8235829: graal crashes with Zombie.java test

Start ServiceThread before compiler threads, and run nmethod barriers for zgc before adding to the service thread queues, or posting events from the java thread.

Reviewed-by: pliden, dholmes, rehn

src/hotspot/share/code/nmethod.cpp

@@ -1567,6 +1567,12 @@ void nmethod::flush_dependencies(bool delete_immediately) {
 // Transfer information from compilation to jvmti
 void nmethod::post_compiled_method_load_event(JvmtiThreadState* state) {
 
+  // Don't post this nmethod load event if it is already dying
+  // because the sweeper might already be deleting this nmethod.
+  if (is_not_entrant() && can_convert_to_zombie()) {
+    return;
+  }
+
   // This is a bad time for a safepoint.  We don't want
   // this nmethod to get unloaded while we're queueing the event.
   NoSafepointVerifier nsv;
@@ -1585,15 +1591,16 @@ void nmethod::post_compiled_method_load_event(JvmtiThreadState* state) {
   if (JvmtiExport::should_post_compiled_method_load()) {
     // Only post unload events if load events are found.
     set_load_reported();
-    // Keep sweeper from turning this into zombie until it is posted.
-    mark_as_seen_on_stack();
-
     // If a JavaThread hasn't been passed in, let the Service thread
     // (which is a real Java thread) post the event
     JvmtiDeferredEvent event = JvmtiDeferredEvent::compiled_method_load_event(this);
     if (state == NULL) {
+      // Execute any barrier code for this nmethod as if it's called, since
+      // keeping it alive looks like stack walking.
+      run_nmethod_entry_barrier();
       ServiceThread::enqueue_deferred_event(&event);
     } else {
+      // This enters the nmethod barrier outside in the caller.
       state->enqueue_event(&event);
     }
   }