Kernel thread scheduling

[Vincenzo Scotti]

Hello,
I am actually studying kernel threads, and I have some doubts about them.
Let's take for example this snippet of code

static int thread_function(void *data)
{
	while (!kthread_should_stop()) {
		schedule();
	}

	pr_err("Stopped");
	return 0;
}

This way it works just fine, and waits until I call kthread_stop on it.
But if I comment out that schedule() call, it just hangs my system when I load
it (it is part of a module). I see that the loop-schedule-wakeup pattern is used
among all the others kernel threads. But I don't get why I need to call the
scheduler explicitly.
I know that the kernel is fully preemptible, and in my interpretation I thought
that it could stop every running thread, even in kernel space, using a
timer-based interrupt handler, to give cpu to other threads. Doesn't this
pattern resemble a voluntary preemption model?

Where am I wrong?