From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751703Ab1GTUdV (ORCPT ); Wed, 20 Jul 2011 16:33:21 -0400 Received: from e9.ny.us.ibm.com ([32.97.182.139]:45674 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751311Ab1GTUdU (ORCPT ); Wed, 20 Jul 2011 16:33:20 -0400 Date: Wed, 20 Jul 2011 13:33:00 -0700 From: "Paul E. McKenney" To: Ingo Molnar Cc: Linus Torvalds , Peter Zijlstra , Ben Greear , Ed Tomlinson , linux-kernel@vger.kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, patches@linaro.org, edward.tomlinson@aero.bombardier.com Subject: Re: [PATCH rcu/urgent 0/6] Fixes for RCU/scheduler/irq-threads trainwreck Message-ID: <20110720203300.GQ2313@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20110720133443.GG2400@linux.vnet.ibm.com> <4E270A0E.6090902@candelatech.com> <20110720171532.GB2313@linux.vnet.ibm.com> <20110720184413.GD17977@elte.hu> <1311187978.29152.58.camel@twins> <20110720192949.GM2313@linux.vnet.ibm.com> <20110720193925.GB7910@elte.hu> <20110720195742.GA14671@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110720195742.GA14671@elte.hu> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 20, 2011 at 09:57:42PM +0200, Ingo Molnar wrote: > > * Ingo Molnar wrote: > > > > > * Paul E. McKenney wrote: > > > > > If my guess is correct, then the minimal non-RCU_BOOST fix is #4 > > > (which drags along #3) and #6. Which are not one-liners, but > > > somewhat smaller: > > > > > > b/kernel/rcutree_plugin.h | 12 ++++++------ > > > b/kernel/softirq.c | 12 ++++++++++-- > > > kernel/rcutree_plugin.h | 31 +++++++++++++++++++++++++------ > > > 3 files changed, 41 insertions(+), 14 deletions(-) > > > > That's half the patch size and half the patch count. > > > > PeterZ's question is relevant: since we apparently had similar bugs > > in v2.6.39 as well, what changed in v3.0 that makes them so urgent > > to fix? > > > > If it's just better instrumentation that proves them better then > > i'd suggest fixing this in v3.1 and not risking v3.0 with an > > unintended side effect. > > Ok, i looked some more at the background and the symptoms that people > are seeing: kernel crashes and lockups. I think we want these > problems fixed in v3.0, even if it was the recent introduction of > RCU_BOOST that made it really prominent. > > Having put some testing into your rcu/urgent branch today i'd feel > more comfortable with taking this plus perhaps an RCU_BOOST disabling > patch. That makes it all fundamentally tested by a number of people > (including those who reported/reproduced the problems). RCU_BOOST is currently default=n. Is that sufficient? If not, one low-risk approach would be for me to just remove RCU_BOOST from init/Kconfig in 3.0 and add it back in for 3.1. Please let me know what works best. Thanx, Paul > Linus, would that approach be fine with you? I'll send an RFC pull > request for the 6 patches as a reply to this mail, in a couple of > minutes. > > Thanks, > > Ingo > -- > 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/