Design a “nested” readers–writers lock in which a thread must first grab the read lock in order to grab the write lock, and releasing the write lock does not release the read lock. In order for a...

Design a “nested” readers–writers lock in which a thread must first grab the read lock in order to grab the write lock, and releasing the write lock does not release the read lock. In order for a reader to become a writer with exclusive write access, every other reader must either unlock the read lock or also attempt to lock the write lock. Show that your implementation is correct and has a reasonable fair ness guarantee between readers and writers.