Cache and fill in virtual thread object for jvmtiFollowReferences cal…

…ls in ReferenceChainWalker Signed-off-by: Jack Lu <Jack.S.Lu@ibm.com>
eclipse-openj9 · Sep 3, 2024 · fe4e1c2 · fe4e1c2
1 parent 6dbed8a
commit fe4e1c2
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Showing 2 changed files with 25 additions and 1 deletion.
diff --git a/runtime/gc_base/ReferenceChainWalker.cpp b/runtime/gc_base/ReferenceChainWalker.cpp
@@ -88,6 +88,7 @@ j9gc_ext_reachable_objects_do(
 #endif /* J9VM_OPT_JVMTI */
 		referenceChainWalker.setTrackVisibleStackFrameDepth(0 != (walkFlags & J9_MU_WALK_TRACK_VISIBLE_FRAME_DEPTH));
 		referenceChainWalker.setPreindexInterfaceFields(0 != (walkFlags & J9_MU_WALK_PREINDEX_INTERFACE_FIELDS));
+		referenceChainWalker.includeVThreadObject();
 		/* walker configuration complete.  Scan objects... */
 		referenceChainWalker.scanReachableObjects(env);
 		referenceChainWalker.tearDown(env);
@@ -120,6 +121,7 @@ j9gc_ext_reachable_from_object_do(
 	MM_ReferenceChainWalker referenceChainWalker(env, TEMP_RCW_STACK_SIZE, userCallback, userData);
 	if (referenceChainWalker.initialize(env)) {
 		referenceChainWalker.setPreindexInterfaceFields(0 != (walkFlags & J9_MU_WALK_PREINDEX_INTERFACE_FIELDS));
+		referenceChainWalker.includeVThreadObject();
 		/* walker configuration complete.  Scan objects... */
 		referenceChainWalker.scanReachableFromObject(env, objectPtr);
 		referenceChainWalker.tearDown(env);
@@ -401,7 +403,11 @@ MM_ReferenceChainWalker::scanContinuationNativeSlots(J9Object *objectPtr)
 	if (MM_GCExtensions::needScanStacksForContinuationObject(currentThread, objectPtr, isConcurrentGC, isGlobalGC, beingMounted)) {
 		StackIteratorData localData;
 		localData.rootScanner = this;
-
+#if JAVA_SPEC_VERSION >= 19
+		if (_includeVThreadObject) {
+			_vThreadObject = VM_ContinuationHelpers::getThreadObjectForContinuation(currentThread, NULL, objectPtr);
+		}
+#endif /* JAVA_SPEC_VERSION >= 19 */
 		GC_VMThreadStackSlotIterator::scanContinuationSlots(currentThread, objectPtr, (void *)&localData, stackSlotIteratorForReferenceChainWalker, false, _trackVisibleStackFrameDepth);
 	}
 }
@@ -646,6 +652,12 @@ MM_ReferenceChainWalker::doStackSlot(J9Object **slotPtr, void *walkState, const
 
 	/* Only report heap objects */
 	if (isHeapObject(slotValue) && !_heap->objectIsInGap(slotValue)) {
+#if JAVA_SPEC_VERSION >= 19
+		if (_includeVThreadObject && (NULL == ((J9StackWalkState *)walkState)->walkThread->threadObject)) {
+			/* Fill in the virtual thread object for jvmtiFollowReferences calls. */
+			((J9StackWalkState *)walkState)->walkThread->threadObject = _vThreadObject;
+		}
+#endif /* JAVA_SPEC_VERSION >= 19 */
 		J9MM_StackSlotDescriptor stackSlotDescriptor = { ((J9StackWalkState *)walkState)->walkThread, (J9StackWalkState *)walkState };
 		if (J9_STACKWALK_SLOT_TYPE_JNI_LOCAL == ((J9StackWalkState *)walkState)->slotType) {
 			doSlot(slotPtr, J9GC_ROOT_TYPE_JNI_LOCAL, -1, (J9Object *)&stackSlotDescriptor);

diff --git a/runtime/gc_base/ReferenceChainWalker.hpp b/runtime/gc_base/ReferenceChainWalker.hpp
@@ -74,11 +74,16 @@ class MM_ReferenceChainWalker : public MM_RootScanner
 	bool _isProcessingOverflow; /**< Set when the queue is currently processing the overflow */
 	bool _isTerminating; /**< Set when no more callbacks should be queued */
 	bool _shouldPreindexInterfaceFields; /**< if true, indexes interface fields of the class being visited before class and superclass fields, otherwise, returns them in the order they appear in an object instance (CMVC 142897) */
+#if JAVA_SPEC_VERSION >= 19
+	bool _includeVThreadObject; /**< Set when VirtualThread object is needed by callback function. */
+	J9Object *_vThreadObject; /**< Cached object ref of VirtualThread object. */
+#endif /* JAVA_SPEC_VERSION >= 19 */
 	MM_ReferenceChainWalkerMarkMap *_markMap;	/**< Mark Map created for Reference Chain Walker */
 	MM_Heap *_heap; /**< Cached pointer to the heap */
 	void *_heapBase; /**< Cached value of the heap base */
 	void *_heapTop; /**< Cached value of the heap top */
 
+
 	void clearQueue();
 	void pushObject(J9Object *obj);
 	J9Object *popObject();
@@ -235,6 +240,10 @@ class MM_ReferenceChainWalker : public MM_RootScanner
 		_isProcessingOverflow(false),
 		_isTerminating(false),
 		_shouldPreindexInterfaceFields(true),	/* default to behaviour required for Java6/heap11 */
+#if JAVA_SPEC_VERSION >= 19
+		_includeVThreadObject(false),
+		_vThreadObject(NULL),
+#endif /* JAVA_SPEC_VERSION >= 19 */
 		_markMap(NULL),
 		_heap(NULL),
 		_heapBase(NULL),
@@ -259,6 +268,9 @@ class MM_ReferenceChainWalker : public MM_RootScanner
 		completeScan();
 	}
 
+#if JAVA_SPEC_VERSION >= 19
+	void includeVThreadObject() { _includeVThreadObject = true; }
+#endif /* JAVA_SPEC_VERSION >= 19 */
 	/**
 	 * Added to support bi-modal interface indexing in JVMTI (CMVC 142897).
 	 * Detail:  heap10 requires no pre-indexing in order to preserve Java5 behaviour but heap11 requires pre-indexing to pass a Java6 JCK