Date: Mon, 4 Dec 2000 17:48:40 -0600 (CST) From: Jonathan Lemon <jlemon@flugsvamp.com> To: jhb@FreeBSD.ORG, smp@FreeBSD.ORG Subject: Re: Netgraph and SMP Message-ID: <200012042348.eB4NmeA73673@prism.flugsvamp.com> In-Reply-To: <local.mail.freebsd-smp/XFMail.001204144630.jhb@FreeBSD.org> References: <local.mail.freebsd-smp/200012042250.eB4Mo7F01738@mass.osd.bsdi.com>
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In article <local.mail.freebsd-smp/XFMail.001204144630.jhb@FreeBSD.org> you write: > >On 04-Dec-00 Mike Smith wrote: >>> > 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. >> >> Er, no, you just have to acquire the exclusive lock in the MOD_UNLOAD >> handler. >> >> As for the actual availibility of SIX-style locks; I'm fairly sure you >> can do this with the lockmgr. > >Yes. See the allproc_lock as an example. Let's get realistic here. We're not going to get a shared lockmgr lock for every stinking packet that comes into the network. While SIX locks (or semaphore, or shared reader/writer) is nice in theory, I think the performance impact is too much for this particular case. -- Jonathan To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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