From 0bdd6f29a7a6033043755f005d54d55a0b071951 Mon Sep 17 00:00:00 2001
From: Babneet Singh <sbabneet@ca.ibm.com>
Date: Mon, 14 Nov 2022 08:10:11 -0500
Subject: [PATCH] Fix jvmtiGetThreadInfo

Set J9JavaVM->vthreadGroup in stdinit.c::standardInit to remove the
recursive dependency with JVMTI event callbacks, which causes an
infinite loop.

Closes: #16229

Signed-off-by: Babneet Singh <sbabneet@ca.ibm.com>
---
 runtime/jcl/common/stdinit.c | 19 ++++++++++++++++
 runtime/jvmti/jvmtiThread.c  | 43 +-----------------------------------
 runtime/oti/j9nonbuilder.h   |  3 +--
 3 files changed, 21 insertions(+), 44 deletions(-)

diff --git a/runtime/jcl/common/stdinit.c b/runtime/jcl/common/stdinit.c
index 81b10fae29a..142b2179766 100644
--- a/runtime/jcl/common/stdinit.c
+++ b/runtime/jcl/common/stdinit.c
@@ -301,6 +301,25 @@ standardInit(J9JavaVM *vm, char *dllName)
 			(void)(*(JNIEnv*)vmThread)->GetStaticFieldID((JNIEnv*)vmThread, clazz, "helpers", "Lcom/ibm/jit/JITHelpers;");
 			(*(JNIEnv*)vmThread)->DeleteLocalRef((JNIEnv*)vmThread, clazz);
 		}
+
+#if JAVA_SPEC_VERSION >= 19
+		clazz = (*(JNIEnv*)vmThread)->FindClass((JNIEnv*)vmThread, "java/lang/Thread$Constants");
+		if (NULL != clazz) {
+			jfieldID id = (*(JNIEnv*)vmThread)->GetStaticFieldID((JNIEnv*)vmThread, clazz, "VTHREAD_GROUP", "Ljava/lang/ThreadGroup;");
+			if (NULL != id) {
+				jobject tempGroup = (*(JNIEnv*)vmThread)->GetStaticObjectField((JNIEnv*)vmThread, clazz, id);
+				if (NULL != tempGroup) {
+					vm->vthreadGroup = (jobject)(*(JNIEnv*)vmThread)->NewGlobalRef((JNIEnv*)vmThread, tempGroup);
+				}
+			}
+			(*(JNIEnv*)vmThread)->DeleteLocalRef((JNIEnv*)vmThread, clazz);
+			if (NULL == vm->vthreadGroup) {
+				goto _fail;
+			}
+		} else {
+			goto _fail;
+		}
+#endif /* JAVA_SPEC_VERSION >= 19 */
 #endif /* !J9VM_IVE_RAW_BUILD */
 	}
 #endif
diff --git a/runtime/jvmti/jvmtiThread.c b/runtime/jvmti/jvmtiThread.c
index 327233010b0..554d1f89b0f 100644
--- a/runtime/jvmti/jvmtiThread.c
+++ b/runtime/jvmti/jvmtiThread.c
@@ -522,48 +522,7 @@ jvmtiGetThreadInfo(jvmtiEnv *env,
 					/* For virtual threads, check its state. */
 					if (JVMTI_VTHREAD_STATE_TERMINATED != J9VMJAVALANGVIRTUALTHREAD_STATE(currentThread, threadObject)) {
 						/* The thread group of a virtual thread is always j.l.Thread$Constants.VTHREAD_GROUP. */
-						JNIEnv *jniEnv = (JNIEnv *)currentThread;
-						jclass constants = vm->jlThreadConstants;
-						jfieldID id = vm->vthreadGroupID;
-						jobject tempGroup = NULL;
-
-						vm->internalVMFunctions->internalExitVMToJNI(currentThread);
-						if (NULL == constants) {
-							/* Cache the class. */
-							jclass localRef = (*jniEnv)->FindClass(jniEnv, "java/lang/Thread$Constants");
-							Assert_JVMTI_notNull(localRef);
-							constants = (jclass)((*jniEnv)->NewGlobalRef(jniEnv, localRef));
-							if (NULL != constants) {
-								vm->jlThreadConstants = constants;
-							} else {
-								rc = JVMTI_ERROR_OUT_OF_MEMORY;
-							}
-						}
-
-						if ((NULL != constants) && (NULL == id)) {
-							/* Cache the field id. */
-							id = (*jniEnv)->GetStaticFieldID(jniEnv, constants, "VTHREAD_GROUP", "Ljava/lang/ThreadGroup;");
-							if (NULL != id) {
-								vm->vthreadGroupID = id;
-							} else {
-								rc = JVMTI_ERROR_OUT_OF_MEMORY;
-							}
-						}
-
-						if ((NULL != constants) && (NULL != id)) {
-							tempGroup = (*jniEnv)->GetStaticObjectField(jniEnv, constants, id);
-							Assert_JVMTI_notNull(tempGroup);
-						}
-
-						/* VM access is required before invoking releaseVMThread. */
-						vm->internalVMFunctions->internalEnterVMFromJNI(currentThread);
-						if (JVMTI_ERROR_OUT_OF_MEMORY == rc) {
-							j9mem_free_memory(name);
-							goto release;
-						}
-
-						group = J9_JNI_UNWRAP_REFERENCE(tempGroup);
-						threadObject = (NULL == thread) ? targetThread->threadObject : J9_JNI_UNWRAP_REFERENCE(thread);
+						group = J9_JNI_UNWRAP_REFERENCE(vm->vthreadGroup);
 					}
 				} else {
 					/* For platform threads, a NULL vmthread indicates that a thread is terminated. */
diff --git a/runtime/oti/j9nonbuilder.h b/runtime/oti/j9nonbuilder.h
index e874e01a9bd..5f0a61251da 100644
--- a/runtime/oti/j9nonbuilder.h
+++ b/runtime/oti/j9nonbuilder.h
@@ -5799,8 +5799,7 @@ typedef struct J9JavaVM {
 	omrthread_monitor_t tlsFinalizersMutex;
 	struct J9Pool *tlsPool;
 	omrthread_monitor_t tlsPoolMutex;
-	jclass jlThreadConstants;
-	jfieldID vthreadGroupID;
+	jobject vthreadGroup;
 #endif /* JAVA_SPEC_VERSION >= 19 */
 } J9JavaVM;