hrtimer.c

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/*
 *  linux/kernel/hrtimer.c
 *
 *  Copyright(C) 2005-2006, Thomas Gleixner <[email protected]>
 *  Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
 *  Copyright(C) 2006-2007  Timesys Corp., Thomas Gleixner
 *
 *  High-resolution kernel timers
 *
 *  In contrast to the low-resolution timeout API implemented in
 *  kernel/timer.c, hrtimers provide finer resolution and accuracy
 *  depending on system configuration and capabilities.
 *
 *  These timers are currently used for:
 *   - itimers
 *   - POSIX timers
 *   - nanosleep
 *   - precise in-kernel timing
 *
 *  Started by: Thomas Gleixner and Ingo Molnar
 *
 *  Credits:
 *  based on kernel/timer.c
 *
 *  Help, testing, suggestions, bugfixes, improvements were
 *  provided by:
 *
 *  George Anzinger, Andrew Morton, Steven Rostedt, Roman Zippel
 *  et. al.
 *
 *  For licencing details see kernel-base/COPYING
 */

#include <linux/cpu.h>
#include <linux/export.h>
#include <linux/percpu.h>
#include <linux/hrtimer.h>
#include <linux/notifier.h>
#include <linux/syscalls.h>
#include <linux/kallsyms.h>
#include <linux/interrupt.h>
#include <linux/tick.h>
#include <linux/seq_file.h>
#include <linux/err.h>
#include <linux/debugobjects.h>
#include <linux/sched.h>
#include <linux/timer.h>

#include <asm/uaccess.h>

#include <trace/events/timer.h>

/*
 * The timer bases:
 *
 * There are more clockids then hrtimer bases. Thus, we index
 * into the timer bases by the hrtimer_base_type enum. When trying
 * to reach a base using a clockid, hrtimer_clockid_to_base()
 * is used to convert from clockid to the proper hrtimer_base_type.
 */
DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
{

    .clock_base =
    {
        {
            .index = HRTIMER_BASE_MONOTONIC,
            .clockid = CLOCK_MONOTONIC,
            .get_time = &ktime_get,
            .resolution = KTIME_LOW_RES,
        },
        {
            .index = HRTIMER_BASE_REALTIME,
            .clockid = CLOCK_REALTIME,
            .get_time = &ktime_get_real,
            .resolution = KTIME_LOW_RES,
        },
        {
            .index = HRTIMER_BASE_BOOTTIME,
            .clockid = CLOCK_BOOTTIME,
            .get_time = &ktime_get_boottime,
            .resolution = KTIME_LOW_RES,
        },
    }
};

static const int hrtimer_clock_to_base_table[MAX_CLOCKS] = {
    [CLOCK_REALTIME]    = HRTIMER_BASE_REALTIME,
    [CLOCK_MONOTONIC]   = HRTIMER_BASE_MONOTONIC,
    [CLOCK_BOOTTIME]    = HRTIMER_BASE_BOOTTIME,
};

static inline int hrtimer_clockid_to_base(clockid_t clock_id)
{
    return hrtimer_clock_to_base_table[clock_id];
}


/*
 * Get the coarse grained time at the softirq based on xtime and
 * wall_to_monotonic.
 */
static void hrtimer_get_softirq_time(struct hrtimer_cpu_base *base)
{
    ktime_t xtim, mono, boot;
    struct timespec xts, tom, slp;

    get_xtime_and_monotonic_and_sleep_offset(&xts, &tom, &slp);

    xtim = timespec_to_ktime(xts);
    mono = ktime_add(xtim, timespec_to_ktime(tom));
    boot = ktime_add(mono, timespec_to_ktime(slp));
    base->clock_base[HRTIMER_BASE_REALTIME].softirq_time = xtim;
    base->clock_base[HRTIMER_BASE_MONOTONIC].softirq_time = mono;
    base->clock_base[HRTIMER_BASE_BOOTTIME].softirq_time = boot;
}

/*
 * Functions and macros which are different for UP/SMP systems are kept in a
 * single place
 */
#ifdef CONFIG_SMP

/*
 * We are using hashed locking: holding per_cpu(hrtimer_bases)[n].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 the lists/queues.
 *
 * When the timer's base is locked, and the timer removed from list, it is
 * possible to set timer->base = NULL and drop the lock: the timer remains
 * locked.
 */
static
struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
                         unsigned long *flags)
{
    struct hrtimer_clock_base *base;

    for (;;) {
        base = timer->base;
        if (likely(base != NULL)) {
            raw_spin_lock_irqsave(&base->cpu_base->lock, *flags);
            if (likely(base == timer->base))
                return base;
            /* The timer has migrated to another CPU: */
            raw_spin_unlock_irqrestore(&base->cpu_base->lock, *flags);
        }
        cpu_relax();
    }
}


/*
 * Get the preferred target CPU for NOHZ
 */
static int hrtimer_get_target(int this_cpu, int pinned)
{
#ifdef CONFIG_NO_HZ
    if (!pinned && get_sysctl_timer_migration() && idle_cpu(this_cpu))
        return get_nohz_timer_target();
#endif
    return this_cpu;
}

/*
 * With HIGHRES=y we do not migrate the timer when it is expiring
 * before the next event on the target cpu because we cannot reprogram
 * the target cpu hardware and we would cause it to fire late.
 *
 * Called with cpu_base->lock of target cpu held.
 */
static int
hrtimer_check_target(struct hrtimer *timer, struct hrtimer_clock_base *new_base)
{
#ifdef CONFIG_HIGH_RES_TIMERS
    ktime_t expires;

    if (!new_base->cpu_base->hres_active)
        return 0;

    expires = ktime_sub(hrtimer_get_expires(timer), new_base->offset);
    return expires.tv64 <= new_base->cpu_base->expires_next.tv64;
#else
    return 0;
#endif
}

/*
 * Switch the timer base to the current CPU when possible.
 */
static inline struct hrtimer_clock_base *
switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base,
            int pinned)
{
    struct hrtimer_clock_base *new_base;
    struct hrtimer_cpu_base *new_cpu_base;
    int this_cpu = smp_processor_id();
    int cpu = hrtimer_get_target(this_cpu, pinned);
    int basenum = base->index;

again:
    new_cpu_base = &per_cpu(hrtimer_bases, cpu);
    new_base = &new_cpu_base->clock_base[basenum];

    if (base != new_base) {
        /*
         * We are trying to move timer to new_base.
         * However we can't change timer's base while it is running,
         * so we keep it on the same CPU. No hassle vs. reprogramming
         * the event source in the high resolution case. The softirq
         * code will take care of this when the timer function has
         * completed. There is no conflict as we hold the lock until
         * the timer is enqueued.
         */
        if (unlikely(hrtimer_callback_running(timer)))
            return base;

        /* See the comment in lock_timer_base() */
        timer->base = NULL;
        raw_spin_unlock(&base->cpu_base->lock);
        raw_spin_lock(&new_base->cpu_base->lock);

        if (cpu != this_cpu && hrtimer_check_target(timer, new_base)) {
            cpu = this_cpu;
            raw_spin_unlock(&new_base->cpu_base->lock);
            raw_spin_lock(&base->cpu_base->lock);
            timer->base = base;
            goto again;
        }
        timer->base = new_base;
    }
    return new_base;
}

#else /* CONFIG_SMP */

static inline struct hrtimer_clock_base *
lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
{
    struct hrtimer_clock_base *base = timer->base;

    raw_spin_lock_irqsave(&base->cpu_base->lock, *flags);

    return base;
}

# define switch_hrtimer_base(t, b, p)   (b)

#endif  /* !CONFIG_SMP */

/*
 * Functions for the union type storage format of ktime_t which are
 * too large for inlining:
 */
#if BITS_PER_LONG < 64
# ifndef CONFIG_KTIME_SCALAR

ktime_t ktime_add_ns(const ktime_t kt, u64 nsec)
{
    ktime_t tmp;

    if (likely(nsec < NSEC_PER_SEC)) {
        tmp.tv64 = nsec;
    } else {
        unsigned long rem = do_div(nsec, NSEC_PER_SEC);

        tmp = ktime_set((long)nsec, rem);
    }

    return ktime_add(kt, tmp);
}

EXPORT_SYMBOL_GPL(ktime_add_ns);

ktime_t ktime_sub_ns(const ktime_t kt, u64 nsec)
{
    ktime_t tmp;

    if (likely(nsec < NSEC_PER_SEC)) {
        tmp.tv64 = nsec;
    } else {
        unsigned long rem = do_div(nsec, NSEC_PER_SEC);

        tmp = ktime_set((long)nsec, rem);
    }

    return ktime_sub(kt, tmp);
}

EXPORT_SYMBOL_GPL(ktime_sub_ns);
# endif /* !CONFIG_KTIME_SCALAR */

/*
 * Divide a ktime value by a nanosecond value
 */
u64 ktime_divns(const ktime_t kt, s64 div)
{
    u64 dclc;
    int sft = 0;

    dclc = ktime_to_ns(kt);
    /* Make sure the divisor is less than 2^32: */
    while (div >> 32) {
        sft++;
        div >>= 1;
    }
    dclc >>= sft;
    do_div(dclc, (unsigned long) div);

    return dclc;
}
#endif /* BITS_PER_LONG >= 64 */

/*
 * Add two ktime values and do a safety check for overflow:
 */
ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs)
{
    ktime_t res = ktime_add(lhs, rhs);

    /*
     * We use KTIME_SEC_MAX here, the maximum timeout which we can
     * return to user space in a timespec:
     */
    if (res.tv64 < 0 || res.tv64 < lhs.tv64 || res.tv64 < rhs.tv64)
        res = ktime_set(KTIME_SEC_MAX, 0);

    return res;
}

EXPORT_SYMBOL_GPL(ktime_add_safe);

#ifdef CONFIG_DEBUG_OBJECTS_TIMERS

static struct debug_obj_descr hrtimer_debug_descr;

static void *hrtimer_debug_hint(void *addr)
{
    return ((struct hrtimer *) addr)->function;
}

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

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

/*
 * fixup_activate is called when:
 * - an active object is activated
 * - an unknown object is activated (might be a statically initialized object)
 */
static int hrtimer_fixup_activate(void *addr, enum debug_obj_state state)
{
    switch (state) {

    case ODEBUG_STATE_NOTAVAILABLE:
        WARN_ON_ONCE(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 hrtimer_fixup_free(void *addr, enum debug_obj_state state)
{
    struct hrtimer *timer = addr;

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

static struct debug_obj_descr hrtimer_debug_descr = {
    .name       = "hrtimer",
    .debug_hint = hrtimer_debug_hint,
    .fixup_init = hrtimer_fixup_init,
    .fixup_activate = hrtimer_fixup_activate,
    .fixup_free = hrtimer_fixup_free,
};

static inline void debug_hrtimer_init(struct hrtimer *timer)
{
    debug_object_init(timer, &hrtimer_debug_descr);
}

static inline void debug_hrtimer_activate(struct hrtimer *timer)
{
    debug_object_activate(timer, &hrtimer_debug_descr);
}

static inline void debug_hrtimer_deactivate(struct hrtimer *timer)
{
    debug_object_deactivate(timer, &hrtimer_debug_descr);
}

static inline void debug_hrtimer_free(struct hrtimer *timer)
{
    debug_object_free(timer, &hrtimer_debug_descr);
}

static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
               enum hrtimer_mode mode);

void hrtimer_init_on_stack(struct hrtimer *timer, clockid_t clock_id,
               enum hrtimer_mode mode)
{
    debug_object_init_on_stack(timer, &hrtimer_debug_descr);
    __hrtimer_init(timer, clock_id, mode);
}
EXPORT_SYMBOL_GPL(hrtimer_init_on_stack);

void destroy_hrtimer_on_stack(struct hrtimer *timer)
{
    debug_object_free(timer, &hrtimer_debug_descr);
}

#else
static inline void debug_hrtimer_init(struct hrtimer *timer) { }
static inline void debug_hrtimer_activate(struct hrtimer *timer) { }
static inline void debug_hrtimer_deactivate(struct hrtimer *timer) { }
#endif

static inline void
debug_init(struct hrtimer *timer, clockid_t clockid,
       enum hrtimer_mode mode)
{
    debug_hrtimer_init(timer);
    trace_hrtimer_init(timer, clockid, mode);
}

static inline void debug_activate(struct hrtimer *timer)
{
    debug_hrtimer_activate(timer);
    trace_hrtimer_start(timer);
}

static inline void debug_deactivate(struct hrtimer *timer)
{
    debug_hrtimer_deactivate(timer);
    trace_hrtimer_cancel(timer);
}

/* High resolution timer related functions */
#ifdef CONFIG_HIGH_RES_TIMERS

/*
 * High resolution timer enabled ?
 */
static int hrtimer_hres_enabled __read_mostly  = 1;

/*
 * Enable / Disable high resolution mode
 */
static int __init setup_hrtimer_hres(char *str)
{
    if (!strcmp(str, "off"))
        hrtimer_hres_enabled = 0;
    else if (!strcmp(str, "on"))
        hrtimer_hres_enabled = 1;
    else
        return 0;
    return 1;
}

__setup("highres=", setup_hrtimer_hres);

/*
 * hrtimer_high_res_enabled - query, if the highres mode is enabled
 */
static inline int hrtimer_is_hres_enabled(void)
{
    return hrtimer_hres_enabled;
}

/*
 * Is the high resolution mode active ?
 */
static inline int hrtimer_hres_active(void)
{
    return __this_cpu_read(hrtimer_bases.hres_active);
}

/*
 * Reprogram the event source with checking both queues for the
 * next event
 * Called with interrupts disabled and base->lock held
 */
static void
hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
{
    int i;
    struct hrtimer_clock_base *base = cpu_base->clock_base;
    ktime_t expires, expires_next;

    expires_next.tv64 = KTIME_MAX;

    for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++, base++) {
        struct hrtimer *timer;
        struct timerqueue_node *next;

        next = timerqueue_getnext(&base->active);
        if (!next)
            continue;
        timer = container_of(next, struct hrtimer, node);

        expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
        /*
         * clock_was_set() has changed base->offset so the
         * result might be negative. Fix it up to prevent a
         * false positive in clockevents_program_event()
         */
        if (expires.tv64 < 0)
            expires.tv64 = 0;
        if (expires.tv64 < expires_next.tv64)
            expires_next = expires;
    }

    if (skip_equal && expires_next.tv64 == cpu_base->expires_next.tv64)
        return;

    cpu_base->expires_next.tv64 = expires_next.tv64;

    if (cpu_base->expires_next.tv64 != KTIME_MAX)
        tick_program_event(cpu_base->expires_next, 1);
}

/*
 * Shared reprogramming for clock_realtime and clock_monotonic
 *
 * When a timer is enqueued and expires earlier than the already enqueued
 * timers, we have to check, whether it expires earlier than the timer for
 * which the clock event device was armed.
 *
 * Called with interrupts disabled and base->cpu_base.lock held
 */
static int hrtimer_reprogram(struct hrtimer *timer,
                 struct hrtimer_clock_base *base)
{
    struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
    ktime_t expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
    int res;

    WARN_ON_ONCE(hrtimer_get_expires_tv64(timer) < 0);

    /*
     * When the callback is running, we do not reprogram the clock event
     * device. The timer callback is either running on a different CPU or
     * the callback is executed in the hrtimer_interrupt context. The
     * reprogramming is handled either by the softirq, which called the
     * callback or at the end of the hrtimer_interrupt.
     */
    if (hrtimer_callback_running(timer))
        return 0;

    /*
     * CLOCK_REALTIME timer might be requested with an absolute
     * expiry time which is less than base->offset. Nothing wrong
     * about that, just avoid to call into the tick code, which
     * has now objections against negative expiry values.
     */
    if (expires.tv64 < 0)
        return -ETIME;

    if (expires.tv64 >= cpu_base->expires_next.tv64)
        return 0;

    /*
     * If a hang was detected in the last timer interrupt then we
     * do not schedule a timer which is earlier than the expiry
     * which we enforced in the hang detection. We want the system
     * to make progress.
     */
    if (cpu_base->hang_detected)
        return 0;

    /*
     * Clockevents returns -ETIME, when the event was in the past.
     */
    res = tick_program_event(expires, 0);
    if (!IS_ERR_VALUE(res))
        cpu_base->expires_next = expires;
    return res;
}

/*
 * Initialize the high resolution related parts of cpu_base
 */
static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base)
{
    base->expires_next.tv64 = KTIME_MAX;
    base->hres_active = 0;
}

/*
 * When High resolution timers are active, try to reprogram. Note, that in case
 * the state has HRTIMER_STATE_CALLBACK set, no reprogramming and no expiry
 * check happens. The timer gets enqueued into the rbtree. The reprogramming
 * and expiry check is done in the hrtimer_interrupt or in the softirq.
 */
static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
                        struct hrtimer_clock_base *base,
                        int wakeup)
{
    if (base->cpu_base->hres_active && hrtimer_reprogram(timer, base)) {
        if (wakeup) {
            raw_spin_unlock(&base->cpu_base->lock);
            raise_softirq_irqoff(HRTIMER_SOFTIRQ);
            raw_spin_lock(&base->cpu_base->lock);
        } else
            __raise_softirq_irqoff(HRTIMER_SOFTIRQ);

        return 1;
    }

    return 0;
}

static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base)
{
    ktime_t *offs_real = &base->clock_base[HRTIMER_BASE_REALTIME].offset;
    ktime_t *offs_boot = &base->clock_base[HRTIMER_BASE_BOOTTIME].offset;

    return ktime_get_update_offsets(offs_real, offs_boot);
}

/*
 * Retrigger next event is called after clock was set
 *
 * Called with interrupts disabled via on_each_cpu()
 */
static void retrigger_next_event(void *arg)
{
    struct hrtimer_cpu_base *base = &__get_cpu_var(hrtimer_bases);

    if (!hrtimer_hres_active())
        return;

    raw_spin_lock(&base->lock);
    hrtimer_update_base(base);
    hrtimer_force_reprogram(base, 0);
    raw_spin_unlock(&base->lock);
}

/*
 * Switch to high resolution mode
 */
static int hrtimer_switch_to_hres(void)
{
    int i, cpu = smp_processor_id();
    struct hrtimer_cpu_base *base = &per_cpu(hrtimer_bases, cpu);
    unsigned long flags;

    if (base->hres_active)
        return 1;

    local_irq_save(flags);

    if (tick_init_highres()) {
        local_irq_restore(flags);
        printk(KERN_WARNING "Could not switch to high resolution "
                    "mode on CPU %d\n", cpu);
        return 0;
    }
    base->hres_active = 1;
    for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)
        base->clock_base[i].resolution = KTIME_HIGH_RES;

    tick_setup_sched_timer();
    /* "Retrigger" the interrupt to get things going */
    retrigger_next_event(NULL);
    local_irq_restore(flags);
    return 1;
}

/*
 * Called from timekeeping code to reprogramm the hrtimer interrupt
 * device. If called from the timer interrupt context we defer it to
 * softirq context.
 */
void clock_was_set_delayed(void)
{
    struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);

    cpu_base->clock_was_set = 1;
    __raise_softirq_irqoff(HRTIMER_SOFTIRQ);
}

#else

static inline int hrtimer_hres_active(void) { return 0; }
static inline int hrtimer_is_hres_enabled(void) { return 0; }
static inline int hrtimer_switch_to_hres(void) { return 0; }
static inline void
hrtimer_force_reprogram(struct hrtimer_cpu_base *base, int skip_equal) { }
static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
                        struct hrtimer_clock_base *base,
                        int wakeup)
{
    return 0;
}
static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base) { }
static inline void retrigger_next_event(void *arg) { }

#endif /* CONFIG_HIGH_RES_TIMERS */

/*
 * Clock realtime was set
 *
 * Change the offset of the realtime clock vs. the monotonic
 * clock.
 *
 * We might have to reprogram the high resolution timer interrupt. On
 * SMP we call the architecture specific code to retrigger _all_ high
 * resolution timer interrupts. On UP we just disable interrupts and
 * call the high resolution interrupt code.
 */
void clock_was_set(void)
{
#ifdef CONFIG_HIGH_RES_TIMERS
    /* Retrigger the CPU local events everywhere */
    on_each_cpu(retrigger_next_event, NULL, 1);
#endif
    timerfd_clock_was_set();
}

/*
 * During resume we might have to reprogram the high resolution timer
 * interrupt (on the local CPU):
 */
void hrtimers_resume(void)
{
    WARN_ONCE(!irqs_disabled(),
          KERN_INFO "hrtimers_resume() called with IRQs enabled!");

    retrigger_next_event(NULL);
    timerfd_clock_was_set();
}

static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
{
#ifdef CONFIG_TIMER_STATS
    if (timer->start_site)
        return;
    timer->start_site = __builtin_return_address(0);
    memcpy(timer->start_comm, current->comm, TASK_COMM_LEN);
    timer->start_pid = current->pid;
#endif
}

static inline void timer_stats_hrtimer_clear_start_info(struct hrtimer *timer)
{
#ifdef CONFIG_TIMER_STATS
    timer->start_site = NULL;
#endif
}

static inline void timer_stats_account_hrtimer(struct hrtimer *timer)
{
#ifdef CONFIG_TIMER_STATS
    if (likely(!timer_stats_active))
        return;
    timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
                 timer->function, timer->start_comm, 0);
#endif
}

/*
 * Counterpart to lock_hrtimer_base above:
 */
static inline
void unlock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
{
    raw_spin_unlock_irqrestore(&timer->base->cpu_base->lock, *flags);
}

u64 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval)
{
    u64 orun = 1;
    ktime_t delta;

    delta = ktime_sub(now, hrtimer_get_expires(timer));

    if (delta.tv64 < 0)
        return 0;

    if (interval.tv64 < timer->base->resolution.tv64)
        interval.tv64 = timer->base->resolution.tv64;

    if (unlikely(delta.tv64 >= interval.tv64)) {
        s64 incr = ktime_to_ns(interval);

        orun = ktime_divns(delta, incr);
        hrtimer_add_expires_ns(timer, incr * orun);
        if (hrtimer_get_expires_tv64(timer) > now.tv64)
            return orun;
        /*
         * This (and the ktime_add() below) is the
         * correction for exact:
         */
        orun++;
    }
    hrtimer_add_expires(timer, interval);

    return orun;
}
EXPORT_SYMBOL_GPL(hrtimer_forward);

/*
 * enqueue_hrtimer - internal function to (re)start a timer
 *
 * The timer is inserted in expiry order. Insertion into the
 * red black tree is O(log(n)). Must hold the base lock.
 *
 * Returns 1 when the new timer is the leftmost timer in the tree.
 */
static int enqueue_hrtimer(struct hrtimer *timer,
               struct hrtimer_clock_base *base)
{
    debug_activate(timer);

    timerqueue_add(&base->active, &timer->node);
    base->cpu_base->active_bases |= 1 << base->index;

    /*
     * HRTIMER_STATE_ENQUEUED is or'ed to the current state to preserve the
     * state of a possibly running callback.
     */
    timer->state |= HRTIMER_STATE_ENQUEUED;

    return (&timer->node == base->active.next);
}

/*
 * __remove_hrtimer - internal function to remove a timer
 *
 * Caller must hold the base lock.
 *
 * High resolution timer mode reprograms the clock event device when the
 * timer is the one which expires next. The caller can disable this by setting
 * reprogram to zero. This is useful, when the context does a reprogramming
 * anyway (e.g. timer interrupt)
 */
static void __remove_hrtimer(struct hrtimer *timer,
                 struct hrtimer_clock_base *base,
                 unsigned long newstate, int reprogram)
{
    struct timerqueue_node *next_timer;
    if (!(timer->state & HRTIMER_STATE_ENQUEUED))
        goto out;

    next_timer = timerqueue_getnext(&base->active);
    timerqueue_del(&base->active, &timer->node);
    if (&timer->node == next_timer) {
#ifdef CONFIG_HIGH_RES_TIMERS
        /* Reprogram the clock event device. if enabled */
        if (reprogram && hrtimer_hres_active()) {
            ktime_t expires;

            expires = ktime_sub(hrtimer_get_expires(timer),
                        base->offset);
            if (base->cpu_base->expires_next.tv64 == expires.tv64)
                hrtimer_force_reprogram(base->cpu_base, 1);
        }
#endif
    }
    if (!timerqueue_getnext(&base->active))
        base->cpu_base->active_bases &= ~(1 << base->index);
out:
    timer->state = newstate;
}

/*
 * remove hrtimer, called with base lock held
 */
static inline int
remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)
{
    if (hrtimer_is_queued(timer)) {
        unsigned long state;
        int reprogram;

        /*
         * Remove the timer and force reprogramming when high
         * resolution mode is active and the timer is on the current
         * CPU. If we remove a timer on another CPU, reprogramming is
         * skipped. The interrupt event on this CPU is fired and
         * reprogramming happens in the interrupt handler. This is a
         * rare case and less expensive than a smp call.
         */
        debug_deactivate(timer);
        timer_stats_hrtimer_clear_start_info(timer);
        reprogram = base->cpu_base == &__get_cpu_var(hrtimer_bases);
        /*
         * We must preserve the CALLBACK state flag here,
         * otherwise we could move the timer base in
         * switch_hrtimer_base.
         */
        state = timer->state & HRTIMER_STATE_CALLBACK;
        __remove_hrtimer(timer, base, state, reprogram);
        return 1;
    }
    return 0;
}

int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
        unsigned long delta_ns, const enum hrtimer_mode mode,
        int wakeup)
{
    struct hrtimer_clock_base *base, *new_base;
    unsigned long flags;
    int ret, leftmost;

    base = lock_hrtimer_base(timer, &flags);

    /* Remove an active timer from the queue: */
    ret = remove_hrtimer(timer, base);

    /* Switch the timer base, if necessary: */
    new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);

    if (mode & HRTIMER_MODE_REL) {
        tim = ktime_add_safe(tim, new_base->get_time());
        /*
         * CONFIG_TIME_LOW_RES is a temporary way for architectures
         * to signal that they simply return xtime in
         * do_gettimeoffset(). In this case we want to round up by
         * resolution when starting a relative timer, to avoid short
         * timeouts. This will go away with the GTOD framework.
         */
#ifdef CONFIG_TIME_LOW_RES
        tim = ktime_add_safe(tim, base->resolution);
#endif
    }

    hrtimer_set_expires_range_ns(timer, tim, delta_ns);

    timer_stats_hrtimer_set_start_info(timer);

    leftmost = enqueue_hrtimer(timer, new_base);

    /*
     * Only allow reprogramming if the new base is on this CPU.
     * (it might still be on another CPU if the timer was pending)
     *
     * XXX send_remote_softirq() ?
     */
    if (leftmost && new_base->cpu_base == &__get_cpu_var(hrtimer_bases))
        hrtimer_enqueue_reprogram(timer, new_base, wakeup);

    unlock_hrtimer_base(timer, &flags);

    return ret;
}

int hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
        unsigned long delta_ns, const enum hrtimer_mode mode)
{
    return __hrtimer_start_range_ns(timer, tim, delta_ns, mode, 1);
}
EXPORT_SYMBOL_GPL(hrtimer_start_range_ns);

int
hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
{
    return __hrtimer_start_range_ns(timer, tim, 0, mode, 1);
}
EXPORT_SYMBOL_GPL(hrtimer_start);


int hrtimer_try_to_cancel(struct hrtimer *timer)
{
    struct hrtimer_clock_base *base;
    unsigned long flags;
    int ret = -1;

    base = lock_hrtimer_base(timer, &flags);

    if (!hrtimer_callback_running(timer))
        ret = remove_hrtimer(timer, base);

    unlock_hrtimer_base(timer, &flags);

    return ret;

}
EXPORT_SYMBOL_GPL(hrtimer_try_to_cancel);

int hrtimer_cancel(struct hrtimer *timer)
{
    for (;;) {
        int ret = hrtimer_try_to_cancel(timer);

        if (ret >= 0)
            return ret;
        cpu_relax();
    }
}
EXPORT_SYMBOL_GPL(hrtimer_cancel);

ktime_t hrtimer_get_remaining(const struct hrtimer *timer)
{
    unsigned long flags;
    ktime_t rem;

    lock_hrtimer_base(timer, &flags);
    rem = hrtimer_expires_remaining(timer);
    unlock_hrtimer_base(timer, &flags);

    return rem;
}
EXPORT_SYMBOL_GPL(hrtimer_get_remaining);

#ifdef CONFIG_NO_HZ

ktime_t hrtimer_get_next_event(void)
{
    struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
    struct hrtimer_clock_base *base = cpu_base->clock_base;
    ktime_t delta, mindelta = { .tv64 = KTIME_MAX };
    unsigned long flags;
    int i;

    raw_spin_lock_irqsave(&cpu_base->lock, flags);

    if (!hrtimer_hres_active()) {
        for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++, base++) {
            struct hrtimer *timer;
            struct timerqueue_node *next;

            next = timerqueue_getnext(&base->active);
            if (!next)
                continue;

            timer = container_of(next, struct hrtimer, node);
            delta.tv64 = hrtimer_get_expires_tv64(timer);
            delta = ktime_sub(delta, base->get_time());
            if (delta.tv64 < mindelta.tv64)
                mindelta.tv64 = delta.tv64;
        }
    }

    raw_spin_unlock_irqrestore(&cpu_base->lock, flags);

    if (mindelta.tv64 < 0)
        mindelta.tv64 = 0;
    return mindelta;
}
#endif

static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
               enum hrtimer_mode mode)
{
    struct hrtimer_cpu_base *cpu_base;
    int base;

    memset(timer, 0, sizeof(struct hrtimer));

    cpu_base = &__raw_get_cpu_var(hrtimer_bases);

    if (clock_id == CLOCK_REALTIME && mode != HRTIMER_MODE_ABS)
        clock_id = CLOCK_MONOTONIC;

    base = hrtimer_clockid_to_base(clock_id);
    timer->base = &cpu_base->clock_base[base];
    timerqueue_init(&timer->node);

#ifdef CONFIG_TIMER_STATS
    timer->start_site = NULL;
    timer->start_pid = -1;
    memset(timer->start_comm, 0, TASK_COMM_LEN);
#endif
}

void hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
          enum hrtimer_mode mode)
{
    debug_init(timer, clock_id, mode);
    __hrtimer_init(timer, clock_id, mode);
}
EXPORT_SYMBOL_GPL(hrtimer_init);

int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
{
    struct hrtimer_cpu_base *cpu_base;
    int base = hrtimer_clockid_to_base(which_clock);

    cpu_base = &__raw_get_cpu_var(hrtimer_bases);
    *tp = ktime_to_timespec(cpu_base->clock_base[base].resolution);

    return 0;
}
EXPORT_SYMBOL_GPL(hrtimer_get_res);

static void __run_hrtimer(struct hrtimer *timer, ktime_t *now)
{
    struct hrtimer_clock_base *base = timer->base;
    struct hrtimer_cpu_base *cpu_base = base->cpu_base;
    enum hrtimer_restart (*fn)(struct hrtimer *);
    int restart;

    WARN_ON(!irqs_disabled());

    debug_deactivate(timer);
    __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
    timer_stats_account_hrtimer(timer);
    fn = timer->function;

    /*
     * Because we run timers from hardirq context, there is no chance
     * they get migrated to another cpu, therefore its safe to unlock
     * the timer base.
     */
    raw_spin_unlock(&cpu_base->lock);
    trace_hrtimer_expire_entry(timer, now);
    restart = fn(timer);
    trace_hrtimer_expire_exit(timer);
    raw_spin_lock(&cpu_base->lock);

    /*
     * Note: We clear the CALLBACK bit after enqueue_hrtimer and
     * we do not reprogramm the event hardware. Happens either in
     * hrtimer_start_range_ns() or in hrtimer_interrupt()
     */
    if (restart != HRTIMER_NORESTART) {
        BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
        enqueue_hrtimer(timer, base);
    }

    WARN_ON_ONCE(!(timer->state & HRTIMER_STATE_CALLBACK));

    timer->state &= ~HRTIMER_STATE_CALLBACK;
}

#ifdef CONFIG_HIGH_RES_TIMERS

/*
 * High resolution timer interrupt
 * Called with interrupts disabled
 */
void hrtimer_interrupt(struct clock_event_device *dev)
{
    struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
    ktime_t expires_next, now, entry_time, delta;
    int i, retries = 0;

    BUG_ON(!cpu_base->hres_active);
    cpu_base->nr_events++;
    dev->next_event.tv64 = KTIME_MAX;

    raw_spin_lock(&cpu_base->lock);
    entry_time = now = hrtimer_update_base(cpu_base);
retry:
    expires_next.tv64 = KTIME_MAX;
    /*
     * We set expires_next to KTIME_MAX here with cpu_base->lock
     * held to prevent that a timer is enqueued in our queue via
     * the migration code. This does not affect enqueueing of
     * timers which run their callback and need to be requeued on
     * this CPU.
     */
    cpu_base->expires_next.tv64 = KTIME_MAX;

    for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
        struct hrtimer_clock_base *base;
        struct timerqueue_node *node;
        ktime_t basenow;

        if (!(cpu_base->active_bases & (1 << i)))
            continue;

        base = cpu_base->clock_base + i;
        basenow = ktime_add(now, base->offset);

        while ((node = timerqueue_getnext(&base->active))) {
            struct hrtimer *timer;

            timer = container_of(node, struct hrtimer, node);

            /*
             * The immediate goal for using the softexpires is
             * minimizing wakeups, not running timers at the
             * earliest interrupt after their soft expiration.
             * This allows us to avoid using a Priority Search
             * Tree, which can answer a stabbing querry for
             * overlapping intervals and instead use the simple
             * BST we already have.
             * We don't add extra wakeups by delaying timers that
             * are right-of a not yet expired timer, because that
             * timer will have to trigger a wakeup anyway.
             */

            if (basenow.tv64 < hrtimer_get_softexpires_tv64(timer)) {
                ktime_t expires;

                expires = ktime_sub(hrtimer_get_expires(timer),
                            base->offset);
                if (expires.tv64 < expires_next.tv64)
                    expires_next = expires;
                break;
            }

            __run_hrtimer(timer, &basenow);
        }
    }

    /*
     * Store the new expiry value so the migration code can verify
     * against it.
     */
    cpu_base->expires_next = expires_next;
    raw_spin_unlock(&cpu_base->lock);

    /* Reprogramming necessary ? */
    if (expires_next.tv64 == KTIME_MAX ||
        !tick_program_event(expires_next, 0)) {
        cpu_base->hang_detected = 0;
        return;
    }

    /*
     * The next timer was already expired due to:
     * - tracing
     * - long lasting callbacks
     * - being scheduled away when running in a VM
     *
     * We need to prevent that we loop forever in the hrtimer
     * interrupt routine. We give it 3 attempts to avoid
     * overreacting on some spurious event.
     *
     * Acquire base lock for updating the offsets and retrieving
     * the current time.
     */
    raw_spin_lock(&cpu_base->lock);
    now = hrtimer_update_base(cpu_base);
    cpu_base->nr_retries++;
    if (++retries < 3)
        goto retry;
    /*
     * Give the system a chance to do something else than looping
     * here. We stored the entry time, so we know exactly how long
     * we spent here. We schedule the next event this amount of
     * time away.
     */
    cpu_base->nr_hangs++;
    cpu_base->hang_detected = 1;
    raw_spin_unlock(&cpu_base->lock);
    delta = ktime_sub(now, entry_time);
    if (delta.tv64 > cpu_base->max_hang_time.tv64)
        cpu_base->max_hang_time = delta;
    /*
     * Limit it to a sensible value as we enforce a longer
     * delay. Give the CPU at least 100ms to catch up.
     */
    if (delta.tv64 > 100 * NSEC_PER_MSEC)
        expires_next = ktime_add_ns(now, 100 * NSEC_PER_MSEC);
    else
        expires_next = ktime_add(now, delta);
    tick_program_event(expires_next, 1);
    printk_once(KERN_WARNING "hrtimer: interrupt took %llu ns\n",
            ktime_to_ns(delta));
}

/*
 * local version of hrtimer_peek_ahead_timers() called with interrupts
 * disabled.
 */
static void __hrtimer_peek_ahead_timers(void)
{
    struct tick_device *td;

    if (!hrtimer_hres_active())
        return;

    td = &__get_cpu_var(tick_cpu_device);
    if (td && td->evtdev)
        hrtimer_interrupt(td->evtdev);
}

void hrtimer_peek_ahead_timers(void)
{
    unsigned long flags;

    local_irq_save(flags);
    __hrtimer_peek_ahead_timers();
    local_irq_restore(flags);
}

static void run_hrtimer_softirq(struct softirq_action *h)
{
    struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);

    if (cpu_base->clock_was_set) {
        cpu_base->clock_was_set = 0;
        clock_was_set();
    }

    hrtimer_peek_ahead_timers();
}

#else /* CONFIG_HIGH_RES_TIMERS */

static inline void __hrtimer_peek_ahead_timers(void) { }

#endif  /* !CONFIG_HIGH_RES_TIMERS */

/*
 * Called from timer softirq every jiffy, expire hrtimers:
 *
 * For HRT its the fall back code to run the softirq in the timer
 * softirq context in case the hrtimer initialization failed or has
 * not been done yet.
 */
void hrtimer_run_pending(void)
{
    if (hrtimer_hres_active())
        return;

    /*
     * This _is_ ugly: We have to check in the softirq context,
     * whether we can switch to highres and / or nohz mode. The
     * clocksource switch happens in the timer interrupt with
     * xtime_lock held. Notification from there only sets the
     * check bit in the tick_oneshot code, otherwise we might
     * deadlock vs. xtime_lock.
     */
    if (tick_check_oneshot_change(!hrtimer_is_hres_enabled()))
        hrtimer_switch_to_hres();
}

/*
 * Called from hardirq context every jiffy
 */
void hrtimer_run_queues(void)
{
    struct timerqueue_node *node;
    struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
    struct hrtimer_clock_base *base;
    int index, gettime = 1;

    if (hrtimer_hres_active())
        return;

    for (index = 0; index < HRTIMER_MAX_CLOCK_BASES; index++) {
        base = &cpu_base->clock_base[index];
        if (!timerqueue_getnext(&base->active))
            continue;

        if (gettime) {
            hrtimer_get_softirq_time(cpu_base);
            gettime = 0;
        }

        raw_spin_lock(&cpu_base->lock);

        while ((node = timerqueue_getnext(&base->active))) {
            struct hrtimer *timer;

            timer = container_of(node, struct hrtimer, node);
            if (base->softirq_time.tv64 <=
                    hrtimer_get_expires_tv64(timer))
                break;

            __run_hrtimer(timer, &base->softirq_time);
        }
        raw_spin_unlock(&cpu_base->lock);
    }
}

/*
 * Sleep related functions:
 */
static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer)
{
    struct hrtimer_sleeper *t =
        container_of(timer, struct hrtimer_sleeper, timer);
    struct task_struct *task = t->task;

    t->task = NULL;
    if (task)
        wake_up_process(task);

    return HRTIMER_NORESTART;
}

void hrtimer_init_sleeper(struct hrtimer_sleeper *sl, struct task_struct *task)
{
    sl->timer.function = hrtimer_wakeup;
    sl->task = task;
}
EXPORT_SYMBOL_GPL(hrtimer_init_sleeper);

static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode)
{
    hrtimer_init_sleeper(t, current);

    do {
        set_current_state(TASK_INTERRUPTIBLE);
        hrtimer_start_expires(&t->timer, mode);
        if (!hrtimer_active(&t->timer))
            t->task = NULL;

        if (likely(t->task))
            schedule();

        hrtimer_cancel(&t->timer);
        mode = HRTIMER_MODE_ABS;

    } while (t->task && !signal_pending(current));

    __set_current_state(TASK_RUNNING);

    return t->task == NULL;
}

static int update_rmtp(struct hrtimer *timer, struct timespec __user *rmtp)
{
    struct timespec rmt;
    ktime_t rem;

    rem = hrtimer_expires_remaining(timer);
    if (rem.tv64 <= 0)
        return 0;
    rmt = ktime_to_timespec(rem);

    if (copy_to_user(rmtp, &rmt, sizeof(*rmtp)))
        return -EFAULT;

    return 1;
}

long __sched hrtimer_nanosleep_restart(struct restart_block *restart)
{
    struct hrtimer_sleeper t;
    struct timespec __user  *rmtp;
    int ret = 0;

    hrtimer_init_on_stack(&t.timer, restart->nanosleep.clockid,
                HRTIMER_MODE_ABS);
    hrtimer_set_expires_tv64(&t.timer, restart->nanosleep.expires);

    if (do_nanosleep(&t, HRTIMER_MODE_ABS))
        goto out;

    rmtp = restart->nanosleep.rmtp;
    if (rmtp) {
        ret = update_rmtp(&t.timer, rmtp);
        if (ret <= 0)
            goto out;
    }

    /* The other values in restart are already filled in */
    ret = -ERESTART_RESTARTBLOCK;
out:
    destroy_hrtimer_on_stack(&t.timer);
    return ret;
}

long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
               const enum hrtimer_mode mode, const clockid_t clockid)
{
    struct restart_block *restart;
    struct hrtimer_sleeper t;
    int ret = 0;
    unsigned long slack;

    slack = current->timer_slack_ns;
    if (rt_task(current))
        slack = 0;

    hrtimer_init_on_stack(&t.timer, clockid, mode);
    hrtimer_set_expires_range_ns(&t.timer, timespec_to_ktime(*rqtp), slack);
    if (do_nanosleep(&t, mode))
        goto out;

    /* Absolute timers do not update the rmtp value and restart: */
    if (mode == HRTIMER_MODE_ABS) {
        ret = -ERESTARTNOHAND;
        goto out;
    }

    if (rmtp) {
        ret = update_rmtp(&t.timer, rmtp);
        if (ret <= 0)
            goto out;
    }

    restart = &current_thread_info()->restart_block;
    restart->fn = hrtimer_nanosleep_restart;
    restart->nanosleep.clockid = t.timer.base->clockid;
    restart->nanosleep.rmtp = rmtp;
    restart->nanosleep.expires = hrtimer_get_expires_tv64(&t.timer);

    ret = -ERESTART_RESTARTBLOCK;
out:
    destroy_hrtimer_on_stack(&t.timer);
    return ret;
}

SYSCALL_DEFINE2(nanosleep, struct timespec __user *, rqtp,
        struct timespec __user *, rmtp)
{
    struct timespec tu;

    if (copy_from_user(&tu, rqtp, sizeof(tu)))
        return -EFAULT;

    if (!timespec_valid(&tu))
        return -EINVAL;

    return hrtimer_nanosleep(&tu, rmtp, HRTIMER_MODE_REL, CLOCK_MONOTONIC);
}

/*
 * Functions related to boot-time initialization:
 */
static void __cpuinit init_hrtimers_cpu(int cpu)
{
    struct hrtimer_cpu_base *cpu_base = &per_cpu(hrtimer_bases, cpu);
    int i;

    raw_spin_lock_init(&cpu_base->lock);

    for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
        cpu_base->clock_base[i].cpu_base = cpu_base;
        timerqueue_init_head(&cpu_base->clock_base[i].active);
    }

    hrtimer_init_hres(cpu_base);
}

#ifdef CONFIG_HOTPLUG_CPU

static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
                struct hrtimer_clock_base *new_base)
{
    struct hrtimer *timer;
    struct timerqueue_node *node;

    while ((node = timerqueue_getnext(&old_base->active))) {
        timer = container_of(node, struct hrtimer, node);
        BUG_ON(hrtimer_callback_running(timer));
        debug_deactivate(timer);

        /*
         * Mark it as STATE_MIGRATE not INACTIVE otherwise the
         * timer could be seen as !active and just vanish away
         * under us on another CPU
         */
        __remove_hrtimer(timer, old_base, HRTIMER_STATE_MIGRATE, 0);
        timer->base = new_base;
        /*
         * Enqueue the timers on the new cpu. This does not
         * reprogram the event device in case the timer
         * expires before the earliest on this CPU, but we run
         * hrtimer_interrupt after we migrated everything to
         * sort out already expired timers and reprogram the
         * event device.
         */
        enqueue_hrtimer(timer, new_base);

        /* Clear the migration state bit */
        timer->state &= ~HRTIMER_STATE_MIGRATE;
    }
}

static void migrate_hrtimers(int scpu)
{
    struct hrtimer_cpu_base *old_base, *new_base;
    int i;

    BUG_ON(cpu_online(scpu));
    tick_cancel_sched_timer(scpu);

    local_irq_disable();
    old_base = &per_cpu(hrtimer_bases, scpu);
    new_base = &__get_cpu_var(hrtimer_bases);
    /*
     * The caller is globally serialized and nobody else
     * takes two locks at once, deadlock is not possible.
     */
    raw_spin_lock(&new_base->lock);
    raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);

    for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
        migrate_hrtimer_list(&old_base->clock_base[i],
                     &new_base->clock_base[i]);
    }

    raw_spin_unlock(&old_base->lock);
    raw_spin_unlock(&new_base->lock);

    /* Check, if we got expired work to do */
    __hrtimer_peek_ahead_timers();
    local_irq_enable();
}

#endif /* CONFIG_HOTPLUG_CPU */

static int __cpuinit hrtimer_cpu_notify(struct notifier_block *self,
                    unsigned long action, void *hcpu)
{
    int scpu = (long)hcpu;

    switch (action) {

    case CPU_UP_PREPARE:
    case CPU_UP_PREPARE_FROZEN:
        init_hrtimers_cpu(scpu);
        break;

#ifdef CONFIG_HOTPLUG_CPU
    case CPU_DYING:
    case CPU_DYING_FROZEN:
        clockevents_notify(CLOCK_EVT_NOTIFY_CPU_DYING, &scpu);
        break;
    case CPU_DEAD:
    case CPU_DEAD_FROZEN:
    {
        clockevents_notify(CLOCK_EVT_NOTIFY_CPU_DEAD, &scpu);
        migrate_hrtimers(scpu);
        break;
    }
#endif

    default:
        break;
    }

    return NOTIFY_OK;
}

static struct notifier_block __cpuinitdata hrtimers_nb = {
    .notifier_call = hrtimer_cpu_notify,
};

void __init hrtimers_init(void)
{
    hrtimer_cpu_notify(&hrtimers_nb, (unsigned long)CPU_UP_PREPARE,
              (void *)(long)smp_processor_id());
    register_cpu_notifier(&hrtimers_nb);
#ifdef CONFIG_HIGH_RES_TIMERS
    open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq);
#endif
}

int __sched
schedule_hrtimeout_range_clock(ktime_t *expires, unsigned long delta,
                   const enum hrtimer_mode mode, int clock)
{
    struct hrtimer_sleeper t;

    /*
     * Optimize when a zero timeout value is given. It does not
     * matter whether this is an absolute or a relative time.
     */
    if (expires && !expires->tv64) {
        __set_current_state(TASK_RUNNING);
        return 0;
    }

    /*
     * A NULL parameter means "infinite"
     */
    if (!expires) {
        schedule();
        __set_current_state(TASK_RUNNING);
        return -EINTR;
    }

    hrtimer_init_on_stack(&t.timer, clock, mode);
    hrtimer_set_expires_range_ns(&t.timer, *expires, delta);

    hrtimer_init_sleeper(&t, current);

    hrtimer_start_expires(&t.timer, mode);
    if (!hrtimer_active(&t.timer))
        t.task = NULL;

    if (likely(t.task))
        schedule();

    hrtimer_cancel(&t.timer);
    destroy_hrtimer_on_stack(&t.timer);

    __set_current_state(TASK_RUNNING);

    return !t.task ? 0 : -EINTR;
}

int __sched schedule_hrtimeout_range(ktime_t *expires, unsigned long delta,
                     const enum hrtimer_mode mode)
{
    return schedule_hrtimeout_range_clock(expires, delta, mode,
                          CLOCK_MONOTONIC);
}
EXPORT_SYMBOL_GPL(schedule_hrtimeout_range);

int __sched schedule_hrtimeout(ktime_t *expires,
                   const enum hrtimer_mode mode)
{
    return schedule_hrtimeout_range(expires, 0, mode);
}
EXPORT_SYMBOL_GPL(schedule_hrtimeout);