Date: Wed, 24 Apr 2024 07:44:31 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Nathan Chancellor <nathan@...nel.org>, shuah@...nel.org
Cc: tglx@...utronix.de, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] selftests: Make ksft_exit functions return void instead
 of int

On 4/17/24 09:37, Nathan Chancellor wrote:
> Commit f7d5bcd35d42 ("selftests: kselftest: Mark functions that
> unconditionally call exit() as __noreturn") marked functions that call
> exit() as __noreturn but it did not change the return type of these
> functions from 'void' to 'int' like it should have (since a noreturn
> function by definition cannot return an integer because it does not
> return...) because there are many tests that return the result of the
> ksft_exit function, even though it has never been used due to calling
> exit().
> 
> Prior to adding __noreturn, the compiler would not know that the functions
> that call exit() will not return, so code like
> 
>    void ksft_exit_fail(void)
>    {
>      exit(1);
>    }
> 
>    void ksft_exit_pass(void)
>    {
>      exit(0);
>    }
> 
>    int main(void)
>    {
>      int ret;
> 
>      ret = foo();
>      if (ret)
>        ksft_exit_fail();
>      ksft_exit_pass();
>    }
> 
> would cause the compiler to complain that main() does not return an
> integer, even though when ksft_exit_pass() is called, exit() will cause
> the program to terminate. So ksft_exit_...() returns int to make the
> compiler happy.
> 
>    int ksft_exit_fail(void)
>    {
>      exit(1);
>    }
> 
>    int ksft_exit_pass(void)
>    {
>      exit(0);
>    }
> 
>    int main(void)
>    {
>      int ret;
> 
>      ret = foo();
>      if (ret)
>        return ksft_exit_fail();
>      return ksft_exit_pass();
>    }
> 
> While this results in no warnings, it is weird semantically and it has
> issues as noted in the aforementioned __noreturn change. Now that
> __noreturn has been added to these functions, it is much cleaner to
> change the functions to 'void' and eliminate the return statements, as
> it has been made clear to the compiler that these functions terminate
> the program. Drop the return before all instances of ksft_exit_...() in
> a mechanical way. Only two manually changes were made to transform
> 
>    return !ret ? ksft_exit_pass() : ksft_exit_fail();
> 
> into the more idiomatic
> 
>    if (ret)
>      ksft_exit_fail();
>    ksft_exit_pass();
> 
> as well as a few style clean ups now that the code is shorter.
> 
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
>   tools/testing/selftests/clone3/clone3_clear_sighand.c        |  2 +-
>   tools/testing/selftests/clone3/clone3_set_tid.c              |  4 +++-
>   tools/testing/selftests/ipc/msgque.c                         | 11 +++++------
>   tools/testing/selftests/kselftest.h                          | 12 ++++++------
>   .../selftests/membarrier/membarrier_test_multi_thread.c      |  2 +-
>   .../selftests/membarrier/membarrier_test_single_thread.c     |  2 +-
>   tools/testing/selftests/mm/compaction_test.c                 |  6 +++---
>   tools/testing/selftests/mm/cow.c                             |  2 +-
>   tools/testing/selftests/mm/gup_longterm.c                    |  2 +-
>   tools/testing/selftests/mm/gup_test.c                        |  4 ++--
>   tools/testing/selftests/mm/ksm_functional_tests.c            |  2 +-
>   tools/testing/selftests/mm/madv_populate.c                   |  2 +-
>   tools/testing/selftests/mm/mkdirty.c                         |  2 +-
>   tools/testing/selftests/mm/pagemap_ioctl.c                   |  4 ++--
>   tools/testing/selftests/mm/soft-dirty.c                      |  2 +-
>   tools/testing/selftests/pidfd/pidfd_fdinfo_test.c            |  2 +-
>   tools/testing/selftests/pidfd/pidfd_open_test.c              |  4 +++-
>   tools/testing/selftests/pidfd/pidfd_poll_test.c              |  2 +-
>   tools/testing/selftests/pidfd/pidfd_test.c                   |  2 +-
>   tools/testing/selftests/resctrl/resctrl_tests.c              |  6 +++---
>   tools/testing/selftests/sync/sync_test.c                     |  3 +--
>   tools/testing/selftests/timers/adjtick.c                     |  4 ++--
>   tools/testing/selftests/timers/alarmtimer-suspend.c          |  4 ++--
>   tools/testing/selftests/timers/change_skew.c                 |  4 ++--
>   tools/testing/selftests/timers/freq-step.c                   |  4 ++--
>   tools/testing/selftests/timers/leap-a-day.c                  | 10 +++++-----
>   tools/testing/selftests/timers/leapcrash.c                   |  4 ++--
>   tools/testing/selftests/timers/mqueue-lat.c                  |  4 ++--
>   tools/testing/selftests/timers/posix_timers.c                | 12 ++++++------
>   tools/testing/selftests/timers/raw_skew.c                    |  6 +++---
>   tools/testing/selftests/timers/set-2038.c                    |  4 ++--
>   tools/testing/selftests/timers/set-tai.c                     |  4 ++--
>   tools/testing/selftests/timers/set-timer-lat.c               |  4 ++--
>   tools/testing/selftests/timers/set-tz.c                      |  4 ++--
>   tools/testing/selftests/timers/skew_consistency.c            |  4 ++--
>   tools/testing/selftests/timers/threadtest.c                  |  2 +-
>   tools/testing/selftests/timers/valid-adjtimex.c              |  6 +++---
>   tools/testing/selftests/x86/lam.c                            |  2 +-
>   38 files changed, 81 insertions(+), 79 deletions(-)
> 

Please generate separate patches for each test so it is easy to apply
them and also reduce merge conflicts.

You are missing maintainers for clone3, mm, pidfd tests. I can take these
through kselftest tree, but I need the changes split.

thanks,
-- Shuah

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