Is socket buffer locking as questionable as it seems?

[Brian Fundakowski Feldman]

I keep getting these panics on my SMP box (no backtrace or DDB or crash
dump of course, because panic() == hang to FreeBSD these days):
panic: receive: m == 0 so->so_rcv.sb_cc == 52
>From what I can tell, all sorts of socket-related calls are "MP-safe"
and yet never even come close to locking the socket buffer.  From
what I can tell, the easiest way for this occur would be sbrelease()
being called from somewhere that it's supposed to, but doesn't, have
sblock().  Has anyone seen these, or a place to start looking?  Maybe
a way to get panics to stop hanging the machine?  TIA if anyone has
some enlightenment.