Messages in this thread | | | Date | Tue, 09 Oct 2007 01:03:22 +0200 | From | Stefan Richter <> | Subject | possible recursive locking detected... in __wake_up |
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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/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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