linux-kernel - Re: [PATCH] perf/hw_breakpoint: test: Skip the test if dependencies unmet

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Date:   Wed, 26 Oct 2022 11:31:10 -0700
From:   Daniel Latypov <dlatypov@...gle.com>
To:     David Gow <davidgow@...gle.com>
Cc:     Marco Elver <elver@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        kunit-dev@...glegroups.com,
        Brendan Higgins <brendanhiggins@...gle.com>,
        kasan-dev@...glegroups.com
Subject: Re: [PATCH] perf/hw_breakpoint: test: Skip the test if dependencies unmet

On Wed, Oct 26, 2022 at 7:10 AM David Gow <davidgow@...gle.com> wrote:
>
> Running the test currently fails on non-SMP systems, despite being
> enabled by default. This means that running the test with:
>
>  ./tools/testing/kunit/kunit.py run --arch x86_64 hw_breakpoint
>
> results in every hw_breakpoint test failing with:
>
>  # test_one_cpu: failed to initialize: -22
>  not ok 1 - test_one_cpu
>
> Instead, use kunit_skip(), which will mark the test as skipped, and give
> a more comprehensible message:
>
>  ok 1 - test_one_cpu # SKIP not enough cpus
>
> This makes it more obvious that the test is not suited to the test
> environment, and so wasn't run, rather than having run and failed.
>
> Signed-off-by: David Gow <davidgow@...gle.com>

Reviewed-by: Daniel Latypov <dlatypov@...gle.com>

This patch makes this command pass for me.
$ ./tools/testing/kunit/kunit.py run --arch x86_64
Since this test gets picked up by default, having it pass for common
uses of kunit.py is a priority, IMO.

(Note: if I add --alltests as well, these were the only failures)

I agree with Marco that TAP/KTAP saying "ok" for skipped tests can be
confusing at first.
But a SKIP status feels more appropriate than FAIL, so I'd strongly
like for this change to go in.

> ---
>  kernel/events/hw_breakpoint_test.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/events/hw_breakpoint_test.c b/kernel/events/hw_breakpoint_test.c
> index 5ced822df788..c57610f52bb4 100644
> --- a/kernel/events/hw_breakpoint_test.c
> +++ b/kernel/events/hw_breakpoint_test.c
> @@ -295,11 +295,11 @@ static int test_init(struct kunit *test)
>  {
>         /* Most test cases want 2 distinct CPUs. */
>         if (num_online_cpus() < 2)
> -               return -EINVAL;
> +               kunit_skip(test, "not enough cpus");

The only minor nit I have is that I'd personally prefer something like
  kunit_skip(test, "need >=2 cpus");
since that makes it clearer
a) that we must only have 1 CPU by default
b) roughly how one might address this.

Note: b) is a bit more complicated than I would like. The final
command is something like
$ ./tools/testing/kunit/kunit.py run --arch x86_64 --qemu_args='-smp
2' --kconfig_add='CONFIG_SMP=y'

But that's orthogonal to this patch.