Bug 1222174 - Switching to text console causes KDE6/X11 plasmashell high CPU usage
Summary: Switching to text console causes KDE6/X11 plasmashell high CPU usage
Status: NEW
Alias: None
Product: openSUSE Tumbleweed
Classification: openSUSE
Component: KDE Workspace (Plasma) (show other bugs)
Version: Current
Hardware: x86-64 openSUSE Tumbleweed
: P5 - None : Normal (vote)
Target Milestone: ---
Assignee: E-Mail List
QA Contact: E-mail List
URL:
Whiteboard:
Keywords:
Depends on:
Blocks:
 
Reported: 2024-03-29 20:59 UTC by Michael Hamilton
Modified: 2024-04-21 22:29 UTC (History)
4 users (show)

See Also:
Found By: ---
Services Priority:
Business Priority:
Blocker: ---
Marketing QA Status: ---
IT Deployment: ---
fabian: needinfo? (michael)


Attachments
perf report (7.70 MB, text/plain)
2024-04-21 22:16 UTC, Kevin Coonan
Details

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Description Michael Hamilton 2024-03-29 20:59:15 UTC
When I switch to a text console (ctrl-alt-F1) and run an htop, I can see plasmashell periodically consuming 100% of a CPU.  

Plasmashell CPU stays at 100% for about 10 seconds then drops to normal for a few seconds then resumes at 100% for another 10 seconds.

This is with TW 20240328, but it was happening on previous versions too.

I'm using X11, KDE6, Nvidia 550.54.
Comment 1 Fabian Vogt 2024-03-29 21:04:24 UTC
Can you collect a backtrace (or multiple) of plasmashell while this happens?
Or even better, use "perf record -e cpu-cycles --call-graph -p $(pidof plasmashell)" for a few secons and then "perf report" to view the most called functions.
Comment 2 Michael Hamilton 2024-03-29 22:18:19 UTC
Had to change/correct the command syntax a bit:

perf record -p $(pidof plasmashell) -e cpu-cycles --call-graph fp
perf report > perf.report
head -200 perf.report
-----------------
# Total Lost Samples: 0
#
# Samples: 316K of event 'cpu-cycles'
# Event count (approx.): 351806076106
#
# Children      Self  Command          Shared Object                                   Symbol                                                                                                                                                                                                                
# ........  ........  ...............  ..............................................  ......................................................................................................................................................................................................................
#
    36.49%     0.84%  QSGRenderThread  libc.so.6                                       [.] clock_gettime@@GLIBC_2.17
            |          
             --35.64%--clock_gettime@@GLIBC_2.17
                       |          
                        --35.64%--__vdso_clock_gettime

    36.04%    36.02%  QSGRenderThread  [vdso]                                          [.] __vdso_clock_gettime
    13.65%     0.00%  QSGRenderThread  [unknown]                                       [.] 0x0000440404400080
            |
            ---0x440404400080
               |          
               |--1.74%--0x7f9e18dff4a4
               |          
               |--1.65%--0x7f9e18dff4c5
               |          
               |--1.64%--0x7f9e18ee3ea5
               |          
                --0.83%--0x7f9e1b080a60

    10.02%     0.00%  QSGRenderThread  [unknown]                                       [.] 0x00000000beee0100
            |
            ---0xbeee0100
               |          
               |--2.50%--0x7f9e1b0800b7
               |          
               |--2.48%--0x557447ab2b90
               |          
                --0.85%--__GI___pthread_self

     9.96%     0.00%  QSGRenderThread  [unknown]                                       [k] 0x0000441f0fc301f0
            |
            ---0x441f0fc301f0
               |          
               |--3.73%--__GI___pthread_mutex_unlock_usercnt
               |          
               |--0.83%--__pthread_equal
               |          
                --0.82%--__GI___pthread_self

     9.68%     9.67%  QSGRenderThread  libc.so.6                                       [.] __printf_buffer
            |          
            |--8.43%--__printf_buffer
            |          
             --1.26%--0xfff760e400000038
                       __printf_buffer

     5.37%     0.00%  QSGRenderThread  [unknown]                                       [.] 0x00000000306d5f6c
            |
            ---0x306d5f6c
               |          
                --5.37%--pthread_mutex_lock@@GLIBC_2.2.5

     5.37%     5.36%  QSGRenderThread  libc.so.6                                       [.] pthread_mutex_lock@@GLIBC_2.2.5
            |          
             --5.36%--0x306d5f6c
                       pthread_mutex_lock@@GLIBC_2.2.5

     3.74%     3.73%  QSGRenderThread  libc.so.6                                       [.] __GI___pthread_mutex_unlock_usercnt
            |          
             --3.73%--0x441f0fc301f0
                       __GI___pthread_mutex_unlock_usercnt

     2.51%     2.51%  QSGRenderThread  libc.so.6                                       [.] __strchrnul_avx2
            |
            ---__strchrnul_avx2

     2.50%     0.00%  QSGRenderThread  libGLX_nvidia.so.550.54.14                      [.] 0x00007f9e1b0800b7
            |
            ---0x7f9e1b0800b7

     2.49%     2.49%  QSGRenderThread  libGLX_nvidia.so.550.54.14                      [.] 0x00000000000530b7
            |          
             --2.49%--0xbeee0100
                       0x7f9e1b0800b7

     2.48%     0.00%  QSGRenderThread  [unknown]                                       [.] 0x0000557447ab2b90
            |
            ---0x557447ab2b90

     2.09%     2.09%  QSGRenderThread  libc.so.6                                       [.] ___vsnprintf
            |
            ---___vsnprintf

     1.74%     0.00%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00007f9e18dff4a4
            |
            ---0x7f9e18dff4a4

     1.74%     1.74%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00000000009ff4a4
            |
            ---0x440404400080
               0x7f9e18dff4a4

     1.67%     1.67%  QSGRenderThread  libc.so.6                                       [.] __GI___pthread_self
            |          
            |--0.85%--0xbeee0100
            |          __GI___pthread_self
            |          
             --0.82%--0x441f0fc301f0
                       __GI___pthread_self

     1.66%     0.00%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00007f9e18dff401
            |
            ---0x7f9e18dff401

     1.66%     1.66%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00000000009ff401
     1.66%     0.00%  QSGRenderThread  [unknown]                                       [.] 0xfff760e400000038
            |
            ---0xfff760e400000038
               |          
                --1.26%--__printf_buffer

     1.65%     0.00%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00007f9e18dff4c5
            |
            ---0x7f9e18dff4c5

     1.65%     1.65%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00000000009ff4c5
            |
            ---0x440404400080
               0x7f9e18dff4c5

     1.64%     1.64%  QSGRenderThread  libc.so.6                                       [.] __printf_buffer_write
            |          
             --1.24%--__printf_buffer_write

     1.64%     0.00%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00007f9e18ee3ea5
            |
            ---0x7f9e18ee3ea5

     1.63%     1.63%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x0000000000ae3ea5
            |
            ---0x440404400080
               0x7f9e18ee3ea5

     0.85%     0.85%  QSGRenderThread  libc.so.6                                       [.] __printf_buffer_done
            |
            ---__printf_buffer_done

     0.84%     0.84%  QSGRenderThread  libc.so.6                                       [.] __memmove_avx_unaligned_erms
            |          
             --0.83%--__memmove_avx_unaligned_erms

     0.84%     0.83%  QSGRenderThread  libc.so.6                                       [.] __pthread_equal
            |          
             --0.83%--0x441f0fc301f0
                       __pthread_equal

     0.83%     0.00%  QSGRenderThread  libGLX_nvidia.so.550.54.14                      [.] 0x00007f9e1b080a60
            |
            ---0x7f9e1b080a60

     0.83%     0.83%  QSGRenderThread  libGLX_nvidia.so.550.54.14                      [.] 0x0000000000053a60
            |
            ---0x440404400080
               0x7f9e1b080a60

     0.82%     0.82%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00000000009e8680
     0.82%     0.00%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00007f9e18de8680
            |
            ---0x7f9e18de8680

     0.81%     0.00%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00007f9e18de8684
            |
            ---0x7f9e18de8684

     0.81%     0.81%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00000000009e8684
     0.80%     0.00%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00007f9e18de8691
            |
            ---0x7f9e18de8691

     0.80%     0.80%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00000000009e8691
     0.48%     0.00%  QSGRenderThread  [kernel.kallsyms]                               [k] entry_SYSCALL_64_after_hwframe
     0.48%     0.00%  QSGRenderThread  [kernel.kallsyms]                               [k] do_syscall_64
     0.46%     0.00%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00007f9e18dff4a0
     0.46%     0.46%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00000000009ff4a0
     0.45%     0.00%  QSGRenderThread  libc.so.6                                       [.] __GI___ioctl
     0.45%     0.00%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00007f9e18ee3e66
     0.45%     0.45%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x0000000000ae3e66
     0.44%     0.00%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00007f9e18de86be
     0.44%     0.00%  QSGRenderThread  libGLX_nvidia.so.550.54.14                      [.] 0x00007f9e1b080abc
     0.44%     0.44%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00000000009ff3e6
     0.44%     0.00%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00007f9e18dff3e6
     0.44%     0.44%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00000000009e86be
     0.44%     0.44%  QSGRenderThread  libGLX_nvidia.so.550.54.14                      [.] 0x0000000000053abc
     0.44%     0.00%  QSGRenderThread  [kernel.kallsyms]                               [k] __x64_sys_ioctl
     0.44%     0.00%  QSGRenderThread  [kernel.kallsyms]                               [k] nvidia_unlocked_ioctl
     0.44%     0.00%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x00007f9e18ee3ea8
     0.44%     0.44%  QSGRenderThread  libnvidia-glcore.so.550.54.14                   [.] 0x0000000000ae3ea8
     0.44%     0.44%  QSGRenderThread  libGLX_nvidia.so.550.54.14                      [.] 0x0000000000053ae9
     0.44%     0.00%  QSGRenderThread  libGLX_nvidia.so.550.54.14                      [.] 0x00007f9e1b080ae9
-------------
Comment 3 Michael Hamilton 2024-04-18 04:48:31 UTC
I think this has something to do with my user login.  I tried another user login and it did not behave in this manner.  It's probable than some pre-KDE6 config or setting in my normal login is lurking and causing the issue.
Comment 4 Kevin Coonan 2024-04-21 22:16:37 UTC
Created attachment 874398 [details]
perf report

PS results at same time
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root     13686  7.8  1.0 926116 358788 ?       Ssl  17:02   0:12 /usr/libexec/packagekitd
me       11481  3.1  0.9 2736820 303336 ?      Sl   16:58   0:13  |   |   \_ /usr/lib64/firefox/firefox -contentproc -childID 8 -isForBrowser -prefsLen 33783 -prefMapSize 240114 -jsInitLen 234952 -parentBuildID 20240401114208 -greomni /usr/lib64/firefox/omni.ja -appomni /usr/lib64/firefox/browser/omni.ja -appDir /usr/lib64/firefox/browser {3c5f4c37-fec8-48e6-9247-d7eb1b844ecf} 10796 true tab
me        8290  249  2.1 3979420 702224 ?      Ssl  16:57  19:33  \_ /usr/bin/plasmashell --no-respawn
root      7369 24.6  1.7 854204 559628 tty2    Rsl+ 16:54   2:47  \_ /usr/bin/Xorg.bin -nolisten tcp -background none -seat seat0 vt2 -auth /run/sddm/xauth_xzEHyo -noreset -displayfd 16
me       13199  2.2  0.4 2384036 151916 ?      Sl   17:01   0:05  |   \_ /usr/bin/konsole
vscan     7261  1.9  4.2 1488508 1379456 ?     Ssl  16:54   0:13 /usr/sbin/clamd
me       11021  1.6  0.6 19620248 229668 ?     Sl   16:58   0:07  |   |   \_ /usr/lib64/firefox/firefox -contentproc -childID 2 -isForBrowser -prefsLen 47723 -prefMapSize 240114 -jsInitLen 234952 -parentBuildID 20240401114208 -greomni /usr/lib64/firefox/omni.ja -appomni /usr/lib64/firefox/browser/omni.ja -appDir /usr/lib64/firefox/browser {1d611496-1c5e-48cd-8b59-324498f3089f} 10796 true tab
me       10796 13.6  1.9 3491648 625404 ?      Sl   16:58   1:00  |   \_ /usr/lib64/firefox/firefox
me        8124  101  2.2 2703804 753844 ?      Ssl  16:57   7:57  \_ /usr/bin/kwin_x11 --replace
Comment 5 Kevin Coonan 2024-04-21 22:29:25 UTC
Recent re-install of TW w/ Plasma6 shows very high (>25% of total CPU resources avaible) use by Plashmashell and KWin X11.  Cannot get to start on Wayland, so that isn't much help.  

Kernel: 6.8.7-1-default arch: x86_64 bits: 64 compiler: gcc
    v: 13.2.1
  Desktop: KDE Plasma v: 6.0.4 Distro: openSUSE Tumbleweed 20240419


 10:53 ~ $  inxi -t -cm10 -xxx
Processes:
CPU top: 10 of 347
  1: cpu: 217% command: plasmashell pid: 8193 mem: 968.2 MiB (3.0%)
  2: cpu: 101% command: kwin_x11 pid: 8030 mem: 1523.2 MiB (4.7%)
  3: cpu: 36.6% command: Xorg.bin pid: 7326 mem: 806.7 MiB (2.5%)
  4: cpu: 7.2% command: firefox pid: 24944 mem: 613.6 MiB (1.9%)
  5: cpu: 2.2% command: firefox pid: 25255 mem: 468.5 MiB (1.4%)
  6: cpu: 1.6% command: firefox pid: 25160 mem: 187.1 MiB (0.5%)
  7: cpu: 1.1% command: kactivitymanagerd pid: 8231 mem: 81.8 MiB (0.2%)
  8: cpu: 1.1% command: konsole pid: 13471 mem: 167.5 MiB (0.5%)
  9: cpu: 0.7% command: firefox pid: 25546 mem: 261.3 MiB (0.8%)
  10: cpu: 0.6% command: upowerd pid: 7706 mem: 22.6 MiB (0.0%)
  System RAM: total: 32 GiB available: 31.3 GiB used: 8.54 GiB (27.3%)
  Memory top: 10 of 347
  1: mem: 1523.2 MiB (4.7%) command: kwin_x11 pid: 8030 cpu: 101%
  2: mem: 1346.9 MiB (4.2%) command: clamd pid: 7213 cpu: 0.2%
  3: mem: 968.2 MiB (3.0%) command: plasmashell pid: 8193 cpu: 217%
  4: mem: 806.7 MiB (2.5%) command: Xorg.bin pid: 7326 cpu: 36.6%
  5: mem: 613.6 MiB (1.9%) command: firefox pid: 24944 cpu: 7.2%
  6: mem: 468.5 MiB (1.4%) command: firefox pid: 25255 cpu: 2.2%
  7: mem: 302.9 MiB (0.9%) command: arangod pid: 7330 cpu: 0.4%
  8: mem: 261.3 MiB (0.8%) command: firefox pid: 25546 cpu: 0.7%
  9: mem: 235.9 MiB (0.7%) command: DiscoverNotifier pid: 8490 cpu: 0.0%
  10: mem: 224.8 MiB (0.7%) command: mysqld pid: 7315 cpu: 0.0%




Efforts to clear out all old Plasmoids and even deletng all old Plasma/KDE settings failed to have any impact.
As I noticed it after a DUP that included a kernel update I tested it w/ old kernel but same problem. See below.  

I was able t dump some data from dbus:

 15:51 ~ $  qdbus org.kde.KWin /KWin supportInformation
KWin Support Information:
The following information should be used when requesting support on e.g. https://discuss.kde.org.
It provides information about the currently running instance, which options are used,
what OpenGL driver and which effects are running.
Please post the information provided underneath this introductory text to a paste bin service
like https://paste.kde.org instead of pasting into support threads.

==========================

Version
=======
KWin version: 6.0.4
Qt Version: 6.7.0
Qt compile version: 6.7.0
XCB compile version: 1.17.0

Operation Mode: X11 only

Build Options
=============
KWIN_BUILD_DECORATIONS: yes
KWIN_BUILD_TABBOX: yes
KWIN_BUILD_ACTIVITIES: yes
HAVE_X11_XCB: yes
HAVE_GLX: yes

X11
===
Vendor: The X.Org Foundation
Vendor Release: 12101012
Protocol Version/Revision: 11/0
SHAPE: yes; Version: 0x11
RANDR: yes; Version: 0x14
DAMAGE: yes; Version: 0x11
Composite: yes; Version: 0x4
RENDER: yes; Version: 0xb
XFIXES: yes; Version: 0x50
SYNC: yes; Version: 0x31
GLX: yes; Version: 0x0

Decoration
==========
Plugin: org.kde.breeze
Theme:
Plugin recommends border size: None
onAllDesktopsAvailable: true
alphaChannelSupported: true
closeOnDoubleClickOnMenu: false
decorationButtonsLeft: 0, 2
decorationButtonsRight: 6, 3, 4, 5
borderSize: 0
gridUnit: 10
font: Noto Sans,10,-1,0,400,0,0,0,0,0,0,0,0,0,0,1
smallSpacing: 2
largeSpacing: 10

Output backend
==============
Name: KWin::X11StandaloneBackend

Cursor
======
themeName: breeze_cursors
themeSize: 24

Options
=======
focusPolicy: ClickToFocus
xwaylandCrashPolicy: 1
xwaylandMaxCrashCount: 3
nextFocusPrefersMouse: false
clickRaise: true
autoRaise: false
autoRaiseInterval: 0
delayFocusInterval: 0
shadeHover: false
shadeHoverInterval: 250


I don't know if any of the output from plasmashell -d is of use:
KPackageStructure of KPluginMetaData(pluginId:"org.kde.plasma.clearclock", fileName: "/home/me/.local/share/plasma/plasmoids/org.kde.plasma.clearclock/metadata.json") does not match requested format "Plasma/Applet"
KPackageStructure of KPluginMetaData(pluginId:"Plasma.Control.Hub", fileName: "/home/me/.local/share/plasma/plasmoids/Plasma.Control.Hub/metadata.json") does not match requested format "Plasma/Applet"
KPackageStructure of KPluginMetaData(pluginId:"com.github.configurable_button", fileName: "/home/me/.local/share/plasma/plasmoids/com.github.configurable_button/metadata.json") does not match requested format "Plasma/Applet"
KPackageStructure of KPluginMetaData(pluginId:"org.kde.Date.Bubble.P6", fileName: "/home/me/.local/share/plasma/plasmoids/org.kde.Date.Bubble.P6/metadata.json") does not match requested format "Plasma/Applet"
KPackageStructure of KPluginMetaData(pluginId:"com.nemmayan.clock", fileName: "/home/me/.local/share/plasma/plasmoids/com.nemmayan.clock/metadata.json") does not match requested format "Plasma/Applet"
KPackageStructure of KPluginMetaData(pluginId:"org.kde.plasma.worldclock", fileName: "/usr/share/plasma/plasmoids/org.kde.plasma.worldclock/metadata.json") does not match requested format "Plasma/Applet"
KPackageStructure of KPluginMetaData(pluginId:"org.papylhomme.diskmonitor", fileName: "/usr/share/plasma/plasmoids/org.papylhomme.diskmonitor/metadata.json") does not match requested format "Plasma/Applet"
KPackageStructure of KPluginMetaData(pluginId:"org.kde.weatherWidget", fileName: "/usr/share/plasma/plasmoids/org.kde.weatherWidget/metadata.json") does not match requested format "Plasma/Applet"
KPackageStructure of KPluginMetaData(pluginId:"org.kde.kupapplet", fileName: "/usr/share/plasma/plasmoids/org.kde.kupapplet/metadata.json") does not match requested format "Plasma/Applet"
kf.plasma.quick: Applet preload policy set to 1
file:///usr/share/plasma/plasmoids/org.kde.desktopcontainment/contents/ui/main.qml:196:25: QML FolderViewDropArea (parent or ancestor of QQuickLayoutAttached): Binding loop detected for property "minimumWidth"
file:///usr/share/plasma/plasmoids/org.kde.desktopcontainment/contents/ui/main.qml:196:25: QML FolderViewDropArea (parent or ancestor of QQuickLayoutAttached): Binding loop detected for property "minimumWidth"
qt.svg.draw: The requested buffer size is too big, ignoring
org.kde.plasma.kicker: Entry is not valid "writer.desktop" 0x5585eb583120
org.kde.plasma.kicker: Entry is not valid "org.kde.Help.desktop" 0x5585eb5810c0
file:///usr/share/plasma/plasmoids/org.kde.plasma.private.systemtray/contents/ui/main.qml:162:21: QML KSortFilterProxyModel: Binding loop detected for property "sourceModel"
file:///usr/share/plasma/plasmoids/org.kde.plasma.private.systemtray/contents/ui/main.qml:162:21: QML KSortFilterProxyModel: Binding loop detected for property "sourceModel"
qml: SystemTray ItemLoader: Invalid state, cannot determine source!
qt.dbus.integration: Could not connect "org.cups.cupsd.Notifier" to PrinterFinishingsChanged(QString, QString, QString, uint, QString, bool) :
Process "nordvpn status" already running. Pid: 9465
QFont::setPointSizeF: Point size <= 0 (0.000000), must be greater than 0



Advice about using journalctl not very helpful:
From journalctl:
Apr 21 11:39:27 beryl plasmashell[7736]: kf.kio.core: -miniicon isn't supported anymore (service "" )
Apr 21 11:39:27 beryl plasmashell[7736]: kf.kio.core: -miniicon isn't supported anymore (service "" )
Apr 21 11:39:28 beryl plasmashell[7736]: kf.runner: Error requesting matches; calling "org.kde.runners.baloo"  : "org.freedesktop.DBus.Error.NotSupported" ""
Apr 21 11:39:28 beryl plasmashell[7736]: kf.runner: Error requesting matches; calling "org.kde.runners.baloo"  : "org.freedesktop.DBus.Error.NotSupported" ""
Apr 21 11:41:53 beryl plasmashell[7736]: kf.runner: Error requesting matches; calling "org.kde.runners.baloo"  : "org.freedesktop.DBus.Error.NotSupported" ""
Apr 21 11:41:53 beryl plasmashell[7736]: kf.runner: Error requesting matches; calling "org.kde.runners.baloo"  : "org.freedesktop.DBus.Error.NotSupported" ""
Apr 21 11:56:46 beryl plasmashell[7736]: file:///usr/share/plasma/plasmoids/org.kde.plasma.notifications/contents/ui/global/Globals.qml:136: TypeError: Cannot read property 'screenGeometry' of null
Apr 21 11:56:47 beryl plasmashell[7736]: QObject::killTimer: Timers cannot be stopped from another thread
Apr 21 11:56:47 beryl plasmashell[7736]: QObject::~QObject: Timers cannot be stopped from another thread
Apr 21 11:56:47 beryl plasmashell[7736]: file:///usr/share/plasma/plasmoids/org.kde.plasma.notifications/contents/ui/global/Globals.qml:

This is what I could get from KWin:
Efforts to use GDB to get a backtrace were not so helpful:  Thread 60 (Thread 0x7fbdb9e006c0 (LWP 30326) "Thread (pooled)"):
#0  0x00007fbe3228effe in __futex_abstimed_wait_common64 (private=0, cancel=true, abstime=0x7fbdb9dff9b0, op=137, expected=0, futex_word=0x5652ed50c740) at futex-internal.c:57
#1  __futex_abstimed_wait_common (futex_word=futex_word@entry=0x5652ed50c740, expected=expected@entry=0, clockid=clockid@entry=1, abstime=abstime@entry=0x7fbdb9dff9b0, private=private@entry=0, cancel=cancel@entry=true) at futex-internal.c:87
#2  0x00007fbe3228f09f in __GI___futex_abstimed_wait_cancelable64 (futex_word=futex_word@entry=0x5652ed50c740, expected=expected@entry=0, clockid=clockid@entry=1, abstime=abstime@entry=0x7fbdb9dff9b0, private=private@entry=0) at futex-internal.c:139
#3  0x00007fbe32292065 in __pthread_cond_wait_common (abstime=0x7fbdb9dff9b0, clockid=1, mutex=0x5652ed50c6f0, cond=0x5652ed50c718) at pthread_cond_wait.c:503
#4  ___pthread_cond_timedwait64 (cond=0x5652ed50c718, mutex=0x5652ed50c6f0, abstime=0x7fbdb9dff9b0) at pthread_cond_wait.c:643
#5  0x00007fbe32cf9413 in QWaitConditionPrivate::wait_relative(QDeadlineTimer) (deadline=..., this=0x5652ed50c6f0) at /usr/src/debug/qtbase-everywhere-src-6.7.0/src/corelib/thread/qwaitcondition_unix.cpp:92
#6  QWaitConditionPrivate::wait(QDeadlineTimer) (deadline=..., this=0x5652ed50c6f0) at /usr/src/debug/qtbase-everywhere-src-6.7.0/src/corelib/thread/qwaitcondition_unix.cpp:100
#7  QWaitCondition::wait(QMutex*, QDeadlineTimer) (this=<optimized out>, mutex=0x5652e4c9be48, deadline=...) at /usr/src/debug/qtbase-everywhere-src-6.7.0/src/corelib/thread/qwaitcondition_unix.cpp:180
#8  0x00007fbe32cf3d49 in QThreadPoolThread::run() (this=0x5652e98841a0) at /usr/src/debug/qtbase-everywhere-src-6.7.0/src/corelib/thread/qthreadpool.cpp:116
#9  0x00007fbe32cecea9 in operator() (__closure=<optimized out>) at /usr/src/debug/qtbase-everywhere-src-6.7.0/src/corelib/thread/qthread_unix.cpp:326
#10 (anonymous namespace)::terminate_on_exception<QThreadPrivate::start(void*)::<lambda()> > (t=<optimized out>) at /usr/src/debug/qtbase-everywhere-src-6.7.0/src/corelib/thread/qthread_unix.cpp:262
#11 QThreadPrivate::start(void*) (arg=0x5652e98841a0) at /usr/src/debug/qtbase-everywhere-src-6.7.0/src/corelib/thread/qthread_unix.cpp:285
#12 0x00007fbe32292bb2 in start_thread (arg=<optimized out>) at pthread_create.c:447
#13 0x00007fbe3231400c in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:78