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[Charles <2107340@xxxxxxxxxxxxxxxxxx>]

How to reproduce:

1. Fresh boot machine
2. See expected realtime parameters
ps -e -o pri,ni,comm | grep wire
 30 -11 pipewire
 19   0 pipewire
 30 -11 wireplumber
 30 -11 pipewire-pulse
3. Restart the services
 systemctl --user restart pipewire wireplumber pipewire-pulse
4. See unexpected realtime parameters
ps -e -o pri,ni,comm | grep wire
 19   0 pipewire
 19   0 pipewire
 19   0 wireplumber
 19   0 pipewire-pulse

I could only reproduce on 25.04, the bug isn't reproducible in questing
or 24.04 for me interestingly. I suspected the culprit was xdg-desktop-
portal after seeing https://github.com/flatpak/xdg-desktop-
portal/issues/1653 - but that fix isn't on noble or questing anyway. The
only difference between plucky and questing's xdg-desktop-portal is a
rebuild for fuse3. It may also be a kernel behaviour. There's hasn't
been much excitement in the git log relating to module-rt.c in pipewire
across the versions from noble to questing...

** Bug watch added: github.com/flatpak/xdg-desktop-portal/issues #1653
   https://github.com/flatpak/xdg-desktop-portal/issues/1653

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https://bugs.launchpad.net/bugs/2107340

Title:
  Pipewire fails to reacquire a realtime priority when restarted

Status in pipewire package in Ubuntu:
  Confirmed

Bug description:
  Pipewire tries to acquire a realtime priority when it starts via the
  libpipewire-module-rt plugin. By default, it prefers to use the
  org.freedesktop.portal.Realtime interface if xdg-desktop-portal is
  running (it checks if org.freedesktop.portal.Desktop exists on the
  session bus). If xdg-desktop-portal isn't running, it uses rtkit
  directly - see
  https://gitlab.freedesktop.org/pipewire/pipewire/-/tree/1.2.7/src/modules?ref_type=tags#L932.

  I started looking at this because I have an annoying issue with my
  audio which results in my speakers making popping noises frequently
  when they're outputting anything. I have another issue where my USB
  speakers are frequently not detected by pipewire without restarting
  it.

  When pipewire starts with a new session, it acquires a realtime
  priority by using rtkit directly because xdg-desktop-portal isn't
  running at this stage. However, if you restart pipewire manually later
  on when xdg-desktop-portal is running, pipewire uses the portal
  interface to request a realtime priority, and this fails with xdg-
  desktop-portal outputting the following error to the journal:

  Apr 13 02:58:01 farnsworth xdg-desktop-por[7283]: Realtime error:
  Could not get pidns: Could not fstatat ns/pid: Not a directory

  The libpipewire-module-rt plugin does have an option to disable usage
  of the portal interface for requesting a realtime priority
  (rtportal.enabled=false).

  This is tested with pipewire 1.2.7 in plucky.

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