Some macros for locking by value.

locking.clj

(def ^:dynamic *locks* (atom {}))

(defn new-lock []
  {:count 1 :ref (Object.)})

(defn inc-lock [lock]
  (when lock (update lock :count inc)))

(defn dec-lock [lock]
  (when lock (update lock :count dec)))

(defn obtain [v]
  (get (swap! *locks* update v #(or (inc-lock %) (new-lock))) v))

(defn release [v]
  (swap! *locks*
         (fn [value]
           (when-some [entry (get value v)]
             (if (= 1 (:count entry))
               (dissoc value v)
               (assoc value v (dec-lock entry)))))))

(defmacro with-locks [locks & body]
  `(binding [*locks* ~locks] ~@body))

(defmacro with-own-locks [& body]
  `(binding [*locks* (atom {})] ~@body))

(defmacro on-value [value & body]
  `(let [v# ~value]
     (try (locking (:ref (obtain v#)) ~@body)
          (finally (release v#)))))