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| author | J. Bruce Fields <bfields@citi.umich.edu> | 2010-03-04 12:03:16 -0500 |
|---|---|---|
| committer | J. Bruce Fields <bfields@citi.umich.edu> | 2010-03-04 12:04:51 -0500 |
| commit | 4ea41e2de5bba756858bb40f964e3490b6d1a25c (patch) | |
| tree | 51a688be321dd42f80d8a0c966eb6a60408d50b3 /kernel/time/clocksource.c | |
| parent | 8d75da8afd068fa58b35e69c7c8c46770d9e7a98 (diff) | |
| parent | 398007f863a4af2b4a5a07219c5a617f1a098115 (diff) | |
Merge branch 'for-linus' of git://oss.sgi.com/xfs/xfs into for-2.6.34-incoming
Resolve merge conflict in fs/xfs/linux-2.6/xfs_export.c.
Diffstat (limited to 'kernel/time/clocksource.c')
| -rw-r--r-- | kernel/time/clocksource.c | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index e85c23404d34..13700833c181 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -343,7 +343,19 @@ static void clocksource_resume_watchdog(void) { unsigned long flags; - spin_lock_irqsave(&watchdog_lock, flags); + /* + * We use trylock here to avoid a potential dead lock when + * kgdb calls this code after the kernel has been stopped with + * watchdog_lock held. When watchdog_lock is held we just + * return and accept, that the watchdog might trigger and mark + * the monitored clock source (usually TSC) unstable. + * + * This does not affect the other caller clocksource_resume() + * because at this point the kernel is UP, interrupts are + * disabled and nothing can hold watchdog_lock. + */ + if (!spin_trylock_irqsave(&watchdog_lock, flags)) + return; clocksource_reset_watchdog(); spin_unlock_irqrestore(&watchdog_lock, flags); } @@ -458,8 +470,8 @@ void clocksource_resume(void) * clocksource_touch_watchdog - Update watchdog * * Update the watchdog after exception contexts such as kgdb so as not - * to incorrectly trip the watchdog. - * + * to incorrectly trip the watchdog. This might fail when the kernel + * was stopped in code which holds watchdog_lock. */ void clocksource_touch_watchdog(void) { |