1. Master1
 2. Master2

log-slave-updates

select @@global.log_slave_updates;

mysql> select @@global.log_slave_updates;
+----------------------------+
| @@global.log_slave_updates |
+----------------------------+
|                          1 |
+----------------------------+
1 row in set (0.00 sec)

log-bin = ....

mysql> show binary logs;

mysql> show binary logs;
ERROR 1381 (HY000): You are not using binary logging

STOP SLAVE;
FLUSH TABLES;
FLUSH LOGS;
SHOW BINARY LOGS;

CHANGE MASTER TO
    MASTER_HOST='IP or Hostname of Master2',
    MASTER_PORT=3306,
    MASTER_USER='...',
    MASTER_PASSWORD='...',
    MASTER_LOG_FILE='First Binary Log On Master2',
    MASTER_LOG_POS=4
;
SHOW SLAVE STATUSG

START SLAVE IO_THREAD;
DO SLEEP(10);
SHOW SLAVE STATUSG

START SLAVE SQL_THREAD;
DO SLEEP(10);
SHOW SLAVE STATUSG

SHOW MASTER STATUS;

SHOW BINARY LOGS;