[mythtv-users] a new type of error

James Abernathy jfabernathy at gmail.com
Fri Mar 9 04:06:17 UTC 2018

> On Mar 8, 2018, at 8:30 PM, Stephen Worthington <stephen_agent at jsw.gen.nz> wrote:
> On Thu, 8 Mar 2018 18:31:37 -0500, you wrote:
>> I’ve setup my mythtv backend to daily optimize and backup the database.  I have it email me with the results.  So when I don’t get the 2 emails at 7:35am each day, I go looking for problems. The system still records problems and the frontends work for viewing.
>> What I’ve seen lately is I can’t ssh or login at the PC console of the backend, and I get errors on the console like:
>> Mar  7 12:11:47 mythbuntu kernel: [317584.873671] NMI watchdog: BUG: soft lockup - CPU#4 stuck for 22s! [TFWWrite:25774]
>> Mar  7 12:12:15 mythbuntu kernel: [317612.872998] NMI watchdog: BUG: soft lockup - CPU#4 stuck for 23s! [TFWWrite:25774]
>> Mar  7 12:12:55 mythbuntu kernel: [317652.872033] NMI watchdog: BUG: soft lockup - CPU#4 stuck for 23s! [TFWWrite:25774]
>> Mar  7 12:13:23 mythbuntu kernel: [317680.871359] NMI watchdog: BUG: soft lockup - CPU#4 stuck for 22s! [TFWWrite:25774]
>> The Host name is mythbuntu.  It’s a Ubuntu 16.04 system
>> Once I reboot, the system works fine and I get my optimize emails after a short time.  But a day or so later I notice this problem again.  I have not changed anything, but I have done some updating using:  apt update and apt upgrade.
>> Any ideas??
>> Jim Abernathy
>> jfabernathy at gmail.com
> Is there any more context in the logs?  Googling suggests that
> TFWWrite is in mythbackend in ThreadedFileWriter.cpp.  I would have
> hoped there might be a backtrace logged when the first error happened.
> You should also check to make sure you have plenty of free disk space
> to optimize_db to use.  You need to have enough free space for copies
> of the files for the largest table in your database to be make.  The
> largest table is always recordedseek.  What do these commands show:
> ll -h /var/lib/mysql/mythconverg/recordedseek.M*
> df -h /var/lib/mysql/mythconverg

-rw-rw---- 1 mysql mysql  12M Mar  8 23:00 recordedseek.MYD
-rw-rw---- 1 mysql mysql  16M Jan 20 13:49 recordedseek.MYD-180120142626.BAK
-rw-rw---- 1 mysql mysql  14M Feb  5 08:48 recordedseek.MYD-180205085856.BAK
-rw-rw---- 1 mysql mysql  11M Mar  8 23:00 recordedseek.MYI
jim at mythbuntu:~$ sudo df -h /var/lib/mysql/mythconverg
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1       451G  4.2G  428G   1% /
jim at mythbuntu:~$ 
> Here are mine:
> root at mypvr:~# ll -h /var/lib/mysql/mythconverg/recordedseek.M*
> -rw-rw---- 1 mysql mysql 5.8G Mar  9 14:14
> /var/lib/mysql/mythconverg/recordedseek.MYD
> -rw-rw---- 1 mysql mysql 5.3G Mar  9 14:14
> /var/lib/mysql/mythconverg/recordedseek.MYI
> root at mypvr:~# df -h /var/lib/mysql/mythconverg
> Filesystem      Size  Used Avail Use% Mounted on
> /dev/nvme0n1p4  100G   46G   50G  49% /
> So I need 11.1 Gibytes of free space available for optimize_db to
> work, but I have lots more than that.
> If you have had a free disk space problem, you may now have old
> temporary files in /var/lib/mysql/mythconverg that have been left
> behind and need to be cleared up.
> The automated database backups are one obvious culprit if you are
> running out of disk space.  If you are in a situation where you are
> accumulating more recordings, as your database grows, the backups also
> grow, and if they are still in the default /var/lib/mythtv/db_backups
> directory, their combined size will increase until there is
> insufficient free space for other things to work.  Rebooting then
> cleans out the files in /tmp which have been left behind when the disk
> filled up, and things can work for a few more days until space runs
> out again.  I have had this pattern happen a couple of times.
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