From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756791Ab2BPBvR (ORCPT ); Wed, 15 Feb 2012 20:51:17 -0500 Received: from ozlabs.org ([203.10.76.45]:56413 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753255Ab2BPBvP (ORCPT ); Wed, 15 Feb 2012 20:51:15 -0500 From: Rusty Russell To: "Srivatsa S. Bhat" Cc: Ralf Baechle , linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, Venkatesh Pallipadi , "akpm\@linux-foundation.org" Subject: Re: [PATCH 4/12] arch/mips: remove references to cpu_*_map. In-Reply-To: <4F3B78C2.7040709@linux.vnet.ibm.com> References: <1329281884.26321.rusty@rustcorp.com.au> <4F3B78C2.7040709@linux.vnet.ibm.com> User-Agent: Notmuch/0.6.1-1 (http://notmuchmail.org) Emacs/23.3.1 (i686-pc-linux-gnu) Date: Thu, 16 Feb 2012 10:29:24 +1030 Message-ID: <87hayrbqcj.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 15 Feb 2012 14:50:02 +0530, "Srivatsa S. Bhat" wrote: > > - cpu_clear(smp_processor_id(), mask); > > - for_each_cpu_mask(cpu, mask) > > - if (cpu_context(cpu, mm)) > > + for_each_online_cpu(cpu) { > > + if (cpu != smp_processor_id() && cpu_context(cpu, mm)) > > cpu_context(cpu, mm) = 0; > > + } > > > Strictly speaking, this one is not a mere cleanup. It causes a subtle change in > behaviour: earlier, it used to iterate over a local copy of cpu_online_mask, which > wouldn't change. However, with this patch, it will iterate directly over > cpu_online_mask, which can change underneath. (The preempt_disable() won't stop > new CPUs from coming in.. it only prevents CPUs from going offline, that too > provided that we use stop_machine stuff for CPU offline, which we do currently.) There's a preempt_disable() around this whole function, so online_mask can't change. Same with the others. > > + mask = *cpu_online_mask; > > + cpumask_clear(&mask, cpu); > > > This should be cpumask_clear_cpu(cpu, &mask); Good catch. I copied the bitmask ops, and continually regret it. I've rolled all these together with your fixes, added your ia64 patch, and am rebasing to -next now, so I can hand this all across to akpm. Thanks, Rusty.