Dear Maintainer,


GPU: GRID Nvidia RTX8000-8Q (VGPU) - driver ver. 470.82.01
Remote access via: VNC CLient -> TigerVNC -> VirtualGL -> Cinnamon Session

virtualgl ver. 3.1-20230315 (A toolkit for displaying OpenGL applications
to thin clients)

Cinnamon session is started via:  vglrun -c proxy -d /dev/dri/card1 +sync
+wm cinnamon-session-cinnamon

Everything works fine, until you try to unmaximize any window, then the
cinnamon crashes.
When I replace the cinnamon with gnome-shell then there is no such problem.

Hi Tomek,

Sorry for the very long delay. Could you still reproduce this on a
supported release? Bullseye, where you saw it, reaches the end of its LTS
support on 2026-08-31; trixie ships cinnamon 6.4.10 and unstable 6.6.9.

For the record, the crash is not in glib: XShmGetImage() fails with an X
error and GDK turns X errors into fatal ones, so glib just aborts. That
code path is the "texture from pixmap" fallback used when
GLX_EXT_texture_from_pixmap is unavailable, which is your VirtualGL case
— muffin logs "NOTE: Not using GLX TFP!" when it happens — and the X
calls there are not wrapped in an error trap, so a pixmap invalidated by
the resize is enough to kill the session. The code is unchanged in
current versions, so the problem may well still be there; it lives in
cogl, which since Cinnamon 5.x is bundled inside muffin, and the bug
would then be reassigned there.

If you can still reproduce it, please say which release and versions, and
whether the "NOTE: Not using GLX TFP!" warning appears in the log.