[Bug 195321] New: nouveau?/DRI3?: dual monitors unusable without running compton --paint-on-overlay

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=195321

            Bug ID: 195321
           Summary: nouveau?/DRI3?: dual monitors unusable without running
                    compton --paint-on-overlay
           Product: Drivers
           Version: 2.5
    Kernel Version: 4.10.8
          Hardware: Intel
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI - non Intel)
          Assignee: drivers_video-dri at kernel-bugs.osdl.org
          Reporter: JimiJames.Bove at gmail.com
        Regression: No

Last known good version: 4.9.8
Software: Arch Linux, XFCE, compton, nouveau (using DRI3)
Hardware: NVIDIA Corporation GK107 [GeForce GT 740] (rev a1)

The behavior *and* workaround for this bug are 100% identical to
https://bugs.freedesktop.org/show_bug.cgi?id=97916

Quoting its behavior because they explained it way better than I could:
With default settings (no xorg.conf), dual monitors can only be used in "clone"
mode.  When trying to switch to "extend" mode, the right-hand display freezes
and continues to display a snapshot of the cloned display contents at the time
of the switch.  Using Option "DRI" "2" in xorg.conf is a workaround.

But the cause is clearly different, because of 3 major differences from that
bug report:
1. I started having this issue when I upgraded the kernel to 4.9.10 from 4.9.8,
rather than when it started for him: 4.7.4. And yes, I already tested to
confirm that this behavior changes between those two versions of Linux, and not
with any other upgrade or downgrade to any of my other packages (not even
nouveau, mesa, or xorg).
2. When X and XFCE first run, this behavior doesn't  happen at all (assuming it
wasn't happening before I shut it down). My dual-monitor setup still works
properly. However, once I disconnect that monitor--or if it was disconnected
when I rebooted, causing my system to remember that on boot--this behavior
starts, and does not go away until I disable and enable the monitor in XFCE's
Display preferences, which then restores the proper behavior until the next
disconnect. It specifically has to be XFCE's Display preferences. Adding a
regular, simple (using nothing but two Monitor sections and Identifiers
matching the monitor names) dual-monitor .conf file to xorg.conf.d/ actually
made it worse by causing this behavior to start immediately at boot no matter
what, and for some reason xrandr couldn't turn the monitor back on after
running xrandr --output <output> --off (though XFCE's preferences COULD turn it
back on).
3. I still have this behavior when compton is disabled and I'm not running any
compositor at all. I specifically have to either downgrade the kernel or run
compton with the --paint-on-overlay option to fix it.
3.5. I have not yet tested for whether switching to DRI2 is another workaround
like it is for that bug. It's been a long night and I'm taking a break.

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