/*
   *  linux/kernel/hrtimer.c
   *
   *  Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
   *  Copyright(C) 2005, Red Hat, Inc., Ingo Molnar
   *
   *  High-resolution kernel timers
   *
   *  In contrast to the low-resolution timeout API implemented in
   *  kernel/timer.c, hrtimers provide finer resolution and accuracy
   *  depending on system configuration and capabilities.
   *
   *  These timers are currently used for:
   *   - itimers
   *   - POSIX timers
   *   - nanosleep
   *   - precise in-kernel timing
   *
   *  Started by: Thomas Gleixner and Ingo Molnar
   *
   *  Credits:
   *	based on kernel/timer.c
   *

   *	Help, testing, suggestions, bugfixes, improvements were
   *	provided by:
   *
   *	George Anzinger, Andrew Morton, Steven Rostedt, Roman Zippel
   *	et. al.
   *

   *  For licencing details see kernel-base/COPYING
   */
  
  #include <linux/cpu.h>
  #include <linux/module.h>
  #include <linux/percpu.h>
  #include <linux/hrtimer.h>
  #include <linux/notifier.h>
  #include <linux/syscalls.h>
  #include <linux/interrupt.h>
  
  #include <asm/uaccess.h>
  
  /**
   * ktime_get - get the monotonic time in ktime_t format
   *
   * returns the time in ktime_t format
   */
  static ktime_t ktime_get(void)
  {
  	struct timespec now;
  
  	ktime_get_ts(&now);
  
  	return timespec_to_ktime(now);
  }
  
  /**
   * ktime_get_real - get the real (wall-) time in ktime_t format
   *
   * returns the time in ktime_t format
   */
  static ktime_t ktime_get_real(void)
  {
  	struct timespec now;
  
  	getnstimeofday(&now);
  
  	return timespec_to_ktime(now);
  }
  
  EXPORT_SYMBOL_GPL(ktime_get_real);
  
  /*
   * The timer bases:

   *
   * Note: If we want to add new timer bases, we have to skip the two
   * clock ids captured by the cpu-timers. We do this by holding empty
   * entries rather than doing math adjustment of the clock ids.
   * This ensures that we capture erroneous accesses to these clock ids
   * rather than moving them into the range of valid clock id's.

   */
  
  #define MAX_HRTIMER_BASES 2
  
  static DEFINE_PER_CPU(struct hrtimer_base, hrtimer_bases[MAX_HRTIMER_BASES]) =
  {
  	{
  		.index = CLOCK_REALTIME,
  		.get_time = &ktime_get_real,
  		.resolution = KTIME_REALTIME_RES,
  	},
  	{
  		.index = CLOCK_MONOTONIC,
  		.get_time = &ktime_get,
  		.resolution = KTIME_MONOTONIC_RES,
  	},
  };
  
  /**
   * ktime_get_ts - get the monotonic clock in timespec format

   * @ts:		pointer to timespec variable
   *
   * The function calculates the monotonic clock from the realtime
   * clock and the wall_to_monotonic offset and stores the result
   * in normalized timespec format in the variable pointed to by ts.
   */
  void ktime_get_ts(struct timespec *ts)
  {
  	struct timespec tomono;
  	unsigned long seq;
  
  	do {
  		seq = read_seqbegin(&xtime_lock);
  		getnstimeofday(ts);
  		tomono = wall_to_monotonic;
  
  	} while (read_seqretry(&xtime_lock, seq));
  
  	set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
  				ts->tv_nsec + tomono.tv_nsec);
  }

  EXPORT_SYMBOL_GPL(ktime_get_ts);

  
  /*

   * Get the coarse grained time at the softirq based on xtime and
   * wall_to_monotonic.
   */
  static void hrtimer_get_softirq_time(struct hrtimer_base *base)
  {
  	ktime_t xtim, tomono;
  	unsigned long seq;
  
  	do {
  		seq = read_seqbegin(&xtime_lock);
  		xtim = timespec_to_ktime(xtime);
  		tomono = timespec_to_ktime(wall_to_monotonic);
  
  	} while (read_seqretry(&xtime_lock, seq));
  
  	base[CLOCK_REALTIME].softirq_time = xtim;
  	base[CLOCK_MONOTONIC].softirq_time = ktime_add(xtim, tomono);
  }
  
  /*

   * Functions and macros which are different for UP/SMP systems are kept in a
   * single place
   */
  #ifdef CONFIG_SMP
  
  #define set_curr_timer(b, t)		do { (b)->curr_timer = (t); } while (0)
  
  /*
   * We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
   * means that all timers which are tied to this base via timer->base are
   * locked, and the base itself is locked too.
   *
   * So __run_timers/migrate_timers can safely modify all timers which could
   * be found on the lists/queues.
   *
   * When the timer's base is locked, and the timer removed from list, it is
   * possible to set timer->base = NULL and drop the lock: the timer remains
   * locked.
   */
  static struct hrtimer_base *lock_hrtimer_base(const struct hrtimer *timer,
  					      unsigned long *flags)
  {
  	struct hrtimer_base *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();
  	}
  }
  
  /*
   * Switch the timer base to the current CPU when possible.
   */
  static inline struct hrtimer_base *
  switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_base *base)
  {
  	struct hrtimer_base *new_base;

  	new_base = &__get_cpu_var(hrtimer_bases)[base->index];

  
  	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,
  		 * so we keep it on the same CPU. No hassle vs. reprogramming
  		 * the event source in the high resolution case. The softirq
  		 * code will take care of this when the timer function has
  		 * completed. There is no conflict as we hold the lock until
  		 * the timer is enqueued.
  		 */
  		if (unlikely(base->curr_timer == timer))
  			return base;
  
  		/* See the comment in lock_timer_base() */
  		timer->base = NULL;
  		spin_unlock(&base->lock);
  		spin_lock(&new_base->lock);
  		timer->base = new_base;
  	}
  	return new_base;
  }
  
  #else /* CONFIG_SMP */
  
  #define set_curr_timer(b, t)		do { } while (0)
  
  static inline struct hrtimer_base *
  lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
  {
  	struct hrtimer_base *base = timer->base;
  
  	spin_lock_irqsave(&base->lock, *flags);
  
  	return base;
  }
  
  #define switch_hrtimer_base(t, b)	(b)
  
  #endif	/* !CONFIG_SMP */
  
  /*
   * Functions for the union type storage format of ktime_t which are
   * too large for inlining:
   */
  #if BITS_PER_LONG < 64
  # ifndef CONFIG_KTIME_SCALAR
  /**
   * ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable

   * @kt:		addend
   * @nsec:	the scalar nsec value to add
   *
   * Returns the sum of kt and nsec in ktime_t format
   */
  ktime_t ktime_add_ns(const ktime_t kt, u64 nsec)
  {
  	ktime_t tmp;
  
  	if (likely(nsec < NSEC_PER_SEC)) {
  		tmp.tv64 = nsec;
  	} else {
  		unsigned long rem = do_div(nsec, NSEC_PER_SEC);
  
  		tmp = ktime_set((long)nsec, rem);
  	}
  
  	return ktime_add(kt, tmp);
  }
  
  #else /* CONFIG_KTIME_SCALAR */
  
  # endif /* !CONFIG_KTIME_SCALAR */
  
  /*
   * Divide a ktime value by a nanosecond value
   */

  static unsigned long ktime_divns(const ktime_t kt, s64 div)

  {
  	u64 dclc, inc, dns;
  	int sft = 0;
  
  	dclc = dns = ktime_to_ns(kt);
  	inc = div;
  	/* Make sure the divisor is less than 2^32: */
  	while (div >> 32) {
  		sft++;
  		div >>= 1;
  	}
  	dclc >>= sft;
  	do_div(dclc, (unsigned long) div);
  
  	return (unsigned long) dclc;
  }
  
  #else /* BITS_PER_LONG < 64 */
  # define ktime_divns(kt, div)		(unsigned long)((kt).tv64 / (div))
  #endif /* BITS_PER_LONG >= 64 */
  
  /*
   * Counterpart to lock_timer_base above:
   */
  static inline
  void unlock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
  {
  	spin_unlock_irqrestore(&timer->base->lock, *flags);
  }
  
  /**
   * hrtimer_forward - forward the timer expiry

   * @timer:	hrtimer to forward

   * @now:	forward past this time

   * @interval:	the interval to forward
   *
   * Forward the timer expiry so it will expire in the future.

   * Returns the number of overruns.

   */
  unsigned long

  hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval)

  {
  	unsigned long orun = 1;

  	ktime_t delta;

  
  	delta = ktime_sub(now, timer->expires);
  
  	if (delta.tv64 < 0)
  		return 0;

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

  	if (unlikely(delta.tv64 >= interval.tv64)) {

  		s64 incr = ktime_to_ns(interval);

  
  		orun = ktime_divns(delta, incr);
  		timer->expires = ktime_add_ns(timer->expires, incr * orun);
  		if (timer->expires.tv64 > now.tv64)
  			return orun;
  		/*
  		 * This (and the ktime_add() below) is the
  		 * correction for exact:
  		 */
  		orun++;
  	}
  	timer->expires = ktime_add(timer->expires, interval);
  
  	return orun;
  }
  
  /*
   * enqueue_hrtimer - internal function to (re)start a timer
   *
   * The timer is inserted in expiry order. Insertion into the
   * red black tree is O(log(n)). Must hold the base lock.
   */
  static void enqueue_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
  {
  	struct rb_node **link = &base->active.rb_node;

  	struct rb_node *parent = NULL;
  	struct hrtimer *entry;
  
  	/*
  	 * Find the right place in the rbtree:
  	 */
  	while (*link) {
  		parent = *link;
  		entry = rb_entry(parent, struct hrtimer, node);
  		/*
  		 * We dont care about collisions. Nodes with
  		 * the same expiry time stay together.
  		 */
  		if (timer->expires.tv64 < entry->expires.tv64)
  			link = &(*link)->rb_left;

  		else

  			link = &(*link)->rb_right;

  	}
  
  	/*

  	 * Insert the timer to the rbtree and check whether it
  	 * replaces the first pending timer

  	 */
  	rb_link_node(&timer->node, parent, link);
  	rb_insert_color(&timer->node, &base->active);

  	if (!base->first || timer->expires.tv64 <
  	    rb_entry(base->first, struct hrtimer, node)->expires.tv64)
  		base->first = &timer->node;
  }

  
  /*
   * __remove_hrtimer - internal function to remove a timer
   *
   * Caller must hold the base lock.
   */
  static void __remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
  {
  	/*

  	 * Remove the timer from the rbtree and replace the
  	 * first entry pointer if necessary.

  	 */

  	if (base->first == &timer->node)
  		base->first = rb_next(&timer->node);

  	rb_erase(&timer->node, &base->active);

  	rb_set_parent(&timer->node, &timer->node);

  }
  
  /*
   * remove hrtimer, called with base lock held
   */
  static inline int
  remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
  {
  	if (hrtimer_active(timer)) {
  		__remove_hrtimer(timer, base);

  		return 1;
  	}
  	return 0;
  }
  
  /**
   * hrtimer_start - (re)start an relative timer on the current CPU

   * @timer:	the timer to be added
   * @tim:	expiry time
   * @mode:	expiry mode: absolute (HRTIMER_ABS) or relative (HRTIMER_REL)
   *
   * Returns:
   *  0 on success
   *  1 when the timer was active
   */
  int
  hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
  {
  	struct hrtimer_base *base, *new_base;
  	unsigned long flags;
  	int ret;
  
  	base = lock_hrtimer_base(timer, &flags);
  
  	/* Remove an active timer from the queue: */
  	ret = remove_hrtimer(timer, base);
  
  	/* Switch the timer base, if necessary: */
  	new_base = switch_hrtimer_base(timer, base);

  	if (mode == HRTIMER_REL) {

  		tim = ktime_add(tim, new_base->get_time());

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

  	timer->expires = tim;
  
  	enqueue_hrtimer(timer, new_base);
  
  	unlock_hrtimer_base(timer, &flags);
  
  	return ret;
  }

  EXPORT_SYMBOL_GPL(hrtimer_start);

  
  /**
   * hrtimer_try_to_cancel - try to deactivate a timer

   * @timer:	hrtimer to stop
   *
   * Returns:
   *  0 when the timer was not active
   *  1 when the timer was active
   * -1 when the timer is currently excuting the callback function and

   *    cannot be stopped

   */
  int hrtimer_try_to_cancel(struct hrtimer *timer)
  {
  	struct hrtimer_base *base;
  	unsigned long flags;
  	int ret = -1;
  
  	base = lock_hrtimer_base(timer, &flags);
  
  	if (base->curr_timer != timer)
  		ret = remove_hrtimer(timer, base);
  
  	unlock_hrtimer_base(timer, &flags);
  
  	return ret;
  
  }

  EXPORT_SYMBOL_GPL(hrtimer_try_to_cancel);

  
  /**
   * hrtimer_cancel - cancel a timer and wait for the handler to finish.

   * @timer:	the timer to be cancelled
   *
   * Returns:
   *  0 when the timer was not active
   *  1 when the timer was active
   */
  int hrtimer_cancel(struct hrtimer *timer)
  {
  	for (;;) {
  		int ret = hrtimer_try_to_cancel(timer);
  
  		if (ret >= 0)
  			return ret;

  		cpu_relax();

  	}
  }

  EXPORT_SYMBOL_GPL(hrtimer_cancel);

  
  /**
   * hrtimer_get_remaining - get remaining time for the timer

   * @timer:	the timer to read
   */
  ktime_t hrtimer_get_remaining(const struct hrtimer *timer)
  {
  	struct hrtimer_base *base;
  	unsigned long flags;
  	ktime_t rem;
  
  	base = lock_hrtimer_base(timer, &flags);
  	rem = ktime_sub(timer->expires, timer->base->get_time());
  	unlock_hrtimer_base(timer, &flags);
  
  	return rem;
  }

  EXPORT_SYMBOL_GPL(hrtimer_get_remaining);

  #ifdef CONFIG_NO_IDLE_HZ
  /**
   * hrtimer_get_next_event - get the time until next expiry event
   *
   * Returns the delta to the next expiry event or KTIME_MAX if no timer
   * is pending.
   */
  ktime_t hrtimer_get_next_event(void)
  {
  	struct hrtimer_base *base = __get_cpu_var(hrtimer_bases);
  	ktime_t delta, mindelta = { .tv64 = KTIME_MAX };
  	unsigned long flags;
  	int i;
  
  	for (i = 0; i < MAX_HRTIMER_BASES; i++, base++) {
  		struct hrtimer *timer;
  
  		spin_lock_irqsave(&base->lock, flags);
  		if (!base->first) {
  			spin_unlock_irqrestore(&base->lock, flags);
  			continue;
  		}
  		timer = rb_entry(base->first, struct hrtimer, node);
  		delta.tv64 = timer->expires.tv64;
  		spin_unlock_irqrestore(&base->lock, flags);
  		delta = ktime_sub(delta, base->get_time());
  		if (delta.tv64 < mindelta.tv64)
  			mindelta.tv64 = delta.tv64;
  	}
  	if (mindelta.tv64 < 0)
  		mindelta.tv64 = 0;
  	return mindelta;
  }
  #endif

  /**

   * hrtimer_init - initialize a timer to the given clock

   * @timer:	the timer to be initialized

   * @clock_id:	the clock to be used

   * @mode:	timer mode abs/rel

   */

  void hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
  		  enum hrtimer_mode mode)

  {
  	struct hrtimer_base *bases;

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

  	bases = __raw_get_cpu_var(hrtimer_bases);

  	if (clock_id == CLOCK_REALTIME && mode != HRTIMER_ABS)
  		clock_id = CLOCK_MONOTONIC;
  
  	timer->base = &bases[clock_id];

  	rb_set_parent(&timer->node, &timer->node);

  }

  EXPORT_SYMBOL_GPL(hrtimer_init);

  
  /**
   * hrtimer_get_res - get the timer resolution for a clock

   * @which_clock: which clock to query
   * @tp:		 pointer to timespec variable to store the resolution
   *
   * Store the resolution of the clock selected by which_clock in the
   * variable pointed to by tp.
   */
  int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
  {
  	struct hrtimer_base *bases;

  	bases = __raw_get_cpu_var(hrtimer_bases);

  	*tp = ktime_to_timespec(bases[which_clock].resolution);

  
  	return 0;
  }

  EXPORT_SYMBOL_GPL(hrtimer_get_res);

  
  /*
   * Expire the per base hrtimer-queue:
   */
  static inline void run_hrtimer_queue(struct hrtimer_base *base)
  {

  	struct rb_node *node;

  	if (!base->first)
  		return;

  	if (base->get_softirq_time)
  		base->softirq_time = base->get_softirq_time();

  	spin_lock_irq(&base->lock);

  	while ((node = base->first)) {

  		struct hrtimer *timer;

  		int (*fn)(struct hrtimer *);

  		int restart;

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

  		if (base->softirq_time.tv64 <= timer->expires.tv64)

  			break;
  
  		fn = timer->function;

  		set_curr_timer(base, timer);
  		__remove_hrtimer(timer, base);
  		spin_unlock_irq(&base->lock);

  		restart = fn(timer);

  
  		spin_lock_irq(&base->lock);

  		if (restart != HRTIMER_NORESTART) {
  			BUG_ON(hrtimer_active(timer));

  			enqueue_hrtimer(timer, base);

  		}

  	}
  	set_curr_timer(base, NULL);
  	spin_unlock_irq(&base->lock);
  }
  
  /*
   * Called from timer softirq every jiffy, expire hrtimers:
   */
  void hrtimer_run_queues(void)
  {
  	struct hrtimer_base *base = __get_cpu_var(hrtimer_bases);
  	int i;

  	hrtimer_get_softirq_time(base);

  	for (i = 0; i < MAX_HRTIMER_BASES; i++)
  		run_hrtimer_queue(&base[i]);
  }
  
  /*

   * Sleep related functions:
   */

  static int hrtimer_wakeup(struct hrtimer *timer)
  {
  	struct hrtimer_sleeper *t =
  		container_of(timer, struct hrtimer_sleeper, timer);
  	struct task_struct *task = t->task;
  
  	t->task = NULL;
  	if (task)
  		wake_up_process(task);
  
  	return HRTIMER_NORESTART;
  }

  void hrtimer_init_sleeper(struct hrtimer_sleeper *sl, struct task_struct *task)

  {
  	sl->timer.function = hrtimer_wakeup;
  	sl->task = task;
  }

  static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode)

  {

  	hrtimer_init_sleeper(t, current);

  	do {
  		set_current_state(TASK_INTERRUPTIBLE);
  		hrtimer_start(&t->timer, t->timer.expires, mode);
  
  		schedule();

  		hrtimer_cancel(&t->timer);
  		mode = HRTIMER_ABS;
  
  	} while (t->task && !signal_pending(current));

  	return t->task == NULL;

  }

  long __sched hrtimer_nanosleep_restart(struct restart_block *restart)

  {

  	struct hrtimer_sleeper t;

  	struct timespec __user *rmtp;
  	struct timespec tu;

  	ktime_t time;

  
  	restart->fn = do_no_restart_syscall;

  	hrtimer_init(&t.timer, restart->arg0, HRTIMER_ABS);
  	t.timer.expires.tv64 = ((u64)restart->arg3 << 32) | (u64) restart->arg2;

  	if (do_nanosleep(&t, HRTIMER_ABS))

  		return 0;

  	rmtp = (struct timespec __user *) restart->arg1;

  	if (rmtp) {
  		time = ktime_sub(t.timer.expires, t.timer.base->get_time());
  		if (time.tv64 <= 0)
  			return 0;
  		tu = ktime_to_timespec(time);
  		if (copy_to_user(rmtp, &tu, sizeof(tu)))
  			return -EFAULT;
  	}

  	restart->fn = hrtimer_nanosleep_restart;

  
  	/* The other values in restart are already filled in */
  	return -ERESTART_RESTARTBLOCK;
  }

  long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
  		       const enum hrtimer_mode mode, const clockid_t clockid)
  {
  	struct restart_block *restart;

  	struct hrtimer_sleeper t;

  	struct timespec tu;
  	ktime_t rem;

  	hrtimer_init(&t.timer, clockid, mode);
  	t.timer.expires = timespec_to_ktime(*rqtp);
  	if (do_nanosleep(&t, mode))

  		return 0;

  	/* Absolute timers do not update the rmtp value and restart: */

  	if (mode == HRTIMER_ABS)
  		return -ERESTARTNOHAND;

  	if (rmtp) {
  		rem = ktime_sub(t.timer.expires, t.timer.base->get_time());
  		if (rem.tv64 <= 0)
  			return 0;
  		tu = ktime_to_timespec(rem);
  		if (copy_to_user(rmtp, &tu, sizeof(tu)))
  			return -EFAULT;
  	}

  
  	restart = &current_thread_info()->restart_block;

  	restart->fn = hrtimer_nanosleep_restart;
  	restart->arg0 = (unsigned long) t.timer.base->index;
  	restart->arg1 = (unsigned long) rmtp;
  	restart->arg2 = t.timer.expires.tv64 & 0xFFFFFFFF;
  	restart->arg3 = t.timer.expires.tv64 >> 32;

  
  	return -ERESTART_RESTARTBLOCK;
  }

  asmlinkage long
  sys_nanosleep(struct timespec __user *rqtp, struct timespec __user *rmtp)
  {
  	struct timespec tu;
  
  	if (copy_from_user(&tu, rqtp, sizeof(tu)))
  		return -EFAULT;
  
  	if (!timespec_valid(&tu))
  		return -EINVAL;
  
  	return hrtimer_nanosleep(&tu, rmtp, HRTIMER_REL, CLOCK_MONOTONIC);
  }

  /*

   * Functions related to boot-time initialization:
   */
  static void __devinit init_hrtimers_cpu(int cpu)
  {
  	struct hrtimer_base *base = per_cpu(hrtimer_bases, cpu);
  	int i;

  	for (i = 0; i < MAX_HRTIMER_BASES; i++, base++) {

  		spin_lock_init(&base->lock);

  		lockdep_set_class(&base->lock, &base->lock_key);
  	}

  }
  
  #ifdef CONFIG_HOTPLUG_CPU
  
  static void migrate_hrtimer_list(struct hrtimer_base *old_base,
  				struct hrtimer_base *new_base)
  {
  	struct hrtimer *timer;
  	struct rb_node *node;
  
  	while ((node = rb_first(&old_base->active))) {
  		timer = rb_entry(node, struct hrtimer, node);
  		__remove_hrtimer(timer, old_base);
  		timer->base = new_base;
  		enqueue_hrtimer(timer, new_base);
  	}
  }
  
  static void migrate_hrtimers(int cpu)
  {
  	struct hrtimer_base *old_base, *new_base;
  	int i;
  
  	BUG_ON(cpu_online(cpu));
  	old_base = per_cpu(hrtimer_bases, cpu);
  	new_base = get_cpu_var(hrtimer_bases);
  
  	local_irq_disable();
  
  	for (i = 0; i < MAX_HRTIMER_BASES; i++) {
  
  		spin_lock(&new_base->lock);
  		spin_lock(&old_base->lock);
  
  		BUG_ON(old_base->curr_timer);
  
  		migrate_hrtimer_list(old_base, new_base);
  
  		spin_unlock(&old_base->lock);
  		spin_unlock(&new_base->lock);
  		old_base++;
  		new_base++;
  	}
  
  	local_irq_enable();
  	put_cpu_var(hrtimer_bases);
  }
  #endif /* CONFIG_HOTPLUG_CPU */

  static int __cpuinit hrtimer_cpu_notify(struct notifier_block *self,

  					unsigned long action, void *hcpu)
  {
  	long cpu = (long)hcpu;
  
  	switch (action) {
  
  	case CPU_UP_PREPARE:
  		init_hrtimers_cpu(cpu);
  		break;
  
  #ifdef CONFIG_HOTPLUG_CPU
  	case CPU_DEAD:
  		migrate_hrtimers(cpu);
  		break;
  #endif
  
  	default:
  		break;
  	}
  
  	return NOTIFY_OK;
  }

  static struct notifier_block __cpuinitdata hrtimers_nb = {

  	.notifier_call = hrtimer_cpu_notify,
  };
  
  void __init hrtimers_init(void)
  {
  	hrtimer_cpu_notify(&hrtimers_nb, (unsigned long)CPU_UP_PREPARE,
  			  (void *)(long)smp_processor_id());
  	register_cpu_notifier(&hrtimers_nb);
  }