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Date:      Wed, 11 Mar 1998 11:52:25 -0500 (EST)
From:      Peter Dufault <dufault@hda.com>
To:        rich@immrc1.Eng.McMaster.CA (Richard Teltz)
Cc:        realtime@FreeBSD.ORG
Subject:   Re: threads questions
Message-ID:  <199803111652.LAA25788@hda.hda.com>
In-Reply-To: <199803032151.QAA05739@immrc.eng.mcmaster.ca> from Richard Teltz at "Mar 3, 98 04:51:04 pm"

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There is no rt-FreeBSD.  I've been putting the infrastructure for
P1003.1B into -current, and that along with the scheduler pieces
should be there this weekend.

Once that is there my understanding is that the threads package
will notice the support from the header files and you can specify
the alternative schedulers.  I haven't looked at this, though, so
you'll have to research how it works for yourself.

You still have the many issues of the non-reentrancy of the kernel,
etc, that make FreeBSD inappropriate for most serious uses.  If I
had the time I'd follow this route:

1. First set it up so that you could have the scheduler policy
apply only within a process group, making the system a lot better
for developing and simulating real time processes, though not
delivering them.  For example, you could then use the Ptolemy
system's real time scheduling to drive simulations without having
to be root and taking over the system.

2. Develop an approach of adding new pieces that were reentrant
and targeted at real time, and a way of detecting when regular
interrupts, system code, etc was activated and use make that
information available to the process as a "real time fault".

3. Work toward an MP system where you'd have a dedicated realtime
system.

Peter

-- 
Peter Dufault (dufault@hda.com)   Realtime development, Machine control,
HD Associates, Inc.               Safety critical systems, Agency approval

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