Maybe I'm sawing the same old violin, but...
I think the key to breaking out of the "incredibly difficult to program in
parallel" conundrum is to dump the baggage of the last couple of decades
and go back, not only to CSP, but also to elegant (small) OS constructs.
If OS size is in kilobytes, there's hope you can understand COMPLETELY
what it is doing, especially if the OS restricts itself to resource
loading and leaves run-time concurrency to applications.
The other thing is to accept a 5 or 10 percent performance hit in order to
keep clear, provable, traceable resource usage (i.e. eliminate spaghetti).
The "hit" is actually not a hit, because the cost of code tangles is
really much more; but if raw specs are applied, you can always do it just
a little faster by letting pointers and dynamic constructs go wild.
Larry Dickson