network locking -- how to enable?

[Goodleaf, John M]

Hello,
I've just been reading the Oct-Dec 2003 FreeBSD status report. I note
there's a section describing how much of the work toward fine-grained
locking in the networking subsystem is in 5.2 RELEASE, but not turned on.
Now I've been out of the loop for a while, so I must have missed something.
How do I turn it on? I realize there may be stability problems, so I don't
plan to try it on a production machine. (How unstable is it, really?)

Thanks,
John