Cross-Referenced Linux and Device Driver Code

   /*
    *  kernel/sched.c
    *
    *  Kernel scheduler and related syscalls
    *
    *  Copyright (C) 1991-2002  Linus Torvalds
    *
    *  1996-12-23  Modified by Dave Grothe to fix bugs in semaphores and
    *              make semaphores SMP safe
   *  1998-11-19  Implemented schedule_timeout() and related stuff
   *              by Andrea Arcangeli
   *  2002-01-04  New ultra-scalable O(1) scheduler by Ingo Molnar:
   *              hybrid priority-list and round-robin design with
   *              an array-switch method of distributing timeslices
   *              and per-CPU runqueues.  Cleanups and useful suggestions
   *              by Davide Libenzi, preemptible kernel bits by Robert Love.
   *  2003-09-03  Interactivity tuning by Con Kolivas.
   *  2004-04-02  Scheduler domains code by Nick Piggin
   *  2007-04-15  Work begun on replacing all interactivity tuning with a
   *              fair scheduling design by Con Kolivas.
   *  2007-05-05  Load balancing (smp-nice) and other improvements
   *              by Peter Williams
   *  2007-05-06  Interactivity improvements to CFS by Mike Galbraith
   *  2007-07-01  Group scheduling enhancements by Srivatsa Vaddagiri
   *  2007-11-29  RT balancing improvements by Steven Rostedt, Gregory Haskins,
   *              Thomas Gleixner, Mike Kravetz
   */
  
  #include <linux/mm.h>
  #include <linux/module.h>
  #include <linux/nmi.h>
  #include <linux/init.h>
  #include <linux/uaccess.h>
  #include <linux/highmem.h>
  #include <linux/smp_lock.h>
  #include <asm/mmu_context.h>
  #include <linux/interrupt.h>
  #include <linux/capability.h>
  #include <linux/completion.h>
  #include <linux/kernel_stat.h>
  #include <linux/debug_locks.h>
  #include <linux/perf_counter.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/proc_fs.h>
  #include <linux/seq_file.h>
  #include <linux/sysctl.h>
  #include <linux/syscalls.h>
  #include <linux/times.h>
  #include <linux/tsacct_kern.h>
  #include <linux/kprobes.h>
  #include <linux/delayacct.h>
  #include <linux/reciprocal_div.h>
  #include <linux/unistd.h>
  #include <linux/pagemap.h>
  #include <linux/hrtimer.h>
  #include <linux/tick.h>
  #include <linux/debugfs.h>
  #include <linux/ctype.h>
  #include <linux/ftrace.h>
  
  #include <asm/tlb.h>
  #include <asm/irq_regs.h>
  
  #include "sched_cpupri.h"
  
  #define CREATE_TRACE_POINTS
  #include <trace/events/sched.h>
  
  /*
   * Convert user-nice values [ -20 ... 0 ... 19 ]
   * to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],
   * and back.
   */
  #define NICE_TO_PRIO(nice)      (MAX_RT_PRIO + (nice) + 20)
  #define PRIO_TO_NICE(prio)      ((prio) - MAX_RT_PRIO - 20)
  #define TASK_NICE(p)            PRIO_TO_NICE((p)->static_prio)
  
  /*
   * 'User priority' is the nice value converted to something we
   * can work with better when scaling various scheduler parameters,
   * it's a [ 0 ... 39 ] range.
   */
  #define USER_PRIO(p)            ((p)-MAX_RT_PRIO)
  #define TASK_USER_PRIO(p)       USER_PRIO((p)->static_prio)
 #define MAX_USER_PRIO           (USER_PRIO(MAX_PRIO))
 
 /*
  * Helpers for converting nanosecond timing to jiffy resolution
  */
 #define NS_TO_JIFFIES(TIME)     ((unsigned long)(TIME) / (NSEC_PER_SEC / HZ))
 
 #define NICE_0_LOAD             SCHED_LOAD_SCALE
 #define NICE_0_SHIFT            SCHED_LOAD_SHIFT
 
 /*
  * These are the 'tuning knobs' of the scheduler:
  *
  * default timeslice is 100 msecs (used only for SCHED_RR tasks).
  * Timeslices get refilled after they expire.
  */
 #define DEF_TIMESLICE           (100 * HZ / 1000)
 
 /*
  * single value that denotes runtime == period, ie unlimited time.
  */
 #define RUNTIME_INF     ((u64)~0ULL)
 
 #ifdef CONFIG_SMP
 
 static void double_rq_lock(struct rq *rq1, struct rq *rq2);
 
 /*
  * Divide a load by a sched group cpu_power : (load / sg->__cpu_power)
  * Since cpu_power is a 'constant', we can use a reciprocal divide.
  */
 static inline u32 sg_div_cpu_power(const struct sched_group *sg, u32 load)
 {
         return reciprocal_divide(load, sg->reciprocal_cpu_power);
 }
 
 /*
  * Each time a sched group cpu_power is changed,
  * we must compute its reciprocal value
  */
 static inline void sg_inc_cpu_power(struct sched_group *sg, u32 val)
 {
         sg->__cpu_power += val;
         sg->reciprocal_cpu_power = reciprocal_value(sg->__cpu_power);
 }
 #endif
 
 static inline int rt_policy(int policy)
 {
         if (unlikely(policy == SCHED_FIFO || policy == SCHED_RR))
                 return 1;
         return 0;
 }
 
 static inline int task_has_rt_policy(struct task_struct *p)
 {
         return rt_policy(p->policy);
 }
 
 /*
  * This is the priority-queue data structure of the RT scheduling class:
  */
 struct rt_prio_array {
         DECLARE_BITMAP(bitmap, MAX_RT_PRIO+1); /* include 1 bit for delimiter */
         struct list_head queue[MAX_RT_PRIO];
 };
 
 struct rt_bandwidth {
         /* nests inside the rq lock: */
         spinlock_t              rt_runtime_lock;
         ktime_t                 rt_period;
         u64                     rt_runtime;
         struct hrtimer          rt_period_timer;
 };
 
 static struct rt_bandwidth def_rt_bandwidth;
 
 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);
 
 static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer)
 {
         struct rt_bandwidth *rt_b =
                 container_of(timer, struct rt_bandwidth, rt_period_timer);
         ktime_t now;
         int overrun;
         int idle = 0;
 
         for (;;) {
                 now = hrtimer_cb_get_time(timer);
                 overrun = hrtimer_forward(timer, now, rt_b->rt_period);
 
                 if (!overrun)
                         break;
 
                 idle = do_sched_rt_period_timer(rt_b, overrun);
         }
 
         return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
 }
 
 static
 void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime)
 {
         rt_b->rt_period = ns_to_ktime(period);
         rt_b->rt_runtime = runtime;
 
         spin_lock_init(&rt_b->rt_runtime_lock);
 
         hrtimer_init(&rt_b->rt_period_timer,
                         CLOCK_MONOTONIC, HRTIMER_MODE_REL);
         rt_b->rt_period_timer.function = sched_rt_period_timer;
 }
 
 static inline int rt_bandwidth_enabled(void)
 {
         return sysctl_sched_rt_runtime >= 0;
 }
 
 static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
 {
         ktime_t now;
 
         if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
                 return;
 
         if (hrtimer_active(&rt_b->rt_period_timer))
                 return;
 
         spin_lock(&rt_b->rt_runtime_lock);
         for (;;) {
                 unsigned long delta;
                 ktime_t soft, hard;
 
                 if (hrtimer_active(&rt_b->rt_period_timer))
                         break;
 
                 now = hrtimer_cb_get_time(&rt_b->rt_period_timer);
                 hrtimer_forward(&rt_b->rt_period_timer, now, rt_b->rt_period);
 
                 soft = hrtimer_get_softexpires(&rt_b->rt_period_timer);
                 hard = hrtimer_get_expires(&rt_b->rt_period_timer);
                 delta = ktime_to_ns(ktime_sub(hard, soft));
                 __hrtimer_start_range_ns(&rt_b->rt_period_timer, soft, delta,
                                 HRTIMER_MODE_ABS_PINNED, 0);
         }
         spin_unlock(&rt_b->rt_runtime_lock);
 }
 
 #ifdef CONFIG_RT_GROUP_SCHED
 static void destroy_rt_bandwidth(struct rt_bandwidth *rt_b)
 {
         hrtimer_cancel(&rt_b->rt_period_timer);
 }
 #endif
 
 /*
  * sched_domains_mutex serializes calls to arch_init_sched_domains,
  * detach_destroy_domains and partition_sched_domains.
  */
 static DEFINE_MUTEX(sched_domains_mutex);
 
 #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_USER_SCHED
         uid_t uid;
 #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;
 
         struct rt_bandwidth rt_bandwidth;
 #endif
 
         struct rcu_head rcu;
         struct list_head list;
 
         struct task_group *parent;
         struct list_head siblings;
         struct list_head children;
 };
 
 #ifdef CONFIG_USER_SCHED
 
 /* Helper function to pass uid information to create_sched_user() */
 void set_tg_uid(struct user_struct *user)
 {
         user->tg->uid = user->uid;
 }
 
 /*
  * Root task group.
  *      Every UID task group (including init_task_group aka UID-0) will
  *      be a child to this group.
  */
 struct task_group root_task_group;
 
 #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;
 #endif /* CONFIG_FAIR_GROUP_SCHED */
 
 #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;
 #endif /* CONFIG_RT_GROUP_SCHED */
 #else /* !CONFIG_USER_SCHED */
 #define root_task_group init_task_group
 #endif /* CONFIG_USER_SCHED */
 
 /* 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);
 
 #ifdef CONFIG_SMP
 static int root_task_group_empty(void)
 {
         return list_empty(&root_task_group.children);
 }
 #endif
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 #ifdef CONFIG_USER_SCHED
 # define INIT_TASK_GROUP_LOAD   (2*NICE_0_LOAD)
 #else /* !CONFIG_USER_SCHED */
 # define INIT_TASK_GROUP_LOAD   NICE_0_LOAD
 #endif /* CONFIG_USER_SCHED */
 
 /*
  * A weight of 0 or 1 can cause arithmetics problems.
  * A weight of a cfs_rq is the sum of weights of which entities
  * are queued on this cfs_rq, so a weight of a entity should not be
  * too large, so as the shares value of a task group.
  * (The default weight is 1024 - so there's no practical
  *  limitation from this.)
  */
 #define MIN_SHARES      2
 #define MAX_SHARES      (1UL << 18)
 
 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;
 
 /* 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
         rcu_read_lock();
         tg = __task_cred(p)->user->tg;
         rcu_read_unlock();
 #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
 }
 
 #else
 
 #ifdef CONFIG_SMP
 static int root_task_group_empty(void)
 {
         return 1;
 }
 #endif
 
 static inline void set_task_rq(struct task_struct *p, unsigned int cpu) { }
 static inline struct task_group *task_group(struct task_struct *p)
 {
         return NULL;
 }
 
 #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 list_head tasks;
         struct list_head *balance_iterator;
 
         /*
          * '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, *last;
 
         unsigned int 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 */
 
 #ifdef CONFIG_SMP
         /*
          * the part of load.weight contributed by tasks
          */
         unsigned long task_weight;
 
         /*
          *   h_load = weight * f(tg)
          *
          * Where f(tg) is the recursive weight fraction assigned to
          * this group.
          */
         unsigned long h_load;
 
         /*
          * this cpu's part of tg->shares
          */
         unsigned long shares;
 
         /*
          * load.weight at the time we set shares
          */
         unsigned long rq_weight;
 #endif
 #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
         struct {
                 int curr; /* highest queued rt task prio */
 #ifdef CONFIG_SMP
                 int next; /* next highest */
 #endif
         } highest_prio;
 #endif
 #ifdef CONFIG_SMP
         unsigned long rt_nr_migratory;
         unsigned long rt_nr_total;
         int overloaded;
         struct plist_head pushable_tasks;
 #endif
         int rt_throttled;
         u64 rt_time;
         u64 rt_runtime;
         /* Nests inside the rq lock: */
         spinlock_t rt_runtime_lock;
 
 #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_var_t span;
         cpumask_var_t online;
 
         /*
          * The "RT overload" flag: it gets set if a CPU has more than
          * one runnable RT task.
          */
         cpumask_var_t rto_mask;
         atomic_t rto_count;
 #ifdef CONFIG_SMP
         struct cpupri cpupri;
 #endif
 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
         /*
          * Preferred wake up cpu nominated by sched_mc balance that will be
          * used when most cpus are idle in the system indicating overall very
          * low system utilisation. Triggered at POWERSAVINGS_BALANCE_WAKEUP(2)
          */
         unsigned int sched_mc_preferred_wakeup_cpu;
 #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: */
         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];
 #ifdef CONFIG_NO_HZ
         unsigned long last_tick_seen;
         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;
         u64 nr_migrations_in;
 
         struct cfs_rq cfs;
         struct rt_rq rt;
 
 #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;
 
         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;
 
         unsigned char idle_at_tick;
         /* For active balancing */
         int active_balance;
         int push_cpu;
         /* cpu of this runqueue: */
         int cpu;
         int online;
 
         unsigned long avg_load_per_task;
 
         struct task_struct *migration_thread;
         struct list_head migration_queue;
 #endif
 
         /* calc_load related fields */
         unsigned long calc_load_update;
         long calc_load_active;
 
 #ifdef CONFIG_SCHED_HRTICK
 #ifdef CONFIG_SMP
         int hrtick_csd_pending;
         struct call_single_data hrtick_csd;
 #endif
         struct hrtimer hrtick_timer;
 #endif
 
 #ifdef CONFIG_SCHEDSTATS
         /* latency stats */
         struct sched_info rq_sched_info;
         unsigned long long rq_cpu_time;
         /* could above be rq->cfs_rq.exec_clock + rq->rt_rq.rt_runtime ? */
 
         /* sys_sched_yield() stats */
         unsigned int yld_count;
 
         /* schedule() stats */
         unsigned int sched_switch;
         unsigned int sched_count;
         unsigned int sched_goidle;
 
         /* try_to_wake_up() stats */
         unsigned int ttwu_count;
         unsigned int ttwu_local;
 
         /* BKL stats */
         unsigned int bkl_count;
 #endif
 };
 
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
 
 static inline void check_preempt_curr(struct rq *rq, struct task_struct *p, int sync)
 {
         rq->curr->sched_class->check_preempt_curr(rq, p, sync);
 }
 
 static inline int cpu_of(struct rq *rq)
 {
 #ifdef CONFIG_SMP
         return rq->cpu;
 #else
         return 0;
 #endif
 }
 
 /*
  * 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)
 
 inline void update_rq_clock(struct rq *rq)
 {
         rq->clock = sched_clock_cpu(cpu_of(rq));
 }
 
 /*
  * 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;
 }
 
 /*
  * Debugging: various feature bits
  */
 
 #define SCHED_FEAT(name, enabled)       \
         __SCHED_FEAT_##name ,
 
 enum {
 #include "sched_features.h"
 };
 
 #undef SCHED_FEAT
 
 #define SCHED_FEAT(name, enabled)       \
         (1UL << __SCHED_FEAT_##name) * enabled |
 
 const_debug unsigned int sysctl_sched_features =
 #include "sched_features.h"
         0;
 
 #undef SCHED_FEAT
 
 #ifdef CONFIG_SCHED_DEBUG
 #define SCHED_FEAT(name, enabled)       \
         #name ,
 
 static __read_mostly char *sched_feat_names[] = {
 #include "sched_features.h"
         NULL
 };
 
 #undef SCHED_FEAT
 
 static int sched_feat_show(struct seq_file *m, void *v)
 {
         int i;
 
         for (i = 0; sched_feat_names[i]; i++) {
                 if (!(sysctl_sched_features & (1UL << i)))
                         seq_puts(m, "NO_");
                 seq_printf(m, "%s ", sched_feat_names[i]);
         }
         seq_puts(m, "\n");
 
         return 0;
 }
 
 static ssize_t
 sched_feat_write(struct file *filp, const char __user *ubuf,
                 size_t cnt, loff_t *ppos)
 {
         char buf[64];
         char *cmp = buf;
         int neg = 0;
         int i;
 
         if (cnt > 63)
                 cnt = 63;
 
         if (copy_from_user(&buf, ubuf, cnt))
                 return -EFAULT;
 
         buf[cnt] = 0;
 
         if (strncmp(buf, "NO_", 3) == 0) {
                 neg = 1;
                 cmp += 3;
         }
 
         for (i = 0; sched_feat_names[i]; i++) {
                 int len = strlen(sched_feat_names[i]);
 
                 if (strncmp(cmp, sched_feat_names[i], len) == 0) {
                         if (neg)
                                 sysctl_sched_features &= ~(1UL << i);
                         else
                                 sysctl_sched_features |= (1UL << i);
                         break;
                 }
         }
 
         if (!sched_feat_names[i])
                 return -EINVAL;
 
         filp->f_pos += cnt;
 
         return cnt;
 }
 
 static int sched_feat_open(struct inode *inode, struct file *filp)
 {
         return single_open(filp, sched_feat_show, NULL);
 }
 
 static struct file_operations sched_feat_fops = {
         .open           = sched_feat_open,
         .write          = sched_feat_write,
         .read           = seq_read,
         .llseek         = seq_lseek,
         .release        = single_release,
 };
 
 static __init int sched_init_debug(void)
 {
         debugfs_create_file("sched_features", 0644, NULL, NULL,
                         &sched_feat_fops);
 
         return 0;
 }
 late_initcall(sched_init_debug);
 
 #endif
 
 #define sched_feat(x) (sysctl_sched_features & (1UL << __SCHED_FEAT_##x))
 
 /*
  * Number of tasks to iterate in a single balance run.
  * Limited because this is done with IRQs disabled.
  */
 const_debug unsigned int sysctl_sched_nr_migrate = 32;
 
 /*
  * ratelimit for updating the group shares.
  * default: 0.25ms
  */
 unsigned int sysctl_sched_shares_ratelimit = 250000;
 
 /*
  * Inject some fuzzyness into changing the per-cpu group shares
  * this avoids remote rq-locks at the expense of fairness.
  * default: 4
  */
 unsigned int sysctl_sched_shares_thresh = 4;
 
 /*
  * 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;
 
 static inline u64 global_rt_period(void)
 {
         return (u64)sysctl_sched_rt_period * NSEC_PER_USEC;
 }
 
 static inline u64 global_rt_runtime(void)
 {
         if (sysctl_sched_rt_runtime < 0)
                 return RUNTIME_INF;
 
         return (u64)sysctl_sched_rt_runtime * NSEC_PER_USEC;
 }
 
 #ifndef prepare_arch_switch
 # define prepare_arch_switch(next)      do { } while (0)
 #endif
 #ifndef finish_arch_switch
 # define finish_arch_switch(prev)       do { } while (0)
 #endif
 
 static inline int task_current(struct rq *rq, struct task_struct *p)
 {
         return rq->curr == p;
 }
 
 #ifndef __ARCH_WANT_UNLOCKED_CTXSW
 static inline int task_running(struct rq *rq, struct task_struct *p)
 {
         return task_current(rq, p);
 }
 
 static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
 {
 }
 
 static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
 {
 #ifdef CONFIG_DEBUG_SPINLOCK
         /* this is a valid case when another task releases the spinlock */
         rq->lock.owner = current;
 #endif
         /*
          * If we are tracking spinlock dependencies then we have to
          * fix up the runqueue lock - which gets 'carried over' from
          * prev into current:
          */
         spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_);
 
         spin_unlock_irq(&rq->lock);
 }
 
 #else /* __ARCH_WANT_UNLOCKED_CTXSW */
 static inline int task_running(struct rq *rq, struct task_struct *p)
 {
 #ifdef CONFIG_SMP
         return p->oncpu;
 #else
         return task_current(rq, p);
 #endif
 }
 
 static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
 {
 #ifdef CONFIG_SMP
         /*
          * We can optimise this out completely for !SMP, because the
          * SMP rebalancing from interrupt is the only thing that cares
          * here.
          */
         next->oncpu = 1;
 #endif
 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
         spin_unlock_irq(&rq->lock);
 #else
         spin_unlock(&rq->lock);
 #endif
 }
 
 static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
 {
 #ifdef CONFIG_SMP
         /*
          * After ->oncpu is cleared, the task can be moved to a different CPU.
          * We must ensure this doesn't happen until the switch is completely
          * finished.
          */
         smp_wmb();
         prev->oncpu = 0;
 #endif
 #ifndef __ARCH_WANT_INTERRUPTS_ON_CTXSW
         local_irq_enable();
 #endif
 }
 #endif /* __ARCH_WANT_UNLOCKED_CTXSW */
 
 /*
  * __task_rq_lock - lock the runqueue a given task resides on.
  * Must be called interrupts disabled.
  */
 static inline struct rq *__task_rq_lock(struct task_struct *p)
         __acquires(rq->lock)
 {
         for (;;) {
                 struct rq *rq = task_rq(p);
                 spin_lock(&rq->lock);
                 if (likely(rq == task_rq(p)))
                         return rq;
                 spin_unlock(&rq->lock);
         }
 }
 
 /*
  * task_rq_lock - lock the runqueue a given task resides on and disable
  * interrupts. Note the ordering: we can safely lookup the task_rq without
  * explicitly disabling preemption.
  */
 static struct rq *task_rq_lock(struct task_struct *p, unsigned long *flags)
         __acquires(rq->lock)
 {
         struct rq *rq;
 
         for (;;) {
                 local_irq_save(*flags);
                 rq = task_rq(p);
                 spin_lock(&rq->lock);
                 if (likely(rq == task_rq(p)))
                         return rq;
                 spin_unlock_irqrestore(&rq->lock, *flags);
         }
 }
 
 void task_rq_unlock_wait(struct task_struct *p)
 {
         struct rq *rq = task_rq(p);
 
         smp_mb(); /* spin-unlock-wait is not a full memory barrier */
         spin_unlock_wait(&rq->lock);
 }
 
 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;
 }
 
 #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.
  */
 
 /*
  * 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 (!cpu_active(cpu_of(rq)))
                 return 0;
         return hrtimer_is_hres_active(&rq->hrtick_timer);
 }
 
 static void hrtick_clear(struct rq *rq)
 {
         if (hrtimer_active(&rq->hrtick_timer))
                 hrtimer_cancel(&rq->hrtick_timer);
 }
 
 /*
  * 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;
 }
 
 #ifdef CONFIG_SMP
 /*
  * called from hardirq (IPI) context
  */
 static void __hrtick_start(void *arg)
 {
         struct rq *rq = arg;
 
         spin_lock(&rq->lock);
         hrtimer_restart(&rq->hrtick_timer);
         rq->hrtick_csd_pending = 0;
         spin_unlock(&rq->lock);
 }
 
 /*
  * Called to set the hrtick timer state.
  *
  * called with rq->lock held and irqs disabled
  */
 static void hrtick_start(struct rq *rq, u64 delay)
 {
         struct hrtimer *timer = &rq->hrtick_timer;
         ktime_t time = ktime_add_ns(timer->base->get_time(), delay);
 
         hrtimer_set_expires(timer, time);
 
         if (rq == this_rq()) {
                 hrtimer_restart(timer);
         } else if (!rq->hrtick_csd_pending) {
                 __smp_call_function_single(cpu_of(rq), &rq->hrtick_csd, 0);
                 rq->hrtick_csd_pending = 1;
         }
 }
 
 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:
                 hrtick_clear(cpu_rq(cpu));
                 return NOTIFY_OK;
         }
 
         return NOTIFY_DONE;
 }
 
 static __init void init_hrtick(void)
 {
         hotcpu_notifier(hotplug_hrtick, 0);
 }
 #else
 /*
  * Called to set the hrtick timer state.
  *
  * called with rq->lock held and irqs disabled
  */
 static void hrtick_start(struct rq *rq, u64 delay)
 {
         __hrtimer_start_range_ns(&rq->hrtick_timer, ns_to_ktime(delay), 0,
                         HRTIMER_MODE_REL_PINNED, 0);
 }
 
 static inline void init_hrtick(void)
 {
 }
 #endif /* CONFIG_SMP */
 
 static void init_rq_hrtick(struct rq *rq)
 {
 #ifdef CONFIG_SMP
         rq->hrtick_csd_pending = 0;
 
         rq->hrtick_csd.flags = 0;
         rq->hrtick_csd.func = __hrtick_start;
         rq->hrtick_csd.info = rq;
 #endif
 
         hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
         rq->hrtick_timer.function = hrtick;
 }
 #else   /* CONFIG_SCHED_HRTICK */
 static inline void hrtick_clear(struct rq *rq)
 {
 }
 
 static inline void init_rq_hrtick(struct rq *rq)
 {
 }
 
 static inline void init_hrtick(void)
 {
 }
 #endif  /* CONFIG_SCHED_HRTICK */
 
 /*
  * resched_task - mark a task 'to be rescheduled now'.
  *
  * On UP this means the setting of the need_resched flag, on SMP it
  * might also involve a cross-CPU call to trigger the scheduler on
  * the target CPU.
  */
 #ifdef CONFIG_SMP
 
 #ifndef tsk_is_polling
 #define tsk_is_polling(t) test_tsk_thread_flag(t, TIF_POLLING_NRFLAG)
 #endif
 
 static void resched_task(struct task_struct *p)
 {
         int cpu;
 
         assert_spin_locked(&task_rq(p)->lock);
 
         if (test_tsk_need_resched(p))
                 return;
 
         set_tsk_need_resched(p);
 
         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 == 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_need_resched(rq->idle);
 
         /* NEED_RESCHED must be visible before we test polling */
         smp_mb();
         if (!tsk_is_polling(rq->idle))
                 smp_send_reschedule(cpu);
 }
 #endif /* CONFIG_NO_HZ */
 
 #else /* !CONFIG_SMP */
 static void resched_task(struct task_struct *p)
 {
         assert_spin_locked(&task_rq(p)->lock);
         set_tsk_need_resched(p);
 }
 #endif /* CONFIG_SMP */
 
 #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))
 
 /*
  * delta *= weight / lw
  */
 static unsigned long
 calc_delta_mine(unsigned long delta_exec, unsigned long weight,
                 struct load_weight *lw)
 {
         u64 tmp;
 
         if (!lw->inv_weight) {
                 if (BITS_PER_LONG > 32 && unlikely(lw->weight >= WMULT_CONST))
                         lw->inv_weight = 1;
                 else
                         lw->inv_weight = 1 + (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 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                3
 #define WMULT_IDLEPRIO         1431655765
 
 /*
  * 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
 
 /* Time spent by the tasks of the cpu accounting group executing in ... */
 enum cpuacct_stat_index {
         CPUACCT_STAT_USER,      /* ... user mode */
         CPUACCT_STAT_SYSTEM,    /* ... kernel mode */
 
         CPUACCT_STAT_NSTATS,
 };
 
 #ifdef CONFIG_CGROUP_CPUACCT
 static void cpuacct_charge(struct task_struct *tsk, u64 cputime);
 static void cpuacct_update_stats(struct task_struct *tsk,
                 enum cpuacct_stat_index idx, cputime_t val);
 #else
 static inline void cpuacct_charge(struct task_struct *tsk, u64 cputime) {}
 static inline void cpuacct_update_stats(struct task_struct *tsk,
                 enum cpuacct_stat_index idx, cputime_t val) {}
 #endif
 
 static inline void inc_cpu_load(struct rq *rq, unsigned long load)
 {
         update_load_add(&rq->load, load);
 }
 
 static inline void dec_cpu_load(struct rq *rq, unsigned long load)
 {
         update_load_sub(&rq->load, load);
 }
 
 #if (defined(CONFIG_SMP) && defined(CONFIG_FAIR_GROUP_SCHED)) || defined(CONFIG_RT_GROUP_SCHED)
 typedef int (*tg_visitor)(struct task_group *, void *);
 
 /*
  * Iterate the full tree, calling @down when first entering a node and @up when
  * leaving it for the final time.
  */
 static int walk_tg_tree(tg_visitor down, tg_visitor up, void *data)
 {
         struct task_group *parent, *child;
         int ret;
 
         rcu_read_lock();
         parent = &root_task_group;
 down:
         ret = (*down)(parent, data);
         if (ret)
                 goto out_unlock;
         list_for_each_entry_rcu(child, &parent->children, siblings) {
                 parent = child;
                 goto down;
 
 up:
                 continue;
         }
         ret = (*up)(parent, data);
         if (ret)
                 goto out_unlock;
 
         child = parent;
         parent = parent->parent;
         if (parent)
                 goto up;
 out_unlock:
         rcu_read_unlock();
 
         return ret;
 }
 
 static int tg_nop(struct task_group *tg, void *data)
 {
         return 0;
 }
 #endif
 
 #ifdef CONFIG_SMP
 static unsigned long source_load(int cpu, int type);
 static unsigned long target_load(int cpu, int type);
 static int task_hot(struct task_struct *p, u64 now, struct sched_domain *sd);
 
 static unsigned long cpu_avg_load_per_task(int cpu)
 {
         struct rq *rq = cpu_rq(cpu);
         unsigned long nr_running = ACCESS_ONCE(rq->nr_running);
 
         if (nr_running)
                 rq->avg_load_per_task = rq->load.weight / nr_running;
         else
                 rq->avg_load_per_task = 0;
 
         return rq->avg_load_per_task;
 }
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 
 static void __set_se_shares(struct sched_entity *se, unsigned long shares);
 
 /*
  * Calculate and set the cpu's group shares.
  */
 static void
 update_group_shares_cpu(struct task_group *tg, int cpu,
                         unsigned long sd_shares, unsigned long sd_rq_weight)
 {
         unsigned long shares;
         unsigned long rq_weight;
 
         if (!tg->se[cpu])
                 return;
 
         rq_weight = tg->cfs_rq[cpu]->rq_weight;
 
         /*
          *           \Sum shares * rq_weight
          * shares =  -----------------------
          *               \Sum rq_weight
          *
          */
         shares = (sd_shares * rq_weight) / sd_rq_weight;
         shares = clamp_t(unsigned long, shares, MIN_SHARES, MAX_SHARES);
 
         if (abs(shares - tg->se[cpu]->load.weight) >
                         sysctl_sched_shares_thresh) {
                 struct rq *rq = cpu_rq(cpu);
                 unsigned long flags;
 
                 spin_lock_irqsave(&rq->lock, flags);
                 tg->cfs_rq[cpu]->shares = shares;
 
                 __set_se_shares(tg->se[cpu], shares);
                 spin_unlock_irqrestore(&rq->lock, flags);
         }
 }
 
 /*
  * Re-compute the task group their per cpu shares over the given domain.
  * This needs to be done in a bottom-up fashion because the rq weight of a
  * parent group depends on the shares of its child groups.
  */
 static int tg_shares_up(struct task_group *tg, void *data)
 {
         unsigned long weight, rq_weight = 0;
         unsigned long shares = 0;
         struct sched_domain *sd = data;
         int i;
 
         for_each_cpu(i, sched_domain_span(sd)) {
                 /*
                  * If there are currently no tasks on the cpu pretend there
                  * is one of average load so that when a new task gets to
                  * run here it will not get delayed by group starvation.
                  */
                 weight = tg->cfs_rq[i]->load.weight;
                 if (!weight)
                         weight = NICE_0_LOAD;
 
                 tg->cfs_rq[i]->rq_weight = weight;
                 rq_weight += weight;
                 shares += tg->cfs_rq[i]->shares;
         }
 
         if ((!shares && rq_weight) || shares > tg->shares)
                 shares = tg->shares;
 
         if (!sd->parent || !(sd->parent->flags & SD_LOAD_BALANCE))
                 shares = tg->shares;
 
         for_each_cpu(i, sched_domain_span(sd))
                 update_group_shares_cpu(tg, i, shares, rq_weight);
 
         return 0;
 }
 
 /*
  * Compute the cpu's hierarchical load factor for each task group.
  * This needs to be done in a top-down fashion because the load of a child
  * group is a fraction of its parents load.
  */
 static int tg_load_down(struct task_group *tg, void *data)
 {
         unsigned long load;
         long cpu = (long)data;
 
         if (!tg->parent) {
                 load = cpu_rq(cpu)->load.weight;
         } else {
                 load = tg->parent->cfs_rq[cpu]->h_load;
                 load *= tg->cfs_rq[cpu]->shares;
                 load /= tg->parent->cfs_rq[cpu]->load.weight + 1;
         }
 
         tg->cfs_rq[cpu]->h_load = load;
 
         return 0;
 }
 
 static void update_shares(struct sched_domain *sd)
 {
         u64 now = cpu_clock(raw_smp_processor_id());
         s64 elapsed = now - sd->last_update;
 
         if (elapsed >= (s64)(u64)sysctl_sched_shares_ratelimit) {
                 sd->last_update = now;
                 walk_tg_tree(tg_nop, tg_shares_up, sd);
         }
 }
 
 static void update_shares_locked(struct rq *rq, struct sched_domain *sd)
 {
         spin_unlock(&rq->lock);
         update_shares(sd);
         spin_lock(&rq->lock);
 }
 
 static void update_h_load(long cpu)
 {
         walk_tg_tree(tg_load_down, tg_nop, (void *)cpu);
 }
 
 #else
 
 static inline void update_shares(struct sched_domain *sd)
 {
 }
 
 static inline void update_shares_locked(struct rq *rq, struct sched_domain *sd)
 {
 }
 
 #endif
 
 #ifdef CONFIG_PREEMPT
 
 /*
  * fair double_lock_balance: Safely acquires both rq->locks in a fair
  * way at the expense of forcing extra atomic operations in all
  * invocations.  This assures that the double_lock is acquired using the
  * same underlying policy as the spinlock_t on this architecture, which
  * reduces latency compared to the unfair variant below.  However, it
  * also adds more overhead and therefore may reduce throughput.
  */
 static inline int _double_lock_balance(struct rq *this_rq, struct rq *busiest)
         __releases(this_rq->lock)
         __acquires(busiest->lock)
         __acquires(this_rq->lock)
 {
         spin_unlock(&this_rq->lock);
         double_rq_lock(this_rq, busiest);
 
         return 1;
 }
 
 #else
 /*
  * Unfair double_lock_balance: Optimizes throughput at the expense of
  * latency by eliminating extra atomic operations when the locks are
  * already in proper order on entry.  This favors lower cpu-ids and will
  * grant the double lock to lower cpus over higher ids under contention,
  * regardless of entry order into the function.
  */
 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(!spin_trylock(&busiest->lock))) {
                 if (busiest < this_rq) {
                         spin_unlock(&this_rq->lock);
                         spin_lock(&busiest->lock);
                         spin_lock_nested(&this_rq->lock, SINGLE_DEPTH_NESTING);
                         ret = 1;
                 } else
                         spin_lock_nested(&busiest->lock, SINGLE_DEPTH_NESTING);
         }
         return ret;
 }
 
 #endif /* CONFIG_PREEMPT */
 
 /*
  * double_lock_balance - lock the busiest runqueue, this_rq is locked already.
  */
 static int double_lock_balance(struct rq *this_rq, struct rq *busiest)
 {
         if (unlikely(!irqs_disabled())) {
                 /* printk() doesn't work good under rq->lock */
                 spin_unlock(&this_rq->lock);
                 BUG_ON(1);
         }
 
         return _double_lock_balance(this_rq, busiest);
 }
 
 static inline void double_unlock_balance(struct rq *this_rq, struct rq *busiest)
         __releases(busiest->lock)
 {
         spin_unlock(&busiest->lock);
         lock_set_subclass(&this_rq->lock.dep_map, 0, _RET_IP_);
 }
 #endif
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 static void cfs_rq_set_shares(struct cfs_rq *cfs_rq, unsigned long shares)
 {
 #ifdef CONFIG_SMP
         cfs_rq->shares = shares;
 #endif
 }
 #endif
 
 static void calc_load_account_active(struct rq *this_rq);
 
 #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 void inc_nr_running(struct rq *rq)
 {
         rq->nr_running++;
 }
 
 static void dec_nr_running(struct rq *rq)
 {
         rq->nr_running--;
 }
 
 static void set_load_weight(struct task_struct *p)
 {
         if (task_has_rt_policy(p)) {
                 p->se.load.weight = prio_to_weight[0] * 2;
                 p->se.load.inv_weight = prio_to_wmult[0] >> 1;
                 return;
         }
 
         /*
          * SCHED_IDLE tasks get minimal weight:
          */
         if (p->policy == SCHED_IDLE) {
                 p->se.load.weight = WEIGHT_IDLEPRIO;
                 p->se.load.inv_weight = WMULT_IDLEPRIO;
                 return;
         }
 
         p->se.load.weight = prio_to_weight[p->static_prio - MAX_RT_PRIO];
         p->se.load.inv_weight = prio_to_wmult[p->static_prio - MAX_RT_PRIO];
 }
 
 static void update_avg(u64 *avg, u64 sample)
 {
         s64 diff = sample - *avg;
         *avg += diff >> 3;
 }
 
 static void enqueue_task(struct rq *rq, struct task_struct *p, int wakeup)
 {
         if (wakeup)
                 p->se.start_runtime = p->se.sum_exec_runtime;
 
         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)
 {
         if (sleep) {
                 if (p->se.last_wakeup) {
                         update_avg(&p->se.avg_overlap,
                                 p->se.sum_exec_runtime - p->se.last_wakeup);
                         p->se.last_wakeup = 0;
                 } else {
                         update_avg(&p->se.avg_wakeup,
                                 sysctl_sched_wakeup_granularity);
                 }
         }
 
         sched_info_dequeued(p);
         p->sched_class->dequeue_task(rq, p, sleep);
         p->se.on_rq = 0;
 }
 
 /*
  * __normal_prio - return the priority that is based on the static prio
  */
 static inline int __normal_prio(struct task_struct *p)
 {
         return p->static_prio;
 }
 
 /*
  * Calculate the expected normal priority: i.e. priority
  * without taking RT-inheritance into account. Might be
  * boosted by interactivity modifiers. Changes upon fork,
  * setprio syscalls, and whenever the interactivity
  * estimator recalculates.
  */
 static inline int normal_prio(struct task_struct *p)
 {
         int prio;
 
         if (task_has_rt_policy(p))
                 prio = MAX_RT_PRIO-1 - p->rt_priority;
         else
                 prio = __normal_prio(p);
         return prio;
 }
 
 /*
  * Calculate the current priority, i.e. the priority
  * taken into account by the scheduler. This value might
  * be boosted by RT tasks, or might be boosted by
  * interactivity modifiers. Will be RT if the task got
  * RT-boosted. If not then it returns p->normal_prio.
  */
 static int effective_prio(struct task_struct *p)
 {
         p->normal_prio = normal_prio(p);
         /*
          * If we are RT tasks or we were boosted to RT priority,
          * keep the priority unchanged. Otherwise, update priority
          * to the normal priority:
          */
         if (!rt_prio(p->prio))
                 return p->normal_prio;
         return p->prio;
 }
 
 /*
  * activate_task - move a task to the runqueue.
  */
 static void activate_task(struct rq *rq, struct task_struct *p, int wakeup)
 {
         if (task_contributes_to_load(p))
                 rq->nr_uninterruptible--;
 
         enqueue_task(rq, p, wakeup);
         inc_nr_running(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++;
 
         dequeue_task(rq, p, sleep);
         dec_nr_running(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;
 }
 
 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
 
 /* Used instead of source_load when we know the type == 0 */
 static unsigned long weighted_cpuload(const int cpu)
 {
         return cpu_rq(cpu)->load.weight;
 }
 
 /*
  * 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 (sched_feat(CACHE_HOT_BUDDY) &&
                         (&p->se == cfs_rq_of(&p->se)->next ||
                          &p->se == cfs_rq_of(&p->se)->last))
                 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;
 
         trace_sched_migrate_task(p, new_cpu);
 
 #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;
 #endif
         if (old_cpu != new_cpu) {
                 p->se.nr_migrations++;
                 new_rq->nr_migrations_in++;
 #ifdef CONFIG_SCHEDSTATS
                 if (task_hot(p, old_rq->clock, NULL))
                         schedstat_inc(p, se.nr_forced2_migrations);
 #endif
                 perf_swcounter_event(PERF_COUNT_SW_CPU_MIGRATIONS,
                                      1, 1, NULL, 0);
         }
         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_context_switch -   wait for a thread to complete at least one
  *                              context switch.
  *
  * @p must not be current.
  */
 void wait_task_context_switch(struct task_struct *p)
 {
         unsigned long nvcsw, nivcsw, flags;
         int running;
         struct rq *rq;
 
         nvcsw   = p->nvcsw;
         nivcsw  = p->nivcsw;
         for (;;) {
                 /*
                  * The runqueue is assigned before the actual context
                  * switch. We need to take the runqueue lock.
                  *
                  * We could check initially without the lock but it is
                  * very likely that we need to take the lock in every
                  * iteration.
                  */
                 rq = task_rq_lock(p, &flags);
                 running = task_running(rq, p);
                 task_rq_unlock(rq, &flags);
 
                 if (likely(!running))
                         break;
                 /*
                  * The switch count is incremented before the actual
                  * context switch. We thus wait for two switches to be
                  * sure at least one completed.
                  */
                 if ((p->nvcsw - nvcsw) > 1)
                         break;
                 if ((p->nivcsw - nivcsw) > 1)
                         break;
 
                 cpu_relax();
         }
 }
 
 /*
  * wait_task_inactive - wait for a thread to unschedule.
  *
  * If @match_state is nonzero, it's the @p->state value just checked and
  * not expected to change.  If it changes, i.e. @p might have woken up,
  * then return zero.  When we succeed in waiting for @p to be off its CPU,
  * we return a positive number (its total switch count).  If a second call
  * a short while later returns the same number, the caller can be sure that
  * @p has remained unscheduled the whole time.
  *
  * 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.
  */
 unsigned long wait_task_inactive(struct task_struct *p, long match_state)
 {
         unsigned long flags;
         int running, on_rq;
         unsigned long ncsw;
         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)) {
                         if (match_state && unlikely(p->state != match_state))
                                 return 0;
                         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_sched_wait_task(rq, p);
                 running = task_running(rq, p);
                 on_rq = p->se.on_rq;
                 ncsw = 0;
                 if (!match_state || p->state == match_state)
                         ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
                 task_rq_unlock(rq, &flags);
 
                 /*
                  * If it changed from the expected state, bail out now.
                  */
                 if (unlikely(!ncsw))
                         break;
 
                 /*
                  * 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 was 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;
         }
 
         return ncsw;
 }
 
 /***
  * 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();
 }
 EXPORT_SYMBOL_GPL(kick_process);
 
 /*
  * 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 || !sched_feat(LB_BIAS))
                 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 || !sched_feat(LB_BIAS))
                 return total;
 
         return max(rq->cpu_load[type-1], total);
 }
 
 /*
  * 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 (!cpumask_intersects(sched_group_cpus(group),
                                         &p->cpus_allowed))
                         continue;
 
                 local_group = cpumask_test_cpu(this_cpu,
                                                sched_group_cpus(group));
 
                 /* Tally up the load of all CPUs in the group */
                 avg_load = 0;
 
                 for_each_cpu(i, sched_group_cpus(group)) {
                         /* 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)
 {
         unsigned long load, min_load = ULONG_MAX;
         int idlest = -1;
         int i;
 
         /* Traverse only the allowed CPUs */
         for_each_cpu_and(i, sched_group_cpus(group), &p->cpus_allowed) {
                 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;
         }
 
         if (sd)
                 update_shares(sd);
 
         while (sd) {
                 struct sched_group *group;
                 int new_cpu, weight;
 
                 if (!(sd->flags & flag)) {
                         sd = sd->child;
                         continue;
                 }
 
                 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;
                 weight = cpumask_weight(sched_domain_span(sd));
                 sd = NULL;
                 for_each_domain(cpu, tmp) {
                         if (weight <= cpumask_weight(sched_domain_span(tmp)))
                                 break;
                         if (tmp->flags & flag)
                                 sd = tmp;
                 }
                 /* while loop will break here if sd == NULL */
         }
 
         return cpu;
 }
 
 #endif /* CONFIG_SMP */
 
 /**
  * task_oncpu_function_call - call a function on the cpu on which a task runs
  * @p:          the task to evaluate
  * @func:       the function to be called
  * @info:       the function call argument
  *
  * Calls the function @func when the task is currently running. This might
  * be on the current CPU, which just calls the function directly
  */
 void task_oncpu_function_call(struct task_struct *p,
                               void (*func) (void *info), void *info)
 {
         int cpu;
 
         preempt_disable();
         cpu = task_cpu(p);
         if (task_curr(p))
                 smp_call_function_single(cpu, func, info, 1);
         preempt_enable();
 }
 
 /***
  * try_to_wake_up - wake up a thread
  * @p: the to-be-woken-up thread
  * @state: the mask of task states that can be woken
  * @sync: do a synchronous wakeup?
  *
  * Put it on the run-queue if it's not already there. The "current"
  * thread is always on the run-queue (except when the actual
  * re-schedule is in progress), and as such you're allowed to do
  * the simpler "current->state = TASK_RUNNING" to mark yourself
  * runnable without the overhead of this.
  *
  * returns failure only if the task is already active.
  */
 static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
 {
         int cpu, orig_cpu, this_cpu, success = 0;
         unsigned long flags;
         long old_state;
         struct rq *rq;
 
         if (!sched_feat(SYNC_WAKEUPS))
                 sync = 0;
 
 #ifdef CONFIG_SMP
         if (sched_feat(LB_WAKEUP_UPDATE) && !root_task_group_empty()) {
                 struct sched_domain *sd;
 
                 this_cpu = raw_smp_processor_id();
                 cpu = task_cpu(p);
 
                 for_each_domain(this_cpu, sd) {
                         if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
                                 update_shares(sd);
                                 break;
                         }
                 }
         }
 #endif
 
         smp_wmb();
         rq = task_rq_lock(p, &flags);
         update_rq_clock(rq);
         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 (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
                                 schedstat_inc(sd, ttwu_wake_remote);
                                 break;
                         }
                 }
         }
 #endif /* CONFIG_SCHEDSTATS */
 
 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);
         activate_task(rq, p, 1);
         success = 1;
 
         /*
          * Only attribute actual wakeups done by this task.
          */
         if (!in_interrupt()) {
                 struct sched_entity *se = &current->se;
                 u64 sample = se->sum_exec_runtime;
 
                 if (se->last_wakeup)
                         sample -= se->last_wakeup;
                 else
                         sample -= se->start_runtime;
                 update_avg(&se->avg_wakeup, sample);
 
                 se->last_wakeup = se->sum_exec_runtime;
         }
 
 out_running:
         trace_sched_wakeup(rq, p, success);
         check_preempt_curr(rq, p, sync);
 
         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;
 }
 
 /**
  * wake_up_process - Wake up a specific process
  * @p: The process to be woken up.
  *
  * Attempt to wake up the nominated process and move it to the set of runnable
  * processes.  Returns 1 if the process was woken up, 0 if it was already
  * running.
  *
  * It may be assumed that this function implies a write memory barrier before
  * changing the task state if and only if any tasks are woken up.
  */
 int wake_up_process(struct task_struct *p)
 {
         return try_to_wake_up(p, TASK_ALL, 0);
 }
 EXPORT_SYMBOL(wake_up_process);
 
 int wake_up_state(struct task_struct *p, unsigned int state)
 {
         return try_to_wake_up(p, state, 0);
 }
 
 /*
  * Perform scheduler related setup for a newly forked process p.
  * p is forked by current.
  *
  * __sched_fork() is basic setup used by init_idle() too:
  */
 static void __sched_fork(struct task_struct *p)
 {
         p->se.exec_start                = 0;
         p->se.sum_exec_runtime          = 0;
         p->se.prev_sum_exec_runtime     = 0;
         p->se.nr_migrations             = 0;
         p->se.last_wakeup               = 0;
         p->se.avg_overlap               = 0;
         p->se.start_runtime             = 0;
         p->se.avg_wakeup                = sysctl_sched_wakeup_granularity;
 
 #ifdef CONFIG_SCHEDSTATS
         p->se.wait_start                        = 0;
         p->se.wait_max                          = 0;
         p->se.wait_count                        = 0;
         p->se.wait_sum                          = 0;
 
         p->se.sleep_start                       = 0;
         p->se.sleep_max                         = 0;
         p->se.sum_sleep_runtime                 = 0;
 
         p->se.block_start                       = 0;
         p->se.block_max                         = 0;
         p->se.exec_max                          = 0;
         p->se.slice_max                         = 0;
 
         p->se.nr_migrations_cold                = 0;
         p->se.nr_failed_migrations_affine       = 0;
         p->se.nr_failed_migrations_running      = 0;
         p->se.nr_failed_migrations_hot          = 0;
         p->se.nr_forced_migrations              = 0;
         p->se.nr_forced2_migrations             = 0;
 
         p->se.nr_wakeups                        = 0;
         p->se.nr_wakeups_sync                   = 0;
         p->se.nr_wakeups_migrate                = 0;
         p->se.nr_wakeups_local                  = 0;
         p->se.nr_wakeups_remote                 = 0;
         p->se.nr_wakeups_affine                 = 0;
         p->se.nr_wakeups_affine_attempts        = 0;
         p->se.nr_wakeups_passive                = 0;
         p->se.nr_wakeups_idle                   = 0;
 
 #endif
 
         INIT_LIST_HEAD(&p->rt.run_list);
         p->se.on_rq = 0;
         INIT_LIST_HEAD(&p->se.group_node);
 
 #ifdef CONFIG_PREEMPT_NOTIFIERS
         INIT_HLIST_HEAD(&p->preempt_notifiers);
 #endif
 
         /*
          * We mark the process as running here, but have not actually
          * inserted it onto the runqueue yet. This guarantees that
          * nobody will actually run it, and a signal or other external
          * event cannot wake it up and insert it on the runqueue either.
          */
         p->state = TASK_RUNNING;
 }
 
 /*
  * fork()/clone()-time setup:
  */
 void sched_fork(struct task_struct *p, int clone_flags)
 {
         int cpu = get_cpu();
 
         __sched_fork(p);
 
 #ifdef CONFIG_SMP
         cpu = sched_balance_self(cpu, SD_BALANCE_FORK);
 #endif
         set_task_cpu(p, cpu);
 
         /*
          * Make sure we do not leak PI boosting priority to the child:
          */
         p->prio = current->normal_prio;
         if (!rt_prio(p->prio))
                 p->sched_class = &fair_sched_class;
 
 #if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
         if (likely(sched_info_on()))
                 memset(&p->sched_info, 0, sizeof(p->sched_info));
 #endif
 #if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
         p->oncpu = 0;
 #endif
 #ifdef CONFIG_PREEMPT
         /* Want to start with kernel preemption disabled. */
         task_thread_info(p)->preempt_count = 1;
 #endif
         plist_node_init(&p->pushable_tasks, MAX_PRIO);
 
         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(rq);
         }
         trace_sched_wakeup_new(rq, p, 1);
         check_preempt_curr(rq, p, 0);
 #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 preempted & rescheduled
  * @notifier: notifier struct to register
  */
 void preempt_notifier_register(struct preempt_notifier *notifier)
 {
         hlist_add_head(&notifier->link, &current->preempt_notifiers);
 }
 EXPORT_SYMBOL_GPL(preempt_notifier_register);
 
 /**
  * preempt_notifier_unregister - no longer interested in preemption notifications
  * @notifier: notifier struct to unregister
  *
  * This is safe to call from within a preemption notifier.
  */
 void preempt_notifier_unregister(struct preempt_notifier *notifier)
 {
         hlist_del(&notifier->link);
 }
 EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
 
 static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
 {
         struct preempt_notifier *notifier;
         struct hlist_node *node;
 
         hlist_for_each_entry(notifier, node, &curr->preempt_notifiers, link)
                 notifier->ops->sched_in(notifier, raw_smp_processor_id());
 }
 
 static void
 fire_sched_out_preempt_notifiers(struct task_struct *curr,
                                  struct task_struct *next)
 {
         struct preempt_notifier *notifier;
         struct hlist_node *node;
 
         hlist_for_each_entry(notifier, node, &curr->preempt_notifiers, link)
                 notifier->ops->sched_out(notifier, next);
 }
 
 #else /* !CONFIG_PREEMPT_NOTIFIERS */
 
 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 /* CONFIG_PREEMPT_NOTIFIERS */
 
 /**
  * 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;
 #ifdef CONFIG_SMP
         int post_schedule = 0;
 
         if (current->sched_class->needs_post_schedule)
                 post_schedule = current->sched_class->needs_post_schedule(rq);
 #endif
 
         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);
         perf_counter_task_sched_in(current, cpu_of(rq));
         finish_lock_switch(rq, prev);
 #ifdef CONFIG_SMP
         if (post_schedule)
                 current->sched_class->post_schedule(rq);
 #endif
 
         fire_sched_in_preempt_notifiers(current);
         if (mm)
                 mmdrop(mm);
         if (unlikely(prev_state == TASK_DEAD)) {
                 /*
                  * Remove function-return probe instances associated with this
                  * task and put them back on the free list.
                  */
                 kprobe_flush_task(prev);
                 put_task_struct(prev);
         }
 }
 
 /**
  * schedule_tail - first thing a freshly forked thread must call.
  * @prev: the thread we just switched away from.
  */
 asmlinkage void schedule_tail(struct task_struct *prev)
         __releases(rq->lock)
 {
         struct rq *rq = this_rq();
 
         finish_task_switch(rq, prev);
 #ifdef __ARCH_WANT_UNLOCKED_CTXSW
         /* In this case, finish_task_switch does not reenable preemption */
         preempt_enable();
 #endif
         if (current->set_child_tid)
                 put_user(task_pid_vnr(current), current->set_child_tid);
 }
 
 /*
  * context_switch - switch to the new MM and the new
  * thread's register state.
  */
 static inline void
 context_switch(struct rq *rq, struct task_struct *prev,
                struct task_struct *next)
 {
         struct mm_struct *mm, *oldmm;
 
         prepare_task_switch(rq, prev, next);
         trace_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_start_context_switch(prev);
 
         if (unlikely(!mm)) {
                 next->active_mm = oldmm;
                 atomic_inc(&oldmm->mm_count);
                 enter_lazy_tlb(oldmm, next);
         } else
                 switch_mm(oldmm, mm, next);
 
         if (unlikely(!prev->mm)) {
                 prev->active_mm = NULL;
                 rq->prev_mm = oldmm;
         }
         /*
          * Since the runqueue lock will be released by the next
          * task (which is an invalid locking op but in the case
          * of the scheduler it's an obvious special-case), so we
          * do an early lockdep release here:
          */
 #ifndef __ARCH_WANT_UNLOCKED_CTXSW
         spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
 #endif
 
         /* Here we just switch the register state and the stack. */
         switch_to(prev, next, prev);
 
         barrier();
         /*
          * this_rq must be evaluated again because prev may have moved
          * CPUs since it called schedule(), thus the 'rq' on its stack
          * frame will be invalid.
          */
         finish_task_switch(this_rq(), prev);
 }
 
 /*
  * nr_running, nr_uninterruptible and nr_context_switches:
  *
  * externally visible scheduler statistics: current number of runnable
  * threads, current number of uninterruptible-sleeping threads, total
  * number of context switches performed since bootup.
  */
 unsigned long nr_running(void)
 {
         unsigned long i, sum = 0;
 
         for_each_online_cpu(i)
                 sum += cpu_rq(i)->nr_running;
 
         return sum;
 }
 
 unsigned long nr_uninterruptible(void)
 {
         unsigned long i, sum = 0;
 
         for_each_possible_cpu(i)
                 sum += cpu_rq(i)->nr_uninterruptible;
 
         /*
          * Since we read the counters lockless, it might be slightly
          * inaccurate. Do not allow it to go below zero though:
          */
         if (unlikely((long)sum < 0))
                 sum = 0;
 
         return sum;
 }
 
 unsigned long long nr_context_switches(void)
 {
         int i;
         unsigned long long sum = 0;
 
         for_each_possible_cpu(i)
                 sum += cpu_rq(i)->nr_switches;
 
         return sum;
 }
 
 unsigned long nr_iowait(void)
 {
         unsigned long i, sum = 0;
 
         for_each_possible_cpu(i)
                 sum += atomic_read(&cpu_rq(i)->nr_iowait);
 
         return sum;
 }
 
 /* Variables and functions for calc_load */
 static atomic_long_t calc_load_tasks;
 static unsigned long calc_load_update;
 unsigned long avenrun[3];
 EXPORT_SYMBOL(avenrun);
 
 /**
  * get_avenrun - get the load average array
  * @loads:      pointer to dest load array
  * @offset:     offset to add
  * @shift:      shift count to shift the result left
  *
  * These values are estimates at best, so no need for locking.
  */
 void get_avenrun(unsigned long *loads, unsigned long offset, int shift)
 {
         loads[0] = (avenrun[0] + offset) << shift;
         loads[1] = (avenrun[1] + offset) << shift;
         loads[2] = (avenrun[2] + offset) << shift;
 }
 
 static unsigned long
 calc_load(unsigned long load, unsigned long exp, unsigned long active)
 {
         load *= exp;
         load += active * (FIXED_1 - exp);
         return load >> FSHIFT;
 }
 
 /*
  * calc_load - update the avenrun load estimates 10 ticks after the
  * CPUs have updated calc_load_tasks.
  */
 void calc_global_load(void)
 {
         unsigned long upd = calc_load_update + 10;
         long active;
 
         if (time_before(jiffies, upd))
                 return;
 
         active = atomic_long_read(&calc_load_tasks);
         active = active > 0 ? active * FIXED_1 : 0;
 
         avenrun[0] = calc_load(avenrun[0], EXP_1, active);
         avenrun[1] = calc_load(avenrun[1], EXP_5, active);
         avenrun[2] = calc_load(avenrun[2], EXP_15, active);
 
         calc_load_update += LOAD_FREQ;
 }
 
 /*
  * Either called from update_cpu_load() or from a cpu going idle
  */
 static void calc_load_account_active(struct rq *this_rq)
 {
         long nr_active, delta;
 
         nr_active = this_rq->nr_running;
         nr_active += (long) this_rq->nr_uninterruptible;
 
         if (nr_active != this_rq->calc_load_active) {
                 delta = nr_active - this_rq->calc_load_active;
                 this_rq->calc_load_active = nr_active;
                 atomic_long_add(delta, &calc_load_tasks);
         }
 }
 
 /*
  * Externally visible per-cpu scheduler statistics:
  * cpu_nr_migrations(cpu) - number of migrations into that cpu
  */
 u64 cpu_nr_migrations(int cpu)
 {
         return cpu_rq(cpu)->nr_migrations_in;
 }
 
 /*
  * 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;
         }
 
         if (time_after_eq(jiffies, this_rq->calc_load_update)) {
                 this_rq->calc_load_update += LOAD_FREQ;
                 calc_load_account_active(this_rq);
         }
 }
 
 #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_nested(&rq2->lock, SINGLE_DEPTH_NESTING);
                 } else {
                         spin_lock(&rq2->lock);
                         spin_lock_nested(&rq1->lock, SINGLE_DEPTH_NESTING);
                 }
         }
         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);
 }
 
 /*
  * 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 (!cpumask_test_cpu(dest_cpu, &p->cpus_allowed)
             || unlikely(!cpu_active(dest_cpu)))
                 goto out;
 
         /* force the process onto the specified CPU */
         if (migrate_task(p, dest_cpu, &req)) {
                 /* Need to wait for migration thread (might exit: take ref). */
                 struct task_struct *mt = rq->migration_thread;
 
                 get_task_struct(mt);
                 task_rq_unlock(rq, &flags);
                 wake_up_process(mt);
                 put_task_struct(mt);
                 wait_for_completion(&req.done);
 
                 return;
         }
 out:
         task_rq_unlock(rq, &flags);
 }
 
 /*
  * sched_exec - execve() is a valuable balancing opportunity, because at
  * this point the task has the smallest effective memory and cache footprint.
  */
 void sched_exec(void)
 {
         int new_cpu, this_cpu = get_cpu();
         new_cpu = sched_balance_self(this_cpu, SD_BALANCE_EXEC);
         put_cpu();
         if (new_cpu != this_cpu)
                 sched_migrate_task(current, new_cpu);
 }
 
 /*
  * pull_task - move a task from a remote runqueue to the local runqueue.
  * Both runqueues must be locked.
  */
 static void pull_task(struct rq *src_rq, struct task_struct *p,
                       struct rq *this_rq, int this_cpu)
 {
         deactivate_task(src_rq, p, 0);
         set_task_cpu(p, this_cpu);
         activate_task(this_rq, p, 0);
         /*
          * Note that idle threads have a prio of MAX_PRIO, for this test
          * to be always true for them.
          */
         check_preempt_curr(this_rq, p, 0);
 }
 
 /*
  * 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)
 {
         int tsk_cache_hot = 0;
         /*
          * 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 (!cpumask_test_cpu(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.
          */
 
         tsk_cache_hot = task_hot(p, rq->clock, sd);
         if (!tsk_cache_hot ||
                 sd->nr_balance_failed > sd->cache_nice_tries) {
 #ifdef CONFIG_SCHEDSTATS
                 if (tsk_cache_hot) {
                         schedstat_inc(sd, lb_hot_gained[idle]);
                         schedstat_inc(p, se.nr_forced_migrations);
                 }
 #endif
                 return 1;
         }
 
         if (tsk_cache_hot) {
                 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;
         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;
 
         if ((p->se.load.weight >> 1) > rem_load_move ||
             !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;
 
 #ifdef CONFIG_PREEMPT
         /*
          * NEWIDLE balancing is a source of latency, so preemptible kernels
          * will stop after the first task is pulled to minimize the critical
          * section.
          */
         if (idle == CPU_NEWLY_IDLE)
                 goto out;
 #endif
 
         /*
          * 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;
 
 #ifdef CONFIG_PREEMPT
                 /*
                  * NEWIDLE balancing is a source of latency, so preemptible
                  * kernels will stop after the first task is pulled to minimize
                  * the critical section.
                  */
                 if (idle == CPU_NEWLY_IDLE && this_rq->nr_running)
                         break;
 #endif
         } 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;
 }
 /********** Helpers for find_busiest_group ************************/
 /*
  * sd_lb_stats - Structure to store the statistics of a sched_domain
  *              during load balancing.
  */
 struct sd_lb_stats {
         struct sched_group *busiest; /* Busiest group in this sd */
         struct sched_group *this;  /* Local group in this sd */
         unsigned long total_load;  /* Total load of all groups in sd */
         unsigned long total_pwr;   /*   Total power of all groups in sd */
         unsigned long avg_load;    /* Average load across all groups in sd */
 
         /** Statistics of this group */
         unsigned long this_load;
         unsigned long this_load_per_task;
         unsigned long this_nr_running;
 
         /* Statistics of the busiest group */
         unsigned long max_load;
         unsigned long busiest_load_per_task;
         unsigned long busiest_nr_running;
 
         int group_imb; /* Is there imbalance in this sd */
 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
         int power_savings_balance; /* Is powersave balance needed for this sd */
         struct sched_group *group_min; /* Least loaded group in sd */
         struct sched_group *group_leader; /* Group which relieves group_min */
         unsigned long min_load_per_task; /* load_per_task in group_min */
         unsigned long leader_nr_running; /* Nr running of group_leader */
         unsigned long min_nr_running; /* Nr running of group_min */
 #endif
 };
 
 /*
  * sg_lb_stats - stats of a sched_group required for load_balancing
  */
 struct sg_lb_stats {
         unsigned long avg_load; /*Avg load across the CPUs of the group */
         unsigned long group_load; /* Total load over the CPUs of the group */
         unsigned long sum_nr_running; /* Nr tasks running in the group */
         unsigned long sum_weighted_load; /* Weighted load of group's tasks */
         unsigned long group_capacity;
         int group_imb; /* Is there an imbalance in the group ? */
 };
 
 /**
  * group_first_cpu - Returns the first cpu in the cpumask of a sched_group.
  * @group: The group whose first cpu is to be returned.
  */
 static inline unsigned int group_first_cpu(struct sched_group *group)
 {
         return cpumask_first(sched_group_cpus(group));
 }
 
 /**
  * get_sd_load_idx - Obtain the load index for a given sched domain.
  * @sd: The sched_domain whose load_idx is to be obtained.
  * @idle: The Idle status of the CPU for whose sd load_icx is obtained.
  */
 static inline int get_sd_load_idx(struct sched_domain *sd,
                                         enum cpu_idle_type idle)
 {
         int load_idx;
 
         switch (idle) {
         case CPU_NOT_IDLE:
                 load_idx = sd->busy_idx;
                 break;
 
         case CPU_NEWLY_IDLE:
                 load_idx = sd->newidle_idx;
                 break;
         default:
                 load_idx = sd->idle_idx;
                 break;
         }
 
         return load_idx;
 }
 
 
 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
 /**
  * init_sd_power_savings_stats - Initialize power savings statistics for
  * the given sched_domain, during load balancing.
  *
  * @sd: Sched domain whose power-savings statistics are to be initialized.
  * @sds: Variable containing the statistics for sd.
  * @idle: Idle status of the CPU at which we're performing load-balancing.
  */
 static inline void init_sd_power_savings_stats(struct sched_domain *sd,
         struct sd_lb_stats *sds, enum cpu_idle_type idle)
 {
         /*
          * Busy processors will not participate in power savings
          * balance.
          */
         if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
                 sds->power_savings_balance = 0;
         else {
                 sds->power_savings_balance = 1;
                 sds->min_nr_running = ULONG_MAX;
                 sds->leader_nr_running = 0;
         }
 }
 
 /**
  * update_sd_power_savings_stats - Update the power saving stats for a
  * sched_domain while performing load balancing.
  *
  * @group: sched_group belonging to the sched_domain under consideration.
  * @sds: Variable containing the statistics of the sched_domain
  * @local_group: Does group contain the CPU for which we're performing
  *              load balancing ?
  * @sgs: Variable containing the statistics of the group.
  */
 static inline void update_sd_power_savings_stats(struct sched_group *group,
         struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)
 {
 
         if (!sds->power_savings_balance)
                 return;
 
         /*
          * If the local group is idle or completely loaded
          * no need to do power savings balance at this domain
          */
         if (local_group && (sds->this_nr_running >= sgs->group_capacity ||
                                 !sds->this_nr_running))
                 sds->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 (!sds->power_savings_balance ||
                 sgs->sum_nr_running >= sgs->group_capacity ||
                 !sgs->sum_nr_running)
                 return;
 
         /*
          * 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 ((sgs->sum_nr_running < sds->min_nr_running) ||
             (sgs->sum_nr_running == sds->min_nr_running &&
              group_first_cpu(group) > group_first_cpu(sds->group_min))) {
                 sds->group_min = group;
                 sds->min_nr_running = sgs->sum_nr_running;
                 sds->min_load_per_task = sgs->sum_weighted_load /
                                                 sgs->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 (sgs->sum_nr_running > sgs->group_capacity - 1)
                 return;
 
         if (sgs->sum_nr_running > sds->leader_nr_running ||
             (sgs->sum_nr_running == sds->leader_nr_running &&
              group_first_cpu(group) < group_first_cpu(sds->group_leader))) {
                 sds->group_leader = group;
                 sds->leader_nr_running = sgs->sum_nr_running;
         }
 }
 
 /**
  * check_power_save_busiest_group - see if there is potential for some power-savings balance
  * @sds: Variable containing the statistics of the sched_domain
  *      under consideration.
  * @this_cpu: Cpu at which we're currently performing load-balancing.
  * @imbalance: Variable to store the imbalance.
  *
  * Description:
  * Check if we have potential to perform some power-savings balance.
  * If yes, set the busiest group to be the least loaded group in the
  * sched_domain, so that it's CPUs can be put to idle.
  *
  * Returns 1 if there is potential to perform power-savings balance.
  * Else returns 0.
  */
 static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
                                         int this_cpu, unsigned long *imbalance)
 {
         if (!sds->power_savings_balance)
                 return 0;
 
         if (sds->this != sds->group_leader ||
                         sds->group_leader == sds->group_min)
                 return 0;
 
         *imbalance = sds->min_load_per_task;
         sds->busiest = sds->group_min;
 
         if (sched_mc_power_savings >= POWERSAVINGS_BALANCE_WAKEUP) {
                 cpu_rq(this_cpu)->rd->sched_mc_preferred_wakeup_cpu =
                         group_first_cpu(sds->group_leader);
         }
 
         return 1;
 
 }
 #else /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
 static inline void init_sd_power_savings_stats(struct sched_domain *sd,
         struct sd_lb_stats *sds, enum cpu_idle_type idle)
 {
         return;
 }
 
 static inline void update_sd_power_savings_stats(struct sched_group *group,
         struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)
 {
         return;
 }
 
 static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
                                         int this_cpu, unsigned long *imbalance)
 {
         return 0;
 }
 #endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
 
 
 /**
  * update_sg_lb_stats - Update sched_group's statistics for load balancing.
  * @group: sched_group whose statistics are to be updated.
  * @this_cpu: Cpu for which load balance is currently performed.
  * @idle: Idle status of this_cpu
  * @load_idx: Load index of sched_domain of this_cpu for load calc.
  * @sd_idle: Idle status of the sched_domain containing group.
  * @local_group: Does group contain this_cpu.
  * @cpus: Set of cpus considered for load balancing.
  * @balance: Should we balance.
  * @sgs: variable to hold the statistics for this group.
  */
 static inline void update_sg_lb_stats(struct sched_group *group, int this_cpu,
                         enum cpu_idle_type idle, int load_idx, int *sd_idle,
                         int local_group, const struct cpumask *cpus,
                         int *balance, struct sg_lb_stats *sgs)
 {
         unsigned long load, max_cpu_load, min_cpu_load;
         int i;
         unsigned int balance_cpu = -1, first_idle_cpu = 0;
         unsigned long sum_avg_load_per_task;
         unsigned long avg_load_per_task;
 
         if (local_group)
                 balance_cpu = group_first_cpu(group);
 
         /* Tally up the load of all CPUs in the group */
         sum_avg_load_per_task = avg_load_per_task = 0;
         max_cpu_load = 0;
         min_cpu_load = ~0UL;
 
         for_each_cpu_and(i, sched_group_cpus(group), cpus) {
                 struct rq *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;
                 }
 
                 sgs->group_load += load;
                 sgs->sum_nr_running += rq->nr_running;
                 sgs->sum_weighted_load += weighted_cpuload(i);
 
                 sum_avg_load_per_task += cpu_avg_load_per_task(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;
                 return;
         }
 
         /* Adjust by relative CPU power of the group */
         sgs->avg_load = sg_div_cpu_power(group,
                         sgs->group_load * SCHED_LOAD_SCALE);
 
 
         /*
          * Consider the group unbalanced when the imbalance is larger
          * than the average weight of two tasks.
          *
          * APZ: with cgroup the avg task weight can vary wildly and
          *      might not be a suitable number - should we keep a
          *      normalized nr_running number somewhere that negates
          *      the hierarchy?
          */
         avg_load_per_task = sg_div_cpu_power(group,
                         sum_avg_load_per_task * SCHED_LOAD_SCALE);
 
         if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task)
                 sgs->group_imb = 1;
 
         sgs->group_capacity = group->__cpu_power / SCHED_LOAD_SCALE;
 
 }
 
 /**
  * update_sd_lb_stats - Update sched_group's statistics for load balancing.
  * @sd: sched_domain whose statistics are to be updated.
  * @this_cpu: Cpu for which load balance is currently performed.
  * @idle: Idle status of this_cpu
  * @sd_idle: Idle status of the sched_domain containing group.
  * @cpus: Set of cpus considered for load balancing.
  * @balance: Should we balance.
  * @sds: variable to hold the statistics for this sched_domain.
  */
 static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu,
                         enum cpu_idle_type idle, int *sd_idle,
                         const struct cpumask *cpus, int *balance,
                         struct sd_lb_stats *sds)
 {
         struct sched_group *group = sd->groups;
         struct sg_lb_stats sgs;
         int load_idx;
 
         init_sd_power_savings_stats(sd, sds, idle);
         load_idx = get_sd_load_idx(sd, idle);
 
         do {
                 int local_group;
 
                 local_group = cpumask_test_cpu(this_cpu,
                                                sched_group_cpus(group));
                 memset(&sgs, 0, sizeof(sgs));
                 update_sg_lb_stats(group, this_cpu, idle, load_idx, sd_idle,
                                 local_group, cpus, balance, &sgs);
 
                 if (local_group && balance && !(*balance))
                         return;
 
                 sds->total_load += sgs.group_load;
                 sds->total_pwr += group->__cpu_power;
 
                 if (local_group) {
                         sds->this_load = sgs.avg_load;
                         sds->this = group;
                         sds->this_nr_running = sgs.sum_nr_running;
                         sds->this_load_per_task = sgs.sum_weighted_load;
                 } else if (sgs.avg_load > sds->max_load &&
                            (sgs.sum_nr_running > sgs.group_capacity ||
                                 sgs.group_imb)) {
                         sds->max_load = sgs.avg_load;
                         sds->busiest = group;
                         sds->busiest_nr_running = sgs.sum_nr_running;
                         sds->busiest_load_per_task = sgs.sum_weighted_load;
                         sds->group_imb = sgs.group_imb;
                 }
 
                 update_sd_power_savings_stats(group, sds, local_group, &sgs);
                 group = group->next;
         } while (group != sd->groups);
 
 }
 
 /**
  * fix_small_imbalance - Calculate the minor imbalance that exists
  *                      amongst the groups of a sched_domain, during
  *                      load balancing.
  * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
  * @this_cpu: The cpu at whose sched_domain we're performing load-balance.
  * @imbalance: Variable to store the imbalance.
  */
 static inline void fix_small_imbalance(struct sd_lb_stats *sds,
                                 int this_cpu, unsigned long *imbalance)
 {
         unsigned long tmp, pwr_now = 0, pwr_move = 0;
         unsigned int imbn = 2;
 
         if (sds->this_nr_running) {
                 sds->this_load_per_task /= sds->this_nr_running;
                 if (sds->busiest_load_per_task >
                                 sds->this_load_per_task)
                         imbn = 1;
         } else
                 sds->this_load_per_task =
                         cpu_avg_load_per_task(this_cpu);
 
         if (sds->max_load - sds->this_load + sds->busiest_load_per_task >=
                         sds->busiest_load_per_task * imbn) {
                 *imbalance = sds->busiest_load_per_task;
                 return;
         }
 
         /*
          * 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 += sds->busiest->__cpu_power *
                         min(sds->busiest_load_per_task, sds->max_load);
         pwr_now += sds->this->__cpu_power *
                         min(sds->this_load_per_task, sds->this_load);
         pwr_now /= SCHED_LOAD_SCALE;
 
         /* Amount of load we'd subtract */
         tmp = sg_div_cpu_power(sds->busiest,
                         sds->busiest_load_per_task * SCHED_LOAD_SCALE);
         if (sds->max_load > tmp)
                 pwr_move += sds->busiest->__cpu_power *
                         min(sds->busiest_load_per_task, sds->max_load - tmp);
 
         /* Amount of load we'd add */
         if (sds->max_load * sds->busiest->__cpu_power <
                 sds->busiest_load_per_task * SCHED_LOAD_SCALE)
                 tmp = sg_div_cpu_power(sds->this,
                         sds->max_load * sds->busiest->__cpu_power);
         else
                 tmp = sg_div_cpu_power(sds->this,
                         sds->busiest_load_per_task * SCHED_LOAD_SCALE);
         pwr_move += sds->this->__cpu_power *
                         min(sds->this_load_per_task, sds->this_load + tmp);
         pwr_move /= SCHED_LOAD_SCALE;
 
         /* Move if we gain throughput */
         if (pwr_move > pwr_now)
                 *imbalance = sds->busiest_load_per_task;
 }
 
 /**
  * calculate_imbalance - Calculate the amount of imbalance present within the
  *                       groups of a given sched_domain during load balance.
  * @sds: statistics of the sched_domain whose imbalance is to be calculated.
  * @this_cpu: Cpu for which currently load balance is being performed.
  * @imbalance: The variable to store the imbalance.
  */
 static inline void calculate_imbalance(struct sd_lb_stats *sds, int this_cpu,
                 unsigned long *imbalance)
 {
         unsigned long max_pull;
         /*
          * 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 (sds->max_load < sds->avg_load) {
                 *imbalance = 0;
                 return fix_small_imbalance(sds, this_cpu, imbalance);
         }
 
         /* Don't want to pull so many tasks that a group would go idle */
         max_pull = min(sds->max_load - sds->avg_load,
                         sds->max_load - sds->busiest_load_per_task);
 
         /* How much load to actually move to equalise the imbalance */
         *imbalance = min(max_pull * sds->busiest->__cpu_power,
                 (sds->avg_load - sds->this_load) * sds->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 < sds->busiest_load_per_task)
                 return fix_small_imbalance(sds, this_cpu, imbalance);
 
 }
 /******* find_busiest_group() helpers end here *********************/
 
 /**
  * find_busiest_group - Returns the busiest group within the sched_domain
  * if there is an imbalance. If there isn't an imbalance, and
  * the user has opted for power-savings, it returns a group whose
  * CPUs can be put to idle by rebalancing those tasks elsewhere, if
  * such a group exists.
  *
  * Also calculates the amount of weighted load which should be moved
  * to restore balance.
  *
  * @sd: The sched_domain whose busiest group is to be returned.
  * @this_cpu: The cpu for which load balancing is currently being performed.
  * @imbalance: Variable which stores amount of weighted load which should
  *              be moved to restore balance/put a group to idle.
  * @idle: The idle status of this_cpu.
  * @sd_idle: The idleness of sd
  * @cpus: The set of CPUs under consideration for load-balancing.
  * @balance: Pointer to a variable indicating if this_cpu
  *      is the appropriate cpu to perform load balancing at this_level.
  *
  * Returns:     - the busiest group if imbalance exists.
  *              - If no imbalance and user has opted for power-savings balance,
  *                 return the least loaded group whose CPUs can be
  *                 put to idle by rebalancing its tasks onto our group.
  */
 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, const struct cpumask *cpus, int *balance)
 {
         struct sd_lb_stats sds;
 
         memset(&sds, 0, sizeof(sds));
 
         /*
          * Compute the various statistics relavent for load balancing at
          * this level.
          */
         update_sd_lb_stats(sd, this_cpu, idle, sd_idle, cpus,
                                         balance, &sds);
 
         /* Cases where imbalance does not exist from POV of this_cpu */
         /* 1) this_cpu is not the appropriate cpu to perform load balancing
          *    at this level.
          * 2) There is no busy sibling group to pull from.
          * 3) This group is the busiest group.
          * 4) This group is more busy than the avg busieness at this
          *    sched_domain.
          * 5) The imbalance is within the specified limit.
          * 6) Any rebalance would lead to ping-pong
          */
         if (balance && !(*balance))
                 goto ret;
 
         if (!sds.busiest || sds.busiest_nr_running == 0)
                 goto out_balanced;
 
         if (sds.this_load >= sds.max_load)
                 goto out_balanced;
 
         sds.avg_load = (SCHED_LOAD_SCALE * sds.total_load) / sds.total_pwr;
 
         if (sds.this_load >= sds.avg_load)
                 goto out_balanced;
 
         if (100 * sds.max_load <= sd->imbalance_pct * sds.this_load)
                 goto out_balanced;
 
         sds.busiest_load_per_task /= sds.busiest_nr_running;
         if (sds.group_imb)
                 sds.busiest_load_per_task =
                         min(sds.busiest_load_per_task, sds.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 (sds.max_load <= sds.busiest_load_per_task)
                 goto out_balanced;
 
         /* Looks like there is an imbalance. Compute it */
         calculate_imbalance(&sds, this_cpu, imbalance);
         return sds.busiest;
 
 out_balanced:
         /*
          * There is no obvious imbalance. But check if we can do some balancing
          * to save power.
          */
         if (check_power_save_busiest_group(&sds, this_cpu, imbalance))
                 return sds.busiest;
 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, const struct cpumask *cpus)
 {
         struct rq *busiest = NULL, *rq;
         unsigned long max_load = 0;
         int i;
 
         for_each_cpu(i, sched_group_cpus(group)) {
                 unsigned long wl;
 
                 if (!cpumask_test_cpu(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
 
 /* Working cpumask for load_balance and load_balance_newidle. */
 static DEFINE_PER_CPU(cpumask_var_t, load_balance_tmpmask);
 
 /*
  * 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;
         unsigned long flags;
         struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);
 
         cpumask_setall(cpus);
 
         /*
          * 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:
         update_shares(sd);
         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)) {
                         cpumask_clear_cpu(cpu_of(busiest), cpus);
                         if (!cpumask_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 (!cpumask_test_cpu(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))
                 ld_moved = -1;
 
         goto out;
 
 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))
                 ld_moved = -1;
         else
                 ld_moved = 0;
 out:
         if (ld_moved)
                 update_shares(sd);
         return ld_moved;
 }
 
 /*
  * 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;
         struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);
 
         cpumask_setall(cpus);
 
         /*
          * 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:
         update_shares_locked(this_rq, sd);
         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);
                 double_unlock_balance(this_rq, busiest);
 
                 if (unlikely(all_pinned)) {
                         cpumask_clear_cpu(cpu_of(busiest), cpus);
                         if (!cpumask_empty(cpus))
                                 goto redo;
                 }
         }
 
         if (!ld_moved) {
                 int active_balance = 0;
 
                 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;
 
                 if (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP)
                         return -1;
 
                 if (sd->nr_balance_failed++ < 2)
                         return -1;
 
                 /*
                  * The only task running in a non-idle cpu can be moved to this
                  * cpu in an attempt to completely freeup the other CPU
                  * package. The same method used to move task in load_balance()
                  * have been extended for load_balance_newidle() to speedup
                  * consolidation at sched_mc=POWERSAVINGS_BALANCE_WAKEUP (2)
                  *
                  * The package power saving logic comes from
                  * find_busiest_group().  If there are no imbalance, then
                  * f_b_g() will return NULL.  However when sched_mc={1,2} then
                  * f_b_g() will select a group from which a running task may be
                  * pulled to this cpu in order to make the other package idle.
                  * If there is no opportunity to make a package idle and if
                  * there are no imbalance, then f_b_g() will return NULL and no
                  * action will be taken in load_balance_newidle().
                  *
                  * Under normal task pull operation due to imbalance, there
                  * will be more than one task in the source run queue and
                  * move_tasks() will succeed.  ld_moved will be true and this
                  * active balance code will not be triggered.
                  */
 
                 /* Lock busiest in correct order while this_rq is held */
                 double_lock_balance(this_rq, busiest);
 
                 /*
                  * don't kick the migration_thread, if the curr
                  * task on busiest cpu can't be moved to this_cpu
                  */
                 if (!cpumask_test_cpu(this_cpu, &busiest->curr->cpus_allowed)) {
                         double_unlock_balance(this_rq, busiest);
                         all_pinned = 1;
                         return ld_moved;
                 }
 
                 if (!busiest->active_balance) {
                         busiest->active_balance = 1;
                         busiest->push_cpu = this_cpu;
                         active_balance = 1;
                 }
 
                 double_unlock_balance(this_rq, busiest);
                 /*
                  * Should not call ttwu while holding a rq->lock
                  */
                 spin_unlock(&this_rq->lock);
                 if (active_balance)
                         wake_up_process(busiest->migration_thread);
                 spin_lock(&this_rq->lock);
 
         } else
                 sd->nr_balance_failed = 0;
 
         update_shares_locked(this_rq, sd);
         return ld_moved;
 
 out_balanced:
         schedstat_inc(sd, lb_balanced[CPU_NEWLY_IDLE]);