From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753906Ab2BBBO6 (ORCPT ); Wed, 1 Feb 2012 20:14:58 -0500 Received: from e37.co.us.ibm.com ([32.97.110.158]:34775 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752418Ab2BBBO4 (ORCPT ); Wed, 1 Feb 2012 20:14:56 -0500 Date: Wed, 1 Feb 2012 17:14:47 -0800 From: "Paul E. McKenney" To: Josh Triplett Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, patches@linaro.org Subject: Re: [PATCH RFC idle] Make arm, sh, and x86 stop using RCU when idle Message-ID: <20120202011447.GS2382@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20120202004253.GA10946@linux.vnet.ibm.com> <20120202004828.GC29058@leaf> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120202004828.GC29058@leaf> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12020201-7408-0000-0000-0000025578A3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 01, 2012 at 04:48:29PM -0800, Josh Triplett wrote: > On Wed, Feb 01, 2012 at 04:42:53PM -0800, Paul E. McKenney wrote: > > RCU's shiny new diagnostics (thank you, Frederic!) for using RCU when idle > > located a few problems in arm, sh, and x86. This patch series contains > > alleged fixes for these problems. And they are real problems -- if RCU > > believes that the CPU is idle, it is ignoring it. Which means that the > > idle CPU can say "rcu_read_lock()" all it like, but there will be no > > useful effect. > > Having to put these calls down in every idle driver seems like such an > ugly layering violation. Not that I have a better alternative to > suggest... If you do happen to think of one, I would very much like to hear of it! ;-) Thanx, Paul