Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932559AbWCHTyb (ORCPT ); Wed, 8 Mar 2006 14:54:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932557AbWCHTyb (ORCPT ); Wed, 8 Mar 2006 14:54:31 -0500 Received: from detroit.securenet-server.net ([209.51.153.26]:25219 "EHLO detroit.securenet-server.net") by vger.kernel.org with ESMTP id S932555AbWCHTya (ORCPT ); Wed, 8 Mar 2006 14:54:30 -0500 From: Jesse Barnes To: Linus Torvalds Subject: Re: [PATCH] Document Linux's memory barriers [try #2] Date: Wed, 8 Mar 2006 11:54:21 -0800 User-Agent: KMail/1.9.1 Cc: David Howells , Alan Cox , akpm@osdl.org, mingo@redhat.com, linux-arch@vger.kernel.org, linuxppc64-dev@ozlabs.org, linux-kernel@vger.kernel.org References: <20060308184500.GA17716@devserv.devel.redhat.com> <14275.1141844922@warthog.cambridge.redhat.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200603081154.21960.jbarnes@virtuousgeek.org> X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - detroit.securenet-server.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [0 0] / [47 12] X-AntiAbuse: Sender Address Domain - virtuousgeek.org X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 825 Lines: 17 On Wednesday, March 8, 2006 11:26 am, Linus Torvalds wrote: > But if you have a separate IO fabric and basically two different CPU's > can get to one device through two different paths, no amount of write > barriers of any kind will ever help you. No, that's exactly the case that mmiowb() was designed to protect against. It ensures that your writes have arrived at the destination bridge, which means after that point any other CPUs writing to the same device will have their data actually hit the device afterwards. Hopefully deviceiobook.tmpl makes that clear... Jesse - 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/