[mythtv-users] recent mythbackend crashing

David Engel david at istwok.net
Thu Jun 2 15:57:52 UTC 2022


On Thu, Jun 02, 2022 at 09:26:27AM +1000, Eyal Lebedinsky wrote:
> 
> 
> On 01/06/2022 09.06, David Engel wrote:
> > On Tue, May 31, 2022 at 10:32:17PM +0000, Gary Buhrmaster wrote:
> > > On Tue, May 31, 2022 at 7:28 PM Klaas de Waal <klaas.de.waal at gmail.com> wrote:
> > > 
> > > > What is a bit strange is that you get the abort signal. Usually we get the segmentation fault.
> > > 
> > > (g)libc (and other libraries) will SIGABRT due to various
> > > "critical" errors, which all too often tend not to be anywhere
> > > near the actual root cause (which is why the extended
> > > mythtv logging and a full bt is probably going to be required).
> > 
> > I can confirm that.  I had some occasional, but frequent enough to be
> > very frustrating, crashes over several months that I finally tracked
> > down to glibc aborting due to the process exceeding the default limit
> > on open, file descriptors.
> > 
> > David
> 
> I am running for over a day with EIT enabled and [Service] includes:
> 	Type=simple
> 	Environment=MYTHCONFDIR=/etc/mythtv
> 	User=mythtv
> 	ExecStart=/usr/bin/mythbackend --logpath /var/log/mythtv -v channel,eit --loglevel=debug	# added '-v ...'
> 	Restart=always		# new line
> 	LimitNOFILE=16384	# new line
> 
> The last 3 lines were changed/added recently.
> 
> Tonight, after more than a day, I had the first crash (see log below) when the backend was idle.
> Same lines in mythbackend log and system messages.
> 
> I do not see anything unusuall, does anyone else?
> 
> I will now disable EIT (and the debug options) until the next experiment.

The next thing to do is enable full, core dumps.  Be sure to set the
ulimits so that you get the entire process dumped.  I think some
things default to only dumping 2 GB or so.  To eventually diagnose my
problem, I also had to install the Debian, -dbg packages with debug
symbols for libraries like glibc and Qt.  I needed those when
inspecting the core dump with gdb to know exactly where glic was
aborting.

David
-- 
David Engel
david at istwok.net


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