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From: David Dawes <dawes@rf900.physics.usyd.edu.au>
Message-Id: <199603160127.MAA14131@rf900.physics.usyd.edu.au>
Subject: Re: -current and accelx
To: toor@dyson.iquest.net (John S. Dyson)
Date: Sat, 16 Mar 1996 12:27:20 +1100 (EST)
Cc: sos@FreeBSD.org, coredump@nervosa.com, mmead@Glock.COM,
        current@FreeBSD.org
In-Reply-To: <199603151751.RAA03179@dyson.iquest.net> from "John S. Dyson" at Mar 15, 96 05:51:50 pm
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>> Ok, so I did a simple test, and found out that its the change in
>> vm_mmap.c (1.38->1.39) that makes life miserable for me and my accelx
>> server...
>> 
>> Hope that helps you John....
>> 
>Hmm... The fix that "fixes" Accelx, breaks XFree86?!?!?!?  I am going
>to ask mmead, and whomever to run a version of vm_mmap.c (I'll create it
>in about an hour or so) that logs the type of mmaps being done.

I'm don't have any ideas about AccelX, but after looking at the changes
in vm_mmap.c, I tried adding MAP_SHARED to the mmap() flags in my test
program, and that fixed it when using the 1.38 version of vm_mmap.c.
I don't understand why the mapping needs to be shared to prevent a
*parent* losing it after it has forked.  We certainly don't need (or want)
the child to share the mapping.  I may be mis-understanding the intention
of MAP_SHARED.

David