            wakeup_busy_runqueue(smt_rq);
            spin_unlock(&smt_rq->lock);
      }
}

/*
 * 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(struct task_struct *p, struct sched_domain *sd)
{
      return p->time_slice * (100 - sd->per_cpu_gain) / 100;
}

/*
 * To minimise lock contention and not have to drop this_rq's runlock we only
 * trylock the sibling runqueues and bypass those runqueues if we fail to
 * acquire their lock. As we only trylock the normal locking order does not
 * need to be obeyed.
 */
static int
dependent_sleeper(int this_cpu, struct rq *this_rq, struct task_struct *p)
{
      struct sched_domain *tmp, *sd = NULL;
      int ret = 0, i;

      /* kernel/rt threads do not participate in dependent sleeping */
      if (!p->mm || rt_task(p))
            return 0;

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

      if (!sd)
            return 0;

      for_each_cpu_mask(i, sd->span) {
            struct task_struct *smt_curr;
            struct rq *smt_rq;

            if (i == this_cpu)
                  continue;

            smt_rq = cpu_rq(i);
            if (unlikely(!spin_trylock(&smt_rq->lock)))
                  continue;

            smt_curr = smt_rq->curr;

            if (!smt_curr->mm)
                  goto unlock;

            /*
             * 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;
            }
unlock:
            spin_unlock(&smt_rq->lock);
      }
      return ret;
}
#else
static inline void wake_sleeping_dependent(int this_cpu)
{
}
static inline int
dependent_sleeper(int this_cpu, struct rq *this_rq, struct task_struct *p)
{
      return 0;
}
#endif

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

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

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

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

#endif

static inline int interactive_sleep(enum sleep_type sleep_type)
{
      return (sleep_type == SLEEP_INTERACTIVE ||
            sleep_type == SLEEP_INTERRUPTED);
}

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

      /*
       * Test if we are atomic.  Since do_exit() needs to call into
       * schedule() atomically, we ignore that path for now.
       * Otherwise, whine if we are scheduling when we should not be.
       */
      if (unlikely(in_atomic() && !current->exit_state)) {
            printk(KERN_ERR "BUG: 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)) {
            idle_balance(cpu, rq);
            if (!rq->nr_running) {
                  next = rq->idle;
                  rq->expired_timestamp = 0;
                  wake_sleeping_dependent(cpu);
                  goto switch_tasks;
            }
      }

      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, struct task_struct, run_list);

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

            if (next->sleep_type == SLEEP_INTERACTIVE)
                  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);
            }
      }
      next->sleep_type = SLEEP_NORMAL;
      if (dependent_sleeper(cpu, rq, next))
            next = rq->idle;
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 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 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)
{
      return try_to_wake_up(curr->private, mode, sync);
}
EXPORT_SYMBOL(default_wake_function);

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

      list_for_each_safe(tmp, next, &q->task_list) {
            wait_queue_t *curr = list_entry(tmp, wait_queue_t, task_list);
            unsigned flags = curr->flags;

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

/**
 * __wake_up - wake up threads blocked on a waitqueue.
 * @q: the waitqueue
 * @mode: which threads
 * @nr_exclusive: how many wake-one or wake-many threads to wake up
 * @key: is directly passed to the wakeup function
 */
void fastcall __wake_up(wait_queue_head_t *q, unsigned int mode,
                  int nr_exclusive, void *key)
{
      unsigned long flags;

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

/*
 * Same as __wake_up but called with the spinlock in wait_queue_head_t held.
 */
void fastcall __wake_up_locked(wait_queue_head_t *q, unsigned int mode)
{
      __wake_up_common(q, mode, 1, 0, NULL);
}

/**
 * __wake_up_sync - wake up threads blocked on a waitqueue.
 * @q: the waitqueue
 * @mode: which threads
 * @nr_exclusive: how many wake-one or wake-many threads to wake up
 *
 * The sync wakeup differs that the waker knows that it will schedule
 * away soon, so while the target thread will be woken up, it will not
 * be migrated to another CPU - ie. the two threads are 'synchronized'
 * with each other. This can prevent needless bouncing between CPUs.
 *
 * On UP it can prevent extra preemption.
 */
void fastcall
__wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
{
      unsigned long flags;
      int sync = 1;

      if (unlikely(!q))
            return;

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

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

void 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);

#ifdef CONFIG_RT_MUTEXES

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

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

      rq = task_rq_lock(p, &flags);

      oldprio = p->prio;
      array = p->array;
      if (array)
            dequeue_task(p, array);
      p->prio = prio;

      if (array) {
            /*
             * If changing to an RT priority then queue it
             * in the active array!
             */
            if (rt_task(p))
                  array = rq->active;
            enqueue_task(p, array);
            /*
             * 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);
}

#endif

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

      if (TASK_NICE(p) == nice || nice < -20 || nice > 19)
            return;
      /*
       * We have to be careful, if called from sys_setpriority(),
       * the task might be in the middle of scheduling on another CPU.
       */
      rq = task_rq_lock(p, &flags);
      /*
       * The RT priorities are set via sched_setscheduler(), but we still
       * allow the 'normal' nice value to be set - but as expected
       * it wont have any effect on scheduling until the task is
       * not SCHED_NORMAL/SCHED_BATCH:
       */
      if (has_rt_policy(p)) {
            p->static_prio = NICE_TO_PRIO(nice);
            goto out_unlock;
      }
      array = p->array;
      if (array) {
            dequeue_task(p, array);
            dec_raw_weighted_load(rq, p);
      }

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

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

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

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

#ifdef __ARCH_WANT_SYS_NICE

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

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

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

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

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

      set_user_nice(current, nice);
      return 0;
}

#endif

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

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

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

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

/**
 * find_process_by_pid - find a process with a matching PID value.
 * @pid: the pid in question.
 */
static inline struct task_struct *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;
      p->normal_prio = normal_prio(p);
      /* we are holding p->pi_lock already */
      p->prio = rt_mutex_getprio(p);
      /*
       * SCHED_BATCH tasks are treated as perpetual CPU hogs:
       */
      if (policy == SCHED_BATCH)
            p->sleep_avg = 0;
      set_load_weight(p);
}

/**
 * sched_setscheduler - change the scheduling policy and/or RT priority of
 * a thread.
 * @p: the task in question.
 * @policy: new policy.
 * @param: structure containing the new RT priority.
 */
int sched_setscheduler(struct task_struct *p, int policy,
                   struct sched_param *param)
{
      int retval, oldprio, oldpolicy = -1;
      struct prio_array *array;
      unsigned long flags;
      struct rq *rq;

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

      /*
       * Allow unprivileged RT tasks to decrease priority:
       */
      if (!capable(CAP_SYS_NICE)) {
            /*
             * can't change policy, except between SCHED_NORMAL
             * and SCHED_BATCH:
             */
            if (((policy != SCHED_NORMAL && p->policy != SCHED_BATCH) &&
                  (policy != SCHED_BATCH && p->policy != SCHED_NORMAL)) &&
                        !p->signal->rlim[RLIMIT_RTPRIO].rlim_cur)
                  return -EPERM;
            /* can't increase priority */
            if ((policy != SCHED_NORMAL && policy != SCHED_BATCH) &&
                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;
      /*
       * make sure no PI-waiters arrive (or leave) while we are
       * changing the priority of the task:
       */
      spin_lock_irqsave(&p->pi_lock, flags);
      /*
       * To be able to change p->policy safely, the apropriate
       * runqueue lock must be held.
       */
      rq = __task_rq_lock(p);
      /* recheck policy now with rq lock held */
      if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
            policy = oldpolicy = -1;
            __task_rq_unlock(rq);
            spin_unlock_irqrestore(&p->pi_lock, flags);
            goto recheck;
      }
      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);
      spin_unlock_irqrestore(&p->pi_lock, flags);

      rt_mutex_adjust_pi(p);

      return 0;
}
EXPORT_SYMBOL_GPL(sched_setscheduler);

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

      if (!param || pid < 0)
            return -EINVAL;
      if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
            return -EFAULT;
      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)
{
      /* negative values for policy are not valid */
      if (policy < 0)
            return -EINVAL;

      return do_sched_setscheduler(pid, policy, param);
}

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

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

      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;
      struct task_struct *p;
      int retval = -EINVAL;

      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)
{
      cpumask_t cpus_allowed;
      struct task_struct *p;
      int retval;

      lock_cpu_hotplug();
      read_lock(&tasklist_lock);

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

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

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

      retval = security_task_setscheduler(p, 0, NULL);
      if (retval)
            goto out_unlock;

      cpus_allowed = cpuset_cpus_allowed(p);
      cpus_and(new_mask, new_mask, cpus_allowed);
      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)
{
      struct task_struct *p;
      int retval;

      lock_cpu_hotplug();
      read_lock(&tasklist_lock);

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

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

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

out_unlock:
      read_unlock(&tasklist_lock);
      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)
{
      struct rq *rq = this_rq_lock();
      struct prio_array *array = current->array, *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);
      spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
      _raw_spin_unlock(&rq->lock);
      preempt_enable_no_resched();

      schedule();

      return 0;
}

static inline int __resched_legal(int expected_preempt_count)
{
      if (unlikely(preempt_count() != expected_preempt_count))
            return 0;
      if (unlikely(system_state != SYSTEM_RUNNING))
            return 0;
      return 1;
}

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

int __sched cond_resched(void)
{
      if (need_resched() && __resched_legal(0)) {
            __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() && __resched_legal(1)) {
            spin_release(&lock->dep_map, 1, _THIS_IP_);
            _raw_spin_unlock(lock);
            preempt_enable_no_resched();
            __cond_resched();
            ret = 1;
            spin_lock(lock);
      }
      return ret;
}
EXPORT_SYMBOL(cond_resched_lock);

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

      if (need_resched() && __resched_legal(0)) {
            raw_local_irq_disable();
            _local_bh_enable();
            raw_local_irq_enable();
            __cond_resched();
            local_bh_disable();
            return 1;
      }
      return 0;
}
EXPORT_SYMBOL(cond_resched_softirq);

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

/*
 * This task is about to go to sleep on IO.  Increment rq->nr_iowait so
 * that process accounting knows that this is a task in IO wait state.
 *
 * But don't do that if it is a deliberate, throttling IO wait (this task
 * has set its backing_dev_info: the queue against which it should throttle)
 */
void __sched io_schedule(void)
{
      struct rq *rq = &__raw_get_cpu_var(runqueues);

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

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

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

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

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

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

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

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

      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 const char stat_nam[] = "RSDTtZX";

static void show_task(struct task_struct *p)
{
      struct task_struct *relative;
      unsigned long free = 0;
      unsigned state;

      state = p->state ? __ffs(p->state) + 1 : 0;
      printk("%-13.13s %c", p->comm,
            state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?');
#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)
{
      struct task_struct *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);
      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(struct task_struct *idle, int cpu)
{
      struct rq *rq = cpu_rq(cpu);
      unsigned long flags;

      idle->timestamp = sched_clock();
      idle->sleep_avg = 0;
      idle->array = NULL;
      idle->prio = idle->normal_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 struct migration_req structure in the source CPU's
 *    runqueue and wake up that CPU's migration thread.
 * 2) we down() the locked semaphore => thread blocks.
 * 3) migration thread wakes up (implicitly it forces the migrated
 *    thread off the CPU)
 * 4) it gets the migration request and checks whether the migrated
 *    task is still in the wrong runqueue.
 * 5) if it's in the wrong runqueue then the migration thread removes
 *    it and puts it into the right queue.
 * 6) migration thread up()s the semaphore.
 * 7) we wake up and the migration is done.
 */

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

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

      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.
 *
 * Returns non-zero if task was successfully migrated.
 */
static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
{
      struct rq *rq_dest, *rq_src;
      int ret = 0;

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

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

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

      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);
            if (TASK_PREEMPTS_CURR(p, rq_dest))
                  resched_task(rq_dest->curr);
      }
      ret = 1;
out:
      double_rq_unlock(rq_src, rq_dest);
      return ret;
}

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

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

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

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

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

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

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

#ifdef CONFIG_HOTPLUG_CPU
/* 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 *p)
{
      unsigned long flags;
      cpumask_t mask;
      struct rq *rq;
      int dest_cpu;

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

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

      /* No more Mr. Nice Guy. */
      if (dest_cpu == NR_CPUS) {
            rq = task_rq_lock(p, &flags);
            cpus_setall(p->cpus_allowed);
            dest_cpu = any_online_cpu(p->cpus_allowed);
            task_rq_unlock(rq, &flags);

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

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

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

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

      write_lock_irq(&tasklist_lock);

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

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

      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 the runqueue. Used by CPU offline code.
 */
void sched_idle_next(void)
{
      int this_cpu = smp_processor_id();
      struct rq *rq = cpu_rq(this_cpu);
      struct task_struct *p = rq->idle;
      unsigned long flags;

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

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

      __setscheduler(p, SCHED_FIFO, MAX_RT_PRIO-1);

      /* Add idle task to the _front_ of its 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, struct task_struct *p)
{
      struct rq *rq = cpu_rq(dead_cpu);

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

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

      get_task_struct(p);

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

      put_task_struct(p);
}

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

      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,
                                   struct task_struct, 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 __cpuinit
migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
{
      struct task_struct *p;
      int cpu = (long)hcpu;
      unsigned long flags;
      struct rq *rq;

      switch (action) {
      case CPU_UP_PREPARE:
            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:
            if (!cpu_rq(cpu)->migration_thread)
                  break;
            /* Unbind it from offline cpu so it can run.  Fall thru. */
            kthread_bind(cpu_rq(cpu)->migration_thread,
                       any_online_cpu(cpu_online_map));
            kthread_stop(cpu_rq(cpu)->migration_thread);
            cpu_rq(cpu)->migration_thread = NULL;
            break;

      case CPU_DEAD:
            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)) {
                  struct migration_req *req;

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

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

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

      /* Start one for the 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) do { } while (0)
#endif

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

      /* Following flags need at least 2 groups */
      if (sd->flags & (SD_LOAD_BALANCE |
                   SD_BALANCE_NEWIDLE |
                   SD_BALANCE_FORK |
                   SD_BALANCE_EXEC)) {
            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)
{
      struct rq *rq = cpu_rq(cpu);
      struct sched_domain *tmp;

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

      if (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            1
#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 ] =
/*
 * Architectures may override the migration cost and thus avoid
 * boot-time calibration. Unit is nanoseconds. Mostly useful for
 * virtualized hardware:
 */
#ifdef CONFIG_DEFAULT_MIGRATION_COST
                  CONFIG_DEFAULT_MIGRATION_COST
#else
                  -1LL
#endif
};

/*
 * 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 10% steps:
             */
            size = size * 10 / 9;
      }

      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
            );
      if (system_state == SYSTEM_BOOTING) {
            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)
{
      DECLARE_BITMAP(used_nodes, MAX_NUMNODES);
      cpumask_t span, nodemask;
      int i;

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

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

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

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

      return span;
}
#endif

int sched_smt_power_savings = 0, sched_mc_power_savings = 0;

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

static int cpu_to_cpu_group(int cpu)
{
      return cpu;
}
#endif

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

#if defined(CONFIG_SCHED_MC) && defined(CONFIG_SCHED_SMT)
static int cpu_to_core_group(int cpu)
{
      return first_cpu(cpu_sibling_map[cpu]);
}
#elif defined(CONFIG_SCHED_MC)
static int cpu_to_core_group(int cpu)
{
      return cpu;
}
#endif

static DEFINE_PER_CPU(struct sched_domain, phys_domains);
static struct sched_group *sched_group_phys_bycpu[NR_CPUS];

static int cpu_to_phys_group(int cpu)
{
#ifdef CONFIG_SCHED_MC
      cpumask_t mask = cpu_coregroup_map(cpu);
      return first_cpu(mask);
#elif defined(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);
}
static void init_numa_sched_groups_power(struct sched_group *group_head)
{
      struct sched_group *sg = group_head;
      int j;

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

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

            sg->cpu_power += sd->groups->cpu_power;
      }
      sg = sg->next;
      if (sg != group_head)
            goto next_sg;
}
#endif

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

      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
      for_each_cpu_mask(cpu, *cpu_map) {
            if (sched_group_phys_bycpu[cpu]) {
                  kfree(sched_group_phys_bycpu[cpu]);
                  sched_group_phys_bycpu[cpu] = NULL;
            }
#ifdef CONFIG_SCHED_MC
            if (sched_group_core_bycpu[cpu]) {
                  kfree(sched_group_core_bycpu[cpu]);
                  sched_group_core_bycpu[cpu] = NULL;
            }
#endif
      }
}

/*
 * Build sched domains for a given set of cpus and attach the sched domains
 * to the individual cpus
 */
static int build_sched_domains(const cpumask_t *cpu_map)
{
      int i;
      struct sched_group *sched_group_phys = NULL;
#ifdef CONFIG_SCHED_MC
      struct sched_group *sched_group_core = NULL;
#endif
#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 = kzalloc(sizeof(struct sched_group*)*MAX_NUMNODES,
                                 GFP_KERNEL);
      if (!sched_group_nodes) {
            printk(KERN_WARNING "Can not alloc sched group node list\n");
            return -ENOMEM;
      }
      sched_group_nodes_bycpu[first_cpu(*cpu_map)] = sched_group_nodes;
#endif

      /*
       * 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");
                              goto error;
                        }
                        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

            if (!sched_group_phys) {
                  sched_group_phys
                        = kmalloc(sizeof(struct sched_group) * NR_CPUS,
                                GFP_KERNEL);
                  if (!sched_group_phys) {
                        printk (KERN_WARNING "Can not alloc phys sched"
                                         "group\n");
                        goto error;
                  }
                  sched_group_phys_bycpu[i] = sched_group_phys;
            }

            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_MC
            if (!sched_group_core) {
                  sched_group_core
                        = kmalloc(sizeof(struct sched_group) * NR_CPUS,
                                GFP_KERNEL);
                  if (!sched_group_core) {
                        printk (KERN_WARNING "Can not alloc core sched"
                                         "group\n");
                        goto error;
                  }
                  sched_group_core_bycpu[i] = sched_group_core;
            }

            p = sd;
            sd = &per_cpu(core_domains, i);
            group = cpu_to_core_group(i);
            *sd = SD_MC_INIT;
            sd->span = cpu_coregroup_map(i);
            cpus_and(sd->span, sd->span, *cpu_map);
            sd->parent = p;
            sd->groups = &sched_group_core[group];
#endif

#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

#ifdef CONFIG_SCHED_MC
      /* Set up multi-core groups */
      for_each_cpu_mask(i, *cpu_map) {
            cpumask_t this_core_map = cpu_coregroup_map(i);
            cpus_and(this_core_map, this_core_map, *cpu_map);
            if (i != first_cpu(this_core_map))
                  continue;
            init_sched_build_groups(sched_group_core, this_core_map,
                              &cpu_to_core_group);
      }
#endif


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

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

            init_sched_build_groups(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_node(sizeof(struct sched_group), GFP_KERNEL, i);
            if (!sg) {
                  printk(KERN_WARNING "Can not alloc domain group for "
                        "node %d\n", i);
                  goto error;
            }
            sched_group_nodes[i] = sg;
            for_each_cpu_mask(j, nodemask) {
                  struct sched_domain *sd;
                  sd = &per_cpu(node_domains, j);
                  sd->groups = sg;
            }
            sg->cpu_power = 0;
            sg->cpumask = nodemask;
            sg->next = sg;
            cpus_or(covered, covered, nodemask);
            prev = sg;

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

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

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

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

      /* Calculate CPU power for physical packages and nodes */
#ifdef CONFIG_SCHED_SMT
      for_each_cpu_mask(i, *cpu_map) {
            struct sched_domain *sd;
            sd = &per_cpu(cpu_domains, i);
            sd->groups->cpu_power = SCHED_LOAD_SCALE;
      }
#endif
#ifdef CONFIG_SCHED_MC
      for_each_cpu_mask(i, *cpu_map) {
            int power;
            struct sched_domain *sd;
            sd = &per_cpu(core_domains, i);
            if (sched_smt_power_savings)
                  power = SCHED_LOAD_SCALE * cpus_weight(sd->groups->cpumask);
            else
                  power = SCHED_LOAD_SCALE + (cpus_weight(sd->groups->cpumask)-1)
                                  * SCHED_LOAD_SCALE / 10;
            sd->groups->cpu_power = power;
      }
#endif

      for_each_cpu_mask(i, *cpu_map) {
            struct sched_domain *sd;
#ifdef CONFIG_SCHED_MC
            sd = &per_cpu(phys_domains, i);
            if (i != first_cpu(sd->groups->cpumask))
                  continue;

            sd->groups->cpu_power = 0;
            if (sched_mc_power_savings || sched_smt_power_savings) {
                  int j;

                  for_each_cpu_mask(j, sd->groups->cpumask) {
                        struct sched_domain *sd1;
                        sd1 = &per_cpu(core_domains, j);
                        /*
                         * for each core we will add once
                         * to the group in physical domain
                         */
                        if (j != first_cpu(sd1->groups->cpumask))
                              continue;

                        if (sched_smt_power_savings)
                              sd->groups->cpu_power += sd1->groups->cpu_power;
                        else
                              sd->groups->cpu_power += SCHED_LOAD_SCALE;
                  }
            } else
                  /*
                   * This has to be < 2 * SCHED_LOAD_SCALE
                   * Lets keep it SCHED_LOAD_SCALE, so that
                   * while calculating NUMA group's cpu_power
                   * we can simply do
                   *  numa_group->cpu_power += phys_group->cpu_power;
                   *
                   * See "only add power once for each physical pkg"
                   * comment below
                   */
                  sd->groups->cpu_power = SCHED_LOAD_SCALE;
#else
            int power;
            sd = &per_cpu(phys_domains, i);
            if (sched_smt_power_savings)
                  power = SCHED_LOAD_SCALE * cpus_weight(sd->groups->cpumask);
            else
                  power = SCHED_LOAD_SCALE;
            sd->groups->cpu_power = power;
#endif
      }

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

      if (sched_group_allnodes) {
            int group = cpu_to_allnodes_group(first_cpu(*cpu_map));
            struct sched_group *sg = &sched_group_allnodes[group];

            init_numa_sched_groups_power(sg);
      }
#endif

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

      return 0;

error:
      free_sched_groups(cpu_map);
      return -ENOMEM;
}
/*
 * Set up scheduler domains and groups.  Callers must hold the hotplug lock.
 */
static int arch_init_sched_domains(const cpumask_t *cpu_map)
{
      cpumask_t cpu_default_map;
      int err;

      /*
       * 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);

      err = build_sched_domains(&cpu_default_map);

      return err;
}

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

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

      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
 */
int partition_sched_domains(cpumask_t *partition1, cpumask_t *partition2)
{
      cpumask_t change_map;
      int err = 0;

      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))
            err = build_sched_domains(partition1);
      if (!err && !cpus_empty(*partition2))
            err = build_sched_domains(partition2);

      return err;
}

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

      lock_cpu_hotplug();
      detach_destroy_domains(&cpu_online_map);
      err = arch_init_sched_domains(&cpu_online_map);
      unlock_cpu_hotplug();

      return err;
}

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

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

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

      ret = arch_reinit_sched_domains();

      return ret ? ret : count;
}

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

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

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

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


#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)
{
      int i, j, k;

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

            rq = cpu_rq(i);
            spin_lock_init(&rq->lock);
            lockdep_set_class(&rq->lock, &rq->rq_lock_key);
            rq->nr_running = 0;
            rq->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);
            }
      }

      set_load_weight(&init_task);

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

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

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

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

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

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

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

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

            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);
            spin_unlock_irqrestore(&p->pi_lock, 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!
 */
struct task_struct *curr_task(int cpu)
{
      return cpu_curr(cpu);
}

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

#endif

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