From owner-freebsd-arch  Tue Jan 16 17:29:20 2001
Delivered-To: freebsd-arch@freebsd.org
Received: from fw.wintelcom.net (ns1.wintelcom.net [209.1.153.20])
	by hub.freebsd.org (Postfix) with ESMTP id 3A6BF37B69F
	for <arch@FreeBSD.ORG>; Tue, 16 Jan 2001 17:29:01 -0800 (PST)
Received: (from bright@localhost)
	by fw.wintelcom.net (8.10.0/8.10.0) id f0H1Sxx00994;
	Tue, 16 Jan 2001 17:28:59 -0800 (PST)
Date: Tue, 16 Jan 2001 17:28:59 -0800
From: Alfred Perlstein <bright@wintelcom.net>
To: Terry Lambert <tlambert@primenet.com>
Cc: Kirk McKusick <mckusick@mckusick.com>, arch@FreeBSD.ORG
Subject: Re: dynamic vs static sysctls?
Message-ID: <20010116172859.B7240@fw.wintelcom.net>
References: <20010115223342.L7240@fw.wintelcom.net> <200101170125.SAA19549@usr08.primenet.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/1.2.5i
In-Reply-To: <200101170125.SAA19549@usr08.primenet.com>; from tlambert@primenet.com on Wed, Jan 17, 2001 at 01:25:43AM +0000
Sender: owner-freebsd-arch@FreeBSD.ORG
Precedence: bulk
X-Loop: FreeBSD.ORG

* Terry Lambert <tlambert@primenet.com> [010116 17:25] wrote:
> > I like this optimization, the only problem is that there's a chance
> > that a dynamic sysctl may disapear out from under you, and even
> > worse, replaced by an unrelated writeable one.
> > 
> > Perhaps you should include a generation count within the sysctl to
> > prevent this sort of potential problem?  So besideds passing the
> > sysctl number, you would include a generation count and error out
> > if both numbers didn't match?
> 
> Dynamically created OIDs should:
> 
> 1)	Monotonically increase

They don't seem to, this is the main problem with doing any translation,
it looks like:

        /*
         * If this oid has a number OID_AUTO, give it a number which
         * is greater than any current oid.  Make sure it is at least
         * 100 to leave space for pre-assigned oid numbers.
         */
        if (oidp->oid_number == OID_AUTO) {
                /* First, find the highest oid in the parent list >99 */
                n = 99;
                SLIST_FOREACH(p, parent, oid_link) {
                        if (p->oid_number > n)
                                n = p->oid_number;
                }
                oidp->oid_number = n + 1;
        }

Could cause some issues because it seems that if a sysctl were to
"go away" the next one to apear under the same level will replace
its number.

> 
> 2)	Be illegal to cache over reboots

of course!

> 
> 3)	Reset on reboots

ditto.

-- 
-Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
"I have the heart of a child; I keep it in a jar on my desk."


To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-arch" in the body of the message