Re: PATCH: Race in 2.6.0-test2 timer code

From: Ingo Molnar (mingo@elte.hu)
Date: Fri Aug 01 2003 - 01:27:35 EST


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

> OK, I looked at removing run_all_timers, it doesn't seem too hard.
>
> I would need to:
> -- add TIMER_SOFTIRQ to interrupts.h,
> -- add open_softirq (run_timer_softirq) to timer.c init_timer()
> -- move guts of run_local_timers() to run_timer_softirq()
> -- remove bh locks in above, not yet sure about other locks
> -- remove TIMER_BH everywhere. Or rather, remove it for those
> arches that support cpu-local timer interupts (curently x86 & freinds,
> soon hopefully ppc64, I attach it below, in case other arches want to
> play with this).
>
> Is that right?

no. In 2.4 there are (and/or can be) all sorts of assumptions about
TIMER_BH being serialized with other bh contexts (eg. the serial bh),
that's why i added the TIMER_BH logic to the 2.4 timer-scalability patch.
You cannot just remove TIMER_BH. The way we did it in 2.5 was to remove
_all_ bhs and thus all assumptions about serialization. This is not an
option for 2.4 in any case.

        Ingo

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