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

Vincenzo Frascino
2019-06-04T14:21:10Z

On 04/06/2019 14:52, Christophe Leroy wrote:
>
>
> Le 04/06/2019 à 15:43, Vincenzo Frascino a écrit :
>> On 04/06/2019 14:39, Christophe Leroy wrote:
>>>
>>>
>>> Le 04/06/2019 à 15:32, Vincenzo Frascino a écrit :
>>>> Hi Christophe,
>>>>
>>>> On 04/06/2019 14:16, Christophe Leroy wrote:
>>>>> Hi Vincenzo
>>>>>
>>>>> Le 28/05/2019 à 13:57, Vincenzo Frascino 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))
>>>>>>
>>>>>> 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.
>>>>>
>>>>> vdso64 is supposed to implement CLOCK_{REALTIME/MONOTONIC}_COARSE, so I
>>>>> guess it should fail for them too ?
>>>>>
>>>>> Or is your test done on vdso32 ?
>>>>>
>>>>
>>>> Based on what I can see in kernel/vdso64 in 5.2-rc3:
>>>>
>>>> /*
>>>> * Exact prototype of clock_getres()
>>>> *
>>>> * int __kernel_clock_getres(clockid_t clock_id, struct timespec *res);
>>>> *
>>>> */
>>>> V_FUNCTION_BEGIN(__kernel_clock_getres)
>>>> .cfi_startproc
>>>> /* Check for supported clock IDs */
>>>> cmpwi cr0,r3,CLOCK_REALTIME
>>>> cmpwi cr1,r3,CLOCK_MONOTONIC
>>>> cror cr0*4+eq,cr0*4+eq,cr1*4+eq
>>>> bne cr0,99f
>>>>
>>>> li r3,0
>>>> cmpldi cr0,r4,0
>>>> crclr cr0*4+so
>>>> beqlr
>>>> lis r5,CLOCK_REALTIME_RES@h
>>>> ori r5,r5,CLOCK_REALTIME_RES@l
>>>> std r3,TSPC64_TV_SEC(r4)
>>>> std r5,TSPC64_TV_NSEC(r4)
>>>> blr
>>>>
>>>> /*
>>>> * syscall fallback
>>>> */
>>>> 99:
>>>> li r0,__NR_clock_getres
>>>> sc
>>>> blr
>>>> .cfi_endproc
>>>> V_FUNCTION_END(__kernel_clock_getres)
>>>>
>>>> it does not seem so for what concerns vdso64. I did run again the test both on
>>>> ppc and ppc64 qemu instances and the result is the same to what I reported in
>>>> this thread.
>>>>
>>>> Am I missing something?
>>>
>>> I was thinking about
>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5c929885f1bb
>>> but apparently clock_getres() was left aside. Should we do something
>>> about it ?
>>>
>>
>> Sure, but I would like this series to be merged first (since the topic is
>> different). I am happy, after that, to push a separate one on top that addresses
>> the problem.
>>
>> Please let me know if it works for you and Michael.
>
> No problem for myself.
>
> By the way, next time (or next spin ?) I recommend you to handle your
> patches independently and not as a series since they are all
> independant. It would have avoided confusion and the need for you to
> resend all 3 patches everytime you did a change in one of them.
>

Thanks for the advise, I will do next time.

> Christophe
>
>>
>>> Christophe
>>>
>>>>
>>>>> Christophe
>>>>>
>>>>>>
>>>>>>> # 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