Re: PATCH: Race in 2.6.0-test2 timer code

From: Andrew Morton (akpm@osdl.org)
Date: Wed Jul 30 2003 - 05:51:40 EST


Ingo Molnar <mingo@elte.hu> wrote:
>
> But on 2.6 the timer will run precisely on the CPU it was added, so i
> think the race is not possible.

well there is add_timer_on()...

I still don't see the race in the itimer code actually. On return
from del_timer_sync() we know that the timer is not pending, even
if it_real_fn() tried to re-add it.

ie: why does the below "crash"?

Andrea Arcangeli <andrea@suse.de> wrote:
>
> cpu0 cpu1
> ------------ --------------------
>
> do_setitimer
> it_real_fn
> del_timer_sync add_timer -> crash

(Does the timer_pending() test in del_timer_sync() needs some
barriers btw?)

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