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From: phil@ux1.cso.uiuc.edu (Phil Howard KA9WGN)
Newsgroups: comp.os.mach
Subject: questions on C threads (part of Mach)
Message-ID: <1991May12.230130.8199@ux1.cso.uiuc.edu>
Date: 12 May 91 23:01:30 GMT
Organization: University of Illinois at Urbana
Lines: 26

This question applies to the C threads library which is part of Mach.
I decided to ask here since those familiar with this might be here in
greater concentration.

Suppose I have a master thread that forks off several slave threads.
It is indeterminate when the slave threads will finish, including the
order in which they will finish.  How can the master thread "join" or
otherwise wait for the conclusion of the first of the slave threads
to finish?

It seems to me that the only way to do this, given that the "join"
function only addresses one thread, is to have the threads manage
some shared queue upon which elements are placed to identify the
ending thread.  This would involve mutex's to lock on and a conditional
variable for the master thread to wait on, to discover which slave
thread is (or is about to) exit.  My objection to doing it this way
is that this seems like the kind of extra management work that a package
like C threads should really have implemented in the first place.

Comments?   Maybe a fuller description of the goals of the C threads
package that is part of Mach will make this clearer.
-- 
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/ Phil Howard -- KA9WGN -- phil@ux1.cso.uiuc.edu   |  Guns don't aim guns at  \
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