From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755997AbYJJFmW (ORCPT ); Fri, 10 Oct 2008 01:42:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752636AbYJJFmN (ORCPT ); Fri, 10 Oct 2008 01:42:13 -0400 Received: from tomts13.bellnexxia.net ([209.226.175.34]:42289 "EHLO tomts13-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752580AbYJJFmM (ORCPT ); Fri, 10 Oct 2008 01:42:12 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AsAEAEOI7khMQWq+/2dsb2JhbACBcrwbgWo Date: Fri, 10 Oct 2008 01:42:10 -0400 From: Mathieu Desnoyers To: Lai Jiangshan Cc: Ingo Molnar , Linux Kernel Mailing List Subject: Re: [PATCH] markers: bit-field is not thread-safe nor smp-safe Message-ID: <20081010054210.GA19481@Krystal> References: <48EEC6AD.4010606@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <48EEC6AD.4010606@cn.fujitsu.com> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 01:30:24 up 127 days, 10:10, 9 users, load average: 0.33, 0.41, 0.35 User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Lai Jiangshan (laijs@cn.fujitsu.com) wrote: > > bit-field is not thread-safe nor smp-safe. > > struct marker_entry.rcu_pending is not protected by any lock > in rcu-callback free_old_closure(). > so we must turn it into a safe type. > All struct marker_entry.rcu_pending accesses are done with the markers_mutex held, except the one done in free_old_closure(). Normally, there should be a if (entry->rcu_pending) rcu_barrier_sched(); At the beginning of each markers_mutex section (just after get_marker()) to make sure any pending callback is executed at that point before any of rcu_pending or ptype are touched. I just noticed that the "markers: fix unchecked format" patch has a race with respect to this. I'll post a patch in a jiffy. Mathieu -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68