[mythtv-users] backend crashes

junk junk at giantblob.com
Wed Jan 31 22:27:20 UTC 2007

Bruce Taber wrote:
> On Wed, 2007-01-31 at 22:03 +0000, junk wrote:
>> Hi,
>> My backend seems to be going through periods where it repeatedly dies 
>> and I'm not sure how to determine the cause of it. Sometimes it'll run 
>> fine for a day or two and I can make a number of scheduled recordings 
>> and/or watch live-tv, other times it'll die on me without warning, 
>> sometimes several times an hour. I don't get much indication in the log 
>> beyond seeing 'Starting up as the master server.' as it restarts after 
>> (presumably) crashing.
>> Firstly, is there any way to force it print a backtrace when it dies? 
>> It's running as a service started by init - does anyone know how to edit 
>> the Gentoo /etc/init.d/mythbackend script to start it under gdb safely 
>> and generate a backtrace on a fatal signal without requiring any user 
>> input (so when it suddently dies at 3AM, I don't need to be there to 
>> watch it!)
>> Secondly, can anyone hazard a guess at possible causes?
>> Things that might be relevant:
>>   - I'm running a single tuner dvb setup on a vanilla kernel
>>   - my dvb reception is poor but backend crashes don't seem particularly 
>> correlated with periods of particularly poor reception/bursts of errors 
>> in the received MPEG2 stream - sometimes I can record hours of 
>> programming with masses of reported errors in the stream and visible 
>> glitches, other times the back end will die repeatedly with no reported 
>> errors in received stream.
>>   - I've tried messing with PCI latencies, but put them back to defaults 
>> when it didn't seem to help
>>   - I have mythcommflag running sometimes, I suspect it might be 
>> contributing to the problem - is this possible?
>>   - All my filesystems are XFS, so autoexpire delete storm is not a 
>> likely cause?
> Check into the usage of XFS further. There is a noted problem with XFS,
> LVM, and sizes of partition > something. I don't know what that
> something is. I was having these types of problems and worse. The worse
> was that my system would unexpectedly hang completely. Couldn't ssh it
> and couldn't see the console. I finally set it up so the console
> wouldn't blank and caught some error messages. Sure enough XFS was
> peppered all around in the messages.
> My one video partition was XFS. That was cleared of all recordings and
> files and reformatted to EXT3. All of the crashes, hangs, and mysterious
> behavior has been eliminated.
I'm not seeing anything specifically about XFS from dmesg or in the 
backend log file - where should I look for XFS related messages?

-- jeek
>>   - Machine has loads of memory (2GB) and 1.8GHz A64 CPU (in 32bit mode) 
>> - I doubt it's overloaded recording one dvb stream
>>   - Single ATA disk has bus to itself and DMA is definitely enabled
>>   - CPU, northbridge, memory and disk are all cool and I don't believe 
>> the hardware is flakey (it's previously been running quite heavy Linux 
>> loads without any odd behavior before being repurposed as my MythTV box)
>> Any suggestions gratefully received, thanks
>> -- jeek
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