linux-kernel - Re: [PATCH v2 2/3] list: test: Add a test for list_is

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Date:   Tue, 8 Feb 2022 12:40:23 -0800
From:   Daniel Latypov <dlatypov@...gle.com>
To:     David Gow <davidgow@...gle.com>
Cc:     Shuah Khan <skhan@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        kunit-dev@...glegroups.com
Subject: Re: [PATCH v2 2/3] list: test: Add a test for list_is_head()

On Mon, Feb 7, 2022 at 8:02 PM David Gow <davidgow@...gle.com> wrote:
>
> list_is_head() was added recently[1], and didn't have a KUnit test. The
> implementation is trivial, so it's not a particularly exciting test, but
> it'd be nice to get back to full coverage of the list functions.
>
> [1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/include/linux/list.h?id=0425473037db40d9e322631f2d4dc6ef51f97e88
>
> Signed-off-by: David Gow <davidgow@...gle.com>

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

One very optional suggestion below.

> ---
>
> Changes since v1:
> https://lore.kernel.org/linux-kselftest/20220205061539.273330-2-davidgow@google.com/
> - Test both non-head elements of the same list and head elements of
>   different lists.
>
> ---
>  lib/list-test.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>
> diff --git a/lib/list-test.c b/lib/list-test.c
> index 976e9ae1f3c5..1960615d1a9f 100644
> --- a/lib/list-test.c
> +++ b/lib/list-test.c
> @@ -252,6 +252,23 @@ static void list_test_list_bulk_move_tail(struct kunit *test)
>         KUNIT_EXPECT_EQ(test, i, 2);
>  }
>
> +static void list_test_list_is_head(struct kunit *test)
> +{
> +       struct list_head a, b, c;
> +
> +       /* Two lists: [a] -> b, [c] */
> +       INIT_LIST_HEAD(&a);
> +       INIT_LIST_HEAD(&c);
> +       list_add_tail(&b, &a);
> +
> +       KUNIT_EXPECT_TRUE(test, list_is_head(&a, &a));
> +       /* Non-head element of same list */
> +       KUNIT_EXPECT_FALSE(test, list_is_head(&a, &b));
> +       /* Head element of different list */
> +       KUNIT_EXPECT_FALSE(test, list_is_head(&a, &c));

very optional,
  KUNIT_EXPECT_FALSE_MSG(test, list_is_head(&a, &c), "Head of a
different list");
It goes over 80 char, so probably needs to be line-wrapped, and thus
doesn't reduce # of lines.

Given the simplicity of this function (checks that its args are
equal), I highly doubt it should ever fail, and so better error
messages aren't really much of a bonus.