This may well be a driver issue, but I report it nonetheless, so you are aware of it. I can report driver bug as well, if desired. When I start a second Plasma session on VT8 using GLX with OpenGL 3.1 as compositor backend + having DRI 3 enabled then after a short time when I switch back to the original session at VT7 I just see a blank screen there. Brightness is zero, so its really not just blank, but backlight is switched off. When I switch to TTY1 then, it is almost black, brightness is very low. I can raise it there, but VT7 is gone for good. In original bug report where I suspected kscreen to be the culprit I reported what I tried to recover the session which includes pressing a key,writing high brightness values to /sys/[path to Intel/ACPI blacklight]/bl_power, xrandr --auto, vbetool dpms off, disabling KScreen 2 + Powerdevil on both sessions, rm -r ~/.local/share/kscreen, masking systemd backlight service, fiddling around with Solid brightness controls and also kwin_x11 --replace. I first thought this to be a bug in kscreen, but as it disappears when either using XRender or disabling DRI 3, I think its a KWin compositor/GLX backend *and/or* a driver issue: Bug 359177 - blanks out original plasma session when I start a new a new plasma session from it Reproducible: Always Steps to Reproduce: 1. Use Intel Sandybridge HD 3000 graphics (maybe fails with others as well, don´t know) 2. Enable DRI 3. 3. Have two sessions with GLX + OpenGL 3.1 as compositing backend. 4. Start into first session. 5. Start second session. 6. Switch back to first session after a while with Ctrl-Alt-F7. 7. Maybe you need to switch between sessions several times. Actually it also happens when just one of the sessions is a Plasma session with GLX + OpenGL 3.1. Actual Results: One of the Plasma sessions or the Plasma session (if one one of them is a Plasma session) has a black screen after switching to it. It never happens to the non Plasma session like MATE or LXDE. Expected Results: Sessions continues to work just fine. Working X11 configuration: martin@merkaba:~> cat /etc/X11/xorg.conf.d/anzeige.conf Section "Device" Identifier "Grafikkern" Driver "intel" # Option "Backlight" "/dev/null" Option "AccelMethod" "uxa" # Option "AccelMethod" "sna" # Option "TearFree" "true" # Option "DRI" "3" EndSection Issue happens when you enable the Option DRI 3 line + GLX with OpenGL 3.1 compositing backend. Acceleration method UXA is essential to prevent hard lockups (one of them caused me a loss of public GPG key ring after a key signing at DebConf 2015). It does not happen when using XRender as compositing backend or when DRI 3 line is commented out. kwin-x11 5.4.3 as packages with or without self-compiled KF5 + KDEPIM from Git master: martin@merkaba:~> LANG=C apt-cache policy kwin-x11 kwin-x11: Installed: 4:5.4.3-1.1 Candidate: 4:5.4.3-1.1 Version table: 4:5.5.4-2 200 200 http://httpredir.debian.org/debian experimental/main amd64 Packages *** 4:5.4.3-1.1 500 500 http://httpredir.debian.org/debian sid/main amd64 Packages 100 /var/lib/dpkg/status I can try the experimental version, if its not compiled with Qt 5.6 (the build for Debian experimental used Qt 5.6 which last time I tried was not yet complete in experimental). I could even add kwin to kdesrc-build or so to build it from master as well (just don´t want to have to build complete Plasma from git due to space constraints on SSDs). It happens on ThinkPad T520 with internal Full HD display second 23 inch Full HD display. # phoronix-test-suite system-info Phoronix Test Suite v5.2.1 System Information Hardware: Processor: Intel Core i5-2520M @ 3.20GHz (4 Cores), Motherboard: LENOVO 42433WG, Chipset: Intel 2nd Generation Core Family DRAM, Memory: 16384MB, Disk: 300GB INTEL SSDSA2CW30 + 480GB Crucial_CT480M50, Graphics: Intel HD 3000 (1300MHz), Audio: Conexant CX20590, Monitor: P24T-7 LED, Network: Intel 82579LM Gigabit Connection + Intel Centrino Advanced-N 6205 Software: OS: Debian unstable, Kernel: 4.4.0-tp520-btrfstrim+ (x86_64), Desktop: KDE Frameworks 5, Display Server: X Server 1.18.1, Display Driver: intel 2.99.917, OpenGL: 3.3 Mesa 11.1.2, Compiler: GCC 5.3.1 20160220, File-System: btrfs, Screen Resolution: 3840x1080 # apt list | egrep "kwin-x11|xserver-xorg/|xserver-xorg-core/|xserver-xorg-video-intel|libdrm-intel|libgl1-mesa-dri" | grep -v dbg […] kwin-x11/unstable,now 4:5.4.3-1.1 amd64 [installiert] libdrm-intel1/unstable,now 2.4.67-1 amd64 [Installiert,automatisch] libgl1-mesa-dri/unstable,now 11.1.2-1 amd64 [installiert] xserver-xorg/unstable,now 1:7.7+13 amd64 [installiert] xserver-xorg-core/unstable,now 2:1.18.1-1 amd64 [Installiert,automatisch] xserver-xorg-video-intel/unstable,now 2:2.99.917+git20160218-1 amd64 [installiert]
KWin doesn't adjust the brightness level at all. So might be that power management does something?
> and also kwin_x11 --replace This doesn't resolve anything? What if you (also) suspend the compositor in the other session before switching back? Could it be the session is locked (and the greeter is black)? => try to "loginctl unlock-session", "loginctl list-sessions" lists them - surprisingly ;-) and check out for kscreenlocker_greet processes.
Thomas kwin_x11 --replace didn´t get the session back. Not even killing kwin (SIGKILL was needed if I remember correctly) and starting it with dbus-launch + export $DISPLAY from other terminal. I think I have seen without and with locked sessions. But I can try this. For today working at homeoffice I prefer stable operation tough. Martin, what I now see without DRI 3 enabled but with GLX + OpenGL 3.1 on both session is this: When I switch from one session to another one after the time where powermanagement usually kicks in the following happens: 1) It shows the session as it. 2) It fades it to black. 3) It fades it back to normal brightness. But, with DRI3 enabled and the issue happened, it stayed black. AFAIR remember it (=whatever does it) showed the session for a short time after switching and then switched it to black. Also with DRI3 enabled I also had black sessions when both powerdevil and kscreen services were disabled (that is all in the original report). That said, maybe X.org itself blanked the display. So the only thing I currently have: DRI 3 + GLX backend with OpenGL 3.1 => blanked session at some time. These are the only factors I could determine for sure at the moment. Whether powerdevil and kscreen services running or not, or kernel 4.4 oder kernel 4.5-rc4 or self-compiled KF5 or packaged KF5 all made no difference.
Thank you for the bug report. As this report hasn't seen any changes in 5 years or more, we ask if you can please confirm that the issue still persists. If this bug is no longer persisting or relevant please change the status to resolved.
This bug was reported against an outdated version of KWin. We have made many changes since the. If the issue persists in newer versions can you reopen the bug report updating the version number.