Description

   This routine initializes a read-write lock object. The routine
   initializes the tis_rwlock_t structure that holds the object's
   lock states.

   To destroy a read-write lock object, call the tis_rwlock_
   destroy() routine.

                                  NOTE

      The tis read-write lock has no relationship to the Single
      UNIX Specification, Version 2 (SUSV2, or UNIX98) read-
      write lock routines (such as pthread_rwlock_init()). The
      tis_rwlock_t type, in particular, cannot be used with the
      pthread read-write lock functions, nor can a pthread_rwlock_
      t type be used with the tis read-write lock functions.