Index: oak-run/src/main/java/org/apache/jackrabbit/oak/benchmark/ConcurrentWriteACLTest.java
===================================================================
--- oak-run/src/main/java/org/apache/jackrabbit/oak/benchmark/ConcurrentWriteACLTest.java	(revision 1574819)
+++ oak-run/src/main/java/org/apache/jackrabbit/oak/benchmark/ConcurrentWriteACLTest.java	(working copy)
@@ -19,6 +19,7 @@
 
 import java.util.Random;
 
+import javax.jcr.InvalidItemStateException;
 import javax.jcr.Node;
 import javax.jcr.Session;
 import javax.jcr.security.AccessControlEntry;
@@ -73,28 +74,30 @@
         Session session = null;
         try {
             session = loginWriter();
-            for (int i=0; i<10; i++) {
+            for (int i=0; i<20; i++) {
                 session.refresh(false);
                 int a = random.nextInt(NODE_COUNT);
                 int b = random.nextInt(NODE_COUNT);
                 String path = "/" + ROOT_NODE_NAME + "/node" + a + "/node" + b;
                 AccessControlManager acMgr = session.getAccessControlManager();
                 JackrabbitAccessControlList acl = AccessControlUtils.getAccessControlList(session, path);
-                Privilege[] privileges = new Privilege[] {
-                        acMgr.privilegeFromName(Privilege.JCR_READ),
-                        acMgr.privilegeFromName(Privilege.JCR_READ_ACCESS_CONTROL)
-                };
-                if (acl.addAccessControlEntry(EveryonePrincipal.getInstance(), privileges)) {
+                if (acl.isEmpty()) {
+                    Privilege[] privileges = new Privilege[] {
+                            acMgr.privilegeFromName(Privilege.JCR_READ),
+                            acMgr.privilegeFromName(Privilege.JCR_READ_ACCESS_CONTROL)
+                    };
+                    if (acl.addAccessControlEntry(EveryonePrincipal.getInstance(), privileges)) {
+                        acMgr.setPolicy(path, acl);
+                    }
+                } else {
+                    for (AccessControlEntry ace: acl.getAccessControlEntries()) {
+                        acl.removeAccessControlEntry(ace);
+                    }
                     acMgr.setPolicy(path, acl);
                 }
                 session.save();
-                for (AccessControlEntry ace: acl.getAccessControlEntries()) {
-                    acl.removeAccessControlEntry(ace);
-                }
-                acMgr.setPolicy(path, acl);
-                session.save();
             }
-        } catch (Exception e) {
+        } catch (InvalidItemStateException e) {
             // ignore
         } finally {
             if (session != null) {