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

rev 9061 : 8227011: Starting a JFR recording in response to JVMTI VMInit and / or Java agent premain corrupts memory
Reviewed-by: egahlin, rwestberg

@@ -140,12 +140,11 @@
 }
 
 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;
 }
 
 jboolean JfrJavaEventWriter::flush(jobject writer, jint used, jint requested, JavaThread* jt) {

@@ -160,10 +159,11 @@
   // "validity" is contextually defined here to mean
   // that some memory location was provided that is
   // 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
   if (buffer != current) {
     w->long_field_put(start_pos_address_offset, (jlong)buffer->pos_address());