From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762077AbZBYRTA (ORCPT ); Wed, 25 Feb 2009 12:19:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761472AbZBYRSs (ORCPT ); Wed, 25 Feb 2009 12:18:48 -0500 Received: from ns1.suse.de ([195.135.220.2]:57053 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755499AbZBYRSr (ORCPT ); Wed, 25 Feb 2009 12:18:47 -0500 Date: Wed, 25 Feb 2009 18:18:42 +0100 From: Nick Piggin To: "Paul E. McKenney" Cc: Ingo Molnar , linux-kernel@vger.kernel.org, vegard.nossum@gmail.com, stable@kernel.org, akpm@linux-foundation.org, penberg@cs.helsinki.fi Subject: Re: [PATCH] v4 Teach RCU that idle task is not quiscent state at boot Message-ID: <20090225171842.GN22785@wotan.suse.de> References: <20090223161611.GA9563@linux.vnet.ibm.com> <20090223204332.GA19861@linux.vnet.ibm.com> <20090225002937.GA23733@linux.vnet.ibm.com> <20090225141945.GA28455@linux.vnet.ibm.com> <20090225160024.GB12732@elte.hu> <20090225162645.GJ22785@wotan.suse.de> <20090225171249.GD6797@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090225171249.GD6797@linux.vnet.ibm.com> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 25, 2009 at 09:12:49AM -0800, Paul E. McKenney wrote: > On Wed, Feb 25, 2009 at 05:26:45PM +0100, Nick Piggin wrote: > > I wonder if you couldn't leave cpu_rq(cpu)->idle as NULL until right > > up to the point where it actually becomes the "idle" thread? This > > would make idle_cpu() more truthful for all other callers in early > > boot code too. And rcupdate shouldn't need any changes (except the > > num_online_cpus() == 1 shortcut probably remains as a nice opt). > > It looked to me that the idle task initialization was moved early > to allow interrupt handlers to see a more normal environment, but I > could easily be confused here. I think we might be OK. I think interrupt handlers shouldn't care so much about whether the cpu is idle or not (and seeing !idle here would be more accurate anyway).