[asterisk-dev] [Code Review] Deadlock ao2_callback / ast_write / handle_incoming

[astmiv]

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It appears that locking a pvt is done without checking if the owner of the pvt is also locked. I have reported another issue 19107 which has the same deadlock problem with one other different location.

One thread is first locking the channel and then would like to lock pvt while another first locks the pvt and then would like to lock the channel.

When I read through the code in sip_chan.c i conclude that the channel (pvt->owner) should always be locked first before locking the pvt. Is this right?

I think we should make a solution which fixes this in every possible situation.

- astmiv


On 2011-04-13 03:17:24, irroot wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> https://reviewboard.asterisk.org/r/1171/
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> 
> (Updated 2011-04-13 03:17:24)
> 
> 
> Review request for Asterisk Developers.
> 
> 
> Summary
> -------
> 
> 
> Channel walk is contending a lock on a channel held by ast_write while sip_write is contending a private lock held by handle incoming that is contending the channel lock held by the write ...
> 
> now if i was holding the channel lock in handle_incoming before i locked private this would not happen ... 
> 
> some how ive been appointed the deadlock fairy ... monitoring +/- 100 1.8 sites for deadlocks and attempt to fix them as they
> popup.
> 
> 
> === Thread ID: 0xb3cf7b70 (do_devstate_changes started at [ 724] devicestate.c ast_device_state_engine_init())
> === ---> Lock #0 (astobj2.c): MUTEX 657 internal_ao2_callback c 0x85fe1b8 (1)
> === ---> Waiting for Lock #1 (channel.c): MUTEX 1641 ast_channel_cmp_cb chan 0xabb7a558 (1)
> === --- ---> Locked Here: channel.c line 4690 (ast_write)
> === -------------------------------------------------------------------
> ===
> === Thread ID: 0xabf3fb70 (do_monitor started at [24621] chan_sip.c restart_monitor())
> === ---> Lock #0 (chan_sip.c): MUTEX 24593 do_monitor &monlock 0xb314fde0 (1)
> === ---> Lock #1 (chan_sip.c): MUTEX 23781 handle_incoming p 0xab7c94a8 (1)
> === ---> Waiting for Lock #2 (channel.c): MUTEX 1361 __ast_queue_frame chan 0xabb7a558 (1)
> === --- ---> Locked Here: channel.c line 4690 (ast_write)
> === -------------------------------------------------------------------
> ===
> === Thread ID: 0xab6c3b70 (pbx_thread started at [ 5038] pbx.c ast_pbx_start())
> === ---> Lock #0 (channel.c): MUTEX 4690 ast_write chan 0xabb7a558 (1)
> === ---> Waiting for Lock #1 (chan_sip.c): MUTEX 6083 sip_write p 0xab7c94a8 (1)
> === --- ---> Locked Here: chan_sip.c line 23781 (handle_incoming)
> === -------------------------------------------------------------------
> === 
> 
> 
> This addresses bug 19112.
>     https://issues.asterisk.org/view.php?id=19112
> 
> 
> Diffs
> -----
> 
>   /branches/1.8/channels/chan_sip.c 313425 
> 
> Diff: https://reviewboard.asterisk.org/r/1171/diff
> 
> 
> Testing
> -------
> 
> 
> Thanks,
> 
> irroot
> 
>

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