Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754150Ab0DSKuv (ORCPT ); Mon, 19 Apr 2010 06:50:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:27533 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751824Ab0DSKut (ORCPT ); Mon, 19 Apr 2010 06:50:49 -0400 Message-ID: <4BCC3584.1050501@redhat.com> Date: Mon, 19 Apr 2010 13:50:44 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100330 Fedora/3.0.4-1.fc12 Thunderbird/3.0.4 MIME-Version: 1.0 To: Peter Zijlstra CC: Jeremy Fitzhardinge , Glauber Costa , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Marcelo Tosatti , Zachary Amsden Subject: Re: [PATCH 1/5] Add a global synchronization point for pvclock References: <1271356648-5108-1-git-send-email-glommer@redhat.com> <1271356648-5108-2-git-send-email-glommer@redhat.com> <4BC8CA52.4090703@goop.org> <1271673545.1674.743.camel@laptop> In-Reply-To: <1271673545.1674.743.camel@laptop> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 794 Lines: 25 On 04/19/2010 01:39 PM, Peter Zijlstra wrote: > On Fri, 2010-04-16 at 13:36 -0700, Jeremy Fitzhardinge wrote: > >>> + do { >>> + last = last_value; >>> >>> >> Does this need a barrier() to prevent the compiler from re-reading >> last_value for the subsequent lines? Otherwise "(ret< last)" and >> "return last" could execute with different values for "last". >> >> > ACCESS_ONCE() is your friend. > I think it's implied with atomic64_read(). -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/