/*
   *  linux/kernel/hrtimer.c
   *

   *  Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>

   *  Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar

   *  Copyright(C) 2006-2007  Timesys Corp., Thomas Gleixner

   *
   *  High-resolution kernel timers
   *
   *  In contrast to the low-resolution timeout API implemented in
   *  kernel/timer.c, hrtimers provide finer resolution and accuracy
   *  depending on system configuration and capabilities.
   *
   *  These timers are currently used for:
   *   - itimers
   *   - POSIX timers
   *   - nanosleep
   *   - precise in-kernel timing
   *
   *  Started by: Thomas Gleixner and Ingo Molnar
   *
   *  Credits:
   *	based on kernel/timer.c
   *

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

   *  For licencing details see kernel-base/COPYING
   */
  
  #include <linux/cpu.h>

  #include <linux/irq.h>

  #include <linux/module.h>
  #include <linux/percpu.h>
  #include <linux/hrtimer.h>
  #include <linux/notifier.h>
  #include <linux/syscalls.h>

  #include <linux/kallsyms.h>

  #include <linux/interrupt.h>

  #include <linux/tick.h>

  #include <linux/seq_file.h>
  #include <linux/err.h>

  
  #include <asm/uaccess.h>
  
  /**
   * ktime_get - get the monotonic time in ktime_t format
   *
   * returns the time in ktime_t format
   */

  ktime_t ktime_get(void)

  {
  	struct timespec now;
  
  	ktime_get_ts(&now);
  
  	return timespec_to_ktime(now);
  }

  EXPORT_SYMBOL_GPL(ktime_get);

  
  /**
   * ktime_get_real - get the real (wall-) time in ktime_t format
   *
   * returns the time in ktime_t format
   */

  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_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =

  {

  
  	.clock_base =

  	{

  		{
  			.index = CLOCK_REALTIME,
  			.get_time = &ktime_get_real,

  			.resolution = KTIME_LOW_RES,

  		},
  		{
  			.index = CLOCK_MONOTONIC,
  			.get_time = &ktime_get,

  			.resolution = KTIME_LOW_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_cpu_base *base)

  {
  	ktime_t xtim, tomono;

  	struct timespec xts, tom;

  	unsigned long seq;
  
  	do {
  		seq = read_seqbegin(&xtime_lock);

  #ifdef CONFIG_NO_HZ
  		getnstimeofday(&xts);
  #else
  		xts = xtime;
  #endif

  		tom = wall_to_monotonic;

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

  	xtim = timespec_to_ktime(xts);

  	tomono = timespec_to_ktime(tom);

  	base->clock_base[CLOCK_REALTIME].softirq_time = xtim;
  	base->clock_base[CLOCK_MONOTONIC].softirq_time =
  		ktime_add(xtim, tomono);

  }
  
  /*

   * Helper function to check, whether the timer is running the callback
   * function
   */
  static inline int hrtimer_callback_running(struct hrtimer *timer)
  {
  	return timer->state & HRTIMER_STATE_CALLBACK;
  }
  
  /*

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

  /*
   * We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
   * means that all timers which are tied to this base via timer->base are
   * locked, and the base itself is locked too.
   *
   * So __run_timers/migrate_timers can safely modify all timers which could
   * be found on the lists/queues.
   *
   * When the timer's base is locked, and the timer removed from list, it is
   * possible to set timer->base = NULL and drop the lock: the timer remains
   * locked.
   */

  static
  struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
  					     unsigned long *flags)

  {

  	struct hrtimer_clock_base *base;

  
  	for (;;) {
  		base = timer->base;
  		if (likely(base != NULL)) {

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

  			if (likely(base == timer->base))
  				return base;
  			/* The timer has migrated to another CPU: */

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

  		}
  		cpu_relax();
  	}
  }
  
  /*
   * Switch the timer base to the current CPU when possible.
   */

  static inline struct hrtimer_clock_base *
  switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base)

  {

  	struct hrtimer_clock_base *new_base;
  	struct hrtimer_cpu_base *new_cpu_base;

  	new_cpu_base = &__get_cpu_var(hrtimer_bases);
  	new_base = &new_cpu_base->clock_base[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(hrtimer_callback_running(timer)))

  			return base;
  
  		/* See the comment in lock_timer_base() */
  		timer->base = NULL;

  		spin_unlock(&base->cpu_base->lock);
  		spin_lock(&new_base->cpu_base->lock);

  		timer->base = new_base;
  	}
  	return new_base;
  }
  
  #else /* CONFIG_SMP */

  static inline struct hrtimer_clock_base *

  lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
  {

  	struct hrtimer_clock_base *base = timer->base;

  	spin_lock_irqsave(&base->cpu_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);
  }

  
  EXPORT_SYMBOL_GPL(ktime_add_ns);

  # endif /* !CONFIG_KTIME_SCALAR */
  
  /*
   * Divide a ktime value by a nanosecond value
   */

  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;
  }

  #endif /* BITS_PER_LONG >= 64 */

  /* High resolution timer related functions */
  #ifdef CONFIG_HIGH_RES_TIMERS
  
  /*
   * High resolution timer enabled ?
   */
  static int hrtimer_hres_enabled __read_mostly  = 1;
  
  /*
   * Enable / Disable high resolution mode
   */
  static int __init setup_hrtimer_hres(char *str)
  {
  	if (!strcmp(str, "off"))
  		hrtimer_hres_enabled = 0;
  	else if (!strcmp(str, "on"))
  		hrtimer_hres_enabled = 1;
  	else
  		return 0;
  	return 1;
  }
  
  __setup("highres=", setup_hrtimer_hres);
  
  /*
   * hrtimer_high_res_enabled - query, if the highres mode is enabled
   */
  static inline int hrtimer_is_hres_enabled(void)
  {
  	return hrtimer_hres_enabled;
  }
  
  /*
   * Is the high resolution mode active ?
   */
  static inline int hrtimer_hres_active(void)
  {
  	return __get_cpu_var(hrtimer_bases).hres_active;
  }
  
  /*
   * Reprogram the event source with checking both queues for the
   * next event
   * Called with interrupts disabled and base->lock held
   */
  static void hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base)
  {
  	int i;
  	struct hrtimer_clock_base *base = cpu_base->clock_base;
  	ktime_t expires;
  
  	cpu_base->expires_next.tv64 = KTIME_MAX;
  
  	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++, base++) {
  		struct hrtimer *timer;
  
  		if (!base->first)
  			continue;
  		timer = rb_entry(base->first, struct hrtimer, node);
  		expires = ktime_sub(timer->expires, base->offset);
  		if (expires.tv64 < cpu_base->expires_next.tv64)
  			cpu_base->expires_next = expires;
  	}
  
  	if (cpu_base->expires_next.tv64 != KTIME_MAX)
  		tick_program_event(cpu_base->expires_next, 1);
  }
  
  /*
   * Shared reprogramming for clock_realtime and clock_monotonic
   *
   * When a timer is enqueued and expires earlier than the already enqueued
   * timers, we have to check, whether it expires earlier than the timer for
   * which the clock event device was armed.
   *
   * Called with interrupts disabled and base->cpu_base.lock held
   */
  static int hrtimer_reprogram(struct hrtimer *timer,
  			     struct hrtimer_clock_base *base)
  {
  	ktime_t *expires_next = &__get_cpu_var(hrtimer_bases).expires_next;
  	ktime_t expires = ktime_sub(timer->expires, base->offset);
  	int res;
  
  	/*
  	 * When the callback is running, we do not reprogram the clock event
  	 * device. The timer callback is either running on a different CPU or
  	 * the callback is executed in the hrtimer_interupt context. The
  	 * reprogramming is handled either by the softirq, which called the
  	 * callback or at the end of the hrtimer_interrupt.
  	 */
  	if (hrtimer_callback_running(timer))
  		return 0;
  
  	if (expires.tv64 >= expires_next->tv64)
  		return 0;
  
  	/*
  	 * Clockevents returns -ETIME, when the event was in the past.
  	 */
  	res = tick_program_event(expires, 0);
  	if (!IS_ERR_VALUE(res))
  		*expires_next = expires;
  	return res;
  }
  
  
  /*
   * Retrigger next event is called after clock was set
   *
   * Called with interrupts disabled via on_each_cpu()
   */
  static void retrigger_next_event(void *arg)
  {
  	struct hrtimer_cpu_base *base;
  	struct timespec realtime_offset;
  	unsigned long seq;
  
  	if (!hrtimer_hres_active())
  		return;
  
  	do {
  		seq = read_seqbegin(&xtime_lock);
  		set_normalized_timespec(&realtime_offset,
  					-wall_to_monotonic.tv_sec,
  					-wall_to_monotonic.tv_nsec);
  	} while (read_seqretry(&xtime_lock, seq));
  
  	base = &__get_cpu_var(hrtimer_bases);
  
  	/* Adjust CLOCK_REALTIME offset */
  	spin_lock(&base->lock);
  	base->clock_base[CLOCK_REALTIME].offset =
  		timespec_to_ktime(realtime_offset);
  
  	hrtimer_force_reprogram(base);
  	spin_unlock(&base->lock);
  }
  
  /*
   * Clock realtime was set
   *
   * Change the offset of the realtime clock vs. the monotonic
   * clock.
   *
   * We might have to reprogram the high resolution timer interrupt. On
   * SMP we call the architecture specific code to retrigger _all_ high
   * resolution timer interrupts. On UP we just disable interrupts and
   * call the high resolution interrupt code.
   */
  void clock_was_set(void)
  {
  	/* Retrigger the CPU local events everywhere */
  	on_each_cpu(retrigger_next_event, NULL, 0, 1);
  }
  
  /*

   * During resume we might have to reprogram the high resolution timer
   * interrupt (on the local CPU):
   */
  void hres_timers_resume(void)
  {
  	WARN_ON_ONCE(num_online_cpus() > 1);
  
  	/* Retrigger the CPU local events: */
  	retrigger_next_event(NULL);
  }
  
  /*

   * Check, whether the timer is on the callback pending list
   */
  static inline int hrtimer_cb_pending(const struct hrtimer *timer)
  {
  	return timer->state & HRTIMER_STATE_PENDING;
  }
  
  /*
   * Remove a timer from the callback pending list
   */
  static inline void hrtimer_remove_cb_pending(struct hrtimer *timer)
  {
  	list_del_init(&timer->cb_entry);
  }
  
  /*
   * Initialize the high resolution related parts of cpu_base
   */
  static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base)
  {
  	base->expires_next.tv64 = KTIME_MAX;
  	base->hres_active = 0;
  	INIT_LIST_HEAD(&base->cb_pending);
  }
  
  /*
   * Initialize the high resolution related parts of a hrtimer
   */
  static inline void hrtimer_init_timer_hres(struct hrtimer *timer)
  {
  	INIT_LIST_HEAD(&timer->cb_entry);
  }
  
  /*
   * When High resolution timers are active, try to reprogram. Note, that in case
   * the state has HRTIMER_STATE_CALLBACK set, no reprogramming and no expiry
   * check happens. The timer gets enqueued into the rbtree. The reprogramming
   * and expiry check is done in the hrtimer_interrupt or in the softirq.
   */
  static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
  					    struct hrtimer_clock_base *base)
  {
  	if (base->cpu_base->hres_active && hrtimer_reprogram(timer, base)) {
  
  		/* Timer is expired, act upon the callback mode */
  		switch(timer->cb_mode) {
  		case HRTIMER_CB_IRQSAFE_NO_RESTART:
  			/*
  			 * We can call the callback from here. No restart
  			 * happens, so no danger of recursion
  			 */
  			BUG_ON(timer->function(timer) != HRTIMER_NORESTART);
  			return 1;
  		case HRTIMER_CB_IRQSAFE_NO_SOFTIRQ:
  			/*
  			 * This is solely for the sched tick emulation with
  			 * dynamic tick support to ensure that we do not
  			 * restart the tick right on the edge and end up with
  			 * the tick timer in the softirq ! The calling site
  			 * takes care of this.
  			 */
  			return 1;
  		case HRTIMER_CB_IRQSAFE:
  		case HRTIMER_CB_SOFTIRQ:
  			/*
  			 * Move everything else into the softirq pending list !
  			 */
  			list_add_tail(&timer->cb_entry,
  				      &base->cpu_base->cb_pending);
  			timer->state = HRTIMER_STATE_PENDING;
  			raise_softirq(HRTIMER_SOFTIRQ);
  			return 1;
  		default:
  			BUG();
  		}
  	}
  	return 0;
  }
  
  /*
   * Switch to high resolution mode
   */

  static int hrtimer_switch_to_hres(void)

  {
  	struct hrtimer_cpu_base *base = &__get_cpu_var(hrtimer_bases);
  	unsigned long flags;
  
  	if (base->hres_active)

  		return 1;

  
  	local_irq_save(flags);
  
  	if (tick_init_highres()) {
  		local_irq_restore(flags);

  		return 0;

  	}
  	base->hres_active = 1;
  	base->clock_base[CLOCK_REALTIME].resolution = KTIME_HIGH_RES;
  	base->clock_base[CLOCK_MONOTONIC].resolution = KTIME_HIGH_RES;
  
  	tick_setup_sched_timer();
  
  	/* "Retrigger" the interrupt to get things going */
  	retrigger_next_event(NULL);
  	local_irq_restore(flags);
  	printk(KERN_INFO "Switched to high resolution mode on CPU %d
  ",
  	       smp_processor_id());

  	return 1;

  }
  
  #else
  
  static inline int hrtimer_hres_active(void) { return 0; }
  static inline int hrtimer_is_hres_enabled(void) { return 0; }

  static inline int hrtimer_switch_to_hres(void) { return 0; }

  static inline void hrtimer_force_reprogram(struct hrtimer_cpu_base *base) { }
  static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
  					    struct hrtimer_clock_base *base)
  {
  	return 0;
  }
  static inline int hrtimer_cb_pending(struct hrtimer *timer) { return 0; }
  static inline void hrtimer_remove_cb_pending(struct hrtimer *timer) { }
  static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base) { }
  static inline void hrtimer_init_timer_hres(struct hrtimer *timer) { }
  
  #endif /* CONFIG_HIGH_RES_TIMERS */

  #ifdef CONFIG_TIMER_STATS
  void __timer_stats_hrtimer_set_start_info(struct hrtimer *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;
  }
  #endif

  /*
   * Counterpart to lock_timer_base above:
   */
  static inline
  void unlock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
  {

  	spin_unlock_irqrestore(&timer->base->cpu_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);

  	/*
  	 * Make sure, that the result did not wrap with a very large
  	 * interval.
  	 */
  	if (timer->expires.tv64 < 0)
  		timer->expires = ktime_set(KTIME_SEC_MAX, 0);

  
  	return orun;
  }

  EXPORT_SYMBOL_GPL(hrtimer_forward);

  
  /*
   * enqueue_hrtimer - internal function to (re)start a timer
   *
   * The timer is inserted in expiry order. Insertion into the
   * red black tree is O(log(n)). Must hold the base lock.
   */

  static void enqueue_hrtimer(struct hrtimer *timer,

  			    struct hrtimer_clock_base *base, int reprogram)

  {
  	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

  	 */

  	if (!base->first || timer->expires.tv64 <
  	    rb_entry(base->first, struct hrtimer, node)->expires.tv64) {
  		/*
  		 * Reprogram the clock event device. When the timer is already
  		 * expired hrtimer_enqueue_reprogram has either called the
  		 * callback or added it to the pending list and raised the
  		 * softirq.
  		 *
  		 * This is a NOP for !HIGHRES
  		 */
  		if (reprogram && hrtimer_enqueue_reprogram(timer, base))
  			return;
  
  		base->first = &timer->node;
  	}

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

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

  }

  
  /*
   * __remove_hrtimer - internal function to remove a timer
   *
   * Caller must hold the base lock.

   *
   * High resolution timer mode reprograms the clock event device when the
   * timer is the one which expires next. The caller can disable this by setting
   * reprogram to zero. This is useful, when the context does a reprogramming
   * anyway (e.g. timer interrupt)

   */

  static void __remove_hrtimer(struct hrtimer *timer,

  			     struct hrtimer_clock_base *base,

  			     unsigned long newstate, int reprogram)

  {

  	/* High res. callback list. NOP for !HIGHRES */
  	if (hrtimer_cb_pending(timer))
  		hrtimer_remove_cb_pending(timer);
  	else {
  		/*
  		 * 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);
  			/* Reprogram the clock event device. if enabled */
  			if (reprogram && hrtimer_hres_active())
  				hrtimer_force_reprogram(base->cpu_base);
  		}
  		rb_erase(&timer->node, &base->active);
  	}

  	timer->state = newstate;

  }
  
  /*
   * remove hrtimer, called with base lock held
   */
  static inline int

  remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)

  {

  	if (hrtimer_is_queued(timer)) {

  		int reprogram;
  
  		/*
  		 * Remove the timer and force reprogramming when high
  		 * resolution mode is active and the timer is on the current
  		 * CPU. If we remove a timer on another CPU, reprogramming is
  		 * skipped. The interrupt event on this CPU is fired and
  		 * reprogramming happens in the interrupt handler. This is a
  		 * rare case and less expensive than a smp call.
  		 */

  		timer_stats_hrtimer_clear_start_info(timer);

  		reprogram = base->cpu_base == &__get_cpu_var(hrtimer_bases);
  		__remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE,
  				 reprogram);

  		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_clock_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_MODE_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;

  	timer_stats_hrtimer_set_start_info(timer);

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

  
  	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_clock_base *base;

  	unsigned long flags;
  	int ret = -1;
  
  	base = lock_hrtimer_base(timer, &flags);

  	if (!hrtimer_callback_running(timer))

  		ret = remove_hrtimer(timer, base);
  
  	unlock_hrtimer_base(timer, &flags);
  
  	return ret;
  
  }

  EXPORT_SYMBOL_GPL(hrtimer_try_to_cancel);

  
  /**
   * 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_clock_base *base;

  	unsigned long flags;
  	ktime_t rem;
  
  	base = lock_hrtimer_base(timer, &flags);

  	rem = ktime_sub(timer->expires, base->get_time());

  	unlock_hrtimer_base(timer, &flags);
  
  	return rem;
  }

  EXPORT_SYMBOL_GPL(hrtimer_get_remaining);

  #if defined(CONFIG_NO_IDLE_HZ) || defined(CONFIG_NO_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_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
  	struct hrtimer_clock_base *base = cpu_base->clock_base;

  	ktime_t delta, mindelta = { .tv64 = KTIME_MAX };
  	unsigned long flags;
  	int i;

  	spin_lock_irqsave(&cpu_base->lock, flags);

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

  			if (!base->first)
  				continue;

  			timer = rb_entry(base->first, struct hrtimer, node);
  			delta.tv64 = timer->expires.tv64;
  			delta = ktime_sub(delta, base->get_time());
  			if (delta.tv64 < mindelta.tv64)
  				mindelta.tv64 = delta.tv64;
  		}

  	}

  
  	spin_unlock_irqrestore(&cpu_base->lock, flags);

  	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_cpu_base *cpu_base;

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

  	cpu_base = &__raw_get_cpu_var(hrtimer_bases);

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

  		clock_id = CLOCK_MONOTONIC;

  	timer->base = &cpu_base->clock_base[clock_id];

  	hrtimer_init_timer_hres(timer);

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

  }

  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_cpu_base *cpu_base;

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

  
  	return 0;
  }

  EXPORT_SYMBOL_GPL(hrtimer_get_res);

  #ifdef CONFIG_HIGH_RES_TIMERS
  
  /*
   * High resolution timer interrupt
   * Called with interrupts disabled
   */
  void hrtimer_interrupt(struct clock_event_device *dev)
  {
  	struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
  	struct hrtimer_clock_base *base;
  	ktime_t expires_next, now;
  	int i, raise = 0;
  
  	BUG_ON(!cpu_base->hres_active);
  	cpu_base->nr_events++;
  	dev->next_event.tv64 = KTIME_MAX;
  
   retry:
  	now = ktime_get();
  
  	expires_next.tv64 = KTIME_MAX;
  
  	base = cpu_base->clock_base;
  
  	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
  		ktime_t basenow;
  		struct rb_node *node;
  
  		spin_lock(&cpu_base->lock);
  
  		basenow = ktime_add(now, base->offset);
  
  		while ((node = base->first)) {
  			struct hrtimer *timer;
  
  			timer = rb_entry(node, struct hrtimer, node);
  
  			if (basenow.tv64 < timer->expires.tv64) {
  				ktime_t expires;
  
  				expires = ktime_sub(timer->expires,
  						    base->offset);
  				if (expires.tv64 < expires_next.tv64)
  					expires_next = expires;
  				break;
  			}
  
  			/* Move softirq callbacks to the pending list */
  			if (timer->cb_mode == HRTIMER_CB_SOFTIRQ) {
  				__remove_hrtimer(timer, base,
  						 HRTIMER_STATE_PENDING, 0);
  				list_add_tail(&timer->cb_entry,
  					      &base->cpu_base->cb_pending);
  				raise = 1;
  				continue;
  			}
  
  			__remove_hrtimer(timer, base,
  					 HRTIMER_STATE_CALLBACK, 0);

  			timer_stats_account_hrtimer(timer);

  
  			/*
  			 * Note: We clear the CALLBACK bit after
  			 * enqueue_hrtimer to avoid reprogramming of
  			 * the event hardware. This happens at the end
  			 * of this function anyway.
  			 */
  			if (timer->function(timer) != HRTIMER_NORESTART) {
  				BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
  				enqueue_hrtimer(timer, base, 0);
  			}
  			timer->state &= ~HRTIMER_STATE_CALLBACK;
  		}
  		spin_unlock(&cpu_base->lock);
  		base++;
  	}
  
  	cpu_base->expires_next = expires_next;
  
  	/* Reprogramming necessary ? */
  	if (expires_next.tv64 != KTIME_MAX) {
  		if (tick_program_event(expires_next, 0))
  			goto retry;
  	}
  
  	/* Raise softirq ? */
  	if (raise)
  		raise_softirq(HRTIMER_SOFTIRQ);
  }
  
  static void run_hrtimer_softirq(struct softirq_action *h)
  {
  	struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
  
  	spin_lock_irq(&cpu_base->lock);
  
  	while (!list_empty(&cpu_base->cb_pending)) {
  		enum hrtimer_restart (*fn)(struct hrtimer *);
  		struct hrtimer *timer;
  		int restart;
  
  		timer = list_entry(cpu_base->cb_pending.next,
  				   struct hrtimer, cb_entry);

  		timer_stats_account_hrtimer(timer);

  		fn = timer->function;
  		__remove_hrtimer(timer, timer->base, HRTIMER_STATE_CALLBACK, 0);
  		spin_unlock_irq(&cpu_base->lock);
  
  		restart = fn(timer);
  
  		spin_lock_irq(&cpu_base->lock);
  
  		timer->state &= ~HRTIMER_STATE_CALLBACK;
  		if (restart == HRTIMER_RESTART) {
  			BUG_ON(hrtimer_active(timer));
  			/*
  			 * Enqueue the timer, allow reprogramming of the event
  			 * device
  			 */
  			enqueue_hrtimer(timer, timer->base, 1);
  		} else if (hrtimer_active(timer)) {
  			/*
  			 * If the timer was rearmed on another CPU, reprogram
  			 * the event device.
  			 */
  			if (timer->base->first == &timer->node)
  				hrtimer_reprogram(timer, timer->base);
  		}
  	}
  	spin_unlock_irq(&cpu_base->lock);
  }
  
  #endif	/* CONFIG_HIGH_RES_TIMERS */

  /*
   * Expire the per base hrtimer-queue:
   */

  static inline void run_hrtimer_queue(struct hrtimer_cpu_base *cpu_base,
  				     int index)

  {

  	struct rb_node *node;

  	struct hrtimer_clock_base *base = &cpu_base->clock_base[index];

  	if (!base->first)
  		return;

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

  	spin_lock_irq(&cpu_base->lock);

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

  		struct hrtimer *timer;

  		enum hrtimer_restart (*fn)(struct hrtimer *);

  		int restart;

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

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

  			break;

  #ifdef CONFIG_HIGH_RES_TIMERS
  		WARN_ON_ONCE(timer->cb_mode == HRTIMER_CB_IRQSAFE_NO_SOFTIRQ);
  #endif

  		timer_stats_account_hrtimer(timer);

  		fn = timer->function;

  		__remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);

  		spin_unlock_irq(&cpu_base->lock);

  		restart = fn(timer);

  		spin_lock_irq(&cpu_base->lock);

  		timer->state &= ~HRTIMER_STATE_CALLBACK;

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

  			enqueue_hrtimer(timer, base, 0);

  		}

  	}

  	spin_unlock_irq(&cpu_base->lock);

  }
  
  /*
   * Called from timer softirq every jiffy, expire hrtimers:

   *
   * For HRT its the fall back code to run the softirq in the timer
   * softirq context in case the hrtimer initialization failed or has
   * not been done yet.

   */
  void hrtimer_run_queues(void)
  {

  	struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);

  	int i;

  	if (hrtimer_hres_active())
  		return;

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

  	if (tick_check_oneshot_change(!hrtimer_is_hres_enabled()))

  		if (hrtimer_switch_to_hres())
  			return;

  	hrtimer_get_softirq_time(cpu_base);

  	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)
  		run_hrtimer_queue(cpu_base, i);

  }
  
  /*

   * Sleep related functions:
   */

  static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer)

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

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

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

  #ifdef CONFIG_HIGH_RES_TIMERS
  	sl->timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_RESTART;
  #endif

  }

  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);

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

  		hrtimer_cancel(&t->timer);

  		mode = HRTIMER_MODE_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_MODE_ABS);

  	t.timer.expires.tv64 = ((u64)restart->arg3 << 32) | (u64) restart->arg2;

  	if (do_nanosleep(&t, HRTIMER_MODE_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_MODE_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_MODE_REL, CLOCK_MONOTONIC);

  }

  /*

   * Functions related to boot-time initialization:
   */
  static void __devinit init_hrtimers_cpu(int cpu)
  {

  	struct hrtimer_cpu_base *cpu_base = &per_cpu(hrtimer_bases, cpu);

  	int i;

  	spin_lock_init(&cpu_base->lock);
  	lockdep_set_class(&cpu_base->lock, &cpu_base->lock_key);
  
  	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)
  		cpu_base->clock_base[i].cpu_base = cpu_base;

  	hrtimer_init_hres(cpu_base);

  }
  
  #ifdef CONFIG_HOTPLUG_CPU

  static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
  				struct hrtimer_clock_base *new_base)

  {
  	struct hrtimer *timer;
  	struct rb_node *node;
  
  	while ((node = rb_first(&old_base->active))) {
  		timer = rb_entry(node, struct hrtimer, node);

  		BUG_ON(hrtimer_callback_running(timer));
  		__remove_hrtimer(timer, old_base, HRTIMER_STATE_INACTIVE, 0);

  		timer->base = new_base;

  		/*
  		 * Enqueue the timer. Allow reprogramming of the event device
  		 */
  		enqueue_hrtimer(timer, new_base, 1);

  	}
  }
  
  static void migrate_hrtimers(int cpu)
  {

  	struct hrtimer_cpu_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);

  	tick_cancel_sched_timer(cpu);

  	local_irq_disable();

  	double_spin_lock(&new_base->lock, &old_base->lock,
  			 smp_processor_id() < cpu);

  	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {

  		migrate_hrtimer_list(&old_base->clock_base[i],
  				     &new_base->clock_base[i]);

  	}

  	double_spin_unlock(&new_base->lock, &old_base->lock,
  			   smp_processor_id() < cpu);

  	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)
  {

  	unsigned int cpu = (long)hcpu;

  
  	switch (action) {
  
  	case CPU_UP_PREPARE:

  	case CPU_UP_PREPARE_FROZEN:

  		init_hrtimers_cpu(cpu);
  		break;
  
  #ifdef CONFIG_HOTPLUG_CPU
  	case CPU_DEAD:

  	case CPU_DEAD_FROZEN:

  		clockevents_notify(CLOCK_EVT_NOTIFY_CPU_DEAD, &cpu);

  		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);

  #ifdef CONFIG_HIGH_RES_TIMERS
  	open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq, NULL);
  #endif

  }