[mythtv-users] mythtv hard lockup

[Yeechang Lee]

David Rees <drees76 at gmail.com> says:
> My system does similar (FC5, Nvidia 9742 and previously 8776, ivtv
> 0.8.2 w/2 PVR-250s, latest mythtv from atrpms). It's been locking up
> for a while. When my system locks up, the computer responds to
> network commands (ping, can start a ssh session but never get a
> prompt), but it seems that any disk IO gets stuck as I can't get a
> shell. Seems to happen once a week or so.

These exact symptoms started happening to me a month or two ago on my
Pentium 4 3.0GHz Fedora Core 4 dedicated frontend+backend after almost
a year of reliable service. Same symptoms as yours; I'd advise you to
try logging into a console session ahead of time and then, at the next
crash, switching to it to see if you can a) do local-disk reads (by,
say, 'ls -la /'),
b) do network-disk writes (by, say, 'touch /mnt/remote/xyz123'), and
c) do local-disk writes ('touch /tmp/xyz23'). If you can do a) and b)
but
c) hangs the shell, you've got what I got. While fiddling with the
options available through the magic SysRq key, I saw many mysterious
"blocked by mutex" (or "blocked mutex," or something like that)
messages. While that meant and still means nothing to me, I presume
these blocks are what prevents local-disk writes from working.

Unfortunately, I don't have a complete soution to this problem, and I
am pretty sure it's not MythTV related per se. I began by thinking
that it was my self-rebuilt Fedora kernel, then the SATA cable, then
the local disk itself, replacing all three (and fiddling with pretty
much every other major and minor software component and option in the
process) with no luck. The hangs started occurring more often--as
quickly as an hour or two after bootup--and in desperation I rebuilt
the box
(<URL:http://www.gossamer-threads.com/lists/mythtv/users/240816#240816>),
only retaining my MythTV database backup for my recordings, along the
way taking the opportunity to move to 64-bit Fedora Core 6 (see my
followups to
<URL:http://www.gossamer-threads.com/lists/mythtv/users/238805#238805>).
This definitely helped, but I still see the same hangs with the same
symptoms every now and then. Once--just once--I *might* have been able
to cure it with repeated invokings of the magic SysRq key's emergency
sync option, but that's never worked again.

-- 
Yeechang Lee <ylee at pobox.com> | +1 650 776 7763 | San Francisco CA US