[asterisk-bugs] [Asterisk 0018310]: hint state changes deadlock/race

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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https://issues.asterisk.org/view.php?id=18310 
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Reported By:                one47
Assigned To:                
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Project:                    Asterisk
Issue ID:                   18310
Category:                   Core/PBX
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     new
Asterisk Version:           1.6.2.14 
JIRA:                       SWP-2541 
Regression:                 No 
Reviewboard Link:            
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2010-11-15 12:19 CST
Last Modified:              2010-11-16 09:43 CST
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Summary:                    hint state changes deadlock/race
Description: 
VERY similar to https://issues.asterisk.org/view.php?id=18165, but this is a
different deadlock path, so I have
raised a separate report.

Thread 1: taskprocessor  -> handle_statechange
    Lock order = conlock, hints, hint, pvt
Thread 2: chan_sip.c:  handle_request_do -> handle_response_notify
    Lock order = pvt, conlock

Thread2 only gets into the conlock if STATECHANGEQUEUE is true, ie. there
are rapid state changes happening on a subscribed hint.
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 (0128895) one47 (reporter) - 2010-11-16 09:43
 https://issues.asterisk.org/view.php?id=18310#c128895 
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I think the conlock is necessary in ast_hint_extension because this ends up
calling pbx_find_extension.

To solve this deadlock, I think it will be necessary to update the
callback functions to return -1 if they cannot get a lock.
handle_statechange can then release (conlocks, hints, hint) locks,
usleep(1), grab locks and try again.

I am experimenting with this now and will post a patch if it seems
alright. 

Issue History 
Date Modified    Username       Field                    Change               
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2010-11-16 09:43 one47          Note Added: 0128895                          
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