Summary:	ASTERISK-02889: Previous locking improvements in chan_mgcp need to be revised (???)
Reporter:	Andrey S Pankov (casper)	Labels:
Date Opened:	2004-11-25 12:56:02.000-0600	Date Closed:	2011-06-07 14:10:45
Priority:	Minor	Regression?	No
Status:	Closed/Complete	Components:	Core/General
Versions:		Frequency of Occurrence
Related Issues:
Environment:		Attachments:	( 0) avoided_deadlock.log.txt ( 1) chan_mgcp.c.diff.txt ( 2) chan_mgcp.c.kram.diff.txt ( 3) chan_mgcp.c.v1-0.diff.txt ( 4) gdb.txt
Description:	There is a scenario leading to "channel.c:495 ast_channel_walk_locked: Avoided deadlock for 'MGCP...'". * remains functional (running), but NOT mgcp devices (no dialtone, no packet exchange, etc.). ****** ADDITIONAL INFORMATION ****** I have no possibility to run HEAD asterisk in production, that's why I've backported chan_mgcp changes from HEAD (bug ASTERISK-2840) to current v1-0. I attach log file from * console (with 'iax2 debug' and 'mgcp debug' turned on). Here is reproducible call scenario... *#1 - 192.168.255.1 (asterisk #1 [IAX2 only] "centrex") *#2 - 192.168.255.3 (asterisk #2 [MGCP CA] "casper") epA - 192.168.255.15 (DLink DG104S [MGCP] "office") epB - 192.168.255.16 (cisco ATA [MGCP] "office2") epB->MGCP/581343->*#2->IAX2/581343->*#1 (not very important part of the call flow, the only thing we need is to have an incoming call on *#2...) *#1->IAX2/101->*#2 (here it is - incoming IAX2 call) *#2->MGCP/101@epB (epB picks up, makes flash/attended transfer to MGCP/103@epA and hangs up...) ...and now the trick! MGCP/103@epA makes #/pound/unattended transfer back to MGCP/101@epB. After that all MGCP devices stop functioning and "show channels" CLI command reports about "Avoided deadlock..." for MGCP channel.
Comments:	By: Mark Spencer (markster) 2004-11-25 13:08:51.000-0600 I need to see the results of this running on CVS head, not on your backport to CVS stable.  I don't even know what the code looks like or what snapshot of CVS head mgcp you used for the port. Also I'll need a "thread apply all bt" from when it's in its bad state. By: Andrey S Pankov (casper) 2004-11-28 10:13:52.000-0600 The same "always" reproducibility for CVS HEAD 2004-11-28. Please see gdb.txt attached for "thread apply all bt full". By: Mark Spencer (markster) 2004-11-28 16:38:12.000-0600 You need to get this in a state where you can duplicate it and find me on irc.  To make things easier, please be sure you have compiled with "make clean ; make valgrind ; make install" so i can get all the details I need out of gdb.  Thanks. By: Olle Johansson (oej) 2004-12-13 01:45:06.000-0600 Any updates, any communication over IRC? /Housekeeping By: Andrey S Pankov (casper) 2004-12-16 09:10:18.000-0600 I don't have internet access for now, sorry... There was lots of attempts to communicate with markster, but no solution was found. As markster said, someone should try to compare chan_zap and chan_mgcp sources to find out what's wrong with locking within chan_mgcp. This task is too hard for me... Anybody volunteers? By: twisted (twisted) 2004-12-28 11:04:35.000-0600 isn't this related to ASTERISK-2840? By: Andrey S Pankov (casper) 2004-12-29 09:28:58.000-0600 twisted: No. This bug is a real one, 100% reproducible. ASTERISK-2840 is just a backport of changes made in head to stable. By: Andrey S Pankov (casper) 2004-12-29 09:36:24.000-0600 chan_mgcp.c.kram.diff.txt file contains changes made by kram on my system. Unfortunately, they don't fix the bug. By: Mark Spencer (markster) 2005-01-09 03:20:39.000-0600 I won't be able to fix this without access to a machine which exhibits this problem. By: Andrey S Pankov (casper) 2005-01-10 07:33:10.000-0600 Patience please... :) Today is the first working day this year! By: Olle Johansson (oej) 2005-01-30 12:31:41.000-0600 Casper: We have had a few working days now. Gentle reminder to move this bug report forward! /Housekeeping By: Andrey S Pankov (casper) 2005-02-09 12:47:34.000-0600 Still no luck getting mgcp hardware... Sorry for the delay. By: Mark Spencer (markster) 2005-02-27 18:47:11.000-0600 When you get hardware and are ready to work on it, we can reopen this.