From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753802Ab2BBEzw (ORCPT ); Wed, 1 Feb 2012 23:55:52 -0500 Received: from e39.co.us.ibm.com ([32.97.110.160]:51380 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752420Ab2BBEzu (ORCPT ); Wed, 1 Feb 2012 23:55:50 -0500 Date: Wed, 1 Feb 2012 20:55:38 -0800 From: "Paul E. McKenney" To: Frederic Weisbecker 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, josh@joshtriplett.org, 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, patches@linaro.org, "Paul E. McKenney" , "H. Peter Anvin" , Len Brown , Borislav Petkov , Kamalesh Babulal , Stephen Wilson , linux-pm@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH RFC idle 1/3] x86: Avoid invoking RCU when CPU is idle Message-ID: <20120202045538.GF2435@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20120202004253.GA10946@linux.vnet.ibm.com> <1328143404-11038-1-git-send-email-paulmck@linux.vnet.ibm.com> <20120202015428.GA8807@somewhere.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120202015428.GA8807@somewhere.redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12020204-4242-0000-0000-000000AB5E91 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 02, 2012 at 02:54:30AM +0100, Frederic Weisbecker wrote: > On Wed, Feb 01, 2012 at 04:43:22PM -0800, Paul E. McKenney wrote: > > From: "Paul E. McKenney" > > > > The idle loop is a quiscent state for RCU, which means that RCU ignores > > CPUs that have told RCU that they are idle via rcu_idle_enter(). There > > are nevertheless quite a few places where idle CPUs use RCU, most commonly > > indirectly via tracing. This patch fixes these problems for x86. > > > > Many of these bugs have been in the kernel for quite some time, but > > Frederic's recent change now gives warnings. > > > > This patch takes the straightforward approach of pushing the > > rcu_idle_enter()/rcu_idle_exit() pair further down into the core > > of the idle loop. > > I guess this is about the trace_power_*() things, right? Indeed it is! Alternative suggestions gladly accepted. ;-) Thanx, Paul > Acked-by: Frederic Weisbecker > > Thanks. >