Messages in this thread | | | Date | Sat, 22 Aug 2009 23:14:57 +0200 | From | Martin Schwidefsky <> | Subject | Re: [tip:timers/core] x86: Do not unregister PIT clocksource on PIT oneshot setup/shutdown |
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On Sat, 22 Aug 2009 12:35:41 +0200 Ingo Molnar <mingo@elte.hu> wrote:
> even after this fix, -tip testing found yet another circular locking > bug, on a 32-bit Core2 laptop:
You got to love lockdep .. another ugly one: clocksource_register: has clocksource_mutex, get cpu_add_remove_lock native_cpu_up: has cpu_add_remove_lock, get clocksource_mutex
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.
-- blue skies, Martin.
"Reality continues to ruin my life." - Calvin.
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