Date: Tue, 21 Nov 2000 23:44:02 -0500 From: "Kurt J. Lidl" <lidl@pix.net> To: Pedro F Giffuni <pfg1+@pitt.edu>, Tony Finch <dot@dotat.at> Cc: freebsd-hackers@FreeBSD.org Subject: Re: sfork() ?? Message-ID: <20001121234402.C18090@pix.net> In-Reply-To: <Pine.GSO.3.96L.1001121201011.27588A-100000@unixs1.cis.pitt.edu>; from Pedro F Giffuni on Tue, Nov 21, 2000 at 08:27:06PM -0500 References: <20001122004551.A50272@hand.dotat.at> <Pine.GSO.3.96L.1001121201011.27588A-100000@unixs1.cis.pitt.edu>
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On Tue, Nov 21, 2000 at 08:27:06PM -0500, Pedro F Giffuni wrote: > rfork comes from plan 9 and along with sfork it wasn't part of the > 4.4BSDlite 2 release, OTOH if both are the same, why aren't we referencing > it in our syscalls for compatibility with BSDI ? > > I can't find a reference to sfork elsewhere, but anyone with BSD/OS 2.x > or later should know for sure. sfork(), in the not-quite-released BSD/OS 4.2 has gotten an overhaul, to the point where fork() and vfork() are just sfork() wrappers. I've heard the comment before that sfork() is just the BSD way of pronouncing rfork()! So in the 4.2 release, BSD/OS will finally have a fully variable weight fork() call, which would be suitable for implementing all sorts of lightweight processes, threads and so forth. For those unfamiliar with variable weight fork semantics, bastically, you get to specify which parts of the process space you want to share and which parts you want to have a new version of in the child process. So, you can trivially share data, memory, etc... (Stack, of course, cannot be shared :-) The linux clone() call is something similar to sfork()/vfork(). It has some extra grot pasted onto the side to allow for pid hiding, for the wretched hack of a way to do pthreads support there. Chris Torek has described this in amazing detail in the past, while answering a different question. Look for the message with the Subject line "why fork?" in the following digest message: http://faqchest.dynhost.com/prgm/perlu-l/perl-99/perl-9906/perl-990602/perl99061420_14433.html -Kurt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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