-/** A special value to represent a successful trylock */
-#define VALUE_TRYSUCCESS 1
-
-/** A special value to represent a failed trylock */
-#define VALUE_TRYFAILED 0
+/**
+ * @brief The "location" at which a fence occurs
+ *
+ * We need a non-zero memory location to associate with fences, since our hash
+ * tables don't handle NULL-pointer keys. HACK: Hopefully this doesn't collide
+ * with any legitimate memory locations.
+ */
+#define FENCE_LOCATION ((void *)0x7)