[asterisk-bugs] [Asterisk 0012080]: Deadlock if feature in use while reload attempted

[noreply at bugs.digium.com]

The following issue has been ASSIGNED. 
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http://bugs.digium.com/view.php?id=12080 
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Reported By:                ChaseVenters
Assigned To:                file
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Project:                    Asterisk
Issue ID:                   12080
Category:                   Resources/res_features
Reproducibility:            random
Severity:                   crash
Priority:                   normal
Status:                     assigned
Asterisk Version:           1.4.18 
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:             02-26-2008 19:29 CST
Last Modified:              02-27-2008 11:03 CST
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Summary:                    Deadlock if feature in use while reload attempted
Description: 
We encountered a deadlock today with Asterisk 1.4.18. I gave Asterisk
SIGSEGV so that I could get a crash dump to see what is going on. (We don't
build with DEBUG_THREADS right now because we had a crash bug in that code
some months prior).

The deadlock appears to be this: in thread 10327, ast_module_reload()
grabs the module_list lock and then nests into the reload() callback for a
module. The res_features.c reload() function calls load_config(), which
calls unmap_features() which attempts to acquire features_lock.

Meanwhile, another thread (10314 in my dump) has features_lock read-locked
inside of ast_feature_interpret(). That calls builtin_blindtransfer()
through the .operation function pointer, which is calling finishup, and
eventually finds its way to ast_update_use_count(), which wants the
module_list lock.

So the "reload" thread 10327 has module_list and wants features_lock.
10314 has features_lock but wants module_list. A deadlock results.
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---------------------------------------------------------------------- 
 svnbot - 02-27-08 11:03  
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Repository: asterisk
Revision: 104596

U   branches/1.4/main/loader.c

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r104596 | file | 2008-02-27 11:03:55 -0600 (Wed, 27 Feb 2008) | 4 lines

Use the lock (which already existed, it just wasn't used) on the updaters
list to protect the contents instead of the overall module list lock.
(closes issue http://bugs.digium.com/view.php?id=12080)
Reported by: ChaseVenters

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http://svn.digium.com/view/asterisk?view=rev&revision=104596 

Issue History 
Date Modified   Username       Field                    Change               
====================================================================== 
02-27-08 11:03  svnbot         Checkin                                      
02-27-08 11:03  svnbot         Note Added: 0083049                          
02-27-08 11:03  svnbot         Status                   confirmed => assigned
02-27-08 11:03  svnbot         Assigned To               => file            
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