From: Stefan Richter <stefanr@s5r6.in-berlin.de>
To: linux-kernel@vger.kernel.org
Cc: Jay Fenlason <fenlason@redhat.com>
Subject: possible recursive locking detected... in __wake_up
Date: Tue, 09 Oct 2007 01:03:22 +0200 [thread overview]
Message-ID: <470AB73A.9020503@s5r6.in-berlin.de> (raw)
In-Reply-To: <20071008210029.GA19900@redhat.com>
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: [<c042671c>] __wake_up+0x15/0x42
>>
>> but task is already holding lock:
>> (&q->lock){++..}, at: [<c042671c>] __wake_up+0x15/0x42
>>
>> other info that might help us debug this:
>> 2 locks held by X/2522:
>> #0: (&client->lock){.+..}, at: [<e0993f51>] queue_event+0x2b/0x68 [firewire_core]
>> #1: (&q->lock){++..}, at: [<c042671c>] __wake_up+0x15/0x42
>>
>> stack backtrace:
>> [<c0406463>] show_trace_log_lvl+0x1a/0x2f
>> [<c0406e4d>] show_trace+0x12/0x14
>> [<c0406e65>] dump_stack+0x16/0x18
>> [<c0449c56>] __lock_acquire+0x189/0xc67
>> [<c044abae>] lock_acquire+0x7b/0x9e
>> [<c0634712>] _spin_lock_irqsave+0x4a/0x77
>> [<c042671c>] __wake_up+0x15/0x42
>> [<c04aed7e>] ep_poll_safewake+0x86/0xa8
>> [<c04afa05>] ep_poll_callback+0x9f/0xaa
>> [<c042483e>] __wake_up_common+0x32/0x55
>> [<c0426738>] __wake_up+0x31/0x42
>> [<e0993f7d>] queue_event+0x57/0x68 [firewire_core]
>> [<e0994a5a>] handle_request+0xd8/0xe0 [firewire_core]
>> [<e099269a>] fw_core_handle_request+0x215/0x23c [firewire_core]
>> [<e0961c42>] handle_ar_packet+0xd7/0xeb [firewire_ohci]
>> [<e0962bac>] ar_context_tasklet+0xb6/0xc4 [firewire_ohci]
>> [<c0432b5b>] tasklet_action+0x68/0xd3
>> [<c0432a39>] __do_softirq+0x78/0xff
>> [<c04075d4>] 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/
parent reply other threads:[~2007-10-08 23:03 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
[parent not found: <20071008210029.GA19900@redhat.com>]
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