**Correction to comment #2** The 2026-07-20 note that HWE **7.0.0-28** + raw DRI3 had “zero” further hangs after a 3-day soak is **no longer accurate**. After that soak window, the same class of hang returned on **7.0.0-28-generic** with Mesa still **25.2.8-0ubuntu0.24.04.2** (no `LIBGL_DRI3_DISABLE`). Several kwin_x11 D-Bus wedges occurred from late July through 2026-08-03 (idle-blocked compositor; Xorg stays healthy; recovery = SIGKILL + restart kwin).
Comment #2’s notification-storm PASS on 7.0 still stands; day-to-day desktop use (especially **screen lock / DPMS**) continues to hit the race. **Environment (unchanged package-wise)** - Ubuntu 24.04.4, X11, Plasma 5.27 / kwin-x11 5.27.11 - mesa / libglx-mesa0 **25.2.8-0ubuntu0.24.04.2** - kernel **7.0.0-28-generic** (HWE) - Dell Precision 5690, Meteor Lake iGPU (Intel Arc MTL), compositing via GLX **New evidence — kwin_x11 blocking variant (2026-08-03)** Captured live with gdb while `org.kde.KWin` D-Bus was hung. CPU counters flat over 3s (blocked, not spinning). Main thread: ``` #0 poll (timeout=-1) #1 … libxcb … #2 xcb_wait_for_special_event #3–#5 … libgallium-25.2.8 … #6 loader_dri3_query_buffer_age ← Mesa 25.2.8 DRI3 loader #7 … libGLX_mesa.so.0 … #9 KWin::Compositor::composite #10 KWin::X11Compositor::composite #12 KWin::RenderLoop::frameRequested #13 KWin::RenderLoopPrivate::dispatch … QTimer → QEventLoop … ``` Full `thread apply all bt` attached (`gdb-kwin_x11-dri3-query-buffer- age-20260803.txt`). This is the same DRI3 Present / special-event wait family as the original plasmashell `glXSwapBuffers` hang (comment #1), observed here in `loader_dri3_query_buffer_age` on the kwin composite path. **Reproducer (reliable on this machine)** Trigger is **lock the session, then force DPMS off, then wake the displays**. On this box that is bound to **Meta+Alt+L** (Windows+Alt+L) via a small helper (PowerDevil’s built-in “Turn Off Screen” is unbound because on X11 key-release immediately wakes DPMS — KDE #423035). Equivalent without our shortcut (run from an already-unlocked session): ```bash # 1) lock (greeter starts) qdbus org.freedesktop.ScreenSaver /ScreenSaver Lock # 2) blank outputs shortly after (race window) sleep 1 xset dpms force off # 3) wake with mouse or key # Expected on this machine within seconds to ~1 minute: # - lock greeter is alive (Howdy/fingerprint/password path may run) # - display shows a frozen / ghost frame (often last unlocked desktop) # - org.kde.KWin supportInformation / D-Bus times out # - kwin_x11 stuck as in the attached backtrace ``` Related variant that also led to the same ghost-lock phenotype: **DPMS- off only** (no lock), then wait for Plasma **Autolock** (here Timeout=10 minutes) so lock runs while outputs are already off. **Asks** 1. Please re-evaluate backporting the Mesa **26.1.5** `dri3: Increment draw->send_sbc after waiting for last presentation` fix (or current equivalent) to noble’s **25.2.x**. 2. Happy to capture `LIBGL_DEBUG` / present traces or retest a proposed package if useful. ** Attachment added: "kwin_x11 gdb thread apply all bt — loader_dri3_query_buffer_age hang 2026-08-03" https://bugs.launchpad.net/bugs/2161079/+attachment/5988814/+files/gdb-kwin_x11-dri3-query-buffer-age-20260803.txt -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2161079 Title: kwin_x11 and plasmashell hang forever in DRI3 glXSwapBuffers after HWE kernel 6.17 update (Meteor Lake, X11) — fix candidate in Mesa 26.1.5 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/mesa/+bug/2161079/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
