KVM (keyboard,video,mouse) switch messing up gdm

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iwishitwouldwork
Posts: 80
Joined: 2014/02/08 14:56:39

KVM (keyboard,video,mouse) switch messing up gdm

Post by iwishitwouldwork » 2021/04/21 21:59:11

centos 8
fully patched. This problem has persisted through several sets of patches.
ATEN CS 1798 KVM switch
and... you guessed it, the problem is intermittent.

I have a couple of centos 8 machines running through an ATEN KVM (keyboard,video,mouse) switch. One runs the gnome GUI but the other (file server) does not even have the GUI installed. This worked for years, going back to centos 7 at least. But now, if I leave
the GUI machine logged in, the gnome-session gdm-x-session goes insane. There are many, many messages (over 1500), in the interest of bandwidth I'm leaving them out.

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Apr 21 16:25:29 ws /usr/libexec/gdm-x-session[403840]: (**) Option "fd" "24"
Apr 21 16:25:29 ws /usr/libexec/gdm-x-session[403840]: (II) event2  - Power Button: device removed
Apr 21 16:25:29 ws /usr/libexec/gdm-x-session[403840]: (**) Option "fd" "27"
Apr 21 16:25:29 ws /usr/libexec/gdm-x-session[403840]: (II) event1  - Power Button: device removed
Apr 21 16:25:29 ws /usr/libexec/gdm-x-session[403840]: (**) Option "fd" "28"
Apr 21 16:25:29 ws /usr/libexec/gdm-x-session[403840]: (II) event0  - Sleep Button: device removed
Apr 21 16:25:29 ws /usr/libexec/gdm-x-session[403840]: (**) Option "fd" "29"
Apr 21 16:25:29 ws /usr/libexec/gdm-x-session[403840]: (II) event3  - ATEN: device removed
Apr 21 16:25:29 ws /usr/libexec/gdm-x-session[403840]: (**) Option "fd" "30"
Apr 21 16:25:29 ws /usr/libexec/gdm-x-session[403840]: (II) event4  - ATEN: device removed
Apr 21 16:25:29 ws /usr/libexec/gdm-x-session[403840]: (II) UnloadModule: "libinput"
Now, the above looks like I did a deliberate switch, but I didn't. I was at my desk but if I touched the keyboard at all it was inadvertent. Certainly I did not touch the KVM switch. When I try to get the computer to respond, the screen flickers on for a second and I can just see the last screen that was there -- that is, the display looks proper, the correct windows are open, etc. There is a brief bit of static from the speakers at the same time.

I'm wondering if there is a way to deliberately have the computer insist that the monitor re-identify itself. I have tried restarting the gdm.service and sometimes that works. I'm wondering about the EDID, the extended display identification data. I've been worried about the EDID being correct before. the Xorg.0.log is likewise huge. There may be a huge red flag in there but I don't recognize it.

The tail end of the log file has a bunch of "modeset" lines in it. I'm guessing this is when the stuff decides to play nice again. I tried doing

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tail -f /var/log/messages
while the stuff was messed up, and watching it through several "buzz" cycles. But nothing shows up in the log file. Is this a hardware problem? Possibly with the KVM?

iwishitwouldwork
Posts: 80
Joined: 2014/02/08 14:56:39

[SOLVED] Re: KVM (keyboard,video,mouse) switch messing up gdm --SOLVED

Post by iwishitwouldwork » 2021/05/06 10:56:39

After a lot of confusion, it was a hardware problem with the monitor.
So, nothing to do with Centos/linux/software at all.

No changes. I'm just trying to figure out how to mark the problem as solved.

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