[Jackit-devel] Re: [linux-audio-dev] 2.4.20 + lowlat +preempt + alsa + jack = dead computer

[Fernando Pablo Lopez-Lezcano]

> >So I run that in a terminal and after playing around with a bunch of
> >jack apps got the machine to lockup... and then, after a little bit,
> >suddenly, it came back to life! (you could see that the monitor had
> >changed the priority of the hogs to SCHED_OTHER). 
> >
> >So I guess that somehow jack has a hard to trigger race condition that
> >locks up the machine when running SCHED_FIFO.
> >
> >Now I have to figure out how to trace the thing so as to determine where
> >the whole thing is locking. Help from the jack gurus appreciated. 
> 
> what do you want to know? 

Ahem, everything? :-) ;-) :-)

> can you get roger's tool to tell you which
> process (PID) is hogging the CPU? is it jackd or a client? 

I just tried it and it appears to be both (which is consistent with what
I got with the kernel debugger, I was breaking into it and the only
processes I ever saw were jackd or one of the clients). 

I was running jackd, ardour, freqtweak, qjackconnect, ams, and an
additional process doing disk i/o that pushed things over the edge.
After rt_monitor kicks in it does print pids, but I just discovered that
for some reason ps axuw is not printing all the processes (seems to miss
the SCHED_FIFO ones - never noticed this before) so it is hard to track
what is what. The SCHED_FIFO jackd process is downgraded to SCHED_OTHER,
plus a bunch of client processes. Only jackd and ardour survive after
the freeze, all other clients die or are killed (just made it happen
again, this time with only jack and ardour).

-- Fernando