[9fans] spawn() vs fork()

[steve.kilbane@ind.alstom.com steve.kilbane@ind.alstom.com]

On 03/07/99 16:22:21 Digby Tarvin  wrote:

> That compromise meant that a fork() style of process creation
> was not possible (all pointers in the child's data segment would
> be pointing into the parents memory), so it uses a spawn() style
> of process creation.

It's not impossible: the Atari ST port of Minix managed fork() on M68000. I
believe the solution was to swap data and stack segments during a context
switch. This meant that anything that forked a child and then talked to it for a
while would run like treacle. Since most processes followed a fork() with an
exec(), it wasn't so much of a problem. All very reminiscent of vfork().

Implementation requirements aside, as Jean says, fork gives you an elegant way
of setting up I/O redirection. It also gives you an elegant way of determining
start-up context as a whole for the new process., including internal state.

steve