Public bug reported:
AFFECTS RELEASE:
Ubuntu 26.04 (Resolute)
---
DESCRIPTION:
gnome-shell crashes with signal 11 (SIGSEGV) on a dual-monitor Wayland session
when using a Mesa version that includes the LP #2152207 flicker fix (26.1.2).
The official Mesa 26.0.3 does NOT crash (but flickers). This appears to be the
separate Issue 2 described in LP #2152207 comment #23.
Daniel van Vugt asked affected users to open a new bug for crashes in comment
#29 of LP #2152207. This report provides reproducible timeline evidence linking
"Unexpected non-NULL onscreen_native->next_frame" warnings to subsequent
gnome-shell crashes.
---
HARDWARE:
- Machine: Lenovo ThinkPad T490 (20RYA014CD)
- GPU: Intel UHD Graphics (CometLake-U GT2, i915 driver)
- Monitors (dual, during all crashes):
* eDP-1: 1920x1080 @ ~60Hz (built-in, primary)
* HDMI-2: 2560x1440 @ ~60Hz (external)
- Input: Logitech G502 HERO Gaming Mouse (USB)
---
SOFTWARE:
- Ubuntu 26.04 LTS (Resolute)
- Kernel: 7.0.0-14-generic
- GNOME Shell: 50.1
- Mutter: 50.1-0ubuntu2.1 (official, unchanged)
- Mesa: 26.1.2~kisak1~r (from ppa:kisak/kisak-mesa, includes LP #2152207 fix)
- Session: Wayland (ubuntu.desktop)
- GRUB: quiet splash (no i915 overrides)
- /etc/environment: clean (no MUTTER_DEBUG_* variables)
Note: crashes occur with ANY Mesa version that fixes the flicker bug:
- vanvugt PPA 26.0.3-1ubuntu1.lp2152207.1 → crash every 1.5~3.5 hours
- canonical-x staging 26.0.8-1ubuntu0.1~ppa1 → crash within minutes
- kisak PPA 26.1.2~kisak1~r → crash after hours (this report)
Official Mesa 26.0.3-1ubuntu1 → no crashes, but flickering present.
---
SYMPTOMS:
- Desktop session logs out unexpectedly (gnome-shell SIGSEGV, auto re-login)
- NOT a full system reboot — only gnome-shell dies
- Zero flickering errors (lock_front_buffer / EGL 3003) with fixed Mesa
- Crash signature always:
GNOME Shell crashed with signal 11
== Stack trace for context ...
#0 ... resource:///org/gnome/shell/ui/init.js:20
---
KEY EVIDENCE: next_frame WARNING PRECEDES CRASHES
Two "Unexpected non-NULL onscreen_native->next_frame" warnings were logged
before crashes, matching the assessment in LP #2152207 comment #23
(Mutter dual-CRTC frame scheduling race in meta-onscreen-native.c).
Timeline (single boot session, 2026-06-04 09:21 → 2026-06-05 16:13):
2026-06-04 12:14:15 gnome-shell[4954]: Unexpected non-NULL
onscreen_native->next_frame
2026-06-05 11:15:47 gnome-shell[4954]: GNOME Shell crashed with signal 11
↑ same process, ~23 hours after warning
2026-06-05 11:30:10 gnome-shell[594714]: Unexpected non-NULL
onscreen_native->next_frame
2026-06-05 12:21:48 gnome-shell[594714]: GNOME Shell crashed with signal 11
↑ same process, ~51 minutes after warning
2026-06-05 16:13:31 gnome-shell[642035]: GNOME Shell crashed with signal 11
↑ no next_frame logged before this crash, but libinput
"your system is too slow" warnings at 16:12:53 (36ms
lag)
Crash frequency accelerates after first crash in a session:
1st crash: ~26 hours uptime
2nd crash: ~1 hour after re-login
3rd crash: ~4 hours after re-login
---
EXTRACTED JOURNAL LOGS:
$ journalctl -b | grep -E 'next_frame|signal 11'
Jun 04 12:14:15 gnome-shell[4954]: Unexpected non-NULL
onscreen_native->next_frame
Jun 05 11:15:47 gnome-shell[4954]: GNOME Shell crashed with signal 11
Jun 05 11:30:10 gnome-shell[594714]: Unexpected non-NULL
onscreen_native->next_frame
Jun 05 12:21:48 gnome-shell[594714]: GNOME Shell crashed with signal 11
Jun 05 16:13:31 gnome-shell[642035]: GNOME Shell crashed with signal 11
Immediately before 3rd crash:
Jun 05 16:12:53 gnome-shell[642035]: libinput error: event4 - Logitech G502
HERO
Gaming Mouse: client bug: event processing lagging behind by 36ms,
your system is too slow
Jun 05 16:13:31 gnome-shell[642035]: GNOME Shell crashed with signal 11
---
EXCLUDED CAUSES:
- NOT Mesa flicker bug (LP #2152207 Issue 1): zero lock_front_buffer / error
3003
- NOT GPU hang: no i915 hang/reset in kernel log at crash times
- NOT OOM: 37GB RAM, no oom-killer events
- NOT full system reboot: clean gnome-shell-only crash + GDM re-login
- NOT caused by MUTTER_DEBUG_* overrides: /etc/environment is clean
---
RELATED BUGS:
- LP #2152207 (Mesa flicker fix — separate issue, Fix Committed for Mesa)
- mutter upstream #4809 (closed Fix Released)
- LP #2152207 comment #23 (Issue 2 — gnome-shell SIGSEGV, ACTIVE unresolved)
- LP #2152207 comment #29 (Daniel: "open a new bug for crashes")
---
WORKAROUND:
Revert to official Mesa 26.0.3-1ubuntu1 → stable, no crashes, but flickering
returns on dual monitors.
Untested: X11 session + fixed Mesa may avoid this Wayland-native code
path.
---
REQUEST:
Please investigate the Mutter dual-CRTC onscreen_native->next_frame race on
Intel i915 + dual monitor (eDP + HDMI) Wayland setups when Mesa front-buffer
management is working correctly. A fix in Mutter (not Mesa) is needed so users
can receive the Mesa SRU flicker fix without session crashes.
I can provide full journal logs or apport crash files on request.
Related: https://bugs.launchpad.net/ubuntu/+source/mesa/+bug/2152207
(Issue 2 from comment #23 — separate crash bug as requested in comment #29)
** Affects: mutter (Ubuntu)
Importance: Undecided
Status: New
** Attachment added: "crash-log-extract.txt"
https://bugs.launchpad.net/bugs/2155628/+attachment/5975705/+files/crash-log-extract.txt
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https://bugs.launchpad.net/bugs/2155628
Title:
gnome-shell SIGSEGV on dual-monitor Wayland after Mesa flicker fix
(next_frame race)
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