Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759877AbYHNSxx (ORCPT ); Thu, 14 Aug 2008 14:53:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752638AbYHNSxo (ORCPT ); Thu, 14 Aug 2008 14:53:44 -0400 Received: from tomts43.bellnexxia.net ([209.226.175.110]:37140 "EHLO tomts43-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751286AbYHNSxn (ORCPT ); Thu, 14 Aug 2008 14:53:43 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AswEAJMZpEhMRKxB/2dsb2JhbACBYrVJgVU Date: Thu, 14 Aug 2008 14:53:38 -0400 From: Mathieu Desnoyers To: "H. Peter Anvin" Cc: Jeremy Fitzhardinge , Andi Kleen , Linus Torvalds , Ingo Molnar , Steven Rostedt , Steven Rostedt , LKML , Thomas Gleixner , Peter Zijlstra , Andrew Morton , David Miller , Roland McGrath , Ulrich Drepper , Rusty Russell , Gregory Haskins , Arnaldo Carvalho de Melo , "Luis Claudio R. Goncalves" , Clark Williams , Christoph Lameter Subject: Re: [RFC PATCH] x86 alternatives : fix LOCK_PREFIX race with preemptible kernel and CPU hotplug Message-ID: <20080814185338.GB7896@Krystal> References: <48A388CE.2020404@goop.org> <20080814014944.GA31883@Krystal> <48A3A806.8060509@goop.org> <20080814151805.GA29507@Krystal> <48A459B1.2070601@zytor.com> <20080814165802.GC517@Krystal> <48A465F2.8000701@goop.org> <20080814173021.GA4697@Krystal> <48A46EC2.1010301@goop.org> <48A47B83.3090408@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <48A47B83.3090408@zytor.com> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 14:52:58 up 70 days, 23:33, 7 users, load average: 3.80, 1.82, 1.12 User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1307 Lines: 32 * H. Peter Anvin (hpa@zytor.com) wrote: > Jeremy Fitzhardinge wrote: >> Ah, OK. I'd thought we started unlocked, but given that I've just been >> disassembling the kernel and looking at the lock prefixes, that's a bit of >> a braino on my part. >> BTW, using the ds prefix allows us to undo the hack of dealing with locked >> instructions with exception handlers. There was a bug where if we do >> lock->nop, then the address of a faulting instruction changes, so we need >> exception records for both the locked and unlocked forms. Using ds means >> the instruction size doesn't change, so we only need one exception record. >> I don't remember off hand where that happens. > > Using %ds: rather than nop really seems to solve a whole lot of problems, > and might even be faster to boot. It really sounds like a no-brainer. > > -hpa So should I wait a bit for more comments or straightforwardly submit this as a patch rather than RFC ? Mathieu -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- 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/