--- signal
    ѿԤäƤ륹åɤ1ĺƳޤƳ줿
    åɤ ConditionVariable#wait [ConditionVariable]
    ǻꤷ mutex Υåߤޤ

    ֤ԤäƤ륹åɤäϡΥåɤ֤ޤ
    Ǥʤ nil ֤ޤ

