[asterisk-bugs] [Asterisk 0018716]: manager_park can deadlock with ast_channel_free, for channel 1 of the park operation (channel list v channel lock)

[Asterisk Bug Tracker]

The following issue has been SUBMITTED. 
====================================================================== 
https://issues.asterisk.org/view.php?id=18716 
====================================================================== 
Reported By:                davidw
Assigned To:                
====================================================================== 
Project:                    Asterisk
Issue ID:                   18716
Category:                   Channels/General
Reproducibility:            have not tried
Severity:                   major
Priority:                   normal
Status:                     new
Asterisk Version:           SVN 
JIRA:                        
Regression:                 No 
Reviewboard Link:            
SVN Branch (only for SVN checkouts, not tarball releases): 1.6.2 
SVN Revision (number only!): 305082 
Request Review:              
====================================================================== 
Date Submitted:             2011-01-31 10:48 CST
Last Modified:              2011-01-31 10:48 CST
====================================================================== 
Summary:                    manager_park can deadlock with ast_channel_free, for
channel 1 of the park operation (channel list v channel lock)
Description: 
manager_park (in features.c) does ast_get_channel_by_name_locked on both
channels that it is given.  This locks the list of channels during its
processing, meaning that the manager thread ends up locking channel 1, and
then the list of channels.

ast_channel_free write locks the list of channels, then temporarily locks
the channel it is freeing, meaning it applies lock in the reverse order!

A real deadlock has been observed with manager_park waiting for channel
list and ast_channel_free waiting for the channel.
====================================================================== 

Issue History 
Date Modified    Username       Field                    Change               
====================================================================== 
2011-01-31 10:48 davidw         New Issue                                    
2011-01-31 10:48 davidw         Asterisk Version          => SVN             
2011-01-31 10:48 davidw         Regression                => No              
2011-01-31 10:48 davidw         SVN Branch (only for SVN checkouts, not tarball
releases) => 1.6.2           
2011-01-31 10:48 davidw         SVN Revision (number only!) => 305082          
======================================================================