nginx, memcached,tomcat 负载均衡memcached dead but subsys locked的问题

[root@server1 ~]# service memcached status
memcached dead but subsys locked
[root@server1 ~]# 
[root@server1 ~]# service memcached stop
Stopping memcached:                                        [FAILED]
[root@server1 ~]# 
[root@server1 ~]# sudo service memcached stop
Stopping memcached:                                        [FAILED]
[root@server1 ~]# 
[root@server1 ~]# service memcached status
memcached is stopped
[root@server1 ~]# 
[root@server1 ~]# sudo service memcached status
memcached is stopped
[root@server1 ~]# 
[root@server1 ~]# sudo service memcached start
Starting memcached:                                        [  OK  ]
[root@server1 ~]# 
[root@server1 ~]# sudo service memcached status
memcached dead but subsys locked
[root@server1 ~]# 

root用户下执行sudo service memcached stop后显示

Stopping memcached:                                        [FAILED]

我service memcached status显示：

   memcached is stopped

然后我service memcached start后显示

   Starting memcached:                                        [  OK  ]

可是，我再service memcached status却又显示：

    memcached dead but subsys locked

这是怎么回事？