Re: [RFC PATCH v1.2 03/11] mm/damon/tests/core-kunit: test damon_rand()

[SeongJae Park <sj@kernel.org>]

On Thu, 25 Jun 2026 14:31:14 +0000 sashiko-bot@kernel.org wrote:

> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Low] The `counts` array computes a histogram of the generated random numbers, but the results are never validated.
> --
> 
> commit 545f6f76f7e281c6063dff020687345d3e3d45e4
> Author: SeongJae Park <sj@kernel.org>
> 
> mm/damon/tests/core-kunit: test damon_rand()
> 
> This commit adds a kunit test for damon_rand() to ensure the generated
> output falls within the specified bounds. It follows a recent change
> that optimized DAMON to use a per-context lockless PRNG.
> 
> > diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
> > index 1cfb8c176b873..eec7cb325a431 100644
> > --- a/mm/damon/tests/core-kunit.h
> > +++ b/mm/damon/tests/core-kunit.h
> > @@ -1460,6 +1460,22 @@ static void damon_test_is_last_region(struct kunit *test)
> >  	damon_free_target(t);
> >  }
> >  
> > +static void damon_test_rand(struct kunit *test)
> > +{
> > +	struct damon_ctx ctx;
> > +	int counts[10] = {};
> > +	int i;
> > +
> > +	prandom_seed_state(&ctx.rnd_state, get_random_u64());
> > +	for (i = 0; i < 10000; i++) {
> > +		unsigned long rnd = damon_rand(&ctx, 0, 10);
> > +
> > +		KUNIT_EXPECT_GE(test, rnd, 0);
> > +		KUNIT_EXPECT_LE(test, rnd, 9);
> > +		counts[rnd]++;
> 
> [Severity: Low]
> Are we missing a validation check here? The counts[] array computes a histogram
> of the generated random numbers, but the accumulated data is never read or
> verified after the loop terminates.

Good catch.  I will drop counts[] in the next revision.


Thanks,
SJ

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