Re: [PATCH printk v1] printk: ringbuffer: Add KUnit test

[John Ogness]

Hi David,

On 2024-11-22, David Gow <davidgow@xxxxxxxxxx> wrote:
> It's a little unusual for a KUnit test -- particularly since it is
> time-based and uses lots of threads. This isn't a problem, but it's
> definitely a good thing that it's marked as slow. Additionally, KUnit
> doesn't track any extra threads spawned, so it requires a bit more
> care.
>
> There are a couple of issues (e.g., it crashes on non-SMP systems, a
> potential race, etc) and some minor suggestions below. In short, it'd
> be a good idea to move some of the initialisation and checks into the
> main test function, rather than the helper threads.
>
> Equally, it looks like there are a bunch of variables shared between
> kthreads — do these need to be checked with READ_ONCE()/WRITE_ONCE(),
> or made volatile, or something?

Agreed.

> In fact, I'm not sure why there's a separate start_test() and
> test_readerwriter() function -- or indeed, a separate kthread? Am I
> missing something, or could everything start_test() does be done from
> the main test function/kthread?

You are not missing anything. It is definitely awkward, mostly because
it was taken from parts of my own personal testing software. I will
implement all your suggestions. Thanks for the detailed review!

John