--- old/src/share/vm/jfr/dcmd/jfrDcmds.cpp	2019-09-27 13:25:58.697533497 +0800
+++ new/src/share/vm/jfr/dcmd/jfrDcmds.cpp	2019-09-27 13:25:58.596529939 +0800
@@ -434,7 +434,13 @@
 
   jobjectArray settings = NULL;
   if (_settings.is_set()) {
-    const int length = _settings.value()->array()->length();
+    int length = _settings.value()->array()->length();
+    if (length == 1) {
+      const char* c_str = _settings.value()->array()->at(0);
+      if (strcmp(c_str, "none") == 0) {
+        length = 0;
+      }
+    }
     settings = JfrJavaSupport::new_string_array(length, CHECK);
     assert(settings != NULL, "invariant");
     for (int i = 0; i < length; ++i) {
--- old/src/share/vm/jfr/jni/jfrJavaCall.cpp	2019-09-27 13:25:59.269553645 +0800
+++ new/src/share/vm/jfr/jni/jfrJavaCall.cpp	2019-09-27 13:25:59.164549946 +0800
@@ -184,7 +184,7 @@
   }
 }
 
-JfrJavaArguments::JfrJavaArguments(JavaValue* result) : _result(result), _klass(NULL), _name(NULL), _signature(NULL), _array_length(0) {
+JfrJavaArguments::JfrJavaArguments(JavaValue* result) : _result(result), _klass(NULL), _name(NULL), _signature(NULL), _array_length(-1) {
   assert(result != NULL, "invariant");
 }
 
@@ -193,7 +193,7 @@
   _klass(NULL),
   _name(NULL),
   _signature(NULL),
-  _array_length(0) {
+  _array_length(-1) {
   assert(result != NULL, "invariant");
   if (klass_name != NULL) {
     set_klass(klass_name, CHECK);
@@ -210,7 +210,7 @@
   _klass(NULL),
   _name(NULL),
   _signature(NULL),
-  _array_length(0) {
+  _array_length(-1) {
   assert(result != NULL, "invariant");
   if (klass != NULL) {
     set_klass(klass);
--- old/src/share/vm/jfr/jni/jfrJavaSupport.cpp	2019-09-27 13:25:59.837573651 +0800
+++ new/src/share/vm/jfr/jni/jfrJavaSupport.cpp	2019-09-27 13:25:59.733569988 +0800
@@ -166,7 +166,7 @@
 
   const int array_length = args->array_length();
 
-  if (array_length > 0) {
+  if (array_length >= 0) {
     array_construction(args, result, klass, array_length, CHECK);
   } else {
     object_construction(args, result, klass, THREAD);
--- old/src/share/vm/jfr/recorder/jfrRecorder.cpp	2019-09-27 13:26:00.393593236 +0800
+++ new/src/share/vm/jfr/recorder/jfrRecorder.cpp	2019-09-27 13:26:00.288589537 +0800
@@ -189,9 +189,6 @@
   if (!validate_recording_options(thread)) {
     return false;
   }
-  if (!JfrJavaEventWriter::initialize()) {
-    return false;
-  }
   if (!JfrOptionSet::configure(thread)) {
     return false;
   }
@@ -235,6 +232,9 @@
   ResourceMark rm;
   HandleMark hm;
 
+  if (!create_java_event_writer()) {
+    return false;
+  }
   if (!create_jvmti_agent()) {
     return false;
   }
@@ -276,6 +276,10 @@
 static JfrOSInterface* _os_interface = NULL;
 static JfrThreadSampling* _thread_sampling = NULL;
 
+bool JfrRecorder::create_java_event_writer() {
+  return JfrJavaEventWriter::initialize();
+}
+
 bool JfrRecorder::create_jvmti_agent() {
   return JfrOptionSet::allow_retransforms() ? JfrJvmtiAgent::create() : true;
 }
--- old/src/share/vm/jfr/recorder/jfrRecorder.hpp	2019-09-27 13:26:00.959613172 +0800
+++ new/src/share/vm/jfr/recorder/jfrRecorder.hpp	2019-09-27 13:26:00.855609509 +0800
@@ -42,6 +42,7 @@
 
   static bool create_checkpoint_manager();
   static bool create_chunk_repository();
+  static bool create_java_event_writer();
   static bool create_jvmti_agent();
   static bool create_os_interface();
   static bool create_post_box();
--- old/src/share/vm/jfr/support/jfrFlush.cpp	2019-09-27 13:26:01.508632509 +0800
+++ new/src/share/vm/jfr/support/jfrFlush.cpp	2019-09-27 13:26:01.406628917 +0800
@@ -62,7 +62,6 @@
 }
 
 void jfr_conditional_flush(JfrEventId id, size_t size, Thread* t) {
-  assert(jfr_is_event_enabled(id), "invariant");
   if (t->jfr_thread_local()->has_native_buffer()) {
     JfrStorage::Buffer* const buffer = t->jfr_thread_local()->native_buffer();
     if (LessThanSize<JfrStorage::Buffer>::evaluate(buffer, size)) {
--- old/src/share/vm/jfr/writers/jfrJavaEventWriter.cpp	2019-09-27 13:26:02.055651777 +0800
+++ new/src/share/vm/jfr/writers/jfrJavaEventWriter.cpp	2019-09-27 13:26:01.954648219 +0800
@@ -142,8 +142,7 @@
 bool JfrJavaEventWriter::initialize() {
   static bool initialized = false;
   if (!initialized) {
-    Thread* thread = Thread::current();
-    initialized = setup_event_writer_offsets(thread);
+    initialized = setup_event_writer_offsets(Thread::current());
   }
   return initialized;
 }
@@ -162,6 +161,7 @@
   // large enough to accommodate the "requested size".
   const bool is_valid = buffer->free_size() >= (size_t)(used + requested);
   u1* const new_current_position = is_valid ? buffer->pos() + used : buffer->pos();
+  assert(start_pos_offset != invalid_offset, "invariant");
   w->long_field_put(start_pos_offset, (jlong)buffer->pos());
   w->long_field_put(current_pos_offset, (jlong)new_current_position);
   // only update java writer if underlying memory changed
--- old/src/share/vm/jfr/writers/jfrJavaEventWriter.hpp	2019-09-27 13:26:02.607671220 +0800
+++ new/src/share/vm/jfr/writers/jfrJavaEventWriter.hpp	2019-09-27 13:26:02.505667627 +0800
@@ -33,14 +33,15 @@
 
 class JfrJavaEventWriter : AllStatic {
   friend class JfrCheckpointThreadClosure;
-  friend class JfrJavaEventWriterNotifyOperation;
   friend class JfrJavaEventWriterNotificationClosure;
+  friend class JfrJavaEventWriterNotifyOperation;
+  friend class JfrRecorder;
  private:
+  static bool initialize();
   static void notify(JavaThread* jt);
 
  public:
   static bool has_required_classes(TRAPS);
-  static bool initialize();
   static void notify();
   static jobject event_writer(Thread* t);
   static jobject new_event_writer(TRAPS);