Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753094AbXIHLeR (ORCPT ); Sat, 8 Sep 2007 07:34:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751288AbXIHLeG (ORCPT ); Sat, 8 Sep 2007 07:34:06 -0400 Received: from twinlark.arctic.org ([207.29.250.54]:54985 "EHLO twinlark.arctic.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751017AbXIHLeF (ORCPT ); Sat, 8 Sep 2007 07:34:05 -0400 Date: Sat, 8 Sep 2007 04:34:03 -0700 (PDT) From: dean gaudet To: Nick Piggin cc: Linus Torvalds , ak@suse.de, Jesse Barnes , linux-kernel@vger.kernel.org Subject: Re: Intel Memory Ordering White Paper In-Reply-To: <200709090348.28076.nickpiggin@yahoo.com.au> Message-ID: References: <200709071526.51169.jesse.barnes@intel.com> <200709090334.27677.nickpiggin@yahoo.com.au> <200709090348.28076.nickpiggin@yahoo.com.au> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1069 Lines: 25 On Sun, 9 Sep 2007, Nick Piggin wrote: > I've also heard that string operations do not follow the normal ordering, but > that's just with respect to individual loads/stores in the one operation, I > hope? And they will still follow ordering rules WRT surrounding loads and > stores? see section 7.2.3 of intel volume 3A... "Code dependent upon sequential store ordering should not use the string operations for the entire data structure to be stored. Data and semaphores should be separated. Order dependent code should use a discrete semaphore uniquely stored to after any string operations to allow correctly ordered data to be seen by all processors." i think we need sfence after things like copy_page, clear_page, and possibly copy_user... at least on intel processors with fast strings option enabled. -dean - 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/