src/share/vm/classfile/javaClasses.cpp

@@ -829,10 +829,11 @@
   // the mirror.
   if (SystemDictionary::Class_klass_loaded()) {
     // Allocate mirror (java.lang.Class instance)
     oop mirror_oop = InstanceMirrorKlass::cast(SystemDictionary::Class_klass())->allocate_instance(k, CHECK);
     Handle mirror(THREAD, mirror_oop);
+    Handle comp_mirror;
 
     // Setup indirection from mirror->klass
     if (k != NULL) {
       java_lang_Class::set_klass(mirror(), k);
     }

@@ -842,26 +843,27 @@
 
     java_lang_Class::set_static_oop_field_count(mirror(), mk->compute_static_oop_field_count(mirror()));
 
     // It might also have a component mirror.  This mirror must already exist.
     if (k->is_array_klass()) {
-      oop comp_mirror;
       if (k->is_typeArray_klass()) {
         BasicType type = TypeArrayKlass::cast(k)->element_type();
-        comp_mirror = Universe::java_mirror(type);
+        comp_mirror = Handle(THREAD, Universe::java_mirror(type));
       } else {
         assert(k->is_objArray_klass(), "Must be");
         Klass* element_klass = ObjArrayKlass::cast(k)->element_klass();
         assert(element_klass != NULL, "Must have an element klass");
-        comp_mirror = element_klass->java_mirror();
+        comp_mirror = Handle(THREAD, element_klass->java_mirror());
       }
-      assert(comp_mirror != NULL, "must have a mirror");
+      assert(comp_mirror() != NULL, "must have a mirror");
 
       // Two-way link between the array klass and its component mirror:
       // (array_klass) k -> mirror -> component_mirror -> array_klass -> k
-      set_component_mirror(mirror(), comp_mirror);
-      set_array_klass(comp_mirror, k);
+      set_component_mirror(mirror(), comp_mirror());
+      // Set after k->java_mirror() is published, because compiled code running
+      // concurrently doesn't expect a k to have a null java_mirror.
+      // set_array_klass(comp_mirror, k);
     } else {
       assert(k->is_instance_klass(), "Must be");
 
       initialize_mirror_fields(k, mirror, protection_domain, THREAD);
       if (HAS_PENDING_EXCEPTION) {

@@ -879,14 +881,15 @@
     set_class_loader(mirror(), class_loader());
 
     // set the module field in the java_lang_Class instance
     set_mirror_module_field(k, mirror, module, THREAD);
 
-    // Setup indirection from klass->mirror last
+    // Setup indirection from klass->mirror
     // after any exceptions can happen during allocations.
-    if (k != NULL) {
       k->set_java_mirror(mirror());
+    if (comp_mirror() != NULL) {
+      set_array_klass(comp_mirror(), k);
     }
   } else {
     if (fixup_mirror_list() == NULL) {
       GrowableArray<Klass*>* list =
        new (ResourceObj::C_HEAP, mtClass) GrowableArray<Klass*>(40, true);

@@ -1086,11 +1089,11 @@
 }
 
 
 void java_lang_Class::set_array_klass(oop java_class, Klass* klass) {
   assert(klass->is_klass() && klass->is_array_klass(), "should be array klass");
-  java_class->metadata_field_put(_array_klass_offset, klass);
+  java_class->metadata_field_put_volatile(_array_klass_offset, klass);
 }
 
 
 bool java_lang_Class::is_primitive(oop java_class) {
   // should assert: