Unlocks the specified reader-writer lock.
#include <synch.h>
int rw_unlock (
rwlock_t *rwlp );
(IN) Points to the reader-writer lock to unlock.
Returns 0; no error conditions have been defined.
No assumptions can be made about the order in which threads waiting for a reader/writer lock will acquire the lock. That is, the reader/writer lock is not guaranteed to be FIFO.