void Thread::start(Thread* thread) {

  {- -------------------------------------------
  (1) (トレース出力)
      ---------------------------------------- -}

      trace("start", thread);

  {- -------------------------------------------
  (1) os::start_thread() で処理対象のスレッドを開始させる.
      (なお, 処理対象が JavaThread の場合には, 
       java_lang_Thread::set_thread_status() で
       スレッドの状態を java_lang_Thread::RUNNABLE にする処理も行う)

      (ただし, デバッグ用のオプションである DisableStartThread が指定されている場合には, 何もしない)
      ---------------------------------------- -}

      // Start is different from resume in that its safety is guaranteed by context or
      // being called from a Java method synchronized on the Thread object.
      if (!DisableStartThread) {
        if (thread->is_Java_thread()) {
          // Initialize the thread state to RUNNABLE before starting this thread.
          // Can not set it after the thread started because we do not know the
          // exact thread state at that time. It could be in MONITOR_WAIT or
          // in SLEEPING or some other state.
          java_lang_Thread::set_thread_status(((JavaThread*)thread)->threadObj(),
                                              java_lang_Thread::RUNNABLE);
        }
        os::start_thread(thread);
      }
    }