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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: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134809.354926067@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Martin Schwidefsky 2009-08-14 15:47:25 +02:00 committed by Thomas Gleixner
parent fb63a0ebe6
commit c55c87c892
2 changed files with 40 additions and 17 deletions
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1
include/linux/clocksource.h
View File

@ -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)

56
kernel/time/clocksource.c
View File

@ -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.
*/
int 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);
}
/*
* Cycle through CPUs to check if the CPUs stay synchronized
* to each other.
*/
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)