Date: Wed, 1 Jul 2009 09:22:26 +0200
From: Andi Kleen <andi@firstfloor.org>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Andi Kleen <andi@firstfloor.org>, jolsa@redhat.com, netdev@vger.kernel.org,
       linux-kernel@vger.kernel.org, fbl@redhat.com, nhorman@redhat.com,
       davem@redhat.com, oleg@redhat.com, eric.dumazet@gmail.com
Subject: Re: [PATCH] net: fix race in the receive/select
Message-ID: <20090701072226.GN6760@one.firstfloor.org>
References: <87eit3l7y6.fsf@basil.nowhere.org> <20090701033924.GA29762@gondor.apana.org.au> <20090701062732.GK6760@one.firstfloor.org> <20090701070332.GA31103@gondor.apana.org.au>
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On Wed, Jul 01, 2009 at 03:03:32PM +0800, Herbert Xu wrote:
> On Wed, Jul 01, 2009 at 08:27:32AM +0200, Andi Kleen wrote:
> >
> > mfence is not needed for normal C code (not using non temporal
> > stores) in the Linux memory model on x86 and is a no-op. Only the compile
> > time barrier matters.
> 
> In that case this bug needs to be digged deeper regardless of
> this patch.

Agreed.

I suspect the reordering of the wake queue tests might makes a difference, but
in this case to ensure they are always tested in the proper order by
the compiler would need more smp_rmb()s

-Andi

-- 
ak@linux.intel.com -- Speaking for myself only.
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