linux-kernel - Re: [PATCH 03 of 36] x86: add memory barriers to wrmsr

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Message-ID: <20080624214441.13202f12@infradead.org>
Date:	Tue, 24 Jun 2008 21:44:41 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	x86@...nel.org, xen-devel <xen-devel@...ts.xensource.com>,
	Stephen Tweedie <sct@...hat.com>,
	Eduardo Habkost <ehabkost@...hat.com>,
	Mark McLoughlin <markmc@...hat.com>
Subject: Re: [PATCH 03 of 36] x86: add memory barriers to wrmsr

On Wed, 25 Jun 2008 00:18:59 -0400
Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> wrmsr is a special instruction which can have arbitrary system-wide
> effects.  We don't want the compiler to reorder it with respect to
> memory operations, so make it a memory barrier.

it's more readable for several of these cases to stick a barrier(); in
front and after it to be honest; that makes it more explicit that
these are deliberate compiler barriers rather than "actual" memory
access...


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