8238197: JFR: Rework setting and getting EventHandler

Reviewed-by: egahlin, jbachorik

Author: Markus Grönlund

src/hotspot/share/jfr/jni/jfrJavaSupport.cpp

@@ -759,72 +759,58 @@ bool JfrJavaSupport::is_excluded(jobject thread) {
   return native_thread != NULL ? native_thread->jfr_thread_local()->is_excluded() : is_thread_excluded(thread);
 }
 
+static const Klass* get_handler_field_descriptor(const Handle& h_mirror, fieldDescriptor* descriptor, TRAPS) {
+  assert(h_mirror.not_null(), "invariant");
+  assert(descriptor != NULL, "invariant");
+  Klass* const k = java_lang_Class::as_Klass(h_mirror());
+  assert(k->is_instance_klass(), "invariant");
+  InstanceKlass* const ik = InstanceKlass::cast(k);
+  if (ik->is_not_initialized()) {
+    ik->initialize(CHECK_NULL);
+  }
+  assert(ik->is_being_initialized() || ik->is_initialized(), "invariant");
+  const Klass* const typed_field_holder = ik->find_field(vmSymbols::eventHandler_name(),
+                                                         vmSymbols::jdk_jfr_internal_handlers_EventHandler_signature(),
+                                                         true,
+                                                         descriptor);
+  return typed_field_holder != NULL ? typed_field_holder : ik->find_field(vmSymbols::eventHandler_name(),
+                                                                          vmSymbols::object_signature(), // untyped
+                                                                          true,
+                                                                          descriptor);
+}
+
 jobject JfrJavaSupport::get_handler(jobject clazz, TRAPS) {
   DEBUG_ONLY(JfrJavaSupport::check_java_thread_in_vm(THREAD));
-  const oop klass_oop = JNIHandles::resolve(clazz);
-  assert(klass_oop != NULL, "invariant");
-  Klass* klass = java_lang_Class::as_Klass(klass_oop);
   HandleMark hm(THREAD);
-  Handle h_klass_oop(Handle(THREAD, klass->java_mirror()));
-  InstanceKlass* const instance_klass = static_cast<InstanceKlass*>(klass);
-  klass->initialize(CHECK_NULL);
-
-  fieldDescriptor event_handler_field;
-  Klass* f = instance_klass->find_field(
-    vmSymbols::eventHandler_name(),
-    vmSymbols::jdk_jfr_internal_handlers_EventHandler_signature(),
-    true, &event_handler_field);
-  if (f != NULL) {
-    oop ret = h_klass_oop->obj_field(event_handler_field.offset());
-    return ret != NULL ? JfrJavaSupport::local_jni_handle(ret, THREAD) : NULL;
+  const Handle h_mirror(Handle(THREAD, JNIHandles::resolve(clazz)));
+  assert(h_mirror.not_null(), "invariant");
+  fieldDescriptor handler_field_descriptor;
+  const Klass* const field_holder = get_handler_field_descriptor(h_mirror, &handler_field_descriptor, THREAD);
+  if (field_holder == NULL) {
+    // The only reason should be that klass initialization failed.
+    return NULL;
   }
-
-  fieldDescriptor object_field;
-  Klass* g = instance_klass->find_field(
-    vmSymbols::eventHandler_name(),
-    vmSymbols::object_signature(),
-    true, &object_field);
-  if (g != NULL) {
-    oop ret = h_klass_oop->obj_field(object_field.offset());
-    return ret != NULL ? JfrJavaSupport::local_jni_handle(ret, THREAD) : NULL;
-  }
-  assert(f == NULL && g == NULL, "no handler field for class");
-  return NULL;
+  assert(java_lang_Class::as_Klass(h_mirror()) == field_holder, "invariant");
+  oop handler_oop = h_mirror->obj_field(handler_field_descriptor.offset());
+  return handler_oop != NULL ? JfrJavaSupport::local_jni_handle(handler_oop, THREAD) : NULL;
 }
 
 bool JfrJavaSupport::set_handler(jobject clazz, jobject handler, TRAPS) {
   DEBUG_ONLY(JfrJavaSupport::check_java_thread_in_vm(THREAD));
-  const oop klass_oop = JNIHandles::resolve(clazz);
-  assert(klass_oop != NULL, "invariant");
-  const oop handler_oop = JNIHandles::resolve(handler);
-  assert(handler_oop != NULL, "invariant");
-  Klass* klass = java_lang_Class::as_Klass(klass_oop);
   HandleMark hm(THREAD);
-  Handle h_klass_oop(Handle(THREAD, klass->java_mirror()));
-  InstanceKlass* const instance_klass = static_cast<InstanceKlass*>(klass);
-  klass->initialize(CHECK_false);
-
-  fieldDescriptor event_handler_field;
-  Klass* f = instance_klass->find_field(
-    vmSymbols::eventHandler_name(),
-    vmSymbols::jdk_jfr_internal_handlers_EventHandler_signature(),
-    true, &event_handler_field);
-  if (f != NULL) {
-    h_klass_oop->obj_field_put(event_handler_field.offset(), handler_oop);
-    return true;
-  }
-
-  fieldDescriptor object_handler_field;
-  Klass* g = instance_klass->find_field(
-    vmSymbols::eventHandler_name(),
-    vmSymbols::object_signature(),
-    true, &object_handler_field);
-  if (g != NULL) {
-    h_klass_oop->obj_field_put(object_handler_field.offset(), handler_oop);
-    return true;
+  const Handle h_mirror(Handle(THREAD, JNIHandles::resolve(clazz)));
+  assert(h_mirror.not_null(), "invariant");
+  fieldDescriptor handler_field_descriptor;
+  const Klass* const field_holder = get_handler_field_descriptor(h_mirror, &handler_field_descriptor, THREAD);
+  if (field_holder == NULL) {
+    // The only reason should be that klass initialization failed.
+    return false;
   }
-  assert(f == NULL && g == NULL, "no handler field for class");
-  return false;
+  assert(java_lang_Class::as_Klass(h_mirror()) == field_holder, "invariant");
+  const oop handler_oop = JNIHandles::resolve(handler);
+  assert(handler_oop != NULL, "invariant");
+  h_mirror->obj_field_put(handler_field_descriptor.offset(), handler_oop);
+  return true;
 }
 
 void JfrJavaSupport::on_thread_start(Thread* t) {

src/jdk.jfr/share/classes/jdk/jfr/internal/Utils.java

@@ -445,23 +445,17 @@ static long nanosToTicks(long nanos) {
 
     public static synchronized EventHandler getHandler(Class<? extends jdk.internal.event.Event> eventClass) {
         Utils.ensureValidEventSubclass(eventClass);
-        try {
-            Field f = eventClass.getDeclaredField(EventInstrumentation.FIELD_EVENT_HANDLER);
-            SecuritySupport.setAccessible(f);
-            return (EventHandler) f.get(null);
-        } catch (NoSuchFieldException | IllegalArgumentException | IllegalAccessException e) {
-            throw new InternalError("Could not access event handler");
+        Object handler = JVM.getJVM().getHandler(eventClass);
+        if (handler == null || handler instanceof EventHandler) {
+            return (EventHandler) handler;
         }
+        throw new InternalError("Could not access event handler");
     }
 
     static synchronized void setHandler(Class<? extends jdk.internal.event.Event> eventClass, EventHandler handler) {
         Utils.ensureValidEventSubclass(eventClass);
-        try {
-            Field field = eventClass.getDeclaredField(EventInstrumentation.FIELD_EVENT_HANDLER);
-            SecuritySupport.setAccessible(field);
-            field.set(null, handler);
-        } catch (NoSuchFieldException | IllegalArgumentException | IllegalAccessException e) {
-            throw new InternalError("Could not access event handler");
+        if (!JVM.getJVM().setHandler(eventClass, handler)) {
+            throw new InternalError("Could not set event handler");
         }
     }