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Date:      Wed, 09 Oct 1996 19:07:21 -0700
From:      John Polstra <jdp@polstra.com>
To:        Charles Henrich <henrich@crh.cl.msu.edu>
Cc:        jgreco@brasil.moneng.mei.com, freebsd-hackers@freebsd.org, dyson@freebsd.org
Subject:   Re: CVSup
Message-ID:  <199610100207.TAA00561@austin.polstra.com>
In-Reply-To: <199610091424.KAA04600@crh.cl.msu.edu>

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> It appears to run (spiffy little tool!) but I billions (okay hundreds :) of:
> 
> fatal process exception: page fault, fault VA = 0x4d9a98
> fatal process exception: page fault, fault VA = 0x3e080c
> fatal process exception: page fault, fault VA = 0x4db3c0
> fatal process exception: page fault, fault VA = 0x3663c0
> ...
> Any hints out there?

Gads!

My -current system is from October 5, and it doesn't do that.  I wonder
if it's caused by some recent change to the VM system ...

Modula-3 has a VM-synchronized garbage collector.  It uses mprotect() to
make certain pages inaccessible, and then catches the SIGBUS signals
that result when accesses occur.  Then it does some GC-related things,
unprotects the offending pages, and continues.

Which is all just a wordy way of saying that it does behave quite
differently from conventional programs.

John Dyson, does any of this ring a bell with you, in connection with
recent changes to the VM system?

John
--
   John Polstra                                       jdp@polstra.com
   John D. Polstra & Co., Inc.                Seattle, Washington USA
   "Self-knowledge is always bad news."                 -- John Barth



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