--- exclusive_unlock { ... }
    ååԤˤʤäƤ륹åɤ¹Բǽ֤
    塢֥å¹Ԥޤ

    ֥åμ¹Ԥλޤǡåɤڤؤޤ

    self åƤʤ nil ֤ޤǤ
    self ֤ޤ

