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

#ifndef DDE_LINUX

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)

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;
        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;

/*
 * Note that all tvec_bases are 2 byte aligned and lower bit of
 * base in timer_list is guaranteed to be zero. Use the LSB for
 * the new flag to indicate whether the timer is deferrable
 */
#define TBASE_DEFERRABLE_FLAG           (0x1)

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

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

static inline void timer_set_deferrable(struct timer_list *timer)
{
        timer->base = ((struct tvec_base *)((unsigned long)(timer->base) |
                                       TBASE_DEFERRABLE_FLAG));
}

static inline void
timer_set_base(struct timer_list *timer, struct tvec_base *new_base)
{
        timer->base = (struct tvec_base *)((unsigned long)(new_base) |
                                      tbase_get_deferrable(timer->base));
}
#endif /* DDE_LINUX */

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;
}

/**
 * __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);


#ifndef DDE_LINUX
static inline void set_running_timer(struct tvec_base *base,
                                        struct timer_list *timer)
{
#ifdef CONFIG_SMP
        base->running_timer = timer;
#endif
}

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 0xffffffff on 64-bit
                 * architectures then we use the maximum timeout:
                 */
                if (idx > 0xffffffffUL) {
                        idx = 0xffffffffUL;
                        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);
}

#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 (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;

/*
 * 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;
        }
}

/*
 * 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 {
                        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 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;
        }
}

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

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 void __init_timer(struct timer_list *timer);

void init_timer_on_stack(struct timer_list *timer)
{
        debug_object_init_on_stack(timer, &timer_debug_descr);
        __init_timer(timer);
}
EXPORT_SYMBOL_GPL(init_timer_on_stack);

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) { }
#endif

static void __init_timer(struct timer_list *timer)
{
        timer->entry.next = NULL;
        timer->base = __raw_get_cpu_var(tvec_bases);
#ifdef CONFIG_TIMER_STATS
        timer->start_site = NULL;
        timer->start_pid = -1;
        memset(timer->start_comm, 0, TASK_COMM_LEN);
#endif
}

/**
 * init_timer - initialize a timer.
 * @timer: the timer to be initialized
 *
 * init_timer() must be done to a timer prior calling *any* of the
 * other timer functions.
 */
void init_timer(struct timer_list *timer)
{
        debug_timer_init(timer);
        __init_timer(timer);
}
EXPORT_SYMBOL(init_timer);

void init_timer_deferrable(struct timer_list *timer)
{
        init_timer(timer);
        timer_set_deferrable(timer);
}
EXPORT_SYMBOL(init_timer_deferrable);

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

        debug_timer_deactivate(timer);

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

/*
 * 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();
        }
}

int __mod_timer(struct timer_list *timer, unsigned long expires)
{
        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);

        if (timer_pending(timer)) {
                detach_timer(timer, 0);
                ret = 1;
        }

        debug_timer_activate(timer);

        new_base = __get_cpu_var(tvec_bases);

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

        return ret;
}

EXPORT_SYMBOL(__mod_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(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_timer_activate(timer);
        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);
}

/**
 * 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)
{
        BUG_ON(!timer->function);

        timer_stats_timer_set_start_info(timer);
        /*
         * 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->expires == expires && timer_pending(timer))
                return 1;

        return __mod_timer(timer, expires);
}

EXPORT_SYMBOL(mod_timer);

/**
 * 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;

        timer_stats_timer_clear_start_info(timer);
        if (timer_pending(timer)) {
                base = lock_timer_base(timer, &flags);
                if (timer_pending(timer)) {
                        detach_timer(timer, 1);
                        ret = 1;
                }
                spin_unlock_irqrestore(&base->lock, flags);
        }

        return ret;
}

EXPORT_SYMBOL(del_timer);

#ifdef CONFIG_SMP
/**
 * 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.
 *
 * It must not be called from interrupt contexts.
 */
int try_to_del_timer_sync(struct timer_list *timer)
{
        struct tvec_base *base;
        unsigned long flags;
        int ret = -1;

        base = lock_timer_base(timer, &flags);

        if (base->running_timer == timer)
                goto out;

        ret = 0;
        if (timer_pending(timer)) {
                detach_timer(timer, 1);
                ret = 1;
        }
out:
        spin_unlock_irqrestore(&base->lock, flags);

        return ret;
}

EXPORT_SYMBOL(try_to_del_timer_sync);

/**
 * 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. 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.
 *
 * The function returns whether it has deactivated a pending timer or not.
 */
int del_timer_sync(struct timer_list *timer)
{
        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);
                internal_add_timer(base, timer);
        }

        return index;
}

#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 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;

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

                        timer_stats_account_timer(timer);

                        set_running_timer(base, timer);
                        detach_timer(timer, 1);
                        spin_unlock_irq(&base->lock);
                        {
                                int preempt_count = preempt_count();
                                fn(data);
                                if (preempt_count != preempt_count()) {
                                        printk(KERN_ERR "huh, entered %p "
                                               "with preempt_count %08x, exited"
                                               " with %08x?\n",
                                               fn, preempt_count,
                                               preempt_count());
                                        BUG();
                                }
                        }
                        spin_lock_irq(&base->lock);
                }
        }
        set_running_timer(base, 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 cpus is idle.
 * This functions needs to be called 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) {
                                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;
}

/**
 * get_next_timer_interrupt - return the jiffy of the next pending timer
 * @now: current time (in jiffies)
 */
unsigned long get_next_timer_interrupt(unsigned long now)
{
        struct tvec_base *base = __get_cpu_var(tvec_bases);
        unsigned long expires;

        spin_lock(&base->lock);
        expires = __next_timer_interrupt(base);
        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();
        if (rcu_pending(cpu))
                rcu_check_callbacks(cpu, user_tick);
        printk_tick();
        scheduler_tick();
        run_posix_cpu_timers(p);
}

/*
 * Nr of active tasks - counted in fixed-point numbers
 */
static unsigned long count_active_tasks(void)
{
        return nr_active() * FIXED_1;
}

/*
 * Hmm.. Changed this, as the GNU make sources (load.c) seems to
 * imply that avenrun[] is the standard name for this kind of thing.
 * Nothing else seems to be standardized: the fractional size etc
 * all seem to differ on different machines.
 *
 * Requires xtime_lock to access.
 */
unsigned long avenrun[3];

EXPORT_SYMBOL(avenrun);

/*
 * calc_load - given tick count, update the avenrun load estimates.
 * This is called while holding a write_lock on xtime_lock.
 */
static inline void calc_load(unsigned long ticks)
{
        unsigned long active_tasks; /* fixed-point */
        static int count = LOAD_FREQ;

        count -= ticks;
        if (unlikely(count < 0)) {
                active_tasks = count_active_tasks();
                do {
                        CALC_LOAD(avenrun[0], EXP_1, active_tasks);
                        CALC_LOAD(avenrun[1], EXP_5, active_tasks);
                        CALC_LOAD(avenrun[2], EXP_15, active_tasks);
                        count += LOAD_FREQ;
                } while (count < 0);
        }
}

/*
 * 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 = __get_cpu_var(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);
        softlockup_tick();
}

/*
 * Called by the timer interrupt. xtime_lock must already be taken
 * by the timer IRQ!
 */
static inline void update_times(unsigned long ticks)
{
        update_wall_time();
        calc_load(ticks);
}

/*
 * The 64-bit jiffies value is not atomic - you MUST NOT read it
 * without sampling the sequence number in xtime_lock.
 * jiffies is defined in the linker script...
 */

void do_timer(unsigned long ticks)
{
        jiffies_64 += ticks;
        update_times(ticks);
}

#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

#ifndef __alpha__

/*
 * The Alpha uses getxpid, getxuid, and getxgid instead.  Maybe this
 * should be moved into arch/i386 instead?
 */

/**
 * sys_getpid - return the thread group id of the current process
 *
 * Note, despite the name, this returns the tgid not the pid.  The tgid and
 * the pid are identical unless CLONE_THREAD was specified on clone() in
 * which case the tgid is the same in all threads of the same group.
 *
 * This is SMP safe as current->tgid does not change.
 */
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(current->real_parent);
        rcu_read_unlock();

        return pid;
}

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

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

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

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

#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);
        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);
}

/**
 * do_sysinfo - fill in sysinfo struct
 * @info: pointer to buffer to fill
 */
int do_sysinfo(struct sysinfo *info)
{
        unsigned long mem_total, sav_total;
        unsigned int mem_unit, bitcount;
        unsigned long seq;

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

        do {
                struct timespec tp;
                seq = read_seqbegin(&xtime_lock);

                /*
                 * This is annoying.  The below is the same thing
                 * posix_get_clock_monotonic() does, but it wants to
                 * take the lock which we want to cover the loads stuff
                 * too.
                 */

                getnstimeofday(&tp);
                tp.tv_sec += wall_to_monotonic.tv_sec;
                tp.tv_nsec += wall_to_monotonic.tv_nsec;
                monotonic_to_bootbased(&tp);
                if (tp.tv_nsec - NSEC_PER_SEC >= 0) {
                        tp.tv_nsec = tp.tv_nsec - NSEC_PER_SEC;
                        tp.tv_sec++;
                }
                info->uptime = tp.tv_sec + (tp.tv_nsec ? 1 : 0);

                info->loads[0] = avenrun[0] << (SI_LOAD_SHIFT - FSHIFT);
                info->loads[1] = avenrun[1] << (SI_LOAD_SHIFT - FSHIFT);
                info->loads[2] = avenrun[2] << (SI_LOAD_SHIFT - FSHIFT);

                info->procs = nr_threads;
        } while (read_seqretry(&xtime_lock, seq));

        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 <andersee@debian.org>
         */

        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;
        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);
                detach_timer(timer, 0);
                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;
        switch(action) {
        case CPU_UP_PREPARE:
        case CPU_UP_PREPARE_FROZEN:
                if (init_timers_cpu(cpu) < 0)
                        return NOTIFY_BAD;
                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 = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
                                (void *)(long)smp_processor_id());

        init_timer_stats();

        BUG_ON(err == NOTIFY_BAD);
        register_cpu_notifier(&timers_nb);
        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);
#endif /* DDE */

/**
 * 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);

---