Unlocks a lock held by the current process.
The lock.
When this is t, an error is signaled if *current-process* is not the owner of lock. The default is t.
Attempts to unlock lock. If lock is owned by *current-process*, then process-unlock decrements an internal count. If this count is then zero, lock is unlocked. Note that process-unlock relates only on Lisp processes.
process-sharing-unlock is guaranteed to successfully unlock lock, but is not guaranteed to return, as described in Guarantees and limitations when locking and unlocking.
LispWorks User Guide and Reference Manual - 20 Sep 2017