From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752825Ab3LRLqt (ORCPT ); Wed, 18 Dec 2013 06:46:49 -0500 Received: from merlin.infradead.org ([205.233.59.134]:44272 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751258Ab3LRLqs (ORCPT ); Wed, 18 Dec 2013 06:46:48 -0500 Date: Wed, 18 Dec 2013 12:46:33 +0100 From: Peter Zijlstra To: Frederic Weisbecker Cc: "Paul E. McKenney" , LKML , Thomas Gleixner , Ingo Molnar , Steven Rostedt , John Stultz , Alex Shi , Kevin Hilman Subject: Re: [PATCH 03/13] rcu: Exclude all potential timekeepers from sysidle detection Message-ID: <20131218114633.GR3694@twins.programming.kicks-ass.net> References: <1387320692-28460-1-git-send-email-fweisbec@gmail.com> <1387320692-28460-4-git-send-email-fweisbec@gmail.com> <20131217232714.GD19211@linux.vnet.ibm.com> <20131217234913.GB18689@localhost.localdomain> <20131218114318.GR13532@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131218114318.GR13532@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 18, 2013 at 12:43:18PM +0100, Peter Zijlstra wrote: > On Wed, Dec 18, 2013 at 12:49:15AM +0100, Frederic Weisbecker wrote: > > That's to start simple as CPU 0 can't be offlined. > > Yes it can, see CONFIG_BOOTPARAM_HOTPLUG_CPU0 Also, that's a traditional weirdness of x86. Other archs might not have this constraint at all and can hotplug any cpu. So relying on the fact that cpu 0 cannot be hotplugged is broken.