Query execution was interrupted, max_statement_time exceeded版本：5.6.16

群里看见一个问题，在备份的时候，报如下错误：
[root@B28-19-75 bak]# mysqldump -root -p --single-transaction --master-data=2 --databases db1 db2 db3 db4 db5

Lock wait timeout exceeded; try restarting transaction参数控制Lock wait timeout exceeded; try restarting transaction锁等待超时。。回滚事务。。当事务1 获得锁start TRANSACTIONupdate user set username='gh4g' where id=