Scheduler deadlock during Live TV

[stichnot]

While watching live TV, got the popup indicating that the backend wanted the tuner for a scheduled recording. I clicked "OK" to let the scheduled program record. This resulted in an apparent deadlock in the scheduler code. (To be precise, the scheduler wanted a different tuner but in the same input group as the Live TV tuner.) The deadlock manifested itself as mythfrontend and mythweb connection attempts hanging.

I attached gdb to the mythbackend process and got a stack trace.

Also including some backend logs with "-v most --loglevel debug". To make the size manageable, I filtered out lines containing "TFW" or "JobQueue?", and I removed lines prior to 1 minute before the recording. (But I kept the first 100 lines to show version and startup information.)

[stuartm]

Can you test the following patch? ​http://pastebin.ca/2162527

[David Engel <dengel@…>]

In ca273324961b95e300890ed40e833249b5460bd8/mythtv:

Hopefully remove more scheduler/recorder deadlocks.

Change the scheduler to unlock schedLock when calling the recorder
synchronously. If the recorder happens to be calling the scheduler at
the same time, this allows the recorder's call to grab the lock as
needed.

Fixes #10647, #10770 and #10771 .

[David Engel <dengel@…>]

In 4386e90e25ed40948bb208e8a325a8b072411e88/mythtv:

Hopefully remove more scheduler/recorder deadlocks.

Change the scheduler to unlock schedLock when calling the recorder
synchronously. If the recorder happens to be calling the scheduler at
the same time, this allows the recorder's call to grab the lock as
needed.

Refs #10647, #10770 and #10771 .
(cherry picked from commit ca273324961b95e300890ed40e833249b5460bd8)

Conflicts:

mythtv/programs/mythbackend/scheduler.cpp