i dont know if this is good advise, but i found this, just google it

hit ctrl-c; that's the key combination to kill any currently running process in a bash shell or terminal.

to find out what's locking up yum, try running:

# ps aux | grep yum

note the pid number of the process and run this to kill the process:

# kill (insert pid number)

check to see if the process has been killed by rerunning:

# ps aux | grep yum

if not, rinse and repeat until the process is killed; some processes can be very stubborn.