Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753589Ab0DSKjL (ORCPT ); Mon, 19 Apr 2010 06:39:11 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:39947 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752632Ab0DSKjJ (ORCPT ); Mon, 19 Apr 2010 06:39:09 -0400 Subject: Re: [PATCH 1/5] Add a global synchronization point for pvclock From: Peter Zijlstra To: Jeremy Fitzhardinge Cc: Glauber Costa , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, avi@redhat.com, Marcelo Tosatti , Zachary Amsden In-Reply-To: <4BC8CA52.4090703@goop.org> References: <1271356648-5108-1-git-send-email-glommer@redhat.com> <1271356648-5108-2-git-send-email-glommer@redhat.com> <4BC8CA52.4090703@goop.org> Content-Type: text/plain; charset="UTF-8" Date: Mon, 19 Apr 2010 12:39:05 +0200 Message-ID: <1271673545.1674.743.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 602 Lines: 15 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. -- 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/