The keyword argument recursivep to make-lock, when true, allows the lock to be locked recursively. recursivep is true by default. If recursivep is false then trying to lock again causes an error. This is useful for debugging code where the lock is not expected to be claimed recursively.
The keyword argument sharing to make-lock, when true, creates an "sharing" lock object, which supports sharing and exclusive locking. A sharing lock is handled by different functions and methods. See with-exclusive-lock, with-sharing-lock, process-exclusive-lock, process-exclusive-unlock, process-sharing-lock and process-sharing-unlock.
LispWorks User Guide and Reference Manual - 21 Dec 2011