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Message-ID: <ba14458b-8f69-4947-ade2-d77e3290d4ed@linuxfoundation.org>
Date: Wed, 24 Apr 2024 10:00:12 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: shuah@...nel.org, 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 4/24/24 09:05, Nathan Chancellor wrote:
> On Wed, Apr 24, 2024 at 07:44:31AM -0600, Shuah Khan wrote:
>> 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.
>
> Is applying 30+ patches easier than applying just one? It is not a
> trivial amount of work for me to break this series up into individual
> patches but I will do so if you really want me to. I based this on the
> kselftest tree directly so that it would apply cleanly.
>
I am not asking each file to be a separate patch.
> How does breaking apart the changes reduce merge conflicts? The diff is
> going to be the same and semantic conflicts can still occur due to the
> kselftest.h changes.
selftest patches go through various repos. With this patch touching
several tests, there will be conflicts with multiple trees.
If this patch can't be split due to dependency on kselftest.h, I will
pull it in, but I do need you to include all the maintainers.
>
>> You are missing maintainers for clone3, mm, pidfd tests. I can take these
>> through kselftest tree, but I need the changes split.
>
> Fair enough, I should have CC'd them, although given this is a change to
> the kselftest API, I was not sure they would care too much.
>
The reason for cc'ing the maintainers is to keep them in the loop about this
change that could result in merge conflicts between kselftest tree and theirs.
Besides I would rather not have developers make calls on who should or shouldn't
care about a change. :)
thanks,
-- Shuah
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