Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932529AbWB1To6 (ORCPT ); Tue, 28 Feb 2006 14:44:58 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932530AbWB1To5 (ORCPT ); Tue, 28 Feb 2006 14:44:57 -0500 Received: from mx.pathscale.com ([64.160.42.68]:18143 "EHLO mx.pathscale.com") by vger.kernel.org with ESMTP id S932529AbWB1To5 (ORCPT ); Tue, 28 Feb 2006 14:44:57 -0500 Subject: Re: [PATCH] Define wc_wmb, a write barrier for PCI write combining From: "Bryan O'Sullivan" To: Benjamin LaHaise , Andi Kleen Cc: Benjamin LaHaise , Andrew Morton , linux-kernel In-Reply-To: <200602282033.48570.ak@suse.de> References: <1140841250.2587.33.camel@localhost.localdomain> <20060228190354.GE24306@kvack.org> <1141154424.20227.11.camel@serpentine.pathscale.com> <200602282033.48570.ak@suse.de> Content-Type: text/plain Organization: PathScale, Inc. Date: Tue, 28 Feb 2006 11:44:51 -0800 Message-Id: <1141155892.20227.26.camel@serpentine.pathscale.com> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 736 Lines: 19 On Tue, 2006-02-28 at 20:33 +0100, Andi Kleen wrote: > Are you sure you used the right instruction? Normally CLFLUSH is used > for such things, not a write barrier which really only changes ordering. Hmm. It's possible we're just getting lucky because another write happens somewhere else soon after the last write we perform as part of a packet send. Perhaps, for complete correctness, we should be using CLFLUSH instead of the last barrier. I'll have to look into this. Thanks,