From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759542AbZBYEoQ (ORCPT ); Tue, 24 Feb 2009 23:44:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755563AbZBYEoA (ORCPT ); Tue, 24 Feb 2009 23:44:00 -0500 Received: from e4.ny.us.ibm.com ([32.97.182.144]:55170 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755537AbZBYEoA (ORCPT ); Tue, 24 Feb 2009 23:44:00 -0500 Date: Tue, 24 Feb 2009 20:43:56 -0800 From: "Paul E. McKenney" To: Nick Piggin Cc: linux-kernel@vger.kernel.org, vegard.nossum@gmail.com, mingo@elte.hu, stable@kernel.org, akpm@linux-foundation.org, penberg@cs.helsinki.fi Subject: Re: [PATCH] v3 Teach RCU that idle task is not quiscent state at boot Message-ID: <20090225044356.GD7241@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20090223161611.GA9563@linux.vnet.ibm.com> <20090223204332.GA19861@linux.vnet.ibm.com> <20090225002937.GA23733@linux.vnet.ibm.com> <20090225041259.GA14149@wotan.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090225041259.GA14149@wotan.suse.de> 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 On Wed, Feb 25, 2009 at 05:12:59AM +0100, Nick Piggin wrote: > Looks OK to me. It's a bit "theoretically" displeasing that > you still treat synchronize_rcu as a gp even after we spawn > some kernel threads. > > ... but it probably isn't worth trying to rearrange the boot > code just to make this look better. I can't see any actual > problems that could arise, as the threads should not have > had a chance to run yet. And if rcuclassic or rcutree on a UP system, even if threads have had a chance to run, it is OK to treat synchronize_rcu() as a grace period, since it has the opportunity to block. > I wonder if you couldn't put in a WARN_ON(nr_context_switches() > 0) > in rcu_idle_now_means_idle() just in case? Makes a lot of sense -- updated and am firing off the tests! Thanx, Paul > On Tue, Feb 24, 2009 at 04:29:37PM -0800, Paul E. McKenney wrote: > > This patch fixes a bug located by Vegard Nossum with the aid of > > kmemcheck, updated based on review comments from Nick Piggin, > > Ingo Molnar, and Andrew Morton.