8331735: UpcallLinker::on_exit races with GC when copying frame anchor

8286875: ProgrammableUpcallHandler::on_entry/on_exit access thread fields from native

Reviewed-by: mbalao
Backport-of: 91457e694353386737e325e6fa0253bcefb8d579

Author: gnu-andrew

src/hotspot/share/prims/universalUpcallHandler.cpp

@@ -131,21 +131,17 @@ void ProgrammableUpcallHandler::on_exit(OptimizedEntryBlob::FrameData* context)
   // restore previous handle block
   thread->set_active_handles(context->old_handles);
 
-  thread->frame_anchor()->zap();
-
   debug_only(thread->dec_java_call_counter());
 
+  thread->frame_anchor()->copy(&context->jfa);
+
   // Old thread-local info. has been restored. We are now back in native code.
   ThreadStateTransition::transition_from_java(thread, _thread_in_native);
 
-  thread->frame_anchor()->copy(&context->jfa);
-
   // Release handles after we are marked as being in native code again, since this
   // operation might block
   JNIHandleBlock::release_block(context->new_handles, thread);
 
-  assert(!thread->has_pending_exception(), "Upcall can not throw an exception");
-
   if (context->should_detach) {
     detach_current_thread();
   }