Thomas Gleixner 7b7422a566 clocksource: Prevent potential kgdb dead lock ... commit 0f8e8ef7 (clocksource: Simplify clocksource watchdog resume logic) introduced a potential kgdb dead lock. When the kernel is stopped by kgdb inside code which holds watchdog_lock then kgdb dead locks in clocksource_resume_watchdog(). clocksource_resume_watchdog() is called from kbdg via clocksource_touch_watchdog() to avoid that the clock source watchdog marks TSC unstable after the kernel has been stopped. Solve this by replacing spin_lock with a spin_trylock and just return in case the lock is held. Not resetting the watchdog might result in TSC becoming marked unstable, but that's an acceptable penalty for using kgdb. The timekeeping is anyway easily screwed up by kgdb when the system uses either jiffies or a clock source which wraps in short intervals (e.g. pm_timer wraps about every 4.6s), so we really do not have to worry about that occasional TSC marked unstable side effect. The second caller of clocksource_resume_watchdog() is clocksource_resume(). The trylock is safe here as well because the system is UP at this point, interrupts are disabled and nothing else can hold watchdog_lock(). Reported-by: Jason Wessel <jason.wessel@windriver.com> LKML-Reference: <1264480000-6997-4-git-send-email-jason.wessel@windriver.com> Cc: kgdb-bugreport@lists.sourceforge.net Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: John Stultz <johnstul@us.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>		2010-01-26 14:53:16 +01:00
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clockevents.c	clockevent: Don't remove broadcast device when cpu is dead	2010-01-18 14:44:50 +01:00
clocksource.c	clocksource: Prevent potential kgdb dead lock	2010-01-26 14:53:16 +01:00
jiffies.c
Kconfig
Makefile
ntp.c
tick-broadcast.c	clockevents: Convert to raw_spinlock	2009-12-14 23:55:34 +01:00
tick-common.c	clockevents: Convert to raw_spinlock	2009-12-14 23:55:34 +01:00
tick-internal.h	clockevents: Make tick_device_lock static	2009-12-14 23:55:34 +01:00
tick-oneshot.c	nohz: Allow 32-bit machines to sleep for more than 2.15 seconds	2009-11-13 20:46:24 +01:00
tick-sched.c	Merge branch 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-12-08 19:27:08 -08:00
timecompare.c	timecompare: fix half-Y2K38 problem in timecompare_update while calculating offset	2009-12-16 07:19:57 -08:00
timeconv.c
timekeeping.c	Revert "time: Remove xtime_cache"	2009-12-22 14:10:37 -08:00
timer_list.c	cpumask: avoid dereferencing struct cpumask	2009-12-17 11:43:29 +10:30
timer_stats.c	hrtimers: Convert to raw_spinlocks	2009-12-14 23:55:34 +01:00