[mythtv] FW: Ticket #10541: SIGSEGV when EIT updating DB and channel change

[Daniel Kristjansson]

On Sun, 2012-04-15 at 18:52 +0200, Angela wrote:
> No crashes anymore. However I see mythbackend hanging, which I have seen in
> the past also without this patch. 

The hangs you reported were the reason I didn't try to apply this before
the 0.25 release.

> During "EITCache: Wrote 14 modified entries of 252 for channel 1002 to
> database" messages, I think mythbackend comes unresponsive, this behaviour
> has been seen before, also without this patch.
> This time the recording has been canceled. In my previous comment, the
> recording started 1.5 minutes later.
> p.s. Why does MythTV not reuse prepared statements ? For each
> insert/update/delete as far as I have seen, the SQL command is prepared on
> each call. Why not preparing it once and reuse it. Sure needs some
> re-preparing when the connection has to be re-astablished. Writing 2000 EIT
> records needs 3 Minutes, which is in my eyes very long. This is on a Sandy
> Bridge 2600K.

I think the hangs and your slow database may be related. The non-reuse
of prepared statements is historic. The code was written when Qt didn't
support prepared statements. But even so your database seems to be
running like it's writing to a floppy and not a hard disk. What is the
formatting of the partition containing the database? If it is xfs or
ext4 does adding nobarriers to the mount fix the hanging?

-- Daniel