[asterisk-bugs] [Asterisk 0011818]: Deadlock in chan_zap between zt_request and do_monitor

[noreply at bugs.digium.com]

A NOTE has been added to this issue. 
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http://bugs.digium.com/view.php?id=11818 
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Reported By:                michael-fig
Assigned To:                
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Project:                    Asterisk
Issue ID:                   11818
Category:                   Channels/chan_zap
Reproducibility:            random
Severity:                   major
Priority:                   normal
Status:                     feedback
Asterisk Version:           1.4.16.2 
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Disclaimer on File?:        N/A 
Request Review:              
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Date Submitted:             01-22-2008 13:17 CST
Last Modified:              02-05-2008 13:29 CST
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Summary:                    Deadlock in chan_zap between zt_request and
do_monitor
Description: 
We have Asterisk installed using SIP internally and a Sangoma T1 PRI card
(AFT101) to the outside world.  Every once in a while, Asterisk would hang,
and when I investigated further, the deadlock detection code found a
deadlock in chan_zap.

I've attached the complete log (from the first Deadlock message to the
point when the connection hung) for you to look at.  In brief, there were a
lot of messages of the form:

[Jan 21 14:36:10] ERROR[4211]:
/usr/src/asterisk-1.4.16.2/include/asterisk/lock.h:338
__ast_pthread_mutex_lock: chan_zap.c line 2722 (zt_hangup): Deadlock?
waited 10 sec for mutex '&iflock'?
[Jan 21 14:36:10] ERROR[4211]:
/usr/src/asterisk-1.4.16.2/include/asterisk/lock.h:342
__ast_pthread_mutex_lock: chan_zap.c line 6804 (do_monitor): '&iflock' was
locked here.

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---------------------------------------------------------------------- 
 putnopvut - 02-05-08 13:29  
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I gave this a look, and what's odd is that the section of code where that
lock is locked does not have any blocking calls. The only thing within that
code section that I believe could cause problems would be if the iflist's
pointers became incorrect and caused an infinite loop.

Having said that, I found a place in the code which seems to improperly
handle a pointer and which could lead to the infinite loop I suspect is
happening. I'm going to upload a patch. Please give it a try and see if
this prevents the deadlock you are experiencing. Thanks. 

Issue History 
Date Modified   Username       Field                    Change               
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02-05-08 13:29  putnopvut      Note Added: 0081713                          
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