Re: [PATCH 10/16] sched: add resource limits for -deadline tasks.

[Juri Lelli]

On 04/24/2012 05:07 PM, Peter Zijlstra wrote:
> On Fri, 2012-04-06 at 09:14 +0200, Juri Lelli wrote:
> > From: Dario Faggioli<raistlin@xxxxxxxx>
> >
> > Add resource limits for non-root tasks in using the SCHED_DEADLINE
> > policy, very similarly to what already exists for RT policies.
> >
> > In fact, this patch:
> >   - adds the resource limit RLIMIT_DLDLINE, which is the minimum value
> >     a user task can use as its own deadline;
> >   - adds the resource limit RLIMIT_DLRTIME, which is the maximum value
> >     a user task can use as it own runtime.
> >
> > Notice that to exploit these, a modified version of the ulimit
> > utility and a modified resource.h header file are needed. They
> > both will be available on the website of the project.
> >
> > Signed-off-by: Dario Faggioli<raistlin@xxxxxxxx>
> > Signed-off-by: Juri Lelli<juri.lelli@xxxxxxxxx>
>
> I'm not sure this is the right way to go.. those existing things aren't
> entirely as useful/sane as one might hope either.
>
> The DLDLINE minimum is ok I guess, the DLRTIME one doesn't really do
> anything, by spawning multiple tasks one can still saturate the cpu and
> thus we have no effective control for unpriv users.
>
> Ideally DLRTIME would be a utilization cap per user and tracked in
> user_struct such that we can enforce a max utilization per user.
>
> This also needs a global (and possibly per-cgroup) user limit too to cap
> the total utilization of all users (excluding root) so that multiple
> users cannot combine their efforts in order to bring down the machine.
>
> In light of these latter controls the per-user control might be
> considered optional, furthermore I don't particularly like the rlimit
> infrastructure but I guess its the best we have for per-user like things
> if indeed we want to go there.

Ok, but considering what you said regarding setscheduler security problems:

On 04/24/2012 11:00 AM, Peter Zijlstra wrote:
> On Tue, 2012-04-24 at 09:21 +0200, Juri Lelli wrote:
> > >  Well, depends on how much effort will this turn to require. I personally
> > >  would prefer to be able to come out with a new release ASAP. Just to
> > >  continue the discussion with the most of the comments addressed and a
> > >  more updated code (I also have a mainline version of the patchset
> > >  quite ready).
> Right, one thing we can initially do is require root for using
> SCHED_DEADLINE and then when later work closes all the holes and we've
> added user bandwidth controls we can allow everybody in.

Are you suggesting to drop/postpone this to some later time?

Thanks,

- Juri
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