Another app is currently holding the yum lock solution appears during yum update

[root@localhost wangcheng]# yum install yumex Existing lock /var/run/yum.pid: another copy isrunning as pid 3807. Another app is  currently holding theyumlock;   waiting for it to exit...Anotherappiscurrentlyholdingtheyumlock; waitingfor it to exit... Anotherappiscurrentlyholdingtheyumlock; waitingfor it to exit... Anotherappiscurrentlyholdingtheyumlock; waitingfor it to exit... Anotherappiscurrentlyholdingtheyumlock                             ; waitingforit to exit... Anotherappiscurrentlyholdingtheyumlock; waitingfor it to exit... Anotherappiscurrentlyholdingtheyumlock; waitingfor it to exit... Anotherappiscurrentlyholdingtheyumlock; waitingfor it to exit... Anotherappiscurrentlyholdingthe                             yum lock ; waiting for  it to exit...  Another app is currently holding the yum lock ;  waiting for  it to exit... why is this? I opened /var/run/ yum .pid, and it was just a number. Others may be that the system automatic upgrade is running, so yum is locked.  The lock can be forcibly unlocked by executing rm -rf /var/run/ yum .pid and your yum is ready to run.