Date: Thu, 28 Mar 2002 17:37:11 -0500 (EST) From: John Baldwin <jhb@FreeBSD.org> To: Julian Elischer <julian@elischer.org> Cc: arch@FreeBSD.ORG, Bosko Milekic <bmilekic@unixdaemons.com> Subject: Re: SMP safe reference counting Message-ID: <XFMail.20020328173711.jhb@FreeBSD.org> In-Reply-To: <Pine.BSF.4.21.0203281412340.53693-100000@InterJet.elischer.org>
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On 28-Mar-2002 Julian Elischer wrote: > > > On Thu, 28 Mar 2002, Bosko Milekic wrote: > >> >> On Thu, Mar 28, 2002 at 09:45:02AM -0500, John Baldwin wrote: >> > >> > On 28-Mar-2002 Bosko Milekic wrote: >> > > >> > > I don't think we really need a ref. count API, per-se. I can think of >> > > several places that may need to do ref. counting but wouldn't want to >> > > do it with a bus-locked instruction because their reference counter(s) >> > > are already protected by an existing mutex. >> > > >> > > -Bosko >> > >> > Those places wouldn't use the API then I think. However, this would be >> > good >> > for things like ucreds, pargs, uidinfos and others. >> >> Yeah, absolutely. I was just pointing out that there's little point >> in having a reference counting API when a lot of the reference counting >> implementations won't be using it. > > but a lot would.. and that's GOOD. > > John, can you put your sugfgested API up again? > I remember it would work but was (in my mind) 'different'. > I didn't think it was intuative but at least get it up for discussion.. > > (I posted my suggested API a few mails ago.. I'm sure it too has > weaknesses though) It's old but it's been at ~jhb/paches/refcount.patch for about an eternity right now. The changes I would make to it are that I would change refcount_drop() (or release or whatever it is called) to return the current value rather than a boolean about the value being 0 or not. Also, once atomic_fetchadd() is done, it will change a fair bit. There would just be a MI header, no MD stuff, and we woudln't use a mutex for the debug version that uses asserts. > Julian -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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