[mythtv-users] Frontend locking up and unable to kill it.

[Stephen Worthington]

On Wed, 3 Jul 2019 17:44:59 -0700, you wrote:

>Twice now the frontend has frozen. If that were not bad enough, I am unable
>to kill it. I have remotely tried to kill it and what I find is a status
>message on the main screen saying the program has become unresponsive and
>do I want to shut it down.  But with no visible cursor I cannot click on
>"Yes" and it does not respond to "Y" from the keyboard. I did a "sudo
>shutdown now -r" from the remote and the link was immediately cut but the
>myth computer did not shut down. It is as if mythfrontend was blocking all
>attempts to close it. I finally held the power button down long enough to
>turn the computer off and when I restarted it, all was fine. There is just
>a short section in the frontend log between when my wife started watching
>her show and the freeze. No log entries after the freeze until the restart.
>
>Jul  3 07:33:33 NewMyth mythfrontend.real: mythfrontend[1555]: I
>CoreContext tv_play.cpp:2532 (HandleStateChange) TV::HandleStateChange():
>Changing from None to WatchingRecording
>Jul  3 07:33:34 NewMyth mythfrontend.real: mythfrontend[1555]: I
>CoreContext tv_play.cpp:2638 (HandleStateChange) TV::HandleStateChange():
>Main UI disabled.
>Jul  3 07:33:34 NewMyth mythfrontend.real: mythfrontend[1555]: I
>CoreContext tv_play.cpp:424 (StartTV) TV::StartTV(): Entering main playback
>loop.
>Jul  3 07:33:34 NewMyth mythfrontend.real: mythfrontend[1555]: N
>CoreContext mythplayer.cpp:2231 (PrebufferEnoughFrames) Player(f): Waited
>101ms for video buffers AAAAAAAAAAAAAA
>Jul  3 07:33:34 NewMyth mythfrontend.real: mythfrontend[1555]: N
>CoreContext mythplayer.cpp:2231 (PrebufferEnoughFrames) Player(f): Waited
>203ms for video buffers AAAAAAAAAAAAAA
>Jul  3 07:33:34 NewMyth mythfrontend.real: mythfrontend[1555]: N
>CoreContext mythplayer.cpp:2231 (PrebufferEnoughFrames) Player(f): Waited
>305ms for video buffers LAAAAAAAAAAAAA
>Jul  3 07:33:34 NewMyth mythfrontend.real: mythfrontend[1555]: I
>CoreContext mythrender_vdpau.cpp:615 (CheckOutputSurfaces) VDPAU: Added 2
>output surfaces (total 4, max 4)
>Jul  3 07:33:34 NewMyth mythfrontend.real: mythfrontend[1555]: N
>CoreContext mythplayer.cpp:2231 (PrebufferEnoughFrames) Player(f): Waited
>102ms for video buffers dLAAAAAAAAAAAA
>Jul  3 07:35:29 NewMyth mythfrontend.real: mythfrontend[1555]: E Decoder
>mythplayer.cpp:3504 (DecoderGetFrame) Player(f): Decoder timed out waiting
>for free video buffers.
>
>Nothing here that means anything to me that tells me what happened or what
>to do.
>
>Ideally someone can help figure out what is causing the freezes but short
>of that, how can I shutdown the system?
>
> What I tried:
>sudo kill 1555
>sudo kill -9 1555
> sudo killall  mythfrontend.re
> sudo shutdown now -r
>
>Nothing  above would kill the frontend.
>
>Allen

That sounds like something else other than mythfrontend was locked up,
like the kernel.  Check syslog.   When that happens, you can get a
complete lockup, or it can just make the system very slow, where it
takes an hour or two to shutdown.  The latter usually happens when one
or more cores of your CPU are locked up or "stalled" by the software
running on them.

What distro is it?  If it is Ubuntu, some of the "magic" keys are
enabled, so that in such a situation, you may be able to get the
filesystem shut down safely and force a reboot.  Try holding down the
Alt key, and the SysReq key (PrintScrn if there is no marked SysReq
key), and then with both those keys down, hit and release all these
keys in sequence, slowly, with a second or two between keys: REISUB.

See this page for what all those keys do:

http://www.ubuntugeek.com/how-to-use-magic-system-request-keys-in-ubuntu-linux.html

Note that the information on that page is for a very old version of
Ubuntu.  The O key (shutdown) does not work for some reason in modern
Ubuntus, so you need to use B and have it reboot, and then you can
shut it down when the BIOS display comes up if that is what you want.

You did manage a remote login - did that take longer than usual to
work?  Was it slow to respond to commands?

Another option is to enable the systemd debug console:

systemctl enable debug-shell.service

That creates a logged-in root shell on Ctrl-Alt-F9 that comes up early
in the boot process and does not go away until as late as possible on
shutdown.  It allows you to use Ctrl-Alt-F9 to see what is preventing
a shutdown by using "systemctl status" or "systemctl list-units", or
any other commands.  However, it is a big security hole as it allows
anyone who knows about it to use Ctrl-Alt-F9 to get root access while
it is enabled.

And remember that if you did not get the filesystem shut down properly
before you powered off or rebooted the PC, you must do a full
filesystem check (fsck -C -f) on all partitions that were mounted at
the time.  The easiest way to do that is to have a separate small boot
partition on the PC to do it from, so that you do not have the root
partition locked.  Or you can use a compatible live DVD or USB stick
to boot from - one that has the same or better level of filesystem
drivers.  Keep repeating the fsck -C -f command for each partition
until there are no more errors reported.