8243503: InstanceKlass::_array_name is not needed and leaks

Decrement the refcount for all Klass in class unloading.

Reviewed-by: lfoltan, hseigel

src/hotspot/share/classfile/classLoaderData.cpp

@@ -640,8 +640,8 @@ public:
     } else {
       assert(k->is_instance_klass(), "Must be");
       _instance_class_released ++;
-      InstanceKlass::release_C_heap_structures(InstanceKlass::cast(k));
     }
+    k->release_C_heap_structures();
   }
 };
 
@@ -869,7 +869,7 @@ void ClassLoaderData::free_deallocate_list_C_heap_structures() {
     } else if (m->is_klass()) {
       InstanceKlass* ik = (InstanceKlass*)m;
       // also releases ik->constants() C heap memory
-      InstanceKlass::release_C_heap_structures(ik);
+      ik->release_C_heap_structures();
       // Remove the class so unloading events aren't triggered for
       // this class (scratch or error class) in do_unloading().
       remove_class(ik);

src/hotspot/share/oops/instanceKlass.cpp

@@ -587,9 +587,9 @@ void InstanceKlass::deallocate_contents(ClassLoaderData* loader_data) {
   // to deallocate.
   assert(array_klasses() == NULL, "array classes shouldn't be created for this class yet");
 
-  // Release C heap allocated data that this might point to, which includes
+  // Release C heap allocated data that this points to, which includes
   // reference counting symbol names.
-  release_C_heap_structures();
+  release_C_heap_structures_internal();
 
   deallocate_methods(loader_data, methods());
   set_methods(NULL);
@@ -2386,7 +2386,6 @@ void InstanceKlass::metaspace_pointers_do(MetaspaceClosure* it) {
   it->push((Klass**)&_array_klasses);
   it->push(&_constants);
   it->push(&_inner_classes);
-  it->push(&_array_name);
 #if INCLUDE_JVMTI
   it->push(&_previous_versions);
 #endif
@@ -2581,17 +2580,19 @@ static void method_release_C_heap_structures(Method* m) {
   m->release_C_heap_structures();
 }
 
-void InstanceKlass::release_C_heap_structures(InstanceKlass* ik) {
+void InstanceKlass::release_C_heap_structures() {
+
   // Clean up C heap
-  ik->release_C_heap_structures();
+  release_C_heap_structures_internal();
-  ik->constants()->release_C_heap_structures();
+  constants()->release_C_heap_structures();
 
   // Deallocate and call destructors for MDO mutexes
-  ik->methods_do(method_release_C_heap_structures);
+  methods_do(method_release_C_heap_structures);
-
 }
 
-void InstanceKlass::release_C_heap_structures() {
+void InstanceKlass::release_C_heap_structures_internal() {
+  Klass::release_C_heap_structures();
+
   // Can't release the constant pool here because the constant pool can be
   // deallocated separately from the InstanceKlass for default methods and
   // redefine classes.
@@ -2629,12 +2630,6 @@ void InstanceKlass::release_C_heap_structures() {
   }
 #endif
 
-  // Decrement symbol reference counts associated with the unloaded class.
-  if (_name != NULL) _name->decrement_refcount();
-
-  // unreference array name derived from this class name (arrays of an unloaded
-  // class can't be referenced anymore).
-  if (_array_name != NULL)  _array_name->decrement_refcount();
   FREE_C_HEAP_ARRAY(char, _source_debug_extension);
 }
 

src/hotspot/share/oops/instanceKlass.hpp

@@ -205,9 +205,6 @@ class InstanceKlass: public Klass {
   // Specified as UTF-8 string without terminating zero byte in the classfile,
   // it is stored in the instanceklass as a NULL-terminated UTF-8 string
   const char*     _source_debug_extension;
-  // Array name derived from this class which needs unreferencing
-  // if this class is unloaded.
-  Symbol*         _array_name;
 
   // Number of heapOopSize words used by non-static fields in this klass
   // (including inherited fields but after header_size()).
@@ -734,10 +731,6 @@ public:
   const char* source_debug_extension() const { return _source_debug_extension; }
   void set_source_debug_extension(const char* array, int length);
 
-  // symbol unloading support (refcount already added)
-  Symbol* array_name()                     { return _array_name; }
-  void set_array_name(Symbol* name)        { assert(_array_name == NULL  || name == NULL, "name already created"); _array_name = name; }
-
   // nonstatic oop-map blocks
   static int nonstatic_oop_map_size(unsigned int oop_map_count) {
     return oop_map_count * OopMapBlock::size_in_words();
@@ -1193,7 +1186,8 @@ public:
 
   // callbacks for actions during class unloading
   static void unload_class(InstanceKlass* ik);
-  static void release_C_heap_structures(InstanceKlass* ik);
+
+  virtual void release_C_heap_structures();
 
   // Naming
   const char* signature_name() const;
@@ -1304,7 +1298,7 @@ private:
                                   PrivateLookupMode private_mode);
 
   // Free CHeap allocated fields.
-  void release_C_heap_structures();
+  void release_C_heap_structures_internal();
 
 #if INCLUDE_JVMTI
   // RedefineClasses support

src/hotspot/share/oops/klass.cpp

@@ -94,6 +94,10 @@ bool Klass::is_subclass_of(const Klass* k) const {
   return false;
 }
 
+void Klass::release_C_heap_structures() {
+  if (_name != NULL) _name->decrement_refcount();
+}
+
 bool Klass::search_secondary_supers(Klass* k) const {
   // Put some extra logic here out-of-line, before the search proper.
   // This cuts down the size of the inline method.

src/hotspot/share/oops/klass.hpp

@@ -674,6 +674,8 @@ protected:
   Symbol* name() const                   { return _name; }
   void set_name(Symbol* n);
 
+  virtual void release_C_heap_structures();
+
  public:
   // jvm support
   virtual jint compute_modifier_flags(TRAPS) const;

src/hotspot/share/oops/objArrayKlass.cpp

@@ -98,9 +98,7 @@ Klass* ObjArrayKlass::allocate_objArray_klass(ClassLoaderData* loader_data,
 
   // Create type name for klass.
   Symbol* name = NULL;
-  if (!element_klass->is_instance_klass() ||
+  {
-      (name = InstanceKlass::cast(element_klass)->array_name()) == NULL) {
-
     ResourceMark rm(THREAD);
     char *name_str = element_klass->name()->as_C_string();
     int len = element_klass->name()->utf8_length();
@@ -116,11 +114,7 @@ Klass* ObjArrayKlass::allocate_objArray_klass(ClassLoaderData* loader_data,
       new_str[idx++] = JVM_SIGNATURE_ENDCLASS;
     }
     new_str[idx++] = '\0';
-    name = SymbolTable::new_permanent_symbol(new_str);
+    name = SymbolTable::new_symbol(new_str);
-    if (element_klass->is_instance_klass()) {
-      InstanceKlass* ik = InstanceKlass::cast(element_klass);
-      ik->set_array_name(name);
-    }
   }
 
   // Initialize instance variables
@@ -143,12 +137,8 @@ Klass* ObjArrayKlass::allocate_objArray_klass(ClassLoaderData* loader_data,
 }
 
 ObjArrayKlass::ObjArrayKlass(int n, Klass* element_klass, Symbol* name) : ArrayKlass(name, ID) {
-  this->set_dimension(n);
+  set_dimension(n);
-  this->set_element_klass(element_klass);
+  set_element_klass(element_klass);
-  // decrement refcount because object arrays are not explicitly freed.  The
-  // InstanceKlass array_name() keeps the name counted while the klass is
-  // loaded.
-  name->decrement_refcount();
 
   Klass* bk;
   if (element_klass->is_objArray_klass()) {
@@ -157,12 +147,12 @@ ObjArrayKlass::ObjArrayKlass(int n, Klass* element_klass, Symbol* name) : ArrayK
     bk = element_klass;
   }
   assert(bk != NULL && (bk->is_instance_klass() || bk->is_typeArray_klass()), "invalid bottom klass");
-  this->set_bottom_klass(bk);
+  set_bottom_klass(bk);
-  this->set_class_loader_data(bk->class_loader_data());
+  set_class_loader_data(bk->class_loader_data());
 
-  this->set_layout_helper(array_layout_helper(T_OBJECT));
+  set_layout_helper(array_layout_helper(T_OBJECT));
-  assert(this->is_array_klass(), "sanity");
+  assert(is_array_klass(), "sanity");
-  assert(this->is_objArray_klass(), "sanity");
+  assert(is_objArray_klass(), "sanity");
 }
 
 int ObjArrayKlass::oop_size(oop obj) const {