From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: Soft-Lockup/Race in networking in 2.6.31-rc1+195 ( possibly?caused by netem) Date: Fri, 03 Jul 2009 18:55:53 -0700 (PDT) Message-ID: <20090703.185553.218218176.davem@davemloft.net> References: <20090703120301.GD4847@ff.dom.local> <20090703.132220.57384838.davem@davemloft.net> <20090703225640.GA3639@ami.dom.local> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: andres@anarazel.de, arun@linux.vnet.ibm.com, tglx@linutronix.de, shemminger@vyatta.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: jarkao2@gmail.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:37870 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754553AbZGDBzr (ORCPT ); Fri, 3 Jul 2009 21:55:47 -0400 In-Reply-To: <20090703225640.GA3639@ami.dom.local> Sender: netdev-owner@vger.kernel.org List-ID: From: Jarek Poplawski Date: Sat, 4 Jul 2009 00:56:40 +0200 > On Fri, Jul 03, 2009 at 01:22:20PM -0700, David Miller wrote: >> Well, if you look at that commit the bisect pointed to Jarek, it is a >> change which starts causing a situation which never happened before. >> Namely, timers added on one cpu can be migrated and fire on another. >> >> So this could be exposing races in the networking that technically >> always existed. > > I'm not sure I get your point; could you give some example? > Actually, I've suspected races in timers code. Let's say that a particular networking timer always gets re-added on the cpu where the timer fires. In that case, beforehand, no inter-cpu races could possibly be tested. But with the new timer code, such races could now be potentially triggered.