请看图
+----+------+-----------+------+------------+------+-------------------------+----------------------------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----+------+-----------+------+------------+------+-------------------------+----------------------------------------+
| 1 | root | localhost | test | Query | 78 | User sleep | select sleep(500) , id from my_test1_0 |
| 9 | root | localhost | NULL | Query | 71 | Waiting for table flush | flush tables |
| 10 | root | localhost | test | Field List | 24 | Waiting for table flush | |
| 11 | root | localhost | NULL | Query | 0 | init | show processlist |
+----+------+-----------+------+------------+------+-------------------------+----------------------------------------+
如果有个运行时间很长的语句，阻塞了flush tables运行，那么后续的所有语句都会被这个flush tables 所阻塞。