From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754006Ab1HSSB6 (ORCPT ); Fri, 19 Aug 2011 14:01:58 -0400 Received: from out2.smtp.messagingengine.com ([66.111.4.26]:41644 "EHLO out2.smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751685Ab1HSSB5 (ORCPT ); Fri, 19 Aug 2011 14:01:57 -0400 X-Sasl-enc: eeIhw04zy4G9opuUI5vR1fSSkII7TstOyu/X5jXYsd1s 1313776914 Date: Fri, 19 Aug 2011 11:01:37 -0700 From: Greg KH To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mathieu.desnoyers@polymtl.ca, laijs@cn.fujitsu.com, eric.dumazet@gmail.com, patches@linaro.org, peterz@infradead.org, josh@joshtriplett.org, rostedt@goodmis.org, stable@kernel.org, dhowells@redhat.com, darren@dvhart.com, niv@us.ibm.com, tglx@linutronix.de, dipankar@in.ibm.com, Valdis.Kletnieks@vt.edu, mingo@elte.hu, akpm@linux-foundation.org Subject: Re: [stable] [PATCH RFC tip/core/urgent] rcu: Avoid having just-onlined CPU resched itself when RCU is idle Message-ID: <20110819180137.GA22040@kroah.com> References: <20110819163547.GA5182@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110819163547.GA5182@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 19, 2011 at 09:35:47AM -0700, Paul E. McKenney wrote: > CPUs set rdp->qs_pending when coming online to resolve races with > grace-period start. However, this means that if RCU is idle, the > just-onlined CPU might needlessly send itself resched IPIs. Adjust the > online-CPU initialization to avoid this, and also to correctly cause > the CPU to respond to the current grace period if needed. > > This patch is believed to fix or otherwise suppress problems in > https://bugzilla.redhat.com/show_bug.cgi?id=726877, however, the > relationship is not apparent to this patch's author. That said, it is > hard to argue with test results. > > This will be available from -rcu as soon as kernel.org's mirrors update: > > git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu.git rcu/urgent > > Reported-by: Nicolas Mailhot > Reported-by: Michal Jaegermann > Reported-by: Josh Boyer > Signed-off-by: Paul E. McKenney > Tested-by: Josh Boyer > > rcutree.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read Documentation/stable_kernel_rules.txt for how to do this properly.