HP Tru64 UNIX v 5.1B-4 systems have been
experiencing a panic with the panic string "a_lock timeout." The
problem was caused by a thread being preempted while holding a
simple lock. This caused other threads waiting for the lock to
timeout and panic.
The solution is to release the lock before preemption, and then
reacquire the lock and re-evaluate context upon continuing.
A typical stack trace follows: