Public bug reported:
ince 2026-09-09, on a docked laptop with the lid closed and two external
monitors, the monitors frequently fail to turn back on after the lock
screen has blanked them (DPMS off). The session itself keeps running:
the lock screen accepts the password blindly, and switching VT away and
back (Ctrl+Alt+F3, then Ctrl+Alt+F2) immediately restores both monitors.
On 2026-10-15 alone this happened 6 times (10:37, 12:12, 14:26 twice,
14:32, 16:16), while at least one wake that day worked normally. A VT
switch fixed every one of them.
Setup
- Lenovo ThinkPad E590 (BIOS R0YET46W 1.29)
- Intel UHD Graphics 620 [8086:3ea0] (i915, drives the displays) + AMD Lexa PRO
[1002:699f] (amdgpu, render-only)
- Generic USB-C dock (VIA billboard 2109:0102, Realtek hubs, RTL8153 LAN);
monitors on DP-1 and HDMI-A-1, laptop lid closed, eDP-1 disabled
- Ubuntu 26.04.1 LTS, Wayland session
- mutter 50.1-0ubuntu2.4, gnome-shell 50.1-0ubuntu1.3, kernel 7.0.0-38-generic
- Kernel parameters: i915.enable_dc=0 i915.enable_psr=0
Steps to reproduce
1. Laptop docked, lid closed, two external monitors active.
2. Lock the session (Super+L) and wait until the monitors go into power save
(~30 s).
3. Press a key or move the mouse.
Expected: the monitors turn on and show the unlock prompt.
Actual: the monitors stay off. The lock screen is awake (fprintd is activated
and a blind password unlocks the session), but the screens stay dark.
Observations
- While the monitors stay dark, /sys/class/drm/card1-{DP-1,HDMI-A-1}/dpms
report "Off" and org.gnome.Mutter.DisplayConfig PowerSaveMode stays at 3.
Mutter never leaves power-save mode, even though the lock screen has woken up.
- Two variants are seen:
a) Silent: nothing is logged at all (both episodes in the morning of
2026-10-15).
b) Mutter logs bursts of "Cursor update failed: drmModeAtomicCommit: Invalid
argument" (hundreds to thousands of lines) after the wake attempt.
- At lock time, "Unexpected non-NULL onscreen_native->next_frame" is often
logged. However, this message has appeared almost daily since June 2026 without
consequences, and it is absent in some of the failed episodes.
- Workaround: a VT switch (chvt 3; chvt 2) always restores the displays. I
currently run a watchdog that does this automatically when the dpms state is
still Off 3 s after the lock-screen wake.
Regression window
- In the journal, "Cursor update failed" was rare up to 2026-09-08 (1-6 lines
per day, on 6 days in three months, with no user-visible problem). Starting on
2026-09-09 it comes in large bursts together with the dark-monitor problem.
- Packages updated on 2026-09-07/08, immediately before the onset:
- linux-image 7.0.0-30 -> 7.0.0-31 (first boot with it on 2026-09-08)
- gnome-shell 50.1-0ubuntu1.1 -> 50.1-0ubuntu1.2
- mesa 26.0.3-1ubuntu1 -> 26.0.8-1ubuntu0.3
- linux-firmware 20260319.git217ca6e4-0ubuntu1 -> -0ubuntu1.2
- I cannot bisect against the old kernel because 7.0.0-30 is no longer
installed.
Happy to provide full journal excerpts or test patches/PPAs.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: mutter (not installed)
ProcVersionSignature: Ubuntu 7.0.0-38.38-generic 7.0.14
Uname: Linux 7.0.0-38-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Thu Oct 15 16:22:03 2026
InstallationDate: Installed on 2022-10-12 (1464 days ago)
InstallationMedia: Ubuntu 22.04.1 LTS "Jammy Jellyfish" - Release amd64
(20220809.1)
ProcEnviron:
LANG=it_IT.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
SourcePackage: mutter
UpgradeStatus: Upgraded to resolute on 2026-05-20 (148 days ago)
modified.conffile..etc.default.apport: [modified]
mtime.conffile..etc.default.apport: 2026-10-09T09:25:02.652678
** Affects: mutter (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
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https://bugs.launchpad.net/bugs/2170995
Title:
External monitors on USB-C dock stay off after waking from lock screen
(regression since early September 2026)
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