Unlocking screen on dual monitor setup causes black screen

[Salem]

After unlock the screen on a dual monitor setup both screens stay completely black, and I can't access the desktop (mouse cursor is visible and I can move it). This only happens when using an external monitor (connected through HDMI).

Expected behavior: after providing the password to the unlock screen, I should access the desktop;
What happens: both screens stay black and I can't access the desktop.

How to reproduce:
1- Having a laptop with an external monitor connected (no mirroring)
2- Lock screen
3- Wait > 5 seconds
4- Touch the mouse/keyboard: the unlocking window appears on one screen (the other stays black)
5- After typing the password both screens remain completely black

Tests in various desktop managers:
* Unity: screens stay black after unlocking;
* Cinnamon: works as expected (unlocking gets you to desktop);
* Gnome classic (fallback): same behavior as Unity;
* Gnome classic (no effects): works as expected.

I have also tested with xscreensaver on Unity and the screens stays black. So the problem should be with Compiz.

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: compiz 1:0.9.8.6-0ubuntu1
ProcVersionSignature: Ubuntu 3.5.0-23.35-generic 3.5.7.2
Uname: Linux 3.5.0-23-generic x86_64
ApportVersion: 2.6.1-0ubuntu10
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
Date: Sat Feb 16 18:59:51 2013
InstallationDate: Installed on 2012-12-03 (74 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.5)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: compiz
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Salem (salemsaberhagen)]

Added Xorg log and Unity log (gathered from a tty with "unity --replace >
unity.log 2>&1").

I have reverted compiz package from 1:0.9.8.6-0ubuntu1
to 1:0.9.8.4-0ubuntu2 and I still get the black screens.
Also I would like to notice that I don't always get the black screens after
unlocking, but it is quite frequent (8/10 times).

2013/2/17 Launchpad Bug Tracker <email address hidden>

> Status changed to 'Confirmed' because the bug affects multiple users.
>
> ** Changed in: compiz (Ubuntu)
> Status: New => Confirmed
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1127439
>
> Title:
> Unlocking screen on dual monitor setup causes black screen
>
> Status in “compiz” package in Ubuntu:
> Confirmed
>
> Bug description:
> After unlock the screen on a dual monitor setup both screens stay
> completely black, and I can't access the desktop (mouse cursor is
> visible and I can move it). This only happens when using an external
> monitor (connected through HDMI).
>
> Expected behavior: after providing the password to the unlock screen, I
> should access the desktop;
> What happens: both screens stay black and I can't access the desktop.
>
> How to reproduce:
> 1- Having a laptop with an external monitor connected (no mirroring)
> 2- Lock screen
> 3- Wait > 5 seconds
> 4- Touch the mouse/keyboard: the unlocking window appears on one screen
> (the other stays black)
> 5- After typing the password both screens remain completely black
>
> Tests in various desktop managers:
> * Unity: screens stay black after unlocking;
> * Cinnamon: works as expected (unlocking gets you to desktop);
> * Gnome classic (fallback): same behavior as Unity;
> * Gnome classic (no effects): works as expected.
>
> I have also tested with xscreensaver on Unity and the screens stays
> black. So the problem should be with Compiz.
>
> ProblemType: Bug
> DistroRelease: Ubuntu 12.10
> Package: compiz 1:0.9.8.6-0ubuntu1
> ProcVersionSignature: Ubuntu 3.5.0-23.35-generic 3.5.7.2
> Uname: Linux 3.5.0-23-generic x86_64
> ApportVersion: 2.6.1-0ubuntu10
> Architecture: amd64
> CompizPlugins: No value set for
> `/apps/compiz-1/general/screen0/options/active_plugins'
> Date: Sat Feb 16 18:59:51 2013
> InstallationDate: Installed on 2012-12-03 (74 days ago)
> InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release amd64
> (20121017.5)
> MarkForUpload: True
> PackageArchitecture: all
> ProcEnviron:
> TERM=xterm
> PATH=(custom, no user)
> XDG_RUNTIME_DIR=<set>
> LANG=en_US.UTF-8
> SHELL=/bin/bash
> SourcePackage: compiz
> UpgradeStatus: No upgrade log present (probably fresh install)
>
> To manage notifications about this bug go to:
>
> https://bugs.launchpad.net/ubuntu/+source/compiz/+bug/1127439/+subscriptions
>