timer.c

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/*
 *  linux/kernel/timer.c
 *
 *  Kernel internal timers, basic process system calls
 *
 *  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/slab.h>

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

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

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 list_head vec[TVN_SIZE];
};

struct tvec_root {
    struct list_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;
    struct tvec_root tv1;
    struct tvec tv2;
    struct tvec tv3;
    struct tvec tv4;
    struct tvec tv5;
} ____cacheline_aligned;

struct tvec_base boot_tvec_bases;
EXPORT_SYMBOL(boot_tvec_bases);
static DEFINE_PER_CPU(struct tvec_base *, tvec_bases) = &boot_tvec_bases;

/* Functions below help us manage 'deferrable' flag */
static inline unsigned int tbase_get_deferrable(struct tvec_base *base)
{
    return ((unsigned int)(unsigned long)base & TIMER_DEFERRABLE);
}

static inline unsigned int tbase_get_irqsafe(struct tvec_base *base)
{
    return ((unsigned int)(unsigned long)base & TIMER_IRQSAFE);
}

static inline struct tvec_base *tbase_get_base(struct tvec_base *base)
{
    return ((struct tvec_base *)((unsigned long)base & ~TIMER_FLAG_MASK));
}

static inline void
timer_set_base(struct timer_list *timer, struct tvec_base *new_base)
{
    unsigned long flags = (unsigned long)timer->base & TIMER_FLAG_MASK;

    timer->base = (struct tvec_base *)((unsigned long)(new_base) | flags);
}

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;

    if (j <= jiffies) /* rounding ate our timeout entirely; */
        return original;
    return j;
}

unsigned long __round_jiffies(unsigned long j, int cpu)
{
    return round_jiffies_common(j, cpu, false);
}
EXPORT_SYMBOL_GPL(__round_jiffies);

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);

unsigned long round_jiffies(unsigned long j)
{
    return round_jiffies_common(j, raw_smp_processor_id(), false);
}
EXPORT_SYMBOL_GPL(round_jiffies);

unsigned long round_jiffies_relative(unsigned long j)
{
    return __round_jiffies_relative(j, raw_smp_processor_id());
}
EXPORT_SYMBOL_GPL(round_jiffies_relative);

unsigned long __round_jiffies_up(unsigned long j, int cpu)
{
    return round_jiffies_common(j, cpu, true);
}
EXPORT_SYMBOL_GPL(__round_jiffies_up);

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);

unsigned long round_jiffies_up(unsigned long j)
{
    return round_jiffies_common(j, raw_smp_processor_id(), true);
}
EXPORT_SYMBOL_GPL(round_jiffies_up);

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);

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 list_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;
    }
    /*
     * Timers are FIFO:
     */
    list_add_tail(&timer->entry, vec);
}

static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
{
    __internal_add_timer(base, timer);
    /*
     * Update base->active_timers and base->next_timer
     */
    if (!tbase_get_deferrable(timer->base)) {
        if (time_before(timer->expires, base->next_timer))
            base->next_timer = timer->expires;
        base->active_timers++;
    }
}

#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)
{
    unsigned int flag = 0;

    if (likely(!timer->start_site))
        return;
    if (unlikely(tbase_get_deferrable(timer->base)))
        flag |= TIMER_STATS_FLAG_DEFERRABLE;

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

#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.next == NULL &&
            timer->entry.prev == 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.prev == 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);
}

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)
{
    struct tvec_base *base = __raw_get_cpu_var(tvec_bases);

    timer->entry.next = NULL;
    timer->base = (void *)((unsigned long)base | flags);
    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);
}

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 list_head *entry = &timer->entry;

    debug_deactivate(timer);

    __list_del(entry->prev, entry->next);
    if (clear_pending)
        entry->next = NULL;
    entry->prev = LIST_POISON2;
}

static inline void
detach_expired_timer(struct timer_list *timer, struct tvec_base *base)
{
    detach_timer(timer, true);
    if (!tbase_get_deferrable(timer->base))
        base->active_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 (!tbase_get_deferrable(timer->base)) {
        base->active_timers--;
        if (timer->expires == base->next_timer)
            base->next_timer = base->timer_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 the timer removed from list, it is
 * possible to set timer->base = NULL and drop the lock: the timer remains
 * locked.
 */
static struct tvec_base *lock_timer_base(struct timer_list *timer,
                    unsigned long *flags)
    __acquires(timer->base->lock)
{
    struct tvec_base *base;

    for (;;) {
        struct tvec_base *prelock_base = timer->base;
        base = tbase_get_base(prelock_base);
        if (likely(base != NULL)) {
            spin_lock_irqsave(&base->lock, *flags);
            if (likely(prelock_base == timer->base))
                return base;
            /* The timer has migrated to another CPU */
            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 , cpu;

    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);

    cpu = smp_processor_id();

#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)
    if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu))
        cpu = get_nohz_timer_target();
#endif
    new_base = per_cpu(tvec_bases, cpu);

    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_set_base(timer, NULL);
            spin_unlock(&base->lock);
            base = new_base;
            spin_lock(&base->lock);
            timer_set_base(timer, base);
        }
    }

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

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

    return ret;
}

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 = (1 << bit) - 1;

    expires_limit = expires_limit & ~(mask);

    return expires_limit;
}

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);

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);

void add_timer(struct timer_list *timer)
{
    BUG_ON(timer_pending(timer));
    mod_timer(timer, timer->expires);
}
EXPORT_SYMBOL(add_timer);

void add_timer_on(struct timer_list *timer, int cpu)
{
    struct tvec_base *base = per_cpu(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_set_base(timer, base);
    debug_activate(timer, timer->expires);
    internal_add_timer(base, timer);
    /*
     * Check whether the other CPU is idle and needs to be
     * triggered to reevaluate the timer wheel when nohz is
     * active. 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 idle can not evaluate
     * the timer wheel.
     */
    wake_up_idle_cpu(cpu);
    spin_unlock_irqrestore(&base->lock, flags);
}
EXPORT_SYMBOL_GPL(add_timer_on);

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);

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

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() && !tbase_get_irqsafe(timer->base));
    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, *tmp;
    struct list_head tv_list;

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

    /*
     * We are removing _all_ timers from the list, so we
     * don't have to detach them individually.
     */
    list_for_each_entry_safe(timer, tmp, &tv_list, entry) {
        BUG_ON(tbase_get_base(timer->base) != base);
        /* 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 preempt_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 (preempt_count != preempt_count()) {
        WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x\n",
              fn, preempt_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() = preempt_count;
    }
}

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

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 list_head work_list;
        struct list_head *head = &work_list;
        int 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;
        list_replace_init(base->tv1.vec + index, &work_list);
        while (!list_empty(head)) {
            void (*fn)(unsigned long);
            unsigned long data;
            bool irqsafe;

            timer = list_first_entry(head, struct timer_list,entry);
            fn = timer->function;
            data = timer->data;
            irqsafe = tbase_get_irqsafe(timer->base);

            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
/*
 * 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 {
        list_for_each_entry(nte, base->tv1.vec + slot, entry) {
            if (tbase_get_deferrable(nte->base))
                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 {
            list_for_each_entry(nte, varp->vec + slot, entry) {
                if (tbase_get_deferrable(nte->base))
                    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 unsigned long cmp_next_hrtimer_event(unsigned long now,
                        unsigned long expires)
{
    ktime_t hr_delta = hrtimer_get_next_event();
    struct timespec tsdelta;
    unsigned long delta;

    if (hr_delta.tv64 == KTIME_MAX)
        return expires;

    /*
     * Expired timer available, let it expire in the next tick
     */
    if (hr_delta.tv64 <= 0)
        return now + 1;

    tsdelta = ktime_to_timespec(hr_delta);
    delta = timespec_to_jiffies(&tsdelta);

    /*
     * Limit the delta to the max value, which is checked in
     * tick_nohz_stop_sched_tick():
     */
    if (delta > NEXT_TIMER_MAX_DELTA)
        delta = NEXT_TIMER_MAX_DELTA;

    /*
     * Take rounding errors in to account and make sure, that it
     * expires in the next tick. Otherwise we go into an endless
     * ping pong due to tick_nohz_stop_sched_tick() retriggering
     * the timer softirq
     */
    if (delta < 1)
        delta = 1;
    now += delta;
    if (time_before(now, expires))
        return now;
    return expires;
}

unsigned long get_next_timer_interrupt(unsigned long now)
{
    struct tvec_base *base = __this_cpu_read(tvec_bases);
    unsigned long expires = now + NEXT_TIMER_MAX_DELTA;

    /*
     * 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);
        expires = base->next_timer;
    }
    spin_unlock(&base->lock);

    if (time_before_eq(expires, now))
        return now;

    return cmp_next_hrtimer_event(now, 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;
    int cpu = smp_processor_id();

    /* Note: this timer irq context must be accounted for as well. */
    account_process_tick(p, user_tick);
    run_local_timers();
    rcu_check_callbacks(cpu, user_tick);
    printk_tick();
#ifdef CONFIG_IRQ_WORK
    if (in_irq())
        irq_work_run();
#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_read(tvec_bases);

    hrtimer_run_pending();

    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

SYSCALL_DEFINE0(getpid)
{
    return task_tgid_vnr(current);
}

/*
 * Accessing ->real_parent is not SMP-safe, it could
 * change from under us. However, we can use a stale
 * value of ->real_parent under rcu_read_lock(), see
 * release_task()->call_rcu(delayed_put_task_struct).
 */
SYSCALL_DEFINE0(getppid)
{
    int pid;

    rcu_read_lock();
    pid = task_tgid_vnr(rcu_dereference(current->real_parent));
    rcu_read_unlock();

    return pid;
}

SYSCALL_DEFINE0(getuid)
{
    /* Only we change this so SMP safe */
    return from_kuid_munged(current_user_ns(), current_uid());
}

SYSCALL_DEFINE0(geteuid)
{
    /* Only we change this so SMP safe */
    return from_kuid_munged(current_user_ns(), current_euid());
}

SYSCALL_DEFINE0(getgid)
{
    /* Only we change this so SMP safe */
    return from_kgid_munged(current_user_ns(), current_gid());
}

SYSCALL_DEFINE0(getegid)
{
    /* Only we change this so SMP safe */
    return from_kgid_munged(current_user_ns(), current_egid());
}

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

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);

/* Thread ID - the internal kernel "pid" */
SYSCALL_DEFINE0(gettid)
{
    return task_pid_vnr(current);
}

int do_sysinfo(struct sysinfo *info)
{
    unsigned long mem_total, sav_total;
    unsigned int mem_unit, bitcount;
    struct timespec tp;

    memset(info, 0, sizeof(struct sysinfo));

    ktime_get_ts(&tp);
    monotonic_to_bootbased(&tp);
    info->uptime = tp.tv_sec + (tp.tv_nsec ? 1 : 0);

    get_avenrun(info->loads, 0, SI_LOAD_SHIFT - FSHIFT);

    info->procs = nr_threads;

    si_meminfo(info);
    si_swapinfo(info);

    /*
     * If the sum of all the available memory (i.e. ram + swap)
     * is less than can be stored in a 32 bit unsigned long then
     * we can be binary compatible with 2.2.x kernels.  If not,
     * well, in that case 2.2.x was broken anyways...
     *
     *  -Erik Andersen <[email protected]>
     */

    mem_total = info->totalram + info->totalswap;
    if (mem_total < info->totalram || mem_total < info->totalswap)
        goto out;
    bitcount = 0;
    mem_unit = info->mem_unit;
    while (mem_unit > 1) {
        bitcount++;
        mem_unit >>= 1;
        sav_total = mem_total;
        mem_total <<= 1;
        if (mem_total < sav_total)
            goto out;
    }

    /*
     * If mem_total did not overflow, multiply all memory values by
     * info->mem_unit and set it to 1.  This leaves things compatible
     * with 2.2.x, and also retains compatibility with earlier 2.4.x
     * kernels...
     */

    info->mem_unit = 1;
    info->totalram <<= bitcount;
    info->freeram <<= bitcount;
    info->sharedram <<= bitcount;
    info->bufferram <<= bitcount;
    info->totalswap <<= bitcount;
    info->freeswap <<= bitcount;
    info->totalhigh <<= bitcount;
    info->freehigh <<= bitcount;

out:
    return 0;
}

SYSCALL_DEFINE1(sysinfo, struct sysinfo __user *, info)
{
    struct sysinfo val;

    do_sysinfo(&val);

    if (copy_to_user(info, &val, sizeof(struct sysinfo)))
        return -EFAULT;

    return 0;
}

static int __cpuinit init_timers_cpu(int cpu)
{
    int j;
    struct tvec_base *base;
    static char __cpuinitdata tvec_base_done[NR_CPUS];

    if (!tvec_base_done[cpu]) {
        static char boot_done;

        if (boot_done) {
            /*
             * The APs use this path later in boot
             */
            base = kmalloc_node(sizeof(*base),
                        GFP_KERNEL | __GFP_ZERO,
                        cpu_to_node(cpu));
            if (!base)
                return -ENOMEM;

            /* Make sure that tvec_base is 2 byte aligned */
            if (tbase_get_deferrable(base)) {
                WARN_ON(1);
                kfree(base);
                return -ENOMEM;
            }
            per_cpu(tvec_bases, cpu) = base;
        } else {
            /*
             * This is for the boot CPU - we use compile-time
             * static initialisation because per-cpu memory isn't
             * ready yet and because the memory allocators are not
             * initialised either.
             */
            boot_done = 1;
            base = &boot_tvec_bases;
        }
        tvec_base_done[cpu] = 1;
    } else {
        base = per_cpu(tvec_bases, cpu);
    }

    spin_lock_init(&base->lock);

    for (j = 0; j < TVN_SIZE; j++) {
        INIT_LIST_HEAD(base->tv5.vec + j);
        INIT_LIST_HEAD(base->tv4.vec + j);
        INIT_LIST_HEAD(base->tv3.vec + j);
        INIT_LIST_HEAD(base->tv2.vec + j);
    }
    for (j = 0; j < TVR_SIZE; j++)
        INIT_LIST_HEAD(base->tv1.vec + j);

    base->timer_jiffies = jiffies;
    base->next_timer = base->timer_jiffies;
    base->active_timers = 0;
    return 0;
}

#ifdef CONFIG_HOTPLUG_CPU
static void migrate_timer_list(struct tvec_base *new_base, struct list_head *head)
{
    struct timer_list *timer;

    while (!list_empty(head)) {
        timer = list_first_entry(head, struct timer_list, entry);
        /* We ignore the accounting on the dying cpu */
        detach_timer(timer, false);
        timer_set_base(timer, new_base);
        internal_add_timer(new_base, timer);
    }
}

static void __cpuinit 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(tvec_bases, cpu);
    new_base = get_cpu_var(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);
    }

    spin_unlock(&old_base->lock);
    spin_unlock_irq(&new_base->lock);
    put_cpu_var(tvec_bases);
}
#endif /* CONFIG_HOTPLUG_CPU */

static int __cpuinit timer_cpu_notify(struct notifier_block *self,
                unsigned long action, void *hcpu)
{
    long cpu = (long)hcpu;
    int err;

    switch(action) {
    case CPU_UP_PREPARE:
    case CPU_UP_PREPARE_FROZEN:
        err = init_timers_cpu(cpu);
        if (err < 0)
            return notifier_from_errno(err);
        break;
#ifdef CONFIG_HOTPLUG_CPU
    case CPU_DEAD:
    case CPU_DEAD_FROZEN:
        migrate_timers(cpu);
        break;
#endif
    default:
        break;
    }
    return NOTIFY_OK;
}

static struct notifier_block __cpuinitdata timers_nb = {
    .notifier_call  = timer_cpu_notify,
};


void __init init_timers(void)
{
    int err;

    /* ensure there are enough low bits for flags in timer->base pointer */
    BUILD_BUG_ON(__alignof__(struct tvec_base) & TIMER_FLAG_MASK);

    err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
                   (void *)(long)smp_processor_id());
    init_timer_stats();

    BUG_ON(err != NOTIFY_OK);
    register_cpu_notifier(&timers_nb);
    open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
}

void msleep(unsigned int msecs)
{
    unsigned long timeout = msecs_to_jiffies(msecs) + 1;

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

EXPORT_SYMBOL(msleep);

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 int __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;
    return schedule_hrtimeout_range(&kmin, delta, HRTIMER_MODE_REL);
}

void usleep_range(unsigned long min, unsigned long max)
{
    __set_current_state(TASK_UNINTERRUPTIBLE);
    do_usleep_range(min, max);
}
EXPORT_SYMBOL(usleep_range);