[PATCH 5/5] testsuite/smokey: posix_clock: prevent false positive in timing-depending test

Jan Kiszka jan.kiszka at siemens.com
Tue Jan 15 18:14:16 CET 2019


On 14.01.19 18:35, Philippe Gerum wrote:
> clock_decrease_after_periodic_timer_first_tick checks that periodic
> interval timers based on CLOCK_REALTIME are not (pathologically)
> affected by the epoch going backwards.
> 
> To this end, we measure the actual time observed between two ticks of
> a periodic timer based on CLOCK_REALTIME with a call to
> clock_settime() injecting a negative offset in between, equivalent to
> five ticks.
> 
> Due to processing delays induced by clock_settime() and other latency,
> we could observe a duration which exceeds a tick by a few tenths of
> microseconds. Since we can't anticipate the amount of latency
> involved, let's accept a longer delay of at most two ticks.
> 
> This is still correct from the standpoint of the test, which verifies
> that no correlation exists between the clock offset injected by
> clock_settime() and the delay until the next tick generated by the
> affected clock.
> 
> Signed-off-by: Philippe Gerum <rpm at xenomai.org>
> ---
>   testsuite/smokey/posix-clock/posix-clock.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/testsuite/smokey/posix-clock/posix-clock.c b/testsuite/smokey/posix-clock/posix-clock.c
> index f672a9d52..3a638d41f 100644
> --- a/testsuite/smokey/posix-clock/posix-clock.c
> +++ b/testsuite/smokey/posix-clock/posix-clock.c
> @@ -417,7 +417,7 @@ static int clock_decrease_after_periodic_timer_first_tick(void)
>   
>   	diff = now.tv_sec * 1000000000ULL + now.tv_nsec -
>   		(timer.it_value.tv_sec * 1000000000ULL + timer.it_value.tv_nsec);
> -	if (!smokey_assert(diff < 1000000000))
> +	if (!smokey_assert(diff < 2000000000))
>   		return -EINVAL;
>   	
>   	ret = smokey_check_errno(read(t, &ticks, sizeof(ticks)));
> 

OK, this apparently addresses the issue Henning once brought up.

You sent the patch again outside of the queue but both look identical. Will take 
this one.

Finally: All 5 a also stable material as it looks like, right?

Jan

-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux



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