[mythtv-users] dd hangs in HDPVR channel changer script

[Andrew Codrington]

Hi all,

I've been using my HDPVR for years and for the last 4 or 5 it's been
working very well.

Recently something changed somewhere and recordings have not been
happening. Mythbackend doesn't show any complaints about the HDPVR recorder
being offline or in error state, it just stops recording new programs.
Everything else works fine.

Digging in a bit I can see that I've got a hung dd process coming from my
channel changing script as found here -
https://www.mythtv.org/wiki/Hauppauge_HD-PVR

This is the command from that script that I can see in my process list
(with variables expanded as expected):

timeout 2 dd if=${VDEV} of=/dev/null bs=4k count=1 1>/dev/null 2>/dev/null

I can't kill the dd process and it even seems to prevent a reboot cycle
from restarting. I have to power off the box before it will restart.

To work around this I've removed the STB power on detection section from
the channel changing script. It's only been a day, but so far things are
working.

I'm sharing partially as FYI in case others are having similar problems,
and partially in case there's an easy fix to resolve the dd hang.

Background:

My machine was originally a mythbuntu box which I upgraded to 16.04 not too
long before this problem started showing up.
I enabled HWE to get this patch so that my Vizio tv wouldn't die and not
come back after power saving kicked in:
Revert "drm/i915: Check live status before reading edid"
https://github.com/torvalds/linux/commit/23f889bdf6ee5cfff012d8b09f6bec
920c691696

andrew at mythbackend:~$ uname -a
Linux mythbackend 4.13.0-36-generic #40~16.04.1-Ubuntu SMP Fri Feb 16
23:25:58 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
andrew at mythbackend:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04.4 LTS
Release: 16.04
Codename: xenial
andrew at mythbackend:~$ mythbackend --version
Please attach all output as a file in bug reports.
MythTV Version : v0.28.2
MythTV Branch : fixes/0.28
Network Protocol : 88
Library API : 0.28.20161120-1
QT Version : 5.5.1
Options compiled in:
 linux profile use_hidesyms using_alsa using_oss using_pulse
using_pulseoutput using_backend using_bindings_perl using_bindings_python
using_bindings_php using_crystalhd using_dvb using_firewire using_frontend
using_hdhomerun using_vbox using_ceton using_hdpvr using_ivtv
using_joystick_menu using_libcec using_libcrypto using_libdns_sd
using_libfftw3 using_libxml2 using_lirc using_mheg using_opengl
using_opengl_video using_opengl_themepainter using_qtwebkit using_qtscript
using_qtdbus using_sdl using_taglib using_v4l2 using_x11 using_xrandr
using_xv using_profiletype using_bindings_perl using_bindings_python
using_bindings_php using_freetype2 using_mythtranscode using_opengl
using_vaapi using_vdpau using_ffmpeg_threads using_mheg using_libass
using_libxml2


Cheers,
Andrew
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