[LAU] JACK hanging upon slight USB power glitch

Sorry if this is an obvious question, but I'm short of time today and
really tired of Google searching.

I'm running:

Linux dlm-A6200 3.2.0-54-lowlatency #56-Ubuntu SMP PREEMPT Thu Sep 19
17:22:47 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

I have jack 2 connected via ALSA to an M-Audio Fast Track Pro.

If there is any slight glitch in the USB power -- for instance, in a
performance space where the sound engineer might need to plug/unplug cables
frequently -- jackd spins out of control on one CPU and often locks up the
user interface, forcing a hard shutdown and reboot. If I'm very lucky, I
can get into the terminal, find jack's PID and kill it, but when the mouse
and keyboard stop responding, there's nothing I can do reach for the power
button.

This occurs less frequently in 12.04 than it did when I started with 10.04,
but when it does happen (as it did just now), it really, really ticks me
off.

I think there must be some automated way for the system to recognize that
jack is out of control and kill it. [1] notes:

       -t, --timeout int
              Set client timeout limit in milliseconds. The default is
500
              msec. In realtime mode the client timeout must be smaller
than
              the watchdog timeout (5000 msec).

Interesting... "watchdog timeout"... but I have never seen any effect from
the watchdog mentioned here. Jack just keeps locking up the system for way
longer than 5 seconds.

I'm happy to provide more info if you can tell me what commands to run.
Normally I would research it myself, but I'm just not in the mood today. If
there's already good documentation on this, great, but... too many pages to
read and I have no idea which is the best one.

Thanks,
hjh

[1] http://manpages.ubuntu.com/manpages/precise/man1/jackd.1.html
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Received on Mon Oct 14 16:15:01 2013