Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751391AbWARRXd (ORCPT ); Wed, 18 Jan 2006 12:23:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751392AbWARRXd (ORCPT ); Wed, 18 Jan 2006 12:23:33 -0500 Received: from mx.pathscale.com ([64.160.42.68]:34501 "EHLO mx.pathscale.com") by vger.kernel.org with ESMTP id S1751391AbWARRXd (ORCPT ); Wed, 18 Jan 2006 12:23:33 -0500 Subject: Re: Why is wmb() a no-op on x86_64? From: "Bryan O'Sullivan" To: Jes Sorensen Cc: Andi Kleen , linux-kernel@vger.kernel.org In-Reply-To: References: <1137601417.4757.38.camel@serpentine.pathscale.com> <200601181729.36423.ak@suse.de> <1137603169.4757.50.camel@serpentine.pathscale.com> Content-Type: text/plain Organization: PathScale, Inc. Date: Wed, 18 Jan 2006 09:23:27 -0800 Message-Id: <1137605007.4757.57.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: 837 Lines: 26 On Wed, 2006-01-18 at 12:06 -0500, Jes Sorensen wrote: > A job for mmiowb() perhaps? That might be suitable. It's a no-op on most platforms, but it's only used by a handful of drivers: drivers/scsi/qla1280.c drivers/sn/ioc4.c drivers/net/bnx2.c drivers/net/sky2.c drivers/net/s2io.c drivers/net/tg3.c If the semantics were to change so that it really did a write barrier, I doubt any existing users would notice. In fact, based on the comments in some drivers, at least some authors think it does already, when it typically doesn't.