8298376: ZGC: thaws stackChunk with stale oops

Backport-of: ed8a212

Author: stefank

src/hotspot/share/oops/stackChunkOop.hpp

@@ -91,6 +91,8 @@ class stackChunkOopDesc : public instanceOopDesc {
   inline int max_thawing_size() const;
   inline void set_max_thawing_size(int value);
 
+  inline oop cont() const;
+  template<typename P>
   inline oop cont() const;
   inline void set_cont(oop value);
   template<typename P>

src/hotspot/share/oops/stackChunkOop.inline.hpp

@@ -86,7 +86,18 @@ inline void stackChunkOopDesc::set_max_thawing_size(int value)  {
   jdk_internal_vm_StackChunk::set_maxThawingSize(this, (jint)value);
 }
 
-inline oop stackChunkOopDesc::cont() const                { return jdk_internal_vm_StackChunk::cont(as_oop()); }
+inline oop stackChunkOopDesc::cont() const                { return UseCompressedOops ? cont<narrowOop>() : cont<oop>(); /* jdk_internal_vm_StackChunk::cont(as_oop()); */ }
+template<typename P>
+inline oop stackChunkOopDesc::cont() const                {
+  // The state of the cont oop is used by ZCollectedHeap::requires_barriers,
+  // to determine the age of the stackChunkOopDesc. For that to work, it is
+  // only the GC that is allowed to perform a load barrier on the oop.
+  // This function is used by non-GC code and therfore create a stack-local
+  // copy on the oop and perform the load barrier on that copy instead.
+  oop obj = jdk_internal_vm_StackChunk::cont_raw<P>(as_oop());
+  obj = (oop)NativeAccess<>::oop_load(&obj);
+  return obj;
+}
 inline void stackChunkOopDesc::set_cont(oop value)        { jdk_internal_vm_StackChunk::set_cont(this, value); }
 template<typename P>
 inline void stackChunkOopDesc::set_cont_raw(oop value)    { jdk_internal_vm_StackChunk::set_cont_raw<P>(this, value); }

src/hotspot/share/runtime/continuationJavaClasses.hpp

@@ -124,7 +124,8 @@ class jdk_internal_vm_StackChunk: AllStatic {
   static inline void set_maxThawingSize(oop chunk, int value);
 
   // cont oop's processing is essential for the chunk's GC protocol
-  static inline oop cont(oop chunk);
+  template<typename P>
+  static inline oop cont_raw(oop chunk);
   static inline void set_cont(oop chunk, oop value);
   template<typename P>
   static inline void set_cont_raw(oop chunk, oop value);

src/hotspot/share/runtime/continuationJavaClasses.inline.hpp

@@ -81,8 +81,9 @@ inline void jdk_internal_vm_StackChunk::set_parent_access(oop chunk, oop value)
   chunk->obj_field_put_access<decorators>(_parent_offset, value);
 }
 
-inline oop jdk_internal_vm_StackChunk::cont(oop chunk) {
-  return chunk->obj_field(_cont_offset);
+template<typename P>
+inline oop jdk_internal_vm_StackChunk::cont_raw(oop chunk) {
+  return (oop)RawAccess<>::oop_load(chunk->field_addr<P>(_cont_offset));
 }
 
 inline void jdk_internal_vm_StackChunk::set_cont(oop chunk, oop value) {