Date: Mon, 04 Dec 2000 22:31:36 +0000 From: Brian Somers <brian@Awfulhak.org> To: Mike Smith <msmith@FreeBSD.org> Cc: Julian Elischer <julian@elischer.org>, brian@FreeBSD.org, archie@FreeBSD.org, phk@FreeBSD.org, smp@FreeBSD.org, brian@Awfulhak.org Subject: Re: Netgraph and SMP Message-ID: <200012042231.eB4MVaD93192@hak.lan.Awfulhak.org> In-Reply-To: Message from Mike Smith <msmith@FreeBSD.org> of "Mon, 04 Dec 2000 13:40:08 PST." <200012042140.eB4Le9F01294@mass.osd.bsdi.com>
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> The simplest structure for this is a shared/exclusive lock
> that supports intention; Terry would have ranted about this. (He would
> have called it a SIX-lock, I think).
[.....]
> This may sound simplistic, but given that you don't necessarily make
> changes to Netgraph very often, this is quite likely more than adequate
> for now.
Nice, I never realised there were shared/exclusive locks available.
I think netgraph nodes would also need to have a ``modevent'' that
fails MOD_UNLOAD events if any locks are outstanding.
Of course there'll probably be loads of edge-cases :-/
> > I'm trying to figure out the locking needed for SMP in Netgraph.
> >
> > Here are some of the various constraints that I see. (some of theme are not just
> > SMP issues).
> >
> > 1/ can't remove modules that are being used (the base framework) or have living
> > nodes (other netgraph modules).
> > 2/ Cannot remove a node if it is in use, (or in a return stack somewhere)
> > 3/ Cannot unlink an 'edge' if someone is passing data across it.
> > 4/ cannot use edges and nodes that are in the process of being set up or torn
> > down.
> > 5/ Defered deliveries cannot be made to nodes that are being removed.
> > 6/ Nodes cannot be completely removed if there are pending deliveries for them.
> >
> > What locking schemes to otther people use for protecting intricate structures of
> > objects with various interconnections? The buffer cache is one example that
> > comes to mind, as is the routing table.
> >
> > Julian
> > --
> > __--_|\ Julian Elischer
> > / \ julian@elischer.org
> > ( OZ ) World tour 2000
> > ---> X_.---._/ presently in: Budapest
> > v
> >
> >
> > To Unsubscribe: send mail to majordomo@FreeBSD.org
> > with "unsubscribe freebsd-smp" in the body of the message
> >
>
> --
> ... every activity meets with opposition, everyone who acts has his
> rivals and unfortunately opponents also. But not because people want
> to be opponents, rather because the tasks and relationships force
> people to take different points of view. [Dr. Fritz Todt]
> V I C T O R Y N O T V E N G E A N C E
--
Brian <brian@Awfulhak.org> <brian@[uk.]FreeBSD.org>
<http://www.Awfulhak.org>; <brian@[uk.]OpenBSD.org>
Don't _EVER_ lose your sense of humour !
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