Fix racing condition.
Fix racing condition.

kanru/aster,z7z8th/aster,walkingice/aster,cuongmv162/aster,walkingice/aster,z7z8th/aster,leijian/aster,kanru/aster,Ryan2009/aster,liuyq/aster,liuyq/aster,leijian/aster,cuongmv162/aster,kanru/aster,z7z8th/aster,walkingice/aster,Ryan2009/aster,Ryan2009/aster,leijian/aster,cuongmv162/aster,liuyq/aster