8291830: jvmti/RedefineClasses/StressRedefine failed: assert(!is_null(v)) failed: narrow klass value can never be zero

Backport-of: fb6fd03233b0eb001e2995d20a079b6af31d2b9b

Author: TheRealMDoerr

src/hotspot/share/classfile/classLoaderData.cpp

@@ -821,6 +821,7 @@ void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
       _deallocate_list = new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(100, mtClass);
     }
     _deallocate_list->append_if_missing(m);
+    ResourceMark rm;
     log_debug(class, loader, data)("deallocate added for %s", m->print_value_string());
     ClassLoaderDataGraph::set_should_clean_deallocate_lists();
   }

src/hotspot/share/oops/klass.cpp

@@ -27,7 +27,7 @@
 #include "cds/heapShared.hpp"
 #include "classfile/classLoaderData.inline.hpp"
 #include "classfile/classLoaderDataGraph.inline.hpp"
-#include "classfile/javaClasses.hpp"
+#include "classfile/javaClasses.inline.hpp"
 #include "classfile/moduleEntry.hpp"
 #include "classfile/systemDictionary.hpp"
 #include "classfile/systemDictionaryShared.hpp"
@@ -63,10 +63,6 @@ oop Klass::java_mirror_no_keepalive() const {
   return _java_mirror.peek();
 }
 
-void Klass::replace_java_mirror(oop mirror) {
-  _java_mirror.replace(mirror);
-}
-
 bool Klass::is_cloneable() const {
   return _access_flags.is_cloneable_fast() ||
          is_subtype_of(vmClasses::Cloneable_klass());
@@ -786,7 +782,7 @@ void Klass::verify_on(outputStream* st) {
   }
 
   if (java_mirror_no_keepalive() != NULL) {
-    guarantee(oopDesc::is_oop(java_mirror_no_keepalive()), "should be instance");
+    guarantee(java_lang_Class::is_instance(java_mirror_no_keepalive()), "should be instance");
   }
 }
 

src/hotspot/share/oops/klass.hpp

@@ -268,7 +268,8 @@ class Klass : public Metadata {
   void set_archived_java_mirror(oop m) NOT_CDS_JAVA_HEAP_RETURN;
 
   // Temporary mirror switch used by RedefineClasses
-  void replace_java_mirror(oop mirror);
+  OopHandle java_mirror_handle() const { return _java_mirror; }
+  void swap_java_mirror_handle(OopHandle& mirror) { _java_mirror.swap(mirror); }
 
   // Set java mirror OopHandle to NULL for CDS
   // This leaves the OopHandle in the CLD, but that's ok, you can't release them.

src/hotspot/share/oops/oopHandle.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2022, 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
@@ -55,6 +55,10 @@ class OopHandle {
     return *this;
   }
 
+  void swap(OopHandle& copy) {
+    ::swap(_obj, copy._obj);
+  }
+
   inline oop resolve() const;
   inline oop peek() const;
 

src/hotspot/share/prims/jvmtiRedefineClasses.cpp

@@ -1318,22 +1318,22 @@ class RedefineVerifyMark : public StackObj {
  private:
   JvmtiThreadState* _state;
   Klass*            _scratch_class;
-  Handle            _scratch_mirror;
+  OopHandle         _scratch_mirror;
 
  public:
 
   RedefineVerifyMark(Klass* the_class, Klass* scratch_class,
                      JvmtiThreadState* state) : _state(state), _scratch_class(scratch_class)
   {
     _state->set_class_versions_map(the_class, scratch_class);
-    _scratch_mirror = Handle(_state->get_thread(), _scratch_class->java_mirror());
-    _scratch_class->replace_java_mirror(the_class->java_mirror());
+    _scratch_mirror = the_class->java_mirror_handle();  // this is a copy that is swapped
+    _scratch_class->swap_java_mirror_handle(_scratch_mirror);
   }
 
   ~RedefineVerifyMark() {
     // Restore the scratch class's mirror, so when scratch_class is removed
     // the correct mirror pointing to it can be cleared.
-    _scratch_class->replace_java_mirror(_scratch_mirror());
+    _scratch_class->swap_java_mirror_handle(_scratch_mirror);
     _state->clear_class_versions_map();
   }
 };