Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763747AbXF0Xaa (ORCPT ); Wed, 27 Jun 2007 19:30:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759424AbXF0XaX (ORCPT ); Wed, 27 Jun 2007 19:30:23 -0400 Received: from x35.xmailserver.org ([64.71.152.41]:1778 "EHLO x35.xmailserver.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761960AbXF0XaW (ORCPT ); Wed, 27 Jun 2007 19:30:22 -0400 X-AuthUser: davidel@xmailserver.org Date: Wed, 27 Jun 2007 16:30:15 -0700 (PDT) From: Davide Libenzi X-X-Sender: davide@alien.or.mcafeemobile.com To: Linus Torvalds cc: Nick Piggin , Eric Dumazet , Chuck Ebbert , Ingo Molnar , Jarek Poplawski , Miklos Szeredi , chris@atlee.ca, Linux Kernel Mailing List , tglx@linutronix.de, Andrew Morton Subject: Re: [BUG] long freezes on thinkpad t60 In-Reply-To: Message-ID: References: <20070620093612.GA1626@ff.dom.local> <20070621073031.GA683@elte.hu> <20070621160817.GA22897@elte.hu> <467AAB04.2070409@redhat.com> <20070621202917.a2bfbfc7.dada1@cosmosbay.com> <4680D162.9050603@yahoo.com.au> <4681F448.3040201@yahoo.com.au> X-GPG-FINGRPRINT: CFAE 5BEE FD36 F65E E640 56FE 0974 BF23 270F 474E X-GPG-PUBLIC_KEY: http://www.xmailserver.org/davidel.asc 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: 1093 Lines: 27 On Wed, 27 Jun 2007, Linus Torvalds wrote: > > IOW shouldn't an mfence always be there? Not only loads could leak up > > into the wait phase, but stores too, if they have no dependency with the > > "head" and "tail" loads. > > Stores never "leak up". They only ever leak down (ie past subsequent loads > or stores), so you don't need to worry about them. That's actually already > documented (although not in those terms), and if it wasn't true, then we > couldn't do the spin unlock with just a regular store anyway. Yes, Intel has never done that. They'll probably never do it since it'll break a lot of system software (unless they use a new mode-bit that allows system software to enable lose-ordering). Although I clearly remember to have read in one of their P4 optimization manuals to not assume this in the future. - Davide - 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/