From: Eugene Surovegin <ebs@ebshome.net>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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 17:34:59 -0700 [thread overview]
Message-ID: <20050630003459.GA1265@gate.ebshome.net> (raw)
In-Reply-To: <1120087568.31924.14.camel@gaston>
On Thu, Jun 30, 2005 at 09:26:07AM +1000, Benjamin Herrenschmidt wrote:
>
> > Execution is resumed exactly where it has been interrupted.
> >
> > > The idea behind my patch was to get rid of that nr_free_contexts counter
> > > that is (I thing) redundant with the context_map.
> >
> > Apparently its there to avoid the spinlock exactly on !FEW_CONTEXTS machines.
> >
> > I suppose that what happens is that get_mmu_context() gets preempted after stealing
> > a context (so nr_free_contexts = 0), but before setting next_mmu_context to the
> > next entry
> >
> > next_mmu_context = (ctx + 1) & LAST_CONTEXT;
>
> Ugh ? Can switch_mm() be preempted at all ? Did I miss yet another
> "let's open 10 gazillion races for gun" Ingo patch ?
No, it can't. schedule() disables preemption at the very beginning.
--
Eugene
next prev parent reply other threads:[~2005-06-30 0:35 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
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 [this message]
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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