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| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2009-08-18 17:09:42 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2009-08-19 12:00:56 +0200 |
| commit | 01548f4d3e8e94caf323a4f664eb347fd34a34ab (patch) | |
| tree | 2717e7d4dd781be2d57737df96b074451090f3d9 /kernel | |
| parent | d0981a1b21a03866c8da7f44e35e389c2e0d6061 (diff) | |
| download | linux-01548f4d3e8e94caf323a4f664eb347fd34a34ab.tar.gz linux-01548f4d3e8e94caf323a4f664eb347fd34a34ab.tar.bz2 linux-01548f4d3e8e94caf323a4f664eb347fd34a34ab.zip | |
clocksource: Avoid clocksource watchdog circular locking dependency
stop_machine from a multithreaded workqueue is not allowed because
of a circular locking dependency between cpu_down and the workqueue
execution. Use a kernel thread to do the clocksource downgrade.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: john stultz <johnstul@us.ibm.com>
LKML-Reference: <20090818170942.3ab80c91@skybase>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/time/clocksource.c | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index c6bff11f7957..e0c86ad6e9fb 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -29,6 +29,7 @@ #include <linux/module.h> #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */ #include <linux/tick.h> +#include <linux/kthread.h> void timecounter_init(struct timecounter *tc, const struct cyclecounter *cc, @@ -130,7 +131,7 @@ static DEFINE_SPINLOCK(watchdog_lock); static cycle_t watchdog_last; static int watchdog_running; -static void clocksource_watchdog_work(struct work_struct *work); +static int clocksource_watchdog_kthread(void *data); static void __clocksource_change_rating(struct clocksource *cs, int rating); /* @@ -139,6 +140,15 @@ static void __clocksource_change_rating(struct clocksource *cs, int rating); #define WATCHDOG_INTERVAL (HZ >> 1) #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4) +static void clocksource_watchdog_work(struct work_struct *work) +{ + /* + * If kthread_run fails the next watchdog scan over the + * watchdog_list will find the unstable clock again. + */ + kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog"); +} + static void clocksource_unstable(struct clocksource *cs, int64_t delta) { printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n", @@ -167,8 +177,10 @@ static void clocksource_watchdog(unsigned long data) list_for_each_entry(cs, &watchdog_list, wd_list) { /* Clocksource already marked unstable? */ - if (cs->flags & CLOCK_SOURCE_UNSTABLE) + if (cs->flags & CLOCK_SOURCE_UNSTABLE) { + schedule_work(&watchdog_work); continue; + } csnow = cs->read(cs); @@ -304,7 +316,7 @@ static void clocksource_dequeue_watchdog(struct clocksource *cs) spin_unlock_irqrestore(&watchdog_lock, flags); } -static void clocksource_watchdog_work(struct work_struct *work) +static int clocksource_watchdog_kthread(void *data) { struct clocksource *cs, *tmp; unsigned long flags; @@ -327,6 +339,7 @@ static void clocksource_watchdog_work(struct work_struct *work) __clocksource_change_rating(cs, 0); } mutex_unlock(&clocksource_mutex); + return 0; } #else /* CONFIG_CLOCKSOURCE_WATCHDOG */ |