Bug 505762

Summary: Error "kwin_wayland_drm: Atomic test failed! Permission denied" with 6.16-rc1
Product: [Plasma] kwin Reporter: Kyle Devir <kyle.devir>
Component: platform-drmAssignee: KWin default assignee <kwin-bugs-null>
Status: RESOLVED UPSTREAM    
Severity: normal CC: kyle.devir, xaver.hugl
Priority: NOR    
Version First Reported In: git master   
Target Milestone: ---   
Platform: Compiled Sources   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: journalctl entries from soft-frozen boot
6.16-rc1 config for testing

Description Kyle Devir 2025-06-19 06:54:31 UTC 
SUMMARY
Starting with Linux kernel version 6.16-rc1, I have started seeing kwin_wayland soft-freeze with "kwin_wayland_drm: Atomic test failed! Permission denied" errors in journalctl. Switching to tty doesn't work ~ but REISUB does, upon which I can restart the compositor. 

The freezing appears to happen upon turning off the screen and turning it back on ~ along with other apparently random moments during normal system usage when kwin_wayland tries to make such a test and just can't keep going, so it locks up entirely.

STEPS TO REPRODUCE
1. Install Linux 6.16-rc1
2. Start kwin_wayland
3. Turn off screen, turn on screen, maybe perfect atomic test somehow?
4. Profit? Not sure whether this is the only cause.

OBSERVED RESULT
Compositor soft-freeze with no restart or crash

EXPECTED RESULT
Functioning normally?

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 6.4.80
KDE Frameworks Version: 6.16.0
Qt Version: 6.9.1
Kernel Version: 6.16.0-rc1-1-custom-bcachefs-git-00060-ge1bce19af73a (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 7800X3D 8-Core Processor
Memory: 32 GiB of RAM (30.4 GiB usable)
Graphics Processor 1: AMD Radeon RX 7900 XTX
Graphics Processor 2: AMD Radeon Graphics
Manufacturer: ASRock
Product Name: X670E Pro RS
Comment 1 Kyle Devir 2025-06-19 06:55:13 UTC 
Created attachment 182375 [details]
journalctl entries from soft-frozen boot
Comment 2 Kyle Devir 2025-06-19 06:57:35 UTC 
Also comes in the "kwin_wayland_drm: Atomic test failed! Invalid argument" flavour too, apparently.

Common underlying issue too, probably.
Comment 3 Kyle Devir 2025-06-19 06:58:30 UTC 
Created attachment 182376 [details]
6.16-rc1 config for testing
Comment 4 Kyle Devir 2025-06-19 12:19:13 UTC 
Appears fixed with 6.16-rc2.

Not kwin_wayland's bug, apparently.