https://blog.gongquiz.com/2022/04/30/%ec%9a%b4%ec%98%81%ec%b2%b4%ec%a0%9c%ec%9d%98-%ec%8a%a4%ec%bc%80%ec%a4%84%eb%a7%81-%ea%b8%b0%eb%b2%95-%ec%a4%91-%ec%84%a0%ec%a0%90preemptive-%ec%8a%a4%ec%bc%80%ec%a4%84%eb%a7%81%ec%97%90-%ed%95%b4/