[mythtv-users] Backend crashes, sometimes with memory faults

Tero Mäntyvaara termant at gmail.com
Sun Dec 28 19:09:44 UTC 2008

Michael T. Dean wrote:
> On 12/23/2008 05:19 AM, Kenan Ezal wrote:
>> I recently built a new 64-bit dual-core myth master backend and frontend
>> box. The hardware for my old box was getting a little unreliable and
>> difficult to replace. While the old system (Fedora 6, Myth 0.20, 32-bit,
>> Intel Monterrey 1700 MHz) was very stable (except for the motherboard
>> dying on me recently), the new system has a serious problem that I've
>> been trying to (unsuccessfully) diagnose for about a month: Basically,
>> the backend dies without warning, sometimes taking out the frontend with
>> it. Although I can't prove it, it seems to be related to deletes and
>> maybe even mysql/mythconverg. However, there is sometimes a delay
>> involved.
>> My system information is:
>> Linux MythTV2 #1 SMP Thu Nov 13 20:29:07 EST 2008
>> x86_64 x86_64 x86_64 GNU/Linux
>> Dual core CPU E2180 @ 2.00GHz with 3.9GiB
>> My video partition is a RAID 5 with an ext3 filesystem.
>> I know that people have reported problems deleting with ext3, but with
>> my old machine, which had slower hard drives, ext3 was the only
>> filesystem that I did NOT have any problems with. Other filesystems
>> would often crash my entire system. The current problem seems to be
>> limited to mythtv -- at least the system doesn't crash.
>> The new machine does have SATA drives so I'm considering changing to
>> another filesystem, however, I thought I would see if anyone else can
>> think of something else that might going on before I commit to such a
>> move.
>> One thing that I thought could be the problem related to the message
>> almost always found in mythbackend.log just before a crash:
>> GetRecordBasename found no entry
>> I've gone through and manually tried to clean
>> mythconverg.recorded/.recordedprogram and hoped that would solve the
>> problem. I didn't help, but I'm not sure if I was successful in finding
>> the reason for the above message. I did find at least one entry that did
>> not have a matching file. But as far as I could tell, all database
>> entries matched my video directory contents after my spring cleaning. Is
>> there a way to check this with higher confidence? (I've also used
>> mysqlcheck without success -- everything seems OK). Maybe I need to
>> revisit this...
>> The only other solid clue I have is that sometimes I get a memory faults
>> (both mythfrontend and mythbackend, but mostly mythbackend). 
>> Otherwise, my observation is that there is a higher probability of a
>> crash if I've just deleted one or more recordings. I know there is a
>> "slow delete" feature (that I used to be able to control with 0.20), but
>> I'm not sure if it could case a delayed crash due to deletes.
>> Anyway I'm providing a couple of samples of my mythbackend.log and
>> mythfrontend.log in the hopes that someone will have a eureka moment. In
>> one case I also caught a mythfrontend memory corruption. All memory
>> faults/corruptions appear to have mysql libraries involved. 
>> I appreciate you reading even this far!
> ...
>> There are more but I will spare you.
>> I have saved all these logs if anyone thinks they might be of some use.
>> Thanks again.
> My first guess--assuming no hardware problems, such as bad 
> memory/overheating (I had a mobo where the chipset would overheat, 
> causing similar issues)/too-aggressive-overclock) would be a problem 
> with the installation.  I'd recommend removing /all/ of myth 
> (mythtv--including mythbackend, mythfrontend, mythfilldatabase, 
> etc.--and mythplugins at least).  Do a backup first, too.  ( 
> http://www.mythtv.org/wiki/index.php/Database_Backup_and_Restore )  
> Then, once you've removed everything using your package manager, make 
> sure nothing is left (i.e. check for and remove files from 
> /usr/{,local/}lib/{libmyth,mythtv} and /usr/{,local/}include/mythtv ).  
> Then, re-install (and restore the database, if necessary).
> If that doesn't help, we'd need a full backtrace to find out why things 
> are segfaulting.  http://mythtv.org/docs/mythtv-HOWTO-22.html#ss22.2  
> Note, though, that Fedora and Ubuntu both have packages that contain all 
> the debug symbols, so there's no need to rebuild mythtv--just 
> (temporarily) install the proper debug packages.  Talk to someone who 
> uses your distro to find out how.
> Mike
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I have had similar symptons in my 1,5 years old dual core 64-bit system.
I am using Ubuntu 8.10 based systems. I have MBE (Mythbuntu) having
mythtv filesystem on other system (Ubuntu server) by CIFS/SMB. I had NFS
before CIFS but kernel based NFS system had weird problems. Mythtv
filesystem is XFS. Database is also in the system that has Ubuntu server.

Tero Mäntyvaara

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