Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!cs.utexas.edu!uunet!mcsun!hp4nl!dutrun!winfwrd
From: winfwrd@dutrun.UUCP (Paul van der Weerd)
Newsgroups: comp.lang.smalltalk
Subject: Re: anyone using time-sliced scheduling w/st80?
Message-ID: <15113@dutrun.UUCP>
Date: 18 Mar 91 15:07:10 GMT
References: <HUGGINS.91Mar12085614@dino.ti.com> <4861@ns-mx.uiowa.edu> <3095@laura.UUCP>
Reply-To: winfwrd@dutrun.tudelft.nl.UUCP (Paul van der Weerd)
Organization: Delft University of Technology, The Netherlands
Lines: 46

The warning from Hubert Baumeister:

>But notice that time slicing is dangerous in the current implementation of the
>Smalltalk user interface as shows following example:
>        ProcessorScheduler startTimeSlicing.
>        [100 timesRepeat: [Transcript show: 'Process 1';cr]] fork.
>        [100 timesRepeat: [Transcript show: 'Process 2';cr]] fork.
>This will hang up Smalltalk because some recources are not protected against
>multiple access. (This is why the example above uses a SharedQueue instead of
>a WriteStream)

To prevent unprotected simultaneous access to a single Transcript, I took the
following approach:
(
| p1 p2 t1 t2 |
"Define some textcollectors."
[t1 := TextCollector new.
TextCollectorView open: t1 label: 'Process 1'] fork.
[t2 := TextCollector new.
TextCollectorView open: t2 label: 'Process 2'] fork.
"Define some processess."
p1 := [[true] whileTrue: [t1 show: 'A']] newProcess.
p2 := [[true] whileTrue: [t2 show: 'B']] newProcess.
"Run processes alternately."
(p1 priority: 3) resume.
(p2 priority: 3) resume.
300 timesRepeat: [
(Delay forMilliseconds: 200) wait.
(Processor suspendFirstAt: 3) resume].
p1 terminate.
p2 terminate.
)
Normally this works, but when some windows are overlapping,
the system crashes. What is wrong?

Question: A forked process is simple to create, but how do
you stop it without the process handle? Is something like a
ProcessInspector available?

--
Paul van der Weerd                  Tel. +31 15 782523
Delft University of Technology      Fax. +31 15 786522
Dept. of Computer Science           Email winfwrd@dutrun.tudelft.nl
Julianalaan 132
2628 BL  Delft
The Netherlands
...................................................................