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Commit fb63a0eb authored by Martin Schwidefsky's avatar Martin Schwidefsky Committed by Thomas Gleixner
Browse files

clocksource: Refactor clocksource watchdog 



Refactor clocksource watchdog code to make it more readable. Add
clocksource_dequeue_watchdog to remove a clocksource from the watchdog
list when it is unregistered.

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: default avatarJohn Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134809.110881699@de.ibm.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 0f8e8ef7

kernel/time/clocksource.c

+69 −28
Original line number Diff line number Diff line
@@ -145,6 +145,7 @@ static struct clocksource *watchdog; 
static struct timer_list watchdog_timer;

static DEFINE_SPINLOCK(watchdog_lock);

static cycle_t watchdog_last;

static int watchdog_running;



/*

 * Interval: 0.5sec Threshold: 0.0625s
@@ -168,6 +169,8 @@ static void clocksource_watchdog(unsigned long data) 
	int64_t wd_nsec, cs_nsec;



	spin_lock(&watchdog_lock);

	if (!watchdog_running)

		goto out;



	wdnow = watchdog->read(watchdog);

	wd_nsec = cyc2ns(watchdog, (wdnow - watchdog_last) & watchdog->mask);
@@ -217,9 +220,30 @@ static void clocksource_watchdog(unsigned long data) 
		watchdog_timer.expires += WATCHDOG_INTERVAL;

		add_timer_on(&watchdog_timer, next_cpu);

	}

out:

	spin_unlock(&watchdog_lock);

}



static inline void clocksource_start_watchdog(void)

{

	if (watchdog_running || !watchdog || list_empty(&watchdog_list))

		return;

	init_timer(&watchdog_timer);

	watchdog_timer.function = clocksource_watchdog;

	watchdog_last = watchdog->read(watchdog);

	watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;

	add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));

	watchdog_running = 1;

}



static inline void clocksource_stop_watchdog(void)

{

	if (!watchdog_running || (watchdog && !list_empty(&watchdog_list)))

		return;

	del_timer(&watchdog_timer);

	watchdog_running = 0;

}



static inline void clocksource_reset_watchdog(void)

{

	struct clocksource *cs;
@@ -237,55 +261,70 @@ static void clocksource_resume_watchdog(void) 
	spin_unlock_irqrestore(&watchdog_lock, flags);

}



static void clocksource_check_watchdog(struct clocksource *cs)

static void clocksource_enqueue_watchdog(struct clocksource *cs)

{

	unsigned long flags;



	spin_lock_irqsave(&watchdog_lock, flags);

	if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {

		int started = !list_empty(&watchdog_list);



		/* cs is a clocksource to be watched. */

		list_add(&cs->wd_list, &watchdog_list);

		if (!started && watchdog) {

			watchdog_last = watchdog->read(watchdog);

			watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;

			add_timer_on(&watchdog_timer,

				     cpumask_first(cpu_online_mask));

		}

		cs->flags &= ~CLOCK_SOURCE_WATCHDOG;

	} else {

		/* cs is a watchdog. */

		if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)

			cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;



		/* Pick the best watchdog. */

		if (!watchdog || cs->rating > watchdog->rating) {

			if (watchdog)

				del_timer(&watchdog_timer);

			watchdog = cs;

			init_timer(&watchdog_timer);

			watchdog_timer.function = clocksource_watchdog;



			/* Reset watchdog cycles */

			clocksource_reset_watchdog();

			/* Start if list is not empty */

			if (!list_empty(&watchdog_list)) {

				watchdog_last = watchdog->read(watchdog);

				watchdog_timer.expires =

					jiffies + WATCHDOG_INTERVAL;

				add_timer_on(&watchdog_timer,

					     cpumask_first(cpu_online_mask));

		}

	}

	/* Check if the watchdog timer needs to be started. */

	clocksource_start_watchdog();

	spin_unlock_irqrestore(&watchdog_lock, flags);

}



static void clocksource_dequeue_watchdog(struct clocksource *cs)

{

	struct clocksource *tmp;

	unsigned long flags;



	spin_lock_irqsave(&watchdog_lock, flags);

	if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {

		/* cs is a watched clocksource. */

		list_del_init(&cs->wd_list);

	} else if (cs == watchdog) {

		/* Reset watchdog cycles */

		clocksource_reset_watchdog();

		/* Current watchdog is removed. Find an alternative. */

		watchdog = NULL;

		list_for_each_entry(tmp, &clocksource_list, list) {

			if (tmp == cs || tmp->flags & CLOCK_SOURCE_MUST_VERIFY)

				continue;

			if (!watchdog || tmp->rating > watchdog->rating)

				watchdog = tmp;

		}

	}

	cs->flags &= ~CLOCK_SOURCE_WATCHDOG;

	/* Check if the watchdog timer needs to be stopped. */

	clocksource_stop_watchdog();

	spin_unlock_irqrestore(&watchdog_lock, flags);

}

#else

static void clocksource_check_watchdog(struct clocksource *cs)



#else /* CONFIG_CLOCKSOURCE_WATCHDOG */



static void clocksource_enqueue_watchdog(struct clocksource *cs)

{

	if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)

		cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;

}



static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }

static inline void clocksource_resume_watchdog(void) { }

#endif



#endif /* CONFIG_CLOCKSOURCE_WATCHDOG */



/**

 * clocksource_resume - resume the clocksource(s)
@@ -414,14 +453,13 @@ int clocksource_register(struct clocksource *cs) 
	clocksource_enqueue(cs);

	clocksource_select();

	spin_unlock_irqrestore(&clocksource_lock, flags);

	clocksource_check_watchdog(cs);

	clocksource_enqueue_watchdog(cs);

	return 0;

}

EXPORT_SYMBOL(clocksource_register);



/**

 * clocksource_change_rating - Change the rating of a registered clocksource

 *

 */

void clocksource_change_rating(struct clocksource *cs, int rating)

{
@@ -434,6 +472,7 @@ void clocksource_change_rating(struct clocksource *cs, int rating) 
	clocksource_select();

	spin_unlock_irqrestore(&clocksource_lock, flags);

}

EXPORT_SYMBOL(clocksource_change_rating);



/**

 * clocksource_unregister - remove a registered clocksource
@@ -442,11 +481,13 @@ void clocksource_unregister(struct clocksource *cs) 
{

	unsigned long flags;



	clocksource_dequeue_watchdog(cs);

	spin_lock_irqsave(&clocksource_lock, flags);

	list_del(&cs->list);

	clocksource_select();

	spin_unlock_irqrestore(&clocksource_lock, flags);

}

EXPORT_SYMBOL(clocksource_unregister);



#ifdef CONFIG_SYSFS

/**