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make cleanUp of systemMessages atomic

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- extend systemDrain to take the new contents which shall be switched in
- make NoMessage placeholder which will signal final closing of the
  mailbox
- put that in when cleaning up, and check it when enqueuing
This commit is contained in:
Roland 2012-06-04 12:18:30 +02:00
parent 1821927023
commit fd1d0ce121
5 changed files with 40 additions and 35 deletions
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51
akka-actor/src/main/scala/akka/dispatch/Mailbox.scala
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@ -169,6 +169,7 @@ private[akka] abstract class Mailbox(val actor: ActorCell, val messageQueue: Mes
*/
protected final def systemQueueGet: SystemMessage =
Unsafe.instance.getObjectVolatile(this, AbstractMailbox.systemMessageOffset).asInstanceOf[SystemMessage]
protected final def systemQueuePut(_old: SystemMessage, _new: SystemMessage): Boolean =
Unsafe.instance.compareAndSwapObject(this, AbstractMailbox.systemMessageOffset, _old, _new)
@ -208,14 +209,14 @@ private[akka] abstract class Mailbox(val actor: ActorCell, val messageQueue: Mes
}
final def processAllSystemMessages() {
var nextMessage = systemDrain()
var nextMessage = systemDrain(null)
try {
while ((nextMessage ne null) && !isClosed) {
if (debug) println(actor.self + " processing system message " + nextMessage + " with " + actor.childrenRefs)
actor systemInvoke nextMessage
nextMessage = nextMessage.next
// don’t ever execute normal message when system message present!
if (nextMessage eq null) nextMessage = systemDrain()
if (nextMessage eq null) nextMessage = systemDrain(null)
}
} catch {
case NonFatal(e) ⇒
@ -235,15 +236,13 @@ private[akka] abstract class Mailbox(val actor: ActorCell, val messageQueue: Mes
protected[dispatch] def cleanUp(): Unit =
if (actor ne null) { // actor is null for the deadLetterMailbox
val dlm = actor.systemImpl.deadLetterMailbox
while (hasSystemMessages) {
var message = systemDrain()
while (message ne null) {
// message must be “virgin” before being able to systemEnqueue again
val next = message.next
message.next = null
dlm.systemEnqueue(actor.self, message)
message = next
}
var message = systemDrain(NoMessage)
while (message ne null) {
// message must be “virgin” before being able to systemEnqueue again
val next = message.next
message.next = null
dlm.systemEnqueue(actor.self, message)
message = next
}
if (messageQueue ne null) // needed for CallingThreadDispatcher, which never calls Mailbox.run()
@ -300,7 +299,7 @@ private[akka] trait SystemMessageQueue {
/**
* Dequeue all messages from system queue and return them as single-linked list.
*/
def systemDrain(): SystemMessage
def systemDrain(newContents: SystemMessage): SystemMessage
def hasSystemMessages: Boolean
}
@ -315,26 +314,30 @@ private[akka] trait DefaultSystemMessageQueue { self: Mailbox ⇒
assert(message.next eq null)
if (Mailbox.debug) println(actor.self + " having enqueued " + message)
val head = systemQueueGet
/*
* this write is safely published by the compareAndSet contained within
* systemQueuePut; “Intra-Thread Semantics” on page 12 of the JSR133 spec
* guarantees that “head” uses the value obtained from systemQueueGet above.
* Hence, SystemMessage.next does not need to be volatile.
*/
message.next = head
if (!systemQueuePut(head, message)) {
message.next = null
systemEnqueue(receiver, message)
if (head == NoMessage) actor.system.deadLetterMailbox.systemEnqueue(receiver, message)
else {
/*
* this write is safely published by the compareAndSet contained within
* systemQueuePut; “Intra-Thread Semantics” on page 12 of the JSR133 spec
* guarantees that “head” uses the value obtained from systemQueueGet above.
* Hence, SystemMessage.next does not need to be volatile.
*/
message.next = head
if (!systemQueuePut(head, message)) {
message.next = null
systemEnqueue(receiver, message)
}
}
}
@tailrec
final def systemDrain(): SystemMessage = {
final def systemDrain(newContents: SystemMessage): SystemMessage = {
val head = systemQueueGet
if (systemQueuePut(head, null)) SystemMessage.reverse(head) else systemDrain()
if (systemQueuePut(head, newContents)) SystemMessage.reverse(head) else systemDrain(newContents)
}
def hasSystemMessages: Boolean = systemQueueGet ne null
}
/**