From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: MMIO and gcc re-ordering issue
Date: Wed, 28 May 2008 07:12:46 +1000
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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David Miller <davem@davemloft.net>, linux-arch@vger.kernel.org, scottwood@freescale.com, linuxppc-dev@ozlabs.org, alan@lxorguk.ukuu.org.uk, linux-kernel@vger.kernel.org, tpiepho@freescale.com


On Tue, 2008-05-27 at 09:47 -0700, Linus Torvalds wrote:
> 
> __read[bwlq]()/__write[bwlq]() are not serialized with a :"memory" 
> barrier, although since they still use "asm volatile" I suspect that
> i 
> practice they are probably serial too. Did not look very closely at
> any 
> generated code (only did a trivial test to see that the code looks 
> *roughly* correct).

Nah, asm volatile doesn't help, it does need the "memory" clobber too.

Cheers,
Ben.