Re: [LTP] [PATCH v2] sched/starvation: Choose from available cpus

Petr Vorel
2024-06-06T07:41:23Z

Hi Edward, Wei,

> Use the first available cpu in the sched_getaffinity set.

> This test was failing as a 32bit test for some arm architectures where
> cpu 0 does not support 32bit applications.

> Reviewed-by: Petr Vorel <pvorel@suse.cz>
> Signed-off-by: Edward Liaw <edliaw@google.com>
> ---
> .../kernel/sched/cfs-scheduler/starvation.c | 19 +++++++++++++++++--
> 1 file changed, 17 insertions(+), 2 deletions(-)

> diff --git a/testcases/kernel/sched/cfs-scheduler/starvation.c b/testcases/kernel/sched/cfs-scheduler/starvation.c
> index eb9fd6ff5..0fd45e281 100644
> --- a/testcases/kernel/sched/cfs-scheduler/starvation.c
> +++ b/testcases/kernel/sched/cfs-scheduler/starvation.c
> @@ -49,12 +49,27 @@ again:
> static void setup(void)
> {
> cpu_set_t mask;
> + int cpu = 0;
> + long ncpus = tst_ncpus_conf();

> CPU_ZERO(&mask);

> - CPU_SET(0, &mask);
> + /* Restrict test to a single cpu */
> + TST_EXP_PASS(sched_getaffinity(0, sizeof(mask), &mask));

> - TST_EXP_POSITIVE(sched_setaffinity(0, sizeof(mask), &mask));

Yeah, Wei was correct that both sched_getaffinity() and sched_setaffinity()
should use TST_EXP_PASS() because return only 0 on success (non-zero value is in
the mask, thus using TST_EXP_POSITIVE() was wrong. Ideally this would be in a
separate commit (before your changes), but I'm ok just to note it in the commit
message.

I was also thinking why test macros are used in setup() function (completely
unrelated to the change), I would just use plain code:

if (!sched_getaffinity(0, sizeof(mask), &mask))
tst_brk(TBROK | TERRNO, "sched_getaffinity() failed");

> + if (CPU_COUNT(&mask) == 0)
> + tst_brk(TBROK, "No cpus available");

I was thinking a while and looking in other software which uses CPU_COUNT().
And agree this should be probably tst_brk(TBROK)

Reviewed-by: Petr Vorel <pvorel@suse.cz>

Kind regards,
Petr

> +
> + while (CPU_ISSET(cpu, &mask) == 0 && cpu < ncpus)
> + cpu++;
> +
> + CPU_ZERO(&mask);
> +
> + CPU_SET(cpu, &mask);
> +
> + TST_EXP_PASS(sched_setaffinity(0, sizeof(mask), &mask));
> +
> + tst_res(TINFO, "Set affinity to CPU %d", cpu);

> if (tst_parse_long(str_loop, &loop, 1, LONG_MAX))
> tst_brk(TBROK, "Invalid number of loop number '%s'", str_loop);

--
Mailing list info: https://lists.linux.it/listinfo/ltp