Making sure that dispatcher scheduling for shutdown is checked even if unregister throws up

akka-actor/src/main/java/akka/dispatch/AbstractMessageDispatcher.java

@@ -0,0 +1,19 @@
+/**
+ * Copyright (C) 2009-2011 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package akka.dispatch;
+
+import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
+import java.util.concurrent.atomic.AtomicLongFieldUpdater;
+import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
+
+abstract class AbstractMessageDispatcher {
+    private volatile int _shutdownSchedule; // not initialized because this is faster: 0 == UNSCHEDULED
+    protected final static AtomicIntegerFieldUpdater<AbstractMessageDispatcher> shutdownScheduleUpdater =
+      AtomicIntegerFieldUpdater.newUpdater(AbstractMessageDispatcher.class, "_shutdownSchedule");
+
+    private volatile long _inhabitants; // not initialized because this is faster
+    protected final static AtomicLongFieldUpdater<AbstractMessageDispatcher> inhabitantsUpdater =
+      AtomicLongFieldUpdater.newUpdater(AbstractMessageDispatcher.class, "_inhabitants");
+}

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

@@ -107,15 +107,14 @@ abstract class MessageDispatcher(val app: ActorSystem) extends AbstractMessageDi
   /**
    * Attaches the specified actor instance to this dispatcher
    */
-  final def attach(actor: ActorCell) {
+  final def attach(actor: ActorCell): Unit = register(actor)
-    register(actor)
-  }
 
   /**
    * Detaches the specified actor instance from this dispatcher
    */
-  final def detach(actor: ActorCell) {
+  final def detach(actor: ActorCell): Unit = try {
     unregister(actor)
+  } finally {
     ifSensibleToDoSoThenScheduleShutdown()
   }
 
@@ -152,7 +151,7 @@ abstract class MessageDispatcher(val app: ActorSystem) extends AbstractMessageDi
     () ⇒ if (inhabitantsUpdater.decrementAndGet(this) == 0) ifSensibleToDoSoThenScheduleShutdown()
 
   /**
-   * Don't call this, this calls you. See "attach" for only invocation
+   * If you override it, you must call it. But only ever once. See "attach" for only invocation
    */
   protected[akka] def register(actor: ActorCell) {
     inhabitantsUpdater.incrementAndGet(this)
@@ -161,7 +160,7 @@ abstract class MessageDispatcher(val app: ActorSystem) extends AbstractMessageDi
   }
 
   /**
-   * Don't call this, this calls you. See "detach" for the only invocation
+   * If you override it, you must call it. But only ever once. See "detach" for the only invocation
    */
   protected[akka] def unregister(actor: ActorCell) {
     inhabitantsUpdater.decrementAndGet(this)