🚀 go-pugleaf

SunOS seems to have a number of Light Weight Process 
system calls in their C library (see lwp_create(3)).

How was this done without modifications to their system
calls? That is, it appears as though they did it without 
introducing any new system calls that would not be in
System V Release 4. 

I'm trying to see if System V Release 4 could in fact support
user-level threads using an enhanced C library?

Assumption 1:

SunOS implements threads in part by using the memcntl(2) call to cause
the user process's memory space to be shared and then it creates light
wieght processes using fork (which would be reasonable fast since it
doesn't have to copy the parent's processes data). Yet is seems that
SUN's LWP library calls include nice things like a preemptive
scheduler while still allowing a single thread to block on I/O without
everything else blocking.

Is it possible to implement light weight processes in a stock
System V Release 4 UNIX?

     -Mike Grenier
      mike@sp.unisys.com