(defmacro read-with-rw-lock ((lock) &body body)
  (let ((locked (gensym)))
    `(let ((,locked nil))
       (unwind-protect
            (progn 
              (begin-read ,lock)
              (setf ,locked t)
              (unwind-protect
                   (if ,locked
                       (locally ,@body))
                (if ,locked
                    (end-read ,lock))))
         (if ,locked
             (end-write ,lock))))))

(defmacro write-with-rw-lock ((lock) &body body)
  (let ((locked (gensym)))
    `(let ((,locked nil))
       (unwind-protect
            (progn 
              (begin-write ,lock)
              (setf ,locked t)
              (unwind-protect 
                   (if ,locked
                       (locally ,@body))
                (if ,locked
                    (end-write ,lock))))
         (if ,locked
             (end-write ,lock))))))