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26 results

hrtimer.c

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  • hrtimer.c 40.18 KiB
    /*
     *  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 <linux/debugobjects.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);
    		xts = current_kernel_time();
    		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);
    
    /**
     * ktime_sub_ns - Subtract a scalar nanoseconds value from a ktime_t variable
     * @kt:		minuend
     * @nsec:	the scalar nsec value to subtract
     *
     * Returns the subtraction of @nsec from @kt in ktime_t format
     */
    ktime_t ktime_sub_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_sub(kt, tmp);
    }
    
    EXPORT_SYMBOL_GPL(ktime_sub_ns);
    # endif /* !CONFIG_KTIME_SCALAR */
    
    /*
     * Divide a ktime value by a nanosecond value
     */
    u64 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 dclc;
    }
    #endif /* BITS_PER_LONG >= 64 */
    
    /*
     * Add two ktime values and do a safety check for overflow:
     */
    ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs)
    {
    	ktime_t res = ktime_add(lhs, rhs);
    
    	/*
    	 * We use KTIME_SEC_MAX here, the maximum timeout which we can
    	 * return to user space in a timespec:
    	 */
    	if (res.tv64 < 0 || res.tv64 < lhs.tv64 || res.tv64 < rhs.tv64)
    		res = ktime_set(KTIME_SEC_MAX, 0);
    
    	return res;
    }
    
    #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
    
    static struct debug_obj_descr hrtimer_debug_descr;
    
    /*
     * fixup_init is called when:
     * - an active object is initialized
     */
    static int hrtimer_fixup_init(void *addr, enum debug_obj_state state)
    {
    	struct hrtimer *timer = addr;
    
    	switch (state) {
    	case ODEBUG_STATE_ACTIVE:
    		hrtimer_cancel(timer);
    		debug_object_init(timer, &hrtimer_debug_descr);
    		return 1;
    	default:
    		return 0;
    	}
    }
    
    /*
     * fixup_activate is called when:
     * - an active object is activated
     * - an unknown object is activated (might be a statically initialized object)
     */
    static int hrtimer_fixup_activate(void *addr, enum debug_obj_state state)
    {
    	switch (state) {
    
    	case ODEBUG_STATE_NOTAVAILABLE:
    		WARN_ON_ONCE(1);
    		return 0;
    
    	case ODEBUG_STATE_ACTIVE:
    		WARN_ON(1);
    
    	default:
    		return 0;
    	}
    }
    
    /*
     * fixup_free is called when:
     * - an active object is freed
     */
    static int hrtimer_fixup_free(void *addr, enum debug_obj_state state)
    {
    	struct hrtimer *timer = addr;
    
    	switch (state) {
    	case ODEBUG_STATE_ACTIVE:
    		hrtimer_cancel(timer);
    		debug_object_free(timer, &hrtimer_debug_descr);
    		return 1;
    	default:
    		return 0;
    	}
    }
    
    static struct debug_obj_descr hrtimer_debug_descr = {
    	.name		= "hrtimer",
    	.fixup_init	= hrtimer_fixup_init,
    	.fixup_activate	= hrtimer_fixup_activate,
    	.fixup_free	= hrtimer_fixup_free,
    };
    
    static inline void debug_hrtimer_init(struct hrtimer *timer)
    {
    	debug_object_init(timer, &hrtimer_debug_descr);
    }
    
    static inline void debug_hrtimer_activate(struct hrtimer *timer)
    {
    	debug_object_activate(timer, &hrtimer_debug_descr);
    }
    
    static inline void debug_hrtimer_deactivate(struct hrtimer *timer)
    {
    	debug_object_deactivate(timer, &hrtimer_debug_descr);
    }
    
    static inline void debug_hrtimer_free(struct hrtimer *timer)
    {
    	debug_object_free(timer, &hrtimer_debug_descr);
    }
    
    static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
    			   enum hrtimer_mode mode);
    
    void hrtimer_init_on_stack(struct hrtimer *timer, clockid_t clock_id,
    			   enum hrtimer_mode mode)
    {
    	debug_object_init_on_stack(timer, &hrtimer_debug_descr);
    	__hrtimer_init(timer, clock_id, mode);
    }
    
    void destroy_hrtimer_on_stack(struct hrtimer *timer)
    {
    	debug_object_free(timer, &hrtimer_debug_descr);
    }
    
    #else
    static inline void debug_hrtimer_init(struct hrtimer *timer) { }
    static inline void debug_hrtimer_activate(struct hrtimer *timer) { }
    static inline void debug_hrtimer_deactivate(struct hrtimer *timer) { }
    #endif
    
    /*
     * 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);
    }
    
    /* 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;
    
    	WARN_ON_ONCE(timer->expires.tv64 < 0);
    
    	/*
    	 * 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_interrupt 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;
    
    	/*
    	 * CLOCK_REALTIME timer might be requested with an absolute
    	 * expiry time which is less than base->offset. Nothing wrong
    	 * about that, just avoid to call into the tick code, which
    	 * has now objections against negative expiry values.
    	 */
    	if (expires.tv64 < 0)
    		return -ETIME;
    
    	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);
    }
    
    /*
     * 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;
    }
    
    /*
     * Initialize the high resolution related parts of a hrtimer
     */
    static inline void hrtimer_init_timer_hres(struct hrtimer *timer)
    {
    }
    
    /*
     * 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:
    			debug_hrtimer_deactivate(timer);
    			/*
    			 * 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.
    			 */
    			debug_hrtimer_deactivate(timer);
    			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;
    			return 1;
    		default:
    			BUG();
    		}
    	}
    	return 0;
    }
    
    /*
     * Switch to high resolution mode
     */
    static int hrtimer_switch_to_hres(void)
    {
    	int cpu = smp_processor_id();
    	struct hrtimer_cpu_base *base = &per_cpu(hrtimer_bases, cpu);
    	unsigned long flags;
    
    	if (base->hres_active)
    		return 1;
    
    	local_irq_save(flags);
    
    	if (tick_init_highres()) {
    		local_irq_restore(flags);
    		printk(KERN_WARNING "Could not switch to high resolution "
    				    "mode on CPU %d\n", cpu);
    		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_DEBUG "Switched to high resolution mode on CPU %d\n",
    	       smp_processor_id());
    	return 1;
    }
    
    static inline void hrtimer_raise_softirq(void)
    {
    	raise_softirq(HRTIMER_SOFTIRQ);
    }
    
    #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 void hrtimer_init_hres(struct hrtimer_cpu_base *base) { }
    static inline void hrtimer_init_timer_hres(struct hrtimer *timer) { }
    static inline int hrtimer_reprogram(struct hrtimer *timer,
    				    struct hrtimer_clock_base *base)
    {
    	return 0;
    }
    static inline void hrtimer_raise_softirq(void) { }
    
    #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_hrtimer_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.
     */
    u64 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval)
    {
    	u64 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_safe(timer->expires, interval);
    
    	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;
    	int leftmost = 1;
    
    	debug_hrtimer_activate(timer);
    
    	/*
    	 * 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;
    			leftmost = 0;
    		}
    	}
    
    	/*
    	 * Insert the timer to the rbtree and check whether it
    	 * replaces the first pending timer
    	 */
    	if (leftmost) {
    		/*
    		 * 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.
    		 */
    		debug_hrtimer_deactivate(timer);
    		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, raise;
    
    	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_safe(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_safe(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));
    
    	/*
    	 * The timer may be expired and moved to the cb_pending
    	 * list. We can not raise the softirq with base lock held due
    	 * to a possible deadlock with runqueue lock.
    	 */
    	raise = timer->state == HRTIMER_STATE_PENDING;
    
    	unlock_hrtimer_base(timer, &flags);
    
    	if (raise)
    		hrtimer_raise_softirq();
    
    	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
    
    static 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];
    	INIT_LIST_HEAD(&timer->cb_entry);
    	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
    }
    
    /**
     * 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)
    {
    	debug_hrtimer_init(timer);
    	__hrtimer_init(timer, clock_id, mode);
    }
    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);
    
    static void run_hrtimer_pending(struct hrtimer_cpu_base *cpu_base)
    {
    	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);
    
    		debug_hrtimer_deactivate(timer);
    		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.
    			 */
    			struct hrtimer_clock_base *base = timer->base;
    
    			if (base->first == &timer->node &&
    			    hrtimer_reprogram(timer, base)) {
    				/*
    				 * Timer is expired. Thus move it from tree to
    				 * pending list again.
    				 */
    				__remove_hrtimer(timer, base,
    						 HRTIMER_STATE_PENDING, 0);
    				list_add_tail(&timer->cb_entry,
    					      &base->cpu_base->cb_pending);
    			}
    		}
    	}
    	spin_unlock_irq(&cpu_base->lock);
    }
    
    static void __run_hrtimer(struct hrtimer *timer)
    {
    	struct hrtimer_clock_base *base = timer->base;
    	struct hrtimer_cpu_base *cpu_base = base->cpu_base;
    	enum hrtimer_restart (*fn)(struct hrtimer *);
    	int restart;
    
    	debug_hrtimer_deactivate(timer);
    	__remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
    	timer_stats_account_hrtimer(timer);
    
    	fn = timer->function;
    	if (timer->cb_mode == HRTIMER_CB_IRQSAFE_NO_SOFTIRQ) {
    		/*
    		 * Used for scheduler timers, avoid lock inversion with
    		 * rq->lock and tasklist_lock.
    		 *
    		 * These timers are required to deal with enqueue expiry
    		 * themselves and are not allowed to migrate.
    		 */
    		spin_unlock(&cpu_base->lock);
    		restart = fn(timer);
    		spin_lock(&cpu_base->lock);
    	} else
    		restart = fn(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 (restart != HRTIMER_NORESTART) {
    		BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
    		enqueue_hrtimer(timer, base, 0);
    	}
    	timer->state &= ~HRTIMER_STATE_CALLBACK;
    }
    
    #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;
    			}
    
    			__run_hrtimer(timer);
    		}
    		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)
    {
    	run_hrtimer_pending(&__get_cpu_var(hrtimer_bases));
    }
    
    #endif	/* CONFIG_HIGH_RES_TIMERS */
    
    /*
     * 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_pending(void)
    {
    	struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
    
    	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()))
    		hrtimer_switch_to_hres();
    
    	run_hrtimer_pending(cpu_base);
    }
    
    /*
     * Called from hardirq context every jiffy
     */
    void hrtimer_run_queues(void)
    {
    	struct rb_node *node;
    	struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
    	struct hrtimer_clock_base *base;
    	int index, gettime = 1;
    
    	if (hrtimer_hres_active())
    		return;
    
    	for (index = 0; index < HRTIMER_MAX_CLOCK_BASES; index++) {
    		base = &cpu_base->clock_base[index];
    
    		if (!base->first)
    			continue;
    
    		if (base->get_softirq_time)
    			base->softirq_time = base->get_softirq_time();
    		else if (gettime) {
    			hrtimer_get_softirq_time(cpu_base);
    			gettime = 0;
    		}
    
    		spin_lock(&cpu_base->lock);
    
    		while ((node = base->first)) {
    			struct hrtimer *timer;
    
    			timer = rb_entry(node, struct hrtimer, node);
    			if (base->softirq_time.tv64 <= timer->expires.tv64)
    				break;
    
    			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);
    				continue;
    			}
    
    			__run_hrtimer(timer);
    		}
    		spin_unlock(&cpu_base->lock);
    	}
    }
    
    /*
     * 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_SOFTIRQ;
    #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 (!hrtimer_active(&t->timer))
    			t->task = NULL;
    
    		if (likely(t->task))
    			schedule();
    
    		hrtimer_cancel(&t->timer);
    		mode = HRTIMER_MODE_ABS;
    
    	} while (t->task && !signal_pending(current));
    
    	__set_current_state(TASK_RUNNING);
    
    	return t->task == NULL;
    }
    
    static int update_rmtp(struct hrtimer *timer, struct timespec __user *rmtp)
    {
    	struct timespec rmt;
    	ktime_t rem;
    
    	rem = ktime_sub(timer->expires, timer->base->get_time());
    	if (rem.tv64 <= 0)
    		return 0;
    	rmt = ktime_to_timespec(rem);
    
    	if (copy_to_user(rmtp, &rmt, sizeof(*rmtp)))
    		return -EFAULT;
    
    	return 1;
    }
    
    long __sched hrtimer_nanosleep_restart(struct restart_block *restart)
    {
    	struct hrtimer_sleeper t;
    	struct timespec __user  *rmtp;
    	int ret = 0;
    
    	hrtimer_init_on_stack(&t.timer, restart->nanosleep.index,
    				HRTIMER_MODE_ABS);
    	t.timer.expires.tv64 = restart->nanosleep.expires;
    
    	if (do_nanosleep(&t, HRTIMER_MODE_ABS))
    		goto out;
    
    	rmtp = restart->nanosleep.rmtp;
    	if (rmtp) {
    		ret = update_rmtp(&t.timer, rmtp);
    		if (ret <= 0)
    			goto out;
    	}
    
    	/* The other values in restart are already filled in */
    	ret = -ERESTART_RESTARTBLOCK;
    out:
    	destroy_hrtimer_on_stack(&t.timer);
    	return ret;
    }
    
    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;
    	int ret = 0;
    
    	hrtimer_init_on_stack(&t.timer, clockid, mode);
    	t.timer.expires = timespec_to_ktime(*rqtp);
    	if (do_nanosleep(&t, mode))
    		goto out;
    
    	/* Absolute timers do not update the rmtp value and restart: */
    	if (mode == HRTIMER_MODE_ABS) {
    		ret = -ERESTARTNOHAND;
    		goto out;
    	}
    
    	if (rmtp) {
    		ret = update_rmtp(&t.timer, rmtp);
    		if (ret <= 0)
    			goto out;
    	}
    
    	restart = &current_thread_info()->restart_block;
    	restart->fn = hrtimer_nanosleep_restart;
    	restart->nanosleep.index = t.timer.base->index;
    	restart->nanosleep.rmtp = rmtp;
    	restart->nanosleep.expires = t.timer.expires.tv64;
    
    	ret = -ERESTART_RESTARTBLOCK;
    out:
    	destroy_hrtimer_on_stack(&t.timer);
    	return ret;
    }
    
    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 __cpuinit init_hrtimers_cpu(int cpu)
    {
    	struct hrtimer_cpu_base *cpu_base = &per_cpu(hrtimer_bases, cpu);
    	int i;
    
    	spin_lock_init(&cpu_base->lock);
    
    	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)
    		cpu_base->clock_base[i].cpu_base = cpu_base;
    
    	INIT_LIST_HEAD(&cpu_base->cb_pending);
    	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));
    		debug_hrtimer_deactivate(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();
    	spin_lock(&new_base->lock);
    	spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
    
    	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
    		migrate_hrtimer_list(&old_base->clock_base[i],
    				     &new_base->clock_base[i]);
    	}
    
    	spin_unlock(&old_base->lock);
    	spin_unlock(&new_base->lock);
    	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
    }