Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!snorkelwacker.mit.edu!bloom-beacon!eru!hagbard!sunic!news.funet.fi!jyu.fi!sakkinen
From: sakkinen@jyu.fi (Markku Sakkinen)
Newsgroups: comp.object
Subject: Re: concurrency control
Message-ID: <1991Apr5.104007.29531@jyu.fi>
Date: 5 Apr 91 10:40:07 GMT
References: <1991Apr4.215238.14067@bingvaxu.cc.binghamton.edu>
Reply-To: sakkinen@jytko.jyu.fi (Markku Sakkinen)
Organization: University of Jyvaskyla, Finland
Lines: 34

In article <1991Apr4.215238.14067@bingvaxu.cc.binghamton.edu> yunyau@bingvaxu.cc.binghamton.edu (Yun Yau Shih) writes:
>Hi Nets:
>
>I am new to the object-oriented concept. So, I hope I would not insult
>any one in this group by asking the following question.

You are welcome.  This group is indeed not reserved only for us who pretend
to know everything, to flame each other.

>What does it mean by "Several threads can simultaneously enter an object
>and execute concurrently." Does it mean REAL CONCURRENCY? How about the
>concurrency control, then? Or an object should have a machanism like a
>monitor. Any comment/hint/reference is welcomed. Thanks in advance.

That's what it means.  And right, systems that allow this will need
some kind of intra-object concurrency control.  One system that I have
happened to read about and that works like this is Parallel Objects
by Corradi and Leonardi.  However, it is probably much more common
that an object can be connected to only one thread or process at a time,
possibly with the exception of urgent messages that can preempt an
ordinary thread.

Recommended reading to start with: "Object-Oriented Concurrent Programming",
ed. by Yonezawa and Tokoro, MIT Press 1987.

Real experts of concurrent OOP, please continue if necessary.

Markku Sakkinen
Department of Computer Science and Information Systems
University of Jyvaskyla (a's with umlauts)
PL 35
SF-40351 Jyvaskyla (umlauts again)
Finland
          SAKKINEN@FINJYU.bitnet (alternative network address)