Re: PATCH: Race in 2.6.0-test2 timer code

From: Ingo Molnar (mingo@elte.hu)
Date: Fri Aug 01 2003 - 01:23:26 EST


On Thu, 31 Jul 2003 linas@austin.ibm.com wrote:

> Well, I'm confused by this a bit too, now. I saw this bug in 2.4 and I
> thought that Andrea was implying that it couldn't happen in 2.6. He
> seemed to be saying that the del_timer_sync() + add_timer() race can
> happen only in 2.4, where add_timer() is running on the 'wrong' cpu
> bacuase it got there through the evil run_all_timers()/TIMER_BH. Since
> there's no run_all_timers() in 2.6, he seemed to imply that the race
> 'couldn't happen'. Is he right?

it is correct, but it was me convincing Andrea about this, not the other
way around :-) Pls. re-read the email thread. My point still stands:

>> (in any case, i still think it would be safer to 'upgrade' the
>> add_timer() interface to be SMP-safe and to allow double-adds - but not
>> for any bug reason anymore.)

this should also make backporting easier.

        Ingo

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