Mailing List Archive: MythTV: Users

Please help! My mythbackend started to crash sporadically

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f-myth-users at media

Jul 2, 2008, 2:37 PM

Post #1 of 8 (450 views)
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Please help! My mythbackend started to crash sporadically

> Date: Wed, 2 Jul 2008 21:00:06 +0400
> From: Andrew Junev <a-j[at]a-j.ru>

> In this situation a script or a program that restarts the backend is
> useful, but that's not a fix. I'm sure 0.21 was working fine for me
> some time ago. I remember I had no crashes then. So there should be
> something out there to fix these crashes...

Straw-grasping time---does your BE do transcoding or other heavy
lifting? Have you made sure its CPU heatsink is firmly attached?
I know you tried running memtest; maybe take antistatic precautions
and wiggle your RAM and any other cards in the machine? Perhaps a
contact has gotten slightly corroded.

(I'd ask, "Is the machine on a UPS?" but it seems unreasonable that
some weirdo voltage sag from the PSU could lead to a BE segfault but
not a machine crash.)
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a-j at a-j

Jul 3, 2008, 12:05 AM

Post #2 of 8 (426 views)
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Re: Please help! My mythbackend started to crash sporadically [In reply to]

Thursday, July 3, 2008, 1:37:21 AM, you wrote:

> > Date: Wed, 2 Jul 2008 21:00:06 +0400
> > From: Andrew Junev <a-j[at]a-j.ru>

> > In this situation a script or a program that restarts the backend is
> > useful, but that's not a fix. I'm sure 0.21 was working fine for me
> > some time ago. I remember I had no crashes then. So there should be
> > something out there to fix these crashes...

> Straw-grasping time---does your BE do transcoding or other heavy
> lifting? Have you made sure its CPU heatsink is firmly attached?

Ths CPU heatsink is fine, I checked that two days ago.
I don't do transcoding, commercial flagging or anything like
that. I just record some shows and watch some live tv from time to
time (my MythTV system is the only DVB-S tuner in my house).

The highest load for this machine is watching some 720p movies. And it
works good all the time - no crashes, no problems.

> I know you tried running memtest; maybe take antistatic precautions
> and wiggle your RAM and any other cards in the machine? Perhaps a
> contact has gotten slightly corroded.

I did that when I cleaned the system (meaning it was 2 days ago).
Nothing changed...

> (I'd ask, "Is the machine on a UPS?" but it seems unreasonable that
> some weirdo voltage sag from the PSU could lead to a BE segfault but
> not a machine crash.)

I also think so. But the machine is on a UPS, just in case... :)

--
Best regards,
Andrew

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lists_mythtv_users at bigpizza

Jul 3, 2008, 1:14 AM

Post #3 of 8 (423 views)
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Re: Please help! My mythbackend started to crash sporadically [In reply to]

There have been several great responses on this topic detailing how to
diagnose a hardware fault. Can anyone suggest how to help diagnose a
software fault? Is there a way to capture useful information from a
backtrace that could be passed on to a myth/kernel/driver developer in
order to give them some insight into some code that can be improved?

Steve.

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a-j at a-j

Jul 3, 2008, 8:12 AM

Post #4 of 8 (416 views)
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Re: Please help! My mythbackend started to crash sporadically [In reply to]

Thursday, July 3, 2008, 12:14:59 PM, you wrote:

> There have been several great responses on this topic detailing how to
> diagnose a hardware fault. Can anyone suggest how to help diagnose a
> software fault? Is there a way to capture useful information from a
> backtrace that could be passed on to a myth/kernel/driver developer in
> order to give them some insight into some code that can be improved?

> Steve.

That's exactly what I was trying to say! :)

Thank you!

--
Best regards,
Andrew

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vitaminjoe at gmail

Jul 3, 2008, 8:19 AM

Post #5 of 8 (413 views)
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Re: Please help! My mythbackend started to crash sporadically [In reply to]

On Thu, Jul 3, 2008 at 2:14 AM, lists_mythtv_users
<lists_mythtv_users[at]bigpizza.co.uk> wrote:
> There have been several great responses on this topic detailing how to
> diagnose a hardware fault. Can anyone suggest how to help diagnose a
> software fault? Is there a way to capture useful information from a
> backtrace that could be passed on to a myth/kernel/driver developer in
> order to give them some insight into some code that can be improved?
>
> Steve.

When it comes to Myth:

http://www.mythtv.org/docs/mythtv-HOWTO-22.html#ss22.2

--
Joe Ripley
vitaminjoe[at]gmail.com
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lists_mythtv_users at bigpizza

Jul 3, 2008, 9:25 AM

Post #6 of 8 (412 views)
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Re: Please help! My mythbackend started to crash sporadically [In reply to]

Joe Ripley wrote:
> On Thu, Jul 3, 2008 at 2:14 AM, lists_mythtv_users
> <lists_mythtv_users[at]bigpizza.co.uk> wrote:
>
>> There have been several great responses on this topic detailing how to
>> diagnose a hardware fault. Can anyone suggest how to help diagnose a
>> software fault? Is there a way to capture useful information from a
>> backtrace that could be passed on to a myth/kernel/driver developer in
>> order to give them some insight into some code that can be improved?
>>
>> Steve.
>>
>
> When it comes to Myth:
>
> http://www.mythtv.org/docs/mythtv-HOWTO-22.html#ss22.2
>
>
Thanks for the info.

In summary, I'd have to recompile MythTV with debugging support
enabled. Is it feasible to compile the myth source and replace the
mythbackend binary that was installed from RPM with a mythbackend binary
compiled with debugging support enabled? Or would I have to go the
whole hog and do "./configure --compile-type-debug && make && make install"?

Steve.

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mtdean at thirdcontact

Jul 3, 2008, 9:32 AM

Post #7 of 8 (412 views)
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Re: Please help! My mythbackend started to crash sporadically [In reply to]

On 07/03/2008 12:25 PM, lists_mythtv_users wrote:
> Joe Ripley wrote:
>
>> On Thu, Jul 3, 2008 at 2:14 AM, lists_mythtv_users wrote:
>>
>>> There have been several great responses on this topic detailing how to
>>> diagnose a hardware fault. Can anyone suggest how to help diagnose a
>>> software fault? Is there a way to capture useful information from a
>>> backtrace that could be passed on to a myth/kernel/driver developer in
>>> order to give them some insight into some code that can be improved?
>> When it comes to Myth:
>>
>> http://www.mythtv.org/docs/mythtv-HOWTO-22.html#ss22.2
> Thanks for the info.
>
> In summary, I'd have to recompile MythTV with debugging support
> enabled.

Depends on your distro.

> Is it feasible to compile the myth source and replace the
> mythbackend binary that was installed from RPM with a mythbackend binary
> compiled with debugging support enabled? Or would I have to go the
> whole hog and do "./configure --compile-type-debug && make && make install"?

Many distros make debug symbols available as a package. See your
friendly #ubuntu-mythtv or ATrpms forum or ... users for help.

Mike
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lists_mythtv_users at bigpizza

Jul 3, 2008, 10:09 AM

Post #8 of 8 (412 views)
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Re: Please help! My mythbackend started to crash sporadically [In reply to]

Michael T. Dean wrote:
> Is it feasible to compile the myth source and replace the
>> mythbackend binary that was installed from RPM with a mythbackend binary
>> compiled with debugging support enabled? Or would I have to go the
>> whole hog and do "./configure --compile-type-debug && make && make install"?
>>
>
> Many distros make debug symbols available as a package. See your
> friendly #ubuntu-mythtv or ATrpms forum or ... users for help.
>

OK, I found a mythtv-debug package for OpenSUSE 10.3 that I have just
installed. I've looked at the contents of the rpm, there are several
files such as /usr/lib/debug/usr/bin/mythbackend.debug,
.../bin/mythcommflag.debug, .../bin/mythfilldatabase.debug, etc. Are
these builds of the binaries with debugging support enabled or symbols
files? /usr/bin/mythbackend is 1.4M in size and
/usr/lib/debug/usr/bin/mythbackend.debug is 9.0M in size, I looked at
both in vi and both seem to be ELF files since the characters ELF are
very near the top of the file. However,
/usr/lib/debug/usr/bin/mythbackend.debug doesn't have any of the execute
flags set and following the instructions at
http://www.mythtv.org/docs/mythtv-HOWTO-22.html#ss22.2 I issued the
following command:

gdb /usr/lib/debug/usr/bin/mythbackend.debug -x gdbcommands

and got the following output:

GNU gdb 6.6.50.20070726-cvs
Copyright (C) 2007 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This GDB was configured as "x86_64-suse-linux"...
Using host libthread_db library "/lib64/libthread_db.so.1".
/bin/bash: /usr/lib/debug/usr/bin/mythbackend.debug: Permission denied
/bin/bash: line 0: exec: /usr/lib/debug/usr/bin/mythbackend.debug:
cannot execute: Success

Program exited with code 0176.
warning: Unable to find dynamic linker breakpoint function.
GDB will be unable to debug shared library initializers
and track explicitly loaded dynamic code.
/home/higgers/gdbcommands:6: Error in sourced command file:
You can't do that without a process to debug.

If /usr/lib/debug/usr/bin/mythbackend.debug is a symbols file then I
guess I need to find out of /usr/bin/mythbackend was compiled with debug
support enabled and if so then I need to adjust /etc/init.d/mythbackend
to start mythbackend via gdb. Would that be the correct thing to do?

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