[mythtv-users] **Update - FIXED** mythbackend not responding - and even more weirdness

Bill Arlofski waa-mythtv at revpol.com
Wed Dec 27 16:34:08 UTC 2006

Ryan Duffy wrote:
>> Thanks to |Torg|, kormoc and others in the #mythtv-users IRC channel it
>> seems we found a possible cause and at least a quick fix.
>> I am no kernel hacker, but |Torg| pointed me to this:
>> http://lkml.org/lkml/2006/4/12/64 , along with the thought that there is
>> or may be timing issue between the two cores which was causing
>> Mythbackend to stop responding.
>> Disabling SMP support in my 2.6.18 "vanilla" kernel (gentoo-speak) on
>> this AMD Athlon64 X2 dual core system seems to have cleared up the
>> problem I originally described where the Mythbackend randomly stopped
>> responding to the frontend(s).
>> It has been running for almost 48 hours now, recording, commflagging,
>> transcoding and talking to multiple frontends, including mythweb - so
>> far no issues to report since SMP was disabled.
> So, let's get this straight - you've "fixed" a mythtv threading issue by disabling one of the cores of your dual-core CPU? 

Thanks for the comment Ryan.

The point of my follow-up post was not to say that I somehow magically
fixed mythtv or the actual problem, but rather that I found what appears
to be the cause and (for now) a temporary solution to the problem that
was plaguing me which no one could offer any insight into. As a matter
of fact, looking back, that is exactly what I said:

"Thanks to |Torg|, kormoc and others in the #mythtv-users IRC channel it
seems we found a possible cause and at least a quick fix."

Perhaps a *PROBLEM ISOLATED, WORKAROUND FOUND* follow-up subject would
have been more clear. :)

I posted the follow-up comment with *FIXED*" in the subject in order to
hopefully generate some "hmmm, that's interesting, let's see what can be
done about really fixing the issue" type comments from any of the devs
that might be following the mythtv-users list. Also as a help to anyone
else that might be experiencing a similar issue on similar hardware.

Besides, I was excited to finally see mythtv running consistently on
this system and wanted anyone who may have been following the thread
that some progress had been made in my situation.

So having said all of that, were exactly is the problem? I don't know.

Is it strictly within the realm of the Linux kernel hackers'
responsibility to fix this? If yes, who's responsibility is it to report
it to them? Surely not an end user of a program. I'd hope a dev would
handle that type of escalation. :)

Does any of the burden of this problem fall on the mythtv devs? Is it a
programming issue with Mythtv and SMP? Is it an AMD Athlon64 X2 SMP
issue specific to the CPU I am using? Again, I do not know.

Not being a developer, I just try to report what I see in the hopes that
someone skilled in this area will pick up the ball and know exactly
what/where the problem lies, or will ask me for more information to get
to the bottom of it all.

> I very strongly suspect you've simply made it less likely to occur...

Well, 6 days, 17 hours and 59 minutes - still running, still responding.
I am pretty happy with that for now. :)

With an SMP-enabled kernel mythbackend failure is immanent - usually
within minutes or a few hours - It probably depends on if/when
recording/commflagging/transcoding is taking place. Never had the chance
to specifically narrow that down. Disabling SMP was the first course of

Happy Holidays!

Thanks again to the MythTV devs.

Bill Arlofski
Reverse Polarity

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