Issue 1 — EGL buffer allocation failure (RESOLVED by Mesa fix)
Before Mesa fix, continuous errors every session:
Error 0x3003 reported by eglSwapBuffers
meta_onscreen_native_swap_buffers_with_damage failed. Frame aborted.
Failed to query buffer age, got error 3003
Failed to lock front buffer on /dev/dri/card1: gbm_surface_lock_front_buffer 
failed

- Escalated to ~300 errors/minute during active flickering
- Visual corruption at outer top-left and top-right corners of display, 
bleeding downward
- COGL_DISABLE_GL_EXTENSIONS=EXT_buffer_age,KHR_partial_update did NOT prevent 
eglSwapBuffers from 
  returning 0x3003
- Temporary workaround: toggling display scale (200%→166%→200%) forced pipeline 
reinit and cleared 
  errors — same behavior as IgorP's refresh rate toggle

After Mesa fix (26.0.3-1ubuntu1.lp2152207.1):

- Zero EGL errors in all sessions ✅
- No visual flickering ✅
- Mesa fix confirmed working for MST tiled display


Issue 2 — gnome-shell SIGSEGV crash (ACTIVE, unresolved)
gnome-shell crashes with signal 11 reproducibly every 1.5–3.5 hours after Mesa 
fix applied:

Session 1: ran 08:24:21 → crashed 09:52:34 (~1.5 hours)
Session 2: ran 10:02:08 → crashed 13:38:35 (~3.5 hours)
Zero EGL errors during both crashed sessions — Mesa fix holding throughout

Crash signature:

GNOME Shell crashed with signal 11
[email protected]: Main process exited, code=dumped, status=11/SEGV
__pthread_kill_implementation → SIGSEGV

Warning observed ~55 minutes before first crash (not seen before
second):

Unexpected non-NULL onscreen_native->next_frame

Assessment: Likely a race condition in Mutter's dual-CRTC frame scheduling — 
onscreen_native->next_frame is not properly serialized between Pipe A (DP-1) 
and Pipe B (DP-2) when both CRTCs complete frames simultaneously. 
Timing-dependent, hence variable 1.5–3.5 hour window before crash. This code 
path is in meta-onscreen-native.c, same file touched by MR 5075.
Cannot install libmutter-18-0-dbgsym — conflicts with PPA version. Please 
retrace server-side.

Attaching - logs.zip
_usr_bin_gnome-shell.1000.crash — apport crash report (please retrace 
server-side)
full-boot-log.txt.gz — complete journal from crashed session
gnome-shell-stacktrace.txt — gdb trace without symbols (symbols unavailable due 
to PPA version conflict)


** Attachment added: "Logs.zip"
   
https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/2152207/+attachment/5974393/+files/Logs.zip

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https://bugs.launchpad.net/bugs/2152207

Title:
  Failed to lock front buffer on /dev/dri/card1:
  gbm_surface_lock_front_buffer failed | Failed to query buffer age, got
  error 3003

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