[mythtv-users] MySQL related BE deadlocks - collective wisdom needed

[David Edwards]

2011/7/25 Warpme <warpme at o2.pl>

> Pls find attached BE trace &  SHOW ENGINE INNODB STATUS\G from deadlocked
> BE (protocol version check deadlock).
>

A few thoughts based on those dumps. It is entirely possible that any of
these thoughts are misguided, since I know little about the code:

1. I don't see anything here suggesting this is a deadlock in MythTV; most
of the threads are waiting to get a lock, but I'm guessing that the lock is
being held by the thread trying to run the DB query, which is waiting on the
database rather than waiting on a lock in the Myth code. Maybe this is a
terminology issue, but I think it makes a difference in terms of the
possible causes.

2. The thread trying to query the database is hanging while preparing a
statement rather than executing one. The database appears to be idle, unless
I'm misinterpreting the output or if you have some tables that are not
InnoDB. Thus the database does not appear to be blocking due to locks.

3. The thread trying to run the DB query (0x98eafb70 = 2565536624) does not
appear in the list of threads in the DB status output. Again, I may be
misinterpreting the output, but if I'm correct then the thread is trying to
prepare a query on a connection that no longer open.

No idea if any of that is helpful...

David
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.mythtv.org/pipermail/mythtv-users/attachments/20110726/879d78e2/attachment.html