https://bugs.kde.org/show_bug.cgi?id=519827
Bug ID: 519827
Summary: Screen frozen/blank after suspend+resume with two
active Wayland sessions when second user switches out.
Classification: Plasma
Product: kwin
Version First 6.6.4
Reported In:
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: wayland-generic
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
SUMMARY
This may be a regression or incomplete fix from bug #512511 ("Screen freeze
when screen dims or entering/exiting fullscreen"), which was resolved in Plasma
6.5.80. The same "Atomic modeset test failed! Permission denied" / "atomic
commit failed: Permission denied" errors appear in the logs, but the trigger is
different: a suspend/resume cycle combined with fast user switching between two
concurrent KDE Plasma/Wayland sessions.
STEPS TO REPRODUCE
1. Log in as user1. Start a KDE Plasma/Wayland session.
2. Use "Switch User" to start a second KDE Plasma/Wayland session as
user2 (both sessions are now active simultaneously).
3. From user2's session, suspend the system (sleep).
4. Resume from suspend. user2's session becomes the active session
on wake (as it was the active session before sleep).
5. Log out of user2's session (or switch back to user1).
OBSERVED RESULT
The display becomes completely frozen/blank after user2's session
closes and SDDM jumps to VT 1. The system is not actually hung:
user1's session continues to run normally in the background
(applications remain active, audio plays), but nothing is rendered
to the screen. The frozen state persists indefinitely.
When the user eventually triggers a logout from user1's session
(e.g. via keyboard shortcut), the sddm-helper crashes (exit code 1)
when attempting to start a new startplasma-wayland session, and SDDM
shuts down entirely, forcing a full system shutdown.
Key log entries (from journalctl, usernames anonymised):
# On resume - user1's background kwin immediately fails:
kwin_wayland[4009]: Atomic modeset test failed! Permission denied
# user2's session closes cleanly; SDDM hands back to VT 1:
sddm[3726]: Jumping to VT 1
# ~19 minutes later - user1 triggers logout; sddm-helper crashes:
sddm[3726]: Auth: sddm-helper (...startplasma-wayland --user user1)
crashed (exit code 1)
# user1's kwin confirms it never recovered DRM master:
kwin_wayland[4009]: atomic commit failed: Permission denied
Full annotated logs are attached (system-journal.log).
EXPECTED RESULT
After user2 logs out, DRM master should be transferred back to user1's
existing kwin_wayland compositor (via logind seat management), and
user1's desktop should be rendered normally on screen. If the existing
session cannot be resumed, SDDM should at minimum present its login
screen and be able to start a new session without crashing.
SOFTWARE/OS VERSIONS
Operating System: Garuda Linux
KDE Plasma Version: 6.6.4
KDE Frameworks Version: 6.25.0
Qt Version: 6.11.0
Kernel Version: 6.19.11-zen1-1-zen (64-bit)
Graphics Platform: Wayland
Processors: 32 × AMD RYZEN AI MAX+ 395 w/ Radeon 8060S
Memory: 128 GiB of RAM (125.1 GiB usable)
Graphics Processor: Radeon 8060S Graphics
ADDITIONAL INFORMATION
Hardware:
Machine: Framework Desktop (AMD Ryzen AI Max 300 Series)
FRANMFCP06 / BIOS 03.02 (07/22/2025)
CPU: AMD RYZEN AI MAX+ 395 w/ Radeon 8060S
(family: 0x1a, model: 0x70, stepping: 0x0, 32 threads)
GPU: AMD Radeon 8060S (amdgpu, gfx_v11_0 / DCN 3.5.1)
VRAM: 512M LPDDR5 256-bit (unified memory)
RAM: 128 GiB
Software:
Distribution: Garuda Linux (rolling, based on Arch Linux)
Kernel: 6.19.11-zen1-1-zen (linux-zen)
KWin: 6.6.4-1
SDDM: 0.21.0-6
Plasma Desktop: 6.6.4-1
Plasma Workspace: 6.6.4-1
Qt6 (Wayland): 6.11.0-1
Qt6 (base): 6.11.0-2
Session type: Wayland (startplasma-wayland)
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