[PlanetCCRMA] guaranteed deadlock w/ 2.4.20-4.ll.acpi

Marc Heckmann mh@nadir.org
Wed May 14 13:29:01 2003

On Wed, May 14, 2003 at 01:18:38PM -0700, Fernando Pablo Lopez-Lezcano wrote:
> > > Is this only happening with ecasound? (and only with two copies running
> > > at the same time?) Or do you see the problem with other jack software as
> > > well?
> > 
> > no, I managed to crash it a couple of times before, while using a
> > arecord and jackrec simultaneously. When that happened, jackrec and
> > arecord were being run without privilieges, but jackd was running with
> > the "-R" (realtime) switch
> That is strange. You should not be able to run arecord and jackrec at
> the same time. Jackd monopolizes the alsa device so arecord should find
> it busy (and eventually timeout?). 

I was running arecord using the jack plugin:

arecord -f cd -D jackplug -t wav

> Roger Larsson sent me a small app to monitor SCHED_FIFO processes and
> downgrade them to normal schedulling when they start eating all the cpu
> for a (programmable) time. It was very useful when I was having lock up
> problems (in that case due to a problem in ext3). The machine would lock
> up for 5 seconds and then magically I would get control again :-) I'm
> adding the files as attachments to this email. 

ok, I'll give them a spin.

> > > Yuck. It sounds like an infinite loop on a SCHED_FIFO process (ie:
> > > anything interrupt related may work but no processes get to be
> > > schedulled at all other than the realtime process sucking up all cpu
> > > cycles). But you mention that it also happens when you run as a normal
> > > users with no special privileges so that should not be the problem. 
> > 
> > no, something has to be running with priviliges. In the case I
> > described, jackd was running un-priviliged, 
> Meaning as root but without "-R"?

no, without "-R" and as an un-priviliged user.

> > While my
> > system is UP, doesn't preempt use spinlocks? Does 2.4.20-4.ll.acpi have
> > preempt enabled?
> Yes. 

maybe I'll rebuild without it and see..