From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933760Ab3GPS1m (ORCPT ); Tue, 16 Jul 2013 14:27:42 -0400 Received: from mga02.intel.com ([134.134.136.20]:59381 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932958Ab3GPS1l (ORCPT ); Tue, 16 Jul 2013 14:27:41 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.89,678,1367996400"; d="scan'208";a="346578162" Message-ID: <51E5921E.6060702@linux.intel.com> Date: Tue, 16 Jul 2013 11:34:06 -0700 From: Srinivas Pandruvada User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 MIME-Version: 1.0 To: Steven Rostedt CC: LKML , Zhang Rui , Andrew Morton , Tejun Heo Subject: Re: [PATCH] Thermal: Fix lockup of cpu_down() References: <1373997748.6458.26.camel@gandalf.local.home> In-Reply-To: <1373997748.6458.26.camel@gandalf.local.home> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/16/2013 11:02 AM, Steven Rostedt wrote: > Commit f1a18a105 "Thermal: CPU Package temperature thermal" had code > that did a get_online_cpus(), run a loop and then do a > put_online_cpus(). The problem is that the loop had an error exit that > would skip the put_online_cpus() part. > > In the error exit part of the function, it also did a get_online_cpus(), > run a loop and then put_online_cpus(). The only way to get to the error > exit part is with get_online_cpus() already performed. If this error > condition is hit, the system will be prevented from taking CPUs offline. > The process taking the CPU offline will lock up hard. > > Removing the get_online_cpus() removes the lockup as the hotplug CPU > refcount is back to zero. > > This was bisected with ktest. > > Signed-off-by: Steven Rostedt > > diff --git a/drivers/thermal/x86_pkg_temp_thermal.c b/drivers/thermal/x86_pkg_temp_thermal.c > index 5de56f6..d47624c 100644 > --- a/drivers/thermal/x86_pkg_temp_thermal.c > +++ b/drivers/thermal/x86_pkg_temp_thermal.c > @@ -592,7 +592,6 @@ static int __init pkg_temp_thermal_init(void) > return 0; > > err_ret: > - get_online_cpus(); > for_each_online_cpu(i) > put_core_offline(i); > put_online_cpus(); > Agreed. >