V6 co-routine scheme and multitasking ?

[dan at rna.UUCP]

Hi,
	Remember the V6 co-routine scheme ? It was a package of C functions
such as crfork(), crread() and crwrite() which implemented behavior
"in many respects like a set of processes working in the same address space".
	Has anyone ever played with those routines ? (They disappeared in PWB
and V7). Does anyone have the V6 source code lying around (I suspect at least
some of the functions were PDP-11 assembler) ?
	I am interested in similar facilities for multitasking real-time
applications. Using the USG 5.0 shared memory calls would probably have similar
effect but may not be suitable for real-time, possibly standalone situations.
	I envision a set of routines (as portable as possible amongst different
CPU's) which implement an environment for a set of processes in the same
(at least data) address space. I know I can probably go with those ROM based
mini-kernels like Hunter and Ready's VRTX or JMI's C executive.
	Has anyone worked out similar schemes - preferably with hooks to use
multiple CPU's on the same memory bus and multitasking within each and among
all the CPU's.

					Cheers,
					Dan Ts'o
					...cmcl2!rna!dan