Once the screen was locked, it arbitrarily blanks on any screen update

tuxolero · 2016-06-18 10:35:05

I'm sometimes encountering a problem after this situation:

Screen was locked, either manually or timer-based
unlocking failed, either by typo or timeout
unlocking succeeds in next try

Especially when the screen locks timer-based, there always occurs a "PAM timeout".

Sometimes, after unlocking, the computer becomes nearly unusable. On focus change or even the blinking of the cursor in a text editor like geany, the screen blanks and I see a mix of the lockscreen (including the unlock dialog and the PAM timeout message) and some remainders of the last screen content before the last locking.

It sems to depend which applications are open, of if I'm on the same virtual desktop as I was when the screen locked last time. It even depends on the Z-order of the application windows.

Once it occurs, only a reboot helps. Logging off from XFCE and back on is not sufficient. The problem is: I often have long-running jobs in background that I can not stop and resume after reboot.

I'm really desperate about this problem. Am I the only one ?

Thanks,
tuxolero

ToZ · 2016-06-18 21:35:01

Which screensaver/screen locker program are you using? Have you tried another to rule out the locker?

Also, which video card and driver are you using?

What do you mean by?

It sems to depend which applications are open, of if I'm on the same virtual desktop as I was when the screen locked last time. It even depends on the Z-order of the application windows.

tuxolero · 2016-06-21 07:21:34

I'm using XScreenSaver 5.34. And in "XFCE Settings" -> "Screensaver", I have selected "Blank Screen only" and "Lock after 30 minutes".

My video card is an AMD Radeon HD 5400 with the open source driver. If it matters, I have two screens attached.

It means that it happens e.g. when geany (the text editor) is in forground, but when firefox is in foreground, it stops for a while, until I switch back to geany. Looks like it's because geany has the blinking cursor, while firefox does not.
Sometimes, when I switch to another virtual desktop, it also stops for a while. Even when I move geany to that other desktop.

But it's always "sometimes", not 100% reproducible.

ToZ · 2016-06-21 11:11:20

It sounds like a video card/driver issue. When it does happen next time , check your Xorg.0.log file to see if anything is logged. Also check your system log files.

Also, does it happen if geany is not running?

tuxolero · 2016-06-21 16:02:01

OK, I'll check the logs next time. If so, it looks mor like a driver issue, because I have this video card since 2 or 3 years now and the issue is relatively new.

geany is just one of the applications that can trigger it because of the blinking cursor. But it can also happen when the browser shows a website with animations. Or when I switch focus between windows, but this happens rarely.

But I want to repeat that all of the problems only occur after the screensaver was activated and unlock failed. After reboot, everything is fine until the next time unlocking the screensaver fails. Unfortunately, it can also fail from a PAM timeout, not only from a typo in the password.

ToZ · 2016-06-21 17:10:34

because I have this video card since 2 or 3 years now and the issue is relatively new.

True, but both the video driver and the version of X update regularly. Perhaps an incompatibility was introduced through one of the updates?

But I want to repeat that all of the problems only occur after the screensaver was activated and unlock failed.

Have you tried another screensaver/screen locker program to rule out xscreensaver as the culprit? Maybe light-locker or gnome-screensaver?

tuxolero · 2016-06-21 22:28:12

ToZ wrote:

because I have this video card since 2 or 3 years now and the issue is relatively new.
True, but both the video driver and the version of X update regularly. Perhaps an incompatibility was introduced through one of the updates?

Yes, an incompatible change could be possible.

ToZ wrote:

But I want to repeat that all of the problems only occur after the screensaver was activated and unlock failed.
Have you tried another screensaver/screen locker program to rule out xscreensaver as the culprit? Maybe light-locker or gnome-screensaver?

Not yet ... how do I configure the screensaver for XFCE ?

What I mean by that is ... in the screensaver settings dialog, there is no such thing as a program to choose. And when I manually lock the screen, I use xflock (from Menu -> System -> Lock Screen). There must be a place where xflock knows that it should use xscreensaver (or something else)

ToZ · 2016-06-22 01:07:11

Screensavers are executed via the /usr/bin/xflock4 script file. It depends on which version of the file you have, but you can view the logic by viewing the file. In the case of the version installed on my computer:

# First test for the command set in the session's xfconf channel
LOCK_CMD=$(xfconf-query -c xfce4-session -p /general/LockCommand)

# Lock by xscreensaver or gnome-screensaver, if a respective daemon is running
for lock_cmd in \
    "$LOCK_CMD" \
    "xscreensaver-command -lock" \
    "gnome-screensaver-command --lock"
do
    if [ ! -z "$lock_cmd" ]; then
        $lock_cmd >/dev/null 2>&1 && exit
    fi
done

# else run another access locking utility, if installed
for lock_cmd in \
  "xlock -mode blank" \
  "slock"
  do
    set -- $lock_cmd
    if command -v -- $1 >/dev/null 2>&1; then
        $lock_cmd >/dev/null 2>&1 &
	# turn off display backlight:
	xset dpms force off
        exit
    fi
done

The version on my system allows the use of xfce4-session's /general/LockCommand xfconf property to specify which screen locker to use. Then it will try xscreensaver, then gnome-screensaver, etc.

If your file contains the /general/LockCommand option, then create that xfconf key and specify the executable of the screensaver you want to use. Otherwise, simply uninstall xscreensaver and install another screensaver (e.g. gnome-screensaver) and it will be used.

tuxolero · 2016-06-22 21:24:01

Today, it happened again. And there was no log, neither in Xorg.0.log nor in syslog. But I found a workaround to stop it, at least for now:
Switching to text mode (Ctl-Alt-F2) and back to graphics mode.

I will test the xscreensaver alternatives next week.

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Sub domains

#1 2016-06-18 10:35:05

Once the screen was locked, it arbitrarily blanks on any screen update

#2 2016-06-18 21:35:01

Re: Once the screen was locked, it arbitrarily blanks on any screen update

#3 2016-06-21 07:21:34

Re: Once the screen was locked, it arbitrarily blanks on any screen update

#4 2016-06-21 11:11:20

Re: Once the screen was locked, it arbitrarily blanks on any screen update

#5 2016-06-21 16:02:01

Re: Once the screen was locked, it arbitrarily blanks on any screen update

#6 2016-06-21 17:10:34

Re: Once the screen was locked, it arbitrarily blanks on any screen update

#7 2016-06-21 22:28:12

Re: Once the screen was locked, it arbitrarily blanks on any screen update

#8 2016-06-22 01:07:11

Re: Once the screen was locked, it arbitrarily blanks on any screen update

#9 2016-06-22 21:24:01

Re: Once the screen was locked, it arbitrarily blanks on any screen update

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