From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757208AbZCOC44 (ORCPT ); Sat, 14 Mar 2009 22:56:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752141AbZCOC4q (ORCPT ); Sat, 14 Mar 2009 22:56:46 -0400 Received: from ozlabs.org ([203.10.76.45]:45978 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750903AbZCOC4p (ORCPT ); Sat, 14 Mar 2009 22:56:45 -0400 From: Rusty Russell To: Ingo Molnar Subject: Re: [PULL] x86 cpumask work Date: Sun, 15 Mar 2009 13:26:33 +1030 User-Agent: KMail/1.11.1 (Linux/2.6.27-11-generic; KDE/4.2.1; i686; ; ) Cc: linux-kernel@vger.kernel.org, x86@kernel.org, Mike Travis References: <200903121453.45163.rusty@rustcorp.com.au> <200903132342.42813.rusty@rustcorp.com.au> <20090313152742.GA11800@elte.hu> In-Reply-To: <20090313152742.GA11800@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200903151326.34114.rusty@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Saturday 14 March 2009 01:57:42 Ingo Molnar wrote: > Note, it might have crashed in a cpu hotplug test i'm conducting > during bootup: > > echo 0 > /sys/devices/system/cpu/cpu1/online Indeed, thanks! Subject: cpumask: fix crash when offlining cpus Impact: Fix cpu offline when CONFIG_MAXSMP=y Changeset bc9b83dd1f66402b870301c3c7117b9c1484abb4 "cpumask: convert c1e_mask in arch/x86/kernel/process.c to cpumask_var_t" contained a bug: c1e_mask is manipulated even if C1E isn't detected (and hence not allocated). This is simply fixed by checking for NULL (which gcc optimizes out anyway of CONFIG_CPUMASK_OFFSTACK=n, since it knows ce1_mask can never be NULL). In addition, fix a leak where select_idle_routine re-allocates (and re-clears) c1e_mask on every cpu init. Reported-by: Ingo Molnar Signed-off-by: Rusty Russell diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index cad5431..91a8c26 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -479,7 +479,8 @@ static int c1e_detected; void c1e_remove_cpu(int cpu) { - cpumask_clear_cpu(cpu, c1e_mask); + if (c1e_mask != NULL) + cpumask_clear_cpu(cpu, c1e_mask); } /* @@ -556,8 +557,11 @@ void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c) pm_idle = mwait_idle; } else if (check_c1e_idle(c)) { printk(KERN_INFO "using C1E aware idle routine\n"); - alloc_cpumask_var(&c1e_mask, GFP_KERNEL); - cpumask_clear(c1e_mask); + /* c1e_mask can only be NULL during boot of first cpu. */ + if (c1e_mask == NULL) { + alloc_cpumask_var(&c1e_mask, GFP_KERNEL); + cpumask_clear(c1e_mask); + } pm_idle = c1e_idle; } else pm_idle = default_idle;