ChucK Jack correctness (Formerly: Re: [linux-audio-dev] [semi-OT] EEL 0.1.0 + ChucK)

[Lee Revell]

On Tue, 2005-01-11 at 13:09 -0500, Dave Robillard wrote:
> After some investigation, yes it is.  The RtAudio driver locks a mutex
> right in the Jack process callback - it doesn't look like it's designed
> correctly for Jack.
> 
> Offending lines are in RtApiJack::callbackEvent.  I may just write a
> direct Jack driver for ChucK though - cut out the middle man.  This
> RtAudio has a lot of code in between the jack callback and ChucK which I
> don't think is necessary, and it would be much simpler to verify ChucK
> isn't doing naughty things if it used Jack directly.

There is a feature in Ingo's RT preempt patchset that allows you to do
userspace atomicity debugging.  I believe recent CVS versions of JACK
detect this automatically and build in support for it.

With this feature if your JACK client does anything non-RT safe (IOW
anything that could schedule()) you get a "scheduling in user-atomic
context" message with a stack trace.

The first time anyone tried it, using Hydrogen, it immediately revealed
a bug where they had used a non RT safe QT call in process().

Lee