sched_setscheduler() behaviour changed??

[Mats Lindberg]

Sergey,

thanks for your comment - however it was my own mistake
in rt.c ...

static void setSchedPolicy( int policy )
{
  struct sched_param schedParam = { 0 };
  TRY(sched_getparam(0, &schedParam),-1);
  switch ( policy )
    {
    case SCHED_RR:
    case SCHED_FIFO:
      schedParam.sched_priority = MAX(1,schedParam.sched_priority);
      break;

    default:;
    }

  TRY(sched_setscheduler(0,policy,&schedParam),-1);
}
...

the sched_getparam() is called in SCHED_OTHER policy, where I would get a
negative or at least acceptable prio value in FBSD 5.x and 6.x
in FBSD 8.1 I got 63 which of course gives me EPERM cause I'm out of range.

Again thanks

2011/2/18 Sergey Kandaurov <pluknet at gmail.com>

> On 17 February 2011 12:50, Mats Lindberg <mats.w.lindberg at gmail.com>
> wrote:
> > All,
> > I have been using a small program /rt) that utilize the
> sched_setscheduler()
> > syscall to set the scheduling policy of a process to SCHED_RR. Been
> running
> > it FBSD 5.x and 6.x. Now when migrating to FBSD 8.1 I get EPERM back at
> me.
> > used to be able to run it like e.g.
> >> ./rt -sr -p2 -- prog
> >
> > which started <prog> in SCHED_RR policy with priority 2.
> >
> > now in FBSD 8.1 I get EPERM
> >
> > But If I do
> >> rtprio 10 ./rt -sr -p2 -- prog
> >
> > it I dont get EPERM.
> >
> > I'm always root when doing this.
> >
> > My problem is that I have customers that need to run their old 5.x 6.x
> > applications 'as is' in 8.1 whithout changing anything.
> >
>
> [just thinking aloud]
>
> Perhaps, you might have stumbled upon the change in
> sched_setscheduler() restricting permission to superuser:
>
> src/sys/posix4/p1003_1b.c#rev1.24.2.1
> MFC revision 1.27.
>    Don't allow non-root user to set a scheduler policy.
>
> @@ -195,6 +195,10 @@ int sched_setscheduler(struct thread *td
>        struct thread *targettd;
>        struct proc *targetp;
>
> +       /* Don't allow non root user to set a scheduler policy */
> +       if (suser(td) != 0)
> +               return (EPERM);
> +
>        e = copyin(uap->param, &sched_param, sizeof(sched_param));
>        if (e)
>                return (e);
>
>
> --
> wbr,
> pluknet
>