[mythtv-users] Best way to submit debug data for Mythbuntu 0.24 autobuilds

Michael T. Dean mtdean at thirdcontact.com
Mon Oct 11 16:53:38 UTC 2010


  On 10/11/2010 08:09 AM, James Crow wrote:
> I have been running Mythbuntu 10.04 w/ 0.24 autbuilds for a few weeks.
> A couple of times a week my MBE locks up. It does not segfault, it
> just stops responding to any FE and the current recordings on the MBE
> stop as well. The problem always occurs just as a show is starting to
> record. I want to make sure I get the required debugging data to
> submit a ticket.
>
> I have the mythtv-dbg build installed. I think I will need to run
> mythbackend under gdb as per the documentation. On Mythbuntu the BE is
> normally run as user mythtv. Should I alter the upstart script to make
> mythbackend run under gdb? Should I start gdb/mythbackend from a
> normal shell and wait for the lockup to Ctrl-C the gdb process? I
> think the documentation is describing a situation where the BE seg
> faults rather than just locks up. Any ideas of the proper way to
> generate a backtrace under these circumstances is appreciated.

Another option is to run mythbackend normally, then attach gdb to the 
running (and locked up) process, as at

http://sourceware.org/gdb/download/onlinedocs/gdb/Attach.html#Attach

Find the process ID for the appropriate mythbackend process (remember 
that in 0.23-fixes and below, some mythbackend processes are used to 
generate previews, so you will likely want to use the oldest of the 
processes).

ps -efw | grep mythback

Once you know the process ID, start gdb and submit the commands:

handle SIGPIPE nostop noprint
handle SIG33 nostop noprint
set logging on
set pagination off
set breakpoint pending on
break qFatal
thread apply all bt full

and once you've gotten the information you need,

set logging off

Once you've been through the process, free to clean up the instructions 
(and fix any incorrect info I put in) and add a new section 4 to:  
http://www.mythtv.org/wiki/Debugging

Thanks,
Mike

(Yeah, some of those commands aren't necessary, but they won't hurt and 
I figured it's better to make generic instructions that would allow 
anyone to use this approach--even if their backend isn't locked up or 
whatever, and they planned to continue running under gdb.)


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