Cross-Referenced Linux and Device Driver Code

   /*
    *  kernel/sched.c
    *
    *  Kernel scheduler and related syscalls
    *
    *  Copyright (C) 1991-2002  Linus Torvalds
    *  Copyright (C) 2004 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
    *
    *  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
   *  2004-10-13  Real-Time Preemption support by Ingo Molnar
   *  2007-04-15  Work begun on replacing all interactivity tuning with a
   *              fair scheduling design by Con Kolivas.
   *  2007-05-05  Load balancing (smp-nice) and other improvements
   *              by Peter Williams
   *  2007-05-06  Interactivity improvements to CFS by Mike Galbraith
   *  2007-07-01  Group scheduling enhancements by Srivatsa Vaddagiri
   *  2007-11-29  RT balancing improvements by Steven Rostedt, Gregory Haskins,
   *              Thomas Gleixner, Mike Kravetz
   */
  
  #include <linux/mm.h>
  #include <linux/module.h>
  #include <linux/nmi.h>
  #include <linux/init.h>
  #include <linux/uaccess.h>
  #include <linux/highmem.h>
  #include <linux/smp_lock.h>
  #include <asm/mmu_context.h>
  #include <linux/interrupt.h>
  #include <linux/capability.h>
  #include <linux/completion.h>
  #include <linux/kernel_stat.h>
  #include <linux/debug_locks.h>
  #include <linux/security.h>
  #include <linux/notifier.h>
  #include <linux/profile.h>
  #include <linux/freezer.h>
  #include <linux/vmalloc.h>
  #include <linux/blkdev.h>
  #include <linux/delay.h>
  #include <linux/pid_namespace.h>
  #include <linux/smp.h>
  #include <linux/threads.h>
  #include <linux/timer.h>
  #include <linux/rcupdate.h>
  #include <linux/cpu.h>
  #include <linux/cpuset.h>
  #include <linux/percpu.h>
  #include <linux/kthread.h>
  #include <linux/seq_file.h>
  #include <linux/sysctl.h>
  #include <linux/syscalls.h>
  #include <linux/times.h>
  #include <linux/kallsyms.h>
  #include <linux/tsacct_kern.h>
  #include <linux/kprobes.h>
  #include <linux/delayacct.h>
  #include <linux/reciprocal_div.h>
  #include <linux/unistd.h>
  #include <linux/pagemap.h>
  #include <linux/hrtimer.h>
  #include <linux/ftrace.h>
  
  #include <asm/tlb.h>
  #include <asm/irq_regs.h>
  
  #include "sched_cpupri.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)
  
  #define __PRIO(prio) \
          ((prio) <= 99 ? 199 - (prio) : (prio) - 120)
  
  #define PRIO(p) __PRIO((p)->prio)
  
  /*
   * 'User priority' is the nice value converted to something we
   * can work with better when scaling various scheduler parameters,
   * it's a [ 0 ... 39 ] range.
   */
  #define USER_PRIO(p)            ((p)-MAX_RT_PRIO)
  #define TASK_USER_PRIO(p)       USER_PRIO((p)->static_prio)
 #define MAX_USER_PRIO           (USER_PRIO(MAX_PRIO))
 
 /*
  * Helpers for converting nanosecond timing to jiffy resolution
  */
 #define NS_TO_JIFFIES(TIME)     ((unsigned long)(TIME) / (NSEC_PER_SEC / HZ))
 
 #define NICE_0_LOAD             SCHED_LOAD_SCALE
 #define NICE_0_SHIFT            SCHED_LOAD_SHIFT
 
 #if (BITS_PER_LONG < 64)
 #define JIFFIES_TO_NS64(TIME) \
         ((unsigned long long)(TIME) * ((unsigned long) (1000000000 / HZ)))
 
 #define NS64_TO_JIFFIES(TIME) \
         ((((unsigned long long)((TIME)) >> BITS_PER_LONG) * \
         (1 + NS_TO_JIFFIES(~0UL))) + NS_TO_JIFFIES((unsigned long)(TIME)))
 #else /* BITS_PER_LONG < 64 */
 
 #define NS64_TO_JIFFIES(TIME) NS_TO_JIFFIES(TIME)
 #define JIFFIES_TO_NS64(TIME) JIFFIES_TO_NS(TIME)
 
 #endif /* BITS_PER_LONG < 64 */
 
 /*
  * These are the 'tuning knobs' of the scheduler:
  *
  * default timeslice is 100 msecs (used only for SCHED_RR tasks).
  * Timeslices get refilled after they expire.
  */
 #define DEF_TIMESLICE           (100 * HZ / 1000)
 
 #ifdef CONFIG_SMP
 /*
  * Divide a load by a sched group cpu_power : (load / sg->__cpu_power)
  * Since cpu_power is a 'constant', we can use a reciprocal divide.
  */
 static inline u32 sg_div_cpu_power(const struct sched_group *sg, u32 load)
 {
         return reciprocal_divide(load, sg->reciprocal_cpu_power);
 }
 
 /*
  * Each time a sched group cpu_power is changed,
  * we must compute its reciprocal value
  */
 static inline void sg_inc_cpu_power(struct sched_group *sg, u32 val)
 {
         sg->__cpu_power += val;
         sg->reciprocal_cpu_power = reciprocal_value(sg->__cpu_power);
 }
 #endif
 
 #define TASK_PREEMPTS_CURR(p, rq) \
         ((p)->prio < (rq)->curr->prio)
 
 /*
  * Tweaks for current
  */
 
 #ifdef CURRENT_PTR
 struct task_struct * const ___current = &init_task;
 struct task_struct ** const current_ptr = (struct task_struct ** const)&___current;
 struct thread_info * const current_ti = &init_thread_union.thread_info;
 struct thread_info ** const current_ti_ptr = (struct thread_info ** const)&current_ti;
 
 EXPORT_SYMBOL(___current);
 EXPORT_SYMBOL(current_ti);
 
 /*
  * The scheduler itself doesnt want 'current' to be cached
  * during context-switches:
  */
 # undef current
 # define current __current()
 # undef current_thread_info
 # define current_thread_info() __current_thread_info()
 #endif
 
 static inline int rt_policy(int policy)
 {
         if (unlikely(policy == SCHED_FIFO) || unlikely(policy == SCHED_RR))
                 return 1;
         return 0;
 }
 
 static inline int task_has_rt_policy(struct task_struct *p)
 {
         return rt_policy(p->policy);
 }
 
 /*
  * This is the priority-queue data structure of the RT scheduling class:
  */
 struct rt_prio_array {
         DECLARE_BITMAP(bitmap, MAX_RT_PRIO+1); /* include 1 bit for delimiter */
         struct list_head xqueue[MAX_RT_PRIO];  /* exclusive queue */
         struct list_head squeue[MAX_RT_PRIO];  /* shared queue */
 };
 
 #ifdef CONFIG_GROUP_SCHED
 
 #include <linux/cgroup.h>
 
 struct cfs_rq;
 
 static LIST_HEAD(task_groups);
 
 /* task group related information */
 struct task_group {
 #ifdef CONFIG_CGROUP_SCHED
         struct cgroup_subsys_state css;
 #endif
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
         /* schedulable entities of this group on each cpu */
         struct sched_entity **se;
         /* runqueue "owned" by this group on each cpu */
         struct cfs_rq **cfs_rq;
         unsigned long shares;
 #endif
 
 #ifdef CONFIG_RT_GROUP_SCHED
         struct sched_rt_entity **rt_se;
         struct rt_rq **rt_rq;
 
         u64 rt_runtime;
 #endif
 
         struct rcu_head rcu;
         struct list_head list;
 };
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 /* Default task group's sched entity on each cpu */
 static DEFINE_PER_CPU(struct sched_entity, init_sched_entity);
 /* Default task group's cfs_rq on each cpu */
 static DEFINE_PER_CPU(struct cfs_rq, init_cfs_rq) ____cacheline_aligned_in_smp;
 
 static struct sched_entity *init_sched_entity_p[NR_CPUS];
 static struct cfs_rq *init_cfs_rq_p[NR_CPUS];
 #endif
 
 #ifdef CONFIG_RT_GROUP_SCHED
 static DEFINE_PER_CPU(struct sched_rt_entity, init_sched_rt_entity);
 static DEFINE_PER_CPU(struct rt_rq, init_rt_rq) ____cacheline_aligned_in_smp;
 
 static struct sched_rt_entity *init_sched_rt_entity_p[NR_CPUS];
 static struct rt_rq *init_rt_rq_p[NR_CPUS];
 #endif
 
 /* task_group_lock serializes add/remove of task groups and also changes to
  * a task group's cpu shares.
  */
 static DEFINE_SPINLOCK(task_group_lock);
 
 /* doms_cur_mutex serializes access to doms_cur[] array */
 static DEFINE_MUTEX(doms_cur_mutex);
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 #ifdef CONFIG_USER_SCHED
 # define INIT_TASK_GROUP_LOAD   (2*NICE_0_LOAD)
 #else
 # define INIT_TASK_GROUP_LOAD   NICE_0_LOAD
 #endif
 
 static int init_task_group_load = INIT_TASK_GROUP_LOAD;
 #endif
 
 /* Default task group.
  *      Every task in system belong to this group at bootup.
  */
 struct task_group init_task_group = {
 #ifdef CONFIG_FAIR_GROUP_SCHED
         .se     = init_sched_entity_p,
         .cfs_rq = init_cfs_rq_p,
 #endif
 
 #ifdef CONFIG_RT_GROUP_SCHED
         .rt_se  = init_sched_rt_entity_p,
         .rt_rq  = init_rt_rq_p,
 #endif
 };
 
 /* return group to which a task belongs */
 static inline struct task_group *task_group(struct task_struct *p)
 {
         struct task_group *tg;
 
 #ifdef CONFIG_USER_SCHED
         tg = p->user->tg;
 #elif defined(CONFIG_CGROUP_SCHED)
         tg = container_of(task_subsys_state(p, cpu_cgroup_subsys_id),
                                 struct task_group, css);
 #else
         tg = &init_task_group;
 #endif
         return tg;
 }
 
 /* Change a task's cfs_rq and parent entity if it moves across CPUs/groups */
 static inline void set_task_rq(struct task_struct *p, unsigned int cpu)
 {
 #ifdef CONFIG_FAIR_GROUP_SCHED
         p->se.cfs_rq = task_group(p)->cfs_rq[cpu];
         p->se.parent = task_group(p)->se[cpu];
 #endif
 
 #ifdef CONFIG_RT_GROUP_SCHED
         p->rt.rt_rq  = task_group(p)->rt_rq[cpu];
         p->rt.parent = task_group(p)->rt_se[cpu];
 #endif
 }
 
 static inline void lock_doms_cur(void)
 {
         mutex_lock(&doms_cur_mutex);
 }
 
 static inline void unlock_doms_cur(void)
 {
         mutex_unlock(&doms_cur_mutex);
 }
 
 #else
 
 static inline void set_task_rq(struct task_struct *p, unsigned int cpu) { }
 static inline void lock_doms_cur(void) { }
 static inline void unlock_doms_cur(void) { }
 
 #endif  /* CONFIG_GROUP_SCHED */
 
 /* CFS-related fields in a runqueue */
 struct cfs_rq {
         struct load_weight load;
         unsigned long nr_running;
 
         u64 exec_clock;
         u64 min_vruntime;
 
         struct rb_root tasks_timeline;
         struct rb_node *rb_leftmost;
         struct rb_node *rb_load_balance_curr;
         /* 'curr' points to currently running entity on this cfs_rq.
          * It is set to NULL otherwise (i.e when none are currently running).
          */
         struct sched_entity *curr, *next;
 
         unsigned long nr_spread_over;
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
         struct rq *rq;  /* cpu runqueue to which this cfs_rq is attached */
 
         /*
          * leaf cfs_rqs are those that hold tasks (lowest schedulable entity in
          * a hierarchy). Non-leaf lrqs hold other higher schedulable entities
          * (like users, containers etc.)
          *
          * leaf_cfs_rq_list ties together list of leaf cfs_rq's in a cpu. This
          * list is used during load balance.
          */
         struct list_head leaf_cfs_rq_list;
         struct task_group *tg;  /* group that "owns" this runqueue */
 #endif
 };
 
 /* Real-Time classes' related field in a runqueue: */
 struct rt_rq {
         struct rt_prio_array active;
         unsigned long rt_nr_running;
 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
         int highest_prio; /* highest queued rt task prio */
 #endif
 #ifdef CONFIG_SMP
         unsigned long rt_nr_migratory;
         int overloaded;
 #endif
         unsigned long rt_nr_uninterruptible;
         int rt_throttled;
         u64 rt_time;
 
 #ifdef CONFIG_RT_GROUP_SCHED
         unsigned long rt_nr_boosted;
 
         struct rq *rq;
         struct list_head leaf_rt_rq_list;
         struct task_group *tg;
         struct sched_rt_entity *rt_se;
 #endif
 };
 
 #ifdef CONFIG_SMP
 
 /*
  * We add the notion of a root-domain which will be used to define per-domain
  * variables. Each exclusive cpuset essentially defines an island domain by
  * fully partitioning the member cpus from any other cpuset. Whenever a new
  * exclusive cpuset is created, we also create and attach a new root-domain
  * object.
  *
  */
 struct root_domain {
         atomic_t refcount;
         cpumask_t span;
         cpumask_t online;
 
         /*
          * The "RT overload" flag: it gets set if a CPU has more than
          * one runnable RT task.
          */
         cpumask_t rto_mask;
         atomic_t rto_count;
 #ifdef CONFIG_SMP
         struct cpupri cpupri;
 #endif
 };
 
 /*
  * By default the system creates a single root-domain with all cpus as
  * members (mimicking the global state we have today).
  */
 static struct root_domain def_root_domain;
 
 #endif
 
 /*
  * This is the main, per-CPU runqueue data structure.
  *
  * Locking rule: those places that want to lock multiple runqueues
  * (such as the load balancing or the thread migration code), lock
  * acquire operations must be ordered by ascending &runqueue.
  */
 struct rq {
         /* runqueue lock: */
         raw_spinlock_t lock;
 
         /*
          * nr_running and cpu_load should be in the same cacheline because
          * remote CPUs use both these fields when doing load calculation.
          */
         unsigned long nr_running;
         #define CPU_LOAD_IDX_MAX 5
         unsigned long cpu_load[CPU_LOAD_IDX_MAX];
         unsigned char idle_at_tick;
 #ifdef CONFIG_NO_HZ
         unsigned char in_nohz_recently;
 #endif
         /* capture load from *all* tasks on this cpu: */
         struct load_weight load;
         unsigned long nr_load_updates;
         u64 nr_switches;
 
         struct cfs_rq cfs;
         struct rt_rq rt;
         u64 rt_period_expire;
         int rt_throttled;
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
         /* list of leaf cfs_rq on this cpu: */
         struct list_head leaf_cfs_rq_list;
 #endif
 #ifdef CONFIG_RT_GROUP_SCHED
         struct list_head leaf_rt_rq_list;
 #endif
 
         /*
          * 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 switch_timestamp;
         unsigned long slice_avg;
         struct task_struct *curr, *idle;
         unsigned long next_balance;
         struct mm_struct *prev_mm;
 
         u64 clock;
 
         atomic_t nr_iowait;
 
 #ifdef CONFIG_SMP
         struct root_domain *rd;
         struct sched_domain *sd;
 
         /* For active balancing */
         int active_balance;
         int push_cpu;
         /* cpu of this runqueue: */
         int cpu;
         int online;
 
         struct task_struct *migration_thread;
         struct list_head migration_queue;
 #endif
 
 #ifdef CONFIG_SCHED_HRTICK
         unsigned long hrtick_flags;
         ktime_t hrtick_expire;
         struct hrtimer hrtick_timer;
 #endif
 
 #ifdef CONFIG_SCHEDSTATS
         /* latency stats */
         struct sched_info rq_sched_info;
 
         /* sys_sched_yield() stats */
         unsigned int yld_exp_empty;
         unsigned int yld_act_empty;
         unsigned int yld_both_empty;
         unsigned int yld_count;
 
         /* schedule() stats */
         unsigned int sched_switch;
         unsigned int sched_count;
         unsigned int sched_goidle;
 
         /* try_to_wake_up() stats */
         unsigned int ttwu_count;
         unsigned int ttwu_local;
 
         /* BKL stats */
         unsigned int bkl_count;
 
         /* RT-overload stats: */
         unsigned long rto_schedule;
         unsigned long rto_schedule_tail;
         unsigned long rto_wakeup;
         unsigned long rto_pulled;
         unsigned long rto_pushed;
 #endif
         struct lock_class_key rq_lock_key;
 };
 
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
 
 static inline void check_preempt_curr(struct rq *rq, struct task_struct *p)
 {
         rq->curr->sched_class->check_preempt_curr(rq, p);
 }
 
 static inline int cpu_of(struct rq *rq)
 {
 #ifdef CONFIG_SMP
         return rq->cpu;
 #else
         return 0;
 #endif
 }
 
 #include "sched_trace.h"
 
 /*
  * 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)
 
 static inline void update_rq_clock(struct rq *rq)
 {
         rq->clock = sched_clock_cpu(cpu_of(rq));
 }
 
 unsigned long rt_needs_cpu(int cpu)
 {
         struct rq *rq = cpu_rq(cpu);
         u64 delta;
 
         if (!rq->rt_throttled)
                 return 0;
 
         if (rq->clock > rq->rt_period_expire)
                 return 1;
 
         delta = rq->rt_period_expire - rq->clock;
         do_div(delta, NSEC_PER_SEC / HZ);
 
         return (unsigned long)delta;
 }
 
 /*
  * Tunables that become constants when CONFIG_SCHED_DEBUG is off:
  */
 #ifdef CONFIG_SCHED_DEBUG
 # define const_debug __read_mostly
 #else
 # define const_debug static const
 #endif
 
 /**
  * runqueue_is_locked
  *
  * Returns true if the current cpu runqueue is locked.
  * This interface allows printk to be called with the runqueue lock
  * held and know whether or not it is OK to wake up the klogd.
  */
 int runqueue_is_locked(void)
 {
         int cpu = get_cpu();
         struct rq *rq = cpu_rq(cpu);
         int ret;
 
         ret = spin_is_locked(&rq->lock);
         put_cpu();
         return ret;
 }
 
 #ifndef CONFIG_SMP
 int task_is_current(struct task_struct *task)
 {
         return task_rq(task)->curr == task;
 }
 #endif
 
 /*
  * Debugging: various feature bits
  */
 enum {
         SCHED_FEAT_NEW_FAIR_SLEEPERS    = 1,
         SCHED_FEAT_WAKEUP_PREEMPT       = 2,
         SCHED_FEAT_START_DEBIT          = 4,
         SCHED_FEAT_HRTICK               = 8,
         SCHED_FEAT_DOUBLE_TICK          = 16,
 };
 
 const_debug unsigned int sysctl_sched_features =
                 SCHED_FEAT_NEW_FAIR_SLEEPERS    * 1 |
                 SCHED_FEAT_WAKEUP_PREEMPT       * 1 |
                 SCHED_FEAT_START_DEBIT          * 1 |
                 SCHED_FEAT_HRTICK               * 1 |
                 SCHED_FEAT_DOUBLE_TICK          * 0;
 
 #define sched_feat(x) (sysctl_sched_features & SCHED_FEAT_##x)
 
 /*
  * Number of tasks to iterate in a single balance run.
  * Limited because this is done with IRQs disabled.
  */
 #ifdef CONFIG_PREEMPT_RT
 const_debug unsigned int sysctl_sched_nr_migrate = 8;
 #else
 const_debug unsigned int sysctl_sched_nr_migrate = 32;
 #endif
 
 /*
  * period over which we measure -rt task cpu usage in us.
  * default: 1s
  */
 unsigned int sysctl_sched_rt_period = 1000000;
 
 static __read_mostly int scheduler_running;
 
 /*
  * part of the period that we allow rt tasks to run in us.
  * default: 0.95s
  */
 /* int sysctl_sched_rt_runtime = 950000; */
 int sysctl_sched_rt_runtime = -1;
 
 /*
  * single value that denotes runtime == period, ie unlimited time.
  */
 #define RUNTIME_INF     ((u64)~0ULL)
 
 /*
  * We really dont want to do anything complex within switch_to()
  * on PREEMPT_RT - this check enforces this.
  */
 #ifdef prepare_arch_switch
 # ifdef CONFIG_PREEMPT_RT
 #   error FIXME
 # else
 #  define _finish_arch_switch finish_arch_switch
 # endif
 #endif
 
 #ifndef prepare_arch_switch
 # define prepare_arch_switch(next)      do { } while (0)
 #endif
 #ifndef finish_arch_switch
 # define _finish_arch_switch(prev)      do { } while (0)
 #endif
 
 static inline int task_current(struct rq *rq, struct task_struct *p)
 {
         return rq->curr == p;
 }
 
 static inline int task_running(struct rq *rq, struct task_struct *p)
 {
 #ifdef CONFIG_SMP
         return p->oncpu;
 #else
         return task_current(rq, p);
 #endif
 }
 
 #ifndef __ARCH_WANT_UNLOCKED_CTXSW
 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
 }
 
 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
 #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(&rq->lock);
 }
 
 #else /* __ARCH_WANT_UNLOCKED_CTXSW */
 
 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
 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
         local_irq_disable();
 #endif
 }
 #endif /* __ARCH_WANT_UNLOCKED_CTXSW */
 
 /*
  * __task_rq_lock - lock the runqueue a given task resides on.
  * Must be called interrupts disabled.
  */
 static inline struct rq *__task_rq_lock(struct task_struct *p)
         __acquires(rq->lock)
 {
         for (;;) {
                 struct rq *rq = task_rq(p);
                 spin_lock(&rq->lock);
                 if (likely(rq == task_rq(p)))
                         return rq;
                 spin_unlock(&rq->lock);
         }
 }
 
 /*
  * task_rq_lock - lock the runqueue a given task resides on and disable
  * interrupts. Note the ordering: we can safely lookup the task_rq without
  * explicitly disabling preemption.
  */
 static struct rq *task_rq_lock(struct task_struct *p, unsigned long *flags)
         __acquires(rq->lock)
 {
         struct rq *rq;
 
         for (;;) {
                 local_irq_save(*flags);
                 rq = task_rq(p);
                 spin_lock(&rq->lock);
                 if (likely(rq == task_rq(p)))
                         return rq;
                 spin_unlock_irqrestore(&rq->lock, *flags);
         }
 }
 
 static void __task_rq_unlock(struct rq *rq)
         __releases(rq->lock)
 {
         spin_unlock(&rq->lock);
 }
 
 static inline void task_rq_unlock(struct rq *rq, unsigned long *flags)
         __releases(rq->lock)
 {
         spin_unlock_irqrestore(&rq->lock, *flags);
 }
 
 /*
  * this_rq_lock - lock this runqueue and disable interrupts.
  */
 static struct rq *this_rq_lock(void)
         __acquires(rq->lock)
 {
         struct rq *rq;
 
         local_irq_disable();
         rq = this_rq();
         spin_lock(&rq->lock);
 
         return rq;
 }
 
 static void __resched_task(struct task_struct *p, int tif_bit);
 
 static inline void resched_task(struct task_struct *p)
 {
         __resched_task(p, TIF_NEED_RESCHED);
 }
 
 #ifdef CONFIG_SCHED_HRTICK
 /*
  * Use HR-timers to deliver accurate preemption points.
  *
  * Its all a bit involved since we cannot program an hrt while holding the
  * rq->lock. So what we do is store a state in in rq->hrtick_* and ask for a
  * reschedule event.
  *
  * When we get rescheduled we reprogram the hrtick_timer outside of the
  * rq->lock.
  */
 static inline void resched_hrt(struct task_struct *p)
 {
         __resched_task(p, TIF_HRTICK_RESCHED);
 }
 
 static inline void resched_rq(struct rq *rq)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&rq->lock, flags);
         resched_task(rq->curr);
         spin_unlock_irqrestore(&rq->lock, flags);
 }
 
 enum {
         HRTICK_SET,             /* re-programm hrtick_timer */
         HRTICK_RESET,           /* not a new slice */
         HRTICK_BLOCK,           /* stop hrtick operations */
 };
 
 /*
  * Use hrtick when:
  *  - enabled by features
  *  - hrtimer is actually high res
  */
 static inline int hrtick_enabled(struct rq *rq)
 {
         if (!sched_feat(HRTICK))
                 return 0;
         if (unlikely(test_bit(HRTICK_BLOCK, &rq->hrtick_flags)))
                 return 0;
         return hrtimer_is_hres_active(&rq->hrtick_timer);
 }
 
 /*
  * Called to set the hrtick timer state.
  *
  * called with rq->lock held and irqs disabled
  */
 static void hrtick_start(struct rq *rq, u64 delay, int reset)
 {
         assert_spin_locked(&rq->lock);
 
         /*
          * preempt at: now + delay
          */
         rq->hrtick_expire =
                 ktime_add_ns(rq->hrtick_timer.base->get_time(), delay);
         /*
          * indicate we need to program the timer
          */
         __set_bit(HRTICK_SET, &rq->hrtick_flags);
         if (reset)
                 __set_bit(HRTICK_RESET, &rq->hrtick_flags);
 
         /*
          * New slices are called from the schedule path and don't need a
          * forced reschedule.
          */
         if (reset)
                 resched_hrt(rq->curr);
 }
 
 static void hrtick_clear(struct rq *rq)
 {
         if (hrtimer_active(&rq->hrtick_timer))
                 hrtimer_cancel(&rq->hrtick_timer);
 }
 
 /*
  * Update the timer from the possible pending state.
  */
 static void hrtick_set(struct rq *rq)
 {
         ktime_t time;
         int set, reset;
         unsigned long flags;
 
         WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
 
         spin_lock_irqsave(&rq->lock, flags);
         set = __test_and_clear_bit(HRTICK_SET, &rq->hrtick_flags);
         reset = __test_and_clear_bit(HRTICK_RESET, &rq->hrtick_flags);
         time = rq->hrtick_expire;
         clear_thread_flag(TIF_HRTICK_RESCHED);
         spin_unlock_irqrestore(&rq->lock, flags);
 
         if (set) {
                 hrtimer_start(&rq->hrtick_timer, time, HRTIMER_MODE_ABS);
                 if (reset && !hrtimer_active(&rq->hrtick_timer))
                         resched_rq(rq);
         } else
                 hrtick_clear(rq);
 }
 
 /*
  * High-resolution timer tick.
  * Runs from hardirq context with interrupts disabled.
  */
 static enum hrtimer_restart hrtick(struct hrtimer *timer)
 {
         struct rq *rq = container_of(timer, struct rq, hrtick_timer);
 
         WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
 
         spin_lock(&rq->lock);
         update_rq_clock(rq);
         rq->curr->sched_class->task_tick(rq, rq->curr, 1);
         spin_unlock(&rq->lock);
 
         return HRTIMER_NORESTART;
 }
 
 static void hotplug_hrtick_disable(int cpu)
 {
         struct rq *rq = cpu_rq(cpu);
         unsigned long flags;
 
         spin_lock_irqsave(&rq->lock, flags);
         rq->hrtick_flags = 0;
         __set_bit(HRTICK_BLOCK, &rq->hrtick_flags);
         spin_unlock_irqrestore(&rq->lock, flags);
 
         hrtick_clear(rq);
 }
 
 static void hotplug_hrtick_enable(int cpu)
 {
         struct rq *rq = cpu_rq(cpu);
         unsigned long flags;
 
         spin_lock_irqsave(&rq->lock, flags);
         __clear_bit(HRTICK_BLOCK, &rq->hrtick_flags);
         spin_unlock_irqrestore(&rq->lock, flags);
 }
 
 static int
 hotplug_hrtick(struct notifier_block *nfb, unsigned long action, void *hcpu)
 {
         int cpu = (int)(long)hcpu;
 
         switch (action) {
         case CPU_UP_CANCELED:
         case CPU_UP_CANCELED_FROZEN:
         case CPU_DOWN_PREPARE:
         case CPU_DOWN_PREPARE_FROZEN:
         case CPU_DEAD:
         case CPU_DEAD_FROZEN:
                 hotplug_hrtick_disable(cpu);
                 return NOTIFY_OK;
 
         case CPU_UP_PREPARE:
         case CPU_UP_PREPARE_FROZEN:
         case CPU_DOWN_FAILED:
         case CPU_DOWN_FAILED_FROZEN:
         case CPU_ONLINE:
         case CPU_ONLINE_FROZEN:
                 hotplug_hrtick_enable(cpu);
                 return NOTIFY_OK;
         }
 
         return NOTIFY_DONE;
 }
 
 static void init_hrtick(void)
 {
         hotcpu_notifier(hotplug_hrtick, 0);
 }
 
 static void init_rq_hrtick(struct rq *rq)
 {
         rq->hrtick_flags = 0;
         hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
         rq->hrtick_timer.function = hrtick;
         rq->hrtick_timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ;
 }
 
 void hrtick_resched(void)
 {
         struct rq *rq;
         unsigned long flags;
 
         if (!test_thread_flag(TIF_HRTICK_RESCHED))
                 return;
 
         local_irq_save(flags);
         rq = cpu_rq(smp_processor_id());
         hrtick_set(rq);
         local_irq_restore(flags);
 }
 #else
 static inline void hrtick_clear(struct rq *rq)
 {
 }
 
 static inline void hrtick_set(struct rq *rq)
 {
 }
 
 static inline void init_rq_hrtick(struct rq *rq)
 {
 }
 
 void hrtick_resched(void)
 {
 }
 
 static inline void init_hrtick(void)
 {
 }
 #endif
 
 /*
  * resched_task - mark a task 'to be rescheduled now'.
  *
  * On UP this means the setting of the need_resched flag, on SMP it
  * might also involve a cross-CPU call to trigger the scheduler on
  * the target CPU.
  */
 #ifdef CONFIG_SMP
 
 #ifndef tsk_is_polling
 #define tsk_is_polling(t) test_tsk_thread_flag(t, TIF_POLLING_NRFLAG)
 #endif
 
 static void __resched_task(struct task_struct *p, int tif_bit)
 {
         int cpu;
 
         assert_spin_locked(&task_rq(p)->lock);
 
         if (unlikely(test_tsk_thread_flag(p, tif_bit)))
                 return;
 
         set_tsk_thread_flag(p, tif_bit);
 
         cpu = task_cpu(p);
         if (cpu == smp_processor_id())
                 return;
 
         /* NEED_RESCHED must be visible before we test polling */
         smp_mb();
         if (!tsk_is_polling(p))
                 smp_send_reschedule(cpu);
 }
 
 static void resched_cpu(int cpu)
 {
         struct rq *rq = cpu_rq(cpu);
         unsigned long flags;
 
         if (!spin_trylock_irqsave(&rq->lock, flags))
                 return;
         resched_task(cpu_curr(cpu));
         spin_unlock_irqrestore(&rq->lock, flags);
 }
 
 #ifdef CONFIG_NO_HZ
 /*
  * When add_timer_on() enqueues a timer into the timer wheel of an
  * idle CPU then this timer might expire before the next timer event
  * which is scheduled to wake up that CPU. In case of a completely
  * idle system the next event might even be infinite time into the
  * future. wake_up_idle_cpu() ensures that the CPU is woken up and
  * leaves the inner idle loop so the newly added timer is taken into
  * account when the CPU goes back to idle and evaluates the timer
  * wheel for the next timer event.
  */
 void wake_up_idle_cpu(int cpu)
 {
         struct rq *rq = cpu_rq(cpu);
 
         if (cpu == raw_smp_processor_id())
                 return;
 
         /*
          * This is safe, as this function is called with the timer
          * wheel base lock of (cpu) held. When the CPU is on the way
          * to idle and has not yet set rq->curr to idle then it will
          * be serialized on the timer wheel base lock and take the new
          * timer into account automatically.
          */
         if (rq->curr != rq->idle)
                 return;
 
         /*
          * We can set TIF_RESCHED on the idle task of the other CPU
          * lockless. The worst case is that the other CPU runs the
          * idle task through an additional NOOP schedule()
          */
         set_tsk_thread_flag(rq->idle, TIF_NEED_RESCHED);
 
         /* NEED_RESCHED must be visible before we test polling */
         smp_mb();
         if (!tsk_is_polling(rq->idle))
                 smp_send_reschedule(cpu);
 }
 #endif
 
 #else
 static void __resched_task(struct task_struct *p, int tif_bit)
 {
         assert_spin_locked(&task_rq(p)->lock);
         set_tsk_thread_flag(p, tif_bit);
 }
 #endif
 
 #if BITS_PER_LONG == 32
 # define WMULT_CONST    (~0UL)
 #else
 # define WMULT_CONST    (1UL << 32)
 #endif
 
 #define WMULT_SHIFT     32
 
 /*
  * Shift right and round:
  */
 #define SRR(x, y) (((x) + (1UL << ((y) - 1))) >> (y))
 
 static unsigned long
 calc_delta_mine(unsigned long delta_exec, unsigned long weight,
                 struct load_weight *lw)
 {
         u64 tmp;
 
         if (unlikely(!lw->inv_weight))
                 lw->inv_weight = (WMULT_CONST-lw->weight/2) / (lw->weight+1);
 
         tmp = (u64)delta_exec * weight;
         /*
          * Check whether we'd overflow the 64-bit multiplication:
          */
         if (unlikely(tmp > WMULT_CONST))
                 tmp = SRR(SRR(tmp, WMULT_SHIFT/2) * lw->inv_weight,
                         WMULT_SHIFT/2);
         else
                 tmp = SRR(tmp * lw->inv_weight, WMULT_SHIFT);
 
         return (unsigned long)min(tmp, (u64)(unsigned long)LONG_MAX);
 }
 
 static inline unsigned long
 calc_delta_fair(unsigned long delta_exec, struct load_weight *lw)
 {
         return calc_delta_mine(delta_exec, NICE_0_LOAD, lw);
 }
 
 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
 {
         lw->weight += inc;
         lw->inv_weight = 0;
 }
 
 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
 {
         lw->weight -= dec;
         lw->inv_weight = 0;
 }
 
 /*
  * To aid in avoiding the subversion of "niceness" due to uneven distribution
  * of tasks with abnormal "nice" values across CPUs the contribution that
  * each task makes to its run queue's load is weighted according to its
  * scheduling class and "nice" value. For SCHED_NORMAL tasks this is just a
  * scaled version of the new time slice allocation that they receive on time
  * slice expiry etc.
  */
 
 #define WEIGHT_IDLEPRIO         2
 #define WMULT_IDLEPRIO          (1 << 31)
 
 /*
  * Nice levels are multiplicative, with a gentle 10% change for every
  * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
  * nice 1, it will get ~10% less CPU time than another CPU-bound task
  * that remained on nice 0.
  *
  * The "10% effect" is relative and cumulative: from _any_ nice level,
  * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
  * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
  * If a task goes up by ~10% and another task goes down by ~10% then
  * the relative distance between them is ~25%.)
  */
 static const int prio_to_weight[40] = {
  /* -20 */     88761,     71755,     56483,     46273,     36291,
  /* -15 */     29154,     23254,     18705,     14949,     11916,
  /* -10 */      9548,      7620,      6100,      4904,      3906,
  /*  -5 */      3121,      2501,      1991,      1586,      1277,
  /*   0 */      1024,       820,       655,       526,       423,
  /*   5 */       335,       272,       215,       172,       137,
  /*  10 */       110,        87,        70,        56,        45,
  /*  15 */        36,        29,        23,        18,        15,
 };
 
 /*
  * Inverse (2^32/x) values of the prio_to_weight[] array, precalculated.
  *
  * In cases where the weight does not change often, we can use the
  * precalculated inverse to speed up arithmetics by turning divisions
  * into multiplications:
  */
 static const u32 prio_to_wmult[40] = {
  /* -20 */     48388,     59856,     76040,     92818,    118348,
  /* -15 */    147320,    184698,    229616,    287308,    360437,
  /* -10 */    449829,    563644,    704093,    875809,   1099582,
  /*  -5 */   1376151,   1717300,   2157191,   2708050,   3363326,
  /*   0 */   4194304,   5237765,   6557202,   8165337,  10153587,
  /*   5 */  12820798,  15790321,  19976592,  24970740,  31350126,
  /*  10 */  39045157,  49367440,  61356676,  76695844,  95443717,
  /*  15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
 };
 
 static void activate_task(struct rq *rq, struct task_struct *p, int wakeup);
 
 /*
  * runqueue iterator, to support SMP load-balancing between different
  * scheduling classes, without having to expose their internal data
  * structures to the load-balancing proper:
  */
 struct rq_iterator {
         void *arg;
         struct task_struct *(*start)(void *);
         struct task_struct *(*next)(void *);
 };
 
 #ifdef CONFIG_SMP
 static unsigned long
 balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
               unsigned long max_load_move, struct sched_domain *sd,
               enum cpu_idle_type idle, int *all_pinned,
               int *this_best_prio, struct rq_iterator *iterator);
 
 static int
 iter_move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
                    struct sched_domain *sd, enum cpu_idle_type idle,
                    struct rq_iterator *iterator);
 #endif
 
 #ifdef CONFIG_CGROUP_CPUACCT
 static void cpuacct_charge(struct task_struct *tsk, u64 cputime);
 #else
 static inline void cpuacct_charge(struct task_struct *tsk, u64 cputime) {}
 #endif
 
 #ifdef CONFIG_SMP
 static unsigned long source_load(int cpu, int type);
 static unsigned long target_load(int cpu, int type);
 static unsigned long cpu_avg_load_per_task(int cpu);
 static int task_hot(struct task_struct *p, u64 now, struct sched_domain *sd);
 #endif /* CONFIG_SMP */
 
 #include "sched_stats.h"
 #include "sched_idletask.c"
 #include "sched_fair.c"
 #include "sched_rt.c"
 #ifdef CONFIG_SCHED_DEBUG
 # include "sched_debug.c"
 #endif
 
 #define sched_class_highest (&rt_sched_class)
 #define for_each_class(class) \
    for (class = sched_class_highest; class; class = class->next)
 
 static inline void inc_load(struct rq *rq, const struct task_struct *p)
 {
         update_load_add(&rq->load, p->se.load.weight);
 }
 
 static inline void dec_load(struct rq *rq, const struct task_struct *p)
 {
         update_load_sub(&rq->load, p->se.load.weight);
 }
 
 static void inc_nr_running(struct task_struct *p, struct rq *rq)
 {
         rq->nr_running++;
         inc_load(rq, p);
 }
 
 static void dec_nr_running(struct task_struct *p, struct rq *rq)
 {
         rq->nr_running--;
         dec_load(rq, p);
 }
 
 static void set_load_weight(struct task_struct *p)
 {
         if (task_has_rt_policy(p)) {
                 p->se.load.weight = prio_to_weight[0] * 2;
                 p->se.load.inv_weight = prio_to_wmult[0] >> 1;
                 return;
         }
 
         /*
          * SCHED_IDLE tasks get minimal weight:
          */
         if (p->policy == SCHED_IDLE) {
                 p->se.load.weight = WEIGHT_IDLEPRIO;
                 p->se.load.inv_weight = WMULT_IDLEPRIO;
                 return;
         }
 
         p->se.load.weight = prio_to_weight[p->static_prio - MAX_RT_PRIO];
         p->se.load.inv_weight = prio_to_wmult[p->static_prio - MAX_RT_PRIO];
 }
 
 static void enqueue_task(struct rq *rq, struct task_struct *p, int wakeup)
 {
         sched_info_queued(p);
         p->sched_class->enqueue_task(rq, p, wakeup);
         p->se.on_rq = 1;
 }
 
 static void dequeue_task(struct rq *rq, struct task_struct *p, int sleep)
 {
         p->sched_class->dequeue_task(rq, p, sleep);
         p->se.on_rq = 0;
 }
 
 /*
  * __normal_prio - return the priority that is based on the static prio
  */
 static inline int __normal_prio(struct task_struct *p)
 {
         return p->static_prio;
 }
 
 /*
  * Calculate the expected normal priority: i.e. priority
  * without taking RT-inheritance into account. Might be
  * boosted by interactivity modifiers. Changes upon fork,
  * setprio syscalls, and whenever the interactivity
  * estimator recalculates.
  */
 static inline int normal_prio(struct task_struct *p)
 {
         int prio;
 
         if (task_has_rt_policy(p))
                 prio = MAX_RT_PRIO-1 - p->rt_priority;
         else
                 prio = __normal_prio(p);
 
 //      trace_special_pid(p->pid, PRIO(p), __PRIO(prio));
         return prio;
 }
 
 /*
  * Calculate the current priority, i.e. the priority
  * taken into account by the scheduler. This value might
  * be boosted by RT tasks, or might be boosted by
  * interactivity modifiers. Will be RT if the task got
  * RT-boosted. If not then it returns p->normal_prio.
  */
 static int effective_prio(struct task_struct *p)
 {
         p->normal_prio = normal_prio(p);
         /*
          * If we are RT tasks or we were boosted to RT priority,
          * keep the priority unchanged. Otherwise, update priority
          * to the normal priority:
          */
         if (!rt_prio(p->prio))
                 return p->normal_prio;
         return p->prio;
 }
 
 /*
  * activate_task - move a task to the runqueue.
  */
 static void activate_task(struct rq *rq, struct task_struct *p, int wakeup)
 {
         if (task_contributes_to_load(p))
                 rq->nr_uninterruptible--;
 
         ftrace_event_task_activate(p, cpu_of(rq));
         enqueue_task(rq, p, wakeup);
         inc_nr_running(p, rq);
 }
 
 /*
  * deactivate_task - remove a task from the runqueue.
  */
 static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep)
 {
         if (task_contributes_to_load(p))
                 rq->nr_uninterruptible++;
 
         ftrace_event_task_deactivate(p, cpu_of(rq));
         dequeue_task(rq, p, sleep);
         dec_nr_running(p, rq);
 }
 
 /**
  * task_curr - is this task currently executing on a CPU?
  * @p: the task in question.
  */
 inline int task_curr(const struct task_struct *p)
 {
         return cpu_curr(task_cpu(p)) == p;
 }
 
 /* Used instead of source_load when we know the type == 0 */
 unsigned long weighted_cpuload(const int cpu)
 {
         return cpu_rq(cpu)->load.weight;
 }
 
 static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)
 {
         set_task_rq(p, cpu);
 #ifdef CONFIG_SMP
         /*
          * After ->cpu is set up to a new value, task_rq_lock(p, ...) can be
          * successfuly executed on another CPU. We must ensure that updates of
          * per-task data have been completed by this moment.
          */
         smp_wmb();
         task_thread_info(p)->cpu = cpu;
 #endif
 }
 
 static inline void check_class_changed(struct rq *rq, struct task_struct *p,
                                        const struct sched_class *prev_class,
                                        int oldprio, int running)
 {
         if (prev_class != p->sched_class) {
                 if (prev_class->switched_from)
                         prev_class->switched_from(rq, p, running);
                 p->sched_class->switched_to(rq, p, running);
         } else
                 p->sched_class->prio_changed(rq, p, oldprio, running);
 }
 
 #ifdef CONFIG_SMP
 
 /*
  * Is this task likely cache-hot:
  */
 static int
 task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
 {
         s64 delta;
 
         /*
          * Buddy candidates are cache hot:
          */
         if (&p->se == cfs_rq_of(&p->se)->next)
                 return 1;
 
         if (p->sched_class != &fair_sched_class)
                 return 0;
 
         if (sysctl_sched_migration_cost == -1)
                 return 1;
         if (sysctl_sched_migration_cost == 0)
                 return 0;
 
         delta = now - p->se.exec_start;
 
         return delta < (s64)sysctl_sched_migration_cost;
 }
 
 
 void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
 {
         int old_cpu = task_cpu(p);
         struct rq *old_rq = cpu_rq(old_cpu), *new_rq = cpu_rq(new_cpu);
         struct cfs_rq *old_cfsrq = task_cfs_rq(p),
                       *new_cfsrq = cpu_cfs_rq(old_cfsrq, new_cpu);
         u64 clock_offset;
 
         clock_offset = old_rq->clock - new_rq->clock;
 
 #ifdef CONFIG_SCHEDSTATS
         if (p->se.wait_start)
                 p->se.wait_start -= clock_offset;
         if (p->se.sleep_start)
                 p->se.sleep_start -= clock_offset;
         if (p->se.block_start)
                 p->se.block_start -= clock_offset;
         if (old_cpu != new_cpu) {
                 schedstat_inc(p, se.nr_migrations);
                 if (task_hot(p, old_rq->clock, NULL))
                         schedstat_inc(p, se.nr_forced2_migrations);
         }
 #endif
         p->se.vruntime -= old_cfsrq->min_vruntime -
                                          new_cfsrq->min_vruntime;
 
         __set_task_cpu(p, new_cpu);
 }
 
 struct migration_req {
         struct list_head list;
 
         struct task_struct *task;
         int dest_cpu;
 
         struct completion done;
 };
 
 /*
  * The task's runqueue lock must be held.
  * Returns true if you have to wait for migration thread.
  */
 static int
 migrate_task(struct task_struct *p, int dest_cpu, struct migration_req *req)
 {
         struct rq *rq = task_rq(p);
 
         /*
          * If the task is not on a runqueue (and not running), then
          * it is sufficient to simply update the task's cpu field.
          */
         if (!p->se.on_rq && !task_running(rq, p)) {
                 set_task_cpu(p, dest_cpu);
                 return 0;
         }
 
         init_completion(&req->done);
         req->task = p;
         req->dest_cpu = dest_cpu;
         list_add(&req->list, &rq->migration_queue);
 
         return 1;
 }
 
 /*
  * wait_task_inactive - wait for a thread to unschedule.
  *
  * The caller must ensure that the task *will* unschedule sometime soon,
  * else this function might spin for a *long* time. This function can't
  * be called with interrupts off, or it may introduce deadlock with
  * smp_call_function() if an IPI is sent by the same process we are
  * waiting to become inactive.
  */
 void wait_task_inactive(struct task_struct *p)
 {
         unsigned long flags;
         int running, on_rq;
         struct rq *rq;
 
         for (;;) {
                 /*
                  * We do the initial early heuristics without holding
                  * any task-queue locks at all. We'll only try to get
                  * the runqueue lock when things look like they will
                  * work out!
                  */
                 rq = task_rq(p);
 
                 /*
                  * If the task is actively running on another CPU
                  * still, just relax and busy-wait without holding
                  * any locks.
                  *
                  * NOTE! Since we don't hold any locks, it's not
                  * even sure that "rq" stays as the right runqueue!
                  * But we don't care, since "task_running()" will
                  * return false if the runqueue has changed and p
                  * is actually now running somewhere else!
                  */
                 while (task_running(rq, p))
                         cpu_relax();
 
                 /*
                  * Ok, time to look more closely! We need the rq
                  * lock now, to be *sure*. If we're wrong, we'll
                  * just go back and repeat.
                  */
                 rq = task_rq_lock(p, &flags);
                 trace_kernel_sched_wait(p);
                 running = task_running(rq, p);
                 on_rq = p->se.on_rq;
                 task_rq_unlock(rq, &flags);
 
                 /*
                  * Was it really running after all now that we
                  * checked with the proper locks actually held?
                  *
                  * Oops. Go back and try again..
                  */
                 if (unlikely(running)) {
                         cpu_relax();
                         continue;
                 }
 
                 /*
                  * It's not enough that it's not actively running,
                  * it must be off the runqueue _entirely_, and not
                  * preempted!
                  *
                  * So if it wa still runnable (but just not actively
                  * running right now), it's preempted, and we should
                  * yield - it could be a while.
                  */
                 if (unlikely(on_rq)) {
                         schedule_timeout_uninterruptible(1);
                         continue;
                 }
 
                 /*
                  * Ahh, all good. It wasn't running, and it wasn't
                  * runnable, which means that it will never become
                  * running in the future either. We're all done!
                  */
                 break;
         }
 }
 
 /***
  * kick_process - kick a running thread to enter/exit the kernel
  * @p: the to-be-kicked thread
  *
  * Cause a process which is running on another CPU to enter
  * kernel-mode, without any delay. (to get signals handled.)
  *
  * NOTE: this function doesnt have to take the runqueue lock,
  * because all it wants to ensure is that the remote task enters
  * the kernel. If the IPI races and the task has been migrated
  * to another CPU then no harm is done and the purpose has been
  * achieved as well.
  */
 void kick_process(struct task_struct *p)
 {
         int cpu;
 
         preempt_disable();
         cpu = task_cpu(p);
         if ((cpu != smp_processor_id()) && task_curr(p))
                 smp_send_reschedule(cpu);
         preempt_enable();
 }
 
 /*
  * Return a low guess at the load of a migration-source cpu weighted
  * according to the scheduling class and "nice" value.
  *
  * We want to under-estimate the load of migration sources, to
  * balance conservatively.
  */
 static unsigned long source_load(int cpu, int type)
 {
         struct rq *rq = cpu_rq(cpu);
         unsigned long total = weighted_cpuload(cpu);
 
         if (type == 0)
                 return total;
 
         return min(rq->cpu_load[type-1], total);
 }
 
 /*
  * Return a high guess at the load of a migration-target cpu weighted
  * according to the scheduling class and "nice" value.
  */
 static unsigned long target_load(int cpu, int type)
 {
         struct rq *rq = cpu_rq(cpu);
         unsigned long total = weighted_cpuload(cpu);
 
         if (type == 0)
                 return total;
 
         return max(rq->cpu_load[type-1], total);
 }
 
 /*
  * Return the average load per task on the cpu's run queue
  */
 static unsigned long cpu_avg_load_per_task(int cpu)
 {
         struct rq *rq = cpu_rq(cpu);
         unsigned long total = weighted_cpuload(cpu);
         unsigned long n = rq->nr_running;
 
         return n ? total / n : SCHED_LOAD_SCALE;
 }
 
 /*
  * find_idlest_group finds and returns the least busy CPU group within the
  * domain.
  */
 static struct sched_group *
 find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
 {
         struct sched_group *idlest = NULL, *this = NULL, *group = sd->groups;
         unsigned long min_load = ULONG_MAX, this_load = 0;
         int load_idx = sd->forkexec_idx;
         int imbalance = 100 + (sd->imbalance_pct-100)/2;
 
         do {
                 unsigned long load, avg_load;
                 int local_group;
                 int i;
 
                 /* Skip over this group if it has no CPUs allowed */
                 if (!cpus_intersects(group->cpumask, p->cpus_allowed))
                         continue;
 
                 local_group = cpu_isset(this_cpu, group->cpumask);
 
                 /* Tally up the load of all CPUs in the group */
                 avg_load = 0;
 
                 for_each_cpu_mask(i, group->cpumask) {
                         /* Bias balancing toward cpus of our domain */
                         if (local_group)
                                 load = source_load(i, load_idx);
                         else
                                 load = target_load(i, load_idx);
 
                         avg_load += load;
                 }
 
                 /* Adjust by relative CPU power of the group */
                 avg_load = sg_div_cpu_power(group,
                                 avg_load * SCHED_LOAD_SCALE);
 
                 if (local_group) {
                         this_load = avg_load;
                         this = group;
                 } else if (avg_load < min_load) {
                         min_load = avg_load;
                         idlest = group;
                 }
         } while (group = group->next, group != sd->groups);
 
         if (!idlest || 100*this_load < imbalance*min_load)
                 return NULL;
         return idlest;
 }
 
 /*
  * find_idlest_cpu - find the idlest cpu among the cpus in group.
  */
 static int
 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
 {
         cpumask_t tmp;
         unsigned long load, min_load = ULONG_MAX;
         int idlest = -1;
         int i;
 
         /* Traverse only the allowed CPUs */
         cpus_and(tmp, group->cpumask, p->cpus_allowed);
 
         for_each_cpu_mask(i, tmp) {
                 load = weighted_cpuload(i);
 
                 if (load < min_load || (load == min_load && i == this_cpu)) {
                         min_load = load;
                         idlest = i;
                 }
         }
 
         return idlest;
 }
 
 /*
  * sched_balance_self: balance the current task (running on cpu) in domains
  * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
  * SD_BALANCE_EXEC.
  *
  * Balance, ie. select the least loaded group.
  *
  * Returns the target CPU number, or the same CPU if no balancing is needed.
  *
  * preempt must be disabled.
  */
 static int sched_balance_self(int cpu, int flag)
 {
         struct task_struct *t = current;
         struct sched_domain *tmp, *sd = NULL;
 
         for_each_domain(cpu, tmp) {
                 /*
                  * If power savings logic is enabled for a domain, stop there.
                  */
                 if (tmp->flags & SD_POWERSAVINGS_BALANCE)
                         break;
                 if (tmp->flags & flag)
                         sd = tmp;
         }
 
         while (sd) {
                 cpumask_t span;
                 struct sched_group *group;
                 int new_cpu, weight;
 
                 if (!(sd->flags & flag)) {
                         sd = sd->child;
                         continue;
                 }
 
                 span = sd->span;
                 group = find_idlest_group(sd, t, cpu);
                 if (!group) {
                         sd = sd->child;
                         continue;
                 }
 
                 new_cpu = find_idlest_cpu(group, t, cpu);
                 if (new_cpu == -1 || new_cpu == cpu) {
                         /* Now try balancing at a lower domain level of cpu */
                         sd = sd->child;
                         continue;
                 }
 
                 /* Now try balancing at a lower domain level of new_cpu */
                 cpu = new_cpu;
                 sd = NULL;
                 weight = cpus_weight(span);
                 for_each_domain(cpu, tmp) {
                         if (weight <= cpus_weight(tmp->span))
                                 break;
                         if (tmp->flags & flag)
                                 sd = tmp;
                 }
                 /* while loop will break here if sd == NULL */
         }
 
         return cpu;
 }
 
 #endif /* CONFIG_SMP */
 
 /***
  * try_to_wake_up - wake up a thread
  * @p: the to-be-woken-up thread
  * @state: the mask of task states that can be woken
  * @sync: do a synchronous wakeup?
  *
  * Put it on the run-queue if it's not already there. The "current"
  * thread is always on the run-queue (except when the actual
  * re-schedule is in progress), and as such you're allowed to do
  * the simpler "current->state = TASK_RUNNING" to mark yourself
  * runnable without the overhead of this.
  *
  * returns failure only if the task is already active.
  */
 static int
 try_to_wake_up(struct task_struct *p, unsigned int state, int sync, int mutex)
 {
         int cpu, orig_cpu, this_cpu, success = 0;
         unsigned long flags;
         long old_state;
         struct rq *rq;
 
 #ifdef CONFIG_PREEMPT_RT
         /*
          * sync wakeups can increase wakeup latencies:
          */
         if (rt_task(p))
                 sync = 0;
 #endif
         smp_wmb();
         rq = task_rq_lock(p, &flags);
         old_state = p->state;
         if (!(old_state & state))
                 goto out;
 
         if (p->se.on_rq)
                 goto out_running;
 
         cpu = task_cpu(p);
         orig_cpu = cpu;
         this_cpu = smp_processor_id();
 
 #ifdef CONFIG_SMP
         if (unlikely(task_running(rq, p)))
                 goto out_activate;
 
         cpu = p->sched_class->select_task_rq(p, sync);
         if (cpu != orig_cpu) {
                 set_task_cpu(p, cpu);
                 task_rq_unlock(rq, &flags);
                 /* might preempt at this point */
                 rq = task_rq_lock(p, &flags);
                 old_state = p->state;
                 if (!(old_state & state))
                         goto out;
                 if (p->se.on_rq)
                         goto out_running;
 
                 this_cpu = smp_processor_id();
                 cpu = task_cpu(p);
         }
 
 #ifdef CONFIG_SCHEDSTATS
         schedstat_inc(rq, ttwu_count);
         if (cpu == this_cpu)
                 schedstat_inc(rq, ttwu_local);
         else {
                 struct sched_domain *sd;
                 for_each_domain(this_cpu, sd) {
                         if (cpu_isset(cpu, sd->span)) {
                                 schedstat_inc(sd, ttwu_wake_remote);
                                 break;
                         }
                 }
         }
 #endif
 
 out_activate:
 #endif /* CONFIG_SMP */
         schedstat_inc(p, se.nr_wakeups);
         if (sync)
                 schedstat_inc(p, se.nr_wakeups_sync);
         if (orig_cpu != cpu)
                 schedstat_inc(p, se.nr_wakeups_migrate);
         if (cpu == this_cpu)
                 schedstat_inc(p, se.nr_wakeups_local);
         else
                 schedstat_inc(p, se.nr_wakeups_remote);
         update_rq_clock(rq);
         activate_task(rq, p, 1);
         success = 1;
 
 out_running:
         trace_kernel_sched_wakeup(rq, p);
         check_preempt_curr(rq, p);
 
         if (mutex)
                 p->state = TASK_RUNNING_MUTEX;
         else
                 p->state = TASK_RUNNING;
 #ifdef CONFIG_SMP
         if (p->sched_class->task_wake_up)
                 p->sched_class->task_wake_up(rq, p);
 #endif
 out:
         task_rq_unlock(rq, &flags);
 
         return success;
 }
 
 int wake_up_process(struct task_struct *p)
 {
         return try_to_wake_up(p, TASK_ALL, 0, 0);
 }
 EXPORT_SYMBOL(wake_up_process);
 
 int  wake_up_process_sync(struct task_struct * p)
 {
         return try_to_wake_up(p, TASK_ALL, 1, 0);
 }
 EXPORT_SYMBOL(wake_up_process_sync);
 
 int  wake_up_process_mutex(struct task_struct * p)
 {
         return try_to_wake_up(p, TASK_ALL, 0, 1);
 }
 EXPORT_SYMBOL(wake_up_process_mutex);
 
 int  wake_up_process_mutex_sync(struct task_struct * p)
 {
         return try_to_wake_up(p, TASK_ALL, 1, 1);
 }
 EXPORT_SYMBOL(wake_up_process_mutex_sync);
 
 int wake_up_state(struct task_struct *p, unsigned int state)
 {
         return try_to_wake_up(p, state | TASK_RUNNING_MUTEX, 0, 0);
 }
 
 /*
  * Perform scheduler related setup for a newly forked process p.
  * p is forked by current.
  *
  * __sched_fork() is basic setup used by init_idle() too:
  */
 static void __sched_fork(struct task_struct *p)
 {
         p->se.exec_start                = 0;
         p->se.sum_exec_runtime          = 0;
         p->se.prev_sum_exec_runtime     = 0;
         p->se.last_wakeup               = 0;
         p->se.avg_overlap               = 0;
 
 #ifdef CONFIG_SCHEDSTATS
         p->se.wait_start                = 0;
         p->se.sum_sleep_runtime         = 0;
         p->se.sleep_start               = 0;
         p->se.block_start               = 0;
         p->se.sleep_max                 = 0;
         p->se.block_max                 = 0;
         p->se.exec_max                  = 0;
         p->se.slice_max                 = 0;
         p->se.wait_max                  = 0;
 #endif
 
         INIT_LIST_HEAD(&p->rt.run_list);
         p->se.on_rq = 0;
 
 #ifdef CONFIG_PREEMPT_NOTIFIERS
         INIT_HLIST_HEAD(&p->preempt_notifiers);
 #endif
 
         /*
          * We mark the process as running here, but have not actually
          * inserted it onto the runqueue yet. This guarantees that
          * nobody will actually run it, and a signal or other external
          * event cannot wake it up and insert it on the runqueue either.
          */
         p->state = TASK_RUNNING;
 }
 
 /*
  * fork()/clone()-time setup:
  */
 void sched_fork(struct task_struct *p, int clone_flags)
 {
         int cpu = get_cpu();
 
         __sched_fork(p);
 
 #ifdef CONFIG_SMP
         cpu = sched_balance_self(cpu, SD_BALANCE_FORK);
 #endif
         set_task_cpu(p, cpu);
 
         /*
          * Make sure we do not leak PI boosting priority to the child:
          */
         p->prio = current->normal_prio;
         if (!rt_prio(p->prio))
                 p->sched_class = &fair_sched_class;
 
 #if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
         if (likely(sched_info_on()))
                 memset(&p->sched_info, 0, sizeof(p->sched_info));
 #endif
 #if defined(CONFIG_SMP)
         p->oncpu = 0;
 #endif
 #ifdef CONFIG_PREEMPT
         /* Want to start with kernel preemption disabled. */
         task_thread_info(p)->preempt_count = 1;
 #endif
         put_cpu();
 }
 
 /*
  * wake_up_new_task - wake up a newly created task for the first time.
  *
  * This function will do some initial scheduler statistics housekeeping
  * that must be done for every newly created context, then puts the task
  * on the runqueue and wakes it.
  */
 void wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
 {
         unsigned long flags;
         struct rq *rq;
 
         rq = task_rq_lock(p, &flags);
         BUG_ON(p->state != TASK_RUNNING);
         update_rq_clock(rq);
 
         p->prio = effective_prio(p);
 
         if (!p->sched_class->task_new || !current->se.on_rq) {
                 activate_task(rq, p, 0);
         } else {
                 /*
                  * Let the scheduling class do new task startup
                  * management (if any):
                  */
                 p->sched_class->task_new(rq, p);
                 inc_nr_running(p, rq);
         }
         trace_kernel_sched_wakeup_new(rq, p);
         check_preempt_curr(rq, p);
 #ifdef CONFIG_SMP
         if (p->sched_class->task_wake_up)
                 p->sched_class->task_wake_up(rq, p);
 #endif
         task_rq_unlock(rq, &flags);
 }
 
 #ifdef CONFIG_PREEMPT_NOTIFIERS
 
 /**
  * preempt_notifier_register - tell me when current is being being preempted & rescheduled
  * @notifier: notifier struct to register
  */
 void preempt_notifier_register(struct preempt_notifier *notifier)
 {
         hlist_add_head(&notifier->link, &current->preempt_notifiers);
 }
 EXPORT_SYMBOL_GPL(preempt_notifier_register);
 
 /**
  * preempt_notifier_unregister - no longer interested in preemption notifications
  * @notifier: notifier struct to unregister
  *
  * This is safe to call from within a preemption notifier.
  */
 void preempt_notifier_unregister(struct preempt_notifier *notifier)
 {
         hlist_del(&notifier->link);
 }
 EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
 
 static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
 {
         struct preempt_notifier *notifier;
         struct hlist_node *node;
 
         if (hlist_empty(&curr->preempt_notifiers))
                 return;
 
         /*
          * The KVM sched in notifier expects to be called with
          * interrupts enabled.
          */
         local_irq_enable();
         hlist_for_each_entry(notifier, node, &curr->preempt_notifiers, link)
                 notifier->ops->sched_in(notifier, raw_smp_processor_id());
         local_irq_disable();
 }
 
 static void
 fire_sched_out_preempt_notifiers(struct task_struct *curr,
                                  struct task_struct *next)
 {
         struct preempt_notifier *notifier;
         struct hlist_node *node;
 
         hlist_for_each_entry(notifier, node, &curr->preempt_notifiers, link)
                 notifier->ops->sched_out(notifier, next);
 }
 
 #else
 
 static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
 {
 }
 
 static void
 fire_sched_out_preempt_notifiers(struct task_struct *curr,
                                  struct task_struct *next)
 {
 }
 
 #endif
 
 #ifdef CONFIG_DEBUG_PREEMPT
 void notrace preempt_enable_no_resched(void)
 {
         static int once = 1;
 
         barrier();
         dec_preempt_count();
 
         if (once && !preempt_count()) {
                 once = 0;
                 printk(KERN_ERR "BUG: %s:%d task might have lost a preemption check!\n",
                         current->comm, current->pid);
                 dump_stack();
         }
 }
 
 EXPORT_SYMBOL(preempt_enable_no_resched);
 #endif
 
 
 /**
  * prepare_task_switch - prepare to switch tasks
  * @rq: the runqueue preparing to switch
  * @prev: the current task that is being switched out
  * @next: the task we are going to switch to.
  *
  * This is called with the rq lock held and interrupts off. It must
  * be paired with a subsequent finish_task_switch after the context
  * switch.
  *
  * prepare_task_switch sets up locking and calls architecture specific
  * hooks.
  */
 static inline void
 prepare_task_switch(struct rq *rq, struct task_struct *prev,
                     struct task_struct *next)
 {
         fire_sched_out_preempt_notifiers(prev, next);
         prepare_lock_switch(rq, next);
         prepare_arch_switch(next);
 }
 
 /**
  * finish_task_switch - clean up after a task-switch
  * @rq: runqueue associated with task-switch
  * @prev: the thread we just switched away from.
  *
  * finish_task_switch must be called after the context switch, paired
  * with a prepare_task_switch call before the context switch.
  * finish_task_switch will reconcile locking set up by prepare_task_switch,
  * and do any other architecture-specific cleanup actions.
  *
  * Note that we may have delayed dropping an mm in context_switch(). If
  * so, we finish that here outside of the runqueue lock. (Doing it
  * with the lock held can cause deadlocks; see schedule() for
  * details.)
  */
 static void finish_task_switch(struct rq *rq, struct task_struct *prev)
         __releases(rq->lock)
 {
         struct mm_struct *mm = rq->prev_mm;
         long prev_state;
 
         rq->prev_mm = NULL;
 
         /*
          * A task struct has one reference for the use as "current".
          * If a task dies, then it sets TASK_DEAD in tsk->state and calls
          * schedule one last time. The schedule call will never return, and
          * the scheduled task must drop that reference.
          * The test for TASK_DEAD must occur while the runqueue locks are
          * still held, otherwise prev could be scheduled on another cpu, die
          * there before we look at prev->state, and then the reference would
          * be dropped twice.
          *              Manfred Spraul <manfred@colorfullife.com>
          */
         prev_state = prev->state;
         _finish_arch_switch(prev);
         finish_lock_switch(rq, prev);
 #ifdef CONFIG_SMP
         if (current->sched_class->post_schedule)
                 current->sched_class->post_schedule(rq);
 #endif
 
         fire_sched_in_preempt_notifiers(current);
         /*
          * Delay the final freeing of the mm or task, so that we dont have
          * to do complex work from within the scheduler:
          */
         if (mm)
                 mmdrop_delayed(mm);
         if (unlikely(prev_state == TASK_DEAD)) {
                 /*
                  * Remove function-return probe instances associated with this
                  * task and put them back on the free list.
                  */
                 kprobe_flush_task(prev);
                 put_task_struct(prev);
         }
 }
 
 /**
  * schedule_tail - first thing a freshly forked thread must call.
  * @prev: the thread we just switched away from.
  */
 asmlinkage void schedule_tail(struct task_struct *prev)
         __releases(rq->lock)
 {
         preempt_disable(); // TODO: move this to fork setup
         finish_task_switch(this_rq(), prev);
         __preempt_enable_no_resched();
         local_irq_enable();
 #ifdef __ARCH_WANT_UNLOCKED_CTXSW
         /* In this case, finish_task_switch does not reenable preemption */
         preempt_enable();
 #else
         preempt_check_resched();
 #endif
         if (current->set_child_tid)
                 put_user(task_pid_vnr(current), current->set_child_tid);
 }
 
 /*
  * context_switch - switch to the new MM and the new
  * thread's register state.
  */
 static inline void
 context_switch(struct rq *rq, struct task_struct *prev,
                struct task_struct *next)
 {
         struct mm_struct *mm, *oldmm;
 
         prepare_task_switch(rq, prev, next);
 
         trace_kernel_sched_switch(rq, prev, next);
         mm = next->mm;
         oldmm = prev->active_mm;
         /*
          * For paravirt, this is coupled with an exit in switch_to to
          * combine the page table reload and the switch backend into
          * one hypercall.
          */
         arch_enter_lazy_cpu_mode();
 
         if (unlikely(!mm)) {
                 next->active_mm = oldmm;
                 atomic_inc(&oldmm->mm_count);
                 enter_lazy_tlb(oldmm, next);
         } else
                 switch_mm(oldmm, mm, next);
 
         if (unlikely(!prev->mm)) {
                 prev->active_mm = NULL;
                 rq->prev_mm = oldmm;
         }
         /*
          * Since the runqueue lock will be released by the next
          * task (which is an invalid locking op but in the case
          * of the scheduler it's an obvious special-case), so we
          * do an early lockdep release here:
          */
 #ifndef __ARCH_WANT_UNLOCKED_CTXSW
         spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
 #endif
 
 #ifdef CURRENT_PTR
         barrier();
         *current_ptr = next;
         *current_ti_ptr = next->thread_info;
 #endif
         /* Here we just switch the register state and the stack. */
         switch_to(prev, next, prev);
 
         barrier();
         /*
          * this_rq must be evaluated again because prev may have moved
          * CPUs since it called schedule(), thus the 'rq' on its stack
          * frame will be invalid.
          */
         finish_task_switch(this_rq(), prev);
 }
 
 /*
  * nr_running, nr_uninterruptible and nr_context_switches:
  *
  * externally visible scheduler statistics: current number of runnable
  * threads, current number of uninterruptible-sleeping threads, total
  * number of context switches performed since bootup.
  */
 unsigned long nr_running(void)
 {
         unsigned long i, sum = 0;
 
         for_each_online_cpu(i)
                 sum += cpu_rq(i)->nr_running;
 
         return sum;
 }
 
 unsigned long nr_uninterruptible(void)
 {
         unsigned long i, sum = 0;
 
         for_each_possible_cpu(i)
                 sum += cpu_rq(i)->nr_uninterruptible;
 
         /*
          * Since we read the counters lockless, it might be slightly
          * inaccurate. Do not allow it to go below zero though:
          */
         if (unlikely((long)sum < 0))
                 sum = 0;
 
         return sum;
 }
 
 unsigned long nr_uninterruptible_cpu(int cpu)
 {
         return cpu_rq(cpu)->nr_uninterruptible;
 }
 
 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);
 
         /*
          * 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 nr_active(void)
 {
         unsigned long i, running = 0, uninterruptible = 0;
 
         for_each_online_cpu(i) {
                 running += cpu_rq(i)->nr_running;
                 uninterruptible += cpu_rq(i)->nr_uninterruptible;
         }
 
         if (unlikely((long)uninterruptible < 0))
                 uninterruptible = 0;
 
         return running + uninterruptible;
 }
 
 /*
  * Update rq->cpu_load[] statistics. This function is usually called every
  * scheduler tick (TICK_NSEC).
  */
 static void update_cpu_load(struct rq *this_rq)
 {
         unsigned long this_load = this_rq->load.weight;
         int i, scale;
 
         this_rq->nr_load_updates++;
 
         /* Update our load: */
         for (i = 0, scale = 1; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
                 unsigned long old_load, new_load;
 
                 /* scale is effectively 1 << i now, and >> i divides by scale */
 
                 old_load = this_rq->cpu_load[i];
                 new_load = this_load;
                 /*
                  * Round up the averaging division if load is increasing. This
                  * prevents us from getting stuck on 9 if the load is 10, for
                  * example.
                  */
                 if (new_load > old_load)
                         new_load += scale-1;
                 this_rq->cpu_load[i] = (old_load*(scale-1) + new_load) >> i;
         }
 }
 
 #ifdef CONFIG_SMP
 
 /*
  * double_rq_lock - safely lock two runqueues
  *
  * Note this does not disable interrupts like task_rq_lock,
  * you need to do so manually before calling.
  */
 static void double_rq_lock(struct rq *rq1, struct rq *rq2)
         __acquires(rq1->lock)
         __acquires(rq2->lock)
 {
         BUG_ON(!irqs_disabled());
         if (rq1 == rq2) {
                 spin_lock(&rq1->lock);
                 __acquire(rq2->lock);   /* Fake it out ;) */
         } else {
                 if (rq1 < rq2) {
                         spin_lock(&rq1->lock);
                         spin_lock(&rq2->lock);
                 } else {
                         spin_lock(&rq2->lock);
                         spin_lock(&rq1->lock);
                 }
         }
         update_rq_clock(rq1);
         update_rq_clock(rq2);
 }
 
 /*
  * double_rq_unlock - safely unlock two runqueues
  *
  * Note this does not restore interrupts like task_rq_unlock,
  * you need to do so manually after calling.
  */
 static void double_rq_unlock(struct rq *rq1, struct rq *rq2)
         __releases(rq1->lock)
         __releases(rq2->lock)
 {
         spin_unlock(&rq1->lock);
         if (rq1 != rq2)
                 spin_unlock(&rq2->lock);
         else
                 __release(rq2->lock);
 }
 
 /*
  * double_lock_balance - lock the busiest runqueue, this_rq is locked already.
  */
 static int double_lock_balance(struct rq *this_rq, struct rq *busiest)
         __releases(this_rq->lock)
         __acquires(busiest->lock)
         __acquires(this_rq->lock)
 {
         int ret = 0;
 
         if (unlikely(!irqs_disabled())) {
                 /* printk() doesn't work good under rq->lock */
                 spin_unlock(&this_rq->lock);
                 BUG_ON(1);
         }
         if (unlikely(!spin_trylock(&busiest->lock))) {
                 if (busiest < this_rq) {
                         spin_unlock(&this_rq->lock);
                         spin_lock(&busiest->lock);
                         spin_lock(&this_rq->lock);
                         ret = 1;
                 } else
                         spin_lock(&busiest->lock);
         }
         return ret;
 }
 
 /*
  * If dest_cpu is allowed for this process, migrate the task to it.
  * This is accomplished by forcing the cpu_allowed mask to only
  * allow dest_cpu, which will force the cpu onto dest_cpu. Then
  * the cpu_allowed mask is restored.
  */
 static void sched_migrate_task(struct task_struct *p, int dest_cpu)
 {
         struct migration_req req;
         unsigned long flags;
         struct rq *rq;
 
         rq = task_rq_lock(p, &flags);
         if (!cpu_isset(dest_cpu, p->cpus_allowed)
             || unlikely(cpu_is_offline(dest_cpu)))
                 goto out;
 
         trace_kernel_sched_migrate_task(p, cpu_of(rq), dest_cpu);
         /* force the process onto the specified CPU */
         if (migrate_task(p, dest_cpu, &req)) {
                 /* Need to wait for migration thread (might exit: take ref). */
                 struct task_struct *mt = rq->migration_thread;
 
                 get_task_struct(mt);
                 task_rq_unlock(rq, &flags);
                 wake_up_process(mt);
                 put_task_struct(mt);
                 wait_for_completion(&req.done);
 
                 return;
         }
 out:
         task_rq_unlock(rq, &flags);
 }
 
 /*
  * sched_exec - execve() is a valuable balancing opportunity, because at
  * this point the task has the smallest effective memory and cache footprint.
  */
 void sched_exec(void)
 {
         int new_cpu, this_cpu = get_cpu();
         new_cpu = sched_balance_self(this_cpu, SD_BALANCE_EXEC);
         put_cpu();
         if (new_cpu != this_cpu)
                 sched_migrate_task(current, new_cpu);
 }
 
 /*
  * pull_task - move a task from a remote runqueue to the local runqueue.
  * Both runqueues must be locked.
  */
 static void pull_task(struct rq *src_rq, struct task_struct *p,
                       struct rq *this_rq, int this_cpu)
 {
         deactivate_task(src_rq, p, 0);
         set_task_cpu(p, this_cpu);
         activate_task(this_rq, p, 0);
         /*
          * Note that idle threads have a prio of MAX_PRIO, for this test
          * to be always true for them.
          */
         check_preempt_curr(this_rq, p);
 }
 
 /*
  * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
  */
 static
 int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
                      struct sched_domain *sd, enum cpu_idle_type idle,
                      int *all_pinned)
 {
         /*
          * We do not migrate tasks that are:
          * 1) running (obviously), or
          * 2) cannot be migrated to this CPU due to cpus_allowed, or
          * 3) are cache-hot on their current CPU.
          */
         if (!cpu_isset(this_cpu, p->cpus_allowed)) {
                 schedstat_inc(p, se.nr_failed_migrations_affine);
                 return 0;
         }
         *all_pinned = 0;
 
         if (task_running(rq, p)) {
                 schedstat_inc(p, se.nr_failed_migrations_running);
                 return 0;
         }
 
         /*
          * Aggressive migration if:
          * 1) task is cache cold, or
          * 2) too many balance attempts have failed.
          */
 
         if (!task_hot(p, rq->clock, sd) ||
                         sd->nr_balance_failed > sd->cache_nice_tries) {
 #ifdef CONFIG_SCHEDSTATS
                 if (task_hot(p, rq->clock, sd)) {
                         schedstat_inc(sd, lb_hot_gained[idle]);
                         schedstat_inc(p, se.nr_forced_migrations);
                 }
 #endif
                 return 1;
         }
 
         if (task_hot(p, rq->clock, sd)) {
                 schedstat_inc(p, se.nr_failed_migrations_hot);
                 return 0;
         }
         return 1;
 }
 
 static unsigned long
 balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
               unsigned long max_load_move, struct sched_domain *sd,
               enum cpu_idle_type idle, int *all_pinned,
               int *this_best_prio, struct rq_iterator *iterator)
 {
         int loops = 0, pulled = 0, pinned = 0, skip_for_load;
         struct task_struct *p;
         long rem_load_move = max_load_move;
 
         if (max_load_move == 0)
                 goto out;
 
         pinned = 1;
 
         /*
          * Start the load-balancing iterator:
          */
         p = iterator->start(iterator->arg);
 next:
         if (!p || loops++ > sysctl_sched_nr_migrate)
                 goto out;
         /*
          * To help distribute high priority tasks across CPUs we don't
          * skip a task if it will be the highest priority task (i.e. smallest
          * prio value) on its new queue regardless of its load weight
          */
         skip_for_load = (p->se.load.weight >> 1) > rem_load_move +
                                                          SCHED_LOAD_SCALE_FUZZ;
         if ((skip_for_load && p->prio >= *this_best_prio) ||
             !can_migrate_task(p, busiest, this_cpu, sd, idle, &pinned)) {
                 p = iterator->next(iterator->arg);
                 goto next;
         }
 
         pull_task(busiest, p, this_rq, this_cpu);
         pulled++;
         rem_load_move -= p->se.load.weight;
 
         /*
          * We only want to steal up to the prescribed amount of weighted load.
          */
         if (rem_load_move > 0) {
                 if (p->prio < *this_best_prio)
                         *this_best_prio = p->prio;
                 p = iterator->next(iterator->arg);
                 goto next;
         }
 out:
         /*
          * Right now, this is one of only two places pull_task() is called,
          * so we can safely collect pull_task() stats here rather than
          * inside pull_task().
          */
         schedstat_add(sd, lb_gained[idle], pulled);
 
         if (all_pinned)
                 *all_pinned = pinned;
 
         return max_load_move - rem_load_move;
 }
 
 /*
  * move_tasks tries to move up to max_load_move weighted load from busiest to
  * this_rq, as part of a balancing operation within domain "sd".
  * Returns 1 if successful and 0 otherwise.
  *
  * Called with both runqueues locked.
  */
 static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
                       unsigned long max_load_move,
                       struct sched_domain *sd, enum cpu_idle_type idle,
                       int *all_pinned)
 {
         const struct sched_class *class = sched_class_highest;
         unsigned long total_load_moved = 0;
         int this_best_prio = this_rq->curr->prio;
 
         do {
                 total_load_moved +=
                         class->load_balance(this_rq, this_cpu, busiest,
                                 max_load_move - total_load_moved,
                                 sd, idle, all_pinned, &this_best_prio);
                 class = class->next;
         } while (class && max_load_move > total_load_moved);
 
         return total_load_moved > 0;
 }
 
 static int
 iter_move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
                    struct sched_domain *sd, enum cpu_idle_type idle,
                    struct rq_iterator *iterator)
 {
         struct task_struct *p = iterator->start(iterator->arg);
         int pinned = 0;
 
         while (p) {
                 if (can_migrate_task(p, busiest, this_cpu, sd, idle, &pinned)) {
                         pull_task(busiest, p, this_rq, this_cpu);
                         /*
                          * Right now, this is only the second place pull_task()
                          * is called, so we can safely collect pull_task()
                          * stats here rather than inside pull_task().
                          */
                         schedstat_inc(sd, lb_gained[idle]);
 
                         return 1;
                 }
                 p = iterator->next(iterator->arg);
         }
 
         return 0;
 }
 
 /*
  * move_one_task tries to move exactly one task from busiest to this_rq, as
  * part of active balancing operations within "domain".
  * Returns 1 if successful and 0 otherwise.
  *
  * Called with both runqueues locked.
  */
 static int move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
                          struct sched_domain *sd, enum cpu_idle_type idle)
 {
         const struct sched_class *class;
 
         for (class = sched_class_highest; class; class = class->next)
                 if (class->move_one_task(this_rq, this_cpu, busiest, sd, idle))
                         return 1;
 
         return 0;
 }
 
 /*
  * find_busiest_group finds and returns the busiest CPU group within the
  * domain. It calculates and returns the amount of weighted load which
  * should be moved to restore balance via the imbalance parameter.
  */
 static struct sched_group *
 find_busiest_group(struct sched_domain *sd, int this_cpu,
                    unsigned long *imbalance, enum cpu_idle_type idle,
                    int *sd_idle, cpumask_t *cpus, int *balance)
 {
         struct sched_group *busiest = NULL, *this = NULL, *group = sd->groups;
         unsigned long max_load, avg_load, total_load, this_load, total_pwr;
         unsigned long max_pull;
         unsigned long busiest_load_per_task, busiest_nr_running;
         unsigned long this_load_per_task, this_nr_running;
         int load_idx, group_imb = 0;
 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
         int power_savings_balance = 1;
         unsigned long leader_nr_running = 0, min_load_per_task = 0;
         unsigned long min_nr_running = ULONG_MAX;
         struct sched_group *group_min = NULL, *group_leader = NULL;
 #endif
 
         max_load = this_load = total_load = total_pwr = 0;
         busiest_load_per_task = busiest_nr_running = 0;
         this_load_per_task = this_nr_running = 0;
         if (idle == CPU_NOT_IDLE)
                 load_idx = sd->busy_idx;
         else if (idle == CPU_NEWLY_IDLE)
                 load_idx = sd->newidle_idx;
         else
                 load_idx = sd->idle_idx;
 
         do {
                 unsigned long load, group_capacity, max_cpu_load, min_cpu_load;
                 int local_group;
                 int i;
                 int __group_imb = 0;
                 unsigned int balance_cpu = -1, first_idle_cpu = 0;
                 unsigned long sum_nr_running, sum_weighted_load;
 
                 local_group = cpu_isset(this_cpu, group->cpumask);
 
                 if (local_group)
                         balance_cpu = first_cpu(group->cpumask);
 
                 /* Tally up the load of all CPUs in the group */
                 sum_weighted_load = sum_nr_running = avg_load = 0;
                 max_cpu_load = 0;
                 min_cpu_load = ~0UL;
 
                 for_each_cpu_mask(i, group->cpumask) {
                         struct rq *rq;
 
                         if (!cpu_isset(i, *cpus))
                                 continue;
 
                         rq = cpu_rq(i);
 
                         if (*sd_idle && rq->nr_running)
                                 *sd_idle = 0;
 
                         /* Bias balancing toward cpus of our domain */
                         if (local_group) {
                                 if (idle_cpu(i) && !first_idle_cpu) {
                                         first_idle_cpu = 1;
                                         balance_cpu = i;
                                 }
 
                                 load = target_load(i, load_idx);
                         } else {
                                 load = source_load(i, load_idx);
                                 if (load > max_cpu_load)
                                         max_cpu_load = load;
                                 if (min_cpu_load > load)
                                         min_cpu_load = load;
                         }
 
                         avg_load += load;
                         sum_nr_running += rq->nr_running;
                         sum_weighted_load += weighted_cpuload(i);
                 }
 
                 /*
                  * First idle cpu or the first cpu(busiest) in this sched group
                  * is eligible for doing load balancing at this and above
                  * domains. In the newly idle case, we will allow all the cpu's
                  * to do the newly idle load balance.
                  */
                 if (idle != CPU_NEWLY_IDLE && local_group &&
                     balance_cpu != this_cpu && balance) {
                         *balance = 0;
                         goto ret;
                 }
 
                 total_load += avg_load;
                 total_pwr += group->__cpu_power;
 
                 /* Adjust by relative CPU power of the group */
                 avg_load = sg_div_cpu_power(group,
                                 avg_load * SCHED_LOAD_SCALE);
 
                 if ((max_cpu_load - min_cpu_load) > SCHED_LOAD_SCALE)
                         __group_imb = 1;
 
                 group_capacity = group->__cpu_power / SCHED_LOAD_SCALE;
 
                 if (local_group) {
                         this_load = avg_load;
                         this = group;
                         this_nr_running = sum_nr_running;
                         this_load_per_task = sum_weighted_load;
                 } else if (avg_load > max_load &&
                            (sum_nr_running > group_capacity || __group_imb)) {
                         max_load = avg_load;
                         busiest = group;
                         busiest_nr_running = sum_nr_running;
                         busiest_load_per_task = sum_weighted_load;
                         group_imb = __group_imb;
                 }
 
 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
                 /*
                  * Busy processors will not participate in power savings
                  * balance.
                  */
                 if (idle == CPU_NOT_IDLE ||
                                 !(sd->flags & SD_POWERSAVINGS_BALANCE))
                         goto group_next;
 
                 /*
                  * If the local group is idle or completely loaded
                  * no need to do power savings balance at this domain
                  */
                 if (local_group && (this_nr_running >= group_capacity ||
                                     !this_nr_running))
                         power_savings_balance = 0;
 
                 /*
                  * If a group is already running at full capacity or idle,
                  * don't include that group in power savings calculations
                  */
                 if (!power_savings_balance || sum_nr_running >= group_capacity
                     || !sum_nr_running)
                         goto group_next;
 
                 /*
                  * Calculate the group which has the least non-idle load.
                  * This is the group from where we need to pick up the load
                  * for saving power
                  */
                 if ((sum_nr_running < min_nr_running) ||
                     (sum_nr_running == min_nr_running &&
                      first_cpu(group->cpumask) <
                      first_cpu(group_min->cpumask))) {
                         group_min = group;
                         min_nr_running = sum_nr_running;
                         min_load_per_task = sum_weighted_load /
                                                 sum_nr_running;
                 }
 
                 /*
                  * Calculate the group which is almost near its
                  * capacity but still has some space to pick up some load
                  * from other group and save more power
                  */
                 if (sum_nr_running <= group_capacity - 1) {
                         if (sum_nr_running > leader_nr_running ||
                             (sum_nr_running == leader_nr_running &&
                              first_cpu(group->cpumask) >
                               first_cpu(group_leader->cpumask))) {
                                 group_leader = group;
                                 leader_nr_running = sum_nr_running;
                         }
                 }
 group_next:
 #endif
                 group = group->next;
         } while (group != sd->groups);
 
         if (!busiest || this_load >= max_load || busiest_nr_running == 0)
                 goto out_balanced;
 
         avg_load = (SCHED_LOAD_SCALE * total_load) / total_pwr;
 
         if (this_load >= avg_load ||
                         100*max_load <= sd->imbalance_pct*this_load)
                 goto out_balanced;
 
         busiest_load_per_task /= busiest_nr_running;
         if (group_imb)
                 busiest_load_per_task = min(busiest_load_per_task, avg_load);
 
         /*
          * We're trying to get all the cpus to the average_load, so we don't
          * want to push ourselves above the average load, nor do we wish to
          * reduce the max loaded cpu below the average load, as either of these
          * actions would just result in more rebalancing later, and ping-pong
          * tasks around. Thus we look for the minimum possible imbalance.
          * Negative imbalances (*we* are more loaded than anyone else) will
          * be counted as no imbalance for these purposes -- we can't fix that
          * by pulling tasks to us. Be careful of negative numbers as they'll
          * appear as very large values with unsigned longs.
          */
         if (max_load <= busiest_load_per_task)
                 goto out_balanced;
 
         /*
          * In the presence of smp nice balancing, certain scenarios can have
          * max load less than avg load(as we skip the groups at or below
          * its cpu_power, while calculating max_load..)
          */
         if (max_load < avg_load) {
                 *imbalance = 0;
                 goto small_imbalance;
         }
 
         /* Don't want to pull so many tasks that a group would go idle */
         max_pull = min(max_load - avg_load, max_load - busiest_load_per_task);
 
         /* How much load to actually move to equalise the imbalance */
         *imbalance = min(max_pull * busiest->__cpu_power,
                                 (avg_load - this_load) * this->__cpu_power)
                         / SCHED_LOAD_SCALE;
 
         /*
          * if *imbalance is less than the average load per runnable task
          * there is no gaurantee that any tasks will be moved so we'll have
          * a think about bumping its value to force at least one task to be
          * moved
          */
         if (*imbalance < busiest_load_per_task) {
                 unsigned long tmp, pwr_now, pwr_move;
                 unsigned int imbn;
 
 small_imbalance:
                 pwr_move = pwr_now = 0;
                 imbn = 2;
                 if (this_nr_running) {
                         this_load_per_task /= this_nr_running;
                         if (busiest_load_per_task > this_load_per_task)
                                 imbn = 1;
                 } else
                         this_load_per_task = SCHED_LOAD_SCALE;
 
                 if (max_load - this_load + SCHED_LOAD_SCALE_FUZZ >=
                                         busiest_load_per_task * imbn) {
                         *imbalance = busiest_load_per_task;
                         return busiest;
                 }
 
                 /*
                  * OK, we don't have enough imbalance to justify moving tasks,
                  * however we may be able to increase total CPU power used by
                  * moving them.
                  */
 
                 pwr_now += busiest->__cpu_power *
                                 min(busiest_load_per_task, max_load);
                 pwr_now += this->__cpu_power *
                                 min(this_load_per_task, this_load);
                 pwr_now /= SCHED_LOAD_SCALE;
 
                 /* Amount of load we'd subtract */
                 tmp = sg_div_cpu_power(busiest,
                                 busiest_load_per_task * SCHED_LOAD_SCALE);
                 if (max_load > tmp)
                         pwr_move += busiest->__cpu_power *
                                 min(busiest_load_per_task, max_load - tmp);
 
                 /* Amount of load we'd add */
                 if (max_load * busiest->__cpu_power <
                                 busiest_load_per_task * SCHED_LOAD_SCALE)
                         tmp = sg_div_cpu_power(this,
                                         max_load * busiest->__cpu_power);
                 else
                         tmp = sg_div_cpu_power(this,
                                 busiest_load_per_task * SCHED_LOAD_SCALE);
                 pwr_move += this->__cpu_power *
                                 min(this_load_per_task, this_load + tmp);
                 pwr_move /= SCHED_LOAD_SCALE;
 
                 /* Move if we gain throughput */
                 if (pwr_move > pwr_now)
                         *imbalance = busiest_load_per_task;
         }
 
         return busiest;
 
 out_balanced:
 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
         if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
                 goto ret;
 
         if (this == group_leader && group_leader != group_min) {
                 *imbalance = min_load_per_task;
                 return group_min;
         }
 #endif
 ret:
         *imbalance = 0;
         return NULL;
 }
 
 /*
  * find_busiest_queue - find the busiest runqueue among the cpus in group.
  */
 static struct rq *
 find_busiest_queue(struct sched_group *group, enum cpu_idle_type idle,
                    unsigned long imbalance, cpumask_t *cpus)
 {
         struct rq *busiest = NULL, *rq;
         unsigned long max_load = 0;
         int i;
 
         for_each_cpu_mask(i, group->cpumask) {
                 unsigned long wl;
 
                 if (!cpu_isset(i, *cpus))
                         continue;
 
                 rq = cpu_rq(i);
                 wl = weighted_cpuload(i);
 
                 if (rq->nr_running == 1 && wl > imbalance)
                         continue;
 
                 if (wl > max_load) {
                         max_load = wl;
                         busiest = rq;
                 }
         }
 
         return busiest;
 }
 
 /*
  * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
  * so long as it is large enough.
  */
 #define MAX_PINNED_INTERVAL     512
 
 /*
  * Check this_cpu to ensure it is balanced within domain. Attempt to move
  * tasks if there is an imbalance.
  */
 static int load_balance(int this_cpu, struct rq *this_rq,
                         struct sched_domain *sd, enum cpu_idle_type idle,
                         int *balance)
 {
         int ld_moved, all_pinned = 0, active_balance = 0, sd_idle = 0;
         struct sched_group *group;
         unsigned long imbalance;
         struct rq *busiest;
         cpumask_t cpus = CPU_MASK_ALL;
         unsigned long flags;
 
         /*
          * When power savings policy is enabled for the parent domain, idle
          * sibling can pick up load irrespective of busy siblings. In this case,
          * let the state of idle sibling percolate up as CPU_IDLE, instead of
          * portraying it as CPU_NOT_IDLE.
          */
         if (idle != CPU_NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER &&
             !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
                 sd_idle = 1;
 
         schedstat_inc(sd, lb_count[idle]);
 
 redo:
         group = find_busiest_group(sd, this_cpu, &imbalance, idle, &sd_idle,
                                    &cpus, balance);
 
         if (*balance == 0)
                 goto out_balanced;
 
         if (!group) {
                 schedstat_inc(sd, lb_nobusyg[idle]);
                 goto out_balanced;
         }
 
         busiest = find_busiest_queue(group, idle, imbalance, &cpus);
         if (!busiest) {
                 schedstat_inc(sd, lb_nobusyq[idle]);
                 goto out_balanced;
         }
 
         BUG_ON(busiest == this_rq);
 
         schedstat_add(sd, lb_imbalance[idle], imbalance);
 
         ld_moved = 0;
         if (busiest->nr_running > 1) {
                 /*
                  * Attempt to move tasks. If find_busiest_group has found
                  * an imbalance but busiest->nr_running <= 1, the group is
                  * still unbalanced. ld_moved simply stays zero, so it is
                  * correctly treated as an imbalance.
                  */
                 local_irq_save(flags);
                 double_rq_lock(this_rq, busiest);
                 ld_moved = move_tasks(this_rq, this_cpu, busiest,
                                       imbalance, sd, idle, &all_pinned);
                 double_rq_unlock(this_rq, busiest);
                 local_irq_restore(flags);
 
                 /*
                  * some other cpu did the load balance for us.
                  */
                 if (ld_moved && this_cpu != smp_processor_id())
                         resched_cpu(this_cpu);
 
                 /* All tasks on this runqueue were pinned by CPU affinity */
                 if (unlikely(all_pinned)) {
                         cpu_clear(cpu_of(busiest), cpus);
                         if (!cpus_empty(cpus))
                                 goto redo;
                         goto out_balanced;
                 }
         }
 
         if (!ld_moved) {
                 schedstat_inc(sd, lb_failed[idle]);
                 sd->nr_balance_failed++;
 
                 if (unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2)) {
 
                         spin_lock_irqsave(&busiest->lock, flags);
 
                         /* don't kick the migration_thread, if the curr
                          * task on busiest cpu can't be moved to this_cpu
                          */
                         if (!cpu_isset(this_cpu, busiest->curr->cpus_allowed)) {
                                 spin_unlock_irqrestore(&busiest->lock, flags);
                                 all_pinned = 1;
                                 goto out_one_pinned;
                         }
 
                         if (!busiest->active_balance) {
                                 busiest->active_balance = 1;
                                 busiest->push_cpu = this_cpu;
                                 active_balance = 1;
                         }
                         spin_unlock_irqrestore(&busiest->lock, flags);
                         if (active_balance)
                                 wake_up_process(busiest->migration_thread);
 
                         /*
                          * We've kicked active balancing, reset the failure
                          * counter.
                          */
                         sd->nr_balance_failed = sd->cache_nice_tries+1;
                 }
         } else
                 sd->nr_balance_failed = 0;
 
         if (likely(!active_balance)) {
                 /* We were unbalanced, so reset the balancing interval */
                 sd->balance_interval = sd->min_interval;
         } else {
                 /*
                  * If we've begun active balancing, start to back off. This
                  * case may not be covered by the all_pinned logic if there
                  * is only 1 task on the busy runqueue (because we don't call
                  * move_tasks).
                  */
                 if (sd->balance_interval < sd->max_interval)
                         sd->balance_interval *= 2;
         }
 
         if (!ld_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
             !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
                 return -1;
         return ld_moved;
 
 out_balanced:
         schedstat_inc(sd, lb_balanced[idle]);
 
         sd->nr_balance_failed = 0;
 
 out_one_pinned:
         /* tune up the balancing interval */
         if ((all_pinned && sd->balance_interval < MAX_PINNED_INTERVAL) ||
                         (sd->balance_interval < sd->max_interval))
                 sd->balance_interval *= 2;
 
         if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
             !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
                 return -1;
         return 0;
 }
 
 /*
  * Check this_cpu to ensure it is balanced within domain. Attempt to move
  * tasks if there is an imbalance.
  *
  * Called from schedule when this_rq is about to become idle (CPU_NEWLY_IDLE).
  * this_rq is locked.
  */
 static int
 load_balance_newidle(int this_cpu, struct rq *this_rq, struct sched_domain *sd)
 {
         struct sched_group *group;
         struct rq *busiest = NULL;
         unsigned long imbalance;
         int ld_moved = 0;
         int sd_idle = 0;
         int all_pinned = 0;
         cpumask_t cpus = CPU_MASK_ALL;
 
         /*
          * When power savings policy is enabled for the parent domain, idle
          * sibling can pick up load irrespective of busy siblings. In this case,
          * let the state of idle sibling percolate up as IDLE, instead of
          * portraying it as CPU_NOT_IDLE.
          */
         if (sd->flags & SD_SHARE_CPUPOWER &&
             !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
                 sd_idle = 1;
 
         schedstat_inc(sd, lb_count[CPU_NEWLY_IDLE]);
 redo:
         group = find_busiest_group(sd, this_cpu, &imbalance, CPU_NEWLY_IDLE,
                                    &sd_idle, &cpus, NULL);
         if (!group) {
                 schedstat_inc(sd, lb_nobusyg[CPU_NEWLY_IDLE]);
                 goto out_balanced;
         }
 
         busiest = find_busiest_queue(group, CPU_NEWLY_IDLE, imbalance,
                                 &cpus);
         if (!busiest) {
                 schedstat_inc(sd, lb_nobusyq[CPU_NEWLY_IDLE]);
                 goto out_balanced;
         }
 
         BUG_ON(busiest == this_rq);
 
         schedstat_add(sd, lb_imbalance[CPU_NEWLY_IDLE], imbalance);
 
         ld_moved = 0;
         if (busiest->nr_running > 1) {
                 /* Attempt to move tasks */
                 double_lock_balance(this_rq, busiest);
                 /* this_rq->clock is already updated */
                 update_rq_clock(busiest);
                 ld_moved = move_tasks(this_rq, this_cpu, busiest,
                                         imbalance, sd, CPU_NEWLY_IDLE,
                                         &all_pinned);
                 spin_unlock(&busiest->lock);
 
                 if (unlikely(all_pinned)) {
                         cpu_clear(cpu_of(busiest), cpus);
                         if (!cpus_empty(cpus))
                                 goto redo;
                 }
         }
 
         if (!ld_moved) {
                 schedstat_inc(sd, lb_failed[CPU_NEWLY_IDLE]);
                 if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
                     !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
                         return -1;
         } else
                 sd->nr_balance_failed = 0;
 
         return ld_moved;
 
 out_balanced:
         schedstat_inc(sd, lb_balanced[CPU_NEWLY_IDLE]);
         if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
             !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
                 return -1;
         sd->nr_balance_failed = 0;
 
         return 0;
 }
 
 /*
  * idle_balance is called by schedule() if this_cpu is about to become
  * idle. Attempts to pull tasks from other CPUs.
  */
 static void idle_balance(int this_cpu, struct rq *this_rq)
 {
         struct sched_domain *sd;
         int pulled_task = -1;
         unsigned long next_balance = jiffies + HZ;
 
         for_each_domain(this_cpu, sd) {
                 unsigned long interval;
 
                 if (!(sd->flags & SD_LOAD_BALANCE))
                         continue;
 
                 if (sd->flags & SD_BALANCE_NEWIDLE)
                         /* If we've pulled tasks over stop searching: */
                         pulled_task = load_balance_newidle(this_cpu,
                                                                 this_rq, sd);
 
                 interval = msecs_to_jiffies(sd->balance_interval);
                 if (time_after(next_balance, sd->last_balance + interval))
                         next_balance = sd->last_balance + interval;
                 if (pulled_task)
                         break;
         }
         if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
                 /*
                  * We are going idle. next_balance may be set based on
                  * a busy processor. So reset next_balance.
                  */
                 this_rq->next_balance = next_balance;
         }
 }
 
 /*
  * active_load_balance is run by migration threads. It pushes running tasks
  * off the busiest CPU onto idle CPUs. It requires at least 1 task to be
  * running on each physical CPU where possible, and avoids physical /
  * logical imbalances.
  *
  * Called with busiest_rq locked.
  */
 static void active_load_balance(struct rq *busiest_rq, int busiest_cpu)
 {
         int target_cpu = busiest_rq->push_cpu;
         struct sched_domain *sd;
         struct rq *target_rq;
 
         /* Is there any task to move? */
         if (busiest_rq->nr_running <= 1)
                 return;
 
         target_rq = cpu_rq(target_cpu);
 
         /*
          * This condition is "impossible", if it occurs
          * we need to fix it. Originally reported by
          * Bjorn Helgaas on a 128-cpu setup.
          */
         BUG_ON(busiest_rq == target_rq);
 
         /* move a task from busiest_rq to target_rq */
         double_lock_balance(busiest_rq, target_rq);
         update_rq_clock(busiest_rq);
         update_rq_clock(target_rq);
 
         /* Search for an sd spanning us and the target CPU. */
         for_each_domain(target_cpu, sd) {
                 if ((sd->flags & SD_LOAD_BALANCE) &&
                     cpu_isset(busiest_cpu, sd->span))
                                 break;
         }
 
         if (likely(sd)) {
                 schedstat_inc(sd, alb_count);
 
                 if (move_one_task(target_rq, target_cpu, busiest_rq,
                                   sd, CPU_IDLE))
                         schedstat_inc(sd, alb_pushed);
                 else
                         schedstat_inc(sd, alb_failed);
         }
         spin_unlock(&target_rq->lock);
 }
 
 #ifdef CONFIG_NO_HZ
 static struct {
         atomic_t load_balancer;
         cpumask_t cpu_mask;
 } nohz ____cacheline_aligned = {
         .load_balancer = ATOMIC_INIT(-1),
         .cpu_mask = CPU_MASK_NONE,
 };
 
 /*
  * This routine will try to nominate the ilb (idle load balancing)
  * owner among the cpus whose ticks are stopped. ilb owner will do the idle
  * load balancing on behalf of all those cpus. If all the cpus in the system
  * go into this tickless mode, then there will be no ilb owner (as there is
  * no need for one) and all the cpus will sleep till the next wakeup event
  * arrives...
  *
  * For the ilb owner, tick is not stopped. And this tick will be used
  * for idle load balancing. ilb owner will still be part of
  * nohz.cpu_mask..
  *
  * While stopping the tick, this cpu will become the ilb owner if there
  * is no other owner. And will be the owner till that cpu becomes busy
  * or if all cpus in the system stop their ticks at which point
  * there is no need for ilb owner.
  *
  * When the ilb owner becomes busy, it nominates another owner, during the
  * next busy scheduler_tick()
  */
 int select_nohz_load_balancer(int stop_tick)
 {
         int cpu = smp_processor_id();
 
         if (stop_tick) {
                 cpu_set(cpu, nohz.cpu_mask);
                 cpu_rq(cpu)->in_nohz_recently = 1;
 
                 /*
                  * If we are going offline and still the leader, give up!
                  */
                 if (cpu_is_offline(cpu) &&
                     atomic_read(&nohz.load_balancer) == cpu) {
                         if (atomic_cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
                                 BUG();
                         return 0;
                 }
 
                 /* time for ilb owner also to sleep */
                 if (cpus_weight(nohz.cpu_mask) == num_online_cpus()) {
                         if (atomic_read(&nohz.load_balancer) == cpu)
                                 atomic_set(&nohz.load_balancer, -1);
                         return 0;
                 }
 
                 if (atomic_read(&nohz.load_balancer) == -1) {
                         /* make me the ilb owner */
                         if (atomic_cmpxchg(&nohz.load_balancer, -1, cpu) == -1)
                                 return 1;
                 } else if (atomic_read(&nohz.load_balancer) == cpu)
                         return 1;
         } else {
                 if (!cpu_isset(cpu, nohz.cpu_mask))
                         return 0;
 
                 cpu_clear(cpu, nohz.cpu_mask);
 
                 if (atomic_read(&nohz.load_balancer) == cpu)
                         if (atomic_cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
                                 BUG();
         }
         return 0;
 }
 #endif
 
 static DEFINE_SPINLOCK(balancing);
 
 /*
  * It checks each scheduling domain to see if it is due to be balanced,
  * and initiates a balancing operation if so.
  *
  * Balancing parameters are set up in arch_init_sched_domains.
  */
 static void rebalance_domains(int cpu, enum cpu_idle_type idle)
 {
         int balance = 1;
         struct rq *rq = cpu_rq(cpu);
         unsigned long interval;
         struct sched_domain *sd;
         /* Earliest time when we have to do rebalance again */
         unsigned long next_balance = jiffies + 60*HZ;
         int update_next_balance = 0;
 
         for_each_domain(cpu, sd) {
                 if (!(sd->flags & SD_LOAD_BALANCE))
                         continue;
 
                 interval = sd->balance_interval;
                 if (idle != CPU_IDLE)
                         interval *= sd->busy_factor;
 
                 /* scale ms to jiffies */
                 interval = msecs_to_jiffies(interval);
                 if (unlikely(!interval))
                         interval = 1;
                 if (interval > HZ*NR_CPUS/10)
                         interval = HZ*NR_CPUS/10;
 
 
                 if (sd->flags & SD_SERIALIZE) {
                         if (!spin_trylock(&balancing))
                                 goto out;
                 }
 
                 if (time_after_eq(jiffies, sd->last_balance + interval)) {
                         if (load_balance(cpu, rq, sd, idle, &balance)) {
                                 /*
                                  * We've pulled tasks over so either we're no
                                  * longer idle, or one of our SMT siblings is
                                  * not idle.
                                  */
                                 idle = CPU_NOT_IDLE;
                         }
                         sd->last_balance = jiffies;
                 }
                 if (sd->flags & SD_SERIALIZE)
                         spin_unlock(&balancing);
 out:
                 if (time_after(next_balance, sd->last_balance + interval)) {
                         next_balance = sd->last_balance + interval;
                         update_next_balance = 1;
                 }
 
                 /*
                  * Stop the load balance at this level. There is another
                  * CPU in our sched group which is doing load balancing more
                  * actively.
                  */
                 if (!balance)
                         break;
         }
 
         /*
          * next_balance will be updated only when there is a need.
          * When the cpu is attached to null domain for ex, it will not be
          * updated.
          */
         if (likely(update_next_balance))
                 rq->next_balance = next_balance;
 }
 
 /*
  * run_rebalance_domains is triggered when needed from the scheduler tick.
  * In CONFIG_NO_HZ case, the idle load balance owner will do the
  * rebalancing for all the cpus for whom scheduler ticks are stopped.
  */
 static void run_rebalance_domains(struct softirq_action *h)
 {
         int this_cpu = raw_smp_processor_id();
         struct rq *this_rq = cpu_rq(this_cpu);
         enum cpu_idle_type idle = this_rq->idle_at_tick ?
                                                 CPU_IDLE : CPU_NOT_IDLE;
 
         rebalance_domains(this_cpu, idle);
 
 #ifdef CONFIG_NO_HZ
         /*
          * If this cpu is the owner for idle load balancing, then do the
          * balancing on behalf of the other idle cpus whose ticks are
          * stopped.
          */
         if (this_rq->idle_at_tick &&
             atomic_read(&nohz.load_balancer) == this_cpu) {
                 cpumask_t cpus = nohz.cpu_mask;
                 struct rq *rq;
                 int balance_cpu;
 
                 cpu_clear(this_cpu, cpus);
                 for_each_cpu_mask(balance_cpu, cpus) {
                         /*
                          * If this cpu gets work to do, stop the load balancing
                          * work being done for other cpus. Next load
                          * balancing owner will pick it up.
                          */
                         if (need_resched())
                                 break;
 
                         rebalance_domains(balance_cpu, CPU_IDLE);
 
                         rq = cpu_rq(balance_cpu);
                         if (time_after(this_rq->next_balance, rq->next_balance))
                                 this_rq->next_balance = rq->next_balance;
                 }
         }
 #endif
 }
 
 /*
  * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
  *
  * In case of CONFIG_NO_HZ, this is the place where we nominate a new
  * idle load balancing owner or decide to stop the periodic load balancing,
  * if the whole system is idle.
  */
 static inline void trigger_load_balance(struct rq *rq, int cpu)
 {
 #ifdef CONFIG_NO_HZ
         /*
          * If we were in the nohz mode recently and busy at the current
          * scheduler tick, then check if we need to nominate new idle
          * load balancer.
          */
         if (rq->in_nohz_recently && !rq->idle_at_tick) {
                 rq->in_nohz_recently = 0;
 
                 if (atomic_read(&nohz.load_balancer) == cpu) {
                         cpu_clear(cpu, nohz.cpu_mask);
                         atomic_set(&nohz.load_balancer, -1);
                 }
 
                 if (atomic_read(&nohz.load_balancer) == -1) {
                         /*
                          * simple selection for now: Nominate the
                          * first cpu in the nohz list to be the next
                          * ilb owner.
                          *
                          * TBD: Traverse the sched domains and nominate
                          * the nearest cpu in the nohz.cpu_mask.
                          */
                         int ilb = first_cpu(nohz.cpu_mask);
 
                         if (ilb != NR_CPUS)
                                 resched_cpu(ilb);
                 }
         }
 
         /*
          * If this cpu is idle and doing idle load balancing for all the
          * cpus with ticks stopped, is it time for that to stop?
          */
         if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) == cpu &&
             cpus_weight(nohz.cpu_mask) == num_online_cpus()) {
                 resched_cpu(cpu);
                 return;
         }
 
         /*
          * If this cpu is idle and the idle load balancing is done by
          * someone else, then no need raise the SCHED_SOFTIRQ
          */
         if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) != cpu &&
             cpu_isset(cpu, nohz.cpu_mask))
                 return;
 #endif
         if (time_after_eq(jiffies, rq->next_balance))
                 raise_softirq(SCHED_SOFTIRQ);
 }
 
 #else   /* CONFIG_SMP */
 
 /*
  * on UP we do not need to balance between CPUs:
  */
 static inline void idle_balance(int cpu, struct rq *rq)
 {
 }
 
 #endif
 
 DEFINE_PER_CPU(struct kernel_stat, kstat);
 
 EXPORT_PER_CPU_SYMBOL(kstat);
 
 /*
  * Return p->sum_exec_runtime plus any more ns on the sched_clock
  * that have not yet been banked in case the task is currently running.
  */
 unsigned long long task_sched_runtime(struct task_struct *p)
 {
         unsigned long flags;
         u64 ns, delta_exec;
         struct rq *rq;
 
         rq = task_rq_lock(p, &flags);
         ns = p->se.sum_exec_runtime;
         if (task_current(rq, p)) {
                 update_rq_clock(rq);
                 delta_exec = rq->clock - p->se.exec_start;
                 if ((s64)delta_exec > 0)
                         ns += delta_exec;
         }
         task_rq_unlock(rq, &flags);
 
         return ns;
 }
 
 /*
  * Account user cpu time to a process.
  * @p: the process that the cpu time gets accounted to
  * @cputime: the cpu time spent in user space since the last update
  */
 void account_user_time(struct task_struct *p, cputime_t cputime)
 {
         struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
         cputime64_t tmp;
 
         p->utime = cputime_add(p->utime, cputime);
 
         /* Add user time to cpustat. */
         tmp = cputime_to_cputime64(cputime);
         if (rt_task(p))
                 cpustat->user_rt = cputime64_add(cpustat->user_rt, tmp);
         else if (TASK_NICE(p) > 0)
                 cpustat->nice = cputime64_add(cpustat->nice, tmp);
         else
                 cpustat->user = cputime64_add(cpustat->user, tmp);
 }
 
 /*
  * Account guest cpu time to a process.
  * @p: the process that the cpu time gets accounted to
  * @cputime: the cpu time spent in virtual machine since the last update
  */
 static void account_guest_time(struct task_struct *p, cputime_t cputime)
 {
         cputime64_t tmp;
         struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
 
         tmp = cputime_to_cputime64(cputime);
 
         p->utime = cputime_add(p->utime, cputime);
         p->gtime = cputime_add(p->gtime, cputime);
 
         cpustat->user = cputime64_add(cpustat->user, tmp);
         cpustat->guest = cputime64_add(cpustat->guest, tmp);
 }
 
 /*
  * Account scaled user cpu time to a process.
  * @p: the process that the cpu time gets accounted to
  * @cputime: the cpu time spent in user space since the last update
  */
 void account_user_time_scaled(struct task_struct *p, cputime_t cputime)
 {
         p->utimescaled = cputime_add(p->utimescaled, cputime);
 }
 
 /*
  * Account system cpu time to a process.
  * @p: the process that the cpu time gets accounted to
  * @hardirq_offset: the offset to subtract from hardirq_count()
  * @cputime: the cpu time spent in kernel space since the last update
  */
 void account_system_time(struct task_struct *p, int hardirq_offset,
                          cputime_t cputime)
 {
         struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
         struct rq *rq = this_rq();
         cputime64_t tmp;
 
         if ((p->flags & PF_VCPU) && (irq_count() - hardirq_offset == 0))
                 return account_guest_time(p, cputime);
 
         p->stime = cputime_add(p->stime, cputime);
 
         /* Add system time to cpustat. */
         tmp = cputime_to_cputime64(cputime);
         if (hardirq_count() - hardirq_offset || (p->flags & PF_HARDIRQ))
                 cpustat->irq = cputime64_add(cpustat->irq, tmp);
         else if (softirq_count() || (p->flags & PF_SOFTIRQ))
                 cpustat->softirq = cputime64_add(cpustat->softirq, tmp);
         else if (rt_task(p))
                 cpustat->system_rt = cputime64_add(cpustat->system_rt, tmp);
         else if (p != rq->idle)
                 cpustat->system = cputime64_add(cpustat->system, tmp);
         else if (atomic_read(&rq->nr_iowait) > 0)
                 cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
         else
                 cpustat->idle = cputime64_add(cpustat->idle, tmp);
         /* Account for system time used */
         acct_update_integrals(p);
 }
 
 /*
  * Account scaled system cpu time to a process.
  * @p: the process that the cpu time gets accounted to
  * @hardirq_offset: the offset to subtract from hardirq_count()
  * @cputime: the cpu time spent in kernel space since the last update
  */
 void account_system_time_scaled(struct task_struct *p, cputime_t cputime)
 {
         p->stimescaled = cputime_add(p->stimescaled, cputime);
 }
 
 /*
  * Account for involuntary wait time.
  * @p: the process from which the cpu time has been stolen
  * @steal: the cpu time spent in involuntary wait
  */
 void account_steal_time(struct task_struct *p, cputime_t steal)
 {
         struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
         cputime64_t tmp = cputime_to_cputime64(steal);
         struct rq *rq = this_rq();
 
         if (p == rq->idle) {
                 p->stime = cputime_add(p->stime, steal);
                 if (atomic_read(&rq->nr_iowait) > 0)
                         cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
                 else
                         cpustat->idle = cputime64_add(cpustat->idle, tmp);
         } else
                 cpustat->steal = cputime64_add(cpustat->steal, tmp);
 }
 
 /*
  * This function gets called by the timer code, with HZ frequency.
  * We call it with interrupts disabled.
  *
  * It also gets called by the fork code, when changing the parent's
  * timeslices.
  */
 void scheduler_tick(void)
 {
         int cpu = smp_processor_id();
         struct rq *rq = cpu_rq(cpu);
         struct task_struct *curr = rq->curr;
 
         sched_clock_tick();
 
         BUG_ON(!irqs_disabled());
 
         spin_lock(&rq->lock);
         update_rq_clock(rq);
         update_cpu_load(rq);
         curr->sched_class->task_tick(rq, curr, 0);
         update_sched_rt_period(rq);
         spin_unlock(&rq->lock);
 
 #ifdef CONFIG_SMP
         rq->idle_at_tick = idle_cpu(cpu);
         trigger_load_balance(rq, cpu);
 #endif
 }
 
 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
                                 defined(CONFIG_PREEMPT_TRACER) || \
                                 defined(CONFIG_PREEMPT_TRACE))
 
 static inline unsigned long get_parent_ip(unsigned long addr)
 {
         if (in_lock_functions(addr)) {
                 addr = CALLER_ADDR2;
                 if (in_lock_functions(addr))
                         addr = CALLER_ADDR3;
         }
         return addr;
 }
 
 void __kprobes add_preempt_count(int val)
 {
         unsigned long eip = CALLER_ADDR0;
         unsigned long parent_eip = get_parent_ip(CALLER_ADDR1);
 
 #ifdef CONFIG_DEBUG_PREEMPT
         /*
          * Underflow?
          */
         if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
                 return;
 #endif
         preempt_count() += val;
 #ifdef CONFIG_PREEMPT_TRACE
         if (val <= 10) {
                 unsigned int idx = preempt_count() & PREEMPT_MASK;
                 if (idx < MAX_PREEMPT_TRACE) {
                         current->preempt_trace_eip[idx] = eip;
                         current->preempt_trace_parent_eip[idx] = parent_eip;
                 }
         }
 #endif
 #ifdef CONFIG_DEBUG_PREEMPT
         /*
          * Spinlock count overflowing soon?
          */
         DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
                                 PREEMPT_MASK - 10);
 #endif
         if (preempt_count() == val)
                 trace_preempt_off(eip, parent_eip);
 }
 EXPORT_SYMBOL(add_preempt_count);
 
 void __kprobes sub_preempt_count(int val)
 {
 #ifdef CONFIG_DEBUG_PREEMPT
         /*
          * Underflow?
          */
         if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
                 return;
         /*
          * Is the spinlock portion underflowing?
          */
         if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
                         !(preempt_count() & PREEMPT_MASK)))
                 return;
 #endif
 
         if (preempt_count() == val)
                 trace_preempt_on(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
         preempt_count() -= val;
 }
 EXPORT_SYMBOL(sub_preempt_count);
 
 #endif
 
 /*
  * Print scheduling while atomic bug:
  */
 static noinline void __schedule_bug(struct task_struct *prev)
 {
         struct pt_regs *regs = get_irq_regs();
 
         printk(KERN_ERR "BUG: scheduling while atomic: %s/0x%08x/%d, CPU#%d\n",
                prev->comm, preempt_count(), prev->pid, smp_processor_id());
 
         debug_show_held_locks(prev);
         if (irqs_disabled())
                 print_irqtrace_events(prev);
 
         if (regs)
                 show_regs(regs);
         else
                 dump_stack();
 }
 
 /*
  * Various schedule()-time debugging checks and statistics:
  */
 static inline void schedule_debug(struct task_struct *prev)
 {
         WARN_ON(system_state == SYSTEM_BOOTING);
 
         /*
          * Test if we are atomic. Since do_exit() needs to call into
          * schedule() atomically, we ignore that path for now.
          * Otherwise, whine if we are scheduling when we should not be.
          */
         if (unlikely(in_atomic_preempt_off()) && unlikely(!prev->exit_state))
                 __schedule_bug(prev);
 
         profile_hit(SCHED_PROFILING, __builtin_return_address(0));
 
         schedstat_inc(this_rq(), sched_count);
 #ifdef CONFIG_SCHEDSTATS
         if (unlikely(prev->lock_depth >= 0)) {
                 schedstat_inc(this_rq(), bkl_count);
                 schedstat_inc(prev, sched_info.bkl_count);
         }
 #endif
 }
 
 /*
  * Pick up the highest-prio task:
  */
 static inline struct task_struct *
 pick_next_task(struct rq *rq, struct task_struct *prev)
 {
         const struct sched_class *class;
         struct task_struct *p;
 
         /*
          * Optimization: we know that if all tasks are in
          * the fair class we can call that function directly:
          */
         if (likely(rq->nr_running == rq->cfs.nr_running)) {
                 p = fair_sched_class.pick_next_task(rq);
                 if (likely(p))
                         return p;
         }
 
         class = sched_class_highest;
         for ( ; ; ) {
                 p = class->pick_next_task(rq);
                 if (p)
                         return p;
                 /*
                  * Will never be NULL as the idle class always
                  * returns a non-NULL p:
                  */
                 class = class->next;
         }
 }
 
 /*
  * schedule() is the main scheduler function.
  */
 asmlinkage void __sched __schedule(void)
 {
         struct task_struct *prev, *next;
         unsigned long *switch_count;
         struct rq *rq;
         int cpu;
 
         rcu_preempt_boost();
 
         preempt_disable();
         cpu = smp_processor_id();
         rq = cpu_rq(cpu);
         rcu_qsctr_inc(cpu);
         prev = rq->curr;
         switch_count = &prev->nivcsw;
 
         release_kernel_lock(prev);
 
         schedule_debug(prev);
 
         hrtick_clear(rq);
 
         /*
          * Do the rq-clock update outside the rq lock:
          */
         local_irq_disable();
         update_rq_clock(rq);
         spin_lock(&rq->lock);
         cpu = smp_processor_id();
         clear_tsk_need_resched(prev);
         clear_tsk_need_resched_delayed(prev);
 
         if ((prev->state & ~TASK_RUNNING_MUTEX) &&
                         !(preempt_count() & PREEMPT_ACTIVE)) {
                 if (unlikely((prev->state & TASK_INTERRUPTIBLE) &&
                                 signal_pending(prev))) {
                         prev->state = TASK_RUNNING;
                 } else {
                         touch_softlockup_watchdog();
                         deactivate_task(rq, prev, 1);
                 }
                 switch_count = &prev->nvcsw;
         }
 
         if (preempt_count() & PREEMPT_ACTIVE)
                 sub_preempt_count(PREEMPT_ACTIVE);
 
 #ifdef CONFIG_SMP
         if (prev->sched_class->pre_schedule)
                 prev->sched_class->pre_schedule(rq, prev);
 #endif
 
         if (unlikely(!rq->nr_running))
                 idle_balance(cpu, rq);
 
         prev->sched_class->put_prev_task(rq, prev);
         next = pick_next_task(rq, prev);
 
         sched_info_switch(prev, next);
 
         if (likely(prev != next)) {
                 rq->nr_switches++;
                 rq->curr = next;
                 ++*switch_count;
 
                 context_switch(rq, prev, next); /* unlocks the rq */
                 /*
                  * the context switch might have flipped the stack from under
                  * us, hence refresh the local variables.
                  */
                 cpu = smp_processor_id();
                 rq = cpu_rq(cpu);
                 __preempt_enable_no_resched();
         } else {
                 __preempt_enable_no_resched();
                 spin_unlock(&rq->lock);
         }
 
         hrtick_set(rq);
 
         reacquire_kernel_lock(current);
         if (!irqs_disabled()) {
                 static int once = 1;
                 if (once) {
                         once = 0;
                         print_irqtrace_events(current);
                         WARN_ON(1);
                 }
         }
 
 }
 
 /*
  * schedule() is the main scheduler function.
  */
 asmlinkage void __sched schedule(void)
 {
         WARN_ON(system_state == SYSTEM_BOOTING);
         /*
          * Test if we have interrupts disabled.
          */
         if (unlikely(irqs_disabled())) {
                 printk(KERN_ERR "BUG: scheduling with irqs disabled: "
                        "%s/0x%08x/%d\n", current->comm, preempt_count(),
                        current->pid);
                 print_symbol("caller is %s\n",
                              (long)__builtin_return_address(0));
                 dump_stack();
         }
 
         if (unlikely(current->flags & PF_NOSCHED)) {
                 current->flags &= ~PF_NOSCHED;
                 printk(KERN_ERR "%s:%d userspace BUG: scheduling in "
                        "user-atomic context!\n", current->comm, current->pid);
                 dump_stack();
                 send_sig(SIGUSR2, current, 1);
         }
 
         local_irq_disable();
 
         do {
                 __schedule();
         } while (unlikely(test_thread_flag(TIF_NEED_RESCHED) ||
                           test_thread_flag(TIF_NEED_RESCHED_DELAYED)));
 
         local_irq_enable();
 }
 EXPORT_SYMBOL(schedule);
 
 #ifdef CONFIG_PREEMPT
 
 /*
  * Global flag to turn preemption off on a CONFIG_PREEMPT kernel:
  */
 int kernel_preemption = 1;
 
 static int __init preempt_setup (char *str)
 {
         if (!strncmp(str, "off", 3)) {
                 if (kernel_preemption) {
                         printk(KERN_INFO "turning off kernel preemption!\n");
                         kernel_preemption = 0;
                 }
                 return 1;
         }
         if (!strncmp(str, "on", 2)) {
                 if (!kernel_preemption) {
                         printk(KERN_INFO "turning on kernel preemption!\n");
                         kernel_preemption = 1;
                 }
                 return 1;
         }
         get_option(&str, &kernel_preemption);
 
         return 1;
 }
 
 __setup("preempt=", preempt_setup);
 
 /*
  * 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();
         struct task_struct *task = current;
         int saved_lock_depth;
 
         if (!kernel_preemption)
                 return;
         /*
          * If there is a non-zero preempt_count or interrupts are disabled,
          * we do not want to preempt the current task. Just return..
          */
         if (likely(ti->preempt_count || irqs_disabled()))
                 return;
 
         do {
                 local_irq_disable();
                 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:
                  */
                 saved_lock_depth = task->lock_depth;
                 task->lock_depth = -1;
                 __schedule();
                 task->lock_depth = saved_lock_depth;
                 local_irq_enable();
 
                 /*
                  * Check again in case we missed a preemption opportunity
                  * between schedule and now.
                  */
                 barrier();
         } while (unlikely(test_thread_flag(TIF_NEED_RESCHED)));
 }
 EXPORT_SYMBOL(preempt_schedule);
 
 /*
  * this is is the entry point for the IRQ return path. Called with
  * interrupts disabled.  To avoid infinite irq-entry recursion problems
  * with fast-paced IRQ sources we do all of this carefully to never
  * enable interrupts again.
  */
 asmlinkage void __sched preempt_schedule_irq(void)
 {
         struct thread_info *ti = current_thread_info();
         struct task_struct *task = current;
         int saved_lock_depth;
 
         if (!kernel_preemption)
                 return;
         /*
          * If there is a non-zero preempt_count then just return.
          * (interrupts are disabled)
          */
         if (unlikely(ti->preempt_count))
                 return;
 
         do {
                 local_irq_disable();
                 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:
                  */
                 saved_lock_depth = task->lock_depth;
                 task->lock_depth = -1;
                 __schedule();
                 local_irq_disable();
                 task->lock_depth = saved_lock_depth;
 
                 /*
                  * Check again in case we missed a preemption opportunity
                  * between schedule and now.
                  */
                 barrier();
         } while (unlikely(test_thread_flag(TIF_NEED_RESCHED)));
 }
 
 #endif /* CONFIG_PREEMPT */
 
 int default_wake_function(wait_queue_t *curr, unsigned mode, int sync,
                           void *key)
 {
         return try_to_wake_up(curr->private, mode | TASK_RUNNING_MUTEX,
                               sync, 0);
 }
 EXPORT_SYMBOL(default_wake_function);
 
 /*
  * The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just
  * wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve
  * number) then we wake all the non-exclusive tasks and one exclusive task.
  *
  * There are circumstances in which we can try to wake a task which has already
  * started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
  * zero in this (rare) case, and we handle it by continuing to scan the queue.
  */
 static void __wake_up_common(wait_queue_head_t *q, unsigned int mode,
                              int nr_exclusive, int sync, void *key)
 {
         wait_queue_t *curr, *next;
 
         list_for_each_entry_safe(curr, next, &q->task_list, task_list) {
                 unsigned flags = curr->flags;
 
                 if (curr->func(curr, mode, sync, key) &&
                                 (flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive)
                         break;
         }
 }
 
 /**
  * __wake_up - wake up threads blocked on a waitqueue.
  * @q: the waitqueue
  * @mode: which threads
  * @nr_exclusive: how many wake-one or wake-many threads to wake up
  * @key: is directly passed to the wakeup function
  */
 void __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, 1, key);
         spin_unlock_irqrestore(&q->lock, flags);
         preempt_check_resched_delayed();
 }
 EXPORT_SYMBOL(__wake_up);
 
 /*
  * Same as __wake_up but called with the spinlock in wait_queue_head_t held.
  */
 void __wake_up_locked(wait_queue_head_t *q, unsigned int mode)
 {
         __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
 __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
 {
         unsigned long flags;
         int sync = 1;
 
         if (unlikely(!q))
                 return;
 
         if (unlikely(!nr_exclusive))
                 sync = 0;
 
         spin_lock_irqsave(&q->lock, flags);
         __wake_up_common(q, mode, nr_exclusive, sync, NULL);
         spin_unlock_irqrestore(&q->lock, flags);
 }
 EXPORT_SYMBOL_GPL(__wake_up_sync);      /* For internal use only */
 
 void complete(struct completion *x)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&x->wait.lock, flags);
         x->done++;
         __wake_up_common(&x->wait, TASK_NORMAL, 1, 1, NULL);
         spin_unlock_irqrestore(&x->wait.lock, flags);
         preempt_check_resched_delayed();
 }
 EXPORT_SYMBOL(complete);
 
 void complete_all(struct completion *x)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&x->wait.lock, flags);
         x->done += UINT_MAX/2;
         __wake_up_common(&x->wait, TASK_NORMAL, 0, 1, NULL);
         spin_unlock_irqrestore(&x->wait.lock, flags);
 }
 EXPORT_SYMBOL(complete_all);
 
 unsigned int  completion_done(struct completion *x)
 {
         return x->done;
 }
 EXPORT_SYMBOL(completion_done);
 
 static inline long __sched
 do_wait_for_common(struct completion *x, long timeout, int state)
 {
         if (!x->done) {
                 DECLARE_WAITQUEUE(wait, current);
 
                 wait.flags |= WQ_FLAG_EXCLUSIVE;
                 __add_wait_queue_tail(&x->wait, &wait);
                 do {
                         if ((state == TASK_INTERRUPTIBLE &&
                              signal_pending(current)) ||
                             (state == TASK_KILLABLE &&
                              fatal_signal_pending(current))) {
                                 __remove_wait_queue(&x->wait, &wait);
                                 return -ERESTARTSYS;
                         }
                         __set_current_state(state);
                         spin_unlock_irq(&x->wait.lock);
                         timeout = schedule_timeout(timeout);
                         spin_lock_irq(&x->wait.lock);
                         if (!timeout) {
                                 __remove_wait_queue(&x->wait, &wait);
                                 return timeout;
                         }
                 } while (!x->done);
                 __remove_wait_queue(&x->wait, &wait);
         }
         x->done--;
         return timeout;
 }
 
 static long __sched
 wait_for_common(struct completion *x, long timeout, int state)
 {
         might_sleep();
 
         spin_lock_irq(&x->wait.lock);
         timeout = do_wait_for_common(x, timeout, state);
         spin_unlock_irq(&x->wait.lock);
         return timeout;
 }
 
 void __sched wait_for_completion(struct completion *x)
 {
         wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
 }
 EXPORT_SYMBOL(wait_for_completion);
 
 unsigned long __sched
 wait_for_completion_timeout(struct completion *x, unsigned long timeout)
 {
         return wait_for_common(x, timeout, TASK_UNINTERRUPTIBLE);
 }
 EXPORT_SYMBOL(wait_for_completion_timeout);
 
 int __sched wait_for_completion_interruptible(struct completion *x)
 {
         long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE);
         if (t == -ERESTARTSYS)
                 return t;
         return 0;
 }
 EXPORT_SYMBOL(wait_for_completion_interruptible);
 
 unsigned long __sched
 wait_for_completion_interruptible_timeout(struct completion *x,
                                           unsigned long timeout)
 {
         return wait_for_common(x, timeout, TASK_INTERRUPTIBLE);
 }
 EXPORT_SYMBOL(wait_for_completion_interruptible_timeout);
 
 int __sched wait_for_completion_killable(struct completion *x)
 {
         long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_KILLABLE);
         if (t == -ERESTARTSYS)
                 return t;
         return 0;
 }
 EXPORT_SYMBOL(wait_for_completion_killable);
 
 static long __sched
 sleep_on_common(wait_queue_head_t *q, int state, long timeout)
 {
         unsigned long flags;
         wait_queue_t wait;
 
         init_waitqueue_entry(&wait, current);
 
         __set_current_state(state);
 
         spin_lock_irqsave(&q->lock, flags);
         __add_wait_queue(q, &wait);
         spin_unlock(&q->lock);
         timeout = schedule_timeout(timeout);
         spin_lock_irq(&q->lock);
         __remove_wait_queue(q, &wait);
         spin_unlock_irqrestore(&q->lock, flags);
 
         return timeout;
 }
 
 void __sched interruptible_sleep_on(wait_queue_head_t *q)
 {
         sleep_on_common(q, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 }
 EXPORT_SYMBOL(interruptible_sleep_on);
 
 long __sched
 interruptible_sleep_on_timeout(wait_queue_head_t *q, long timeout)
 {
         return sleep_on_common(q, TASK_INTERRUPTIBLE, timeout);
 }
 EXPORT_SYMBOL(interruptible_sleep_on_timeout);
 
 void __sched sleep_on(wait_queue_head_t *q)
 {
         sleep_on_common(q, TASK_UNINTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 }
 EXPORT_SYMBOL(sleep_on);
 
 long __sched sleep_on_timeout(wait_queue_head_t *q, long timeout)
 {
         return sleep_on_common(q, TASK_UNINTERRUPTIBLE, timeout);
 }
 EXPORT_SYMBOL(sleep_on_timeout);
 
 /*
  * task_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
  * and by rcupreempt-boost to boost priorities of tasks sleeping
  * with rcu locks.
  */
 void task_setprio(struct task_struct *p, int prio)
 {
         unsigned long flags;
         int oldprio, prev_resched, on_rq, running;
         struct rq *rq;
         const struct sched_class *prev_class = p->sched_class;
 
         BUG_ON(prio < 0 || prio > MAX_PRIO);
 
         rq = task_rq_lock(p, &flags);
 
         /*
          * Idle task boosting is a nono in general. There is one
          * exception, when NOHZ is active:
          *
          * The idle task calls get_next_timer_interrupt() and holds
          * the timer wheel base->lock on the CPU and another CPU wants
          * to access the timer (probably to cancel it). We can safely
          * ignore the boosting request, as the idle CPU runs this code
          * with interrupts disabled and will complete the lock
          * protected section without being interrupted. So there is no
          * real need to boost.
          */
         if (unlikely(p == rq->idle)) {
                 WARN_ON(p != rq->curr);
                 WARN_ON(p->pi_blocked_on);
                 goto out_unlock;
         }
 
         update_rq_clock(rq);
 
         oldprio = p->prio;
         on_rq = p->se.on_rq;
         running = task_current(rq, p);
         if (on_rq)
                 dequeue_task(rq, p, 0);
         if (running)
                 p->sched_class->put_prev_task(rq, p);
 
         if (rt_prio(prio))
                 p->sched_class = &rt_sched_class;
         else
                 p->sched_class = &fair_sched_class;
 
         p->prio = prio;
 
 //      trace_special_pid(p->pid, __PRIO(oldprio), PRIO(p));
         prev_resched = _need_resched();
 
         if (running)
                 p->sched_class->set_curr_task(rq);
         if (on_rq) {
                 enqueue_task(rq, p, 0);
 
                 check_class_changed(rq, p, prev_class, oldprio, running);
         }
 //      trace_special(prev_resched, _need_resched(), 0);
 
 out_unlock:
         task_rq_unlock(rq, &flags);
 }
 
 void set_user_nice(struct task_struct *p, long nice)
 {
         int old_prio, delta, on_rq;
         unsigned long flags;
         struct rq *rq;
 
         if (TASK_NICE(p) == nice || nice < -20 || nice > 19)
                 return;
         /*
          * We have to be careful, if called from sys_setpriority(),
          * the task might be in the middle of scheduling on another CPU.
          */
         rq = task_rq_lock(p, &flags);
         update_rq_clock(rq);
         /*
          * The RT priorities are set via sched_setscheduler(), but we still
          * allow the 'normal' nice value to be set - but as expected
          * it wont have any effect on scheduling until the task is
          * SCHED_FIFO/SCHED_RR:
          */
         if (task_has_rt_policy(p)) {
                 p->static_prio = NICE_TO_PRIO(nice);
                 goto out_unlock;
         }
         on_rq = p->se.on_rq;
         if (on_rq) {
                 dequeue_task(rq, p, 0);
                 dec_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 (on_rq) {
                 enqueue_task(rq, p, 0);
                 inc_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(task_nice);
 
 /**
  * idle_cpu - is a given cpu idle currently?
  * @cpu: the processor in question.
  */
 int idle_cpu(int cpu)
 {
         return cpu_curr(cpu) == cpu_rq(cpu)->idle;
 }
 
 /**
  * idle_task - return the idle task for a given cpu.
  * @cpu: the processor in question.
  */
 struct task_struct *idle_task(int cpu)
 {
         return cpu_rq(cpu)->idle;
 }
 
 /**
  * find_process_by_pid - find a process with a matching PID value.
  * @pid: the pid in question.
  */
 static struct task_struct *find_process_by_pid(pid_t pid)
 {
         return pid ? find_task_by_vpid(pid) : current;
 }
 
 /* Actually do priority change: must hold rq lock. */
 static void
 __setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio)
 {
         BUG_ON(p->se.on_rq);
 
         p->policy = policy;
         switch (p->policy) {
         case SCHED_NORMAL:
         case SCHED_BATCH:
         case SCHED_IDLE:
                 p->sched_class = &fair_sched_class;
                 break;
         case SCHED_FIFO:
         case SCHED_RR:
                 p->sched_class = &rt_sched_class;
                 break;
         }
 
         p->rt_priority = prio;
         p->normal_prio = normal_prio(p);
         /* we are holding p->pi_lock already */
         p->prio = rt_mutex_getprio(p);
         set_load_weight(p);
 }
 
 /**
  * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
  * @p: the task in question.
  * @policy: new policy.
  * @param: structure containing the new RT priority.
  *
  * NOTE that the task may be already dead.
  */
 int sched_setscheduler(struct task_struct *p, int policy,
                        struct sched_param *param)
 {
         int retval, oldprio, oldpolicy = -1, on_rq, running;
         unsigned long flags;
         const struct sched_class *prev_class = p->sched_class;
         struct rq *rq;
 
         /* may grab non-irq protected spin_locks */
         BUG_ON(in_interrupt());
 recheck:
         /* double check policy once rq lock held */
         if (policy < 0)
                 policy = oldpolicy = p->policy;
         else if (policy != SCHED_FIFO && policy != SCHED_RR &&
                         policy != SCHED_NORMAL && policy != SCHED_BATCH &&
                         policy != SCHED_IDLE)
                 return -EINVAL;
         /*
          * Valid priorities for SCHED_FIFO and SCHED_RR are
          * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
          * SCHED_BATCH and SCHED_IDLE is 0.
          */
         if (param->sched_priority < 0 ||
             (p->mm && param->sched_priority > MAX_USER_RT_PRIO-1) ||
             (!p->mm && param->sched_priority > MAX_RT_PRIO-1))
                 return -EINVAL;
         if (rt_policy(policy) != (param->sched_priority != 0))
                 return -EINVAL;
 
         /*
          * Allow unprivileged RT tasks to decrease priority:
          */
         if (!capable(CAP_SYS_NICE)) {
                 if (rt_policy(policy)) {
                         unsigned long rlim_rtprio;
 
                         if (!lock_task_sighand(p, &flags))
                                 return -ESRCH;
                         rlim_rtprio = p->signal->rlim[RLIMIT_RTPRIO].rlim_cur;
                         unlock_task_sighand(p, &flags);
 
                         /* can't set/change the rt policy */
                         if (policy != p->policy && !rlim_rtprio)
                                 return -EPERM;
 
                         /* can't increase priority */
                         if (param->sched_priority > p->rt_priority &&
                             param->sched_priority > rlim_rtprio)
                                 return -EPERM;
                 }
                 /*
                  * Like positive nice levels, dont allow tasks to
                  * move out of SCHED_IDLE either:
                  */
                 if (p->policy == SCHED_IDLE && policy != SCHED_IDLE)
                         return -EPERM;
 
                 /* can't change other user's priorities */
                 if ((current->euid != p->euid) &&
                     (current->euid != p->uid))
                         return -EPERM;
         }
 
 #ifdef CONFIG_RT_GROUP_SCHED
         /*
          * Do not allow realtime tasks into groups that have no runtime
          * assigned.
          */
         if (rt_policy(policy) && task_group(p)->rt_runtime == 0)
                 return -EPERM;
 #endif
 
         retval = security_task_setscheduler(p, policy, param);
         if (retval)
                 return retval;
         /*
          * make sure no PI-waiters arrive (or leave) while we are
          * changing the priority of the task:
          */
         spin_lock_irqsave(&p->pi_lock, flags);
         /*
          * To be able to change p->policy safely, the apropriate
          * runqueue lock must be held.
          */
         rq = __task_rq_lock(p);
         /* recheck policy now with rq lock held */
         if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
                 policy = oldpolicy = -1;
                 __task_rq_unlock(rq);
                 spin_unlock_irqrestore(&p->pi_lock, flags);
                 goto recheck;
         }
         update_rq_clock(rq);
         on_rq = p->se.on_rq;
         running = task_current(rq, p);
         if (on_rq)
                 deactivate_task(rq, p, 0);
         if (running)
                 p->sched_class->put_prev_task(rq, p);
 
         oldprio = p->prio;
         __setscheduler(rq, p, policy, param->sched_priority);
 
         if (running)
                 p->sched_class->set_curr_task(rq);
         if (on_rq) {
                 activate_task(rq, p, 0);
 
                 check_class_changed(rq, p, prev_class, oldprio, running);
         }
         __task_rq_unlock(rq);
         spin_unlock_irqrestore(&p->pi_lock, flags);
 
         rt_mutex_adjust_pi(p);
 
         return 0;
 }
 EXPORT_SYMBOL_GPL(sched_setscheduler);
 
 static int
 do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
 {
         struct sched_param lparam;
         struct task_struct *p;
         int retval;
 
         if (!param || pid < 0)
                 return -EINVAL;
         if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
                 return -EFAULT;
 
         rcu_read_lock();
         retval = -ESRCH;
         p = find_process_by_pid(pid);
         if (p != NULL)
                 retval = sched_setscheduler(p, policy, &lparam);
         rcu_read_unlock();
 
         return retval;
 }
 
 /**
  * sys_sched_setscheduler - set/change the scheduler policy and RT priority
  * @pid: the pid in question.
  * @policy: new policy.
  * @param: structure containing the new RT priority.
  */
 asmlinkage long
 sys_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
 {
         /* negative values for policy are not valid */
         if (policy < 0)
                 return -EINVAL;
 
         return do_sched_setscheduler(pid, policy, param);
 }
 
 /**
  * sys_sched_setparam - set/change the RT priority of a thread
  * @pid: the pid in question.
  * @param: structure containing the new RT priority.
  */
 asmlinkage long sys_sched_setparam(pid_t pid, struct sched_param __user *param)
 {
         return do_sched_setscheduler(pid, -1, param);
 }
 
 /**
  * sys_sched_getscheduler - get the policy (scheduling class) of a thread
  * @pid: the pid in question.
  */
 asmlinkage long sys_sched_getscheduler(pid_t pid)
 {
         struct task_struct *p;
         int retval;
 
         if (pid < 0)
                 return -EINVAL;
 
         retval = -ESRCH;
         read_lock(&tasklist_lock);
         p = find_process_by_pid(pid);
         if (p) {
                 retval = security_task_getscheduler(p);
                 if (!retval)
                         retval = p->policy;
         }
         read_unlock(&tasklist_lock);
         return retval;
 }
 
 /**
  * sys_sched_getscheduler - get the RT priority of a thread
  * @pid: the pid in question.
  * @param: structure containing the RT priority.
  */
 asmlinkage long sys_sched_getparam(pid_t pid, struct sched_param __user *param)
 {
         struct sched_param lp;
         struct task_struct *p;
         int retval;
 
         if (!param || pid < 0)
                 return -EINVAL;
 
         read_lock(&tasklist_lock);
         p = find_process_by_pid(pid);
         retval = -ESRCH;
         if (!p)
                 goto out_unlock;
 
         retval = security_task_getscheduler(p);
         if (retval)
                 goto out_unlock;
 
         lp.sched_priority = p->rt_priority;
         read_unlock(&tasklist_lock);
 
         /*
          * This one might sleep, we cannot do it with a spinlock held ...
          */
         retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
 
         return retval;
 
 out_unlock:
         read_unlock(&tasklist_lock);
         return retval;
 }
 
 long sched_setaffinity(pid_t pid, cpumask_t new_mask)
 {
         cpumask_t cpus_allowed;
         struct task_struct *p;
         int retval;
 
         get_online_cpus();
         read_lock(&tasklist_lock);
 
         p = find_process_by_pid(pid);
         if (!p) {
                 read_unlock(&tasklist_lock);
                 put_online_cpus();
                 return -ESRCH;
         }
 
         /*
          * It is not safe to call set_cpus_allowed with the
          * tasklist_lock held. We will bump the task_struct's
          * usage count and then drop tasklist_lock.
          */
         get_task_struct(p);
         read_unlock(&tasklist_lock);
 
         retval = -EPERM;
         if ((current->euid != p->euid) && (current->euid != p->uid) &&
                         !capable(CAP_SYS_NICE))
                 goto out_unlock;
 
         retval = security_task_setscheduler(p, 0, NULL);
         if (retval)
                 goto out_unlock;
 
         cpus_allowed = cpuset_cpus_allowed(p);
         cpus_and(new_mask, new_mask, cpus_allowed);
  again:
         retval = set_cpus_allowed(p, new_mask);
 
         if (!retval) {
                 cpus_allowed = cpuset_cpus_allowed(p);
                 if (!cpus_subset(new_mask, cpus_allowed)) {
                         /*
                          * We must have raced with a concurrent cpuset
                          * update. Just reset the cpus_allowed to the
                          * cpuset's cpus_allowed
                          */
                         new_mask = cpus_allowed;
                         goto again;
                 }
         }
 out_unlock:
         put_task_struct(p);
         put_online_cpus();
         return retval;
 }
 
 static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
                              cpumask_t *new_mask)
 {
         if (len < sizeof(cpumask_t)) {
                 memset(new_mask, 0, sizeof(cpumask_t));
         } else if (len > sizeof(cpumask_t)) {
                 len = sizeof(cpumask_t);
         }
         return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
 }
 
 /**
  * sys_sched_setaffinity - set the cpu affinity of a process
  * @pid: pid of the process
  * @len: length in bytes of the bitmask pointed to by user_mask_ptr
  * @user_mask_ptr: user-space pointer to the new cpu mask
  */
 asmlinkage long sys_sched_setaffinity(pid_t pid, unsigned int len,
                                       unsigned long __user *user_mask_ptr)
 {
         cpumask_t new_mask;
         int retval;
 
         retval = get_user_cpu_mask(user_mask_ptr, len, &new_mask);
         if (retval)
                 return retval;
 
         return sched_setaffinity(pid, new_mask);
 }
 
 /*
  * Represents all cpu's present in the system
  * In systems capable of hotplug, this map could dynamically grow
  * as new cpu's are detected in the system via any platform specific
  * method, such as ACPI for e.g.
  */
 
 cpumask_t cpu_present_map __read_mostly;
 EXPORT_SYMBOL(cpu_present_map);
 
 #ifndef CONFIG_SMP
 cpumask_t cpu_online_map __read_mostly = CPU_MASK_ALL;
 EXPORT_SYMBOL(cpu_online_map);
 
 cpumask_t cpu_possible_map __read_mostly = CPU_MASK_ALL;
 EXPORT_SYMBOL(cpu_possible_map);
 #endif
 
 long sched_getaffinity(pid_t pid, cpumask_t *mask)
 {
         struct task_struct *p;
         int retval;
 
         get_online_cpus();
         read_lock(&tasklist_lock);
 
         retval = -ESRCH;
         p = find_process_by_pid(pid);
         if (!p)
                 goto out_unlock;
 
         retval = security_task_getscheduler(p);
         if (retval)
                 goto out_unlock;
 
         cpus_and(*mask, p->cpus_allowed, cpu_online_map);
 
 out_unlock:
         read_unlock(&tasklist_lock);
         put_online_cpus();
 
         return retval;
 }
 
 /**
  * sys_sched_getaffinity - get the cpu affinity of a process
  * @pid: pid of the process
  * @len: length in bytes of the bitmask pointed to by user_mask_ptr
  * @user_mask_ptr: user-space pointer to hold the current cpu mask
  */
 asmlinkage long sys_sched_getaffinity(pid_t pid, unsigned int len,
                                       unsigned long __user *user_mask_ptr)
 {
         int ret;
         cpumask_t mask;
 
         if (len < sizeof(cpumask_t))
                 return -EINVAL;
 
         ret = sched_getaffinity(pid, &mask);
         if (ret < 0)
                 return ret;
 
         if (copy_to_user(user_mask_ptr, &mask, sizeof(cpumask_t)))
                 return -EFAULT;
 
         return sizeof(cpumask_t);
 }
 
 /**
  * sys_sched_yield - yield the current processor to other threads.
  *
  * This function yields the current CPU to other tasks. If there are no
  * other threads running on this CPU then this function will return.
  */
 asmlinkage long sys_sched_yield(void)
 {
         struct rq *rq = this_rq_lock();
 
         schedstat_inc(rq, yld_count);
         current->sched_class->yield_task(rq);
 
         /*
          * Since we are going to call schedule() anyway, there's
          * no need to preempt or enable interrupts:
          */
         spin_unlock_no_resched(&rq->lock);
 
         __schedule();
 
         local_irq_enable();
         preempt_check_resched();
 
         return 0;
 }
 
 static void __cond_resched(void)
 {
 #if defined(CONFIG_DEBUG_SPINLOCK_SLEEP) || defined(CONFIG_DEBUG_PREEMPT)
         __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 {
                 local_irq_disable();
                 add_preempt_count(PREEMPT_ACTIVE);
                 __schedule();
         } while (need_resched());
         local_irq_enable();
 }
 
 #if !defined(CONFIG_PREEMPT) || defined(CONFIG_PREEMPT_VOLUNTARY)
 int __sched _cond_resched(void)
 {
         if (need_resched() && !(preempt_count() & PREEMPT_ACTIVE) &&
                                         system_state == SYSTEM_RUNNING) {
                 __cond_resched();
                 return 1;
         }
         return 0;
 }
 EXPORT_SYMBOL(_cond_resched);
 #endif
 
 /*
  * cond_resched_lock() - if a reschedule is pending, drop the given lock,
  * call schedule, and on return reacquire the lock.
  *
  * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
  * operations here to prevent schedule() from being called twice (once via
  * spin_unlock(), once by hand).
  */
 int __cond_resched_raw_spinlock(raw_spinlock_t *lock)
 {
         int resched = need_resched() && system_state == SYSTEM_RUNNING;
         int ret = 0;
 
         if (spin_needbreak(lock) || resched) {
                 spin_unlock_no_resched(lock);
                 if (resched && need_resched())
                         __cond_resched();
                 else
                         cpu_relax();
                 ret = 1;
                 spin_lock(lock);
         }
         return ret;
 }
 EXPORT_SYMBOL(__cond_resched_raw_spinlock);
 
 #ifdef CONFIG_PREEMPT_RT
 
 int __cond_resched_spinlock(spinlock_t *lock)
 {
 #if (defined(CONFIG_SMP) && defined(CONFIG_PREEMPT)) || defined(CONFIG_PREEMPT_RT)
         if (lock->break_lock) {
                 lock->break_lock = 0;
                 spin_unlock_no_resched(lock);
                 __cond_resched();
                 spin_lock(lock);
                 return 1;
         }
 #endif
         return 0;
 }
 EXPORT_SYMBOL(__cond_resched_spinlock);
 
 #endif
 
 /*
  * Voluntarily preempt a process context that has softirqs disabled:
  */
 int __sched cond_resched_softirq(void)
 {
 #ifndef CONFIG_PREEMPT_SOFTIRQS
         WARN_ON_ONCE(!in_softirq());
 #endif
         if (need_resched() && system_state == SYSTEM_RUNNING) {
                 local_bh_enable();
                 __cond_resched();
                 local_bh_disable();
                 return 1;
         }
         return 0;
 }
 EXPORT_SYMBOL(cond_resched_softirq);
 
 /*
  * Voluntarily preempt a softirq context (possible with softirq threading):
  */
 int __sched cond_resched_softirq_context(void)
 {
         WARN_ON_ONCE(!in_softirq());
 
         if (softirq_need_resched() && system_state == SYSTEM_RUNNING) {
                 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_context);
 
 /*
  * Preempt a hardirq context if necessary (possible with hardirq threading):
  */
 int cond_resched_hardirq_context(void)
 {
         WARN_ON_ONCE(!in_irq());
         WARN_ON_ONCE(!irqs_disabled());
 
         if (hardirq_need_resched()) {
 #ifndef CONFIG_PREEMPT_RT
                 irq_exit();
 #endif
                 local_irq_enable();
                 __cond_resched();
 #ifndef CONFIG_PREEMPT_RT
                 local_irq_disable();
                 __irq_enter();
 #endif
 
                 return 1;
         }
         return 0;
 }
 EXPORT_SYMBOL(cond_resched_hardirq_context);
 
 #ifdef CONFIG_PREEMPT_VOLUNTARY
 
 int voluntary_preemption = 1;
 
 EXPORT_SYMBOL(voluntary_preemption);
 
 static int __init voluntary_preempt_setup (char *str)
 {
         if (!strncmp(str, "off", 3))
                 voluntary_preemption = 0;
         else
                 get_option(&str, &voluntary_preemption);
         if (!voluntary_preemption)
                 printk("turning off voluntary preemption!\n");
 
         return 1;
 }
 
 __setup("voluntary-preempt=", voluntary_preempt_setup);
 
 #endif
 
 /**
  * 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();
 }
 
 void __sched yield(void)
 {
         static int once = 1;
 
         /*
          * it's a bug to rely on yield() with RT priorities. We print
          * the first occurance after bootup ... this will still give
          * us an idea about the scope of the problem, without spamming
          * the syslog:
          */
         if (once && rt_task(current)) {
                 once = 0;
                 printk(KERN_ERR "BUG: %s:%d RT task yield()-ing!\n",
                         current->comm, current->pid);
                 dump_stack();
         }
         __yield();
 }
 EXPORT_SYMBOL(yield);
 
 /*
  * This task is about to go to sleep on IO. Increment rq->nr_iowait so
  * that process accounting knows that this is a task in IO wait state.
  *
  * But don't do that if it is a deliberate, throttling IO wait (this task
  * has set its backing_dev_info: the queue against which it should throttle)
  */
 void __sched io_schedule(void)
 {
         struct rq *rq = &__raw_get_cpu_var(runqueues);
 
         delayacct_blkio_start();
         atomic_inc(&rq->nr_iowait);
         schedule();
         atomic_dec(&rq->nr_iowait);
         delayacct_blkio_end();
 }
 EXPORT_SYMBOL(io_schedule);
 
 long __sched io_schedule_timeout(long timeout)
 {
         struct rq *rq = &__raw_get_cpu_var(runqueues);
         long ret;
 
         delayacct_blkio_start();
         atomic_inc(&rq->nr_iowait);
         ret = schedule_timeout(timeout);
         atomic_dec(&rq->nr_iowait);
         delayacct_blkio_end();
         return ret;
 }
 
 /**
  * sys_sched_get_priority_max - return maximum RT priority.
  * @policy: scheduling class.
  *
  * this syscall returns the maximum rt_priority that can be used
  * by a given scheduling class.
  */
 asmlinkage long sys_sched_get_priority_max(int policy)
 {
         int ret = -EINVAL;
 
         switch (policy) {
         case SCHED_FIFO:
         case SCHED_RR:
                 ret = MAX_USER_RT_PRIO-1;
                 break;
         case SCHED_NORMAL:
         case SCHED_BATCH:
         case SCHED_IDLE:
                 ret = 0;
                 break;
         }
         return ret;
 }
 
 /**
  * sys_sched_get_priority_min - return minimum RT priority.
  * @policy: scheduling class.
  *
  * this syscall returns the minimum rt_priority that can be used
  * by a given scheduling class.
  */
 asmlinkage long sys_sched_get_priority_min(int policy)
 {
         int ret = -EINVAL;
 
         switch (policy) {
         case SCHED_FIFO:
         case SCHED_RR:
                 ret = 1;
                 break;
         case SCHED_NORMAL:
         case SCHED_BATCH:
         case SCHED_IDLE:
                 ret = 0;
         }
         return ret;
 }
 
 /**
  * sys_sched_rr_get_interval - return the default timeslice of a process.
  * @pid: pid of the process.
  * @interval: userspace pointer to the timeslice value.
  *
  * this syscall writes the default timeslice value of a given process
  * into the user-space timespec buffer. A value of '' means infinity.
  */
 asmlinkage
 long sys_sched_rr_get_interval(pid_t pid, struct timespec __user *interval)
 {
         struct task_struct *p;
         unsigned int time_slice;
         int retval;
         struct timespec t;
 
         if (pid < 0)
                 return -EINVAL;
 
         retval = -ESRCH;
         read_lock(&tasklist_lock);
         p = find_process_by_pid(pid);
         if (!p)
                 goto out_unlock;
 
         retval = security_task_getscheduler(p);
         if (retval)
                 goto out_unlock;
 
         /*
          * Time slice is 0 for SCHED_FIFO tasks and for SCHED_OTHER
          * tasks that are on an otherwise idle runqueue:
          */
         time_slice = 0;
         if (p->policy == SCHED_RR) {
                 time_slice = DEF_TIMESLICE;
         } else if (p->policy != SCHED_FIFO) {
                 struct sched_entity *se = &p->se;
                 unsigned long flags;
                 struct rq *rq;
 
                 rq = task_rq_lock(p, &flags);
                 if (rq->cfs.load.weight)
                         time_slice = NS_TO_JIFFIES(sched_slice(&rq->cfs, se));
                 task_rq_unlock(rq, &flags);
         }
         read_unlock(&tasklist_lock);
         jiffies_to_timespec(time_slice, &t);
         retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
         return retval;
 
 out_unlock:
         read_unlock(&tasklist_lock);
         return retval;
 }
 
 static const char stat_nam[] = TASK_STATE_TO_CHAR_STR;
 
 void sched_show_task(struct task_struct *p)
 {
         unsigned long free = 0;
         unsigned state;
 
         state = p->state ? __ffs(p->state) + 1 : 0;
         printk("%-13.13s %c [%p]", p->comm,
                 state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?', p);
 #if BITS_PER_LONG == 32
         if (0 && (state == TASK_RUNNING))
                 printk(KERN_CONT " running  ");
         else
                 printk(KERN_CONT " %08lx ", thread_saved_pc(p));
 #else
         if (0 && (state == TASK_RUNNING))
                 printk(KERN_CONT "  running task    ");
         else
                 printk(KERN_CONT " %016lx ", thread_saved_pc(p));
 #endif
         if (task_curr(p))
                 printk("[curr] ");
         else if (p->se.on_rq)
                 printk("[on rq #%d] ", task_cpu(p));
 #ifdef CONFIG_DEBUG_STACK_USAGE
         {
                 unsigned long *n = end_of_stack(p);
                 while (!*n)
                         n++;
                 free = (unsigned long)n - (unsigned long)end_of_stack(p);
         }
 #endif
         printk(KERN_CONT "%5lu %5d %6d\n", free,
                 task_pid_nr(p), task_pid_nr(p->real_parent));
 
         show_stack(p, NULL);
 }
 
 void show_state_filter(unsigned long state_filter)
 {
         struct task_struct *g, *p;
         int do_unlock = 1;
 
 #if BITS_PER_LONG == 32
         printk(KERN_INFO
                 "  task                PC stack   pid father\n");
 #else
         printk(KERN_INFO
                 "  task                        PC stack   pid father\n");
 #endif
 #ifdef CONFIG_PREEMPT_RT
         if (!read_trylock(&tasklist_lock)) {
                 printk("hm, tasklist_lock write-locked.\n");
                 printk("ignoring ...\n");
                 do_unlock = 0;
         }
 #else
         read_lock(&tasklist_lock);
 #endif
 
         do_each_thread(g, p) {
                 /*
                  * reset the NMI-timeout, listing all files on a slow
                  * console might take alot of time:
                  */
                 touch_nmi_watchdog();
                 if (!state_filter || (p->state & state_filter))
                         sched_show_task(p);
         } while_each_thread(g, p);
 
         touch_all_softlockup_watchdogs();
 
 #ifdef CONFIG_SCHED_DEBUG
         sysrq_sched_debug_show();
 #endif
         if (do_unlock)
                 read_unlock(&tasklist_lock);
         /*
          * Only show locks if all tasks are dumped:
          */
         if (state_filter == -1)
                 debug_show_all_locks();
 }
 
 void __cpuinit init_idle_bootup_task(struct task_struct *idle)
 {
         idle->sched_class = &idle_sched_class;
 }
 
 /**
  * init_idle - set up an idle thread for a given CPU
  * @idle: task in question
  * @cpu: cpu the idle task belongs to
  *
  * NOTE: this function does not set the idle thread's NEED_RESCHED
  * flag, to make booting more robust.
  */
 void __cpuinit init_idle(struct task_struct *idle, int cpu)
 {
         struct rq *rq = cpu_rq(cpu);
         unsigned long flags;
 
         __sched_fork(idle);
         idle->se.exec_start = sched_clock();
 
         idle->prio = idle->normal_prio = MAX_PRIO;
         idle->cpus_allowed = cpumask_of_cpu(cpu);
         __set_task_cpu(idle, cpu);
 
         spin_lock_irqsave(&rq->lock, flags);
         rq->curr = rq->idle = idle;
 #if defined(CONFIG_SMP)
         idle->oncpu = 1;
 #endif
         spin_unlock_irqrestore(&rq->lock, flags);
 
         /* Set the preempt count _outside_ the spinlocks! */
         task_thread_info(idle)->preempt_count = 0;
 
         /*
          * The idle tasks have their own, simple scheduling class:
          */
         idle->sched_class = &idle_sched_class;
 }
 
 /*
  * In a system that switches off the HZ timer nohz_cpu_mask
  * indicates which cpus entered this state. This is used
  * in the rcu update to wait only for active cpus. For system
  * which do not switch off the HZ timer nohz_cpu_mask should
  * always be CPU_MASK_NONE.
  */
 cpumask_t nohz_cpu_mask = CPU_MASK_NONE;
 
 /*
  * Increase the granularity value when there are more CPUs,
  * because with more CPUs the 'effective latency' as visible
  * to users decreases. But the relationship is not linear,
  * so pick a second-best guess by going with the log2 of the
  * number of CPUs.
  *
  * This idea comes from the SD scheduler of Con Kolivas:
  */
 static inline void sched_init_granularity(void)
 {
         unsigned int factor = 1 + ilog2(num_online_cpus());
         const unsigned long limit = 200000000;
 
         sysctl_sched_min_granularity *= factor;
         if (sysctl_sched_min_granularity > limit)
                 sysctl_sched_min_granularity = limit;
 
         sysctl_sched_latency *= factor;
         if (sysctl_sched_latency > limit)
                 sysctl_sched_latency = limit;
 
         sysctl_sched_wakeup_granularity *= factor;
         sysctl_sched_batch_wakeup_granularity *= factor;
 }
 
 #ifdef CONFIG_SMP
 /*
  * This is how migration works:
  *
  * 1) we queue a struct migration_req structure in the source CPU's
  *    runqueue and wake up that CPU's migration thread.
  * 2) we down() the locked semaphore => thread blocks.
  * 3) migration thread wakes up (implicitly it forces the migrated
  *    thread off the CPU)
  * 4) it gets the migration request and checks whether the migrated
  *    task is still in the wrong runqueue.
  * 5) if it's in the wrong runqueue then the migration thread removes
  *    it and puts it into the right queue.
  * 6) migration thread up()s the semaphore.
  * 7) we wake up and the migration is done.
  */
 
 /*
  * Change a given task's CPU affinity. Migrate the thread to a
  * proper CPU and schedule it away if the CPU it's executing on
  * is removed from the allowed bitmask.
  *
  * NOTE: the caller must have a valid reference to the task, the
  * task must not exit() & deallocate itself prematurely. The
  * call is not atomic; no spinlocks may be held.
  */
 int set_cpus_allowed(struct task_struct *p, cpumask_t new_mask)
 {
         struct migration_req req;
         unsigned long flags;
         struct rq *rq;
         int ret = 0;
 
         rq = task_rq_lock(p, &flags);
         if (!cpus_intersects(new_mask, cpu_online_map)) {
                 ret = -EINVAL;
                 goto out;
         }
 
         if (p->sched_class->set_cpus_allowed)
                 p->sched_class->set_cpus_allowed(p, &new_mask);
         else {
                 p->cpus_allowed = new_mask;
                 p->rt.nr_cpus_allowed = cpus_weight(new_mask);
         }
 
         /* Can the task run on the task's current CPU? If so, we're done */
         if (cpu_isset(task_cpu(p), new_mask))
                 goto out;
 
         if (migrate_task(p, any_online_cpu(new_mask), &req)) {
                 /* Need help from migration thread: drop lock and wait. */
                 task_rq_unlock(rq, &flags);
                 wake_up_process(rq->migration_thread);
                 wait_for_completion(&req.done);
                 tlb_migrate_finish(p->mm);
                 return 0;
         }
 out:
         task_rq_unlock(rq, &flags);
 
         return ret;
 }
 EXPORT_SYMBOL_GPL(set_cpus_allowed);
 
 /*
  * Move (not current) task off this cpu, onto dest cpu. We're doing
  * this because either it can't run here any more (set_cpus_allowed()
  * away from this CPU, or CPU going down), or because we're
  * attempting to rebalance this task on exec (sched_exec).
  *
  * So we race with normal scheduler movements, but that's OK, as long
  * as the task is no longer on this CPU.
  *
  * Returns non-zero if task was successfully migrated.
  */
 static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
 {
         struct rq *rq_dest, *rq_src;
         unsigned long flags;
         int ret = 0, on_rq;
 
         if (unlikely(cpu_is_offline(dest_cpu)))
                 return ret;
 
         /*
          * PREEMPT_RT: this relies on write_lock_irq(&tasklist_lock)
          * disabling interrupts - which on PREEMPT_RT does not do:
          */
         local_irq_save(flags);
 
         rq_src = cpu_rq(src_cpu);
         rq_dest = cpu_rq(dest_cpu);
 
         double_rq_lock(rq_src, rq_dest);
         /* Already moved. */
         if (task_cpu(p) != src_cpu)
                 goto out;
         /* Affinity changed (again). */
         if (!cpu_isset(dest_cpu, p->cpus_allowed))
                 goto out;
 
         on_rq = p->se.on_rq;
         if (on_rq)
                 deactivate_task(rq_src, p, 0);
 
         set_task_cpu(p, dest_cpu);
         if (on_rq) {
                 activate_task(rq_dest, p, 0);
                 check_preempt_curr(rq_dest, p);
         }
         ret = 1;
 out:
         double_rq_unlock(rq_src, rq_dest);
         local_irq_restore(flags);
 
         return ret;
 }
 
 /*
  * migration_thread - this is a highprio system thread that performs
  * thread migration by bumping thread off CPU then 'pushing' onto
  * another runqueue.
  */
 static int migration_thread(void *data)
 {
         int cpu = (long)data;
         struct rq *rq;
 
         rq = cpu_rq(cpu);
         BUG_ON(rq->migration_thread != current);
 
         set_current_state(TASK_INTERRUPTIBLE);
         while (!kthread_should_stop()) {
                 struct migration_req *req;
                 struct list_head *head;
 
                 spin_lock_irq(&rq->lock);
 
                 if (cpu_is_offline(cpu)) {
                         spin_unlock_irq(&rq->lock);
                         goto wait_to_die;
                 }
 
                 if (rq->active_balance) {
                         active_load_balance(rq, cpu);
                         rq->active_balance = 0;
                 }
 
                 head = &rq->migration_queue;
 
                 if (list_empty(head)) {
                         spin_unlock_irq(&rq->lock);
                         schedule();
                         set_current_state(TASK_INTERRUPTIBLE);
                         continue;
                 }
                 req = list_entry(head->next, struct migration_req, list);
                 list_del_init(head->next);
 
                 spin_unlock(&rq->lock);
                 __migrate_task(req->task, cpu, req->dest_cpu);
                 local_irq_enable();
 
                 complete(&req->done);
         }
         __set_current_state(TASK_RUNNING);
         return 0;
 
 wait_to_die:
         /* Wait for kthread_stop */
         set_current_state(TASK_INTERRUPTIBLE);
         while (!kthread_should_stop()) {
                 schedule();
                 set_current_state(TASK_INTERRUPTIBLE);
         }
         __set_current_state(TASK_RUNNING);
         return 0;
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
 
 static int __migrate_task_irq(struct task_struct *p, int src_cpu, int dest_cpu)
 {
         int ret;
 
         local_irq_disable();
         ret = __migrate_task(p, src_cpu, dest_cpu);
         local_irq_enable();
         return ret;
 }
 
 /*
  * Figure out where task on dead CPU should go, use force if necessary.
  * NOTE: interrupts should be disabled by the caller
  */
 static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
 {
         unsigned long flags;
         cpumask_t mask;
         struct rq *rq;
         int dest_cpu;
 
         do {
                 /* On same node? */
                 mask = node_to_cpumask(cpu_to_node(dead_cpu));
                 cpus_and(mask, mask, p->cpus_allowed);
                 dest_cpu = any_online_cpu(mask);
 
                 /* On any allowed CPU? */
                 if (dest_cpu == NR_CPUS)
                         dest_cpu = any_online_cpu(p->cpus_allowed);
 
                 /* No more Mr. Nice Guy. */
                 if (dest_cpu == NR_CPUS) {
                         cpumask_t cpus_allowed = cpuset_cpus_allowed_locked(p);
                         /*
                          * Try to stay on the same cpuset, where the
                          * current cpuset may be a subset of all cpus.
                          * The cpuset_cpus_allowed_locked() variant of
                          * cpuset_cpus_allowed() will not block. It must be
                          * called within calls to cpuset_lock/cpuset_unlock.
                          */
                         rq = task_rq_lock(p, &flags);
                         p->cpus_allowed = cpus_allowed;
                         dest_cpu = any_online_cpu(p->cpus_allowed);
                         task_rq_unlock(rq, &flags);
 
                         /*
                          * Don't tell them about moving exiting tasks or
                          * kernel threads (both mm NULL), since they never
                          * leave kernel.
                          */
                         if (p->mm && printk_ratelimit()) {
                                 printk(KERN_INFO "process %d (%s) no "
                                        "longer affine to cpu%d\n",
                                         task_pid_nr(p), p->comm, dead_cpu);
                         }
                 }
         } while (!__migrate_task_irq(p, dead_cpu, dest_cpu));
 }
 
 /*
  * While a dead CPU has no uninterruptible tasks queued at this point,
  * it might still have a nonzero ->nr_uninterruptible counter, because
  * for performance reasons the counter is not stricly tracking tasks to
  * their home CPUs. So we just add the counter to another CPU's counter,
  * to keep the global sum constant after CPU-down:
  */
 static void migrate_nr_uninterruptible(struct rq *rq_src)
 {
         struct rq *rq_dest = cpu_rq(any_online_cpu(CPU_MASK_ALL));
         unsigned long flags;
 
         local_irq_save(flags);
         double_rq_lock(rq_src, rq_dest);
         rq_dest->nr_uninterruptible += rq_src->nr_uninterruptible;
         rq_src->nr_uninterruptible = 0;
         double_rq_unlock(rq_src, rq_dest);
         local_irq_restore(flags);
 }
 
 /* Run through task list and migrate tasks from the dead cpu. */
 static void migrate_live_tasks(int src_cpu)
 {
         struct task_struct *p, *t;
 
         read_lock(&tasklist_lock);
 
         do_each_thread(t, p) {
                 if (p == current)
                         continue;
 
                 if (task_cpu(p) == src_cpu)
                         move_task_off_dead_cpu(src_cpu, p);
         } while_each_thread(t, p);
 
         read_unlock(&tasklist_lock);
 }
 
 /*
  * Schedules idle task to be the next runnable task on current CPU.
  * It does so by boosting its priority to highest possible.
  * Used by CPU offline code.
  */
 void sched_idle_next(void)
 {
         int this_cpu = smp_processor_id();
         struct rq *rq = cpu_rq(this_cpu);
         struct task_struct *p = rq->idle;
         unsigned long flags;
 
         /* cpu has to be offline */
         BUG_ON(cpu_online(this_cpu));
 
         /*
          * Strictly not necessary since rest of the CPUs are stopped by now
          * and interrupts disabled on the current cpu.
          */
         spin_lock_irqsave(&rq->lock, flags);
 
         __setscheduler(rq, p, SCHED_FIFO, MAX_RT_PRIO-1);
 
         update_rq_clock(rq);
         activate_task(rq, p, 0);
 
         spin_unlock_irqrestore(&rq->lock, flags);
 }
 
 /*
  * Ensures that the idle task is using init_mm right before its cpu goes
  * offline.
  */
 void idle_task_exit(void)
 {
         struct mm_struct *mm = current->active_mm;
 
         BUG_ON(cpu_online(smp_processor_id()));
 
         if (mm != &init_mm)
                 switch_mm(mm, &init_mm, current);
         mmdrop(mm);
 }
 
 /* called under rq->lock with disabled interrupts */
 static void migrate_dead(unsigned int dead_cpu, struct task_struct *p)
 {
         struct rq *rq = cpu_rq(dead_cpu);
 
         /* Must be exiting, otherwise would be on tasklist. */
         BUG_ON(!p->exit_state);
 
         /* Cannot have done final schedule yet: would have vanished. */
         BUG_ON(p->state == TASK_DEAD);
 
         get_task_struct(p);
 
         /*
          * Drop lock around migration; if someone else moves it,
          * that's OK. No task can be added to this CPU, so iteration is
          * fine.
          */
         spin_unlock_irq(&rq->lock);
         move_task_off_dead_cpu(dead_cpu, p);
         spin_lock_irq(&rq->lock);
 
         put_task_struct(p);
 }
 
 /* release_task() removes task from tasklist, so we won't find dead tasks. */
 static void migrate_dead_tasks(unsigned int dead_cpu)
 {
         struct rq *rq = cpu_rq(dead_cpu);
         struct task_struct *next;
 
         for ( ; ; ) {
                 if (!rq->nr_running)
                         break;
                 update_rq_clock(rq);
                 next = pick_next_task(rq, rq->curr);
                 if (!next)
                         break;
                 migrate_dead(dead_cpu, next);
 
         }
 }
 #endif /* CONFIG_HOTPLUG_CPU */
 
 #if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_SYSCTL)
 
 static struct ctl_table sd_ctl_dir[] = {
         {
                 .procname       = "sched_domain",
                 .mode           = 0555,
         },
         {0, },
 };
 
 static struct ctl_table sd_ctl_root[] = {
         {
                 .ctl_name       = CTL_KERN,
                 .procname       = "kernel",
                 .mode           = 0555,
                 .child          = sd_ctl_dir,
         },
         {0, },
 };
 
 static struct ctl_table *sd_alloc_ctl_entry(int n)
 {
         struct ctl_table *entry =
                 kcalloc(n, sizeof(struct ctl_table), GFP_KERNEL);
 
         return entry;
 }
 
 static void sd_free_ctl_entry(struct ctl_table **tablep)
 {
         struct ctl_table *entry;
 
         /*
          * In the intermediate directories, both the child directory and
          * procname are dynamically allocated and could fail but the mode
          * will always be set. In the lowest directory the names are
          * static strings and all have proc handlers.
          */
         for (entry = *tablep; entry->mode; entry++) {
                 if (entry->child)
                         sd_free_ctl_entry(&entry->child);
                 if (entry->proc_handler == NULL)
                         kfree(entry->procname);
         }
 
         kfree(*tablep);
         *tablep = NULL;
 }
 
 static void
 set_table_entry(struct ctl_table *entry,
                 const char *procname, void *data, int maxlen,
                 mode_t mode, proc_handler *proc_handler)
 {
         entry->procname = procname;
         entry->data = data;
         entry->maxlen = maxlen;
         entry->mode = mode;
         entry->proc_handler = proc_handler;
 }
 
 static struct ctl_table *
 sd_alloc_ctl_domain_table(struct sched_domain *sd)
 {
         struct ctl_table *table = sd_alloc_ctl_entry(12);
 
         if (table == NULL)
                 return NULL;
 
         set_table_entry(&table[0], "min_interval", &sd->min_interval,
                 sizeof(long), 0644, proc_doulongvec_minmax);
         set_table_entry(&table[1], "max_interval", &sd->max_interval,
                 sizeof(long), 0644, proc_doulongvec_minmax);
         set_table_entry(&table[2], "busy_idx", &sd->busy_idx,
                 sizeof(int), 0644, proc_dointvec_minmax);
         set_table_entry(&table[3], "idle_idx", &sd->idle_idx,
                 sizeof(int), 0644, proc_dointvec_minmax);
         set_table_entry(&table[4], "newidle_idx", &sd->newidle_idx,
                 sizeof(int), 0644, proc_dointvec_minmax);
         set_table_entry(&table[5], "wake_idx", &sd->wake_idx,
                 sizeof(int), 0644, proc_dointvec_minmax);
         set_table_entry(&table[6], "forkexec_idx", &sd->forkexec_idx,
                 sizeof(int), 0644, proc_dointvec_minmax);
         set_table_entry(&table[7], "busy_factor", &sd->busy_factor,
                 sizeof(int), 0644, proc_dointvec_minmax);
         set_table_entry(&table[8], "imbalance_pct", &sd->imbalance_pct,
                 sizeof(int), 0644, proc_dointvec_minmax);
         set_table_entry(&table[9], "cache_nice_tries",
                 &sd->cache_nice_tries,
                 sizeof(int), 0644, proc_dointvec_minmax);
         set_table_entry(&table[10], "flags", &sd->flags,
                 sizeof(int), 0644, proc_dointvec_minmax);
         /* &table[11] is terminator */
 
         return table;
 }
 
 static ctl_table *sd_alloc_ctl_cpu_table(int cpu)
 {
         struct ctl_table *entry, *table;
         struct sched_domain *sd;
         int domain_num = 0, i;
         char buf[32];
 
         for_each_domain(cpu, sd)
                 domain_num++;
         entry = table = sd_alloc_ctl_entry(domain_num + 1);
         if (table == NULL)
                 return NULL;
 
         i = 0;
         for_each_domain(cpu, sd) {
                 snprintf(buf, 32, "domain%d", i);
                 entry->procname = kstrdup(buf, GFP_KERNEL);
                 entry->mode = 0555;
                 entry->child = sd_alloc_ctl_domain_table(sd);
                 entry++;
                 i++;
         }
         return table;
 }
 
 static struct ctl_table_header *sd_sysctl_header;
 static void register_sched_domain_sysctl(void)
 {
         int i, cpu_num = num_online_cpus();
         struct ctl_table *entry = sd_alloc_ctl_entry(cpu_num + 1);
         char buf[32];
 
         WARN_ON(sd_ctl_dir[0].child);
         sd_ctl_dir[0].child = entry;
 
         if (entry == NULL)
                 return;
 
         for_each_online_cpu(i) {
                 snprintf(buf, 32, "cpu%d", i);
                 entry->procname = kstrdup(buf, GFP_KERNEL);
                 entry->mode = 0555;
                 entry->child = sd_alloc_ctl_cpu_table(i);
                 entry++;
         }
 
         WARN_ON(sd_sysctl_header);
         sd_sysctl_header = register_sysctl_table(sd_ctl_root);
 }
 
 /* may be called multiple times per register */
 static void unregister_sched_domain_sysctl(void)
 {
         if (sd_sysctl_header)
                 unregister_sysctl_table(sd_sysctl_header);
         sd_sysctl_header = NULL;
         if (sd_ctl_dir[0].child)
                 sd_free_ctl_entry(&sd_ctl_dir[0].child);
 }
 #else
 static void register_sched_domain_sysctl(void)
 {
 }
 static void unregister_sched_domain_sysctl(void)
 {
 }
 #endif
 
 static void set_rq_online(struct rq *rq)
 {
         if (!rq->online) {
                 const struct sched_class *class;
 
                 cpu_set(rq->cpu, rq->rd->online);
                 rq->online = 1;
 
                 for_each_class(class) {
                         if (class->rq_online)
                                 class->rq_online(rq);
                 }
         }
 }
 
 static void set_rq_offline(struct rq *rq)
 {
         if (rq->online) {
                 const struct sched_class *class;
 
                 for_each_class(class) {
                         if (class->rq_offline)
                                 class->rq_offline(rq);
                 }
 
                 cpu_clear(rq->cpu, rq->rd->online);
                 rq->online = 0;
         }
 }
 
 /*
  * migration_call - callback that gets triggered when a CPU is added.
  * Here we can start up the necessary migration thread for the new CPU.
  */
 static int __cpuinit
 migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
 {
         struct task_struct *p;
         int cpu = (long)hcpu;
         unsigned long flags;
         struct rq *rq;
 
         switch (action) {
 
         case CPU_UP_PREPARE:
         case CPU_UP_PREPARE_FROZEN:
                 p = kthread_create(migration_thread, hcpu, "migration/%d", cpu);
                 if (IS_ERR(p))
                         return NOTIFY_BAD;
                 kthread_bind(p, cpu);
                 /* Must be high prio: stop_machine expects to yield to it. */
                 rq = task_rq_lock(p, &flags);
                 __setscheduler(rq, p, SCHED_FIFO, MAX_RT_PRIO-1);
                 task_rq_unlock(rq, &flags);
                 cpu_rq(cpu)->migration_thread = p;
                 break;
 
         case CPU_ONLINE:
         case CPU_ONLINE_FROZEN:
                 /* Strictly unnecessary, as first user will wake it. */
                 wake_up_process(cpu_rq(cpu)->migration_thread);
 
                 /* Update our root-domain */
                 rq = cpu_rq(cpu);
                 spin_lock_irqsave(&rq->lock, flags);
                 if (rq->rd) {
                         BUG_ON(!cpu_isset(cpu, rq->rd->span));
 
                         set_rq_online(rq);
                 }
                 spin_unlock_irqrestore(&rq->lock, flags);
                 break;
 
 #ifdef CONFIG_HOTPLUG_CPU
         case CPU_UP_CANCELED:
         case CPU_UP_CANCELED_FROZEN:
                 if (!cpu_rq(cpu)->migration_thread)
                         break;
                 /* Unbind it from offline cpu so it can run. Fall thru. */
                 kthread_bind(cpu_rq(cpu)->migration_thread,
                              any_online_cpu(cpu_online_map));
                 kthread_stop(cpu_rq(cpu)->migration_thread);
                 cpu_rq(cpu)->migration_thread = NULL;
                 break;
 
         case CPU_DEAD:
         case CPU_DEAD_FROZEN:
                 cpuset_lock(); /* around calls to cpuset_cpus_allowed_lock() */
                 migrate_live_tasks(cpu);
                 rq = cpu_rq(cpu);
                 kthread_stop(rq->migration_thread);
                 rq->migration_thread = NULL;
                 /* Idle task back to normal (off runqueue, low prio) */
                 spin_lock_irq(&rq->lock);
                 update_rq_clock(rq);
                 deactivate_task(rq, rq->idle, 0);
                 rq->idle->static_prio = MAX_PRIO;
                 __setscheduler(rq, rq->idle, SCHED_NORMAL, 0);
                 rq->idle->sched_class = &idle_sched_class;
                 migrate_dead_tasks(cpu);
                 spin_unlock_irq(&rq->lock);
                 cpuset_unlock();
                 migrate_nr_uninterruptible(rq);
                 BUG_ON(rq->nr_running != 0);
 
                 /*
                  * No need to migrate the tasks: it was best-effort if
                  * they didn't take sched_hotcpu_mutex. Just wake up
                  * the requestors.
                  */
                 spin_lock_irq(&rq->lock);
                 while (!list_empty(&rq->migration_queue)) {
                         struct migration_req *req;
 
                         req = list_entry(rq->migration_queue.next,
                                          struct migration_req, list);
                         list_del_init(&req->list);
                         complete(&req->done);
                 }
                 spin_unlock_irq(&rq->lock);
                 break;
 
         case CPU_DYING:
         case CPU_DYING_FROZEN:
                 /* Update our root-domain */
                 rq = cpu_rq(cpu);
                 spin_lock_irqsave(&rq->lock, flags);
                 if (rq->rd) {
                         BUG_ON(!cpu_isset(cpu, rq->rd->span));
                         set_rq_offline(rq);
                 }
                 spin_unlock_irqrestore(&rq->lock, flags);
                 break;
 #endif
         }
         return NOTIFY_OK;
 }
 
 /* Register at highest priority so that task migration (migrate_all_tasks)
  * happens before everything else.
  */
 static struct notifier_block __cpuinitdata migration_notifier = {
         .notifier_call = migration_call,
         .priority = 10
 };
 
 void __init migration_init(void)
 {
         void *cpu = (void *)(long)smp_processor_id();
         int err;
 
         /* Start one for the boot CPU: */
         err = migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
         BUG_ON(err == NOTIFY_BAD);
         migration_call(&migration_notifier, CPU_ONLINE, cpu);
         register_cpu_notifier(&migration_notifier);
 }
 #endif
 
 #ifdef CONFIG_SMP
 
 /* Number of possible processor ids */
 int nr_cpu_ids __read_mostly = NR_CPUS;
 EXPORT_SYMBOL(nr_cpu_ids);
 
 #ifdef CONFIG_SCHED_DEBUG
 
 static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level)
 {
         struct sched_group *group = sd->groups;
         cpumask_t groupmask;
         char str[NR_CPUS];
 
         cpumask_scnprintf(str, NR_CPUS, sd->span);
         cpus_clear(groupmask);
 
         printk(KERN_DEBUG "%*s domain %d: ", level, "", level);
 
         if (!(sd->flags & SD_LOAD_BALANCE)) {
                 printk("does not load-balance\n");
                 if (sd->parent)
                         printk(KERN_ERR "ERROR: !SD_LOAD_BALANCE domain"
                                         " has parent");
                 return -1;
         }
 
         printk(KERN_CONT "span %s\n", str);
 
         if (!cpu_isset(cpu, sd->span)) {
                 printk(KERN_ERR "ERROR: domain->span does not contain "
                                 "CPU%d\n", cpu);
         }
         if (!cpu_isset(cpu, group->cpumask)) {
                 printk(KERN_ERR "ERROR: domain->groups does not contain"
                                 " CPU%d\n", cpu);
         }
 
         printk(KERN_DEBUG "%*s groups:", level + 1, "");
         do {
                 if (!group) {
                         printk("\n");
                         printk(KERN_ERR "ERROR: group is NULL\n");
                         break;
                 }
 
                 if (!group->__cpu_power) {
                         printk(KERN_CONT "\n");
                         printk(KERN_ERR "ERROR: domain->cpu_power not "
                                         "set\n");
                         break;
                 }
 
                 if (!cpus_weight(group->cpumask)) {
                         printk(KERN_CONT "\n");
                         printk(KERN_ERR "ERROR: empty group\n");
                         break;
                 }
 
                 if (cpus_intersects(groupmask, group->cpumask)) {
                         printk(KERN_CONT "\n");
                         printk(KERN_ERR "ERROR: repeated CPUs\n");
                         break;
                 }
 
                 cpus_or(groupmask, groupmask, group->cpumask);
 
                 cpumask_scnprintf(str, NR_CPUS, group->cpumask);
                 printk(KERN_CONT " %s", str);
 
                 group = group->next;
         } while (group != sd->groups);
         printk(KERN_CONT "\n");
 
         if (!cpus_equal(sd->span, groupmask))
                 printk(KERN_ERR "ERROR: groups don't span domain->span\n");
 
         if (sd->parent && !cpus_subset(groupmask, sd->parent->span))
                 printk(KERN_ERR "ERROR: parent span is not a superset "
                         "of domain->span\n");
         return 0;
 }
 
 static void sched_domain_debug(struct sched_domain *sd, int cpu)
 {
         int level = 0;
 
         if (!sd) {
                 printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu);
                 return;
         }
 
         printk(KERN_DEBUG "CPU%d attaching sched-domain:\n", cpu);
 
         for (;;) {
                 if (sched_domain_debug_one(sd, cpu, level))
                         break;
                 level++;
                 sd = sd->parent;
                 if (!sd)
                         break;
         }
 }
 #else
 # define sched_domain_debug(sd, cpu) do { } while (0)
 #endif
 
 static int sd_degenerate(struct sched_domain *sd)
 {
         if (cpus_weight(sd->span) == 1)
                 return 1;
 
         /* Following flags need at least 2 groups */
         if (sd->flags & (SD_LOAD_BALANCE |
                          SD_BALANCE_NEWIDLE |
                          SD_BALANCE_FORK |
                          SD_BALANCE_EXEC |
                          SD_SHARE_CPUPOWER |
                          SD_SHARE_PKG_RESOURCES)) {
                 if (sd->groups != sd->groups->next)
                         return 0;
         }
 
         /* Following flags don't use groups */
         if (sd->flags & (SD_WAKE_IDLE |
                          SD_WAKE_AFFINE |
                          SD_WAKE_BALANCE))
                 return 0;
 
         return 1;
 }
 
 static int
 sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
 {
         unsigned long cflags = sd->flags, pflags = parent->flags;
 
         if (sd_degenerate(parent))
                 return 1;
 
         if (!cpus_equal(sd->span, parent->span))
                 return 0;
 
         /* Does parent contain flags not in child? */
         /* WAKE_BALANCE is a subset of WAKE_AFFINE */
         if (cflags & SD_WAKE_AFFINE)
                 pflags &= ~SD_WAKE_BALANCE;
         /* Flags needing groups don't count if only 1 group in parent */
         if (parent->groups == parent->groups->next) {
                 pflags &= ~(SD_LOAD_BALANCE |
                                 SD_BALANCE_NEWIDLE |
                                 SD_BALANCE_FORK |
                                 SD_BALANCE_EXEC |
                                 SD_SHARE_CPUPOWER |
                                 SD_SHARE_PKG_RESOURCES);
         }
         if (~cflags & pflags)
                 return 0;
 
         return 1;
 }
 
 static void rq_attach_root(struct rq *rq, struct root_domain *rd)
 {
         unsigned long flags;
         struct root_domain *reap = NULL;
 
         spin_lock_irqsave(&rq->lock, flags);
 
         if (rq->rd) {
                 struct root_domain *old_rd = rq->rd;
 
                 if (cpu_isset(rq->cpu, old_rd->online))
                         set_rq_offline(rq);
 
                 cpu_clear(rq->cpu, old_rd->span);
 
                 if (atomic_dec_and_test(&old_rd->refcount))
                         reap = old_rd;
         }
 
         atomic_inc(&rd->refcount);
         rq->rd = rd;
 
         cpu_set(rq->cpu, rd->span);
         if (cpu_isset(rq->cpu, cpu_online_map))
                 set_rq_online(rq);
 
         spin_unlock_irqrestore(&rq->lock, flags);
 
         /* Don't try to free the memory while in-atomic() */
         if (unlikely(reap))
                 kfree(reap);
 }
 
 static void init_rootdomain(struct root_domain *rd)
 {
         memset(rd, 0, sizeof(*rd));
 
         cpus_clear(rd->span);
         cpus_clear(rd->online);
 
         cpupri_init(&rd->cpupri);
 }
 
 static void init_defrootdomain(void)
 {
         init_rootdomain(&def_root_domain);
         atomic_set(&def_root_domain.refcount, 1);
 }
 
 static struct root_domain *alloc_rootdomain(void)
 {
         struct root_domain *rd;
 
         rd = kmalloc(sizeof(*rd), GFP_KERNEL);
         if (!rd)
                 return NULL;
 
         init_rootdomain(rd);
 
         return rd;
 }
 
 /*
  * Attach the domain 'sd' to 'cpu' as its base domain. Callers must
  * hold the hotplug lock.
  */
 static void
 cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
 {
         struct rq *rq = cpu_rq(cpu);
         struct sched_domain *tmp;
 
         /* Remove the sched domains which do not contribute to scheduling. */
         for (tmp = sd; tmp; tmp = tmp->parent) {
                 struct sched_domain *parent = tmp->parent;
                 if (!parent)
                         break;
                 if (sd_parent_degenerate(tmp, parent)) {
                         tmp->parent = parent->parent;
                         if (parent->parent)
                                 parent->parent->child = tmp;
                 }
         }
 
         if (sd && sd_degenerate(sd)) {
                 sd = sd->parent;
                 if (sd)
                         sd->child = NULL;
         }
 
         sched_domain_debug(sd, cpu);
 
         rq_attach_root(rq, rd);
         rcu_assign_pointer(rq->sd, sd);
 }
 
 /* cpus with isolated domains */
 static cpumask_t cpu_isolated_map = CPU_MASK_NONE;
 
 /* Setup the mask of cpus configured for isolated domains */
 static int __init isolated_cpu_setup(char *str)
 {
         int ints[NR_CPUS], i;
 
         str = get_options(str, ARRAY_SIZE(ints), ints);
         cpus_clear(cpu_isolated_map);
         for (i = 1; i <= ints[0]; i++)
                 if (ints[i] < NR_CPUS)
                         cpu_set(ints[i], cpu_isolated_map);
         return 1;
 }
 
 __setup("isolcpus=", isolated_cpu_setup);
 
 /*
  * init_sched_build_groups takes the cpumask we wish to span, and a pointer
  * to a function which identifies what group(along with sched group) a CPU
  * belongs to. The return value of group_fn must be a >= 0 and < NR_CPUS
  * (due to the fact that we keep track of groups covered with a cpumask_t).
  *
  * init_sched_build_groups will build a circular linked list of the groups
  * covered by the given span, and will set each group's ->cpumask correctly,
  * and ->cpu_power to 0.
  */
 static void
 init_sched_build_groups(cpumask_t span, const cpumask_t *cpu_map,
                         int (*group_fn)(int cpu, const cpumask_t *cpu_map,
                                         struct sched_group **sg))
 {
         struct sched_group *first = NULL, *last = NULL;
         cpumask_t covered = CPU_MASK_NONE;
         int i;
 
         for_each_cpu_mask(i, span) {
                 struct sched_group *sg;
                 int group = group_fn(i, cpu_map, &sg);
                 int j;
 
                 if (cpu_isset(i, covered))
                         continue;
 
                 sg->cpumask = CPU_MASK_NONE;
                 sg->__cpu_power = 0;
 
                 for_each_cpu_mask(j, span) {
                         if (group_fn(j, cpu_map, NULL) != group)
                                 continue;
 
                         cpu_set(j, covered);
                         cpu_set(j, sg->cpumask);
                 }
                 if (!first)
                         first = sg;
                 if (last)
                         last->next = sg;
                 last = sg;
         }
         last->next = first;
 }
 
 #define SD_NODES_PER_DOMAIN 16
 
 #ifdef CONFIG_NUMA
 
 /**
  * find_next_best_node - find the next node to include in a sched_domain
  * @node: node whose sched_domain we're building
  * @used_nodes: nodes already in the sched_domain
  *
  * Find the next node to include in a given scheduling domain. Simply
  * finds the closest node not already in the @used_nodes map.
  *
  * Should use nodemask_t.
  */
 static int find_next_best_node(int node, unsigned long *used_nodes)
 {
         int i, n, val, min_val, best_node = 0;
 
         min_val = INT_MAX;
 
         for (i = 0; i < MAX_NUMNODES; i++) {
                 /* Start at @node */
                 n = (node + i) % MAX_NUMNODES;
 
                 if (!nr_cpus_node(n))
                         continue;
 
                 /* Skip already used nodes */
                 if (test_bit(n, used_nodes))
                         continue;
 
                 /* Simple min distance search */
                 val = node_distance(node, n);
 
                 if (val < min_val) {
                         min_val = val;
                         best_node = n;
                 }
         }
 
         set_bit(best_node, used_nodes);
         return best_node;
 }
 
 /**
  * sched_domain_node_span - get a cpumask for a node's sched_domain
  * @node: node whose cpumask we're constructing
  * @size: number of nodes to include in this span
  *
  * Given a node, construct a good cpumask for its sched_domain to span. It
  * should be one that prevents unnecessary balancing, but also spreads tasks
  * out optimally.
  */
 static cpumask_t sched_domain_node_span(int node)
 {
         DECLARE_BITMAP(used_nodes, MAX_NUMNODES);
         cpumask_t span, nodemask;
         int i;
 
         cpus_clear(span);
         bitmap_zero(used_nodes, MAX_NUMNODES);
 
         nodemask = node_to_cpumask(node);
         cpus_or(span, span, nodemask);
         set_bit(node, used_nodes);
 
         for (i = 1; i < SD_NODES_PER_DOMAIN; i++) {
                 int next_node = find_next_best_node(node, used_nodes);
 
                 nodemask = node_to_cpumask(next_node);
                 cpus_or(span, span, nodemask);
         }
 
         return span;
 }
 #endif
 
 int sched_smt_power_savings = 0, sched_mc_power_savings = 0;
 
 /*
  * SMT sched-domains:
  */
 #ifdef CONFIG_SCHED_SMT
 static DEFINE_PER_CPU(struct sched_domain, cpu_domains);
 static DEFINE_PER_CPU(struct sched_group, sched_group_cpus);
 
 static int
 cpu_to_cpu_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg)
 {
         if (sg)
                 *sg = &per_cpu(sched_group_cpus, cpu);
         return cpu;
 }
 #endif
 
 /*
  * multi-core sched-domains:
  */
 #ifdef CONFIG_SCHED_MC
 static DEFINE_PER_CPU(struct sched_domain, core_domains);
 static DEFINE_PER_CPU(struct sched_group, sched_group_core);
 #endif
 
 #if defined(CONFIG_SCHED_MC) && defined(CONFIG_SCHED_SMT)
 static int
 cpu_to_core_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg)
 {
         int group;
         cpumask_t mask = per_cpu(cpu_sibling_map, cpu);
         cpus_and(mask, mask, *cpu_map);
         group = first_cpu(mask);
         if (sg)
                 *sg = &per_cpu(sched_group_core, group);
         return group;
 }
 #elif defined(CONFIG_SCHED_MC)
 static int
 cpu_to_core_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg)
 {
         if (sg)
                 *sg = &per_cpu(sched_group_core, cpu);
         return cpu;
 }
 #endif
 
 static DEFINE_PER_CPU(struct sched_domain, phys_domains);
 static DEFINE_PER_CPU(struct sched_group, sched_group_phys);
 
 static int
 cpu_to_phys_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg)
 {
         int group;
 #ifdef CONFIG_SCHED_MC
         cpumask_t mask = cpu_coregroup_map(cpu);
         cpus_and(mask, mask, *cpu_map);
         group = first_cpu(mask);
 #elif defined(CONFIG_SCHED_SMT)
         cpumask_t mask = per_cpu(cpu_sibling_map, cpu);
         cpus_and(mask, mask, *cpu_map);
         group = first_cpu(mask);
 #else
         group = cpu;
 #endif
         if (sg)
                 *sg = &per_cpu(sched_group_phys, group);
         return group;
 }
 
 #ifdef CONFIG_NUMA
 /*
  * The init_sched_build_groups can't handle what we want to do with node
  * groups, so roll our own. Now each node has its own list of groups which
  * gets dynamically allocated.
  */
 static DEFINE_PER_CPU(struct sched_domain, node_domains);
 static struct sched_group **sched_group_nodes_bycpu[NR_CPUS];
 
 static DEFINE_PER_CPU(struct sched_domain, allnodes_domains);
 static DEFINE_PER_CPU(struct sched_group, sched_group_allnodes);
 
 static int cpu_to_allnodes_group(int cpu, const cpumask_t *cpu_map,
                                  struct sched_group **sg)
 {
         cpumask_t nodemask = node_to_cpumask(cpu_to_node(cpu));
         int group;
 
         cpus_and(nodemask, nodemask, *cpu_map);
         group = first_cpu(nodemask);
 
         if (sg)
                 *sg = &per_cpu(sched_group_allnodes, group);
         return group;
 }
 
 static void init_numa_sched_groups_power(struct sched_group *group_head)
 {
         struct sched_group *sg = group_head;
         int j;
 
         if (!sg)
                 return;
         do {
                 for_each_cpu_mask(j, sg->cpumask) {
                         struct sched_domain *sd;
 
                         sd = &per_cpu(phys_domains, j);
                         if (j != first_cpu(sd->groups->cpumask)) {
                                 /*
                                  * Only add "power" once for each
                                  * physical package.
                                  */
                                 continue;
                         }
 
                         sg_inc_cpu_power(sg, sd->groups->__cpu_power);
                 }
                 sg = sg->next;
         } while (sg != group_head);
 }
 #endif
 
 #ifdef CONFIG_NUMA
 /* Free memory allocated for various sched_group structures */
 static void free_sched_groups(const cpumask_t *cpu_map)
 {
         int cpu, i;
 
         for_each_cpu_mask(cpu, *cpu_map) {
                 struct sched_group **sched_group_nodes
                         = sched_group_nodes_bycpu[cpu];
 
                 if (!sched_group_nodes)
                         continue;
 
                 for (i = 0; i < MAX_NUMNODES; i++) {
                         cpumask_t nodemask = node_to_cpumask(i);
                         struct sched_group *oldsg, *sg = sched_group_nodes[i];
 
                         cpus_and(nodemask, nodemask, *cpu_map);
                         if (cpus_empty(nodemask))
                                 continue;
 
                         if (sg == NULL)
                                 continue;
                         sg = sg->next;
 next_sg:
                         oldsg = sg;
                         sg = sg->next;
                         kfree(oldsg);
                         if (oldsg != sched_group_nodes[i])
                                 goto next_sg;
                 }
                 kfree(sched_group_nodes);
                 sched_group_nodes_bycpu[cpu] = NULL;
         }
 }
 #else
 static void free_sched_groups(const cpumask_t *cpu_map)
 {
 }
 #endif
 
 /*
  * Initialize sched groups cpu_power.
  *
  * cpu_power indicates the capacity of sched group, which is used while
  * distributing the load between different sched groups in a sched domain.
  * Typically cpu_power for all the groups in a sched domain will be same unless
  * there are asymmetries in the topology. If there are asymmetries, group
  * having more cpu_power will pickup more load compared to the group having
  * less cpu_power.
  *
  * cpu_power will be a multiple of SCHED_LOAD_SCALE. This multiple represents
  * the maximum number of tasks a group can handle in the presence of other idle
  * or lightly loaded groups in the same sched domain.
  */
 static void init_sched_groups_power(int cpu, struct sched_domain *sd)
 {
         struct sched_domain *child;
         struct sched_group *group;
 
         WARN_ON(!sd || !sd->groups);
 
         if (cpu != first_cpu(sd->groups->cpumask))
                 return;
 
         child = sd->child;
 
         sd->groups->__cpu_power = 0;
 
         /*
          * For perf policy, if the groups in child domain share resources
          * (for example cores sharing some portions of the cache hierarchy
          * or SMT), then set this domain groups cpu_power such that each group
          * can handle only one task, when there are other idle groups in the
          * same sched domain.
          */
         if (!child || (!(sd->flags & SD_POWERSAVINGS_BALANCE) &&
                        (child->flags &
                         (SD_SHARE_CPUPOWER | SD_SHARE_PKG_RESOURCES)))) {
                 sg_inc_cpu_power(sd->groups, SCHED_LOAD_SCALE);
                 return;
         }
 
         /*
          * add cpu_power of each child group to this groups cpu_power
          */
         group = child->groups;
         do {
                 sg_inc_cpu_power(sd->groups, group->__cpu_power);
                 group = group->next;
         } while (group != child->groups);
 }
 
 /*
  * Build sched domains for a given set of cpus and attach the sched domains
  * to the individual cpus
  */
 static int build_sched_domains(const cpumask_t *cpu_map)
 {
         int i;
         struct root_domain *rd;
 #ifdef CONFIG_NUMA
         struct sched_group **sched_group_nodes = NULL;
         int sd_allnodes = 0;
 
         /*
          * Allocate the per-node list of sched groups
          */
         sched_group_nodes = kcalloc(MAX_NUMNODES, sizeof(struct sched_group *),
                                     GFP_KERNEL);
         if (!sched_group_nodes) {
                 printk(KERN_WARNING "Can not alloc sched group node list\n");
                 return -ENOMEM;
         }
         sched_group_nodes_bycpu[first_cpu(*cpu_map)] = sched_group_nodes;
 #endif
 
         rd = alloc_rootdomain();
         if (!rd) {
                 printk(KERN_WARNING "Cannot alloc root domain\n");
                 return -ENOMEM;
         }
 
         /*
          * Set up domains for cpus specified by the cpu_map.
          */
         for_each_cpu_mask(i, *cpu_map) {
                 struct sched_domain *sd = NULL, *p;
                 cpumask_t nodemask = node_to_cpumask(cpu_to_node(i));
 
                 cpus_and(nodemask, nodemask, *cpu_map);
 
 #ifdef CONFIG_NUMA
                 if (cpus_weight(*cpu_map) >
                                 SD_NODES_PER_DOMAIN*cpus_weight(nodemask)) {
                         sd = &per_cpu(allnodes_domains, i);
                         *sd = SD_ALLNODES_INIT;
                         sd->span = *cpu_map;
                         cpu_to_allnodes_group(i, cpu_map, &sd->groups);
                         p = sd;
                         sd_allnodes = 1;
                 } else
                         p = NULL;
 
                 sd = &per_cpu(node_domains, i);
                 *sd = SD_NODE_INIT;
                 sd->span = sched_domain_node_span(cpu_to_node(i));
                 sd->parent = p;
                 if (p)
                         p->child = sd;
                 cpus_and(sd->span, sd->span, *cpu_map);
 #endif
 
                 p = sd;
                 sd = &per_cpu(phys_domains, i);
                 *sd = SD_CPU_INIT;
                 sd->span = nodemask;
                 sd->parent = p;
                 if (p)
                         p->child = sd;
                 cpu_to_phys_group(i, cpu_map, &sd->groups);
 
 #ifdef CONFIG_SCHED_MC
                 p = sd;
                 sd = &per_cpu(core_domains, i);
                 *sd = SD_MC_INIT;
                 sd->span = cpu_coregroup_map(i);
                 cpus_and(sd->span, sd->span, *cpu_map);
                 sd->parent = p;
                 p->child = sd;
                 cpu_to_core_group(i, cpu_map, &sd->groups);
 #endif
 
 #ifdef CONFIG_SCHED_SMT
                 p = sd;
                 sd = &per_cpu(cpu_domains, i);
                 *sd = SD_SIBLING_INIT;
                 sd->span = per_cpu(cpu_sibling_map, i);
                 cpus_and(sd->span, sd->span, *cpu_map);
                 sd->parent = p;
                 p->child = sd;
                 cpu_to_cpu_group(i, cpu_map, &sd->groups);
 #endif
         }
 
 #ifdef CONFIG_SCHED_SMT
         /* Set up CPU (sibling) groups */
         for_each_cpu_mask(i, *cpu_map) {
                 cpumask_t this_sibling_map = per_cpu(cpu_sibling_map, i);
                 cpus_and(this_sibling_map, this_sibling_map, *cpu_map);
                 if (i != first_cpu(this_sibling_map))
                         continue;
 
                 init_sched_build_groups(this_sibling_map, cpu_map,
                                         &cpu_to_cpu_group);
         }
 #endif
 
 #ifdef CONFIG_SCHED_MC
         /* Set up multi-core groups */
         for_each_cpu_mask(i, *cpu_map) {
                 cpumask_t this_core_map = cpu_coregroup_map(i);
                 cpus_and(this_core_map, this_core_map, *cpu_map);
                 if (i != first_cpu(this_core_map))
                         continue;
                 init_sched_build_groups(this_core_map, cpu_map,
                                         &cpu_to_core_group);
         }
 #endif
 
         /* Set up physical groups */
         for (i = 0; i < MAX_NUMNODES; i++) {
                 cpumask_t nodemask = node_to_cpumask(i);
 
                 cpus_and(nodemask, nodemask, *cpu_map);
                 if (cpus_empty(nodemask))
                         continue;
 
                 init_sched_build_groups(nodemask, cpu_map, &cpu_to_phys_group);
         }
 
 #ifdef CONFIG_NUMA
         /* Set up node groups */
         if (sd_allnodes)
                 init_sched_build_groups(*cpu_map, cpu_map,
                                         &cpu_to_allnodes_group);
 
         for (i = 0; i < MAX_NUMNODES; i++) {
                 /* Set up node groups */
                 struct sched_group *sg, *prev;
                 cpumask_t nodemask = node_to_cpumask(i);
                 cpumask_t domainspan;
                 cpumask_t covered = CPU_MASK_NONE;
                 int j;
 
                 cpus_and(nodemask, nodemask, *cpu_map);
                 if (cpus_empty(nodemask)) {
                         sched_group_nodes[i] = NULL;
                         continue;
                 }
 
                 domainspan = sched_domain_node_span(i);
                 cpus_and(domainspan, domainspan, *cpu_map);
 
                 sg = kmalloc_node(sizeof(struct sched_group), GFP_KERNEL, i);
                 if (!sg) {
                         printk(KERN_WARNING "Can not alloc domain group for "
                                 "node %d\n", i);
                         goto error;
                 }
                 sched_group_nodes[i] = sg;
                 for_each_cpu_mask(j, nodemask) {
                         struct sched_domain *sd;
 
                         sd = &per_cpu(node_domains, j);
                         sd->groups = sg;
                 }
                 sg->__cpu_power = 0;
                 sg->cpumask = nodemask;
                 sg->next = sg;
                 cpus_or(covered, covered, nodemask);
                 prev = sg;
 
                 for (j = 0; j < MAX_NUMNODES; j++) {
                         cpumask_t tmp, notcovered;
                         int n = (i + j) % MAX_NUMNODES;
 
                         cpus_complement(notcovered, covered);
                         cpus_and(tmp, notcovered, *cpu_map);
                         cpus_and(tmp, tmp, domainspan);
                         if (cpus_empty(tmp))
                                 break;
 
                         nodemask = node_to_cpumask(n);
                         cpus_and(tmp, tmp, nodemask);
                         if (cpus_empty(tmp))
                                 continue;