From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <andi@firstfloor.org>
Subject: Re: Linux questions
Date: Tue, 04 Dec 2007 12:13:41 +0100
Message-ID: <p73r6i2k90a.fsf@bingen.suse.de>
References: <475538A4.76E4.0078.0@novell.com>
	<C37AE293.195B6%Keir.Fraser@cl.cam.ac.uk>
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To: Keir Fraser <Keir.Fraser@cl.cam.ac.uk>
Cc: xen-devel@lists.xensource.com, Jan Beulich <jbeulich@novell.com>, Samuel Thibault <samuel.thibault@eu.citrix.com>
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Keir Fraser <Keir.Fraser@cl.cam.ac.uk> writes:

> On 4/12/07 10:23, "Jan Beulich" <jbeulich@novell.com> wrote:
>
>> I have to disagree: At least the uses of barrier() in monotonic_clock() appear
>> to be in places where in reality (and from a theoretical standpoint) rmb()
>> ought to be used.
>
> We're sync'ing against concurrent updates of a this_cpu variable. We can
> only race updates in a local ISR, and hence barrier() suffices.

Not if you use RDTSC inside the loop.

-Andi