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

Christophe Leroy
2019-05-28T17:01:32Z

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

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