Improve action task termination routine.

module/dal/control/src/main/java/org/openbase/bco/dal/control/action/ActionImpl.java

@@ -80,6 +80,13 @@ public class ActionImpl implements SchedulableAction {
     private ServiceDescription serviceDescription;
     private volatile Future<ActionDescription> actionTask;
 
+    /**
+     * This flag ist required to handle the case when the action task was
+     * initiated but never started because of any interruption.
+     * In this case the flag is false but the actionTask non null.
+     */
+    private volatile Boolean actionTaskRunning = false;
+
     /**
      * Constructor creates a new action object which helps to manage its execution during the scheduling process.
      * <p>
@@ -198,7 +205,7 @@ private boolean isActionTaskFinished() {
             // when the action task finishes it will finally reset the action task to null.
             // actionTask.isDone(); is not a solution at all because when the action task is
             // canceled then the method already returns true but the task is maybe still running.
-            return actionTask == null;
+            return actionTask == null || !actionTaskRunning;
         }
     }
 
@@ -256,7 +263,9 @@ public Future<ActionDescription> execute() {
                     new FatalImplementationErrorException("Action task still running while initializing a new one.", this);
                 }
 
+                actionTaskRunning = false;
                 actionTask = GlobalCachedExecutorService.submit(() -> {
+                    actionTaskRunning = true;
                     try {
 
                         // validate operation service
@@ -362,6 +371,7 @@ public Future<ActionDescription> execute() {
                         }
                     } finally {
                         actionTask = null;
+                        actionTaskRunning = false;
                         synchronized (actionTaskLock) {
                             actionTaskLock.notifyAll();
                         }
@@ -728,6 +738,14 @@ private void cancelActionTask() {
         // cancel if exist
         if (actionTask != null) {
             actionTask.cancel(true);
+
+            // if the task is canceled before it is scheduled, we need to notify
+            // all waiting tasks about the cancellation
+            synchronized (actionTaskLock) {
+                if (!actionTaskRunning) {
+                    actionTaskLock.notifyAll();
+                }
+            }
         }
 
         try {