once again, cooperative multitasking?

["Mark D. Anderson" <mda@...>]

I've looked through the mailing list archives, and found a number
of matches, but many of the posts are of the form "I could tell
you how I did this, but then I'd have to kill you."

I'm wondering what the possibilities are for integrating lua with
a C program that uses a user threading library (non preemptive)
such as Pth or coro, based on setjmp/longjmp.

I can see in the manual that there is support for coroutines:
  http://www.lua.org/manual/5.0/manual.html#coroutine
  http://www.lua.org/manual/5.0/manual.html#5.2
Though this just describes an API from the lua side, with no
explanation of implementation, or indications of
what can and can't be done from C.

Also, I presume that Lua is fine with having distinct threads
on the C side use distinct Lua environments, even
without lua_lock? 
lua_lock is just if you want multiple C threads playing in the
same Lua environment?

-mda