[LTP] [PATCH] open_posix/timer_getoverrun/2-3: Fix test for systems with low timer precision

[Joerg Vehlow]

> I didn't change timer resolution, I only used larger interval values
> as multiple of timer resolution:
>   intervalnsec = largeX * timer_resolution
>
ah ok
> I'd prefer we tweak the tolerance rather than make test run longer.
> I'm thinking just allow ~50ms of extra overruns, and don't be so
> strict about absolute number of overruns. (KVM guests and s390 lpars
> tend to suffer from higher steal time).
>
> diff --git 
> a/testcases/open_posix_testsuite/conformance/interfaces/timer_getoverrun/2-3.c 
> b/testcases/open_posix_testsuite/conformance/interfaces/timer_getoverrun/2-3.c 
>
> index 96b7d01e6ffe..66f8b583a5a6 100644
> --- 
> a/testcases/open_posix_testsuite/conformance/interfaces/timer_getoverrun/2-3.c
> +++ 
> b/testcases/open_posix_testsuite/conformance/interfaces/timer_getoverrun/2-3.c
> @@ -94,11 +94,17 @@ int main(void)
>
>         valuensec = tsres.tv_nsec;
>         intervalnsec = 2 * valuensec;
> -       //expectedoverruns = (1000000000 - valuensec) / intervalnsec;
>         expectedoverruns = 1000000000 / intervalnsec - 1;
>
> +       /*
> +        * waking up from sleep isn't instant, we can overshoot.
> +        * Allow up to ~50ms worth of extra overruns.
> +        */
> +       fudge = 50000000 / intervalnsec + 1;
> +
>         printf("value = %d sec, interval = %d nsec, "
> -              "expected overruns = %d\n", 1, intervalnsec, 
> expectedoverruns);
> +              "expected overruns = %d, fudge = %d\n", 1,
> +              intervalnsec, expectedoverruns, fudge);
>
>         its.it_interval.tv_sec = 0;
>         its.it_interval.tv_nsec = intervalnsec;
> @@ -146,7 +152,6 @@ int main(void)
>          * extra expiries after the nanosleep completes so do
>          * a range check.
>          */
> -       fudge = expectedoverruns / 100;
>         if (overruns >= expectedoverruns && overruns < 
> expectedoverruns + fudge) {
>                 printf("Test PASSED\n");
>                 return PTS_PASS;
>
I wonder if there was a way to do this more accurate, like busy waiting 
while signals
are blocked. But I would also be fine with your solution.