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Date: Tue, 19 Feb 2002 14:17:04 -0800
From: Jesse Barnes <jbarnes@sgi.com>
To: Keith Owens <kaos@ocs.com.au>
Cc: David Mosberger <davidm@hpl.hp.com>, Dan Maas <dmaas@dcine.com>,
        linux-kernel@vger.kernel.org,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Ben Collins <bcollins@debian.org>
Subject: Re: readl/writel and memory barriers
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On Wed, Feb 20, 2002 at 09:05:37AM +1100, Keith Owens wrote:
> On Tue, 19 Feb 2002 10:35:06 -0800, 
> Jesse Barnes <jbarnes@sgi.com> wrote:
> >Making a variable volatile doesn't guarantee that the compiler won't
> >reorder references to it, AFAIK.
> 
> Ignoring the issue of hardware that reorders I/O, volatile accesses
> must not be reordered by the compiler.  From a C9X draft (1999, anybody
> have the current C standard online?) :-

Of course volatile references must be ordered wrt each other, but a
reference to a volatile doesn't preclude the compiler from moving it
above or below accesses to other variables.  That is, it doesn't act
as an optimization barrier.  Sound right?  I guess I'm getting a
little off-topic here...

Jesse
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