Hi list,

how could this ever happen?

>> =============================================
>> [ INFO: possible recursive locking detected ]
>> 2.6.23-0.222.rc9.git4.fc8 #1
>> ---------------------------------------------
>> X/2522 is trying to acquire lock:
>> (&q->lock){++..}, at: [] __wake_up+0x15/0x42
>>
>> but task is already holding lock:
>> (&q->lock){++..}, at: [] __wake_up+0x15/0x42
>>
>> other info that might help us debug this:
>> 2 locks held by X/2522:
>> #0: (&client->lock){.+..}, at: [] queue_event+0x2b/0x68 [firewire_core]
>> #1: (&q->lock){++..}, at: [] __wake_up+0x15/0x42
>>
>> stack backtrace:
>> [] show_trace_log_lvl+0x1a/0x2f
>> [] show_trace+0x12/0x14
>> [] dump_stack+0x16/0x18
>> [] __lock_acquire+0x189/0xc67
>> [] lock_acquire+0x7b/0x9e
>> [] _spin_lock_irqsave+0x4a/0x77
>> [] __wake_up+0x15/0x42
>> [] ep_poll_safewake+0x86/0xa8
>> [] ep_poll_callback+0x9f/0xaa
>> [] __wake_up_common+0x32/0x55
>> [] __wake_up+0x31/0x42
>> [] queue_event+0x57/0x68 [firewire_core]
>> [] handle_request+0xd8/0xe0 [firewire_core]
>> [] fw_core_handle_request+0x215/0x23c [firewire_core]
>> [] handle_ar_packet+0xd7/0xeb [firewire_ohci]
>> [] ar_context_tasklet+0xb6/0xc4 [firewire_ohci]
>> [] tasklet_action+0x68/0xd3
>> [] __do_softirq+0x78/0xff
>> [] do_softirq+0x74/0xf7
>> =======================

(from https://bugzilla.redhat.com/show_bug.cgi?id=323411)

We wake up the queue from a workqueue context (rarely) and from tasklet
context (frequently). However, since __wake_up disables local IRQs, it
should be entirely impossible for __wake_up to take q->lock twice before
releasing it. What's the deal?
--
Stefan Richter
-=====-=-=== =-=- -=--=
http://arcgraph.de/sr/
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