Change from audio group to something else

[Kaj Ailomaa]

On Tue, Oct 28, 2014, at 01:45 PM, Felipe Sateler wrote:
> Hi Kaj,
> 
> On Tue, Oct 28, 2014 at 3:07 AM, Kaj Ailomaa <zequence at mousike.me> wrote:
> > I think I was able to figure out pretty much all about how the cgroups
> > tools and configs work (and what is possible), however, I never got
> > realtime scheduling to work Not sure why. Compiled a kernel with
> > CONFIG_RT_GROUP_SCHED on (which apparently is turned off nowadays),
> > which I believe is necessary.
> >
> > My goal was to first grant realtime privilege to any user, but only to
> > selected processes (like jackd). All seemed to be set up right, but no.
> > Wonder if anyone would consider this a security issue.
> 
> rtkit seems to do what you are proposing to do. It grants realtime
> privileges to selected processes. Although I'm not sure of the
> implementation details (ie, how does it determine it can grant or not
> the privilege), its description roughly correlates with what you are
> trying to accomplish.
> 

I've been meaning to check how that works for a long time (takes me a
lot of time to investigate, as there's a big lack of knowledge on my
side when it comes to a great many things). 
>From what I've read, some have said rtkit is old, which doesn't tell me
much. The idea seems very sound to me at least.

Would rtkit be the simplest and most generic solution if packaging jack
and making sure it gets RT privilege on any Debian based distro just by
installing the package?

> Except that...
> 
> > Heard that systemd might get in the way somehow, and I do have systemd
> > on this machine.
> 
> It depends on where were you starting your program, I belive. Please
> see this bug[1] and the related links for more details on why systemd
> causes problems for realtime services.
> 

Thanks.

> As I note in that bug log, I do not know what fiddling is necessary
> with cgroups to allow rt privileges. Perhaps with your research you
> know what needs to be done?
> 

I only worked out how cgroups is administered with the tools and
configs, and to the best of my knowledge I did everything right. I could
of course be missing something. I've read that someone else was having
problems using cgroups for RT on Debian, and was blaming systemd - but
from my view that is only hearsay for the time being. To make sure I did
things correctly, I'm going to try on a different distro, which is known
to work with cgroups and RT, just to make sure my implementations work -
and only then start investigating if and what in Debian is stopping it
to work.

> 
> If you are starting your program as a user, you should be OK though
> (according to the systemd realtime page linked in the bug log, but
> that page is horribly outdated, as the ControlGroup* directives were
> removed).
> 
> 
> [1]https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=747568
> 
> -- 
> 
> Saludos,
> Felipe Sateler
> 
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