8046210: Missing memory barrier when reading init_lock

Reviewed-by: fparain, dcubed, mdoerr
Contributed-by: NBill Pittore <bill.pittore@oracle.com>

src/share/vm/oops/instanceKlass.cpp

@@ -504,6 +504,8 @@ objArrayOop InstanceKlass::signers() const {
 oop InstanceKlass::init_lock() const {
   // return the init lock from the mirror
   oop lock = java_lang_Class::init_lock(java_mirror());
+  // Prevent reordering with any access of initialization state
+  OrderAccess::loadload();
   assert((oop)lock != NULL || !is_not_initialized(), // initialized or in_error state
          "only fully initialized state can have a null lock");
   return lock;