To forcibly stop a service that has been executed, you must stop the tasks generated from the service.
You can forcibly stop tasks that are in the In Progress, Long Running, Waiting for Input, In Progress (with Error), and In Progress (Terminating) status. You enable the Forcibly Stop action in the Available Actions section of the Create/Edit Service window. A task that is stopped cannot be resumed. To restart the execution of a stopped task, you must resubmit the service that is associated with the task.