From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937858Ab0CPNIS (ORCPT ); Tue, 16 Mar 2010 09:08:18 -0400 Received: from tomts16.bellnexxia.net ([209.226.175.4]:38567 "EHLO tomts16-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932211Ab0CPNIR (ORCPT ); Tue, 16 Mar 2010 09:08:17 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AvsEAMsfn0tGHl03/2dsb2JhbACafXS5P4JYgiQE Date: Tue, 16 Mar 2010 09:08:14 -0400 From: Mathieu Desnoyers To: Lai Jiangshan Cc: Ingo Molnar , "Paul E. McKenney" , LKML Subject: Re: [PATCH -tip] rcu: fix lockdep for tracepoint Message-ID: <20100316130814.GA32375@Krystal> References: <4B9F48AD.4000404@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <4B9F48AD.4000404@cn.fujitsu.com> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.27.31-grsec (i686) X-Uptime: 09:07:16 up 89 days, 21:25, 4 users, load average: 0.25, 0.30, 0.20 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 * Lai Jiangshan (laijs@cn.fujitsu.com) wrote: > tracepoint.h use rcu_dereference(), it triggers this warning: > > [ 0.701161] =================================================== > [ 0.702211] [ INFO: suspicious rcu_dereference_check() usage. ] > [ 0.702716] --------------------------------------------------- > [ 0.703203] include/trace/events/workqueue.h:68 invoked rcu_dereference_check() without protection! > [ 0.703971] > [ 0.703990] other info that might help us debug this: > [ 0.703993] > [ 0.705590] > [ 0.705604] rcu_scheduler_active = 1, debug_locks = 0 > [ 0.706712] 1 lock held by swapper/1: > [ 0.707229] #0: (cpu_add_remove_lock){+.+.+.}, at: [] cpu_maps_update_begin+0x14/0x20 > [ 0.710097] > [ 0.710106] stack backtrace: > [ 0.712602] Pid: 1, comm: swapper Not tainted 2.6.34-rc1-tip-01613-g72662bb #168 > [ 0.713231] Call Trace: > [ 0.713997] [] lockdep_rcu_dereference+0x9d/0xb0 > [ 0.714746] [] create_workqueue_thread+0x107/0x110 > [ 0.715353] [] ? worker_thread+0x0/0x340 > [ 0.715845] [] __create_workqueue_key+0x138/0x240 > [ 0.716427] [] ? cpu_maps_update_done+0x12/0x20 > [ 0.717012] [] init_workqueues+0x6f/0x80 > [ 0.717530] [] kernel_init+0x102/0x1f0 > [ 0.717570] [] ? kernel_init+0x0/0x1f0 > [ 0.718944] [] kernel_thread_helper+0x6/0x10 > > Signed-off-by: Lai Jiangshan Acked-by: Mathieu Desnoyers Thanks Lai, Mathieu > --- > diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h > index f59604e..78b4bd3 100644 > --- a/include/linux/tracepoint.h > +++ b/include/linux/tracepoint.h > @@ -49,7 +49,7 @@ struct tracepoint { > void **it_func; \ > \ > rcu_read_lock_sched_notrace(); \ > - it_func = rcu_dereference((tp)->funcs); \ > + it_func = rcu_dereference_sched((tp)->funcs); \ > if (it_func) { \ > do { \ > ((void(*)(proto))(*it_func))(args); \ > -- Mathieu Desnoyers Operating System Efficiency Consultant EfficiOS Inc. http://www.efficios.com