Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755527AbYBSKpl (ORCPT ); Tue, 19 Feb 2008 05:45:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751578AbYBSKpd (ORCPT ); Tue, 19 Feb 2008 05:45:33 -0500 Received: from rv-out-0910.google.com ([209.85.198.185]:46603 "EHLO rv-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751044AbYBSKpc (ORCPT ); Tue, 19 Feb 2008 05:45:32 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references:x-google-sender-auth; b=PhtFXf0v3YEx3Y2AJRfmRi1MnBpaV+7gsV9iZqUVLD9L21sJHpJo5EV4jZ/2XMY1hADJGZAQMlAaWLuAtLJzv3H0HxOeY79+NWSuNdT8hMBzqEXpC6pqJeaUtVoQzPIARkAeNKVV+uFvzDbwgvppmyGBsv6/N6lY1/1WgoT8jvY= Message-ID: <84144f020802190245p7c2a52f2r72f273d37cb001f9@mail.gmail.com> Date: Tue, 19 Feb 2008 12:45:29 +0200 From: "Pekka Enberg" To: "Ingo Molnar" Subject: Re: Linux 2.6.25-rc2 Cc: "Torsten Kaiser" , "Linus Torvalds" , "Linux Kernel Mailing List" , "Mathieu Desnoyers" , "Christoph Lameter" In-Reply-To: <20080219102700.GC14092@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <64bb37e0802161338j306c1357m25bc224f09e6b7cd@mail.gmail.com> <20080219061107.GA23229@elte.hu> <64bb37e0802182254l49b10cbblc23f8a83d189ff8e@mail.gmail.com> <84144f020802182321x452888bai639c71ea2a5067da@mail.gmail.com> <20080219102700.GC14092@elte.hu> X-Google-Sender-Auth: e8a840cc054ba253 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1897 Lines: 45 Hi, Pekka Enberg wrote: > > Mathieu, Christoph is on vacation and I'm not at all that familiar > > with this cmpxchg_local() optimization, so if you could take a peek at > > this bug report to see if you can spot something obviously wrong with > > it, I would much appreciate that. On Feb 19, 2008 12:27 PM, Ingo Molnar wrote: > hm, it's bad for at least one other reason as well (which is probably > unrelated to this crash): > > /* > * Currently fastpath is not supported if preemption is enabled. > */ > #if defined(CONFIG_FAST_CMPXCHG_LOCAL) && !defined(CONFIG_PREEMPT) > #define SLUB_FASTPATH > #endif > > such !PREEMPT exceptions tend to show "i didnt want to think too hard > about the preemptible case so just turn it off" thinking. > > Also, why isnt this "SLUB_FASTPATH" flag done in the Kconfig space? Hmm, no idea. I think might have been some mix-up with merging the patch. The one I saw was: http://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.24/2.6.24-mm1/broken-out/slub-optional-fast-path-using-cmpxchg_local.patch But I don't remember giving out a Reviewed-by for it (and my mailbox confirms that). Furthermore, somehow it turned into this when merged: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=1f84260c8ce3b1ce26d4c1d6dedc2f33a3a29c0c In any case, if Torsten/someone can verify that reverting 1f84260c8ce3b1ce26d4c1d6dedc2f33a3a29c0c ("SLUB: Alternate fast paths using cmpxchg_local") fixes these problems, I think we should just do it and let Christoph sort it out when he gets back. Pekka -- 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/