Date: Tue, 19 Oct 2004 18:19:10 -0400 (EDT) From: Robert Watson <rwatson@FreeBSD.org> To: Julian Elischer <julian@elischer.org> Cc: Max Laier <max@love2party.net> Subject: Re: cvs commit: src/sys/sys protosw.h src/sys/kern uipc_domain.cuipc_socket2.c Message-ID: <Pine.NEB.3.96L.1041019181643.81058G-100000@fledge.watson.org> In-Reply-To: <41759110.6010005@elischer.org>
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On Tue, 19 Oct 2004, Julian Elischer wrote: > >>Another point: If you really want to keep the possibility to remove a > >>protocol, you have to introduce some busy counter that pervents removal while > >>the kernel is inside a protocol function. This has to be handled by the > >>protocol itself, but it has to be taken care of somehow. > > each protocol array entry could have either a mutex or a refcount or > both.. The trick here is to get just enough synchronization to not break, but not enough to hurt. That's one of the reasons why I feel like the heavier weight approaches taken elsewhere may not be appropriate here. I guess no one is talking about loading UDP, but at the same time if we're going to have generic loadable protocol support, it would be nice to get a pretty clean API that would meet the requirements of higher volume protocols. As I mentioned in a previous e-mail, it might almost be desirable to say "no unloading" and simply avoid the hard problems, since atomic add is easy whereas atomic remove is hard. Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Principal Research Scientist, McAfee Research
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