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authorThomas Gleixner <tglx@linutronix.de>2009-08-28 14:25:24 -0400
committerThomas Gleixner <tglx@linutronix.de>2009-08-28 14:25:24 -0400
commit7285dd7fd375763bfb8ab1ac9cf3f1206f503c16 (patch)
tree42f809ab3616cc3d93d655acccfc2d54e9f6d0e4 /include
parent90cba64a5f672a239f43ec5cb9a11b806887331e (diff)
clocksource: Resolve cpu hotplug dead lock with TSC unstable
Martin Schwidefsky analyzed it: To register a clocksource the clocksource_mutex is acquired and if necessary timekeeping_notify is called to install the clocksource as the timekeeper clock. timekeeping_notify uses stop_machine which needs to take cpu_add_remove_lock mutex. Starting a new cpu is done with the cpu_add_remove_lock mutex held. native_cpu_up checks the tsc of the new cpu and if the tsc is no good clocksource_change_rating is called. Which needs the clocksource_mutex and the deadlock is complete. The solution is to replace the TSC via the clocksource watchdog mechanism. Mark the TSC as unstable and schedule the watchdog work so it gets removed in the watchdog thread context. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> LKML-Reference: <new-submission> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: John Stultz <johnstul@us.ibm.com>
Diffstat (limited to 'include')
-rw-r--r--include/linux/clocksource.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 9ea40ff26f0e..83d2fbd81b93 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -277,6 +277,7 @@ extern struct clocksource* clocksource_get_next(void);
277extern void clocksource_change_rating(struct clocksource *cs, int rating); 277extern void clocksource_change_rating(struct clocksource *cs, int rating);
278extern void clocksource_resume(void); 278extern void clocksource_resume(void);
279extern struct clocksource * __init __weak clocksource_default_clock(void); 279extern struct clocksource * __init __weak clocksource_default_clock(void);
280extern void clocksource_mark_unstable(struct clocksource *cs);
280 281
281#ifdef CONFIG_GENERIC_TIME_VSYSCALL 282#ifdef CONFIG_GENERIC_TIME_VSYSCALL
282extern void update_vsyscall(struct timespec *ts, struct clocksource *c); 283extern void update_vsyscall(struct timespec *ts, struct clocksource *c);