[asterisk-bugs] [Asterisk 0013213]: [patch] DAHDI mwi thread race conditions, sometimes crash or output wierd noises on the call

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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http://bugs.digium.com/view.php?id=13213 
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Reported By:                bbryant
Assigned To:                
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Project:                    Asterisk
Issue ID:                   13213
Category:                   Channels/chan_dahdi
Reproducibility:            sometimes
Severity:                   minor
Priority:                   normal
Status:                     new
Asterisk Version:           SVN 
SVN Branch (only for SVN checkouts, not tarball releases):  trunk 
SVN Revision (number only!): 134352 
Disclaimer on File?:        N/A 
Request Review:              
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Date Submitted:             2008-07-31 18:04 CDT
Last Modified:              2008-08-01 15:37 CDT
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Summary:                    [patch] DAHDI mwi thread race conditions, sometimes
crash or output wierd noises on the call
Description: 
DAHDI appears to have a race condition in do_monitor where it can spawn two
instances of mwi_send_data for the same dahdi_pvt structure if the ioctl
for DAHDI_MWT fails around line 7922. 

Attached is a backtrace of a crash that can occur with this issue.

My test environment is asterisk trunk r134352 and dahdi r4590 with a 4
port analog card. The test was just picking up the analog phone, and having
it drop into an immediate context that just played back a file.

Here are the debug messages, accompanied by 'dialup like' noises on the
analog phone:

[Jul 31 18:09:53] DEBUG[25958]: chan_dahdi.c:7914 do_monitor: Unable to
control message waiting led on channel 4: Inappropriate ioctl for device
[Jul 31 18:09:53] DEBUG[25963]: chan_dahdi.c:5558 dahdi_write: Dropping
frame since I've still got a callerid spill
[Jul 31 18:09:54] DEBUG[25963]: chan_dahdi.c:5558 dahdi_write: Dropping
frame since I've still got a callerid spill
[Jul 31 18:09:54] DEBUG[25963]: chan_dahdi.c:5558 dahdi_write: Dropping
frame since I've still got a callerid spill
[Jul 31 18:09:54] DEBUG[25963]: chan_dahdi.c:5558 dahdi_write: Dropping
frame since I've still got a callerid spill
[Jul 31 18:09:54] DEBUG[25963]: chan_dahdi.c:5558 dahdi_write: Dropping
frame since I've still got a callerid spill
[Jul 31 18:09:54] DEBUG[25963]: chan_dahdi.c:1954 restore_conference:
Restored conferencing
[Jul 31 18:09:54] WARNING[25962]: chan_dahdi.c:7543 mwi_send_thread: MWI
Send Write failed: Invalid argument

I've attempted a few wierd ways to fix it, but I think the patch just
creatively masking the problem instead of fixing it (still, I've attached
the patch because it makes it work).
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---------------------------------------------------------------------- 
 (0091001) dbailey (administrator) - 2008-08-01 15:37
 http://bugs.digium.com/view.php?id=13213#c91001 
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I doubt that there are two instances of the mwi_send_thread colliding but
instead is the mwi_send_thread colliding with other code that uses the cid
variables.  

The patch's utilization of local variables instead of using those in the
dahdi_pvt is a big improvement.  

I will look for collisions in handling the cid variables to see where
mwi_send_thread is treading. 

Issue History 
Date Modified    Username       Field                    Change               
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2008-08-01 15:37 dbailey        Note Added: 0091001                          
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