[Pkg-utopia-maintainers] Bug#1082772: No realtime on Trixie

[Ray Guiliard]

I'm seeing no realtime threads from pipewire jack in Trixie. Pipewire
seems to be following rlimits for nice but not passing on realtime
priority. It appears to itself be gaining realtime priority for it's
data loop thread.

I can get realtime threads through yabridge and alsa but not pipewire
jack. Logging is not helping with the source of the problem. It was
entirely functional in bookworm.

I've tested with rtkit enabled and disabled. With rtkit enabled,
pipewire doesn't seem to request realtime access but other apps do
successfully. With rtkit disabled pipewire also doesn't pass realtime
priority to jack threads but I don't find logging complaining that it
tried and failed.

I have other applications (yabridge, bitwig/reaper through alsa) that
gain realtime access without issue but I'm also seeing ardour complain
that it can't get realtime IO threads and from the ardour code in git
that's entirely rlimit based.

If this is a bigger problem than pipewire there's some evidence for it
but a lot of evidence against. I haven't found any bug reports in the
pipewire bug tracker that seem related and post 1.4.2 release.

I'm using the xanmod 6.15.9-x64v3 kernel but also tested with 6.12 from
trixie. Neither have CONFIG_RT_GROUP_SCHED enabled so it doesn't seem
to be a cgroup interaction. Both have CONFIG_PREEMPT_DYNAMIC. I don't
have jackd or jackd2 installed though I did with bookworm and tested
with and without (after purge) and the ld.so.conf.d file is in place as
per the package. Even so I tested via pw-jack and no difference.