From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id CC7D36B003D for ; Thu, 26 Mar 2009 03:01:18 -0400 (EDT) Received: from d28relay02.in.ibm.com (d28relay02.in.ibm.com [9.184.220.59]) by e28smtp04.in.ibm.com (8.13.1/8.13.1) with ESMTP id n2Q7pLe3032125 for ; Thu, 26 Mar 2009 13:21:21 +0530 Received: from d28av05.in.ibm.com (d28av05.in.ibm.com [9.184.220.67]) by d28relay02.in.ibm.com (8.13.8/8.13.8/NCO v9.2) with ESMTP id n2Q7lmqf4222982 for ; Thu, 26 Mar 2009 13:17:49 +0530 Received: from d28av05.in.ibm.com (loopback [127.0.0.1]) by d28av05.in.ibm.com (8.13.1/8.13.3) with ESMTP id n2Q7pKPB005693 for ; Thu, 26 Mar 2009 18:51:20 +1100 Date: Thu, 26 Mar 2009 13:21:01 +0530 From: Balbir Singh Subject: Re: [PATCH} - There appears to be a minor race condition in sched.c Message-ID: <20090326075101.GE24227@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <49CAFA83.1000005@tensilica.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <49CAFA83.1000005@tensilica.com> Sender: owner-linux-mm@kvack.org To: Piet Delaney Cc: Ingo Molnar , Peter Zijlstra , linux-mm@kvack.org, Johannes Weiner , LKML List-ID: * Piet Delaney [2009-03-25 20:46:11]: > Ingo, Peter: > > There appears to be a minor race condition in sched.c where > you can get a division by zero. I suspect that it only shows > up when the kernel is compiled without optimization and the code > loads rq->nr_running from memory twice. > > It's part of our SMP stabilization changes that I just posted to: > > git://git.kernel.org/pub/scm/linux/kernel/git/piet/xtensa-2.6.27-smp.git > > I mentioned it to Johannes the other day and he suggested passing it on to you ASAP. > The latest version uses ACCESS_ONCE to get rq->nr_running and then uses that value. I am not sure what version you are talking about, if it is older, you should consider backporting from the current version. -- Balbir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org