[mythtv-users] Hard frontend crash with vaapi on Ubuntu 20.04 and Mythtv 31

Klaas de Waal klaas.de.waal at gmail.com
Tue Jun 1 16:40:03 UTC 2021


What I do with a crashing frontend is to run it interactively in a gdb
session. If the failure is in mythfrontend then gdb catches it. If the
failure is due to a kernel crash, like in the driver, then this does not
work and the only option I see then is just trying all different driver
versions that you can find.

On Tue, 1 Jun 2021 at 17:52, OpenMedia Support <support at openmedia.co.nz>
wrote:

> > On Wed, 2 Jun 2021 02:16:28 +1200, you wrote:
> >
> >>>
> >>> On 6/1/21 7:05 AM, OpenMedia Support wrote:
> >>>>> On 6/1/21 3:38 AM, OpenMedia Support wrote:
> >>>>>> I'm running an Intel N3150 based NUC as a dedicated frontend for
> >>>>>> MythTV
> >>>>>> and it keep getting hard crashes during video playback with VAAPI.
> >>>>>> Id
> >>>>>> appreciate some guidance on how to best debug the problem.
> >>>>>>
> >>>>>> Hardware - Gigabyte Brix Intel N3150 / 4GB Ram / 120GB SSD
> >>>>>>
> >>>>>> OS - Ubuntu 20.04 LTS - regularly patched
> >>>>>>
> >>>>>> MythTV Backend - on different hardware with DVB-T and DVB-S cards
> >>>>>>
> >>>>>> MythTV Frontend - Lastest version from the PPA -
> >>>>>> http://ppa.launchpad.net/mythbuntu/31/ubuntu
> >>>>>>
> >>>>>> Video playback currently uses a custom VAAPI profile, but the out of
> >>>>>> the
> >>>>>> box VAAPI profile also has issues. It appears to occur when playing
> >>>>>> H.264
> >>>>>> based content. Our DVB-T FTA service is H.264 for both HD and SD
> >>>>>> material.
> >>>>>> It can occur when we're simply watching a show, and the video /
> >>>>>> audio
> >>>>>> freezes and I need to hard-reset the Brix hardware.
> >>>>>>
> >>>>>> I've configured for
> >>>>>>    - max_cpus = 3
> >>>>>>    - deinterlacer - low:shader:driver
> >>>>>>    - decoder - vaapi
> >>>>>>    - videorender - opengl-hw
> >>>>>>    - skiploop - 0
> >>>>>>
> >>>>>> I'll try and reproduce with "-v playback" enabled but at present
> >>>>>> there
> >>>>>> is
> >>>>>> nothing obvious in the frontend or system logs when the crash
> >>>>>> occurs.
> >>>>>>
> >>>>>> I'd really appreciate it if anyone else seen similar issues and
> >>>>>> could
> >>>>>> provide guidance.
> >>>>>
> >>>>> I have a NUC i7-1165G7 and it has Iris graphics.  I can't get
> >>>>> VAAPI
> >>>>> to
> >>>>> work at all. I have to use OpenGL low quality deinterlacing. When I
> >>>>> use
> >>>>> VAAPI it crashes with code 139. I can't run higher than low
> >>>>> deinterlacing because the pictures tears about 10% from the top of
> >>>>> the
> >>>>> screen.
> >>>>>
> >>>>> Luckily, I didn't buy the $800 NUC as a mythtv frontend only. Iris
> >>>>> GFX
> >>>>> and Mythtv aren't a good solution for sure.
> >>>>>
> >>>> The N3150 Brix was relatively cheap and generally makes quite a nice
> >>>> front
> >>>> end, and now it has an SSD is effectively silent.
> >>>>
> >>>> Just had a fresh hard crash with "-v playback" and all I can see is
> >>>> the
> >>>> following as I had an SSH session tailing the frontend logs.
> >>>>
> >>>> Jun  1 21:49:37 mythfe1 mythfrontend.real: mythfrontend[1900]: I
> >>>
> >>> Are you able to get into ssh to kill the frontend when it locks up? I
> >>> would say the thing to do is enable core files by setting the limit and
> >>> disabling Ubuntu crash logging, then when it happens run kill SIGQUIT
> >>> to
> >>> create a core dump which can be analyzed to see where the hang
> >>> occurred.
> >>
> >>Afraid not. This is a hard crash and I loose my SSH sessions. I've been
> >>running a couple of sessions to tail the mythfrontend and system logs and
> >>they become responsive until I reboot the hardware.
> >
> > Have you tried using the magic keys to see if you can get the
> > filesystem buffers to flush before rebooting?  Sometimes you can get
> > some log information that way.
> >
> > In /etc/sysctl.conf, put:
> >
> > kernel.sysrq=1
> >
> > to allow all the magic keys.  Run "sysctl --system" to reload the
> > sysctl.conf settings, or reboot.  Then when the next lockup happens,
> > hold down the Alt and SysReq keys, then with both down type this
> > sequence:
> >
> > REISUB
> >
> > If your keyboard does not have a SysReq key marked, it is also usually
> > the PrntScrn key.
> >
> > See here for what each keystroke does:
> >
> > https://en.wikipedia.org/wiki/Magic_SysRq_key
> >
> > The S and U are the critical ones - they sync and unmount the
> > filesystems.
> >
> > Your problem has the same characteristics as what I had when I first
> > installed my Nvidia GT1030 card.  In my case, it was an Nvidia driver
> > bug and it became much less common with a driver update in the same
> > series, and went away completely with a major driver update.
>
> Thanks for the tip. I've enabled the setting.
>
> I've also enabled the HWE kernel and switched from 5.4.0.73.76 to
> 5.8.0.53.60 to see if that will help
>
>
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