hutch@net1.ucsd.edu (Jim Hutchison) (05/27/88)
Ports? Oh my! Yes, in the heavy duty sense you have to dup all of the
parents resources (including program data space). For the average use,
things can be much simpler.
I'm porting things (junk, stuff, tidbits). I only need to have wait() wait,
and fork() start up a second task. This will get me going for the
fork()/exec() crew. I would rather munge as little code as possible.
Admittedly I may be misunderstanding again (like when I didn't know about
scatter loading :-( for program loading), but shouldn't this work o.k.?
All I want is a new *seperate* process which I can examine for signs of life.
Comments?
--
Jim Hutchison UUCP: {dcdwest,ucbvax}!cs!net1!hutch
ARPA: Hutch@net1.ucsd.edu
Disclaimer: The cat agreed that it would be o.k. to say these things.elg@killer.UUCP (Eric Green) (05/29/88)
in article <4982@sdcsvax.UCSD.EDU>, hutch@net1.ucsd.edu (Jim Hutchison) says: > Ports? Oh my! Yes, in the heavy duty sense you have to dup all of the > parents resources (including program data space). For the average use, > things can be much simpler. > > I'm porting things (junk, stuff, tidbits). I only need to have wait() wait, > and fork() start up a second task. This will get me going for the > fork()/exec() crew. I would rather munge as little code as possible. Hmm. Code is easy (if it's "pure", it's identical between the two processes). For small-model Manx, static data is easy to handle (just copy it, and change D4), and the same with stack (copy, change SP). But, things on the heap will kill you, as will the fact that sigbits are allocated on a per-process basis and not system-wide (meaning that all of your neatly duplicated I/O request blocks will fail to wake you up, or else will guru you :-( ). Thus, while it's reasonable to be able to expect multiple copies of the same program to be runnable, it is NOT reasonable to expect the other copies to be exact duplicates of the first, at any time in their running. Even if the OS had resource-tracking, there is no method besides a MMU for adjusting the pointers in linked lists upon the heap (or, at least, no cheap, easily implemented method that would be useful on a system-wide basis). -- Eric Lee Green {cuae2,ihnp4}!killer!elg Snail Mail P.O. Box 92191 Lafayette, LA 70509 "Is a dream a lie if it don't come true, or is it something worse?"