From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from detroit.securenet-server.net ([209.51.153.26]:58340 "EHLO detroit.securenet-server.net") by vger.kernel.org with ESMTP id S1751526AbWCGUBh (ORCPT ); Tue, 7 Mar 2006 15:01:37 -0500 From: Jesse Barnes Subject: Re: [PATCH] Document Linux's memory barriers Date: Tue, 7 Mar 2006 12:01:21 -0800 References: <200603071134.52962.ak@suse.de> <1141759408.2617.9.camel@serpentine.pathscale.com> <200603071257.24234.ak@suse.de> In-Reply-To: <200603071257.24234.ak@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200603071201.22397.jbarnes@virtuousgeek.org> Sender: linux-arch-owner@vger.kernel.org To: Andi Kleen Cc: Bryan O'Sullivan , David Howells , torvalds@osdl.org, akpm@osdl.org, mingo@redhat.com, linux-arch@vger.kernel.org, linuxppc64-dev@ozlabs.org, linux-kernel@vger.kernel.org List-ID: On Tuesday, March 7, 2006 3:57 am, Andi Kleen wrote: > On Tuesday 07 March 2006 20:23, Bryan O'Sullivan wrote: > > On Tue, 2006-03-07 at 18:30 +0000, David Howells wrote: > > > True, I suppose. I should make it clear that these accessor > > > functions imply memory barriers, if indeed they do, > > > > They don't, but according to Documentation/DocBook/deviceiobook.tmpl > > they are performed by the compiler in the order specified. > > I don't think that's correct. Probably the documentation should > be fixed. On ia64 I'm pretty sure it's true, and it seems like it should be in the general case too. The compiler shouldn't reorder uncached memory accesses with volatile semantics... Jesse