kthread_stop —
stop a thread created by kthread_create.
int kthread_stop (struct task_struct * k);
Sets kthread_should_stop for k to return true, wakes it, and
waits for it to exit. Your threadfn must not call do_exit
itself if you use this function! This can also be called after
kthread_create instead of calling wake_up_process: the thread
will exit without calling threadfn.
Returns the result of threadfn, or -EINTR if wake_up_process
was never called.