From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753672Ab0BIJLc (ORCPT ); Tue, 9 Feb 2010 04:11:32 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46429 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751535Ab0BIJL3 (ORCPT ); Tue, 9 Feb 2010 04:11:29 -0500 Date: Tue, 9 Feb 2010 04:10:41 -0500 From: Amerigo Wang To: linux-kernel@vger.kernel.org Cc: Xiaotian Feng , Benjamin Herrenschmidt , Dave Jones , cpufreq@vger.kernel.org, Amerigo Wang , Prarit Bhargava , Thomas Renninger , akpm@linux-foundation.org, Venkatesh Pallipadi Message-Id: <20100209091408.29971.63921.sendpatchset@localhost.localdomain> Subject: [Patch] cpufreq: fix a deadlock during shutting down Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Benjamin reported that, the machine deadlocks right after printing the following when doing a shutdown: halt/4071 is trying to acquire lock: (s_active){++++.+}, at: [] .sysfs_addrm_finish+0x58/0xc0 but task is already holding lock: (&per_cpu(cpu_policy_rwsem, cpu)){+.+.+.}, at: [] .lock_policy_rwsem_write+0x84/0xf4 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: This is because we are trying to kobject_put() a kobject while we are holding cpu policy rwsem. So just move kobject_put() down after releasing the rwsem. Totally untested. Reported-by: Xiaotian Feng Reported-by: Benjamin Herrenschmidt Signed-off-by: WANG Cong Cc: Dave Jones Cc: Thomas Renninger Cc: Prarit Bhargava Cc: Venkatesh Pallipadi --- diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 67bc2ec..222b35f 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1113,6 +1113,7 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev) unsigned int cpu = sys_dev->id; unsigned long flags; struct cpufreq_policy *data; + struct kobject *kobj; #ifdef CONFIG_SMP struct sys_device *cpu_sys_dev; unsigned int j; @@ -1192,7 +1193,7 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev) if (cpufreq_driver->target) __cpufreq_governor(data, CPUFREQ_GOV_STOP); - kobject_put(&data->kobj); + kobj = &data->kobj; /* we need to make sure that the underlying kobj is actually * not referenced anymore by anybody before we proceed with @@ -1207,6 +1208,7 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev) unlock_policy_rwsem_write(cpu); + kobject_put(kobj); free_cpumask_var(data->related_cpus); free_cpumask_var(data->cpus); kfree(data);