Date: Sat, 13 Jul 1996 23:29:08 -0600
   From: Warner Losh <imp@village.org>

   Sun, when they were writing Solaris, is rumored to have produced
   "warlock."  This program would go through all your sources and warn
   of potential deadlock situations in them.  They never released it
   as they considered it a competitive advantage to them...

Solaris kernel also has a debugging feature, it's called "deadman".
Every so often a timer based callout runs which runs down all the
mutex/semaphore/spinlock holder lists in the kernel and panics if any
circular and/or deadlock cases are found.

Later,
David S. Miller
dm@sgi.com