       return true
 
     default:
-      preconditionFailure("Weird context value in \(__FUNCTION__)")
+      preconditionFailure("Unknown context value in \(__FUNCTION__)")
     }
   }
 

      return element

    default:
      preconditionFailure("Weird context value in \(__FUNCTION__)")
    }
  }
}

      return false
    }

    // make our data available for a reader
    let threadLock = SemaphorePool.dequeue()
    dispatch_set_context(threadLock, &newElement)
    writerQueue.enqueue(threadLock)
    OSSpinLockUnlock(&lock)
