Pi 4: V3D GPU hangs (V3D_ERR_STAT 0x00001000) with X11/glamor on 6.18.34, resolved by disabling glamor

[montgomeryb]

Describe the bug

On Raspberry Pi OS Trixie with kernel 6.18.34+rpt-rpi-v8, the desktop eventually freezes while connected through NoMachine.

SSH continues to work, but the X desktop becomes unusable and NoMachine can no longer reconnect.

The kernel repeatedly reports V3D GPU resets:

v3d: Resetting GPU for hang
V3D_ERR_STAT: 0x00001000

Disabling glamor acceleration appears to eliminate the problem.

To reproduce

Hardware:

• Raspberry Pi 4 (4GB)
• HDMI to VGA adapator connected
• Raspberry Pi OS Trixie 64-bit
• LightDM
• X11 (not Wayland)

Software:

• Kernel 6.18.34+rpt-rpi-v8
• NoMachine 9.8.2

Logs

Kernel:

v3d: Resetting GPU for hang.
V3D_ERR_STAT: 0x00001000

No other GPU errors are present before the failure.

Additional observations

The X server becomes unresponsive after the GPU hang.

From SSH:

DISPLAY=:0 XAUTHORITY=/var/run/lightdm/root/:0 xdpyinfo

blocks once the failure occurs.

Workaround

Creating:

/etc/X11/xorg.conf.d/20-modesetting-noaccel.conf

with:

Section "Device"
Identifier "Modesetting"
Driver "modesetting"
Option "AccelMethod" "none"
EndSection

results in:

() modeset(0): Option "AccelMethod" "none"
() modeset(0): glamor disabled

After disabling glamor:

• NoMachine remains usable.
• rtl_airband and TwoToneDetect continue running.
• No V3D errors occur.
• The system remained stable for at least 47 minutes (still testing).

This strongly suggests the issue is in the accelerated X11/V3D path rather than NoMachine itself.

Steps to reproduce the behaviour

Steps:

1. Boot normally.
2. Connect to the desktop using NoMachine.
3. Use the desktop normally (mostly terminal windows).
4. After roughly 10-20 minutes the desktop freezes.
5. SSH remains functional.
6. Kernel repeatedly reports V3D GPU reset messages.

Device (s)

Raspberry Pi 4 Mod. B

System

https://pastebin.com/BVBwgayG

Logs

sudo dmesg -T | grep -iE 'v3d|drm_sched|gpu_sched|job timedout|hung task' | tail -80
[Thu Jul 23 20:06:34 2026] v3d fec00000.v3d: [drm] Transparent Hugepage support is recommended for optimal performance on this platform!
[Thu Jul 23 20:06:34 2026] [drm] Initialized v3d 1.0.0 for fec00000.v3d on minor 0
[Thu Jul 23 20:18:37 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR Resetting GPU for hang.
[Thu Jul 23 20:18:37 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR V3D_ERR_STAT: 0x00001000
[Thu Jul 23 20:18:38 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR Resetting GPU for hang.
[Thu Jul 23 20:18:38 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR V3D_ERR_STAT: 0x00001000
[Thu Jul 23 20:18:39 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR Resetting GPU for hang.
[Thu Jul 23 20:18:39 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR V3D_ERR_STAT: 0x00001000
[Thu Jul 23 20:18:40 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR Resetting GPU for hang.
[Thu Jul 23 20:18:40 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR V3D_ERR_STAT: 0x00001000
[Thu Jul 23 20:18:40 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR Resetting GPU for hang.
[Thu Jul 23 20:18:40 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR V3D_ERR_STAT: 0x00001000
[Thu Jul 23 20:18:41 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR Resetting GPU for hang.
[Thu Jul 23 20:18:41 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR V3D_ERR_STAT: 0x00001000
[Thu Jul 23 20:18:41 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR Resetting GPU for hang.
[Thu Jul 23 20:18:41 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR V3D_ERR_STAT: 0x00001000
[Thu Jul 23 20:18:42 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR Resetting GPU for hang.
[Thu Jul 23 20:18:42 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR V3D_ERR_STAT: 0x00001000
[Thu Jul 23 20:18:43 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR Resetting GPU for hang.
[Thu Jul 23 20:18:43 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR V3D_ERR_STAT: 0x00001000
[Thu Jul 23 20:18:44 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR Resetting GPU for hang.
[Thu Jul 23 20:18:44 2026] v3d fec00000.v3d: [drm:v3d_reset [v3d]] ERROR V3D_ERR_STAT: 0x00001000

Additional context

No response