Status changed to 'Confirmed' because the bug affects multiple users.
** Changed in: xdg-desktop-portal (Ubuntu Plucky)
Status: New => Confirmed
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https://bugs.launchpad.net/bugs/2107340
Title:
[SRU] Pipewire fails to reacquire a realtime priority when restarted
Status in pipewire package in Ubuntu:
Triaged
Status in xdg-desktop-portal package in Ubuntu:
Triaged
Status in pipewire source package in Plucky:
Confirmed
Status in xdg-desktop-portal source package in Plucky:
Confirmed
Bug description:
[Impact]
Restarting the pipewire user daemon causes it to lose realtime privileges,
potentially resulting in hard-to-diagnose choppy audio.
[Test plan]
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. Ensure the realtime parameters are unchanged from before the restart,
ps -e -o pri,ni,comm | grep wire
30 -11 pipewire
19 0 pipewire
30 -11 wireplumber
30 -11 pipewire-pulse
[Regression potential]
Backporting both commit dd08d451e3019f4ec6285ecb14d4c746b6e1d420 and
522236e41043a558a825da4cee70ee31ce607147 has a very low regression potential.
The first change is purely refactoring commit, which enhances code clarity by
renaming functions and variables to better differentiate between pidfds and
/proc/$PID directory file descriptors without altering any underlying logic or
behavior. The second fixes a specific bug where a function was incorrectly
called with a pidfd instead of a /proc/$PID directory file descriptor,
introducing a new, correct pidfd-aware function. The PIDFD_GET_PID_NAMESPACE
ioctl is a standard Linux kernel interface for interacting with PID file
descriptors. Its usage here is straightforward and unlikely to cause unexpected
side effects if the underlying kernel support is present.
[Original report]
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.
[Additional information]
See the xdg-desktop-portal package rebuild here:
https://launchpad.net/~charles05/+archive/ubuntu/ppa/+packages
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/pipewire/+bug/2107340/+subscriptions
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