[asterisk-bugs] [Asterisk 0017407]: [patch] DEADLOCK_AVOIDANCE can actually generate dealocks

[Asterisk Bug Tracker]

The following issue has been UPDATED. 
====================================================================== 
https://issues.asterisk.org/view.php?id=17407 
====================================================================== 
Reported By:                pdf
Assigned To:                
====================================================================== 
Project:                    Asterisk
Issue ID:                   17407
Category:                   Core/General
Reproducibility:            sometimes
Severity:                   block
Priority:                   normal
Status:                     ready for testing
Target Version:             1.4.34
Asterisk Version:           1.4.31 
JIRA:                       SWP-1584 
Regression:                 No 
Reviewboard Link:            
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
====================================================================== 
Date Submitted:             2010-05-27 00:23 CDT
Last Modified:              2010-06-01 15:47 CDT
====================================================================== 
Summary:                    [patch] DEADLOCK_AVOIDANCE can actually generate
dealocks
Description: 
We have reported this issue to Digium support, however were asked to submit
the patch via this tracker.

In brief: the DEADLOCK_AVOIDANCE macro attempts to release an existing
lock, then relock after a usleep(1), to allow other code to proceed around
the lock.  However, it doesn't actually check to see if a lock was released
by the unlock, before taking a new lock.  This means that whenever there is
no lock released, a new lock is taken that will never be released, meaning
that DEADLOCK_AVOIDANCE actually leaks locks, which can obviously lead to a
deadlock.
====================================================================== 

Issue History 
Date Modified    Username       Field                    Change               
====================================================================== 
2010-06-01 15:47 lmadsen        Target Version           1.4.33 => 1.4.34    
======================================================================