Re: [PATCH v4 3/3] kselftest: Extend vDSO selftest to clock_getres

Vincenzo Frascino
2019-05-28T17:05:37Z

Hi Christophe,

On 28/05/2019 18:01, Christophe Leroy wrote:
> Vincenzo Frascino <vincenzo.frascino@arm.com> a écrit :
>
>> Hi Michael,
>>
>> thank you for your reply.
>>
>> On 28/05/2019 07:19, Michael Ellerman wrote:
>>> Vincenzo Frascino <vincenzo.frascino@arm.com> writes:
>>>
>>>> The current version of the multiarch vDSO selftest verifies only
>>>> gettimeofday.
>>>>
>>>> Extend the vDSO selftest to clock_getres, to verify that the
>>>> syscall and the vDSO library function return the same information.
>>>>
>>>> The extension has been used to verify the hrtimer_resoltion fix.
>>>
>>> This is passing for me even without patch 1 applied, shouldn't it fail
>>> without the fix? What am I missing?
>>>
>>
>> This is correct, because during the refactoring process I missed an "n" :)
>>
>> if·((x.tv_sec·!=·y.tv_sec)·||·(x.tv_sec·!=·y.tv_sec))
>>
>> Should be:
>>
>> if·((x.tv_sec·!=·y.tv_sec)·||·(x.tv_nsec·!=·y.tv_nsec))
>
> Maybe you'd better use timercmp() from sys/time.h
>

timercmp() takes "struct timeval" not "struct timespec".

> Christophe
>
>>
>> My mistake, I am going to fix the test and re-post v5 of this set.
>>
>> Without my patch if you pass "highres=off" to the kernel (as a command line
>> parameter) it leads to a broken implementation of clock_getres since
>> the value
>> of CLOCK_REALTIME_RES does not change at runtime.
>>
>> Expected result (with highres=off):
>>
>> # uname -r
>> 5.2.0-rc2
>> # ./vdso_clock_getres
>> clock_id: CLOCK_REALTIME [FAIL]
>> clock_id: CLOCK_BOOTTIME [PASS]
>> clock_id: CLOCK_TAI [PASS]
>> clock_id: CLOCK_REALTIME_COARSE [PASS]
>> clock_id: CLOCK_MONOTONIC [FAIL]
>> clock_id: CLOCK_MONOTONIC_RAW [PASS]
>> clock_id: CLOCK_MONOTONIC_COARSE [PASS]
>>
>> The reason of this behavior is that the only clocks supported by getres on
>> powerpc are CLOCK_REALTIME and CLOCK_MONOTONIC, the rest on the clocks use
>> always syscalls.
>>
>>> # uname -r
>>> 5.2.0-rc2-gcc-8.2.0
>>>
>>> # ./vdso_clock_getres
>>> clock_id: CLOCK_REALTIME [PASS]
>>> clock_id: CLOCK_BOOTTIME [PASS]
>>> clock_id: CLOCK_TAI [PASS]
>>> clock_id: CLOCK_REALTIME_COARSE [PASS]
>>> clock_id: CLOCK_MONOTONIC [PASS]
>>> clock_id: CLOCK_MONOTONIC_RAW [PASS]
>>> clock_id: CLOCK_MONOTONIC_COARSE [PASS]
>>>
>>> cheers
>>>
>>>> Cc: Shuah Khan <shuah@kernel.org>
>>>> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
>>>> ---
>>>>
>>>> Note: This patch is independent from the others in this series, hence it
>>>> can be merged singularly by the kselftest maintainers.
>>>>
>>>> tools/testing/selftests/vDSO/Makefile | 2 +
>>>> .../selftests/vDSO/vdso_clock_getres.c | 124 ++++++++++++++++++
>>>> 2 files changed, 126 insertions(+)
>>>> create mode 100644 tools/testing/selftests/vDSO/vdso_clock_getres.c
>>
>> --
>> Regards,
>> Vincenzo
>
>

--
Regards,
Vincenzo