while looking into the problem with freeing the sau twice,
I hit another assertion fairly repeatably:

panic: kernel debugging assertion "vp->savp_lwp == l2" failed: file "../../../../kern/kern_sa.c", line 1021

the way I trigger this is to start named, run another program that
allocates enough memory that named is completely paged out, then send
named a SIGKILL.  running this in a loop for a while has triggered the
assertion several times.  does anyone else want to look at this one?

-Chuck