Wayland: kwin_wayland 6.7 hangs (hung task / deadlock) after waking monitors from power-saving mode with hybrid AMD/NVIDIA (nvidia open driver)

NVIDIA Open GPU Kernel Modules Version

610.43.02

Please confirm this issue does not happen with the proprietary driver (of the same version). This issue tracker is only for bugs specific to the open kernel driver.

• I confirm that this does not happen with the proprietary driver package.

Operating System and Version

Arch Linux

Kernel Release

7.0.12-arch1-1 - 7.1.2-arch3-1 (64-bit)

Please confirm you are running a stable release kernel (e.g. not a -rc). We do not accept bug reports for unreleased kernels.

• I am running on a stable kernel release.

Hardware: GPU

AMD Radeon 780M Graphics [Integrated] / NVIDIA GeForce RTX 4060 Max-Q / Mobile [Discrete]

Describe the bug

SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 6.7.1 - 6.7.2
KDE Frameworks Version: 6.27.0
Qt Version: 6.11.1
Kernel Version: 7.0.12-arch1-1 - 7.1.2-arch3-1 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 9 7940HS w/ Radeon 780M Graphics
Memory: 32 ГиБ of RAM (30.6 GiB usable)
Graphics Processor 1: AMD Radeon 780M Graphics
Graphics Processor 2: NVIDIA GeForce RTX 4060 Laptop GPU
Manufacturer: ASUSTeK COMPUTER INC.
Product Name: Vivobook_ASUSLaptop M6500XV_M6500XV
System Version: 1.0
NVIDIA Open Driver: 610.43.02

DESCRIPTION
The issue appears to be a kernel deadlock inside the NVIDIA driver, where nvidia-modeset holds a semaphore indefinitely while looping in kernel space, causing kwin_wayland to hang in state:D.

After updating KDE Plasma to versions 6.7.1 and 6.7.2, a severe issue occurs in the Wayland session when monitors wake up from power-saving (DPMS) mode.

In this hybrid GPU setup, if the screens go into power-saving mode and I then wake them up, there is a very high probability that the graphical system will freeze within a few seconds, followed by a hung task / deadlock. The entire system becomes completely unresponsive, forcing a hard reset using the power button.

Additionally, I noticed that starting with KDE Plasma 6.7, the monitors take noticeably longer to wake up from power-saving mode and the process feels much less responsive than before.

OBSERVED RESULT
The graphical session freezes, followed shortly by a hung task / deadlock, requiring a hard reboot.

EXPECTED RESULT
The monitors should wake up quickly and responsively without causing any system instability, freezes, or hung task / deadlock.

hangs.log

To Reproduce

STEPS TO REPRODUCE

1. Connect an external monitor via HDMI (driven by the NVIDIA dGPU) while the laptop screen runs on the AMD iGPU.
2. Log into a KDE Plasma Wayland session.
3. Let the system put the monitors into power-saving mode (or trigger screen sleep automatically via energy saving settings).
4. Wake the monitors up by moving the mouse or pressing a key.
5. Wait a few seconds.

Bug Incidence

Sometimes

nvidia-bug-report.log.gz

ADDITIONAL INFO:
Downgrading to Plasma 6.6 resolves the issue completely,

Note: The nvidia-bug-report.log.gz was collected after the crash, right after rebooting the system.

nvidia-bug-report.log.gz

Related upstream issue: I have also opened a bug report on the KDE tracker to keep both development teams informed: https://bugs.kde.org/show_bug.cgi?id=522646

More Info

No response

Start by reviewing hangs.log and nvidia-bug-report.log.gz alongside the reproduction steps for the hybrid AMD/NVIDIA Wayland setup. Compare behavior between Plasma 6.6 and 6.7, and consult the linked KDE issue for cross-project context. Done means waking monitors from power-saving no longer causes the reported freeze, hung task, or deadlock.