From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755404AbZHYRLp (ORCPT ); Tue, 25 Aug 2009 13:11:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755331AbZHYRLo (ORCPT ); Tue, 25 Aug 2009 13:11:44 -0400 Received: from e3.ny.us.ibm.com ([32.97.182.143]:60330 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755329AbZHYRLn (ORCPT ); Tue, 25 Aug 2009 13:11:43 -0400 Date: Tue, 25 Aug 2009 10:11:36 -0700 From: "Paul E. McKenney" To: Mathieu Desnoyers Cc: Ingo Molnar , Lai Jiangshan , linux-kernel@vger.kernel.org, dipankar@in.ibm.com, akpm@linux-foundation.org, josht@linux.vnet.ibm.com, dvhltc@us.ibm.com, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Paul Mundt Subject: Re: [PATCH -tip 0/2] Temporary RCU fixes for notrace and hotplug CPU Message-ID: <20090825171136.GG6616@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20090824164112.GA13693@linux.vnet.ibm.com> <20090825065501.GA29162@elte.hu> <20090825080047.GA16139@elte.hu> <20090825161208.GE6616@linux.vnet.ibm.com> <20090825162549.GB25058@Krystal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090825162549.GB25058@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, Aug 25, 2009 at 12:25:49PM -0400, Mathieu Desnoyers wrote: > * Paul E. McKenney (paulmck@linux.vnet.ibm.com) wrote: > > On Tue, Aug 25, 2009 at 10:00:47AM +0200, Ingo Molnar wrote: > > > > > > btw., i'm still seeing crashes with the latest RCU bits: > > > > > > [ 20.621740] Testing event sys_enter_futex: OK > > > [ 20.629738] Testing event sys_exit_futex: OK > > > [ 20.637737] Testing event lock_acquire: [reboot] > > > > > > Possibly due to infinite recursion as well. Config attached. > > > > Color me confused... > > > > Unless someone has a better idea, I will send in a patch that adds > > "notrace" to every RCU API member used by any file in the kernel > > that has "trace" in its name (excluding ptrace.c and rcutree_trace.c, > > of course). This list is as follows: > > > > call_rcu() > > call_rcu_sched() > > rcu_read_lock() > > rcu_read_unlock() > > > > So, any better ideas? > > Tracers using RCU should use the _notrace() version of read_lock/unlock. > I think the callers should be fixed rather than RCU. > > Tracepoints have been designed to use the _notrace variant on the > instrumentation site. The core of tracepoint management use > call_rcu_sched(), which can be traced without any problem. > > I have not followed the late tracing development as closely though, so > errors might have crept in. Or I might have inadvertently broken something in a non-obvious (to me, anyway) manner. So, would you be willing to look at commit bc33f24bd in the -tip tree and see if there is anything I broke other than the now-fixed rcu_read_lock_sched_notrace() and rcu_read_unlock_sched_notrace()? And for that matter, whether my alleged fix for these two API members really does fix the problem (-tip commit 7c614d6461)? The -tip tree is at: git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git And these patches are on the tip/core/rcu branch. Thanx, Paul