linux-kernel - Re: [PATCH] net: fix race in the receive/select

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Message-ID: <20090701072226.GN6760@one.firstfloor.org>
Date:	Wed, 1 Jul 2009 09:22:26 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Andi Kleen <andi@...stfloor.org>, jolsa@...hat.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	fbl@...hat.com, nhorman@...hat.com, davem@...hat.com,
	oleg@...hat.com, eric.dumazet@...il.com
Subject: Re: [PATCH] net: fix race in the receive/select

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@...ux.intel.com -- Speaking for myself only.
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