[mythtv-users] FC5 crashing with newly installed 0.20

Jonas Anden jonas at anden.nu
Fri Oct 20 08:06:06 UTC 2006

Hi Jay (and everyone else listening),

I know it was a while ago since you mailed out about your problems with
mythbackend crashing during EIT scanning. Did you get these problems
resolved? If so, how? If not, what DVB card(s) are you using?

I think I've got the same issue with my Nova-T 500 (DVB-T dual tuner).
It is a PCI board with an on-board USB controller attached to two DiBcom
0700 tuner chips.

I have noticed that during these crashes when myth is scanning for EIT
data, it does not seem to close all demuxers, and when the number of
open file handles related to the tuner chip reaches 22, the card seems
to do a USB disconnect/reconnect, which in turn causes an kernel Oops
(since the dvb-usb drivers don't handle USB disconnection while it is
"in use"). I don't know if this is a fault management operation, or if
it is some kind of buffer overrun that causes the disconnection (haven't
looked at the code yet). Sometimes this results in the box freezing up,
sometimes it just goes on but can't record DVB (which is worse, since
the scheduler then does not take action to reschedule the shows using
the analog tuners on my primary backend).

Looking at open files while running, mythbackend is using the frontend
constantly. I have two tuners, so I see /dev/dvb/adapter0/frontend0
and /dev/dvb/adapter1/frontend0. When a recording starts, mythbackend
uses 7 open files for this -- 1 for frontend0, 1 for 'dvr0', and 5(!)
for the demux0 device. The EIT scanner does this similarly, but when
done it does not always close the demux0 device, leaving them open after
the operation has completed.

I'll take a look at the code for the EIT scanning this weekend to see if
I can spot what is leaving the demux0 device open.

  // J

More information about the mythtv-users mailing list