static inline void transition_from_native(JavaThread *thread, JavaThreadState to) {

  {- -------------------------------------------
  (1) (assert)
      ---------------------------------------- -}

        assert((to & 1) == 0, "odd numbers are transitions states");
        assert(thread->thread_state() == _thread_in_native, "coming from wrong thread state");

  {- -------------------------------------------
  (1) 処理対象のスレッドの JavaThreadState を _thread_in_native_trans に変更する.

      なお, MP 環境の場合には
      VM Thread 側への visibility (sequential consistency) を保証する必要があるので, 
      変更後に以下のどちらかを行っている (See: SafepointSynchronize::begin()).
      * UseMembar オプションが指定されている場合:
        OrderAccess::fence() でメモリバリアを張る.
      * そうではない場合: 
        InterfaceSupport::serialize_memory() で serialize page への書き込みを行う.
      ---------------------------------------- -}

        // Change to transition state (assumes total store ordering!  -Urs)
        thread->set_thread_state(_thread_in_native_trans);

        // Make sure new state is seen by GC thread
        if (os::is_MP()) {
          if (UseMembar) {
            // Force a fence between the write above and read below
            OrderAccess::fence();
          } else {
            // Must use this rather than serialization page in particular on Windows
            InterfaceSupport::serialize_memory(thread);
          }
        }

  {- -------------------------------------------
  (1) 以下の 2つを確認し, もしこういった状況が発生していたら, 
      JavaThread::check_safepoint_and_suspend_for_native_trans() を呼んで待機する.
      * Safepoint 処理が開始されているかどうか  (= SafepointSynchronize::do_call_back()) 
      * カレントスレッドがサスペンドされているかどうか  (= thread->is_suspend_after_native())

      (なお, asynchronous exception はチェックしない. #TODO)


      (なお, CHECK_UNHANDLED_OOPS が #define されている場合には, 
       JavaThread::check_safepoint_and_suspend_for_native_trans() を呼んだ場合, 
       unhandled oop をクリアする処理も行っている.)
      ---------------------------------------- -}

        // We never install asynchronous exceptions when coming (back) in
        // to the runtime from native code because the runtime is not set
        // up to handle exceptions floating around at arbitrary points.
        if (SafepointSynchronize::do_call_back() || thread->is_suspend_after_native()) {
          JavaThread::check_safepoint_and_suspend_for_native_trans(thread);

          // Clear unhandled oops anywhere where we could block, even if we don't.
          CHECK_UNHANDLED_OOPS_ONLY(thread->clear_unhandled_oops();)
        }

  {- -------------------------------------------
  (1) 処理対象のスレッドの JavaThreadState を, to 引数の値に変更する.
      ---------------------------------------- -}

        thread->set_thread_state(to);
      }