From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Guillaume Autran <gautran@mrv.com>
Cc: linux-ppc-embedded <linuxppc-embedded@ozlabs.org>
Subject: Re: [PATCH] 8xx: get_mmu_context() for (very) FEW_CONTEXTS and KERNEL_PREEMPT race/starvation issue
Date: Wed, 29 Jun 2005 14:15:30 +1000 [thread overview]
Message-ID: <1120018530.5133.241.camel@gaston> (raw)
In-Reply-To: <42C153E1.3060004@mrv.com>
On Tue, 2005-06-28 at 09:42 -0400, Guillaume Autran wrote:
> Hi,
>
> I happen to notice a race condition in the mmu_context code for the 8xx
> with very few context (16 MMU contexts) and kernel preemption enable. It
> is hard to reproduce has it shows only when many processes are
> created/destroy and the system is doing a lot of IRQ processing.
>
> In short, one process is trying to steal a context that is in the
> process of being freed (mm->context == NO_CONTEXT) but not completely
> freed (nr_free_contexts == 0).
> The steal_context() function does not do anything and the process stays
> in the loop forever.
>
> Anyway, I got a patch that fixes this part. Does not seem to affect
> scheduling latency at all.
>
> Comments are appreciated.
Your patch seems to do a hell lot more than fixing this race ... What
about just calling preempt_disable() in destroy_context() instead ?
Ben.
next prev parent reply other threads:[~2005-06-29 4:20 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-06-25 14:53 [PATCH] 8xx: map_page() skip pinned region and tlbie debugging aid Marcelo Tosatti
2005-06-25 22:24 ` Dan Malek
2005-06-26 14:30 ` Marcelo Tosatti
2005-06-27 13:39 ` Marcelo Tosatti
2005-06-27 20:46 ` Dan Malek
2005-06-28 6:30 ` Benjamin Herrenschmidt
2005-06-28 13:42 ` [PATCH] 8xx: get_mmu_context() for (very) FEW_CONTEXTS and KERNEL_PREEMPT race/starvation issue Guillaume Autran
2005-06-29 4:15 ` Benjamin Herrenschmidt [this message]
2005-06-29 15:32 ` Guillaume Autran
2005-06-29 15:54 ` Marcelo Tosatti
2005-06-29 21:25 ` Guillaume Autran
2005-06-29 17:00 ` Marcelo Tosatti
2005-06-29 23:26 ` Benjamin Herrenschmidt
2005-06-29 19:38 ` Marcelo Tosatti
2005-06-30 13:54 ` Guillaume Autran
2005-07-05 13:12 ` Guillaume Autran
2005-06-30 0:34 ` Eugene Surovegin
2005-06-29 23:24 ` Benjamin Herrenschmidt
2005-06-28 13:53 ` [PATCH] 8xx: map_page() skip pinned region and tlbie debugging aid Dan Malek
2005-06-28 23:47 ` Benjamin Herrenschmidt
2005-06-29 17:19 ` Marcelo Tosatti
2005-06-29 23:31 ` Benjamin Herrenschmidt
2005-06-30 18:05 ` Dan Malek
2005-06-30 23:29 ` Benjamin Herrenschmidt
2005-07-01 7:01 ` Pantelis Antoniou
2005-06-30 17:49 ` Dan Malek
2005-06-27 14:28 ` [PATCH] 8xx: tlbie debugging aid (try #2) Marcelo Tosatti
2005-06-27 20:18 ` Dan Malek
2005-06-27 14:56 ` Marcelo Tosatti
2005-06-27 20:53 ` Dan Malek
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