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Date: 5 Aug 91 16:06:25 GMT
From: emery@mitre-bedford.arpa  (David Emery)
Subject: Re: Ada and Unix--Blocked Tasks
Message-ID: <EMERY.91Aug5090625@Dr_No.mitre.org>
List-Id: <comp.lang.ada>

There is clearly a problem with Unix here, and not with the Ada
implementation.  Unix semantics are pretty clear, the _process_
blocks.  The Unix kernal has no knowledge of Ada tasks, and if all of
the tasks are in a single Unix process, then Unix blocks the process
and all of its tasks.  

There are some hacks (such as using the SIGIO signals) for resolving
this problem, but the basic problem is that Unix was not designed for
multithreaded processes.  This is NOT fixed in POSIX 1003.1, but may
well be fixed (for Ada) by POSIX 1003.4a, which extends the POSIX
interface to handle multiple threads.

				dave emery