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Message-ID: <4BD8196E.3000407@redhat.com>
Date: Wed, 28 Apr 2010 19:18:06 +0800
From: Cong Wang <amwang@...hat.com>
To: Dave Jones <davej@...hat.com>, Miles Lane <miles.lane@...il.com>,
Greg Kroah-Hartman <gregkh@...e.de>,
LKML <linux-kernel@...r.kernel.org>,
Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
"Rafael J. Wysocki" <rjw@...k.pl>,
Amerigo Wang <amwang@...hat.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: 2.6.34-rc5-git7 -- INFO: possible circular locking dependency
detected - &per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [<ffffffff8139f077>]
lock_policy_rwsem_read+0x4a/0x7a
(Adding Eric B. into Cc.)
Dave Jones wrote:
> On Mon, Apr 26, 2010 at 09:30:41PM -0400, Miles Lane wrote:
> > Dave, is this the same? http://marc.info/?l=linux-kernel&m=127207512031810&w=2
>
> looks like it to me. 499bca9b6d3243f9278a1f5a22d00e67acdd844d should have fixed it,
> but it looks like that's present in -git7, so something is still missing..
>
> Dave
>
> > I produced this one by running "find /sys | xargs cat"
> >
> > [ 2982.773548] [ INFO: possible circular locking dependency detected ]
> > [ 2982.773551] 2.6.34-rc5-git7 #33
> > [ 2982.773554] -------------------------------------------------------
> > [ 2982.773557] head/6335 is trying to acquire lock:
> > [ 2982.773560] (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at:
> > [<ffffffff8139f077>] lock_policy_rwsem_read+0x4a/0x7a
> > [ 2982.773571]
> > [ 2982.773572] but task is already holding lock:
> > [ 2982.773575] (s_active#102){++++.+}, at: [<ffffffff81153a23>]
> > sysfs_read_file+0x8d/0x139
> > [ 2982.773586]
> > [ 2982.773586] which lock already depends on the new lock.
> > [ 2982.773587]
> > [ 2982.773590]
> > [ 2982.773591] the existing dependency chain (in reverse order) is:
> > [ 2982.773593]
> > [ 2982.773594] -> #2 (s_active#102){++++.+}:
> > [ 2982.773601] [<ffffffff8107654d>] __lock_acquire+0xb59/0xd11
> > [ 2982.773608] [<ffffffff8107681a>] lock_acquire+0x115/0x150
> > [ 2982.773613] [<ffffffff81154556>] sysfs_deactivate+0x9b/0xec
> > [ 2982.773619] [<ffffffff81154d0a>] sysfs_addrm_finish+0x31/0x50
> > [ 2982.773624] [<ffffffff81152e05>] sysfs_hash_and_remove+0x4e/0x65
> > [ 2982.773629] [<ffffffff81155fc0>] sysfs_remove_group+0x8c/0xc5
> > [ 2982.773634] [<ffffffffa00a3d26>]
> > cpufreq_governor_dbs+0x2a6/0x33c [cpufreq_ondemand]
> > [ 2982.773642] [<ffffffff8139da32>] __cpufreq_governor+0x5d/0xa3
> > [ 2982.773648] [<ffffffff8139e4e2>] __cpufreq_remove_dev+0x231/0x2e2
> > [ 2982.773653] [<ffffffff81454e40>] cpufreq_cpu_callback+0x62/0x7a
> > [ 2982.773660] [<ffffffff8145d636>] notifier_call_chain+0x63/0x97
> > [ 2982.773666] [<ffffffff810680dc>] __raw_notifier_call_chain+0x9/0xb
> > [ 2982.773672] [<ffffffff8144337b>] _cpu_down+0x90/0x29e
> > [ 2982.773679] [<ffffffff81048cd7>] disable_nonboot_cpus+0x6f/0x105
> > [ 2982.773685] [<ffffffff81083b94>] suspend_devices_and_enter+0xe8/0x1ec
> > [ 2982.773691] [<ffffffff81083d72>] enter_state+0xda/0x12b
> > [ 2982.773696] [<ffffffff810834d5>] state_store+0xb1/0xce
> > [ 2982.773702] [<ffffffff811f2fb3>] kobj_attr_store+0x17/0x19
> > [ 2982.773708] [<ffffffff8115395a>] sysfs_write_file+0x103/0x13f
> > [ 2982.773713] [<ffffffff810fb933>] vfs_write+0xa9/0x106
> > [ 2982.773719] [<ffffffff810fba46>] sys_write+0x45/0x69
> > [ 2982.773723] [<ffffffff81009d82>] system_call_fastpath+0x16/0x1b
> > [ 2982.773730]
> > [ 2982.773731] -> #1 (dbs_mutex){+.+.+.}:
> > [ 2982.773737] [<ffffffff8107654d>] __lock_acquire+0xb59/0xd11
> > [ 2982.773742] [<ffffffff8107681a>] lock_acquire+0x115/0x150
> > [ 2982.773747] [<ffffffff814582ce>] __mutex_lock_common+0x57/0x558
> > [ 2982.773752] [<ffffffff81458875>] mutex_lock_nested+0x34/0x39
> > [ 2982.773757] [<ffffffffa00a3af6>]
> > cpufreq_governor_dbs+0x76/0x33c [cpufreq_ondemand]
> > [ 2982.773763] [<ffffffff8139da32>] __cpufreq_governor+0x5d/0xa3
> > [ 2982.773769] [<ffffffff8139e7ec>] __cpufreq_set_policy+0x1a8/0x222
> > [ 2982.773774] [<ffffffff8139ecca>] store_scaling_governor+0x19f/0x1ed
> > [ 2982.773779] [<ffffffff8139e622>] store+0x56/0x78
> > [ 2982.773783] [<ffffffff8115395a>] sysfs_write_file+0x103/0x13f
> > [ 2982.773788] [<ffffffff810fb933>] vfs_write+0xa9/0x106
> > [ 2982.773793] [<ffffffff810fba46>] sys_write+0x45/0x69
> > [ 2982.773798] [<ffffffff81009d82>] system_call_fastpath+0x16/0x1b
> > [ 2982.773803]
> > [ 2982.773804] -> #0 (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}:
> > [ 2982.773810] [<ffffffff810763f7>] __lock_acquire+0xa03/0xd11
> > [ 2982.773815] [<ffffffff8107681a>] lock_acquire+0x115/0x150
> > [ 2982.773820] [<ffffffff81458bba>] down_read+0x42/0x57
> > [ 2982.773825] [<ffffffff8139f077>] lock_policy_rwsem_read+0x4a/0x7a
> > [ 2982.773830] [<ffffffff8139f0d7>] show+0x30/0x69
> > [ 2982.773835] [<ffffffff81153a4a>] sysfs_read_file+0xb4/0x139
> > [ 2982.773840] [<ffffffff810fbb10>] vfs_read+0xa6/0x103
> > [ 2982.773844] [<ffffffff810fbc23>] sys_read+0x45/0x69
> > [ 2982.773849] [<ffffffff81009d82>] system_call_fastpath+0x16/0x1b
> > [ 2982.773854]
> > [ 2982.773855] other info that might help us debug this:
> > [ 2982.773856]
> > [ 2982.773860] 2 locks held by head/6335:
> > [ 2982.773862] #0: (&buffer->mutex){+.+.+.}, at:
> > [<ffffffff811539ca>] sysfs_read_file+0x34/0x139
> > [ 2982.773871] #1: (s_active#102){++++.+}, at: [<ffffffff81153a23>]
> > sysfs_read_file+0x8d/0x139
> > [ 2982.773881]
> > [ 2982.773882] stack backtrace:
> > [ 2982.773886] Pid: 6335, comm: head Not tainted 2.6.34-rc5-git7 #33
> > [ 2982.773889] Call Trace:
> > [ 2982.773893] [<ffffffff810755c3>] print_circular_bug+0xa8/0xb7
> > [ 2982.773893] [<ffffffff810763f7>] __lock_acquire+0xa03/0xd11
> > [ 2982.773893] [<ffffffff810766f6>] ? __lock_acquire+0xd02/0xd11
> > [ 2982.773893] [<ffffffff8139f077>] ? lock_policy_rwsem_read+0x4a/0x7a
> > [ 2982.773893] [<ffffffff8107681a>] lock_acquire+0x115/0x150
> > [ 2982.773893] [<ffffffff8139f077>] ? lock_policy_rwsem_read+0x4a/0x7a
> > [ 2982.773893] [<ffffffff81458bba>] down_read+0x42/0x57
> > [ 2982.773893] [<ffffffff8139f077>] ? lock_policy_rwsem_read+0x4a/0x7a
> > [ 2982.773893] [<ffffffff81459cb9>] ? _raw_spin_unlock_irqrestore+0x87/0x95
> > [ 2982.773893] [<ffffffff8139f077>] lock_policy_rwsem_read+0x4a/0x7a
> > [ 2982.773893] [<ffffffff8139f0d7>] show+0x30/0x69
> > [ 2982.773893] [<ffffffff81153a4a>] sysfs_read_file+0xb4/0x139
> > [ 2982.773893] [<ffffffff810fbb10>] vfs_read+0xa6/0x103
> > [ 2982.773893] [<ffffffff81074eae>] ? trace_hardirqs_on_caller+0x127/0x152
> > [ 2982.773893] [<ffffffff810fbc23>] sys_read+0x45/0x69
> > [ 2982.773893] [<ffffffff81009d82>] system_call_fastpath+0x16/0x1b
>
With Eric B.'s patch, lockdep will treat s_active as a rwsem too, thus causes
this warning...
Thanks.
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