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Date:      Wed, 8 Mar 2000 18:08:06 -0500 (EST)
From:      Peter Dufault <dufault@hda.com>
To:        Peter Jeremy <peter.jeremy@alcatel.com.au>
Cc:        Dave Boers <djb@wit389306.student.utwente.nl>, Arun Sharma <adsharma@sharmas.dhs.org>, freebsd-current@FreeBSD.ORG
Subject:   Re: current lockups
Message-ID:  <200003082308.SAA64038@hda.hda.com>
In-Reply-To: <00Mar8.103928est.115210@border.alcanet.com.au> from Peter Jeremy at "Mar 7, 2000 09:45:55 am"

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> On 2000-Mar-07 06:29:17 +1100, Dave Boers <djb@wit389306.student.utwente.nl> wrote:
> >It is rumoured that Arun Sharma had the courage to say:
> >> Compiling Mozilla with make -j 2 got -current to lock up, twice in
> >> succession. I'm running a fairly recent snapshot (a week or two old)
> >> on a Dual celeron box (BP6) with UDMA66 enabled.
> >
> >Finally. I've been complaining about this on several occasions. I'm also
> >running UDMA66 and Dual Celeron BP6. No overclocking. 
> 
> Later postings mention possible problems with UDMA66.  The other
> possibility that has been discussed recently is potential priority
> inversions for processes using rtptio and idprio.
> 
> Note that ntpd will use rtprio if the Posix P1003.1b extensions aren't
> enabled in the kernel.  (These were enabled by default in GENERIC on
> i386 in mid-January).  If you have the new ntpd (rather than xntpd)
> and are running a kernel without options P1003_1B,
> _KPOSIX_PRIORITY_SCHEDULING and _KPOSIX_VERSION=199309L, you could
> potentially get a lockup due to a priority inversion.  (Though I
> think the probability is very small).

There's no difference between rtprio and P1003.1B scheduling other than
the name.  rtprio is the same as P1003.1B "SCHED_RR".

I'd like to remove the rtprio call from ntpd.  I think we ought to do
it now before 4.0 ships.

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


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