No need for deferred in gracefullyKillWorker().

lib/provider.js

@@ -131,17 +131,14 @@ function forceKillWorker(id) {
 }
 
 function gracefullyKillWorker(id) {
-  var deferred = Q.defer()
-
-  tryKillWorker(id)
+  return tryKillWorker(id)
     .timeout(10000)
-    .then(deferred.resolve)
     .catch(function() {
       log.error('Device worker "%s" did not stop in time', id)
-      forceKillWorker(id).then(deferred.resolve)
+      return forceKillWorker(id)
+        .timeout(10000)
+        .then(deferred.resolve)
     })
-
-  return deferred.promise
 }
 
 function gracefullyExit() {