JobScheduler Operations Center (JOC) provides two methods to end a running task. Both are reachable via the context menu of the task.

End a task with the "end" command

This command will send the xml command

 <kill_task ... immediately="no" />

to the JobScheduler engine.

It stops the task regular after the current execution of spooler_process() and continue with spooler_close(). No more iterations of spooler_process() will be executed.

This command has no effect for shell jobs.

End a task with the "kill immediately" command

This command will send the following xml command to the JobScheduler engine:

 <kill_task ... immediately="yes" />

It stops the process of the task and its child processes immediately by sending the SIGKILL signal.
Perhaps it is not possible to kill a task or one of its child processes because it is running in process state D (uninterruptable process).