8286066: assert(k != __null) failed: klass not loaded caused by FillerObject_klass

src/hotspot/share/classfile/vmClassMacros.hpp

@@ -58,8 +58,6 @@
   do_klass(System_klass,                                java_lang_System                                      ) \
   do_klass(Throwable_klass,                             java_lang_Throwable                                   ) \
   do_klass(Error_klass,                                 java_lang_Error                                       ) \
-  /* GC support, should be loaded as early as possible */                                                       \
-  do_klass(FillerObject_klass,                          jdk_internal_vm_FillerObject                          ) \
   do_klass(ThreadDeath_klass,                           java_lang_ThreadDeath                                 ) \
   do_klass(Exception_klass,                             java_lang_Exception                                   ) \
   do_klass(RuntimeException_klass,                      java_lang_RuntimeException                            ) \
@@ -185,6 +183,8 @@
   do_klass(vector_VectorMask_klass,                     jdk_internal_vm_vector_VectorMask                     ) \
   do_klass(vector_VectorShuffle_klass,                  jdk_internal_vm_vector_VectorShuffle                  ) \
                                                                                                                 \
+  /* GC support */                                                                                              \
+  do_klass(FillerObject_klass,                          jdk_internal_vm_FillerObject                          ) \
                                                                                                                 \
   /*end*/
 

src/hotspot/share/classfile/vmClasses.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 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
@@ -30,6 +30,7 @@
 #include "classfile/systemDictionary.hpp"
 #include "classfile/vmClasses.hpp"
 #include "classfile/vmSymbols.hpp"
+#include "gc/shared/collectedHeap.hpp"
 #include "memory/metaspaceClosure.hpp"
 #include "memory/universe.hpp"
 #include "oops/instanceKlass.hpp"
@@ -122,10 +123,10 @@ void vmClasses::resolve_all(TRAPS) {
   // Preload commonly used klasses
   vmClassID scan = vmClassID::FIRST;
   // first do Object, then String, Class
+  resolve_through(VM_CLASS_ID(Object_klass), scan, CHECK);
+  CollectedHeap::set_filler_klass(vmClasses::Object_klass());
 #if INCLUDE_CDS
   if (UseSharedSpaces) {
-    resolve_through(VM_CLASS_ID(Object_klass), scan, CHECK);
-
     // It's unsafe to access the archived heap regions before they
     // are fixed up, so we must do the fixup as early as possible
     // before the archived java objects are accessed by functions
@@ -191,6 +192,8 @@ void vmClasses::resolve_all(TRAPS) {
   resolve_through(jsr292_group_end, scan, CHECK);
   resolve_until(vmClassID::LIMIT, scan, CHECK);
 
+  CollectedHeap::set_filler_klass(vmClasses::FillerObject_klass());
+
   _box_klasses[T_BOOLEAN] = vmClasses::Boolean_klass();
   _box_klasses[T_CHAR]    = vmClasses::Character_klass();
   _box_klasses[T_FLOAT]   = vmClasses::Float_klass();

src/hotspot/share/gc/shared/collectedHeap.cpp

@@ -60,6 +60,7 @@
 
 class ClassLoaderData;
 
+Klass* CollectedHeap::_filler_klass = NULL;
 size_t CollectedHeap::_filler_array_max_size = 0;
 
 class GCMessage : public FormatBuffer<1024> {
@@ -467,7 +468,7 @@ CollectedHeap::fill_with_object_impl(HeapWord* start, size_t words, bool zap)
     fill_with_array(start, words, zap);
   } else if (words > 0) {
     assert(words == min_fill_size(), "unaligned size");
-    ObjAllocator allocator(vmClasses::FillerObject_klass(), words);
+    ObjAllocator allocator(CollectedHeap::filler_klass(), words);
     allocator.initialize(start);
   }
 }

src/hotspot/share/gc/shared/collectedHeap.hpp

@@ -104,6 +104,10 @@ class CollectedHeap : public CHeapObj<mtGC> {
   size_t _capacity_at_last_gc;
   size_t _used_at_last_gc;
 
+  // First, set it to java_lang_Object.
+  // Then, set it to FillerObject after the FillerObject_klass loading is complete.
+  static Klass* _filler_klass;
+
  protected:
   // Not used by all GCs
   MemRegion _reserved;
@@ -204,6 +208,14 @@ class CollectedHeap : public CHeapObj<mtGC> {
     return _filler_array_max_size;
   }
 
+  static inline Klass* filler_klass() {
+    return _filler_klass;
+  }
+
+  static inline void set_filler_klass(Klass* k) {
+    _filler_klass = k;
+  }
+
   virtual Name kind() const = 0;
 
   virtual const char* name() const = 0;