[mythtv-users] System crashes on start of DVB-S recording

[OCG Technical Support]

You'll likely get some negative feedback - sasc-ng is a "no no" on this
list...

 

Have you asked on the happysat forum?  A new ECM or code will lock sasc-ng.
While this shouldn't lock the system, it can cause the backend to freeze.

 

From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Jelte Veldstra
Sent: February 8, 2009 1:17 PM
To: Myth TV Users List
Subject: [mythtv-users] System crashes on start of DVB-S recording

 

This issue really drives me mad and I was wondering if others have
experienced the same.

I have built a dedicated backend based on CentOS 5 (with DVB support from
centos.plus kernels) and MythTV 0.21-fixes. It is currently fitted with two
Hauppauge Nova-S (budget) DVB-S adapters. Encrypted channels are decrypted
using open-sasc-ng and a subscription card in a phoenix smartcard reader.

This setup works quite well but every now and then (~ 1 in 100 recordings) I
have this setup hardlocking on me as a recording is started. After
restarting the system and looking into the logfiles there is nothing that
hints what happened that made it crash. It looks as if the power plug was
pulled as syslog shows nothing on the Linux level. The backend log only
shows the line that indicates a recording is started and nothing since. The
sasc-ng log shows no attempt of the backend connecting to it for this
recording. The system has had its share of stress tests to rule out memory,
power or overheating problems and has shown no such issues.

As MythTV and sasc-ng run as non-privileged users it seems like something is
going on on kernel and driver level. This thought is enforced as it only
seems to happen with stv0299 based adapters (such as the Nova-S). Having
used a single Twinhan 1030A DVB-S adapter (dvb-bt8xx based) for a while
never failed on me. And when I mixed both types (I really want a twin-tuner
system) it would occasionally crash on the Nova-S but never on the Twinhan.

So somehow it seems related to the hardware, but as I tried three different
stv0299 based tuners, it's not a faulty adapter is seems but rather a driver
issue. If I could find a second 1030A then I would try that for sure, but I
havent been able to find one, plus I'd really like to understand what's
going on here. Searching linuxtv.org mail archives doesn't provide answers
on that.

Googling for it revealed some possible hints. One suggestion was that it
could be multirec in combination with open-sasc-ng. Others have found that
multirec not being 100% working with open-sasc-ng but had no crashes. To
rule is out I have disabled multirec, but still have had crashes. Another
suggestion was that a race condition could arrise between software RAID5
code and the DVB subsystem (would explain why there are no kernel messages
during or after the crash). As I used soft RAID5 I have since removed that
configuration from my setup, but still no luck. 

So I have spent quite some time googling and trying out what I found there,
but no luck yet. I'm runnning out of ideas and wondered if other MythTV
users have had similar issues or found a pattern. So far I cannot reproduce
it and the only pattern so far is that it only happens at the start of a
recording (never during or outside recordings) and on stv0299 based
adapters.

If you recognise this or have any pointers for me to try, please share.

Thanks in advance,


Jelte

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