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Date:      08 May 2001 23:26:00 +0200
From:      Dag-Erling Smorgrav <des@ofug.org>
To:        tlambert2@mindspring.com
Cc:        Dennis Glatting <dennis.glatting@software-munitions.com>, Kris Kennaway <kris@obsecurity.org>, freebsd-stable@frebsd.org, freebsd-current@FreeBSD.ORG
Subject:   Re: pgm to kill 4.3 via vm
Message-ID:  <xzp4ruvjzx3.fsf@flood.ping.uio.no>
In-Reply-To: <3AF821C9.113680F1@mindspring.com>
References:  <20010507112937.V47835-100000@btw.plaintalk.bellevue.wa.us> <3AF821C9.113680F1@mindspring.com>

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Terry Lambert <tlambert2@mindspring.com> writes:
> A number of operating systems will allow programs to be
> parked "precious".  In AIX, this is done by establishing
> a signal handler for the resource starvation condition;
> programs without the handler "just die".  Programs with
> the handler are permitted to shut down gracefully.  A
> "precious" program, such as "init" or the swapper, etc.,
> just ignore the signal, and reestablish the handler (if
> they suffer from SVR3 signal semantics, and can't do it
> automatically).

Yes.  In fact, the new signal stuff was written as a consequence of a
previous round of this dicussion, where somebody pointed out that we
couldn't implement this because we already had 32 signals, and that
the old signal code didn't support more than 32 signals.  Now that
this is no longer an issue, I wouldn't mind seeing this implemented...
But you need to start signalling some yards from the edge of the cliff
instead of waiting until you stand at the brink, so your apps get a
fighting chance to catch and handle the signal.

You might want two signals, actually - one that defaults to SIG_IGN
(but some apps may want to catch it and start GCing to play nice with
their brethren), and one triggered a little later that kills any
process that doesn't catch it.

DES
-- 
Dag-Erling Smorgrav - des@ofug.org

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