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Commit c55c87c8 authored by Martin Schwidefsky's avatar Martin Schwidefsky Committed by Thomas Gleixner
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clocksource: Move watchdog downgrade to a work queue thread 



Move the downgrade of an unstable clocksource from the timer interrupt
context into the process context of a work queue thread. This is
needed to be able to do the clocksource switch with stop_machine.

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: <20090814134809.354926067@de.ibm.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent fb63a0eb

include/linux/clocksource.h

+1 −0
Original line number Diff line number Diff line
@@ -213,6 +213,7 @@ extern struct clocksource *clock; /* current clocksource */ 


#define CLOCK_SOURCE_WATCHDOG			0x10

#define CLOCK_SOURCE_VALID_FOR_HRES		0x20

#define CLOCK_SOURCE_UNSTABLE			0x40



/* simplify initialization of mask field */

#define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)

kernel/time/clocksource.c

+39 −17
Original line number Diff line number Diff line
@@ -143,10 +143,13 @@ fs_initcall(clocksource_done_booting); 
static LIST_HEAD(watchdog_list);

static struct clocksource *watchdog;

static struct timer_list watchdog_timer;

static struct work_struct watchdog_work;

static DEFINE_SPINLOCK(watchdog_lock);

static cycle_t watchdog_last;

static int watchdog_running;



static void clocksource_watchdog_work(struct work_struct *work);



/*

 * Interval: 0.5sec Threshold: 0.0625s

 */
@@ -158,15 +161,16 @@ static void clocksource_unstable(struct clocksource *cs, int64_t delta) 
	printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",

	       cs->name, delta);

	cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);

	clocksource_change_rating(cs, 0);

	list_del(&cs->wd_list);

	cs->flags |= CLOCK_SOURCE_UNSTABLE;

	schedule_work(&watchdog_work);

}



static void clocksource_watchdog(unsigned long data)

{

	struct clocksource *cs, *tmp;

	struct clocksource *cs;

	cycle_t csnow, wdnow;

	int64_t wd_nsec, cs_nsec;

	int next_cpu;



	spin_lock(&watchdog_lock);

	if (!watchdog_running)
@@ -176,7 +180,12 @@ static void clocksource_watchdog(unsigned long data) 
	wd_nsec = cyc2ns(watchdog, (wdnow - watchdog_last) & watchdog->mask);

	watchdog_last = wdnow;



	list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {

	list_for_each_entry(cs, &watchdog_list, wd_list) {



		/* Clocksource already marked unstable? */

		if (cs->flags & CLOCK_SOURCE_UNSTABLE)

			continue;



		csnow = cs->read(cs);



		/* Clocksource initialized ? */
@@ -207,19 +216,15 @@ static void clocksource_watchdog(unsigned long data) 
		}

	}



	if (!list_empty(&watchdog_list)) {

	/*

		 * Cycle through CPUs to check if the CPUs stay

		 * synchronized to each other.

	 * Cycle through CPUs to check if the CPUs stay synchronized

	 * to each other.

	 */

		int next_cpu = cpumask_next(raw_smp_processor_id(),

					    cpu_online_mask);



	next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);

	if (next_cpu >= nr_cpu_ids)

		next_cpu = cpumask_first(cpu_online_mask);

	watchdog_timer.expires += WATCHDOG_INTERVAL;

	add_timer_on(&watchdog_timer, next_cpu);

	}

out:

	spin_unlock(&watchdog_lock);

}
@@ -228,6 +233,7 @@ static inline void clocksource_start_watchdog(void) 
{

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

		return;

	INIT_WORK(&watchdog_work, clocksource_watchdog_work);

	init_timer(&watchdog_timer);

	watchdog_timer.function = clocksource_watchdog;

	watchdog_last = watchdog->read(watchdog);
@@ -313,6 +319,22 @@ static void clocksource_dequeue_watchdog(struct clocksource *cs) 
	spin_unlock_irqrestore(&watchdog_lock, flags);

}



static void clocksource_watchdog_work(struct work_struct *work)

{

	struct clocksource *cs, *tmp;

	unsigned long flags;



	spin_lock_irqsave(&watchdog_lock, flags);

	list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list)

		if (cs->flags & CLOCK_SOURCE_UNSTABLE) {

			list_del_init(&cs->wd_list);

			clocksource_change_rating(cs, 0);

		}

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

	clocksource_stop_watchdog();

	spin_unlock(&watchdog_lock);

}



#else /* CONFIG_CLOCKSOURCE_WATCHDOG */



static void clocksource_enqueue_watchdog(struct clocksource *cs)