From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759040AbZJGMiO (ORCPT ); Wed, 7 Oct 2009 08:38:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758924AbZJGMiO (ORCPT ); Wed, 7 Oct 2009 08:38:14 -0400 Received: from bc.sympatico.ca ([209.226.175.184]:50980 "EHLO tomts22-srv.bellnexxia.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754341AbZJGMiN (ORCPT ); Wed, 7 Oct 2009 08:38:13 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AlMFAOIjzEpMROOX/2dsb2JhbACBUdNQhCoE Date: Wed, 7 Oct 2009 08:36:59 -0400 From: Mathieu Desnoyers To: "Paul E. McKenney" Cc: akpm@linux-foundation.org, Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [patch 0/4] DEBUG_RCU_HEAD: Debug and fix racy call_rcu() users Message-ID: <20091007123658.GA27363@Krystal> References: <20091006143727.868480435@polymtl.ca> <20091007042054.GE6838@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <20091007042054.GE6838@linux.vnet.ibm.com> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.27.31-grsec (i686) X-Uptime: 08:31:03 up 49 days, 23:20, 2 users, load average: 0.27, 0.23, 0.22 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Paul E. McKenney (paulmck@linux.vnet.ibm.com) wrote: > On Tue, Oct 06, 2009 at 10:37:28AM -0400, Mathieu Desnoyers wrote: > > Here is a patchset, done on 2.6.30.9, which permits to detect and fix racy > > call_rcu() users. > > > > Fix for vunmap, which happens to be one of them, is included. > > > > Note that some false-positives might come up when call_rcu() is called on > > uninitialized struct rcu_head. The solution is, surprisingly enough, to > > initialize them. > > Very cool, Mathieu!!! > > I do like adding the debug-only field to struct rcu_head. Lots of > additional places need initialization, or am I missing a trick here? > In my case, only 2 sites in the process management and 1 site in the now deprecated marker.c complained about not being initialized. I can guess we will find others though. Please see the v2 of my patch, which adds the supplementary "debug" field rather than depending on word-aligned pointers. I volountarily complain about the .debug pointer being non-NULL when we find an uninitialized site. I could be more specific and complain "differently" if the pointer happens to be random vs if it's LIST_POISON1. Thanks, Mathieu > Thanx, Paul -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68