Re: cyclictest: Unable to set scheduling policy / join real-time group or run as root

[Clark Williams <williams@redhat.com>]

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On Wed, 27 Feb 2013 18:22:20 +0200
Hartmut Behrens <hartmut.behrens@gmail.com> wrote:

> On Wed, Feb 27, 2013 at 6:09 PM, Clark Williams <williams@redhat.com> wrote:
> > What happens if you compile and run this program on your kernel?
> > #include <stdio.h>
> > #include <stdlib.h>
> > #include <sched.h>
> > #include <errno.h>
> > #include <memory.h>
> >
> > int main(int argc, char **argv)
> > {
> >         int ret;
> >         struct sched_param s;
> >
> >         memset(&s, 0, sizeof(s));
> >         s.sched_priority = 1;
> >         if ((sched_setscheduler(0, SCHED_FIFO, &s))) {
> >                 fprintf(stderr, "error changing policy: %s\n", strerror(errno));
> >                 exit(errno);
> >         }
> >         printf("successfully changed policy to SCHED_FIFO priority 1\n");
> >         exit(0);
> > }
> 
> When I run it as root I get "error changing policy: Operation not permitted".
> 
> Does this mean that some hard limits are not correctly set for root?

Well this is a new one on me. Some questions:

Do you have SELinux running?

Are there any files in /etc/security/limits.d other than the one you put
there?

Other than that I can't think of a reason why sched_setscheduler()
would fail as root. 

Clark

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