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From: samuel@nada.kth.se (Samuel Cederlind)
Newsgroups: comp.os.mach
Subject: Threads and fork() on the NeXT
Summary: Forking threads after forking tasks
Keywords: NeXT, thread
Message-ID: <1990Sep15.221401.25887@nada.kth.se>
Date: 15 Sep 90 22:14:01 GMT
Sender: Samuel Cederlund, samuel@nada.kth.se
Organization: Royal Institute of Technology, Stockholm, Sweden
Lines: 20

(This question also posed to comp.sys.next)
How come forking C-threads on the NeXT does not work after
having done a unix fork() call?

As I ported the public domain XScheme to our NeXT, I made an object
extension to it, originally because we wanted to build an adventure
game.

Using the Mach operating system, objects can communicate nicely with-
out knowing the borders of their tasks. It would then be very convenient
if objects could be "forked off" into new processes.
There is a function in the NeXT Reference Manual, task_create(), very
briefly documented. In the Mach manuals it says:
> Note:  Not implemented yet. Use fork.

So I have. There are three or so threads that always need to be running
for the communication between objects. After a fork(), you have to
create all threads anew, right? Anyway, there I'm stuck. This seems
an insoluble problem. cthread_fork() yields an error, and sticks.
Is there any reason why this should be?