Index: lams_learning/src/java/org/lamsfoundation/lams/learning/service/LearnerService.java
===================================================================
RCS file: /usr/local/cvsroot/lams_learning/src/java/org/lamsfoundation/lams/learning/service/LearnerService.java,v
diff -u -r1.89 -r1.89.2.1
--- lams_learning/src/java/org/lamsfoundation/lams/learning/service/LearnerService.java	29 Oct 2008 05:34:52 -0000	1.89
+++ lams_learning/src/java/org/lamsfoundation/lams/learning/service/LearnerService.java	17 Feb 2009 04:53:22 -0000	1.89.2.1
@@ -97,8 +97,9 @@
     private ActivityMapping activityMapping;
     private IUserManagementService userManagementService;
     private ILessonService lessonService;
+    private static HashMap<Integer, Long> syncMap = new HashMap<Integer, Long>();
     protected MessageService messageService;
-
+    
     // ---------------------------------------------------------------------
     // Inversion of Control Methods - Constructor injection
     // ---------------------------------------------------------------------
@@ -426,20 +427,49 @@
      *      org.lamsfoundation.lams.learningdesign.Activity)
      */
     public LearnerProgress moveToActivity(Integer learnerId, Long lessonId, Activity fromActivity, Activity toActivity) {
-	LearnerProgress progress = learnerProgressDAO.getLearnerProgressByLearner(learnerId, lessonId);
+	
+    	int count = 0;
+    	LearnerProgress progress = null;
 
-	if (fromActivity != null) {
-	    progress.setProgressState(fromActivity, LearnerProgress.ACTIVITY_ATTEMPTED, activityDAO);
-	}
+    	  // wait till lock is released
+ 	 	while(syncMap.containsKey(learnerId)) {
+ 	 		count++;
+ 	 		try {
+ 	 			Thread.sleep(1000);
+ 	 			
+ 	 			if(count > 100) {
+ 	 				throw new LearnerServiceException("Thread wait count exceeded limit.");
+ 	 			}
+ 	 		} catch (InterruptedException e1) {
+ 	 			throw new LearnerServiceException("While retrying to move activity, thread was interrupted.", e1);
+ 	 		}
+ 	 	}
 
-	if (toActivity != null) {
-	    progress.setProgressState(toActivity, LearnerProgress.ACTIVITY_ATTEMPTED, activityDAO);
-	    progress.setCurrentActivity(toActivity);
-	    progress.setNextActivity(toActivity);
-	}
+ 	 	// lock
+ 	 	try {
+		 	syncMap.put(learnerId, lessonId);
+		 	progress = learnerProgressDAO.getLearnerProgressByLearner(learnerId, lessonId);
+		 	 
+			if (fromActivity != null) {
+			    progress.setProgressState(fromActivity, LearnerProgress.ACTIVITY_ATTEMPTED, activityDAO);
+			}
+		
+			if (toActivity != null) {
+			    progress.setProgressState(toActivity, LearnerProgress.ACTIVITY_ATTEMPTED, activityDAO);
+			    progress.setCurrentActivity(toActivity);
+			    progress.setNextActivity(toActivity);
+			}
 
-	learnerProgressDAO.updateLearnerProgress(progress);
-	return progress;
+			learnerProgressDAO.updateLearnerProgress(progress);
+ 	 	} catch(Exception e) {
+ 	 		 throw new LearnerServiceException(e.getMessage());
+ 	 	} finally {
+ 	 		// remove lock
+ 	 		if(syncMap.containsKey(learnerId))
+ 	 			 syncMap.remove(learnerId);
+ 	 	}
+ 	 	
+		return progress;
     }
 
     /**