8215575: C2 crash: assert(get_instanceKlass()->is_loaded()) failed: must be at least loaded

Set InstanceKlass::loaded before adding classes to the subklass list, which can be read concurrently by the compiler.

Reviewed-by: dholmes, eosterlund

src/hotspot/share/classfile/systemDictionary.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -1788,14 +1788,17 @@ void SystemDictionary::add_to_hierarchy(InstanceKlass* k, TRAPS) {
   assert(k != NULL, "just checking");
   assert_locked_or_safepoint(Compile_lock);
 
-  // Link into hierachy. Make sure the vtables are initialized before linking into
+  k->set_init_state(InstanceKlass::loaded);
+  // make sure init_state store is already done.
+  // The compiler reads the hierarchy outside of the Compile_lock.
+  // Access ordering is used to add to hierarchy.
+
+  // Link into hierachy.
   k->append_to_sibling_list();                    // add to superklass/sibling list
   k->process_interfaces(THREAD);                  // handle all "implements" declarations
-  k->set_init_state(InstanceKlass::loaded);
+
   // Now flush all code that depended on old class hierarchy.
   // Note: must be done *after* linking k into the hierarchy (was bug 12/9/97)
-  // Also, first reinitialize vtable because it may have gotten out of synch
-  // while the new class wasn't connected to the class hierarchy.
   CodeCache::flush_dependents_on(k);
 }
 

src/hotspot/share/oops/instanceKlass.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -3662,14 +3662,14 @@ void JNIid::verify(Klass* holder) {
   }
 }
 
-#ifdef ASSERT
 void InstanceKlass::set_init_state(ClassState state) {
+#ifdef ASSERT
   bool good_state = is_shared() ? (_init_state <= state)
                                                : (_init_state < state);
   assert(good_state || state == allocated, "illegal state transition");
+#endif
   _init_state = (u1)state;
 }
-#endif
 
 #if INCLUDE_JVMTI
 

src/hotspot/share/oops/instanceKlass.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -1242,11 +1242,7 @@ public:
 
 private:
   // initialization state
-#ifdef ASSERT
   void set_init_state(ClassState state);
-#else
-  void set_init_state(ClassState state) { _init_state = (u1)state; }
-#endif
   void set_rewritten()                  { _misc_flags |= _misc_rewritten; }
   void set_init_thread(Thread *thread)  { _init_thread = thread; }