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From: mouse@mcgill-vision.UUCP.UUCP
Newsgroups: mod.computers.68k
Subject: Re: Questions about the use of fork()
Message-ID: <8703310008.AA20068@larry.ee.mcgill>
Date: Mon, 30-Mar-87 19:08:45 EST
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Posted: Mon Mar 30 19:08:45 1987
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In article <8703210641.AA09391@violet.berkeley.edu>, mwm@VIOLET.BERKELEY.EDU (Mike  Meyer, No one lives forever.) writes:
[ stuff about how using fexec() because it covers 99% of the cases is a
  bad idea - I agree. ]
> What I prefer is two system calls:

> 2) newthread - roughly, vfork in 4BSD. This creates another process
> that shares all resources with the parent. If either one does an
> exit() (or exec()) the other one just continues. YOu probably want to
> schedule the child to run first. Some technic for rendezvous will be
> required.

> Newthread gives you the capabilities of Unix fork/exec, you just
> have to take more care about things. It should cover all the cases you
> want fork for. Of course, the cases you want it for fork/exec

Heavens no.  Do you realize what concurrent execution with shared stack
segments means?!  Shared text is OK, and is in fact used.  Shared data
can be useful but is normally a pain for tasks where you want fork()
but not fexec().  Shared stack is a disaster, *unless*, as in BSD
vfork(), one process waits until the other exit()s (or exec()s).  Even
then, vfork() is annoying in its restrictions.

fork() is nice when you want to keep all the code in one process
(fexec() requires having the child's program in another file somewhere,
and wiring its name in somehow - using fork() means the binary is
self-contained and more portable).

					der Mouse

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