Fix termination race condition in OperatorPublish.dispatch

Author: akarnokd

src/main/java/rx/internal/operators/OperatorPublish.java

@@ -458,6 +458,15 @@ void dispatch() {
             boolean skipFinal = false;
             try {
                 for (;;) {
+                    /*
+                     * We need to read terminalEvent before checking the queue for emptyness because
+                     * all enqueue happens before setting the terminal event.
+                     * If it were the other way around, when the emission is paused between
+                     * checking isEmpty and checking terminalEvent, some other thread might
+                     * have produced elements and set the terminalEvent and we'd quit emitting
+                     * prematurely.
+                     */
+                    Object term = terminalEvent;
                     /*
                      * See if the queue is empty; since we need this information multiple
                      * times later on, we read it one.
@@ -468,7 +477,7 @@ void dispatch() {
                     // if the queue is empty and the terminal event was received, quit
                     // and don't bother restoring emitting to false: no further activity is
                     // possible at this point
-                    if (checkTerminated(terminalEvent, empty)) {
+                    if (checkTerminated(term, empty)) {
                         skipFinal = true;
                         return;
                     }
@@ -508,10 +517,11 @@ void dispatch() {
                         // it may happen everyone has unsubscribed between here and producers.get()
                         // or we have no subscribers at all to begin with
                         if (len == unsubscribed) {
+                            term = terminalEvent;
                             // so let's consume a value from the queue
                             Object v = queue.poll();
                             // or terminate if there was a terminal event and the queue is empty
-                            if (checkTerminated(terminalEvent, v == null)) {
+                            if (checkTerminated(term, v == null)) {
                                 skipFinal = true;
                                 return;
                             }
@@ -748,4 +758,4 @@ public void unsubscribe() {
             }
         }
     }
-}
+}