** Description changed: - [Impact] - Restarting the pipewire user daemon causes it to lose realtime privileges, potentially resulting in hard-to-diagnose choppy audio. + [ Impact ] + Restarting the pipewire user daemon causes it to lose realtime privileges, potentially resulting in hard-to-diagnose choppy audio. (xruns) - [Test plan] + [ 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. + [ Where problems could occur ] - [Original report] + The new method of getting pid namespaces from pidfd's could itself be + buggy in some unknown way. In the absolute worst case, this would imply + no sandboxed apps could request setting threads to realtime + (org.freedesktop.portal.Realtime) or access the GameMode API + (org.freedesktop.portal.GameMode). + + [ Other Info ] + This bug was only reproducible on specific versions of the kernel. The combination of this portal brittleness and the kernel currently shipped with Plucky is triggering it. + + Backporting both commit dd08d451e3019f4ec6285ecb14d4c746b6e1d420 and + dd08d451e3019f4ec6285ecb14d4c746b6e1d420 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/$PID directory file descriptors without + altering any underlying logic or behavior. + dd08d451e3019f4ec6285ecb14d4c746b6e1d420 fixes a specific bug where a + function was incorrectly called with a pidfd instead of a /proc/$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 (https://lwn.net/Articles/992740/). + + See the xdg-desktop-portal package rebuild here: + https://launchpad.net/~charles05/+archive/ubuntu/ppa/+packages + + Upstream discussion: https://github.com/flatpak/xdg-desktop- + portal/pull/1713 + + [ 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
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2107340 Title: [SRU] Pipewire fails to reacquire a realtime priority when restarted To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/pipewire/+bug/2107340/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
