Unresponsive GUI and journal flooded with: JS ERROR: TypeError: null has no properties _onFocusChanged@resource:///org/gnome/shell/ui/closeDialog.js:135:9

It appears the problem is:

[123981.625765] bs1-ThinkPad-T410 gnome-shell[2226]: JS ERROR: TypeError: null has no properties
                                                    _onFocusChanged@resource:///org/gnome/shell/ui/closeDialog.js:135:9
[123981.625875] bs1-ThinkPad-T410 gnome-shell[2226]: JS ERROR: TypeError: null has no properties
                                                    _onFocusChanged@resource:///org/gnome/shell/ui/closeDialog.js:135:9
[123981.625998] bs1-ThinkPad-T410 gnome-shell[2226]: JS ERROR: TypeError: null has no properties
                                                    _onFocusChanged@resource:///org/gnome/shell/ui/closeDialog.js:135:9

Confirmed by upstream bug:

https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2467

Please push out a fix for this ASAP, once this tight loop is hit the machine becomes an unusable 100% CPU using mess. I know of several others suffering exactly the same bug.

For me this can be reproduced by having a terminal using half the screen (using CMD+LEFT), then switching to fullscreen (F11) and back (F11). Repeating this some number of times triggers this tight loop of 100% CPU usage. After that, it's difficult to get window focus and windows are slow to respond to anything.

To recover I use `killall -3 gnome-shell`, which allows Gnome to restart but then has the delightful affect of throwing windows around the screen randomly and forgetting there are multiple monitors.

There is no fix for this bug yet. If you would like to discuss it then please do so with the developers at:

  https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2467

The

killall -3 gnome-shell

Does help recover more gracefully than a hard boot after 100% cpu. Thanks danbarry16!

^^^
Note the above command is only safe in Xorg sessions, NOT in Wayland sessions.

thanks Dan `killall -3 gnome-shell` keeps me sane. No longer need to reboot everyday.

I hope this helps: I see these errors in my syslog:

Nov 4 10:43:32 parse2 gnome-shell[4026701]: JS ERROR: TypeError: windowActor is null#012_addWindowEffect@resource:///org/gnome/shell/ui/closeDialog.js:90:28#012vfunc_show@resource:///org/gnome/shell/ui/closeDialog.js:162:14

Nov 4 11:17:38 parse2 gnome-shell[4026701]: message repeated 34072 times: [ JS ERROR: TypeError: null has no properties#012_onFocusChanged@resource:///org/gnome/shell/ui/closeDialog.js:135:9]

Nov 4 10:51:50 parse2 gnome-shell[11582]: [11584:11584:1104/105150.374036:ERROR:CONSOLE(1)] "[Shields]: Can't request shields panel data. Error: No tab url specified", source: chrome-extension://mnojpmjdmbbfme
jpflffifhffcmidifd/out/brave_extension_background.bundle.js (1)

Yet More Info:
While it was running slow, I did a gcore, and it showed a single active thread (90% CPU) in the garbage collector. That may have nothing to do with this, but who knows...

gnome-shell: 3.36.4
Ubuntu 20.04
Hardware: 64g memory, 1Tb NVME drive, Asus ROG Strix GeForce RTX 2060, 4 Monitors
          Cores: 16 Threads: 32 AMD Ryzen 3950X
browser1 = brave tabs = 67
browser2 = firefox tabs= 64
various other windows Quake, rocketchat, Thunderbird, MATE terminal

Similar ERROR in /var/log/syslog for me on Ubuntu 20.10 with gnome-shell 3.38.1-1ubuntu1.1. Similar to comment #9 I have firefox with many tabs and dissenter (brave fork) with many tabs open.

Jan 4 06:43:29 desktop01 gnome-shell[2096000]: JS ERROR: TypeError: null has no properties#012_onFocusChanged@resource:///org/gnome/shell/ui/closeDialog.js:135:9

Jan 4 06:43:30 desktop01 gnome-shell[2096000]: message repeated 35862 times: [ JS ERROR: TypeError: null has no properties#012_onFocusChanged@resource:///org/gnome/shell/ui/closeDialog.js:135:9]

Jan 4 06:43:30 desktop01 gnome-shell[2096000]: JS ERROR: TypeError: windowActor is null#012_addWindowEffect@resource:///org/gnome/shell/ui/closeDialog.js:90:28#012vfunc_show@resource:///org/gnome/shell/ui/closeDialog.js:162:14

➜ ~ inxi -SMCG
System: Host: desktop01 Kernel: 5.8.0-33-generic x86_64 bits: 64 Desktop: N/A Distro: Ubuntu 20.10 (Groovy Gorilla)
Machine: Type: Desktop System: ASUS product: All Series v: N/A serial: <superuser/root required>
           Mobo: ASUSTeK model: X99-A v: Rev 1.xx serial: <superuser/root required> UEFI: American Megatrends v: 4101
           date: 07/10/2019
CPU: Info: 6-Core model: Intel Core i7-5820K bits: 64 type: MT MCP L2 cache: 15.0 MiB
           Speed: 1765 MHz min/max: 1200/3600 MHz Core speeds (MHz): 1: 1626 2: 1243 3: 1387 4: 1291 5: 1379 6: 1316 7: 1329
           8: 1300 9: 1288 10: 1247 11: 1356 12: 1282
Graphics: Device-1: NVIDIA GK208B [GeForce GT 710] driver: nvidia v: 455.38
           Display: x11 server: X.Org 1.20.9 driver: nvidia unloaded: fbdev,modesetting,nouveau,vesa resolution:
           1: 2560x1080~60Hz 2: 1680x1050~60Hz
           OpenGL: renderer: GeForce GT 710/PCIe/SSE2 v: 4.6.0 NVIDIA 455.38

A potential fix has been proposed upstream:

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1676

Hello! Please update the description to include the necessary SRU information [1]. Thank you!

[1] https://wiki.ubuntu.com/StableReleaseUpdates#SRU_Bug_Template

This bug was fixed in the package mutter - 3.38.3-2ubuntu1

---------------
mutter (3.38.3-2ubuntu1) hirsute; urgency=medium

  * Merge with debian, containing new upstream release (LP: #1915025)
    - Disable CRTCs when system becomes headless (LP: #1905825)
    - Fixed crash during windows unmanagement (LP: #1870822)
    - Do not handle ungrabbed events when unmanaging (LP: #1880405)
    - Downgrade assert to warning when adding window (LP: #1911921)
  * d/p/x11-Add-support-for-fractional-scaling-using-Randr.patch:
    - Refreshed
  * debian/rules: Enable remote desktop for all linux builds (LP: #1730612)

mutter (3.38.3-2) unstable; urgency=medium

  * Team upload
  * d/patches: Update to commit 3.38.3-12-g2d424a739 from gnome-3-38 branch
    - Cope with monitors with metacharacters in their EDID data
    - Don't crash if parsing monitor configuration fails
    - Don't crash if an extension tries to add the same window to a
      workspace more than once, such as auto-move-windows
    - Cope with monitor configuration changes during screencasting
    - Speed up workspace switching when many windows are open
    - Fix Xwayland windows not always appearing in the gnome-shell overview
    - Avoid warning spam and poor performance when unmanaging a window
      (probably Closes: #970295, LP: #1841774)

mutter (3.38.3-1) unstable; urgency=medium

  * Team upload
  * d/watch: Only watch for 3.38.x versions
  * New upstream release

 -- Marco Trevisan (Treviño) <email address hidden> Tue, 09 Feb 2021 04:59:11 +0100

Is the fix available in 20.04 LTS, or just 20.10 only?

Only in 21.04 at the moment.

The fix is coming in the future mutter 3.36.9 update.

Would be very nice if it will be available in 20.04 ubuntu. Very annoying issue :(

3.36.9-0ubuntu0.20.04.1 is still in proposed, so not yet released.

Monitor https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/1919143 to also mark this as released.