linux-kernel - Re: [PATCH v2 1/3] list: test: Add test for list_del_init

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Date:   Tue, 8 Feb 2022 12:32:01 -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 1/3] list: test: Add test for list_del_init_careful()

On Mon, Feb 7, 2022 at 8:01 PM David Gow <davidgow@...gle.com> wrote:
>
> The list_del_init_careful() function was added[1] after the list KUnit
> test. Add a very basic test to cover it.
>
> Note that this test only covers the single-threaded behaviour (which
> matches list_del_init()), as is already the case with the test for
> list_empty_careful().
>
> [1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c6fe44d96fc1536af5b11cd859686453d1b7bfd1
>
> Signed-off-by: David Gow <davidgow@...gle.com>
> ---
>
> Changes since v1:
> https://lore.kernel.org/linux-kselftest/20220205061539.273330-1-davidgow@google.com/
> - Patch 1/3 unchanged
>
> ---
>  lib/list-test.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
>
> diff --git a/lib/list-test.c b/lib/list-test.c
> index ee09505df16f..976e9ae1f3c5 100644
> --- a/lib/list-test.c
> +++ b/lib/list-test.c
> @@ -161,6 +161,24 @@ static void list_test_list_del_init(struct kunit *test)
>         KUNIT_EXPECT_TRUE(test, list_empty_careful(&a));
>  }
>
> +static void list_test_list_del_init_careful(struct kunit *test)
> +{
> +       /* This test doesn't check correctness under concurrent access */

nit: I personally didn't read this comment in the intended way at first.
I'd personally find something like

NOTE: this doesn't test for concurrency/memory
ordering/however-you-want-to-word-it issues

a bit more readable.

> +       struct list_head a, b;
> +       LIST_HEAD(list);
> +
> +       list_add_tail(&a, &list);
> +       list_add_tail(&b, &list);
> +
> +       /* before: [list] -> a -> b */
> +       list_del_init(&a);

Is this supposed to use list_del_init_careful(&a)?
That would make it match the name of the test case.

> +       /* after: [list] -> b, a initialised */
> +
> +       KUNIT_EXPECT_PTR_EQ(test, list.next, &b);
> +       KUNIT_EXPECT_PTR_EQ(test, b.prev, &list);
> +       KUNIT_EXPECT_TRUE(test, list_empty_careful(&a));
> +}
> +
>  static void list_test_list_move(struct kunit *test)
>  {
>         struct list_head a, b;
> @@ -707,6 +725,7 @@ static struct kunit_case list_test_cases[] = {
>         KUNIT_CASE(list_test_list_replace_init),
>         KUNIT_CASE(list_test_list_swap),
>         KUNIT_CASE(list_test_list_del_init),
> +       KUNIT_CASE(list_test_list_del_init_careful),
>         KUNIT_CASE(list_test_list_move),
>         KUNIT_CASE(list_test_list_move_tail),
>         KUNIT_CASE(list_test_list_bulk_move_tail),
> --
> 2.35.0.263.gb82422642f-goog
>