Switching to the same system message emptying strategy as for the normal Dispatcher, on the BalancingDispatcher

akka-actor/src/main/scala/akka/dispatch/BalancingDispatcher.scala

@@ -44,11 +44,9 @@ class BalancingDispatcher(
   protected val messageQueue: MessageQueue = mailboxType match {
     case u: UnboundedMailbox ⇒ new QueueBasedMessageQueue with UnboundedMessageQueueSemantics {
       final val queue = new ConcurrentLinkedQueue[Envelope]
-      final val dispatcher = BalancingDispatcher.this
     }
     case BoundedMailbox(cap, timeout) ⇒ new QueueBasedMessageQueue with BoundedMessageQueueSemantics {
       final val queue = new LinkedBlockingQueue[Envelope](cap)
-      final val dispatcher = BalancingDispatcher.this
       final val pushTimeOut = timeout
     }
     case other ⇒ throw new IllegalArgumentException("Only handles BoundedMailbox and UnboundedMailbox, but you specified [" + other + "]")
@@ -73,18 +71,19 @@ class BalancingDispatcher(
 
   protected[akka] override def unregister(actor: ActorCell) = {
     super.unregister(actor)
-    intoTheFray(except = actor)
     buddies.remove(actor)
+    intoTheFray(except = actor)
   }
 
   protected override def cleanUpMailboxFor(actor: ActorCell, mailBox: Mailbox) {
     if (mailBox.hasSystemMessages) {
-      var messages = mailBox.systemDrain()
-      while (messages ne null) {
-        deadLetterMailbox.systemEnqueue(actor.self, messages) //Send to dead letter queue
-        messages = messages.next
-        if (messages eq null) //Make sure that any system messages received after the current drain are also sent to the dead letter mbox
-          messages = mailBox.systemDrain()
+      var message = mailBox.systemDrain()
+      while (message ne null) {
+        // message must be “virgin” before being able to systemEnqueue again
+        val next = message.next
+        message.next = null
+        deadLetterMailbox.systemEnqueue(actor.self, message)
+        message = next
       }
     }
   }