From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755640AbZHUOSC (ORCPT ); Fri, 21 Aug 2009 10:18:02 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755608AbZHUOSB (ORCPT ); Fri, 21 Aug 2009 10:18:01 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:56576 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755278AbZHUOSA (ORCPT ); Fri, 21 Aug 2009 10:18:00 -0400 Date: Fri, 21 Aug 2009 16:17:21 +0200 From: Ingo Molnar To: Mathieu Desnoyers Cc: "Paul E. McKenney" , Josh Triplett , linux-kernel@vger.kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, dvhltc@us.ibm.com, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, hugh.dickins@tiscali.co.uk, benh@kernel.crashing.org Subject: Re: [PATCH -tip/core/rcu 1/6] Cleanups and fixes for RCU in face of heavy CPU-hotplug stress Message-ID: <20090821141721.GA11098@elte.hu> References: <20090815165153.GA8886@linux.vnet.ibm.com> <1250533487.2709.14.camel@josh-work.beaverton.ibm.com> <20090817192036.GJ6760@linux.vnet.ibm.com> <20090818152643.GA5549@elte.hu> <20090820140335.GA31773@Krystal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090820140335.GA31773@Krystal> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Mathieu Desnoyers wrote: > I would not trust this architecture for synchronization tests. > There has been reports of a hardware bug affecting the cmpxchg > instruction in the field. The load fence normally implied by the > semantic seems to be missing. AFAIK, AMD never acknowledged the > problem. If cmpxchg was broken i'd be having far worse problems and very widely so. FYI, this was the same box i prototyped/developed -rt on, which uses cmpxchg for _everything_. That's not a proof of course (it's near impossible to prove the lack of a bug), but it's sure a strong indicator and you'll need to provide far more proof of misbehavior before i discount a bona fide regression on this box. Ingo