From owner-freebsd-hackers  Thu Jan 30 19:05:47 1997
Return-Path: <owner-hackers>
Received: (from root@localhost)
          by freefall.freebsd.org (8.8.5/8.8.5) id TAA25965
          for hackers-outgoing; Thu, 30 Jan 1997 19:05:47 -0800 (PST)
Received: from eldorado.net-tel.co.uk ([193.122.171.253])
          by freefall.freebsd.org (8.8.5/8.8.5) with SMTP id TAA25957
          for <freebsd-hackers@freebsd.org>; Thu, 30 Jan 1997 19:05:40 -0800 (PST)
From: Andrew.Gordon@net-tel.co.uk
Received: (from root@localhost) by eldorado.net-tel.co.uk (8.6.12/8.6.10) id DAA19743; Fri, 31 Jan 1997 03:04:29 GMT
Received: from "/PRMD=NET-TEL/ADMD=GOLD 400/C=GB/" by net-tel.co.uk
        (Route400-RFCGate); Fri, 31 Jan 97  3:01:20 +0000
X400-Received: by mta "eldorado" in "/PRMD=net-tel/ADMD=gold 400/C=gb/"; 
        Relayed; Fri, 31 Jan 97  3:01:20 +0000
X400-Received: by mta "net-tel cambridge" in "/PRMD=net-tel/ADMD=gold 400/C=gb/";
         Relayed; Fri, 31 Jan 97  3:01:18 +0000
X400-Received: by "/PRMD=NET-TEL/ADMD=Gold 400/C=GB/"; Relayed; 
        Fri, 31 Jan 97  3:01:17 +0000
X400-MTS-Identifier: 
        ["/PRMD=NET-TEL/ADMD=Gold 400/C=GB/";hst:8035-970131030117-6E3C]
X400-Content-Type: P2-1984 (2)
X400-Originator: Andrew.Gordon@net-tel.co.uk
Original-Encoded-Information-Types: IA5-Text
X400-Recipients: non-disclosure:;
Date: Fri, 31 Jan 97  3:01:17 +0000
X400-Content-Identifier: Re(2): Using rfo
Message-Id: <"40b1-970131030103-8AD9*/G=Andrew/S=Gordon/O=NET-TEL Computer
 Systems Ltd/PRMD=NET-TEL/ADMD=Gold 400/C=GB/"@MHS>
To: rminnich@Sarnoff.COM
Cc: freebsd-hackers@freebsd.org
In-Reply-To: <Pine.SUN.3.91.970130081328.9307F-100000@terra>
Subject: Re(2): Using rfork() / threads
Sender: owner-hackers@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

> VM space handling is a little different. If you request VM space sharing,
> you don't exactly get Vm address space sharing:  what you get is instead
> shared data areas where in normal fork they are copied. More details on 
> request. The effect is what you want, though: shared data areas. 

What synchronization primitives are you supposed to use between two
rfork()ed processes?  Using SysV sepmaphores seems a bit perverse
(and would they even work in the environment after a rfork() ?),
but talking through pairs of sockets to lock small datastructures
seems a bit heavyweight.