Re: once again, cooperative multitasking?

[Taj Khattra <taj.khattra@...>]

On Tue, Apr 13, 2004 at 12:32:41AM -0700, Mark D. Anderson wrote:
> 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.

with non-preemptive threads, i believe it should "just work" ?
i.e. you don't need to do anything extra to make it work.

for preemptive threads or multiple procs sharing a lua_State,
you'd need to define or more of:

LUA_USER_H
	include file included by lua.h
LUA_USERSTATE
	additional user state (e.g. space for lock)
	space is reserved just before lua_State (see lstate.c)
lua_userstateopen(L)
	init LUA_USERSTATE, if required (e.g. initialise lock)
	called by lua_open() (see lstate.c)
lua_lock(L)
lua_unlock(L)
	lock/unlock routines

i don't think this stuff is documented anywhere.  you can take
a look at etc/luser_tests.h for an example.  since it's just
testing the api, it declares a global lock - in real life, you'd
probably allocate a lock per lua_State.

> Also, I presume that Lua is fine with having distinct threads
> on the C side use distinct Lua environments, even
> without lua_lock? 

yes, each lua_State is completely independent.

> lua_lock is just if you want multiple C threads playing in the
> same Lua environment?

yes, but like i mentioned above, if they are non-preemptive then
i don't think you need lua_lock.