Index: core/src/main/java/org/jbpm/logging/exe/LoggingInstance.java
===================================================================
--- core/src/main/java/org/jbpm/logging/exe/LoggingInstance.java	(revision 6947)
+++ core/src/main/java/org/jbpm/logging/exe/LoggingInstance.java	(working copy)
@@ -51,16 +51,16 @@
   public LoggingInstance() {
   }
 
-  public void startCompositeLog(CompositeLog compositeLog) {
+  public synchronized void startCompositeLog(CompositeLog compositeLog) {
     addLog(compositeLog);
     compositeLogStack.add(compositeLog);
   }
 
-  public void endCompositeLog() {
+  public synchronized void endCompositeLog() {
     compositeLogStack.remove(compositeLogStack.size() - 1);
   }
 
-  public void addLog(ProcessLog processLog) {
+  public synchronized void addLog(ProcessLog processLog) {
     if (!compositeLogStack.isEmpty()) {
       CompositeLog compositeLog = (CompositeLog) compositeLogStack.get(compositeLogStack.size() - 1);
       compositeLog.addChild(processLog);