Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!amdcad!ames!ucbcad!ucbvax!SCU.BITNET!HYUNG
From: HYUNG@SCU.BITNET ("Defender of The Faith")
Newsgroups: comp.os.vms
Subject: Asynchronous Process Communication
Message-ID: <8801040013.AA00529@jade.berkeley.edu>
Date: 4 Jan 88 00:13:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 38

Hello Netlanders:

        I am looking for a simple way to synchornize multiple processes
that belong to different users.  In other words, they all have different
UID's.

        I have tried using global memory mapping giving read/write access
to all these processes with each one of them monitoring a semaphore.
The problem is that I can't think of any other way to monitor the
semaphore except with a "while(TRUE)" loop (yes, I am writing in C).
And this drives the CPU usage all the way up to the ceiling.

        My second try was to use system event flags, but the problem
is that I can not set/reset those flags if my processes do not belong
to the same Group ID.  Unfortunately, at our site, each user has its
own Group ID.

        The third solution was to put all processes in HIBER and have
them wake each other up when needed.  However, this requires WORLD priv
and I want these processes to run without any special PRIV.

        I am thinking of implementing the four alternative, which is to
set up 2 mailboxes for each process, one input and one output.  Each
mailbox will have an AST attached to it.  The processes are put into
hibernation and will wake up when something is written to the mailboxes
(activating the AST's).

        However, before implementing that, I would like to find out
if I am missing an obvious, simple/elegant solution to my problem.
After all, asynchornous process communication (with different UID's)
should be pretty common on the VAX.

Thanks in advance to ANY help I can get.

Henry Yung
BITNET: hyung@scu
ARPA: hyung%scu.bitnet@ucbjade.berkeley.edu
INTERNET: henry_k_yung@cup.portal.com