'dm-tool lock' cause login panel flash & black screen after unlock.

[Hacksign]

lightdm-gtk-greeter work normally after boot.
but it flashes after I locked my screen with 'dm-tool lock' and light monitor up again.
the login panel moves very fast from right to left on the monitor,a picture can be found here:
http://www.hacksign.cn/612022797.jpg

after I login in with correct username & password.
My extended monitor lighted up, but the primary monitor still black.I had to light it up with 'xrandr --output eDP1 --off && xrandr --output eDP1 --auto' manually.
cpu usage is normal after login in.

below is some extra information:

hacksign@XSign [10:42:37] : ~
>> lightdm --version
lightdm 1.14.2
hacksign@XSign [10:42:41] : ~
>> lightdm-gtk-greeter --version
** Message: Starting lightdm-gtk-greeter 2.0.1 (May 26 2015, 08:48:40)
** Message: [Configuration] Reading file: /etc/lightdm/lightdm-gtk-greeter.conf

** (lightdm-gtk-greeter:12273): WARNING **: No LIGHTDM_TO_SERVER_FD environment variable

** (lightdm-gtk-greeter:12273): WARNING **: No LIGHTDM_FROM_SERVER_FD environment variable
DEBUG-Message: Connecting to display manager...

[root@XSign lightdm]# pwd
/var/log/lightdm
[root@XSign lightdm]# ls -la
总用量 16
drwx--x--x 2 root lightdm 4096 Jul 20 10:12 .
drwxr-xr-x 8 root root 4096 Jul 20 10:12 ..
-rw------- 1 root root 3963 Jul 20 10:12 x-1-greeter.log
-rw------- 1 root root 958 Jul 20 10:12 x-1.log
[root@XSign lightdm]# cat x-1*
** Message: Starting lightdm-gtk-greeter 2.0.1 (May 26 2015, 08:48:40)
** Message: [Configuration] Reading file: /etc/lightdm/lightdm-gtk-greeter.conf
DEBUG-Message: Connecting to display manager...
DEBUG-Message: Wrote 22 bytes to daemon
DEBUG-Message: Read 8 bytes from daemon
DEBUG-Message: Read 174 bytes from daemon
DEBUG-Message: Connected version=1.14.2 default-session=awesome show-manual-login=false lock-screen=true hide-users=true has-guest-account=false show-remote-login=true
DEBUG-Message: [Configuration] GTK+ theme: 'Adwaita'
DEBUG-Message: [Configuration] Icons theme: 'Adwaita'
DEBUG-Message: [Configuration] Changing font to 'Terminal'
DEBUG-Message: [Configuration] Font: 'Terminal'
DEBUG-Message: [PIDs] Command executed (#3951): /usr/lib/at-spi2-core/at-spi-bus-launcher

** (lightdm-gtk-greeter:3948): WARNING **: [PIDs] Failed to execute command: upstart

(lightdm-gtk-greeter:3948): GLib-GObject-WARNING **: The property GtkWidget:margin-left is deprecated and shouldn't be used anymore. It will be removed in a future version.

(lightdm-gtk-greeter:3948): GLib-GObject-WARNING **: The property GtkWidget:margin-right is deprecated and shouldn't be used anymore. It will be removed in a future version.

(lightdm-gtk-greeter:3948): GLib-GObject-WARNING **: The property GtkImage:stock is deprecated and shouldn't be used anymore. It will be removed in a future version.
DEBUG-Message: Loaded session /usr/share/xsessions/awesome.desktop (awesome, Highly configurable framework window manager)
DEBUG-Message: [Configuration] Monitor configuration found: '*'
DEBUG-Message: [Background] Connecting to screen: 0x22280c0 (4480x1440px, 945x304mm)
DEBUG-Message: [Background] Monitors found: 2
DEBUG-Message: [Background] Monitor: eDP1 #0 (2560x1440 at 0x0) primary
DEBUG-Message: [Background] No configuration options for monitor eDP1 #0, using default
DEBUG-Message: [Background] Monitor: HDMI2 #1 (1920x1080 at 2560x0)
DEBUG-Message: [Background] No configuration options for monitor HDMI2 #1, using default
DEBUG-Message: [Background] Creating DBus proxy

(lightdm-gtk-greeter:3948): GLib-CRITICAL **: g_variant_get_type: assertion 'value != NULL' failed

(lightdm-gtk-greeter:3948): GLib-CRITICAL **: g_variant_type_is_subtype_of: assertion 'g_variant_type_check (type)' failed

(lightdm-gtk-greeter:3948): GLib-CRITICAL **: g_variant_get_boolean: assertion 'g_variant_is_of_type (value, G_VARIANT_TYPE_BOOLEAN)' failed

(lightdm-gtk-greeter:3948): GLib-CRITICAL **: g_variant_unref: assertion 'value != NULL' failed
DEBUG-Message: [Background] UPower.LidIsPresent property value: 0
DEBUG-Message: [Background] Active monitor is not specified, using first enabled monitor from 'active-monitor' list
DEBUG-Message: [Background] Active monitor changed to: eDP1 #0
DEBUG-Message: Starting authentication for user (null)...
DEBUG-Message: Wrote 16 bytes to daemon
DEBUG-Message: Run Gtk loop...
DEBUG-Message: Read 8 bytes from daemon
DEBUG-Message: Read 26 bytes from daemon
DEBUG-Message: Prompt user with 1 message(s)
DEBUG-Message: Loading users from org.freedesktop.Accounts
DEBUG-Message: User /org/freedesktop/Accounts/User1000 added
DEBUG-Message: Starting authentication for user hacksign...
DEBUG-Message: Wrote 24 bytes to daemon
DEBUG-Message: Read 8 bytes from daemon
DEBUG-Message: Read 38 bytes from daemon
DEBUG-Message: Prompt user with 1 message(s)
DEBUG-Message: Providing response to display manager
DEBUG-Message: Wrote 25 bytes to daemon
DEBUG-Message: Read 8 bytes from daemon
DEBUG-Message: Read 20 bytes from daemon
DEBUG-Message: Authentication complete for user hacksign with return code 0
DEBUG-Message: Wrote 22 bytes to daemon
DEBUG-Message: Starting session awesome
DEBUG-Message: Wrote 19 bytes to daemon
DEBUG-Message: Read 8 bytes from daemon
DEBUG-Message: Read 4 bytes from daemon
DEBUG-Message: SIGTERM received
DEBUG-Message: [PIDs] Process terminated: #3951
DEBUG-Message: Killing greeter with exit()...

X.Org X Server 1.17.2
Release Date: 2015-06-16
X Protocol Version 11, Revision 0
Build Operating System: Linux 4.0.4-2-ARCH x86_64
Current Operating System: Linux XSign 4.1.2-2-ARCH #1 SMP PREEMPT Wed Jul 15 08:30:32 UTC 2015 x86_64
Kernel command line: initrd=\initramfs-linux.img root=/dev/sda3 rw
Build Date: 15 July 2015 04:09:05PM

Current version of pixman: 0.32.6
 Before reporting problems, check http://wiki.x.org
 to make sure that you have the latest version.
Markers: (--) probed, (**) from config file, (==) default setting,
 (++) from command line, (!!) notice, (II) informational,
 (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: "/var/log/Xorg.1.log", Time: Mon Jul 20 10:12:17 2015
(==) Using config directory: "/etc/X11/xorg.conf.d"
(==) Using system config directory "/usr/share/X11/xorg.conf.d"
(II) AIGLX: Suspending AIGLX clients for VT switch
(II) Server terminated successfully (0). Closing log file.