Re: [Agnula-Developers] [ demudi-Feature Requests-723 ] Compile Muse 0.6.3 with givertcap support

["Jack O'Quin" <joq@io.com>]

guenter geiger <geiger@xdv.org> writes:

> For 2.6 there is another possibility, the realtime kernel module by
> Jack O'Quin (who is on the debian-multimedia list too and has provided
> us already with important insights into the working of JACK).
> Using this module the applications do not have to be changed.
> They can just use their "normal" priority settings mechanism.
> 
> Its downloadable at:
> http://www.joq.us/realtime/

One of the permission options provided by this module is `gid=29',
which grants realtime privileges to any process belonging to group
`audio'.  This fits the Debian structure nicely.

I believe this approach could form *part* of a systematic solution to
the overall realtime privileges problem.  The missing piece is a
corresponding solution for 2.4 kernels, which will continue being used
with audio for a long time.  It still runs better (when patched) for
low latencies, though with 2.6.3 latency is improving.  AFAIK, 2.4 is
still the default kernel for sarge, right?

The obvious solution would be to apply the rather large SELinux patch
from NSA.  This back-ports the entire LSM structure to 2.4.  I doubt
the Debian kernel maintainers would approve of that idea, and IMHO it
is overkill for the small changes needed to grant realtime access.

To my mind, a more practical solution for 2.4 would be something like
the `schedmlockpatch' kernel patch Kjetil Matheussen posted on LAD a
while back.

For this approach to be adopted by a major distribution like Debian
multimedia, I would recommend doing some additional work to make the
permission methods for both kernel versions look and behave similarly.
I would control them through the same interface in /proc/sys/kernel
(or some place like that).

I have done some thinking about this.  There was a good discussion on
LAD a few months back.  If there is interest I will make a specific
proposal, and maybe come up with a modified 2.4 patch for people to
experiement with.
-- 
  joq