Verification done for noble: xorg-server 2:21.1.12-1ubuntu1.9 from
noble-proposed fixes the crash.
Test system:
- HP Pavilion x360 14-dh1xxx (Intel CometLake-U UHD, modesetting), Secure Boot
enabled
- Ubuntu Cinnamon 24.04.5 live session (X11, real Xorg via LightDM), kernel
7.0.0-31-generic (HWE)
- DisplayLink USB3.0 UHD DisplayPort Adapter (17e9:4301) with a monitor attached
- displaylink-driver 6.4.0-22, with the kernel's own evdi module from
linux-modules-evdi-7.0.0-31-generic 7.0.0-31.31~24.04.1
- evdi initial_device_count=0 (the module default), so DisplayLinkManager
creates the evdi device after X is running
Steps, run identically on each version (the same as the resolute verification):
1. Stop lightdm and displaylink-driver, reload evdi so no evdi device exists.
2. Start lightdm (X comes up with no evdi GPU), then start displaylink-driver.
Xorg.0.log shows the runtime add: "config/udev: Adding drm device
(/dev/dri/card0)", "modeset(G0): using drv /dev/dri/card0".
3. Restart lightdm, which tears the X server down with the hotplugged GPU
screen still present.
Before, 2:21.1.12-1ubuntu1.8 (noble-updates): the teardown crashes:
(EE) Segmentation fault at address 0x0
(EE) Caught signal 11 (Segmentation fault). Server aborting
(EE) Server terminated with error (1). Closing log file.
and systemd-coredump records an Xorg core (SIGABRT from the signal
handler).
After, 2:21.1.12-1ubuntu1.9 (noble-proposed): same steps, run twice.
Each time the runtime add appears in the log, the GPU screen is torn
down ("UnloadModule: modesetting") and the server exits cleanly ("Server
terminated successfully (0)"), with no core dumps. The DisplayLink
monitor is active under 1.9 (DVI-I-1-1 at 1280x1440 in xrandr).
Separately, my daily driver (an HP ZBook on noble with a DisplayLink
adapter on a Thunderbolt dock) has run the same fix, as a PPA build of
1.9, since July 2026, with no Xorg crashes since.
As with resolute, the udev NULL-subsystem fix is a teardown race that
can't be triggered on demand; it did not fire in these runs.
Changing the tag to verification-done-noble.
** Tags removed: verification-needed-noble
** Tags added: verification-done-noble
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https://bugs.launchpad.net/bugs/2160643
Title:
xorg-server SIGSEGV on runtime GPU-screen (DisplayLink/evdi) hotplug
-- NULL SetDGAMode and NULL udev subsystem
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