From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752931Ab2LDPRp (ORCPT ); Tue, 4 Dec 2012 10:17:45 -0500 Received: from mail-pa0-f46.google.com ([209.85.220.46]:50922 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751723Ab2LDPRn (ORCPT ); Tue, 4 Dec 2012 10:17:43 -0500 Date: Tue, 4 Dec 2012 07:17:34 -0800 From: Tejun Heo To: "Srivatsa S. Bhat" Cc: tglx@linutronix.de, peterz@infradead.org, paulmck@linux.vnet.ibm.com, rusty@rustcorp.com.au, mingo@kernel.org, akpm@linux-foundation.org, namhyung@kernel.org, vincent.guittot@linaro.org, sbw@mit.edu, amit.kucheria@linaro.org, rostedt@goodmis.org, rjw@sisk.pl, wangyun@linux.vnet.ibm.com, xiaoguangrong@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 01/10] CPU hotplug: Introduce "stable" cpu online mask, for atomic hotplug readers Message-ID: <20121204151734.GB3885@mtj.dyndns.org> References: <20121204085149.25919.29920.stgit@srivatsabhat.in.ibm.com> <20121204085324.25919.53090.stgit@srivatsabhat.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121204085324.25919.53090.stgit@srivatsabhat.in.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 Hello, Srivatsa. On Tue, Dec 04, 2012 at 02:23:41PM +0530, Srivatsa S. Bhat wrote: > extern const struct cpumask *const cpu_possible_mask; > extern const struct cpumask *const cpu_online_mask; > +extern const struct cpumask *const cpu_online_stable_mask; > extern const struct cpumask *const cpu_present_mask; > extern const struct cpumask *const cpu_active_mask; This is a bit nasty. The distinction between cpu_online_mask and the stable one is quite subtle and there's no mechanism to verify the right one is in use. IIUC, the only time cpu_online_mask and cpu_online_stable_mask can deviate is during the final stage CPU take down, right? If so, why not just make cpu_online_mask the stable one and the few cases where the actual online state matters deal with the internal version? Anyone outside cpu hotplug proper should be happy with the stable version anyway, no? Thanks. -- tejun