From a38694bd69e6733c7bcae24702754f31702d8d1a Mon Sep 17 00:00:00 2001
From: Patrik Nordwall <patrik.nordwall@gmail.com>
Date: Tue, 25 Sep 2012 18:35:07 +0200
Subject: [PATCH] Remove race when terminating, see #2552

---
 .../main/scala/akka/remote/RemoteDaemon.scala | 29 ++++++++++---------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/akka-remote/src/main/scala/akka/remote/RemoteDaemon.scala b/akka-remote/src/main/scala/akka/remote/RemoteDaemon.scala
index ccdeee439b..eb13428ca5 100644
--- a/akka-remote/src/main/scala/akka/remote/RemoteDaemon.scala
+++ b/akka-remote/src/main/scala/akka/remote/RemoteDaemon.scala
@@ -10,6 +10,7 @@ import akka.event.LoggingAdapter
 import akka.dispatch.Watch
 import akka.actor.ActorRefWithCell
 import akka.actor.ActorRefScope
+import akka.util.Switch
 
 private[akka] sealed trait DaemonMsg
 private[akka] case class DaemonMsgCreate(props: Props, deploy: Deploy, path: String, supervisor: ActorRef) extends DaemonMsg
@@ -28,7 +29,7 @@ private[akka] class RemoteSystemDaemon(system: ActorSystemImpl, _path: ActorPath
 
   system.provider.systemGuardian.tell(RegisterTerminationHook, this)
 
-  @volatile private var terminating = false
+  private val terminating = new Switch(false)
 
   /**
    * Find the longest matching path which we know about and return that ref
@@ -56,7 +57,7 @@ private[akka] class RemoteSystemDaemon(system: ActorSystemImpl, _path: ActorPath
   }
 
   override def !(msg: Any)(implicit sender: ActorRef = null): Unit = msg match {
-    case message: DaemonMsg if !terminating ⇒
+    case message: DaemonMsg ⇒
       log.debug("Received command [{}] to RemoteSystemDaemon on [{}]", message, path.address)
       message match {
         case DaemonMsgCreate(props, deploy, path, supervisor) ⇒
@@ -66,18 +67,19 @@ private[akka] class RemoteSystemDaemon(system: ActorSystemImpl, _path: ActorPath
               // TODO RK canonicalize path so as not to duplicate it always #1446
               val subpath = elems.drop(1)
               val path = this.path / subpath
-              val actor = system.provider.actorOf(system, props, supervisor.asInstanceOf[InternalActorRef],
-                path, systemService = false, Some(deploy), lookupDeploy = true, async = false)
-              addChild(subpath.mkString("/"), actor)
-              actor.sendSystemMessage(Watch(actor, this))
+              terminating.fold(
+                log.debug("Skipping [{}] to RemoteSystemDaemon on [{}] while terminating", message, path.address)) {
+
+                  val actor = system.provider.actorOf(system, props, supervisor.asInstanceOf[InternalActorRef],
+                    path, systemService = false, Some(deploy), lookupDeploy = true, async = false)
+                  addChild(subpath.mkString("/"), actor)
+                  actor.sendSystemMessage(Watch(actor, this))
+                }
             case _ ⇒
               log.error("remote path does not match path from message [{}]", message)
           }
       }
 
-    case message: DaemonMsg if terminating ⇒
-      log.debug("Skipping [{}] to RemoteSystemDaemon on [{}] while terminating", message, path.address)
-
     case Terminated(child: ActorRefWithCell) if child.asInstanceOf[ActorRefScope].isLocal ⇒
       removeChild(child.path.elements.drop(1).mkString("/"))
       terminationHookDoneWhenNoChildren()
@@ -85,14 +87,15 @@ private[akka] class RemoteSystemDaemon(system: ActorSystemImpl, _path: ActorPath
     case t: Terminated ⇒
 
     case TerminationHook ⇒
-      terminating = true
-      terminationHookDoneWhenNoChildren()
-      allChildren foreach system.stop
+      terminating.switchOn {
+        terminationHookDoneWhenNoChildren()
+        allChildren foreach system.stop
+      }
 
     case unknown ⇒ log.warning("Unknown message {} received by {}", unknown, this)
   }
 
-  def terminationHookDoneWhenNoChildren(): Unit = if (terminating && !hasChildren)
+  def terminationHookDoneWhenNoChildren(): Unit = if (terminating.isOn && !hasChildren)
     system.provider.systemGuardian.tell(TerminationHookDone, this)
 
 }