mysql - cancel source call
By "source file", do you mean the source command in the commandline tool mysql?  If so, you need to kill that client, not the individual commands in PROCESSLIST.

Go to the OS's task manager.  (You may need to be root.)

# ps -axl | grep mysql  (or other args of your picking)
# kill -9 1234567       (using the PID from the ps)