Messages in this thread | | | Date | Thu, 26 Jun 2008 17:48:14 +0530 | From | Nageswara R Sastry <> | Subject | Re: [BUG] While changing the cpufreq governor, kernel hits a bug in workqueue.c |
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Hi,
Johannes Weiner wrote:
> From: Johannes Weiner <hannes@saeurebad.de> > 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 <rnsastry@linux.vnet.ibm.com> > Signed-off-by: Johannes Weiner <hannes@saeurebad.de> > --- > > 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: [<c012f46c>] __cancel_work_timer+0x80/0x177
but task is already holding lock: (dbs_mutex){--..}, at: [<c041e7cb>] cpufreq_governor_dbs+0x25e/0x2ed
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (dbs_mutex){--..}: [<c013aa76>] add_lock_to_list+0x61/0x83 [<c013cfa3>] __lock_acquire+0x953/0xb05 [<c041e5e1>] cpufreq_governor_dbs+0x74/0x2ed [<c013d1b4>] lock_acquire+0x5f/0x79 [<c041e5e1>] cpufreq_governor_dbs+0x74/0x2ed [<c04cdaa7>] mutex_lock_nested+0xce/0x222 [<c041e5e1>] cpufreq_governor_dbs+0x74/0x2ed [<c041e5e1>] cpufreq_governor_dbs+0x74/0x2ed [<c041e5e1>] cpufreq_governor_dbs+0x74/0x2ed [<c041c87a>] __cpufreq_governor+0x73/0xa6 [<c041c9e8>] __cpufreq_set_policy+0x13b/0x19e [<c041d6b5>] cpufreq_add_dev+0x3b4/0x4aa [<c041d296>] handle_update+0x0/0x21 [<c02ee310>] sysdev_driver_register+0x48/0x9a [<c041c75b>] cpufreq_register_driver+0x9b/0x147 [<c06b742c>] kernel_init+0x130/0x26f [<c06b72fc>] kernel_init+0x0/0x26f [<c06b72fc>] kernel_init+0x0/0x26f [<c0105527>] kernel_thread_helper+0x7/0x10 [<ffffffff>] 0xffffffff
-> #1 (&per_cpu(cpu_policy_rwsem, cpu)){----}: [<c013cfa3>] __lock_acquire+0x953/0xb05 [<c041d194>] lock_policy_rwsem_write+0x30/0x56 [<c010a83b>] save_stack_trace+0x1a/0x35 [<c013d1b4>] lock_acquire+0x5f/0x79 [<c041d194>] lock_policy_rwsem_write+0x30/0x56 [<c04cdfd9>] down_write+0x2b/0x44 [<c041d194>] lock_policy_rwsem_write+0x30/0x56 [<c041d194>] lock_policy_rwsem_write+0x30/0x56 [<c041e35e>] do_dbs_timer+0x40/0x24f [<c012ee7f>] run_workqueue+0x81/0x187 [<c012eeba>] run_workqueue+0xbc/0x187 [<c012ee7f>] run_workqueue+0x81/0x187 [<c041e31e>] do_dbs_timer+0x0/0x24f [<c012f6fa>] worker_thread+0x0/0xbd [<c012f7ad>] worker_thread+0xb3/0xbd [<c0131acc>] autoremove_wake_function+0x0/0x2d [<c0131a1b>] kthread+0x38/0x5d [<c01319e3>] kthread+0x0/0x5d [<c0105527>] kernel_thread_helper+0x7/0x10 [<ffffffff>] 0xffffffff
-> #0 (&(&dbs_info->work)->work){--..}: [<c013b6a2>] print_circular_bug_tail+0x2a/0x61 [<c013cec8>] __lock_acquire+0x878/0xb05 [<c013d1b4>] lock_acquire+0x5f/0x79 [<c012f46c>] __cancel_work_timer+0x80/0x177 [<c012f497>] __cancel_work_timer+0xab/0x177 [<c012f46c>] __cancel_work_timer+0x80/0x177 [<c013c0ee>] mark_held_locks+0x39/0x53 [<c04cdbe8>] mutex_lock_nested+0x20f/0x222 [<c013c277>] trace_hardirqs_on+0xe7/0x10e [<c04cdbf3>] mutex_lock_nested+0x21a/0x222 [<c041e7cb>] cpufreq_governor_dbs+0x25e/0x2ed [<c041e7dd>] cpufreq_governor_dbs+0x270/0x2ed [<c041c87a>] __cpufreq_governor+0x73/0xa6 [<c041c9d6>] __cpufreq_set_policy+0x129/0x19e [<c041ce0b>] store_scaling_governor+0x112/0x135 [<c041d296>] handle_update+0x0/0x21 [<c0410065>] atkbd_set_leds+0x9/0xcf [<c041ccf9>] store_scaling_governor+0x0/0x135 [<c041d7e7>] store+0x3c/0x54 [<c01a09a0>] sysfs_write_file+0xa9/0xdd [<c01a08f7>] sysfs_write_file+0x0/0xdd [<c016e412>] vfs_write+0x83/0xf6 [<c016e958>] sys_write+0x3c/0x63 [<c0104816>] sysenter_past_esp+0x5f/0xa5 [<ffffffff>] 0xffffffff
other info that might help us debug this:
3 locks held by S06cpuspeed/3493: #0: (&buffer->mutex){--..}, at: [<c01a091b>] sysfs_write_file+0x24/0xdd #1: (&per_cpu(cpu_policy_rwsem, cpu)){----}, at: [<c041d194>] lock_policy_rwsem_write+0x30/0x56 #2: (dbs_mutex){--..}, at: [<c041e7cb>] cpufreq_governor_dbs+0x25e/0x2ed
stack backtrace: Pid: 3493, comm: S06cpuspeed Not tainted 2.6.25.7.cpufreq_patch #2 [<c013b6cf>] print_circular_bug_tail+0x57/0x61 [<c013cec8>] __lock_acquire+0x878/0xb05 [<c013d1b4>] lock_acquire+0x5f/0x79 [<c012f46c>] __cancel_work_timer+0x80/0x177 [<c012f497>] __cancel_work_timer+0xab/0x177 [<c012f46c>] __cancel_work_timer+0x80/0x177 [<c013c0ee>] mark_held_locks+0x39/0x53 [<c04cdbe8>] mutex_lock_nested+0x20f/0x222 [<c013c277>] trace_hardirqs_on+0xe7/0x10e [<c04cdbf3>] mutex_lock_nested+0x21a/0x222 [<c041e7cb>] cpufreq_governor_dbs+0x25e/0x2ed [<c041e7dd>] cpufreq_governor_dbs+0x270/0x2ed [<c041c87a>] __cpufreq_governor+0x73/0xa6 [<c041c9d6>] __cpufreq_set_policy+0x129/0x19e [<c041ce0b>] store_scaling_governor+0x112/0x135 [<c041d296>] handle_update+0x0/0x21 [<c0410065>] atkbd_set_leds+0x9/0xcf [<c041ccf9>] store_scaling_governor+0x0/0x135 [<c041d7e7>] store+0x3c/0x54 [<c01a09a0>] sysfs_write_file+0xa9/0xdd [<c01a08f7>] sysfs_write_file+0x0/0xdd [<c016e412>] vfs_write+0x83/0xf6 [<c016e958>] sys_write+0x3c/0x63 [<c0104816>] sysenter_past_esp+0x5f/0xa5 =======================
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