https://bugs.kde.org/show_bug.cgi?id=527839
Bug ID: 527839
Summary: KWin 6.8.1 Wayland crash & display freezes.
Classification: Plasma
Product: kwin
Version First 6.8.1
Reported In:
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: wayland-generic
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
## DESCRIPTION
Disclaimer:
GPT was used to help identify the possible culprit, as with it's suggested
temporary fix, the core problem has since not occurred. So GPT was used to help
formulate a proper bug report below.
KWin 6.8.1 intermittently freezes or crashes during normal desktop usage on KDE
Plasma Wayland with an NVIDIA Blackwell GPU.
Sometimes the primary DisplayPort monitor freezes while the secondary HDMI
monitor remains responsive. Other times both displays freeze, occasionally
requiring a hard reset.
On October 26, 2026, activating the primary monitor coincided with a confirmed
KWin segmentation fault (`SIGSEGV`). Firefox and multiple KDE applications
subsequently lost their Wayland compositor connections.
The crash occurred inside
`KWin::SurfaceInterface::requestedTimingOfNextCommit()`, suggesting a possible
problem involving Wayland commit timing or frame presentation.
The freezes occurred with both NVIDIA driver 615.78.08 and 610.57.04.
After disabling KWin's Wayland commit-timing support using
`KWIN_WAYLAND_SUPPORT_COMMIT_TIMING_V1=0`, no further freezes have been
observed during approximately one night of testing.
This is a preliminary observation rather than a confirmed permanent fix.
## STEPS TO REPRODUCE
1. Run KDE Plasma 6.8.1 on Wayland with an NVIDIA Blackwell GPU and a
dual-monitor setup, including a high-refresh-rate DisplayPort monitor.
2. Use the desktop normally with multiple applications open, including Firefox,
or other graphical programs. One program that instantly triggered it was one
that uses pyqt6, and situation returned immediately. Turn the primary
DisplayPort monitor off and back on, causing a display activation or
reconfiguration.
3. Intermittently, KWin crashes or the display freezes. The problem is not
reproducible on every monitor power cycle.
## OBSERVED RESULT
KWin intermittently freezes or crashes. In some cases, a hard reset is
required.
A confirmed crash occurred on October 26, 2026, at approximately 04:16 CET:
```text
Process: kwin_wayland
PID: 1696
Signal: SIGSEGV (11)
#0 KWin::SurfaceInterface::requestedTimingOfNextCommit()
(libkwin.so.6 + 0x71c894)
#1 KWin::SurfaceItemWayland::handleFramePainted(...)
(libkwin.so.6 + 0x41b8a3)
#2 KWin::Item::framePainted(...)
(libkwin.so.6 + 0x3f508c)
#3 KWin::WorkspaceScene::frame(...)
(libkwin.so.6 + 0x41d413)
#4 KWin::Compositor::composite(...)
(libkwin.so.6 + 0x1b25fc)
```
Immediately afterward, multiple applications reported losing their Wayland
compositor connections, and DisplayPort monitor's image freezes/ Second monitor
remains responsive, and moving a window over to the main monitor does not
change the image. The monitor will return to normal state after roughly 10-15
seconds, but will crash again after a minute or so.
Firefox generated a crash minidump and exited. The kernel also logged repeated
`NVRM: VM: invalid mmap context` messages after the compositor crash.
## EXPECTED RESULT
KWin should remain responsive during normal desktop usage, Wayland frame
presentation, and monitor power transitions.
Turning a monitor off or on should not crash the compositor, freeze displays,
or cause applications to terminate.
## SOFTWARE/OS VERSIONS
Operating System: CachyOS Linux
KDE Plasma Version: 6.8.1
KDE Frameworks Version: 6.31.0
Qt Version: 6.12.0
KWin Version: 6.8.1-1.1
Kernel Version: 6.18.55-2-cachyos-lts (64-bit)
Graphics Platform: Wayland
Processors: AMD Ryzen 9 5900X 12-Core Processor
Memory: 64 GiB RAM (62.7 GiB usable)
Graphics Processor: NVIDIA GeForce RTX 5090 (Blackwell architecture)
NVIDIA Drivers Tested: 615.78.08 and 610.57.04 (open kernel modules)
Kernels Tested:
- 7.3.0-3-cachyos with NVIDIA 615.78.08
- 6.18.55-2-cachyos-lts with NVIDIA 610.57.04
## ADDITIONAL INFORMATION
**Monitor configuration**
Primary monitor: LG 34GN850-B
- DisplayPort (DP-2)
- 3440×1440 at 160 Hz
- VRR disabled
- HDR disabled
- Scaling 100%
Secondary monitor: LF27T850
- HDMI (HDMI-A-1)
- 2560×1440 at 71.99 Hz
**Troubleshooting performed**
Initially, the freezes occurred with NVIDIA driver 615.78.08 on CachyOS kernel
7.3.
I downgraded NVIDIA to 610.57.04 and switched to kernel 6.18.55 LTS because the
older driver was incompatible with kernel 7.3.
The freezing persisted under the older driver and LTS kernel. The recorded KWin
segmentation fault occurred with NVIDIA 610.57.04.
**Workaround**
Created the following configuration file:
`~/.config/environment.d/kwin-commit-timing.conf`
With the contents:
```ini
KWIN_WAYLAND_SUPPORT_COMMIT_TIMING_V1=0
```
After restarting the desktop session with this setting, the system remained
stable for approximately one night without further observed freezes or
compositor crashes.
The backtrace's fault location and the improvement after disabling commit
timing suggest that KWin's Wayland commit-timing handling may be involved.
Possible causes include a surface lifetime issue, incorrect frame-timing state
handling, or an interaction between KWin, the NVIDIA driver, and display
reconfiguration.
The exact root cause has not been determined, and longer-term testing is
ongoing.
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