Subject: Re: [PATCH] net: fix race in the receive/select

From: Andi Kleen <[email-masked]>
Date: Wed, 1 Jul 2009 08:27:32 +0200

On Wed, Jul 01, 2009 at 11:39:24AM +0800, Herbert Xu wrote:
> Andi Kleen <[email-masked]> wrote:
> > 
> > At least on x86 I can't see how it happens. mb() is only a compile
> > time barrier and the compiler doesn't optimize over indirect callbacks
> > like __pollwait() anyways.
> 
> mb() does more than just a compiler barrier, it also issues mfence.

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.

-Andi

-- 
[email-masked] -- Speaking for myself only.