From: Andi Kleen <ak@suse.de>
To: "Bryan O'Sullivan" <bos@serpentine.com>
Subject: Re: [PATCH] Document Linux's memory barriers
Date: Tue, 7 Mar 2006 22:24:09 +0100
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On Tuesday 07 March 2006 22:14, Bryan O'Sullivan wrote:
> On Tue, 2006-03-07 at 12:57 +0100, Andi Kleen wrote:
> > > > True, I suppose. I should make it clear that these accessor functions
> > > > imply memory barriers, if indeed they do,
> > >
> > > They don't, but according to Documentation/DocBook/deviceiobook.tmpl
> > > they are performed by the compiler in the order specified.
> >
> > I don't think that's correct. Probably the documentation should
> > be fixed.
>
> That's why I hedged my words with "according to ..." :-)
>
> But on most arches those accesses do indeed seem to happen in-order.  On
> i386 and x86_64, it's a natural consequence of program store ordering.

Not true for reads on x86.

-Andi
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