Path: utzoo!mnetor!uunet!portal!cup.portal.com!doug-merritt
From: doug-merritt@cup.portal.com
Newsgroups: comp.sys.amiga
Subject: Re: Unix on the Amiga
Message-ID: <5122@cup.portal.com>
Date: 5 May 88 17:39:00 GMT
References: <517@viscous> <51577@sun.uucp> <1923@sugar.UUCP>
Organization: The Portal System (TM)
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Peter da Silva remarks that he doesn't think that the Unix fork()
call to create a duplicate child process will ever be implemented on
the Amiga.

The reason to doubt this is that the *right* way to implement it
depends on having sufficient memory management to give each process
its own address space, so that you can copy the parent to the child,
and have all pointers behave.

However, there is a way to do it. There've been zillions of discussions
about this over in the minix group, and it's actually been implemented
in the Atari ST version of Minix. You just swap the child process in
every time it gets cpu time (i.e. copy it back to the same place in
memory it used to be in). Inefficient, and wastes memory, but it works.
There are certainly problems with doing this with general processes under
AmigaDOS (I'd imagine that AmigaDOS could scribble on the wrong copy
of a process). But it works with the Amiga *hardware*. It conceivably
could even work under AmigaDOS, if you thought it out carefully enough,
possibly restricting the way in which the forked() process used AmigaDOS
services.
     Doug

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