Like process-lock, but on a "sharing" lock.
A sharing lock.
The status of the process while lock is locked, as seen in the Process Browser.
A non-negative real or nil.
The function process-exclusive-lock is the same as process-lock, but on a "sharing" lock. It waits until sharing-lock is free before locking it in exclusive mode.
Calls to process-exclusive-lock should be paired with process-exclusive-unlock calls. In most cases the macro with-exclusive-lock the best way to achieve this.
It is not possible to use exclusive lock in the scope of a sharing lock on the same lock, and trying to do this will cause the process to hang. Whether it is possible to use an exclusive lock inside an exclusive lock of the same lock is determined by the recursivep argument in make-lock.
process-exclusive-lock is guaranteed to return if it locked sharing-lock, but may throw before locking, as described in Guarantees and limitations when locking and unlocking.
LispWorks User Guide and Reference Manual - 20 Sep 2017