8008549: NPG: SystemDictionary::find(...) unnecessarily keeps class loaders alive

Summary: SystemDictionary::find(...) should not create and register ClassLoaderData objects for class loaders.
Reviewed-by: coleenp, acorn
Contributed-by: NStefan Karlsson &lt;stefan.karlsson@oracle.com&gt;, Erik Helin <erik.helin@oracle.com>

src/share/vm/classfile/classLoaderData.hpp

@@ -234,6 +234,7 @@ class ClassLoaderData : public CHeapObj<mtClass> {
   void add_to_deallocate_list(Metadata* m);
 
   static ClassLoaderData* class_loader_data(oop loader);
+  static ClassLoaderData* class_loader_data_or_null(oop loader);
   static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS);
   static void print_loader(ClassLoaderData *loader_data, outputStream *out);
 

src/share/vm/classfile/classLoaderData.inline.hpp

@@ -25,9 +25,15 @@
 #include "classfile/classLoaderData.hpp"
 #include "classfile/javaClasses.hpp"
 
+inline ClassLoaderData* ClassLoaderData::class_loader_data_or_null(oop loader) {
+  if (loader == NULL) {
+    return ClassLoaderData::the_null_class_loader_data();
+  }
+  return java_lang_ClassLoader::loader_data(loader);
+}
+
 inline ClassLoaderData* ClassLoaderData::class_loader_data(oop loader) {
-  if (loader == NULL) return ClassLoaderData::the_null_class_loader_data();
-  ClassLoaderData* loader_data = java_lang_ClassLoader::loader_data(loader);
+  ClassLoaderData* loader_data = class_loader_data_or_null(loader);
   assert(loader_data != NULL, "Must be");
   return loader_data;
 }

src/share/vm/classfile/dictionary.cpp

@@ -347,6 +347,7 @@ void Dictionary::add_klass(Symbol* class_name, ClassLoaderData* loader_data,
   assert_locked_or_safepoint(SystemDictionary_lock);
   assert(obj() != NULL, "adding NULL obj");
   assert(obj()->name() == class_name, "sanity check on name");
+  assert(loader_data != NULL, "Must be non-NULL");
 
   unsigned int hash = compute_hash(class_name, loader_data);
   int index = hash_to_index(hash);

src/share/vm/classfile/systemDictionary.cpp

@@ -866,16 +866,22 @@ Klass* SystemDictionary::resolve_instance_class_or_null(Symbol* name, Handle cla
 // the new entry.
 
 Klass* SystemDictionary::find(Symbol* class_name,
-                                Handle class_loader,
-                                Handle protection_domain,
-                                TRAPS) {
+                              Handle class_loader,
+                              Handle protection_domain,
+                              TRAPS) {
 
   // UseNewReflection
   // The result of this call should be consistent with the result
   // of the call to resolve_instance_class_or_null().
   // See evaluation 6790209 and 4474172 for more details.
   class_loader = Handle(THREAD, java_lang_ClassLoader::non_reflection_class_loader(class_loader()));
-  ClassLoaderData* loader_data = register_loader(class_loader, CHECK_NULL);
+  ClassLoaderData* loader_data = ClassLoaderData::class_loader_data_or_null(class_loader());
+
+  if (loader_data == NULL) {
+    // If the ClassLoaderData has not been setup,
+    // then the class loader has no entries in the dictionary.
+    return NULL;
+  }
 
   unsigned int d_hash = dictionary()->compute_hash(class_name, loader_data);
   int d_index = dictionary()->hash_to_index(d_hash);