From 13eb1b6c8b5e516cb0e3ebd69cdabd6cf8dcfe36 Mon Sep 17 00:00:00 2001
From: Roland <rk@rkuhn.info>
Date: Mon, 5 Dec 2011 16:18:56 +0100
Subject: [PATCH] replace @volatile for childrenRefs with mailbox status read
 for memory consistency

---
 akka-actor/src/main/scala/akka/actor/ActorCell.scala | 2 --
 akka-actor/src/main/scala/akka/actor/ActorRef.scala  | 9 ++++++---
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/akka-actor/src/main/scala/akka/actor/ActorCell.scala b/akka-actor/src/main/scala/akka/actor/ActorCell.scala
index 01500a0301..2eb1ccd777 100644
--- a/akka-actor/src/main/scala/akka/actor/ActorCell.scala
+++ b/akka-actor/src/main/scala/akka/actor/ActorCell.scala
@@ -99,8 +99,6 @@ private[akka] class ActorCell(
   var receiveTimeoutData: (Long, Cancellable) =
     if (_receiveTimeout.isDefined) (_receiveTimeout.get, emptyCancellable) else emptyReceiveTimeoutData
 
-  // this is accessed without further synchronization during actorFor look-ups
-  @volatile
   var childrenRefs: TreeMap[String, ChildRestartStats] = emptyChildrenRefs
 
   def actorOf(props: Props, name: String): ActorRef = {
diff --git a/akka-actor/src/main/scala/akka/actor/ActorRef.scala b/akka-actor/src/main/scala/akka/actor/ActorRef.scala
index 118e07cd37..230a4d9571 100644
--- a/akka-actor/src/main/scala/akka/actor/ActorRef.scala
+++ b/akka-actor/src/main/scala/akka/actor/ActorRef.scala
@@ -245,9 +245,12 @@ class LocalActorRef private[akka] (
    * to inject “synthetic” actor paths like “/temp”.
    */
   protected def getSingleChild(name: String): InternalActorRef = {
-    val children = actorCell.childrenRefs
-    if (children contains name) children(name).child.asInstanceOf[InternalActorRef]
-    else Nobody
+    if (actorCell.isTerminated) Nobody // read of the mailbox status ensures we get the latest childrenRefs
+    else {
+      val children = actorCell.childrenRefs
+      if (children contains name) children(name).child.asInstanceOf[InternalActorRef]
+      else Nobody
+    }
   }
 
   def getChild(names: Iterable[String]): InternalActorRef = {