Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758122AbZKSACJ (ORCPT ); Wed, 18 Nov 2009 19:02:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756827AbZKSACI (ORCPT ); Wed, 18 Nov 2009 19:02:08 -0500 Received: from e4.ny.us.ibm.com ([32.97.182.144]:45142 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756687AbZKSACH (ORCPT ); Wed, 18 Nov 2009 19:02:07 -0500 Date: Wed, 18 Nov 2009 16:02:13 -0800 From: "Paul E. McKenney" To: Mathieu Desnoyers Cc: Jason Baron , linux-kernel@vger.kernel.org, mingo@elte.hu, hpa@zytor.com, tglx@linutronix.de, rostedt@goodmis.org, andi@firstfloor.org, roland@redhat.com, rth@redhat.com, mhiramat@redhat.com Subject: Re: [PATCH] notifier atomic call chain notrace Message-ID: <20091119000213.GE6683@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <14acd28665b633909f7e9873861075fd657e9a52.1258580048.git.jbaron@redhat.com> <20091118233815.GA28962@Krystal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091118233815.GA28962@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 Content-Length: 2799 Lines: 72 On Wed, Nov 18, 2009 at 06:38:15PM -0500, Mathieu Desnoyers wrote: > * Jason Baron (jbaron@redhat.com) wrote: > > Note that this is conditional on gcc >= 4.5. Also there is a !lockdep > > condition. This is b/c the die_notifier takes an rcu_read_lock() on the > > int3 trap, which then causes another one etc. Since, we aren't going to be > > installing removing the handler, the rcu_read_lock() could be avoided for this > > case with some code restructuring. > > > [snip] > > Would the following patch help ? I use it in the LTTng tree to alleviate > this problem. > > > notifier atomic call chain notrace > > In LTTng, being able to use the atomic notifier from cpu idle entry to > ensure the tracer flush the last events in the current subbuffer > requires the rcu read-side to be marked "notrace", otherwise it can end > up calling back into lockdep and the tracer. > > Also apply to the the die notifier. Reviewed-by: Paul E. McKenney > Signed-off-by: Mathieu Desnoyers > CC: "Paul E. McKenney" > CC: Jason Baron > CC: mingo@elte.hu > --- > kernel/notifier.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > Index: linux-2.6-lttng/kernel/notifier.c > =================================================================== > --- linux-2.6-lttng.orig/kernel/notifier.c 2009-11-12 17:58:56.000000000 -0500 > +++ linux-2.6-lttng/kernel/notifier.c 2009-11-12 18:03:28.000000000 -0500 > @@ -148,7 +148,7 @@ int atomic_notifier_chain_unregister(str > spin_lock_irqsave(&nh->lock, flags); > ret = notifier_chain_unregister(&nh->head, n); > spin_unlock_irqrestore(&nh->lock, flags); > - synchronize_rcu(); > + synchronize_sched(); > return ret; > } > EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister); > @@ -178,9 +178,9 @@ int __kprobes __atomic_notifier_call_cha > { > int ret; > > - rcu_read_lock(); > + rcu_read_lock_sched_notrace(); > ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls); > - rcu_read_unlock(); > + rcu_read_unlock_sched_notrace(); > return ret; > } > EXPORT_SYMBOL_GPL(__atomic_notifier_call_chain); > > -- > Mathieu Desnoyers > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/