Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752787AbYFZMSc (ORCPT ); Thu, 26 Jun 2008 08:18:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750830AbYFZMSY (ORCPT ); Thu, 26 Jun 2008 08:18:24 -0400 Received: from E23SMTP04.au.ibm.com ([202.81.18.173]:59067 "EHLO e23smtp04.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750736AbYFZMSX (ORCPT ); Thu, 26 Jun 2008 08:18:23 -0400 Message-ID: <48638906.4090308@linux.vnet.ibm.com> Date: Thu, 26 Jun 2008 17:48:14 +0530 From: Nageswara R Sastry User-Agent: Thunderbird 2.0.0.14 (X11/20080505) MIME-Version: 1.0 To: Johannes Weiner CC: linux-kernel@vger.kernel.org, balbir@linux.vnet.ibm.com, ego@linux.vnet.ibm.com, svaidy@linux.vnet.ibm.com, davej@codemonkey.org.uk Subject: Re: [BUG] While changing the cpufreq governor, kernel hits a bug in workqueue.c References: <485F8028.1070302@linux.vnet.ibm.com> <87y74w41fp.fsf@skyscraper.fehenstaub.lan> <4860BB8E.2070505@linux.vnet.ibm.com> <87tzfh2t5l.fsf@skyscraper.fehenstaub.lan> In-Reply-To: <87tzfh2t5l.fsf@skyscraper.fehenstaub.lan> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7064 Lines: 172 Hi, Johannes Weiner wrote: > From: Johannes Weiner > Subject: cpufreq: cancel self-rearming work synchroneuously > > The ondemand and conservative governor workers are self-rearming. > Cancel them synchroneously to avoid nasty races. > > Reported-by: Nageswara R Sastry > Signed-off-by: Johannes Weiner > --- > > diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c > index 5d3a04b..78bac06 100644 > --- a/drivers/cpufreq/cpufreq_conservative.c > +++ b/drivers/cpufreq/cpufreq_conservative.c > @@ -467,7 +467,7 @@ static inline void dbs_timer_init(void) > > static inline void dbs_timer_exit(void) > { > - cancel_delayed_work(&dbs_work); > + cancel_delayed_work_sync(&dbs_work); > return; > } > > diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c > index d2af20d..1eb8c58 100644 > --- a/drivers/cpufreq/cpufreq_ondemand.c > +++ b/drivers/cpufreq/cpufreq_ondemand.c > @@ -490,7 +490,7 @@ static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info) > static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info) > { > dbs_info->enable = 0; > - cancel_delayed_work(&dbs_info->work); > + cancel_delayed_work_sync(&dbs_info->work); > } > > static int cpufreq_governor_dbs(struct cpufreq_policy *policy, Applied the above patch only and compiled the kernel and seeing an Circular lock related issue at the time of booting. First I am checking this and will let you the results by applying both the patches. ======================================================= [ INFO: possible circular locking dependency detected ] 2.6.25.7.cpufreq_patch #2 ------------------------------------------------------- S06cpuspeed/3493 is trying to acquire lock: (&(&dbs_info->work)->work){--..}, at: [] __cancel_work_timer+0x80/0x177 but task is already holding lock: (dbs_mutex){--..}, at: [] cpufreq_governor_dbs+0x25e/0x2ed which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (dbs_mutex){--..}: [] add_lock_to_list+0x61/0x83 [] __lock_acquire+0x953/0xb05 [] cpufreq_governor_dbs+0x74/0x2ed [] lock_acquire+0x5f/0x79 [] cpufreq_governor_dbs+0x74/0x2ed [] mutex_lock_nested+0xce/0x222 [] cpufreq_governor_dbs+0x74/0x2ed [] cpufreq_governor_dbs+0x74/0x2ed [] cpufreq_governor_dbs+0x74/0x2ed [] __cpufreq_governor+0x73/0xa6 [] __cpufreq_set_policy+0x13b/0x19e [] cpufreq_add_dev+0x3b4/0x4aa [] handle_update+0x0/0x21 [] sysdev_driver_register+0x48/0x9a [] cpufreq_register_driver+0x9b/0x147 [] kernel_init+0x130/0x26f [] kernel_init+0x0/0x26f [] kernel_init+0x0/0x26f [] kernel_thread_helper+0x7/0x10 [] 0xffffffff -> #1 (&per_cpu(cpu_policy_rwsem, cpu)){----}: [] __lock_acquire+0x953/0xb05 [] lock_policy_rwsem_write+0x30/0x56 [] save_stack_trace+0x1a/0x35 [] lock_acquire+0x5f/0x79 [] lock_policy_rwsem_write+0x30/0x56 [] down_write+0x2b/0x44 [] lock_policy_rwsem_write+0x30/0x56 [] lock_policy_rwsem_write+0x30/0x56 [] do_dbs_timer+0x40/0x24f [] run_workqueue+0x81/0x187 [] run_workqueue+0xbc/0x187 [] run_workqueue+0x81/0x187 [] do_dbs_timer+0x0/0x24f [] worker_thread+0x0/0xbd [] worker_thread+0xb3/0xbd [] autoremove_wake_function+0x0/0x2d [] kthread+0x38/0x5d [] kthread+0x0/0x5d [] kernel_thread_helper+0x7/0x10 [] 0xffffffff -> #0 (&(&dbs_info->work)->work){--..}: [] print_circular_bug_tail+0x2a/0x61 [] __lock_acquire+0x878/0xb05 [] lock_acquire+0x5f/0x79 [] __cancel_work_timer+0x80/0x177 [] __cancel_work_timer+0xab/0x177 [] __cancel_work_timer+0x80/0x177 [] mark_held_locks+0x39/0x53 [] mutex_lock_nested+0x20f/0x222 [] trace_hardirqs_on+0xe7/0x10e [] mutex_lock_nested+0x21a/0x222 [] cpufreq_governor_dbs+0x25e/0x2ed [] cpufreq_governor_dbs+0x270/0x2ed [] __cpufreq_governor+0x73/0xa6 [] __cpufreq_set_policy+0x129/0x19e [] store_scaling_governor+0x112/0x135 [] handle_update+0x0/0x21 [] atkbd_set_leds+0x9/0xcf [] store_scaling_governor+0x0/0x135 [] store+0x3c/0x54 [] sysfs_write_file+0xa9/0xdd [] sysfs_write_file+0x0/0xdd [] vfs_write+0x83/0xf6 [] sys_write+0x3c/0x63 [] sysenter_past_esp+0x5f/0xa5 [] 0xffffffff other info that might help us debug this: 3 locks held by S06cpuspeed/3493: #0: (&buffer->mutex){--..}, at: [] sysfs_write_file+0x24/0xdd #1: (&per_cpu(cpu_policy_rwsem, cpu)){----}, at: [] lock_policy_rwsem_write+0x30/0x56 #2: (dbs_mutex){--..}, at: [] cpufreq_governor_dbs+0x25e/0x2ed stack backtrace: Pid: 3493, comm: S06cpuspeed Not tainted 2.6.25.7.cpufreq_patch #2 [] print_circular_bug_tail+0x57/0x61 [] __lock_acquire+0x878/0xb05 [] lock_acquire+0x5f/0x79 [] __cancel_work_timer+0x80/0x177 [] __cancel_work_timer+0xab/0x177 [] __cancel_work_timer+0x80/0x177 [] mark_held_locks+0x39/0x53 [] mutex_lock_nested+0x20f/0x222 [] trace_hardirqs_on+0xe7/0x10e [] mutex_lock_nested+0x21a/0x222 [] cpufreq_governor_dbs+0x25e/0x2ed [] cpufreq_governor_dbs+0x270/0x2ed [] __cpufreq_governor+0x73/0xa6 [] __cpufreq_set_policy+0x129/0x19e [] store_scaling_governor+0x112/0x135 [] handle_update+0x0/0x21 [] atkbd_set_leds+0x9/0xcf [] store_scaling_governor+0x0/0x135 [] store+0x3c/0x54 [] sysfs_write_file+0xa9/0xdd [] sysfs_write_file+0x0/0xdd [] vfs_write+0x83/0xf6 [] sys_write+0x3c/0x63 [] sysenter_past_esp+0x5f/0xa5 ======================= -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/