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l3u

Member

Registered: 2022-07-10

Posts: 63  

Dozens of lxqt-config-monitor processes are started

Hi all :-)

I have LxQt running.

As soon as the energy management turns off the monitor, a lot of "lxqt-config-monitor -l" processes are started. Maybe, the process keeps crashing and is started over and over again. At the time I saw it, the system was up several weeks, and I had > 200 such processes:

 $ ps -ef | grep lxqt-config-monitor
...
serverh+ 19102  3339  0 16:30 ?        00:00:00 /usr/bin/lxqt-config-monitor -l
serverh+ 19112  3339  0 16:30 ?        00:00:00 /usr/bin/lxqt-config-monitor -l
serverh+ 19122  3339  0 16:30 ?        00:00:00 /usr/bin/lxqt-config-monitor -l
serverh+ 19132  3339  0 16:30 ?        00:00:00 /usr/bin/lxqt-config-monitor -l
serverh+ 19143  3339  0 16:30 ?        00:00:00 /usr/bin/lxqt-config-monitor -l
serverh+ 19153  3339  0 16:30 ?        00:00:00 /usr/bin/lxqt-config-monitor -l
serverh+ 19163  3339  0 16:31 ?        00:00:00 /usr/bin/lxqt-config-monitor -l
serverh+ 19173  3339  0 16:31 ?        00:00:00 /usr/bin/lxqt-config-monitor -l
serverh+ 19183  3339  0 16:31 ?        00:00:00 /usr/bin/lxqt-config-monitor -l
serverh+ 19193  3339  0 16:31 ?        00:00:00 /usr/bin/lxqt-config-monitor -l
...

Playing around a bit, I saw that at the exact moment the energy management turns off the monitor, a few such processes appear.

I also played around with the xscreensaver settings. This seems to change nothing. Also, I never changed any screen setting. Running "lxqt-config-monitor -l" manually doesn't crash and returns normally.

As soon as the monitor is turned off, the following appears over and over again in ~/.xsession-errors (it was > 300 MB big at the time I noticed this):

lxqt-session: "Session 'session': display device '/dev/dri/card0'"
[load.applyBestSettings()] Finished
qt.qpa.xcb: QXcbConnection: XCB error: 148 (Unknown), sequence: 190, resource id: 0, major code: 140 (Unknown), minor code: 20
lxqt-session: "Session 'session': display device '/dev/dri/card0'"
[load.applyBestSettings()] Finished
lxqt-config-monitor: Applying current settings...
Output:  "DP-1"
Output:  "HDMI-1"
Output:  "DP-2"
Output:  "HDMI-2"
lxqt-config-monitor: Settings applied.

What may cause this? And how can I prevent it other than turning off the energy management?

Thanks for all help!

Last edited by l3u (2023-12-12 16:40:26)

stopAI

Member

Registered: 2023-04-04

Posts: 186  

Re: Dozens of lxqt-config-monitor processes are started

Hello.

What if you try to disable lxqt power monitoring and switch it to xscreensaver?

l3u

Member

Registered: 2022-07-10

Posts: 63  

Re: Dozens of lxqt-config-monitor processes are started

Okay, I just saw that xscreensaver also seems to have the ability to turn off the monitor. I'll try to enable this and to disable the energy management … however, this is definitely not expected behavior, is it?!

Last edited by l3u (2023-12-12 17:27:30)

fsmithred

Administrator

Registered: 2016-11-25

Posts: 2,486  

Re: Dozens of lxqt-config-monitor processes are started

I don't think it's normal behavior, but I'm not sure. My lxqt is minimal. I can't tell you off the top of my head which parts I left out, but I do have lxqt-powermanagement and lxqt-config-monitor. I do not have xscreensaver installed. I'm using openbox as the window manager.

lxqt-powermanagement is running. Watching top in an ssh session from another machine, I did not see lxqt-config-monitor run when the screen blanked. Screen blanking is set in the power manager settings. Nothing shows up in ~/.xsession-errors when the screen goes blank or when it comes back on.

Here's what I have installed with lxqt in the package name. Let me know if you think of something else you want me to check.

ii  liblxqt-globalkeys-ui1:i386        1.2.0-1                                i386         daemon used to register global keyboard shortcuts (ui files)
ii  liblxqt-globalkeys1:i386           1.2.0-1                                i386         daemon used to register global keyboard shortcuts (shared libs)
ii  liblxqt1:i386                      1.2.0-8                                i386         Shared libraries for LXQt desktop environment (libs)
ii  lxqt-config                        1.2.0-1+b1                             i386         LXQt system settings center
ii  lxqt-globalkeys                    1.2.0-1                                i386         daemon used to register global keyboard shortcuts (appl.)
ii  lxqt-notificationd                 1.2.0-1                                i386         LXQt notification daemon
ii  lxqt-panel                         1.2.1-1                                i386         LXQt desktop panel
ii  lxqt-policykit                     1.2.0-1                                i386         LXQt authentication agent for PolicyKit
ii  lxqt-powermanagement               1.2.0-1                                i386         power management module for LXQt
ii  lxqt-qtplugin:i386                 1.2.0-3+b2                             i386         LXQt system integration plugin for Qt
ii  lxqt-session                       1.2.0-3                                i386         session manager component for LXQt
ii  lxqt-system-theme                  1.2.0-1                                all          System theme for LXQt
ii  lxqt-themes                        1.2.0-1                                all          Themes for LXQt

l3u

Member

Registered: 2022-07-10

Posts: 63  

Re: Dozens of lxqt-config-monitor processes are started

I'm pretty sure that producing hundreds of zombie processes spamming a logfile with hundreds of megabytes in error messages would not be considered expected behavior ;-)

I won't have physical access to the machine in question until tomorrow, so I played around with another one also running LxQt.

There, the monitor can be turned off both using the energy management and xscreensaver. In neither case, such zombie processes appear.

What is a bit odd is that lxqt-config-monitor isn't even started … I wrote a small wrapper script that writes "lxqt-config-monitor started" to syslog and then actually starts it … neither when the monitor goes off, nor when it goes on again, lxqt-config-monitor is run.

So … what does even start it on the other machine?!

Last edited by l3u (2023-12-13 05:17:17)

l3u

Member

Registered: 2022-07-10

Posts: 63  

Re: Dozens of lxqt-config-monitor processes are started

Okay, just tried it.

It doesn't matter if the energy management turns off the monitor, or if xscreensaver does it. In both cases, the zombie processes appear.

I now tried to work around it by moving lxqt-config-monitor to lxqt-config-monitor~ and adding a fake script named lxqt-config-monitor that does nothing but logging that something wanted to run lxqt-config-monitor.

Interestingly, this also doesn't fix the problem: Now, the script becomes the zombie process. So apparently, lxqt-config-monitor itself isn't even the problem!

On my other machine I played around with yesterday evening, lxqt-config-monitor wasn't even started when the monitor was turned off. So why does this even happen, and what is starting lxqt-config-monitor?! Seems like the problem is there …

l3u

Member

Registered: 2022-07-10

Posts: 63  

Re: Dozens of lxqt-config-monitor processes are started

Even if I turn off my monitor manually, I get one "/usr/bin/lxqt-config-monitor -l" zombie process!!!

Is there a way to find out what trigger this?! There must be some daemon running this command!

delgado

Member

Registered: 2022-07-14

Posts: 213  

Re: Dozens of lxqt-config-monitor processes are started

maybe

$ pstree

gives a hint?

l3u

Member

Registered: 2022-07-10

Posts: 63  

Re: Dozens of lxqt-config-monitor processes are started

Searching for some answer, I also posted this on the LxQt "forum": https://github.com/lxqt/lxqt/discussions/2489

Apparently, this is a Debian issue, as one user answering pointed me to this here: https://github.com/lxqt/lxqt/discussions/2489
which looks exactly like the problem I'm seeing.

I use the machine only to host a QEMU virtual machine which provides the actual server, so I never ran into that "Maximum number of clients reached" problem, because it doesn't affect already opened windows and I normally don't open new ones.

Well, maybe, swapping monitor hardware may fix it as the poster of the mentioned issue states … but anyway, this should not happen! Where would I report this? I think this definitely has to be fixed upstream!

chris2be8

Member

Registered: 2018-08-11

Posts: 307  

Re: Dozens of lxqt-config-monitor processes are started

zombie processes are processes that have been terminated, but not reaped by their parent. So look at the PPID (3339 in the first post) with ps -fp 3339 (replace 3339 which whatever the current PPID is). That should tell you what started them, which is probably where the bug is.

See man ps and search for zombie for details.

l3u

Member

Registered: 2022-07-10

Posts: 63  

Re: Dozens of lxqt-config-monitor processes are started

One of the maintainers guessworks that this could be caused by some broken Debian Bookworm package: https://github.com/lxqt/lxqt/discussion … nt-7844956

Still, I have no idea how to debug this … I'll check for the parent as soon as I see the next lost process.

Last edited by l3u (2023-12-13 18:30:40)

l3u

Member

Registered: 2022-07-10

Posts: 63  

Re: Dozens of lxqt-config-monitor processes are started

Here we are! Simply switching the monitor off (physically) spawns an lxqt-config-monitor zombie process:

$ ps -ef | grep lxqt-config-monitor
serverh+ 26115  3339  0 09:12 ?        00:00:00 /usr/bin/lxqt-config-monitor -l
serverh+ 26121 26106  0 09:12 pts/1    00:00:00 grep lxqt-config-monitor

And here's who does it:

$ ps -fp 3339
UID        PID  PPID  C STIME TTY          TIME CMD
serverh+  3339  3333  0 Nov22 ?        00:25:52 lxqt-session

chris2be8

Member

Registered: 2018-08-11

Posts: 307  

Re: Dozens of lxqt-config-monitor processes are started

Post that to the github discussion. It might point then towards the bug. (Sorry if you'e already done that).

l3u

Member

Registered: 2022-07-10

Posts: 63  

Re: Dozens of lxqt-config-monitor processes are started

Done: https://github.com/lxqt/lxqt/discussion … nt-7863853

Last edited by l3u (2023-12-15 12:52:33)

chris2be8

Member

Registered: 2018-08-11

Posts: 307  

Re: Dozens of lxqt-config-monitor processes are started

Good. I hope that gets a response, I've reached the limit of my debugging skills in this area.