6987597: ManagementFactory.getGarbageCollectorMXBeans() returns empty list with CMS

Reviewed-by: mchung

test/com/sun/management/GarbageCollectorMXBean/LastGCInfo.java

 /*
- * Copyright (c) 2004, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2004, 2013 Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -27,8 +27,11 @@
  * @summary Sanity Test for GarbageCollectorMXBean.getLastGcInfo().
  * @author  Mandy Chung
  *
- * @run main LastGCInfo
+ * @run main/othervm -XX:-ExplicitGCInvokesConcurrent LastGCInfo
  */
+// Passing "-XX:-ExplicitGCInvokesConcurrent" to force System.gc()
+// run on foreground when CMS is used and prevent situations when "GcInfo"
+// is missing even though System.gc() was successfuly processed.
 
 import java.lang.management.ManagementFactory;
 import java.lang.management.MemoryUsage;

test/java/lang/management/GarbageCollectorMXBean/GcInfoCompositeType.java

 /*
- * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2013 Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -26,8 +26,11 @@
  * @bug     6396794
  * @summary Check that LastGcInfo contents are reasonable
  * @author  Eamonn McManus
- * @run     main/othervm GcInfoCompositeType
+ * @run     main/othervm -XX:-ExplicitGCInvokesConcurrent GcInfoCompositeType
  */
+// Passing "-XX:-ExplicitGCInvokesConcurrent" to force System.gc()
+// run on foreground when CMS is used and prevent situations when "GcInfo"
+// is missing even though System.gc() was successfuly processed.
 
 import java.util.*;
 import java.lang.management.*;