[asterisk-bugs] [Asterisk 0015349]: Deadlock in do_monitor() of chan_sip

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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https://issues.asterisk.org/view.php?id=15349 
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Reported By:                samy
Assigned To:                mmichelson
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Project:                    Asterisk
Issue ID:                   15349
Category:                   Channels/chan_sip/General
Reproducibility:            have not tried
Severity:                   major
Priority:                   normal
Status:                     assigned
Asterisk Version:           1.6.0.10 
Regression:                 No 
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2009-06-17 22:08 CDT
Last Modified:              2009-06-29 20:53 CDT
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Summary:                    Deadlock in do_monitor() of chan_sip
Description: 
Unfortunately I have no steps to reproduce this. Had about 30 calls going
through, all calls are SIP, and randomly ran into a SIP deadlock (`sip show
channels` would cause console to hang, no new SIP calls would begin).

It sort of looks like `dialoglist` is an infinite loop (every member
points to at least one other member, there is never a ->next that points to
null), but I don't see how that could happen in the code so I'm not sure.

I did get `core show locks` output a few times, and I have a modified
version that provides the time of the last time each lock was
locked/unlocked. This is interesting because we can see lock
https://issues.asterisk.org/view.php?id=0 never
changes and is held for multiple minutes before I restart, but lock
https://issues.asterisk.org/view.php?id=1
changes constantly.

The fact that lock https://issues.asterisk.org/view.php?id=1 (lock on
dialog->sip_pvt) is constantly changing in
do_monitor makes me think `dialoglist` is an infinite loop.
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 (0107215) samy (reporter) - 2009-06-29 20:53
 https://issues.asterisk.org/view.php?id=15349#c107215 
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One additional note, the infinite loop in `dialoglist` starts from the
beginning (meaning `dialoglist` is repeated).

It COULD have been:
a -> b -> c -> d -> b -> c -> d -> b -> c -> d....

But in two instances of the loop, it's always looped back to 'a' (which I
think could further be proof for my theory, but who knows...not me :)

In the two cores that I have, it's:
a -> b -> c -> d -> a -> b -> c -> d -> a... 

Issue History 
Date Modified    Username       Field                    Change               
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2009-06-29 20:53 samy           Note Added: 0107215                          
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