From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966219Ab0CPNbY (ORCPT ); Tue, 16 Mar 2010 09:31:24 -0400 Received: from e1.ny.us.ibm.com ([32.97.182.141]:54333 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965058Ab0CPNbW (ORCPT ); Tue, 16 Mar 2010 09:31:22 -0400 Date: Tue, 16 Mar 2010 06:31:15 -0700 From: "Paul E. McKenney" To: Mathieu Desnoyers Cc: Lai Jiangshan , Ingo Molnar , LKML Subject: Re: [PATCH -tip] rcu: fix lockdep for tracepoint Message-ID: <20100316133115.GE6709@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <4B9F48AD.4000404@cn.fujitsu.com> <20100316130814.GA32375@Krystal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100316130814.GA32375@Krystal> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 16, 2010 at 09:08:14AM -0400, Mathieu Desnoyers wrote: > * 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, Me too! Acked-by: Paul E. McKenney > 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