8227011: Starting a JFR recording in response to JVMTI VMInit and / or Java agent premain corrupts memory

Reviewed-by: egahlin, rwestberg

src/hotspot/share/jfr/recorder/jfrRecorder.cpp

@@ -194,9 +194,6 @@ bool JfrRecorder::on_vm_start() {
     if (!validate_recording_options(thread)) {
       return false;
     }
-    if (!JfrJavaEventWriter::initialize()) {
-      return false;
-    }
     if (!JfrOptionSet::configure(thread)) {
       return false;
     }
@@ -246,6 +243,9 @@ bool JfrRecorder::create_components() {
   ResourceMark rm;
   HandleMark hm;
 
+  if (!create_java_event_writer()) {
+    return false;
+  }
   if (!create_jvmti_agent()) {
     return false;
   }
@@ -287,6 +287,10 @@ static JfrStringPool* _stringpool = NULL;
 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;
 }

src/hotspot/share/jfr/recorder/jfrRecorder.hpp

@@ -40,6 +40,7 @@ class JfrRecorder : public JfrCHeapObj {
  private:
   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();

src/hotspot/share/jfr/writers/jfrJavaEventWriter.cpp

@@ -135,8 +135,7 @@ static bool setup_event_writer_offsets(TRAPS) {
 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;
 }
@@ -155,6 +154,7 @@ jboolean JfrJavaEventWriter::flush(jobject writer, jint used, jint requested, Ja
   // 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

src/hotspot/share/jfr/writers/jfrJavaEventWriter.hpp

@@ -33,13 +33,14 @@ class Thread;
 
 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 initialize();
   static void notify();
   static jobject event_writer(Thread* t);
   static jobject new_event_writer(TRAPS);