Processes stuck in *unp_m after recent uipc changes

With the latest uipc locking changes, I experienced a hard lockup on
my -current machine. Many processes got stuck in *unp_m state and
ctrl-alt-delete at the console cannot properly restart the machine and
I had to hard-reset (no coredump available). Is there anyway to
diagnose this?

Jiawei

-- 
"If it looks like a duck, walks like a duck, and quacks like a duck,
then to the end user it's a duck, and end users have made it pretty
clear they want a duck; whether the duck drinks hot chocolate or
coffee is irrelevant."