--- old/src/share/vm/classfile/classLoaderData.cpp	2016-05-26 23:24:11.074125651 -0400
+++ new/src/share/vm/classfile/classLoaderData.cpp	2016-05-26 23:24:09.006007797 -0400
@@ -67,6 +67,7 @@
 #include "runtime/javaCalls.hpp"
 #include "runtime/jniHandles.hpp"
 #include "runtime/mutex.hpp"
+#include "runtime/orderAccess.hpp"
 #include "runtime/safepoint.hpp"
 #include "runtime/synchronizer.hpp"
 #include "utilities/growableArray.hpp"
@@ -76,6 +77,11 @@
 #include "trace/tracing.hpp"
 #endif
 
+// helper function to avoid in-line casts
+template <typename T> static T* load_ptr_acquire(T* volatile *p) {
+  return static_cast<T*>(OrderAccess::load_ptr_acquire(p));
+}
+
 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;
 
 ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies) :
@@ -147,20 +153,21 @@
 }
 
 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
-  for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
+  for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
     klass_closure->do_klass(k);
     assert(k != k->next_link(), "no loops!");
   }
 }
 
 void ClassLoaderData::classes_do(void f(Klass * const)) {
+  assert_locked_or_safepoint(_metaspace_lock);
   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
     f(k);
   }
 }
 
 void ClassLoaderData::methods_do(void f(Method*)) {
-  for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
+  for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
     if (k->is_instance_klass()) {
       InstanceKlass::cast(k)->methods_do(f);
     }
@@ -179,7 +186,7 @@
 }
 
 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
-  for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
+  for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
     if (k->is_instance_klass()) {
       f(InstanceKlass::cast(k));
     }
@@ -188,6 +195,7 @@
 }
 
 void ClassLoaderData::modules_do(void f(ModuleEntry*)) {
+  assert_locked_or_safepoint(Module_lock);
   if (_modules != NULL) {
     for (int i = 0; i < _modules->table_size(); i++) {
       for (ModuleEntry* entry = _modules->bucket(i);
@@ -200,6 +208,7 @@
 }
 
 void ClassLoaderData::packages_do(void f(PackageEntry*)) {
+  assert_locked_or_safepoint(Module_lock);
   if (_packages != NULL) {
     for (int i = 0; i < _packages->table_size(); i++) {
       for (PackageEntry* entry = _packages->bucket(i);
@@ -325,10 +334,9 @@
     MutexLockerEx ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
     Klass* old_value = _klasses;
     k->set_next_link(old_value);
-    // Make sure linked class is stable, since the class list is walked without a lock
-    OrderAccess::storestore();
-    // link the new item into the list
-    _klasses = k;
+    // Link the new item into the list, making sure the linked class is stable
+    // since the list can be walked without a lock
+    OrderAccess::release_store_ptr(&_klasses, k);
   }
 
   if (publicize && k->class_loader_data() != NULL) {
@@ -352,6 +360,8 @@
   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
     if (k == scratch_class) {
       if (prev == NULL) {
+        // lock-free iteration will either see k or k->next_link, both
+        // of which are stable
         _klasses = k->next_link();
       } else {
         Klass* next = k->next_link();
@@ -390,42 +400,44 @@
 
 PackageEntryTable* ClassLoaderData::packages() {
   // Lazily create the package entry table at first request.
-  if (_packages == NULL) {
+  PackageEntryTable* packages = load_ptr_acquire(&_packages);
+  if (packages == NULL) {
     MutexLockerEx m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
     // Check if _packages got allocated while we were waiting for this lock.
-    if (_packages == NULL) {
-      _packages = new PackageEntryTable(PackageEntryTable::_packagetable_entry_size);
+    if ((packages = _packages) == NULL) {
+      packages = new PackageEntryTable(PackageEntryTable::_packagetable_entry_size);
+      // Ensure _packages is stable, since it is examined without a lock
+      OrderAccess::release_store_ptr(&_packages, packages);
     }
   }
-  return _packages;
+  return packages;
 }
 
 ModuleEntryTable* ClassLoaderData::modules() {
   // Lazily create the module entry table at first request.
-  if (_modules == NULL) {
+  ModuleEntryTable* modules = load_ptr_acquire(&_modules);
+  if (modules == NULL) {
     MutexLocker m1(Module_lock);
-    // Check again if _modules has been allocated while we were getting this lock.
-    if (_modules != NULL) {
-      return _modules;
-    }
-
-    ModuleEntryTable* temp_table = new ModuleEntryTable(ModuleEntryTable::_moduletable_entry_size);
-    // Each loader has one unnamed module entry. Create it before
-    // any classes, loaded by this loader, are defined in case
-    // they end up being defined in loader's unnamed module.
-    temp_table->create_unnamed_module(this);
-
-    {
-      MutexLockerEx m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
-      // Ensure _modules is stable, since it is examined without a lock
-      OrderAccess::storestore();
-      _modules = temp_table;
+    // Check if _modules got allocated while we were waiting for this lock.
+    if ((modules = _modules) == NULL) {
+      modules = new ModuleEntryTable(ModuleEntryTable::_moduletable_entry_size);
+      // Each loader has one unnamed module entry. Create it before
+      // any classes, loaded by this loader, are defined in case
+      // they end up being defined in loader's unnamed module.
+      modules->create_unnamed_module(this);
+
+      {
+        MutexLockerEx m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
+        // Ensure _modules is stable, since it is examined without a lock
+        OrderAccess::release_store_ptr(&_modules, modules);
+      }
     }
   }
-  return _modules;
+  return modules;
 }
 
 oop ClassLoaderData::keep_alive_object() const {
+  assert_locked_or_safepoint(_metaspace_lock);
   assert(!keep_alive(), "Don't use with CLDs that are artificially kept alive");
   return is_anonymous() ? _klasses->java_mirror() : class_loader();
 }
@@ -499,30 +511,32 @@
   // to create smaller arena for Reflection class loaders also.
   // The reason for the delayed allocation is because some class loaders are
   // simply for delegating with no metadata of their own.
-  if (_metaspace == NULL) {
-    MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
-    // Check again if metaspace has been allocated while we were getting this lock.
-    if (_metaspace != NULL) {
-      return _metaspace;
-    }
-    if (this == the_null_class_loader_data()) {
-      assert (class_loader() == NULL, "Must be");
-      set_metaspace(new Metaspace(_metaspace_lock, Metaspace::BootMetaspaceType));
-    } else if (is_anonymous()) {
-      if (class_loader() != NULL) {
-        log_trace(class, loader, data)("is_anonymous: %s", class_loader()->klass()->internal_name());
-      }
-      set_metaspace(new Metaspace(_metaspace_lock, Metaspace::AnonymousMetaspaceType));
-    } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
-      if (class_loader() != NULL) {
-        log_trace(class, loader, data)("is_reflection: %s", class_loader()->klass()->internal_name());
+  Metaspace* metaspace = load_ptr_acquire(&_metaspace);
+  if (metaspace == NULL) {
+    MutexLockerEx ml(_metaspace_lock,  Mutex::_no_safepoint_check_flag);
+    // Check if _metaspace got allocated while we were waiting for this lock.
+    if ((metaspace = _metaspace) == NULL) {
+      if (this == the_null_class_loader_data()) {
+        assert (class_loader() == NULL, "Must be");
+        metaspace = new Metaspace(_metaspace_lock, Metaspace::BootMetaspaceType);
+      } else if (is_anonymous()) {
+        if (class_loader() != NULL) {
+          log_trace(class, loader, data)("is_anonymous: %s", class_loader()->klass()->internal_name());
+        }
+        metaspace = new Metaspace(_metaspace_lock, Metaspace::AnonymousMetaspaceType);
+      } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
+        if (class_loader() != NULL) {
+          log_trace(class, loader, data)("is_reflection: %s", class_loader()->klass()->internal_name());
+        }
+        metaspace = new Metaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType);
+      } else {
+        metaspace = new Metaspace(_metaspace_lock, Metaspace::StandardMetaspaceType);
       }
-      set_metaspace(new Metaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType));
-    } else {
-      set_metaspace(new Metaspace(_metaspace_lock, Metaspace::StandardMetaspaceType));
+      // Ensure _metaspace is stable, since it is examined without a lock
+      OrderAccess::release_store_ptr(&_metaspace, metaspace);
     }
   }
-  return _metaspace;
+  return metaspace;
 }
 
 JNIHandleBlock* ClassLoaderData::handles() const           { return _handles; }
@@ -638,6 +652,7 @@
 #endif // PRODUCT
 
 void ClassLoaderData::verify() {
+  assert_locked_or_safepoint(_metaspace_lock);
   oop cl = class_loader();
 
   guarantee(this == class_loader_data(cl) || is_anonymous(), "Must be the same");
@@ -656,7 +671,7 @@
 }
 
 bool ClassLoaderData::contains_klass(Klass* klass) {
-  for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
+  for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
     if (k == klass) return true;
   }
   return false;
@@ -1046,6 +1061,7 @@
 
   // Find the first klass in the CLDG.
   while (cld != NULL) {
+    assert_locked_or_safepoint(cld->metaspace_lock());
     klass = cld->_klasses;
     if (klass != NULL) {
       _next_klass = klass;
@@ -1063,6 +1079,7 @@
 
   // No more klasses in the current CLD. Time to find a new CLD.
   ClassLoaderData* cld = klass->class_loader_data();
+  assert_locked_or_safepoint(cld->metaspace_lock());
   while (next == NULL) {
     cld = cld->next();
     if (cld == NULL) {
--- old/src/share/vm/classfile/classLoaderData.hpp	2016-05-26 23:24:17.518492889 -0400
+++ new/src/share/vm/classfile/classLoaderData.hpp	2016-05-26 23:24:15.450375036 -0400
@@ -216,8 +216,6 @@
   ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies);
   ~ClassLoaderData();
 
-  void set_metaspace(Metaspace* m) { _metaspace = m; }
-
   JNIHandleBlock* handles() const;
   void set_handles(JNIHandleBlock* handles);