This is a bit more complex than you might think. Jack's thread
management is very unflexible and insists on controlling the entire
thread life cycle, only calling into client code in very few
occasions.

Of course it would great if JACK would be more flexible with its RT
loop handling. What I am missing is basically a way to
asynchronously/lock-free trigger execution of a callback function in
the RT loop at a suitable place. By a "suitable place" I mean that the
RT loop delays execution of this callback until a time where its
impact would be minimal, i.e. right after a completed process() and a
quick verification that the next process() cycle is still a bit away.