[Bug 88960] New: X server comes up with black screen if screensaver is activated on another X server

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=88960

            Bug ID: 88960
           Summary: X server comes up with black screen if screensaver is
                    activated on another X server
           Product: xorg
           Version: unspecified
          Hardware: All
                OS: Linux (All)
            Status: NEW
          Severity: major
          Priority: medium
         Component: Driver/intel
          Assignee: chris at chris-wilson.co.uk
          Reporter: maxtram95 at gmail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org

Created attachment 113142
  --> https://bugs.freedesktop.org/attachment.cgi?id=113142&action=edit
Xorg on vt7 log

I'm on Gentoo, video card is 945GSE, xorg 1.16.3, xf86-video-intel 2.99.917
(SNA), linux 3.18.5. I also use lightdm and systemd. Important note: I have no
fbcon kernel module loaded, so there are no text VTs on my laptop.

Suppose we have X session (only terminal emulator in my case) running on vt7
started from lightdm. "dm-tool switch-to-greeter" is a command that should
start second X server on vt8, display lightdm greeter there, and switch to vt8
so that I could login as different user or unlock my session on vt7. It works
fine if screensaver is not active.

If I run the following command: "sleep 0.1; xset s activate; dm-tool
switch-to-greeter", second X server on vt8 comes up, greeter also starts, but
screen remains blank. I can enter my password blindly and return to vt7, screen
turns on then.

So the issue is that if I have Xorg running with screensaver active (and the
screen blanked), and I start another Xorg (via lightdm, "dm-tool
switch-to-greeter"), second Xorg will come up with screen turned off. This is
major blocker for me, because normally I use Xfce, lightdm and light-locker,
and when screensaver automatically activates after 5 minutes of inactivity,
light-locker does the switch to vt8 where lightdm greeter should appear, but
screen remains blank, so I can only enter my password blindly.

Some other test cases:

If I modprobe fbcon, bug disappears. What I think about this:
1. Without fbcon: Xorg on vt7 turns off the screen (xset s activate), then we
get switched to vt8 (screen remains off), then Xorg on vt8 starts and does not
turn on the screen.
2. With fbcon: Xorg on vt7 turns off the screen (xset s activate), then we get
switched to vt8, fbcon turns screen on, then Xorg on vt8 starts with screen
already turned on.

If I replace "xset s activate" with "xset dpms force on", bug disappears.

If I run "DISPLAY=:1 xrandr --auto" when Xorg on vt8 starts, screen turns on.

Steps to reproduce (sorry, I failed to start X server without lightdm):
1. Setup lightdm and disable fbcon kernel module.
2. Setup simple minimalistic X session: create file ~/.xsession and put command
to start your favorite terminal emulator (xfce4-terminal in my case) into that
file.
3. Login using lightdm to this session.
4. Open two tabs in your terminal emulator; get root in one of them (e.g. using
"sudo -i").
5. Put the following command into root shell:
sleep 10; DISPLAY=:1 xrandr --current; DISPLAY=:1 xrandr --auto; DISPLAY=:1
xrandr --current
6. Put the following command into your user's shell:
sleep 0.1; xset s activate; dm-tool switch-to-greeter
7. Run the first command, then the second one.
8. Screen should go blank (screensaver activates).
9. Second Xorg on vt8 starts. VT8 activates, but screen is blank (bug here).
10. After 10 seconds "xrandr --auto" will run (do you remember the command in
root shell?), screen will turn on.
11. Enter your password to return to vt7.
12. Here is my output from xrandr commands:
before xrandr --auto (something very wrong):
----
xrandr: Output LVDS1 is not disconnected but has no modes
xrandr: Output VGA1 is not disconnected but has no modes
xrandr: Output VIRTUAL1 is not disconnected but has no modes
Screen 0: minimum 8 x 8, current 1024 x 600, maximum 32767 x 32767
LVDS1 connected (normal left inverted right x axis y axis)
VGA1 connected (normal left inverted right x axis y axis)
VIRTUAL1 connected (normal left inverted right x axis y axis)
----
after xrandr --auto (good):
----
Screen 0: minimum 8 x 8, current 1024 x 600, maximum 32767 x 32767
LVDS1 connected 1024x600+0+0 (normal left inverted right x axis y axis) 220mm x
129mm
   1024x600      60.00*+  65.00  
   800x600       60.32    56.25  
   640x480       59.94  
VGA1 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)
----

I also attach logs for two Xorg instances involved.

Why do I think it is intel driver bug? Because xrandr --current shows something
really messy when Xorg is started with blank screen. Driver should initialize
video modes on startup.

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