Merge tag 'nfsd-4.3' of git://linux-nfs.org/~bfields/linux

[karo-tx-linux.git] / kernel / time / timer.c

/*
 *  linux/kernel/timer.c
 *
 *  Kernel internal timers
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  1997-01-28  Modified by Finn Arne Gangstad to make timers scale better.
 *
 *  1997-09-10  Updated NTP code according to technical memorandum Jan '96
 *              "A Kernel Model for Precision Timekeeping" by Dave Mills
 *  1998-12-24  Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
 *              serialize accesses to xtime/lost_ticks).
 *                              Copyright (C) 1998  Andrea Arcangeli
 *  1999-03-10  Improved NTP compatibility by Ulrich Windl
 *  2002-05-31  Move sys_sysinfo here and make its locking sane, Robert Love
 *  2000-10-05  Implemented scalable SMP per-CPU timer handling.
 *                              Copyright (C) 2000, 2001, 2002  Ingo Molnar
 *              Designed by David S. Miller, Alexey Kuznetsov and Ingo Molnar
 */

#include <linux/kernel_stat.h>
#include <linux/export.h>
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/pid_namespace.h>
#include <linux/notifier.h>
#include <linux/thread_info.h>
#include <linux/time.h>
#include <linux/jiffies.h>
#include <linux/posix-timers.h>
#include <linux/cpu.h>
#include <linux/syscalls.h>
#include <linux/delay.h>
#include <linux/tick.h>
#include <linux/kallsyms.h>
#include <linux/irq_work.h>
#include <linux/sched.h>
#include <linux/sched/sysctl.h>
#include <linux/slab.h>
#include <linux/compat.h>

#include <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/div64.h>
#include <asm/timex.h>
#include <asm/io.h>

#include "tick-internal.h"

#define CREATE_TRACE_POINTS
#include <trace/events/timer.h>

__visible u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;

EXPORT_SYMBOL(jiffies_64);

/*
 * per-CPU timer vector definitions:
 */
#define TVN_BITS (CONFIG_BASE_SMALL ? 4 : 6)
#define TVR_BITS (CONFIG_BASE_SMALL ? 6 : 8)
#define TVN_SIZE (1 << TVN_BITS)
#define TVR_SIZE (1 << TVR_BITS)
#define TVN_MASK (TVN_SIZE - 1)
#define TVR_MASK (TVR_SIZE - 1)
#define MAX_TVAL ((unsigned long)((1ULL << (TVR_BITS + 4*TVN_BITS)) - 1))

struct tvec {
        struct hlist_head vec[TVN_SIZE];
};

struct tvec_root {
        struct hlist_head vec[TVR_SIZE];
};

struct tvec_base {
        spinlock_t lock;
        struct timer_list *running_timer;
        unsigned long timer_jiffies;
        unsigned long next_timer;
        unsigned long active_timers;
        unsigned long all_timers;
        int cpu;
        bool migration_enabled;
        bool nohz_active;
        struct tvec_root tv1;
        struct tvec tv2;
        struct tvec tv3;
        struct tvec tv4;
        struct tvec tv5;
} ____cacheline_aligned;


static DEFINE_PER_CPU(struct tvec_base, tvec_bases);

#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
unsigned int sysctl_timer_migration = 1;

void timers_update_migration(bool update_nohz)
{
        bool on = sysctl_timer_migration && tick_nohz_active;
        unsigned int cpu;

        /* Avoid the loop, if nothing to update */
        if (this_cpu_read(tvec_bases.migration_enabled) == on)
                return;

        for_each_possible_cpu(cpu) {
                per_cpu(tvec_bases.migration_enabled, cpu) = on;
                per_cpu(hrtimer_bases.migration_enabled, cpu) = on;
                if (!update_nohz)
                        continue;
                per_cpu(tvec_bases.nohz_active, cpu) = true;
                per_cpu(hrtimer_bases.nohz_active, cpu) = true;
        }
}

int timer_migration_handler(struct ctl_table *table, int write,
                            void __user *buffer, size_t *lenp,
                            loff_t *ppos)
{
        static DEFINE_MUTEX(mutex);
        int ret;

        mutex_lock(&mutex);
        ret = proc_dointvec(table, write, buffer, lenp, ppos);
        if (!ret && write)
                timers_update_migration(false);
        mutex_unlock(&mutex);
        return ret;
}

static inline struct tvec_base *get_target_base(struct tvec_base *base,
                                                int pinned)
{
        if (pinned || !base->migration_enabled)
                return this_cpu_ptr(&tvec_bases);
        return per_cpu_ptr(&tvec_bases, get_nohz_timer_target());
}
#else
static inline struct tvec_base *get_target_base(struct tvec_base *base,
                                                int pinned)
{
        return this_cpu_ptr(&tvec_bases);
}
#endif

static unsigned long round_jiffies_common(unsigned long j, int cpu,
                bool force_up)
{
        int rem;
        unsigned long original = j;

        /*
         * We don't want all cpus firing their timers at once hitting the
         * same lock or cachelines, so we skew each extra cpu with an extra
         * 3 jiffies. This 3 jiffies came originally from the mm/ code which
         * already did this.
         * The skew is done by adding 3*cpunr, then round, then subtract this
         * extra offset again.
         */
        j += cpu * 3;

        rem = j % HZ;

        /*
         * If the target jiffie is just after a whole second (which can happen
         * due to delays of the timer irq, long irq off times etc etc) then
         * we should round down to the whole second, not up. Use 1/4th second
         * as cutoff for this rounding as an extreme upper bound for this.
         * But never round down if @force_up is set.
         */
        if (rem < HZ/4 && !force_up) /* round down */
                j = j - rem;
        else /* round up */
                j = j - rem + HZ;

        /* now that we have rounded, subtract the extra skew again */
        j -= cpu * 3;

        /*
         * Make sure j is still in the future. Otherwise return the
         * unmodified value.
         */
        return time_is_after_jiffies(j) ? j : original;
}

/**
 * __round_jiffies - function to round jiffies to a full second
 * @j: the time in (absolute) jiffies that should be rounded
 * @cpu: the processor number on which the timeout will happen
 *
 * __round_jiffies() rounds an absolute time in the future (in jiffies)
 * up or down to (approximately) full seconds. This is useful for timers
 * for which the exact time they fire does not matter too much, as long as
 * they fire approximately every X seconds.
 *
 * By rounding these timers to whole seconds, all such timers will fire
 * at the same time, rather than at various times spread out. The goal
 * of this is to have the CPU wake up less, which saves power.
 *
 * The exact rounding is skewed for each processor to avoid all
 * processors firing at the exact same time, which could lead
 * to lock contention or spurious cache line bouncing.
 *
 * The return value is the rounded version of the @j parameter.
 */
unsigned long __round_jiffies(unsigned long j, int cpu)
{
        return round_jiffies_common(j, cpu, false);
}
EXPORT_SYMBOL_GPL(__round_jiffies);

/**
 * __round_jiffies_relative - function to round jiffies to a full second
 * @j: the time in (relative) jiffies that should be rounded
 * @cpu: the processor number on which the timeout will happen
 *
 * __round_jiffies_relative() rounds a time delta  in the future (in jiffies)
 * up or down to (approximately) full seconds. This is useful for timers
 * for which the exact time they fire does not matter too much, as long as
 * they fire approximately every X seconds.
 *
 * By rounding these timers to whole seconds, all such timers will fire
 * at the same time, rather than at various times spread out. The goal
 * of this is to have the CPU wake up less, which saves power.
 *
 * The exact rounding is skewed for each processor to avoid all
 * processors firing at the exact same time, which could lead
 * to lock contention or spurious cache line bouncing.
 *
 * The return value is the rounded version of the @j parameter.
 */
unsigned long __round_jiffies_relative(unsigned long j, int cpu)
{
        unsigned long j0 = jiffies;

        /* Use j0 because jiffies might change while we run */
        return round_jiffies_common(j + j0, cpu, false) - j0;
}
EXPORT_SYMBOL_GPL(__round_jiffies_relative);

/**
 * round_jiffies - function to round jiffies to a full second
 * @j: the time in (absolute) jiffies that should be rounded
 *
 * round_jiffies() rounds an absolute time in the future (in jiffies)
 * up or down to (approximately) full seconds. This is useful for timers
 * for which the exact time they fire does not matter too much, as long as
 * they fire approximately every X seconds.
 *
 * By rounding these timers to whole seconds, all such timers will fire
 * at the same time, rather than at various times spread out. The goal
 * of this is to have the CPU wake up less, which saves power.
 *
 * The return value is the rounded version of the @j parameter.
 */
unsigned long round_jiffies(unsigned long j)
{
        return round_jiffies_common(j, raw_smp_processor_id(), false);
}
EXPORT_SYMBOL_GPL(round_jiffies);

/**
 * round_jiffies_relative - function to round jiffies to a full second
 * @j: the time in (relative) jiffies that should be rounded
 *
 * round_jiffies_relative() rounds a time delta  in the future (in jiffies)
 * up or down to (approximately) full seconds. This is useful for timers
 * for which the exact time they fire does not matter too much, as long as
 * they fire approximately every X seconds.
 *
 * By rounding these timers to whole seconds, all such timers will fire
 * at the same time, rather than at various times spread out. The goal
 * of this is to have the CPU wake up less, which saves power.
 *
 * The return value is the rounded version of the @j parameter.
 */
unsigned long round_jiffies_relative(unsigned long j)
{
        return __round_jiffies_relative(j, raw_smp_processor_id());
}
EXPORT_SYMBOL_GPL(round_jiffies_relative);

/**
 * __round_jiffies_up - function to round jiffies up to a full second
 * @j: the time in (absolute) jiffies that should be rounded
 * @cpu: the processor number on which the timeout will happen
 *
 * This is the same as __round_jiffies() except that it will never
 * round down.  This is useful for timeouts for which the exact time
 * of firing does not matter too much, as long as they don't fire too
 * early.
 */
unsigned long __round_jiffies_up(unsigned long j, int cpu)
{
        return round_jiffies_common(j, cpu, true);
}
EXPORT_SYMBOL_GPL(__round_jiffies_up);

/**
 * __round_jiffies_up_relative - function to round jiffies up to a full second
 * @j: the time in (relative) jiffies that should be rounded
 * @cpu: the processor number on which the timeout will happen
 *
 * This is the same as __round_jiffies_relative() except that it will never
 * round down.  This is useful for timeouts for which the exact time
 * of firing does not matter too much, as long as they don't fire too
 * early.
 */
unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
{
        unsigned long j0 = jiffies;

        /* Use j0 because jiffies might change while we run */
        return round_jiffies_common(j + j0, cpu, true) - j0;
}
EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);

/**
 * round_jiffies_up - function to round jiffies up to a full second
 * @j: the time in (absolute) jiffies that should be rounded
 *
 * This is the same as round_jiffies() except that it will never
 * round down.  This is useful for timeouts for which the exact time
 * of firing does not matter too much, as long as they don't fire too
 * early.
 */
unsigned long round_jiffies_up(unsigned long j)
{
        return round_jiffies_common(j, raw_smp_processor_id(), true);
}
EXPORT_SYMBOL_GPL(round_jiffies_up);

/**
 * round_jiffies_up_relative - function to round jiffies up to a full second
 * @j: the time in (relative) jiffies that should be rounded
 *
 * This is the same as round_jiffies_relative() except that it will never
 * round down.  This is useful for timeouts for which the exact time
 * of firing does not matter too much, as long as they don't fire too
 * early.
 */
unsigned long round_jiffies_up_relative(unsigned long j)
{
        return __round_jiffies_up_relative(j, raw_smp_processor_id());
}
EXPORT_SYMBOL_GPL(round_jiffies_up_relative);

/**
 * set_timer_slack - set the allowed slack for a timer
 * @timer: the timer to be modified
 * @slack_hz: the amount of time (in jiffies) allowed for rounding
 *
 * Set the amount of time, in jiffies, that a certain timer has
 * in terms of slack. By setting this value, the timer subsystem
 * will schedule the actual timer somewhere between
 * the time mod_timer() asks for, and that time plus the slack.
 *
 * By setting the slack to -1, a percentage of the delay is used
 * instead.
 */
void set_timer_slack(struct timer_list *timer, int slack_hz)
{
        timer->slack = slack_hz;
}
EXPORT_SYMBOL_GPL(set_timer_slack);

static void
__internal_add_timer(struct tvec_base *base, struct timer_list *timer)
{
        unsigned long expires = timer->expires;
        unsigned long idx = expires - base->timer_jiffies;
        struct hlist_head *vec;

        if (idx < TVR_SIZE) {
                int i = expires & TVR_MASK;
                vec = base->tv1.vec + i;
        } else if (idx < 1 << (TVR_BITS + TVN_BITS)) {
                int i = (expires >> TVR_BITS) & TVN_MASK;
                vec = base->tv2.vec + i;
        } else if (idx < 1 << (TVR_BITS + 2 * TVN_BITS)) {
                int i = (expires >> (TVR_BITS + TVN_BITS)) & TVN_MASK;
                vec = base->tv3.vec + i;
        } else if (idx < 1 << (TVR_BITS + 3 * TVN_BITS)) {
                int i = (expires >> (TVR_BITS + 2 * TVN_BITS)) & TVN_MASK;
                vec = base->tv4.vec + i;
        } else if ((signed long) idx < 0) {
                /*
                 * Can happen if you add a timer with expires == jiffies,
                 * or you set a timer to go off in the past
                 */
                vec = base->tv1.vec + (base->timer_jiffies & TVR_MASK);
        } else {
                int i;
                /* If the timeout is larger than MAX_TVAL (on 64-bit
                 * architectures or with CONFIG_BASE_SMALL=1) then we
                 * use the maximum timeout.
                 */
                if (idx > MAX_TVAL) {
                        idx = MAX_TVAL;
                        expires = idx + base->timer_jiffies;
                }
                i = (expires >> (TVR_BITS + 3 * TVN_BITS)) & TVN_MASK;
                vec = base->tv5.vec + i;
        }

        hlist_add_head(&timer->entry, vec);
}

static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
{
        /* Advance base->jiffies, if the base is empty */
        if (!base->all_timers++)
                base->timer_jiffies = jiffies;

        __internal_add_timer(base, timer);
        /*
         * Update base->active_timers and base->next_timer
         */
        if (!(timer->flags & TIMER_DEFERRABLE)) {
                if (!base->active_timers++ ||
                    time_before(timer->expires, base->next_timer))
                        base->next_timer = timer->expires;
        }

        /*
         * Check whether the other CPU is in dynticks mode and needs
         * to be triggered to reevaluate the timer wheel.
         * We are protected against the other CPU fiddling
         * with the timer by holding the timer base lock. This also
         * makes sure that a CPU on the way to stop its tick can not
         * evaluate the timer wheel.
         *
         * Spare the IPI for deferrable timers on idle targets though.
         * The next busy ticks will take care of it. Except full dynticks
         * require special care against races with idle_cpu(), lets deal
         * with that later.
         */
        if (base->nohz_active) {
                if (!(timer->flags & TIMER_DEFERRABLE) ||
                    tick_nohz_full_cpu(base->cpu))
                        wake_up_nohz_cpu(base->cpu);
        }
}

#ifdef CONFIG_TIMER_STATS
void __timer_stats_timer_set_start_info(struct timer_list *timer, void *addr)
{
        if (timer->start_site)
                return;

        timer->start_site = addr;
        memcpy(timer->start_comm, current->comm, TASK_COMM_LEN);
        timer->start_pid = current->pid;
}

static void timer_stats_account_timer(struct timer_list *timer)
{
        if (likely(!timer->start_site))
                return;

        timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
                                 timer->function, timer->start_comm,
                                 timer->flags);
}

#else
static void timer_stats_account_timer(struct timer_list *timer) {}
#endif

#ifdef CONFIG_DEBUG_OBJECTS_TIMERS

static struct debug_obj_descr timer_debug_descr;

static void *timer_debug_hint(void *addr)
{
        return ((struct timer_list *) addr)->function;
}

/*
 * fixup_init is called when:
 * - an active object is initialized
 */
static int timer_fixup_init(void *addr, enum debug_obj_state state)
{
        struct timer_list *timer = addr;

        switch (state) {
        case ODEBUG_STATE_ACTIVE:
                del_timer_sync(timer);
                debug_object_init(timer, &timer_debug_descr);
                return 1;
        default:
                return 0;
        }
}

/* Stub timer callback for improperly used timers. */
static void stub_timer(unsigned long data)
{
        WARN_ON(1);
}

/*
 * fixup_activate is called when:
 * - an active object is activated
 * - an unknown object is activated (might be a statically initialized object)
 */
static int timer_fixup_activate(void *addr, enum debug_obj_state state)
{
        struct timer_list *timer = addr;

        switch (state) {

        case ODEBUG_STATE_NOTAVAILABLE:
                /*
                 * This is not really a fixup. The timer was
                 * statically initialized. We just make sure that it
                 * is tracked in the object tracker.
                 */
                if (timer->entry.pprev == NULL &&
                    timer->entry.next == TIMER_ENTRY_STATIC) {
                        debug_object_init(timer, &timer_debug_descr);
                        debug_object_activate(timer, &timer_debug_descr);
                        return 0;
                } else {
                        setup_timer(timer, stub_timer, 0);
                        return 1;
                }
                return 0;

        case ODEBUG_STATE_ACTIVE:
                WARN_ON(1);

        default:
                return 0;
        }
}

/*
 * fixup_free is called when:
 * - an active object is freed
 */
static int timer_fixup_free(void *addr, enum debug_obj_state state)
{
        struct timer_list *timer = addr;

        switch (state) {
        case ODEBUG_STATE_ACTIVE:
                del_timer_sync(timer);
                debug_object_free(timer, &timer_debug_descr);
                return 1;
        default:
                return 0;
        }
}

/*
 * fixup_assert_init is called when:
 * - an untracked/uninit-ed object is found
 */
static int timer_fixup_assert_init(void *addr, enum debug_obj_state state)
{
        struct timer_list *timer = addr;

        switch (state) {
        case ODEBUG_STATE_NOTAVAILABLE:
                if (timer->entry.next == TIMER_ENTRY_STATIC) {
                        /*
                         * This is not really a fixup. The timer was
                         * statically initialized. We just make sure that it
                         * is tracked in the object tracker.
                         */
                        debug_object_init(timer, &timer_debug_descr);
                        return 0;
                } else {
                        setup_timer(timer, stub_timer, 0);
                        return 1;
                }
        default:
                return 0;
        }
}

static struct debug_obj_descr timer_debug_descr = {
        .name                   = "timer_list",
        .debug_hint             = timer_debug_hint,
        .fixup_init             = timer_fixup_init,
        .fixup_activate         = timer_fixup_activate,
        .fixup_free             = timer_fixup_free,
        .fixup_assert_init      = timer_fixup_assert_init,
};

static inline void debug_timer_init(struct timer_list *timer)
{
        debug_object_init(timer, &timer_debug_descr);
}

static inline void debug_timer_activate(struct timer_list *timer)
{
        debug_object_activate(timer, &timer_debug_descr);
}

static inline void debug_timer_deactivate(struct timer_list *timer)
{
        debug_object_deactivate(timer, &timer_debug_descr);
}

static inline void debug_timer_free(struct timer_list *timer)
{
        debug_object_free(timer, &timer_debug_descr);
}

static inline void debug_timer_assert_init(struct timer_list *timer)
{
        debug_object_assert_init(timer, &timer_debug_descr);
}

static void do_init_timer(struct timer_list *timer, unsigned int flags,
                          const char *name, struct lock_class_key *key);

void init_timer_on_stack_key(struct timer_list *timer, unsigned int flags,
                             const char *name, struct lock_class_key *key)
{
        debug_object_init_on_stack(timer, &timer_debug_descr);
        do_init_timer(timer, flags, name, key);
}
EXPORT_SYMBOL_GPL(init_timer_on_stack_key);

void destroy_timer_on_stack(struct timer_list *timer)
{
        debug_object_free(timer, &timer_debug_descr);
}
EXPORT_SYMBOL_GPL(destroy_timer_on_stack);

#else
static inline void debug_timer_init(struct timer_list *timer) { }
static inline void debug_timer_activate(struct timer_list *timer) { }
static inline void debug_timer_deactivate(struct timer_list *timer) { }
static inline void debug_timer_assert_init(struct timer_list *timer) { }
#endif

static inline void debug_init(struct timer_list *timer)
{
        debug_timer_init(timer);
        trace_timer_init(timer);
}

static inline void
debug_activate(struct timer_list *timer, unsigned long expires)
{
        debug_timer_activate(timer);
        trace_timer_start(timer, expires, timer->flags);
}

static inline void debug_deactivate(struct timer_list *timer)
{
        debug_timer_deactivate(timer);
        trace_timer_cancel(timer);
}

static inline void debug_assert_init(struct timer_list *timer)
{
        debug_timer_assert_init(timer);
}

static void do_init_timer(struct timer_list *timer, unsigned int flags,
                          const char *name, struct lock_class_key *key)
{
        timer->entry.pprev = NULL;
        timer->flags = flags | raw_smp_processor_id();
        timer->slack = -1;
#ifdef CONFIG_TIMER_STATS
        timer->start_site = NULL;
        timer->start_pid = -1;
        memset(timer->start_comm, 0, TASK_COMM_LEN);
#endif
        lockdep_init_map(&timer->lockdep_map, name, key, 0);
}

/**
 * init_timer_key - initialize a timer
 * @timer: the timer to be initialized
 * @flags: timer flags
 * @name: name of the timer
 * @key: lockdep class key of the fake lock used for tracking timer
 *       sync lock dependencies
 *
 * init_timer_key() must be done to a timer prior calling *any* of the
 * other timer functions.
 */
void init_timer_key(struct timer_list *timer, unsigned int flags,
                    const char *name, struct lock_class_key *key)
{
        debug_init(timer);
        do_init_timer(timer, flags, name, key);
}
EXPORT_SYMBOL(init_timer_key);

static inline void detach_timer(struct timer_list *timer, bool clear_pending)
{
        struct hlist_node *entry = &timer->entry;

        debug_deactivate(timer);

        __hlist_del(entry);
        if (clear_pending)
                entry->pprev = NULL;
        entry->next = LIST_POISON2;
}

static inline void
detach_expired_timer(struct timer_list *timer, struct tvec_base *base)
{
        detach_timer(timer, true);
        if (!(timer->flags & TIMER_DEFERRABLE))
                base->active_timers--;
        base->all_timers--;
}

static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,
                             bool clear_pending)
{
        if (!timer_pending(timer))
                return 0;

        detach_timer(timer, clear_pending);
        if (!(timer->flags & TIMER_DEFERRABLE)) {
                base->active_timers--;
                if (timer->expires == base->next_timer)
                        base->next_timer = base->timer_jiffies;
        }
        /* If this was the last timer, advance base->jiffies */
        if (!--base->all_timers)
                base->timer_jiffies = jiffies;
        return 1;
}

/*
 * We are using hashed locking: holding per_cpu(tvec_bases).lock
 * means that all timers which are tied to this base via timer->base are
 * locked, and the base itself is locked too.
 *
 * So __run_timers/migrate_timers can safely modify all timers which could
 * be found on ->tvX lists.
 *
 * When the timer's base is locked and removed from the list, the
 * TIMER_MIGRATING flag is set, FIXME
 */
static struct tvec_base *lock_timer_base(struct timer_list *timer,
                                        unsigned long *flags)
        __acquires(timer->base->lock)
{
        for (;;) {
                u32 tf = timer->flags;
                struct tvec_base *base;

                if (!(tf & TIMER_MIGRATING)) {
                        base = per_cpu_ptr(&tvec_bases, tf & TIMER_CPUMASK);
                        spin_lock_irqsave(&base->lock, *flags);
                        if (timer->flags == tf)
                                return base;
                        spin_unlock_irqrestore(&base->lock, *flags);
                }
                cpu_relax();
        }
}

static inline int
__mod_timer(struct timer_list *timer, unsigned long expires,
            bool pending_only, int pinned)
{
        struct tvec_base *base, *new_base;
        unsigned long flags;
        int ret = 0;

        timer_stats_timer_set_start_info(timer);
        BUG_ON(!timer->function);

        base = lock_timer_base(timer, &flags);

        ret = detach_if_pending(timer, base, false);
        if (!ret && pending_only)
                goto out_unlock;

        debug_activate(timer, expires);

        new_base = get_target_base(base, pinned);

        if (base != new_base) {
                /*
                 * We are trying to schedule the timer on the local CPU.
                 * However we can't change timer's base while it is running,
                 * otherwise del_timer_sync() can't detect that the timer's
                 * handler yet has not finished. This also guarantees that
                 * the timer is serialized wrt itself.
                 */
                if (likely(base->running_timer != timer)) {
                        /* See the comment in lock_timer_base() */
                        timer->flags |= TIMER_MIGRATING;

                        spin_unlock(&base->lock);
                        base = new_base;
                        spin_lock(&base->lock);
                        WRITE_ONCE(timer->flags,
                                   (timer->flags & ~TIMER_BASEMASK) | base->cpu);
                }
        }

        timer->expires = expires;
        internal_add_timer(base, timer);

out_unlock:
        spin_unlock_irqrestore(&base->lock, flags);

        return ret;
}

/**
 * mod_timer_pending - modify a pending timer's timeout
 * @timer: the pending timer to be modified
 * @expires: new timeout in jiffies
 *
 * mod_timer_pending() is the same for pending timers as mod_timer(),
 * but will not re-activate and modify already deleted timers.
 *
 * It is useful for unserialized use of timers.
 */
int mod_timer_pending(struct timer_list *timer, unsigned long expires)
{
        return __mod_timer(timer, expires, true, TIMER_NOT_PINNED);
}
EXPORT_SYMBOL(mod_timer_pending);

/*
 * Decide where to put the timer while taking the slack into account
 *
 * Algorithm:
 *   1) calculate the maximum (absolute) time
 *   2) calculate the highest bit where the expires and new max are different
 *   3) use this bit to make a mask
 *   4) use the bitmask to round down the maximum time, so that all last
 *      bits are zeros
 */
static inline
unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
{
        unsigned long expires_limit, mask;
        int bit;

        if (timer->slack >= 0) {
                expires_limit = expires + timer->slack;
        } else {
                long delta = expires - jiffies;

                if (delta < 256)
                        return expires;

                expires_limit = expires + delta / 256;
        }
        mask = expires ^ expires_limit;
        if (mask == 0)
                return expires;

        bit = find_last_bit(&mask, BITS_PER_LONG);

        mask = (1UL << bit) - 1;

        expires_limit = expires_limit & ~(mask);

        return expires_limit;
}

/**
 * mod_timer - modify a timer's timeout
 * @timer: the timer to be modified
 * @expires: new timeout in jiffies
 *
 * mod_timer() is a more efficient way to update the expire field of an
 * active timer (if the timer is inactive it will be activated)
 *
 * mod_timer(timer, expires) is equivalent to:
 *
 *     del_timer(timer); timer->expires = expires; add_timer(timer);
 *
 * Note that if there are multiple unserialized concurrent users of the
 * same timer, then mod_timer() is the only safe way to modify the timeout,
 * since add_timer() cannot modify an already running timer.
 *
 * The function returns whether it has modified a pending timer or not.
 * (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
 * active timer returns 1.)
 */
int mod_timer(struct timer_list *timer, unsigned long expires)
{
        expires = apply_slack(timer, expires);

        /*
         * This is a common optimization triggered by the
         * networking code - if the timer is re-modified
         * to be the same thing then just return:
         */
        if (timer_pending(timer) && timer->expires == expires)
                return 1;

        return __mod_timer(timer, expires, false, TIMER_NOT_PINNED);
}
EXPORT_SYMBOL(mod_timer);

/**
 * mod_timer_pinned - modify a timer's timeout
 * @timer: the timer to be modified
 * @expires: new timeout in jiffies
 *
 * mod_timer_pinned() is a way to update the expire field of an
 * active timer (if the timer is inactive it will be activated)
 * and to ensure that the timer is scheduled on the current CPU.
 *
 * Note that this does not prevent the timer from being migrated
 * when the current CPU goes offline.  If this is a problem for
 * you, use CPU-hotplug notifiers to handle it correctly, for
 * example, cancelling the timer when the corresponding CPU goes
 * offline.
 *
 * mod_timer_pinned(timer, expires) is equivalent to:
 *
 *     del_timer(timer); timer->expires = expires; add_timer(timer);
 */
int mod_timer_pinned(struct timer_list *timer, unsigned long expires)
{
        if (timer->expires == expires && timer_pending(timer))
                return 1;

        return __mod_timer(timer, expires, false, TIMER_PINNED);
}
EXPORT_SYMBOL(mod_timer_pinned);

/**
 * add_timer - start a timer
 * @timer: the timer to be added
 *
 * The kernel will do a ->function(->data) callback from the
 * timer interrupt at the ->expires point in the future. The
 * current time is 'jiffies'.
 *
 * The timer's ->expires, ->function (and if the handler uses it, ->data)
 * fields must be set prior calling this function.
 *
 * Timers with an ->expires field in the past will be executed in the next
 * timer tick.
 */
void add_timer(struct timer_list *timer)
{
        BUG_ON(timer_pending(timer));
        mod_timer(timer, timer->expires);
}
EXPORT_SYMBOL(add_timer);

/**
 * add_timer_on - start a timer on a particular CPU
 * @timer: the timer to be added
 * @cpu: the CPU to start it on
 *
 * This is not very scalable on SMP. Double adds are not possible.
 */
void add_timer_on(struct timer_list *timer, int cpu)
{
        struct tvec_base *base = per_cpu_ptr(&tvec_bases, cpu);
        unsigned long flags;

        timer_stats_timer_set_start_info(timer);
        BUG_ON(timer_pending(timer) || !timer->function);
        spin_lock_irqsave(&base->lock, flags);
        timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
        debug_activate(timer, timer->expires);
        internal_add_timer(base, timer);
        spin_unlock_irqrestore(&base->lock, flags);
}
EXPORT_SYMBOL_GPL(add_timer_on);

/**
 * del_timer - deactive a timer.
 * @timer: the timer to be deactivated
 *
 * del_timer() deactivates a timer - this works on both active and inactive
 * timers.
 *
 * The function returns whether it has deactivated a pending timer or not.
 * (ie. del_timer() of an inactive timer returns 0, del_timer() of an
 * active timer returns 1.)
 */
int del_timer(struct timer_list *timer)
{
        struct tvec_base *base;
        unsigned long flags;
        int ret = 0;

        debug_assert_init(timer);

        timer_stats_timer_clear_start_info(timer);
        if (timer_pending(timer)) {
                base = lock_timer_base(timer, &flags);
                ret = detach_if_pending(timer, base, true);
                spin_unlock_irqrestore(&base->lock, flags);
        }

        return ret;
}
EXPORT_SYMBOL(del_timer);

/**
 * try_to_del_timer_sync - Try to deactivate a timer
 * @timer: timer do del
 *
 * This function tries to deactivate a timer. Upon successful (ret >= 0)
 * exit the timer is not queued and the handler is not running on any CPU.
 */
int try_to_del_timer_sync(struct timer_list *timer)
{
        struct tvec_base *base;
        unsigned long flags;
        int ret = -1;

        debug_assert_init(timer);

        base = lock_timer_base(timer, &flags);

        if (base->running_timer != timer) {
                timer_stats_timer_clear_start_info(timer);
                ret = detach_if_pending(timer, base, true);
        }
        spin_unlock_irqrestore(&base->lock, flags);

        return ret;
}
EXPORT_SYMBOL(try_to_del_timer_sync);

#ifdef CONFIG_SMP
/**
 * del_timer_sync - deactivate a timer and wait for the handler to finish.
 * @timer: the timer to be deactivated
 *
 * This function only differs from del_timer() on SMP: besides deactivating
 * the timer it also makes sure the handler has finished executing on other
 * CPUs.
 *
 * Synchronization rules: Callers must prevent restarting of the timer,
 * otherwise this function is meaningless. It must not be called from
 * interrupt contexts unless the timer is an irqsafe one. The caller must
 * not hold locks which would prevent completion of the timer's
 * handler. The timer's handler must not call add_timer_on(). Upon exit the
 * timer is not queued and the handler is not running on any CPU.
 *
 * Note: For !irqsafe timers, you must not hold locks that are held in
 *   interrupt context while calling this function. Even if the lock has
 *   nothing to do with the timer in question.  Here's why:
 *
 *    CPU0                             CPU1
 *    ----                             ----
 *                                   <SOFTIRQ>
 *                                   call_timer_fn();
 *                                     base->running_timer = mytimer;
 *  spin_lock_irq(somelock);
 *                                     <IRQ>
 *                                        spin_lock(somelock);
 *  del_timer_sync(mytimer);
 *   while (base->running_timer == mytimer);
 *
 * Now del_timer_sync() will never return and never release somelock.
 * The interrupt on the other CPU is waiting to grab somelock but
 * it has interrupted the softirq that CPU0 is waiting to finish.
 *
 * The function returns whether it has deactivated a pending timer or not.
 */
int del_timer_sync(struct timer_list *timer)
{
#ifdef CONFIG_LOCKDEP
        unsigned long flags;

        /*
         * If lockdep gives a backtrace here, please reference
         * the synchronization rules above.
         */
        local_irq_save(flags);
        lock_map_acquire(&timer->lockdep_map);
        lock_map_release(&timer->lockdep_map);
        local_irq_restore(flags);
#endif
        /*
         * don't use it in hardirq context, because it
         * could lead to deadlock.
         */
        WARN_ON(in_irq() && !(timer->flags & TIMER_IRQSAFE));
        for (;;) {
                int ret = try_to_del_timer_sync(timer);
                if (ret >= 0)
                        return ret;
                cpu_relax();
        }
}
EXPORT_SYMBOL(del_timer_sync);
#endif

static int cascade(struct tvec_base *base, struct tvec *tv, int index)
{
        /* cascade all the timers from tv up one level */
        struct timer_list *timer;
        struct hlist_node *tmp;
        struct hlist_head tv_list;

        hlist_move_list(tv->vec + index, &tv_list);

        /*
         * We are removing _all_ timers from the list, so we
         * don't have to detach them individually.
         */
        hlist_for_each_entry_safe(timer, tmp, &tv_list, entry) {
                /* No accounting, while moving them */
                __internal_add_timer(base, timer);
        }

        return index;
}

static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long),
                          unsigned long data)
{
        int count = preempt_count();

#ifdef CONFIG_LOCKDEP
        /*
         * It is permissible to free the timer from inside the
         * function that is called from it, this we need to take into
         * account for lockdep too. To avoid bogus "held lock freed"
         * warnings as well as problems when looking into
         * timer->lockdep_map, make a copy and use that here.
         */
        struct lockdep_map lockdep_map;

        lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
#endif
        /*
         * Couple the lock chain with the lock chain at
         * del_timer_sync() by acquiring the lock_map around the fn()
         * call here and in del_timer_sync().
         */
        lock_map_acquire(&lockdep_map);

        trace_timer_expire_entry(timer);
        fn(data);
        trace_timer_expire_exit(timer);

        lock_map_release(&lockdep_map);

        if (count != preempt_count()) {
                WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x\n",
                          fn, count, preempt_count());
                /*
                 * Restore the preempt count. That gives us a decent
                 * chance to survive and extract information. If the
                 * callback kept a lock held, bad luck, but not worse
                 * than the BUG() we had.
                 */
                preempt_count_set(count);
        }
}

#define INDEX(N) ((base->timer_jiffies >> (TVR_BITS + (N) * TVN_BITS)) & TVN_MASK)

/**
 * __run_timers - run all expired timers (if any) on this CPU.
 * @base: the timer vector to be processed.
 *
 * This function cascades all vectors and executes all expired timer
 * vectors.
 */
static inline void __run_timers(struct tvec_base *base)
{
        struct timer_list *timer;

        spin_lock_irq(&base->lock);

        while (time_after_eq(jiffies, base->timer_jiffies)) {
                struct hlist_head work_list;
                struct hlist_head *head = &work_list;
                int index;

                if (!base->all_timers) {
                        base->timer_jiffies = jiffies;
                        break;
                }

                index = base->timer_jiffies & TVR_MASK;

                /*
                 * Cascade timers:
                 */
                if (!index &&
                        (!cascade(base, &base->tv2, INDEX(0))) &&
                                (!cascade(base, &base->tv3, INDEX(1))) &&
                                        !cascade(base, &base->tv4, INDEX(2)))
                        cascade(base, &base->tv5, INDEX(3));
                ++base->timer_jiffies;
                hlist_move_list(base->tv1.vec + index, head);
                while (!hlist_empty(head)) {
                        void (*fn)(unsigned long);
                        unsigned long data;
                        bool irqsafe;

                        timer = hlist_entry(head->first, struct timer_list, entry);
                        fn = timer->function;
                        data = timer->data;
                        irqsafe = timer->flags & TIMER_IRQSAFE;

                        timer_stats_account_timer(timer);

                        base->running_timer = timer;
                        detach_expired_timer(timer, base);

                        if (irqsafe) {
                                spin_unlock(&base->lock);
                                call_timer_fn(timer, fn, data);
                                spin_lock(&base->lock);
                        } else {
                                spin_unlock_irq(&base->lock);
                                call_timer_fn(timer, fn, data);
                                spin_lock_irq(&base->lock);
                        }
                }
        }
        base->running_timer = NULL;
        spin_unlock_irq(&base->lock);
}

#ifdef CONFIG_NO_HZ_COMMON
/*
 * Find out when the next timer event is due to happen. This
 * is used on S/390 to stop all activity when a CPU is idle.
 * This function needs to be called with interrupts disabled.
 */
static unsigned long __next_timer_interrupt(struct tvec_base *base)
{
        unsigned long timer_jiffies = base->timer_jiffies;
        unsigned long expires = timer_jiffies + NEXT_TIMER_MAX_DELTA;
        int index, slot, array, found = 0;
        struct timer_list *nte;
        struct tvec *varray[4];

        /* Look for timer events in tv1. */
        index = slot = timer_jiffies & TVR_MASK;
        do {
                hlist_for_each_entry(nte, base->tv1.vec + slot, entry) {
                        if (nte->flags & TIMER_DEFERRABLE)
                                continue;

                        found = 1;
                        expires = nte->expires;
                        /* Look at the cascade bucket(s)? */
                        if (!index || slot < index)
                                goto cascade;
                        return expires;
                }
                slot = (slot + 1) & TVR_MASK;
        } while (slot != index);

cascade:
        /* Calculate the next cascade event */
        if (index)
                timer_jiffies += TVR_SIZE - index;
        timer_jiffies >>= TVR_BITS;

        /* Check tv2-tv5. */
        varray[0] = &base->tv2;
        varray[1] = &base->tv3;
        varray[2] = &base->tv4;
        varray[3] = &base->tv5;

        for (array = 0; array < 4; array++) {
                struct tvec *varp = varray[array];

                index = slot = timer_jiffies & TVN_MASK;
                do {
                        hlist_for_each_entry(nte, varp->vec + slot, entry) {
                                if (nte->flags & TIMER_DEFERRABLE)
                                        continue;

                                found = 1;
                                if (time_before(nte->expires, expires))
                                        expires = nte->expires;
                        }
                        /*
                         * Do we still search for the first timer or are
                         * we looking up the cascade buckets ?
                         */
                        if (found) {
                                /* Look at the cascade bucket(s)? */
                                if (!index || slot < index)
                                        break;
                                return expires;
                        }
                        slot = (slot + 1) & TVN_MASK;
                } while (slot != index);

                if (index)
                        timer_jiffies += TVN_SIZE - index;
                timer_jiffies >>= TVN_BITS;
        }
        return expires;
}

/*
 * Check, if the next hrtimer event is before the next timer wheel
 * event:
 */
static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
{
        u64 nextevt = hrtimer_get_next_event();

        /*
         * If high resolution timers are enabled
         * hrtimer_get_next_event() returns KTIME_MAX.
         */
        if (expires <= nextevt)
                return expires;

        /*
         * If the next timer is already expired, return the tick base
         * time so the tick is fired immediately.
         */
        if (nextevt <= basem)
                return basem;

        /*
         * Round up to the next jiffie. High resolution timers are
         * off, so the hrtimers are expired in the tick and we need to
         * make sure that this tick really expires the timer to avoid
         * a ping pong of the nohz stop code.
         *
         * Use DIV_ROUND_UP_ULL to prevent gcc calling __divdi3
         */
        return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
}

/**
 * get_next_timer_interrupt - return the time (clock mono) of the next timer
 * @basej:      base time jiffies
 * @basem:      base time clock monotonic
 *
 * Returns the tick aligned clock monotonic time of the next pending
 * timer or KTIME_MAX if no timer is pending.
 */
u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
{
        struct tvec_base *base = this_cpu_ptr(&tvec_bases);
        u64 expires = KTIME_MAX;
        unsigned long nextevt;

        /*
         * Pretend that there is no timer pending if the cpu is offline.
         * Possible pending timers will be migrated later to an active cpu.
         */
        if (cpu_is_offline(smp_processor_id()))
                return expires;

        spin_lock(&base->lock);
        if (base->active_timers) {
                if (time_before_eq(base->next_timer, base->timer_jiffies))
                        base->next_timer = __next_timer_interrupt(base);
                nextevt = base->next_timer;
                if (time_before_eq(nextevt, basej))
                        expires = basem;
                else
                        expires = basem + (nextevt - basej) * TICK_NSEC;
        }
        spin_unlock(&base->lock);

        return cmp_next_hrtimer_event(basem, expires);
}
#endif

/*
 * Called from the timer interrupt handler to charge one tick to the current
 * process.  user_tick is 1 if the tick is user time, 0 for system.
 */
void update_process_times(int user_tick)
{
        struct task_struct *p = current;

        /* Note: this timer irq context must be accounted for as well. */
        account_process_tick(p, user_tick);
        run_local_timers();
        rcu_check_callbacks(user_tick);
#ifdef CONFIG_IRQ_WORK
        if (in_irq())
                irq_work_tick();
#endif
        scheduler_tick();
        run_posix_cpu_timers(p);
}

/*
 * This function runs timers and the timer-tq in bottom half context.
 */
static void run_timer_softirq(struct softirq_action *h)
{
        struct tvec_base *base = this_cpu_ptr(&tvec_bases);

        if (time_after_eq(jiffies, base->timer_jiffies))
                __run_timers(base);
}

/*
 * Called by the local, per-CPU timer interrupt on SMP.
 */
void run_local_timers(void)
{
        hrtimer_run_queues();
        raise_softirq(TIMER_SOFTIRQ);
}

#ifdef __ARCH_WANT_SYS_ALARM

/*
 * For backwards compatibility?  This can be done in libc so Alpha
 * and all newer ports shouldn't need it.
 */
SYSCALL_DEFINE1(alarm, unsigned int, seconds)
{
        return alarm_setitimer(seconds);
}

#endif

static void process_timeout(unsigned long __data)
{
        wake_up_process((struct task_struct *)__data);
}

/**
 * schedule_timeout - sleep until timeout
 * @timeout: timeout value in jiffies
 *
 * Make the current task sleep until @timeout jiffies have
 * elapsed. The routine will return immediately unless
 * the current task state has been set (see set_current_state()).
 *
 * You can set the task state as follows -
 *
 * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
 * pass before the routine returns. The routine will return 0
 *
 * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
 * delivered to the current task. In this case the remaining time
 * in jiffies will be returned, or 0 if the timer expired in time
 *
 * The current task state is guaranteed to be TASK_RUNNING when this
 * routine returns.
 *
 * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
 * the CPU away without a bound on the timeout. In this case the return
 * value will be %MAX_SCHEDULE_TIMEOUT.
 *
 * In all cases the return value is guaranteed to be non-negative.
 */
signed long __sched schedule_timeout(signed long timeout)
{
        struct timer_list timer;
        unsigned long expire;

        switch (timeout)
        {
        case MAX_SCHEDULE_TIMEOUT:
                /*
                 * These two special cases are useful to be comfortable
                 * in the caller. Nothing more. We could take
                 * MAX_SCHEDULE_TIMEOUT from one of the negative value
                 * but I' d like to return a valid offset (>=0) to allow
                 * the caller to do everything it want with the retval.
                 */
                schedule();
                goto out;
        default:
                /*
                 * Another bit of PARANOID. Note that the retval will be
                 * 0 since no piece of kernel is supposed to do a check
                 * for a negative retval of schedule_timeout() (since it
                 * should never happens anyway). You just have the printk()
                 * that will tell you if something is gone wrong and where.
                 */
                if (timeout < 0) {
                        printk(KERN_ERR "schedule_timeout: wrong timeout "
                                "value %lx\n", timeout);
                        dump_stack();
                        current->state = TASK_RUNNING;
                        goto out;
                }
        }

        expire = timeout + jiffies;

        setup_timer_on_stack(&timer, process_timeout, (unsigned long)current);
        __mod_timer(&timer, expire, false, TIMER_NOT_PINNED);
        schedule();
        del_singleshot_timer_sync(&timer);

        /* Remove the timer from the object tracker */
        destroy_timer_on_stack(&timer);

        timeout = expire - jiffies;

 out:
        return timeout < 0 ? 0 : timeout;
}
EXPORT_SYMBOL(schedule_timeout);

/*
 * We can use __set_current_state() here because schedule_timeout() calls
 * schedule() unconditionally.
 */
signed long __sched schedule_timeout_interruptible(signed long timeout)
{
        __set_current_state(TASK_INTERRUPTIBLE);
        return schedule_timeout(timeout);
}
EXPORT_SYMBOL(schedule_timeout_interruptible);

signed long __sched schedule_timeout_killable(signed long timeout)
{
        __set_current_state(TASK_KILLABLE);
        return schedule_timeout(timeout);
}
EXPORT_SYMBOL(schedule_timeout_killable);

signed long __sched schedule_timeout_uninterruptible(signed long timeout)
{
        __set_current_state(TASK_UNINTERRUPTIBLE);
        return schedule_timeout(timeout);
}
EXPORT_SYMBOL(schedule_timeout_uninterruptible);

#ifdef CONFIG_HOTPLUG_CPU
static void migrate_timer_list(struct tvec_base *new_base, struct hlist_head *head)
{
        struct timer_list *timer;
        int cpu = new_base->cpu;

        while (!hlist_empty(head)) {
                timer = hlist_entry(head->first, struct timer_list, entry);
                /* We ignore the accounting on the dying cpu */
                detach_timer(timer, false);
                timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
                internal_add_timer(new_base, timer);
        }
}

static void migrate_timers(int cpu)
{
        struct tvec_base *old_base;
        struct tvec_base *new_base;
        int i;

        BUG_ON(cpu_online(cpu));
        old_base = per_cpu_ptr(&tvec_bases, cpu);
        new_base = get_cpu_ptr(&tvec_bases);
        /*
         * The caller is globally serialized and nobody else
         * takes two locks at once, deadlock is not possible.
         */
        spin_lock_irq(&new_base->lock);
        spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);

        BUG_ON(old_base->running_timer);

        for (i = 0; i < TVR_SIZE; i++)
                migrate_timer_list(new_base, old_base->tv1.vec + i);
        for (i = 0; i < TVN_SIZE; i++) {
                migrate_timer_list(new_base, old_base->tv2.vec + i);
                migrate_timer_list(new_base, old_base->tv3.vec + i);
                migrate_timer_list(new_base, old_base->tv4.vec + i);
                migrate_timer_list(new_base, old_base->tv5.vec + i);
        }

        old_base->active_timers = 0;
        old_base->all_timers = 0;

        spin_unlock(&old_base->lock);
        spin_unlock_irq(&new_base->lock);
        put_cpu_ptr(&tvec_bases);
}

static int timer_cpu_notify(struct notifier_block *self,
                                unsigned long action, void *hcpu)
{
        switch (action) {
        case CPU_DEAD:
        case CPU_DEAD_FROZEN:
                migrate_timers((long)hcpu);
                break;
        default:
                break;
        }

        return NOTIFY_OK;
}

static inline void timer_register_cpu_notifier(void)
{
        cpu_notifier(timer_cpu_notify, 0);
}
#else
static inline void timer_register_cpu_notifier(void) { }
#endif /* CONFIG_HOTPLUG_CPU */

static void __init init_timer_cpu(int cpu)
{
        struct tvec_base *base = per_cpu_ptr(&tvec_bases, cpu);

        base->cpu = cpu;
        spin_lock_init(&base->lock);

        base->timer_jiffies = jiffies;
        base->next_timer = base->timer_jiffies;
}

static void __init init_timer_cpus(void)
{
        int cpu;

        for_each_possible_cpu(cpu)
                init_timer_cpu(cpu);
}

void __init init_timers(void)
{
        init_timer_cpus();
        init_timer_stats();
        timer_register_cpu_notifier();
        open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
}

/**
 * msleep - sleep safely even with waitqueue interruptions
 * @msecs: Time in milliseconds to sleep for
 */
void msleep(unsigned int msecs)
{
        unsigned long timeout = msecs_to_jiffies(msecs) + 1;

        while (timeout)
                timeout = schedule_timeout_uninterruptible(timeout);
}

EXPORT_SYMBOL(msleep);

/**
 * msleep_interruptible - sleep waiting for signals
 * @msecs: Time in milliseconds to sleep for
 */
unsigned long msleep_interruptible(unsigned int msecs)
{
        unsigned long timeout = msecs_to_jiffies(msecs) + 1;

        while (timeout && !signal_pending(current))
                timeout = schedule_timeout_interruptible(timeout);
        return jiffies_to_msecs(timeout);
}

EXPORT_SYMBOL(msleep_interruptible);

static void __sched do_usleep_range(unsigned long min, unsigned long max)
{
        ktime_t kmin;
        unsigned long delta;

        kmin = ktime_set(0, min * NSEC_PER_USEC);
        delta = (max - min) * NSEC_PER_USEC;
        schedule_hrtimeout_range(&kmin, delta, HRTIMER_MODE_REL);
}

/**
 * usleep_range - Drop in replacement for udelay where wakeup is flexible
 * @min: Minimum time in usecs to sleep
 * @max: Maximum time in usecs to sleep
 */
void __sched usleep_range(unsigned long min, unsigned long max)
{
        __set_current_state(TASK_UNINTERRUPTIBLE);
        do_usleep_range(min, max);
}
EXPORT_SYMBOL(usleep_range);