Has anyone else run into this?

If I log in as a second user kscreenlocker_greet goes into a loop of crashing and coredumps. This causes a fair amount of CPU usage, averaging about 25% for all cores. furthermore, if I switch back and fourth between the two running sessions, the system will eventually go into "graphical meltdown"- filling the screen with garbage in a "shattered glass" pattern. The system will then need to be rebooted from a tty. Turning off compositing for both logins fixes this, but Plasma 5's "flat" look is way too flat without the 3D effects of compositing.

This is happening on Arch Linux with the Nvidia driver. A log excerpt from the coredump loop follows.


May 23 19:07:35 itldesk kscreenlocker_greet[3869]: [1;39mfile:///usr/share/plasma/look-and-feel/org.kde.breeze.desktop/contents/components/UserDelegate.qml:82:9: QML Image: Cannot open: file:///usr/share/plasma/look-and-feel/org.kde.breeze.desktop/contents/components/user-identity[0m
May 23 19:07:35 itldesk kscreenlocker_greet[3869]: [1;39mfile:///usr/share/plasma/look-and-feel/org.kde.breeze.desktop/contents/components/UserDelegate.qml:82:9: QML Image: Cannot open: file:///usr/share/plasma/look-and-feel/org.kde.breeze.desktop/contents/components/system-log-out[0m
May 23 19:07:35 itldesk kscreenlocker_greet[3869]: [1;39mfile:///usr/share/plasma/look-and-feel/org.kde.breeze.desktop/contents/components/UserDelegate.qml:82:9: QML Image: Cannot open: file:///usr/share/plasma/look-and-feel/org.kde.breeze.desktop/contents/components/system-switch-user[0m
May 23 19:07:35 itldesk kernel: QSGRenderThread[3874]: segfault at 0 ip 00007f800455d34d sp 00007f7fdb094ce8 error 4 in libc-2.21.so[7f80044c4000+199000]
May 23 19:07:35 itldesk kdeinit5[1134]: UnmapNotify: 2097162
May 23 19:07:35 itldesk kdeinit5[1134]: CreateNotify: 2097154
May 23 19:07:35 itldesk kdeinit5[1134]: CreateNotify: 2097156
May 23 19:07:35 itldesk kscreenlocker_greet[3876]: [1;39mCould not find drkonqi at /usr/lib/drkonqi[0m
May 23 19:07:35 itldesk kscreenlocker_greet[3876]: kwayland-client: Connected to Wayland server over file descriptor: 29
May 23 19:07:35 itldesk kdeinit5[1134]: CreateNotify: 2097159
May 23 19:07:35 itldesk kdeinit5[1134]: CreateNotify: 2097161
May 23 19:07:36 itldesk systemd-coredump[3875]: Removed old coredump core.kscreenlocker_g.1001.9330bf989be447e4bca564275a3cb7fc.3778.1432426048000000.lz4.
May 23 19:07:36 itldesk systemd-coredump[3875]: [1;31mProcess 3869 (kscreenlocker_g) of user 1001 dumped core.[0m
May 23 19:07:36 itldesk kdeinit5[1078]: [1;39mSkipped method "moduleDeleted" : Pointers are not supported: KDEDModule*[0m
May 23 19:07:36 itldesk kdeinit5[1078]: kcm_keyboard: Fetched layout groups from X server: layouts: ("us") variants: ("")
May 23 19:07:36 itldesk kdeinit5[1078]: kcm_keyboard: Fetched layout groups from X server: layouts: ("us") variants: ("")
May 23 19:07:36 itldesk kscreenlocker_greet[3876]: [1;39mfile:///usr/share/plasma/look-and-feel/org.kde.breeze.desktop/contents/components/InfoPane.qml:52:22: Unable to assign [undefined] to int[0m
May 23 19:07:36 itldesk kscreenlocker_greet[3876]: [1;39mfile:///usr/share/plasma/look-and-feel/org.kde.breeze.desktop/contents/lockscreen/LockScreen.qml:166: TypeError: Cannot read property 'showPassword' of undefined[0m
May 23 19:07:36 itldesk kscreenlocker_greet[3876]: [1;39mfile:///usr/share/plasma/look-and-feel/org.kde.breeze.desktop/contents/lockscreen/LockScreen.qml:208: TypeError: Cannot read property 'ButtonLabel' of undefined[0m
May 23 19:07:36 itldesk kdeinit5[1134]: CreateNotify: 2097162
May 23 19:07:36 itldesk kdeinit5[1134]: MapNotify: 2097162
May 23 19:07:36 itldesk kdeinit5[1134]: uhoh! duplicate!
May 23 19:07:36 itldesk kscreenlocker_greet[3876]: org.kde.keyboardLayout: Layouts list changed: ("us")
May 23 19:07:36 itldesk kdeinit5[1134]: uhoh! duplicate!
May 23 19:07:36 itldesk kscreenlocker_greet[3876]: kwayland-client: Unknown interface announced: org_kde_ksld / 1 / 2
May 23 19:07:36 itldesk kdeinit5[1134]: CreateNotify: 2097166
May 23 19:07:36 itldesk kscreenlocker_greet[3876]: [1;39mfile:///usr/share/plasma/look-and-feel/org.kde.breeze.desktop/contents/components/UserDeleg

Yes and there're bug reports about simply moving to another TTY is enough to cause this.
Long story short: faaar too many GL contexts.

I assume waiting for the vblank signal or the explicit sync fences or just "massive" usage of VBOs cause this.
Assume you'd be playing three or four instances of Quake4 on each VT...

You may try setting the "tearing prevention" to "none" as well as

Code: Select all

export KWIN_EXPLICIT_SYNC=0
export KWIN_USE_BUFFER_AGE=0
kwin_x11 --replace &


But expect your system to go south nevertheless.
Restarting X11 (w/ the ever restarting greeter) is btw. sufficient, in doubt kill ksmserver.

thanks for the reply. I tried executing the commands you gave me in both loggins, but this made CPU usage worse if anything. Any other ideas other than waiting for Wayland? Actually it sounds like Wayland might be usable in plasma 5.4,

http://blog.martin-graesslin.com/blog/2 ... side-down/

Of course this will bring a plethora of new bugs with it.

For now, wayland is not available on the nvidia driver anyway.
It will however -hopefully- resolve the situation in that there won't be a pleathora of different GL contexts.

However, what you encounter here is "just" a series of bugs that need to be fixed/worked around "anyway"
Notably the re-crashes of the lockscreen greeter: aside an actual fix of the crash (which may be due to Qt or libgl) eg. there could be a dumb failsafe variant (no qml, no gl, no fancyness - just a stupid qdialog) that would be invoked after the third crash in a row or so.
The other requirement would be for kwin to somehow™ detect the garbage VBO memory and reset VBOs (please don't ask me right now, what that "somehow™" is supposed to be)