diff -r ff38d05ea86f -r 38e8278318ca src/share/vm/runtime/jniHandles.cpp
--- a/src/share/vm/runtime/jniHandles.cpp	Fri Jun 18 16:51:54 2010 -0700
+++ b/src/share/vm/runtime/jniHandles.cpp	Mon Jun 21 14:26:17 2010 -0700
@@ -66,6 +66,7 @@
 
 
 jobject JNIHandles::make_global(Handle obj) {
+  assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
   jobject res = NULL;
   if (!obj.is_null()) {
     // ignore null handles
@@ -81,6 +82,7 @@
 
 
 jobject JNIHandles::make_weak_global(Handle obj) {
+  assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
   jobject res = NULL;
   if (!obj.is_null()) {
     // ignore null handles