From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: [PATCH 1/5] Add a global synchronization point for pvclock
Date: Mon, 19 Apr 2010 17:33:57 +0300
Message-ID: <4BCC69D5.3050209@redhat.com>
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Cc: Peter Zijlstra <peterz@infradead.org>,
	Jeremy Fitzhardinge <jeremy@goop.org>, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Zachary Amsden <zamsden@redhat.com>
To: Glauber Costa <glommer@redhat.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <20100419142158.GD14158@mothafucka.localdomain>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

On 04/19/2010 05:21 PM, Glauber Costa wrote:
>
>> Oh yes, just trying to avoid a patch with both atomic64_read() and
>> ACCESS_ONCE().
>>      
> you're mixing the private version of the patch you saw with this one.
> there isn't any atomic reads in here. I'll use a barrier then
>    

This patch writes last_value atomically, but reads it non-atomically.  A 
barrier is insufficient.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.