NEXTSOURCE Key stops mythfrontend accepting input

[Paul]

Problem: Press key Y (or current binding) to select NEXTSOURCE, and no further keyboard or lirc input is accepted from mythfrontend. It must be restarted.

Background: This was hidden until ​http://svn.mythtv.org/trac/ticket/6472 fixed the keybinding itself - the NEXTSOURCE binding previously went nowhere. The ticket discusses this problem but was unrelated to the original defect other than circumstantially.

mdean: Anyway, as far as the NEXTSOURCE issue, I'd need a good (with symbols) backtrace to say for sure, but I'm almost positive the problem exists in the TV::SwitchSource?() function and is unrelated to the keybinding fix (though the binding allows you to access that function). I plan to test it eventually, but if you can get a backtrace of the hung mythfrontend process, feel free to submit a separate ticket for the issue.

Tested in 23562, and a .22-fixes

[Dibblah]

Backtrace?

[Paul <mythtv@…>]

I haven't gone about getting a backtrace out of mythtv before, I'll look it up. Note that mythfrontend continues to work, and play the current channel being watched, so it doesn't crash as such - presumably I can still get a backtrace?

I just tested the telnet 6546 port and after NEXTSOURCE if I try a "key p" for example, it hangs.

[Paul <mythtv@…>]

Replying to Paul <mythtv@…>:

I haven't gone about getting a backtrace out of mythtv before, I'll look it up. Note that mythfrontend continues to work, and play the current channel being watched, so it doesn't crash as such - presumably I can still get a backtrace?

I just tested the telnet 6546 port and after NEXTSOURCE if I try a "key p" for example, it hangs.

The telnet session hangs btw, mythfrontend itself carries on with the current playing show.

[Paul <mythtv@…>]

The http://www.mythtv.org/wiki/Debugging page only refers to getting a backtrace by having the debugging symbol versions installed when a crash happens.

Mythtv doesn't crash in this instance - is there any more information I can provide that would help?

[robertm]

Paul,

You should be able to attach to the mythfrontend process using gdb and produce a trace otherwise as indicated in the manual. Get to the locked behavior, open a terminal, do a "ps aux |grep mythfrontend" to get the pid, run gdb, and attach with "attach $pidnumber", then get a backtrace.

(forgive any flubs in those instructions, working from memory)

[robertm]

BT from Jafa at SiliconDust

[sphery]

(In [24274]) Fix a deadlock in TV::SwitchSource() that occured when using the NEXTSOURCE/PREVSOURCE key bindings to switch sources.

The code in TV::timerEvent() was holding a lock, causing a deadlock when TV::SwitchSource() requested the PlayerContext. This changes TV::SwitchSource() to work like the related TV::SwitchCards() and TV::ToggleInputs functions by using the PlayerContext that TV::timerEvent() passes through TV::ProcessKeypress() and, finally, to TV::ActivePostQHandleAction(), which calls TV::SwitchSource().

This seems to have been broken in the mythtv-vid branch, but the code was unreachable/untestable due to broken key bindings (which were fixed for #6472).

Refs #6472. Fixes #8190. Thanks to jafa for finally getting a backtrace.

[sphery]

(In [24728]) Fix NEXTSOURCE/PREVSOURCE key bindings. Backports [24274] from trunk. Refs #8190.