rc scripts change for review

[Kostik Belousov]

On Sat, Apr 23, 2011 at 09:43:56PM -0700, Doug Barton wrote:
> On 04/23/2011 15:40, Rick Macklem wrote:
> >>
> >>>One thing I am not sure about is the REQUIRE: list in mountd.
> >>>nfsserver and nfssrv essentially load the respective module. They
> >>>are only
> >>>used if sysctl variables need to be set and that's actually done by
> >>>nfsd.
> >>>(Should they be listed in mountd or nfsd or ???)
> >>
> >>It's not a good idea to add single scripts that only have a tiny
> >>function, especially if they are only called conditionally (I.e., they
> >>contain KEYWORD: nostart). It's preferred to handle these things
> >>things
> >>in the script that needs them, or if it's necessary in more than one
> >>script to add a function to the appropriate .subr (rc, or network).
> >>
> >>So can you say a little more about what you're trying to accomplish?
> >>It's not clear to me why instead of doing this:
> >>
> >>+ if ! sysctl vfs.newnfs>/dev/null 2>&1; then
> >>+ force_depend nfssrv || return 1
> >>+ fi
> >>
> >>you would not just do this:
> >>
> >>+ if ! sysctl vfs.newnfs>/dev/null 2>&1; then
> >>+ load_kld nfsd
> >>+ fi
> >>
> >Well, the intent of the above was to get the module loaded so that
> >sysctl could manipulate its sysctl variables. I played with it a bit
> >and it turns out that neither of the above code snippets work in the
> >sense that they don't affect the outcome.
> >
> >What is needed to make the sysctls work is "nfssrv" has to be in the
> >REQUIRED: list for either mountd or nfsd. Without it, the sysctls fail
> >with unknown oid. (I'm guessing there is some delay between the load_kld
> >and when the module gets its sysctl variables registered?)
> >
> >Now, I'm not sure whether there is any advantage to specifying "nfssrv"
> >in nfsd or mountd, although both seem to work when I test them. "nfsserver"
> >is in mountd, so unless you guys have a better suggestion, that's where
> >I'll leave it.
> 
> From what you're describing the reason it works by using the nfsserver 
> and nfssrv scripts is simply an accident of timing. That's not a good 
> thing no matter how you look at it. :)  I understand your dilemma in 
> that the nfsserver "solution" was pre-existing, so you were just 
> following the example you had. However I have this odd idea that we 
> ought to fix broken code, not perpetuate it. Even if I weren't 
> interested in this for pedantic value, the fact that it's only working 
> now as an accident of timing is a good reason to fix it.
> 
> The load_kld module is safe to run unconditionally (it will simply 
> return if the module is loaded). So what you could do (for both cases) 
> is something like this:
> 
> load_kld nfsd
> while ! sysctl vfs.newnfs >/dev/null 2>&1; do
> 	sleep .5
> done
> 
> If that works, I think we should add that feature to load_kld itself.

This is a kludge, hiding some bug. Sysctl oids are registered synchronously,
and kldload(2) syscall loads the module in context of the called thread.
So if MOD_LOAD even handler registered its oids, then usermode and sysctl(8)
should see them without arbitrary wait.
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