[PATCH] kernel-doc for kernel/resource.c

[linux-2.6.22.y-op.git] / kernel / timer.c

/*
 *  linux/kernel/timer.c
 *
 *  Kernel internal timers, kernel timekeeping, 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/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 <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/div64.h>
#include <asm/timex.h>
#include <asm/io.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)

typedef struct tvec_s {
        struct list_head vec[TVN_SIZE];
} tvec_t;

typedef struct tvec_root_s {
        struct list_head vec[TVR_SIZE];
} tvec_root_t;

struct tvec_t_base_s {
        spinlock_t lock;
        struct timer_list *running_timer;
        unsigned long timer_jiffies;
        tvec_root_t tv1;
        tvec_t tv2;
        tvec_t tv3;
        tvec_t tv4;
        tvec_t tv5;
} ____cacheline_aligned_in_smp;

typedef struct tvec_t_base_s tvec_base_t;

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

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

static void internal_add_timer(tvec_base_t *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);
}

/**
 * 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 fastcall init_timer(struct timer_list *timer)
{
        timer->entry.next = NULL;
        timer->base = __raw_get_cpu_var(tvec_bases);
}
EXPORT_SYMBOL(init_timer);

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

        __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 tvec_base_t *lock_timer_base(struct timer_list *timer,
                                        unsigned long *flags)
        __acquires(timer->base->lock)
{
        tvec_base_t *base;

        for (;;) {
                base = timer->base;
                if (likely(base != NULL)) {
                        spin_lock_irqsave(&base->lock, *flags);
                        if (likely(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)
{
        tvec_base_t *base, *new_base;
        unsigned long flags;
        int ret = 0;

        BUG_ON(!timer->function);

        base = lock_timer_base(timer, &flags);

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

        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->base = NULL;
                        spin_unlock(&base->lock);
                        base = new_base;
                        spin_lock(&base->lock);
                        timer->base = 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)
{
        tvec_base_t *base = per_cpu(tvec_bases, cpu);
        unsigned long flags;

        BUG_ON(timer_pending(timer) || !timer->function);
        spin_lock_irqsave(&base->lock, flags);
        timer->base = base;
        internal_add_timer(base, timer);
        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);

        /*
         * 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)
{
        tvec_base_t *base;
        unsigned long flags;
        int ret = 0;

        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)
{
        tvec_base_t *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;
}

/**
 * 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(tvec_base_t *base, tvec_t *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(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(tvec_base_t *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_entry(head->next,struct timer_list,entry);
                        fn = timer->function;
                        data = timer->data;

                        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_WARNING "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_IDLE_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.
 */
unsigned long next_timer_interrupt(void)
{
        tvec_base_t *base;
        struct list_head *list;
        struct timer_list *nte;
        unsigned long expires;
        unsigned long hr_expires = MAX_JIFFY_OFFSET;
        ktime_t hr_delta;
        tvec_t *varray[4];
        int i, j;

        hr_delta = hrtimer_get_next_event();
        if (hr_delta.tv64 != KTIME_MAX) {
                struct timespec tsdelta;
                tsdelta = ktime_to_timespec(hr_delta);
                hr_expires = timespec_to_jiffies(&tsdelta);
                if (hr_expires < 3)
                        return hr_expires + jiffies;
        }
        hr_expires += jiffies;

        base = __get_cpu_var(tvec_bases);
        spin_lock(&base->lock);
        expires = base->timer_jiffies + (LONG_MAX >> 1);
        list = NULL;

        /* Look for timer events in tv1. */
        j = base->timer_jiffies & TVR_MASK;
        do {
                list_for_each_entry(nte, base->tv1.vec + j, entry) {
                        expires = nte->expires;
                        if (j < (base->timer_jiffies & TVR_MASK))
                                list = base->tv2.vec + (INDEX(0));
                        goto found;
                }
                j = (j + 1) & TVR_MASK;
        } while (j != (base->timer_jiffies & TVR_MASK));

        /* Check tv2-tv5. */
        varray[0] = &base->tv2;
        varray[1] = &base->tv3;
        varray[2] = &base->tv4;
        varray[3] = &base->tv5;
        for (i = 0; i < 4; i++) {
                j = INDEX(i);
                do {
                        if (list_empty(varray[i]->vec + j)) {
                                j = (j + 1) & TVN_MASK;
                                continue;
                        }
                        list_for_each_entry(nte, varray[i]->vec + j, entry)
                                if (time_before(nte->expires, expires))
                                        expires = nte->expires;
                        if (j < (INDEX(i)) && i < 3)
                                list = varray[i + 1]->vec + (INDEX(i + 1));
                        goto found;
                } while (j != (INDEX(i)));
        }
found:
        if (list) {
                /*
                 * The search wrapped. We need to look at the next list
                 * from next tv element that would cascade into tv element
                 * where we found the timer element.
                 */
                list_for_each_entry(nte, list, entry) {
                        if (time_before(nte->expires, expires))
                                expires = nte->expires;
                }
        }
        spin_unlock(&base->lock);

        /*
         * It can happen that other CPUs service timer IRQs and increment
         * jiffies, but we have not yet got a local timer tick to process
         * the timer wheels.  In that case, the expiry time can be before
         * jiffies, but since the high-resolution timer here is relative to
         * jiffies, the default expression when high-resolution timers are
         * not active,
         *
         *   time_before(MAX_JIFFY_OFFSET + jiffies, expires)
         *
         * would falsely evaluate to true.  If that is the case, just
         * return jiffies so that we can immediately fire the local timer
         */
        if (time_before(expires, jiffies))
                return jiffies;

        if (time_before(hr_expires, expires))
                return hr_expires;

        return expires;
}
#endif

/******************************************************************/

/* 
 * The current time 
 * wall_to_monotonic is what we need to add to xtime (or xtime corrected 
 * for sub jiffie times) to get to monotonic time.  Monotonic is pegged
 * at zero at system boot time, so wall_to_monotonic will be negative,
 * however, we will ALWAYS keep the tv_nsec part positive so we can use
 * the usual normalization.
 */
struct timespec xtime __attribute__ ((aligned (16)));
struct timespec wall_to_monotonic __attribute__ ((aligned (16)));

EXPORT_SYMBOL(xtime);


/* XXX - all of this timekeeping code should be later moved to time.c */
#include <linux/clocksource.h>
static struct clocksource *clock; /* pointer to current clocksource */

#ifdef CONFIG_GENERIC_TIME
/**
 * __get_nsec_offset - Returns nanoseconds since last call to periodic_hook
 *
 * private function, must hold xtime_lock lock when being
 * called. Returns the number of nanoseconds since the
 * last call to update_wall_time() (adjusted by NTP scaling)
 */
static inline s64 __get_nsec_offset(void)
{
        cycle_t cycle_now, cycle_delta;
        s64 ns_offset;

        /* read clocksource: */
        cycle_now = clocksource_read(clock);

        /* calculate the delta since the last update_wall_time: */
        cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;

        /* convert to nanoseconds: */
        ns_offset = cyc2ns(clock, cycle_delta);

        return ns_offset;
}

/**
 * __get_realtime_clock_ts - Returns the time of day in a timespec
 * @ts:         pointer to the timespec to be set
 *
 * Returns the time of day in a timespec. Used by
 * do_gettimeofday() and get_realtime_clock_ts().
 */
static inline void __get_realtime_clock_ts(struct timespec *ts)
{
        unsigned long seq;
        s64 nsecs;

        do {
                seq = read_seqbegin(&xtime_lock);

                *ts = xtime;
                nsecs = __get_nsec_offset();

        } while (read_seqretry(&xtime_lock, seq));

        timespec_add_ns(ts, nsecs);
}

/**
 * getnstimeofday - Returns the time of day in a timespec
 * @ts:         pointer to the timespec to be set
 *
 * Returns the time of day in a timespec.
 */
void getnstimeofday(struct timespec *ts)
{
        __get_realtime_clock_ts(ts);
}

EXPORT_SYMBOL(getnstimeofday);

/**
 * do_gettimeofday - Returns the time of day in a timeval
 * @tv:         pointer to the timeval to be set
 *
 * NOTE: Users should be converted to using get_realtime_clock_ts()
 */
void do_gettimeofday(struct timeval *tv)
{
        struct timespec now;

        __get_realtime_clock_ts(&now);
        tv->tv_sec = now.tv_sec;
        tv->tv_usec = now.tv_nsec/1000;
}

EXPORT_SYMBOL(do_gettimeofday);
/**
 * do_settimeofday - Sets the time of day
 * @tv:         pointer to the timespec variable containing the new time
 *
 * Sets the time of day to the new time and update NTP and notify hrtimers
 */
int do_settimeofday(struct timespec *tv)
{
        unsigned long flags;
        time_t wtm_sec, sec = tv->tv_sec;
        long wtm_nsec, nsec = tv->tv_nsec;

        if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
                return -EINVAL;

        write_seqlock_irqsave(&xtime_lock, flags);

        nsec -= __get_nsec_offset();

        wtm_sec  = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
        wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);

        set_normalized_timespec(&xtime, sec, nsec);
        set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);

        clock->error = 0;
        ntp_clear();

        write_sequnlock_irqrestore(&xtime_lock, flags);

        /* signal hrtimers about time change */
        clock_was_set();

        return 0;
}

EXPORT_SYMBOL(do_settimeofday);

/**
 * change_clocksource - Swaps clocksources if a new one is available
 *
 * Accumulates current time interval and initializes new clocksource
 */
static int change_clocksource(void)
{
        struct clocksource *new;
        cycle_t now;
        u64 nsec;
        new = clocksource_get_next();
        if (clock != new) {
                now = clocksource_read(new);
                nsec =  __get_nsec_offset();
                timespec_add_ns(&xtime, nsec);

                clock = new;
                clock->cycle_last = now;
                printk(KERN_INFO "Time: %s clocksource has been installed.\n",
                                        clock->name);
                return 1;
        } else if (clock->update_callback) {
                return clock->update_callback();
        }
        return 0;
}
#else
#define change_clocksource() (0)
#endif

/**
 * timeofday_is_continuous - check to see if timekeeping is free running
 */
int timekeeping_is_continuous(void)
{
        unsigned long seq;
        int ret;

        do {
                seq = read_seqbegin(&xtime_lock);

                ret = clock->is_continuous;

        } while (read_seqretry(&xtime_lock, seq));

        return ret;
}

/*
 * timekeeping_init - Initializes the clocksource and common timekeeping values
 */
void __init timekeeping_init(void)
{
        unsigned long flags;

        write_seqlock_irqsave(&xtime_lock, flags);

        ntp_clear();

        clock = clocksource_get_next();
        clocksource_calculate_interval(clock, tick_nsec);
        clock->cycle_last = clocksource_read(clock);

        write_sequnlock_irqrestore(&xtime_lock, flags);
}


static int timekeeping_suspended;
/**
 * timekeeping_resume - Resumes the generic timekeeping subsystem.
 * @dev:        unused
 *
 * This is for the generic clocksource timekeeping.
 * xtime/wall_to_monotonic/jiffies/etc are
 * still managed by arch specific suspend/resume code.
 */
static int timekeeping_resume(struct sys_device *dev)
{
        unsigned long flags;

        write_seqlock_irqsave(&xtime_lock, flags);
        /* restart the last cycle value */
        clock->cycle_last = clocksource_read(clock);
        clock->error = 0;
        timekeeping_suspended = 0;
        write_sequnlock_irqrestore(&xtime_lock, flags);
        return 0;
}

static int timekeeping_suspend(struct sys_device *dev, pm_message_t state)
{
        unsigned long flags;

        write_seqlock_irqsave(&xtime_lock, flags);
        timekeeping_suspended = 1;
        write_sequnlock_irqrestore(&xtime_lock, flags);
        return 0;
}

/* sysfs resume/suspend bits for timekeeping */
static struct sysdev_class timekeeping_sysclass = {
        .resume         = timekeeping_resume,
        .suspend        = timekeeping_suspend,
        set_kset_name("timekeeping"),
};

static struct sys_device device_timer = {
        .id             = 0,
        .cls            = &timekeeping_sysclass,
};

static int __init timekeeping_init_device(void)
{
        int error = sysdev_class_register(&timekeeping_sysclass);
        if (!error)
                error = sysdev_register(&device_timer);
        return error;
}

device_initcall(timekeeping_init_device);

/*
 * If the error is already larger, we look ahead even further
 * to compensate for late or lost adjustments.
 */
static __always_inline int clocksource_bigadjust(s64 error, s64 *interval, s64 *offset)
{
        s64 tick_error, i;
        u32 look_ahead, adj;
        s32 error2, mult;

        /*
         * Use the current error value to determine how much to look ahead.
         * The larger the error the slower we adjust for it to avoid problems
         * with losing too many ticks, otherwise we would overadjust and
         * produce an even larger error.  The smaller the adjustment the
         * faster we try to adjust for it, as lost ticks can do less harm
         * here.  This is tuned so that an error of about 1 msec is adusted
         * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks).
         */
        error2 = clock->error >> (TICK_LENGTH_SHIFT + 22 - 2 * SHIFT_HZ);
        error2 = abs(error2);
        for (look_ahead = 0; error2 > 0; look_ahead++)
                error2 >>= 2;

        /*
         * Now calculate the error in (1 << look_ahead) ticks, but first
         * remove the single look ahead already included in the error.
         */
        tick_error = current_tick_length() >> (TICK_LENGTH_SHIFT - clock->shift + 1);
        tick_error -= clock->xtime_interval >> 1;
        error = ((error - tick_error) >> look_ahead) + tick_error;

        /* Finally calculate the adjustment shift value.  */
        i = *interval;
        mult = 1;
        if (error < 0) {
                error = -error;
                *interval = -*interval;
                *offset = -*offset;
                mult = -1;
        }
        for (adj = 0; error > i; adj++)
                error >>= 1;

        *interval <<= adj;
        *offset <<= adj;
        return mult << adj;
}

/*
 * Adjust the multiplier to reduce the error value,
 * this is optimized for the most common adjustments of -1,0,1,
 * for other values we can do a bit more work.
 */
static void clocksource_adjust(struct clocksource *clock, s64 offset)
{
        s64 error, interval = clock->cycle_interval;
        int adj;

        error = clock->error >> (TICK_LENGTH_SHIFT - clock->shift - 1);
        if (error > interval) {
                error >>= 2;
                if (likely(error <= interval))
                        adj = 1;
                else
                        adj = clocksource_bigadjust(error, &interval, &offset);
        } else if (error < -interval) {
                error >>= 2;
                if (likely(error >= -interval)) {
                        adj = -1;
                        interval = -interval;
                        offset = -offset;
                } else
                        adj = clocksource_bigadjust(error, &interval, &offset);
        } else
                return;

        clock->mult += adj;
        clock->xtime_interval += interval;
        clock->xtime_nsec -= offset;
        clock->error -= (interval - offset) << (TICK_LENGTH_SHIFT - clock->shift);
}

/**
 * update_wall_time - Uses the current clocksource to increment the wall time
 *
 * Called from the timer interrupt, must hold a write on xtime_lock.
 */
static void update_wall_time(void)
{
        cycle_t offset;

        /* Make sure we're fully resumed: */
        if (unlikely(timekeeping_suspended))
                return;

#ifdef CONFIG_GENERIC_TIME
        offset = (clocksource_read(clock) - clock->cycle_last) & clock->mask;
#else
        offset = clock->cycle_interval;
#endif
        clock->xtime_nsec += (s64)xtime.tv_nsec << clock->shift;

        /* normally this loop will run just once, however in the
         * case of lost or late ticks, it will accumulate correctly.
         */
        while (offset >= clock->cycle_interval) {
                /* accumulate one interval */
                clock->xtime_nsec += clock->xtime_interval;
                clock->cycle_last += clock->cycle_interval;
                offset -= clock->cycle_interval;

                if (clock->xtime_nsec >= (u64)NSEC_PER_SEC << clock->shift) {
                        clock->xtime_nsec -= (u64)NSEC_PER_SEC << clock->shift;
                        xtime.tv_sec++;
                        second_overflow();
                }

                /* interpolator bits */
                time_interpolator_update(clock->xtime_interval
                                                >> clock->shift);

                /* accumulate error between NTP and clock interval */
                clock->error += current_tick_length();
                clock->error -= clock->xtime_interval << (TICK_LENGTH_SHIFT - clock->shift);
        }

        /* correct the clock when NTP error is too big */
        clocksource_adjust(clock, offset);

        /* store full nanoseconds into xtime */
        xtime.tv_nsec = (s64)clock->xtime_nsec >> clock->shift;
        clock->xtime_nsec -= (s64)xtime.tv_nsec << clock->shift;

        /* check to see if there is a new clocksource to use */
        if (change_clocksource()) {
                clock->error = 0;
                clock->xtime_nsec = 0;
                clocksource_calculate_interval(clock, tick_nsec);
        }
}

/*
 * 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. */
        if (user_tick)
                account_user_time(p, jiffies_to_cputime(1));
        else
                account_system_time(p, HARDIRQ_OFFSET, jiffies_to_cputime(1));
        run_local_timers();
        if (rcu_pending(cpu))
                rcu_check_callbacks(cpu, user_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;

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

/*
 * This read-write spinlock protects us from races in SMP while
 * playing with xtime and avenrun.
 */
#ifndef ARCH_HAVE_XTIME_LOCK
__cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock);

EXPORT_SYMBOL(xtime_lock);
#endif

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

        hrtimer_run_queues();
        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)
{
        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.
 */
asmlinkage unsigned long sys_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.
 */
asmlinkage long sys_getpid(void)
{
        return current->tgid;
}

/*
 * 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).
 */
asmlinkage long sys_getppid(void)
{
        int pid;

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

        return pid;
}

asmlinkage long sys_getuid(void)
{
        /* Only we change this so SMP safe */
        return current->uid;
}

asmlinkage long sys_geteuid(void)
{
        /* Only we change this so SMP safe */
        return current->euid;
}

asmlinkage long sys_getgid(void)
{
        /* Only we change this so SMP safe */
        return current->gid;
}

asmlinkage long sys_getegid(void)
{
        /* 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.
 */
fastcall 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 from %p\n", timeout,
                                __builtin_return_address(0));
                        current->state = TASK_RUNNING;
                        goto out;
                }
        }

        expire = timeout + jiffies;

        setup_timer(&timer, process_timeout, (unsigned long)current);
        __mod_timer(&timer, expire);
        schedule();
        del_singleshot_timer_sync(&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_uninterruptible(signed long timeout)
{
        __set_current_state(TASK_UNINTERRUPTIBLE);
        return schedule_timeout(timeout);
}
EXPORT_SYMBOL(schedule_timeout_uninterruptible);

/* Thread ID - the internal kernel "pid" */
asmlinkage long sys_gettid(void)
{
        return current->pid;
}

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

        memset((char *)&val, 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;
                if (tp.tv_nsec - NSEC_PER_SEC >= 0) {
                        tp.tv_nsec = tp.tv_nsec - NSEC_PER_SEC;
                        tp.tv_sec++;
                }
                val.uptime = tp.tv_sec + (tp.tv_nsec ? 1 : 0);

                val.loads[0] = avenrun[0] << (SI_LOAD_SHIFT - FSHIFT);
                val.loads[1] = avenrun[1] << (SI_LOAD_SHIFT - FSHIFT);
                val.loads[2] = avenrun[2] << (SI_LOAD_SHIFT - FSHIFT);

                val.procs = nr_threads;
        } while (read_seqretry(&xtime_lock, seq));

        si_meminfo(&val);
        si_swapinfo(&val);

        /*
         * 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 = val.totalram + val.totalswap;
        if (mem_total < val.totalram || mem_total < val.totalswap)
                goto out;
        bitcount = 0;
        mem_unit = val.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
         * val.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...
         */

        val.mem_unit = 1;
        val.totalram <<= bitcount;
        val.freeram <<= bitcount;
        val.sharedram <<= bitcount;
        val.bufferram <<= bitcount;
        val.totalswap <<= bitcount;
        val.freeswap <<= bitcount;
        val.totalhigh <<= bitcount;
        val.freehigh <<= bitcount;

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

        return 0;
}

/*
 * lockdep: we want to track each per-CPU base as a separate lock-class,
 * but timer-bases are kmalloc()-ed, so we need to attach separate
 * keys to them:
 */
static struct lock_class_key base_lock_keys[NR_CPUS];

static int __devinit init_timers_cpu(int cpu)
{
        int j;
        tvec_base_t *base;
        static char __devinitdata 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,
                                                cpu_to_node(cpu));
                        if (!base)
                                return -ENOMEM;
                        memset(base, 0, sizeof(*base));
                        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);
        lockdep_set_class(&base->lock, base_lock_keys + cpu);

        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(tvec_base_t *new_base, struct list_head *head)
{
        struct timer_list *timer;

        while (!list_empty(head)) {
                timer = list_entry(head->next, struct timer_list, entry);
                detach_timer(timer, 0);
                timer->base = new_base;
                internal_add_timer(new_base, timer);
        }
}

static void __devinit migrate_timers(int cpu)
{
        tvec_base_t *old_base;
        tvec_base_t *new_base;
        int i;

        BUG_ON(cpu_online(cpu));
        old_base = per_cpu(tvec_bases, cpu);
        new_base = get_cpu_var(tvec_bases);

        local_irq_disable();
        spin_lock(&new_base->lock);
        spin_lock(&old_base->lock);

        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(&new_base->lock);
        local_irq_enable();
        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:
                if (init_timers_cpu(cpu) < 0)
                        return NOTIFY_BAD;
                break;
#ifdef CONFIG_HOTPLUG_CPU
        case CPU_DEAD:
                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());

        BUG_ON(err == NOTIFY_BAD);
        register_cpu_notifier(&timers_nb);
        open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL);
}

#ifdef CONFIG_TIME_INTERPOLATION

struct time_interpolator *time_interpolator __read_mostly;
static struct time_interpolator *time_interpolator_list __read_mostly;
static DEFINE_SPINLOCK(time_interpolator_lock);

static inline u64 time_interpolator_get_cycles(unsigned int src)
{
        unsigned long (*x)(void);

        switch (src)
        {
                case TIME_SOURCE_FUNCTION:
                        x = time_interpolator->addr;
                        return x();

                case TIME_SOURCE_MMIO64 :
                        return readq_relaxed((void __iomem *)time_interpolator->addr);

                case TIME_SOURCE_MMIO32 :
                        return readl_relaxed((void __iomem *)time_interpolator->addr);

                default: return get_cycles();
        }
}

static inline u64 time_interpolator_get_counter(int writelock)
{
        unsigned int src = time_interpolator->source;

        if (time_interpolator->jitter)
        {
                u64 lcycle;
                u64 now;

                do {
                        lcycle = time_interpolator->last_cycle;
                        now = time_interpolator_get_cycles(src);
                        if (lcycle && time_after(lcycle, now))
                                return lcycle;

                        /* When holding the xtime write lock, there's no need
                         * to add the overhead of the cmpxchg.  Readers are
                         * force to retry until the write lock is released.
                         */
                        if (writelock) {
                                time_interpolator->last_cycle = now;
                                return now;
                        }
                        /* Keep track of the last timer value returned. The use of cmpxchg here
                         * will cause contention in an SMP environment.
                         */
                } while (unlikely(cmpxchg(&time_interpolator->last_cycle, lcycle, now) != lcycle));
                return now;
        }
        else
                return time_interpolator_get_cycles(src);
}

void time_interpolator_reset(void)
{
        time_interpolator->offset = 0;
        time_interpolator->last_counter = time_interpolator_get_counter(1);
}

#define GET_TI_NSECS(count,i) (((((count) - i->last_counter) & (i)->mask) * (i)->nsec_per_cyc) >> (i)->shift)

unsigned long time_interpolator_get_offset(void)
{
        /* If we do not have a time interpolator set up then just return zero */
        if (!time_interpolator)
                return 0;

        return time_interpolator->offset +
                GET_TI_NSECS(time_interpolator_get_counter(0), time_interpolator);
}

#define INTERPOLATOR_ADJUST 65536
#define INTERPOLATOR_MAX_SKIP 10*INTERPOLATOR_ADJUST

void time_interpolator_update(long delta_nsec)
{
        u64 counter;
        unsigned long offset;

        /* If there is no time interpolator set up then do nothing */
        if (!time_interpolator)
                return;

        /*
         * The interpolator compensates for late ticks by accumulating the late
         * time in time_interpolator->offset. A tick earlier than expected will
         * lead to a reset of the offset and a corresponding jump of the clock
         * forward. Again this only works if the interpolator clock is running
         * slightly slower than the regular clock and the tuning logic insures
         * that.
         */

        counter = time_interpolator_get_counter(1);
        offset = time_interpolator->offset +
                        GET_TI_NSECS(counter, time_interpolator);

        if (delta_nsec < 0 || (unsigned long) delta_nsec < offset)
                time_interpolator->offset = offset - delta_nsec;
        else {
                time_interpolator->skips++;
                time_interpolator->ns_skipped += delta_nsec - offset;
                time_interpolator->offset = 0;
        }
        time_interpolator->last_counter = counter;

        /* Tuning logic for time interpolator invoked every minute or so.
         * Decrease interpolator clock speed if no skips occurred and an offset is carried.
         * Increase interpolator clock speed if we skip too much time.
         */
        if (jiffies % INTERPOLATOR_ADJUST == 0)
        {
                if (time_interpolator->skips == 0 && time_interpolator->offset > tick_nsec)
                        time_interpolator->nsec_per_cyc--;
                if (time_interpolator->ns_skipped > INTERPOLATOR_MAX_SKIP && time_interpolator->offset == 0)
                        time_interpolator->nsec_per_cyc++;
                time_interpolator->skips = 0;
                time_interpolator->ns_skipped = 0;
        }
}

static inline int
is_better_time_interpolator(struct time_interpolator *new)
{
        if (!time_interpolator)
                return 1;
        return new->frequency > 2*time_interpolator->frequency ||
            (unsigned long)new->drift < (unsigned long)time_interpolator->drift;
}

void
register_time_interpolator(struct time_interpolator *ti)
{
        unsigned long flags;

        /* Sanity check */
        BUG_ON(ti->frequency == 0 || ti->mask == 0);

        ti->nsec_per_cyc = ((u64)NSEC_PER_SEC << ti->shift) / ti->frequency;
        spin_lock(&time_interpolator_lock);
        write_seqlock_irqsave(&xtime_lock, flags);
        if (is_better_time_interpolator(ti)) {
                time_interpolator = ti;
                time_interpolator_reset();
        }
        write_sequnlock_irqrestore(&xtime_lock, flags);

        ti->next = time_interpolator_list;
        time_interpolator_list = ti;
        spin_unlock(&time_interpolator_lock);
}

void
unregister_time_interpolator(struct time_interpolator *ti)
{
        struct time_interpolator *curr, **prev;
        unsigned long flags;

        spin_lock(&time_interpolator_lock);
        prev = &time_interpolator_list;
        for (curr = *prev; curr; curr = curr->next) {
                if (curr == ti) {
                        *prev = curr->next;
                        break;
                }
                prev = &curr->next;
        }

        write_seqlock_irqsave(&xtime_lock, flags);
        if (ti == time_interpolator) {
                /* we lost the best time-interpolator: */
                time_interpolator = NULL;
                /* find the next-best interpolator */
                for (curr = time_interpolator_list; curr; curr = curr->next)
                        if (is_better_time_interpolator(curr))
                                time_interpolator = curr;
                time_interpolator_reset();
        }
        write_sequnlock_irqrestore(&xtime_lock, flags);
        spin_unlock(&time_interpolator_lock);
}
#endif /* CONFIG_TIME_INTERPOLATION */

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

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

EXPORT_SYMBOL(msleep);

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

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

EXPORT_SYMBOL(msleep_interruptible);