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From: daemon@watdragon.waterloo.edu (Owner of Many System Processes)
Newsgroups: ont.events,uw.talks,uw.cs.grad
Subject: MASTER'S THESIS PRESENTATION
Keywords: Mr. Michel Fortier, graduate student,
Message-ID: <16247@watdragon.waterloo.edu>
Date: 6 Sep 89 14:53:42 GMT
Distribution: ont
Organization: U of Waterloo, Ontario
Lines: 58

Dept. of Computer Science, will speak on ``Study of Monitors.''
From: wlrush@poppy.waterloo.edu (Wenchantress Wench Wendall)
Path: poppy!wlrush


DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES

MASTER'S THESIS PRESENTATION

                    -Friday, September 8, 1989

Mr. Michel Fortier, graduate student, Dept. of Computer
Science, will speak on ``Study of Monitors.''

TIME:                 2:00 p.m.

ROOM:                 DC 1304

In  the  design  of  a  concurrent  system, problems of
synchronization  and  communication of processes can be
solve by using monitors.

Over   the   past  15  years several different kinds of
monitors   have  been   investigated.   A  taxonomy  is
presented   that  encompasses  all  these   traditional
monitors   and   suggests   others  not  found  in  the
literature  or  in existing programming languages.  The
classification  scheme  is  based on a single criterion
-  the  scheduling  of  processes   waiting  to use the
monitor which occurs after a wait, after  a  signal and
at  the  exit of the monitor.  It identifies a total of
nine  different  primitive  monitor  types:  six signal
monitors      based      on      categorizations     of
blocking/nonblocking    signal    and    priority    of
resumption,  two  based  on immediate return signal and
priority  of resumption, and two based on an automatic-
signal mechanism and priority of resumption.

An  attempt  is  made to give some empirical discussion
and   analytical   results   about  the  classification
criterion   that  suggest  that  some   monitor  types,
although   functionally  equivalent,  are  better  than
other  types.   In particular, the priority-nonblocking
monitor  has  properties that suggest it is better than
the others.

All   the   monitor   types  have been implemented in C
language.  By having the different monitor types in one
language, it was possible to run tests to compare them.

An    animation   facility   has  been  implemented  to
visualize   the  different   types   of   monitors   by
showing   process   movement   on   entry  queues,   on
condition   variables   and  in and out of the monitor.
With  this  tool, it is possible to see the differences
in the monnitors as well as deadlock and bottlenecks.