Re: [PATCH v2 2/2] selftests: sched: skip cs_prctl_test for systems with core scheduling disabled

[Chris Hyser]

>From: Sinadin Shan <sinadin.shan@xxxxxxxxxx>
>Sent: Monday, February 24, 2025 7:10 AM
>To: Shrikanth Hegde; shuah@xxxxxxxxxx
>Cc: linux-kselftest@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Chris Hyser
>Subject: Re: [PATCH v2 2/2] selftests: sched: skip cs_prctl_test for systems with core scheduling disabled
>
>On 24-02-2025 01:49 pm, Shrikanth Hegde wrote:
...
>> If the self-tests are to be used in development flow, these checks may
>> not be sufficient.
>
>Right, this particular case was overlooked. To handle this, the test
>could take a path to the custom config as an argument. I shall work on
>getting this fixed.

I was thinking something along the lines of just calling the prctl. 

If you call it and SCHED_CORE is not configured, you will get an EINVAL. Unfortunately,
passing other bad values in the other prctl args will also give an EINVAL, but if you call it with a
non-existent PID (say max_pid + 1) it will generate an ESRCH if the code is present.

So something like (and I'd look up the maxpid on the actual system):

int check_core_sched()
{
        ret = prctl(PR_SCHED_CORE, PR_SCHED_CORE_GET, 32769, PIDTYPE_PID,                                                                                                                                                         
                         (unsigned long)&cookie);                                                                                                                                                                            

        printf("ret = %d\n", ret);                                                                                                                                                                             
        perror("Error:\n");     
}

-chrish