INFO: possible circular locking dependency detected kacpi_hotplug

[Zdenek Kabelac]

Hello

I've noticed this INFO trace in my message log - happened during
undocking T61 C2D 4GB

Zdenek


=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.31-rc4-00001-gec938c6 #74
-------------------------------------------------------
 /113 is trying to acquire lock:
 (kacpid){+.+.+.}, at: [<ffffffff81062ca0>] flush_workqueue+0x0/0xc0

but task is already holding lock:
 (&dpc->work){+.+.+.}, at: [<ffffffff81061286>] worker_thread+0x196/0x3a0

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&dpc->work){+.+.+.}:
       [<ffffffff8107be6c>] __lock_acquire+0xc5c/0x1090
       [<ffffffff8107c338>] lock_acquire+0x98/0x140
       [<ffffffff810612d2>] worker_thread+0x1e2/0x3a0
       [<ffffffff8106687e>] kthread+0x9e/0xb0
       [<ffffffff8100d1da>] child_rip+0xa/0x20
       [<ffffffffffffffff>] 0xffffffffffffffff

-> #0 (kacpid){+.+.+.}:
       [<ffffffff8107bf3f>] __lock_acquire+0xd2f/0x1090
       [<ffffffff8107c338>] lock_acquire+0x98/0x140
       [<ffffffff81062d02>] flush_workqueue+0x62/0xc0
       [<ffffffff8120bbd0>] acpi_os_wait_events_complete+0x15/0x23
       [<ffffffff8120bc0d>] acpi_os_execute_hp_deferred+0x2f/0x43
       [<ffffffff810612d8>] worker_thread+0x1e8/0x3a0
       [<ffffffff8106687e>] kthread+0x9e/0xb0
       [<ffffffff8100d1da>] child_rip+0xa/0x20
       [<ffffffffffffffff>] 0xffffffffffffffff

other info that might help us debug this:

2 locks held by kacpi_hotplug/113:
 #0:  (kacpi_hotplug){+.+...}, at: [<ffffffff81061286>]
worker_thread+0x196/0x3a0
 #1:  (&dpc->work){+.+.+.}, at: [<ffffffff81061286>] worker_thread+0x196/0x3a0

stack backtrace:
Pid: 113, comm: kacpi_hotplug Not tainted 2.6.31-rc4-00001-gec938c6 #74
Call Trace:
 [<ffffffff81079e65>] print_circular_bug_tail+0xa5/0xf0
 [<ffffffff8107bf3f>] __lock_acquire+0xd2f/0x1090
 [<ffffffff8107857f>] ? save_trace+0x3f/0xb0
 [<ffffffff8107c338>] lock_acquire+0x98/0x140
 [<ffffffff81062ca0>] ? flush_workqueue+0x0/0xc0
 [<ffffffff8120bbde>] ? acpi_os_execute_hp_deferred+0x0/0x43
 [<ffffffff81062d02>] flush_workqueue+0x62/0xc0
 [<ffffffff81062ca0>] ? flush_workqueue+0x0/0xc0
 [<ffffffff81061286>] ? worker_thread+0x196/0x3a0
 [<ffffffff8120bbd0>] acpi_os_wait_events_complete+0x15/0x23
 [<ffffffff8120bc0d>] acpi_os_execute_hp_deferred+0x2f/0x43
 [<ffffffff810612d8>] worker_thread+0x1e8/0x3a0
 [<ffffffff81061286>] ? worker_thread+0x196/0x3a0
 [<ffffffff81378c5b>] ? thread_return+0x3e/0x703
 [<ffffffff81066c60>] ? autoremove_wake_function+0x0/0x40
 [<ffffffff810610f0>] ? worker_thread+0x0/0x3a0
 [<ffffffff8106687e>] kthread+0x9e/0xb0
 [<ffffffff8100d1da>] child_rip+0xa/0x20
 [<ffffffff8100cb7c>] ? restore_args+0x0/0x30
 [<ffffffff810667e0>] ? kthread+0x0/0xb0
 [<ffffffff8100d1d0>] ? child_rip+0x0/0x20
ACPI: \_SB_.GDCK - undocking
usb 1-4: USB disconnect, address 4
usb 1-4.3: USB disconnect, address 5
usb 1-4.4: USB disconnect, address 6
e1000e: eth0 NIC Link is Down
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