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#1 2018-11-30 16:03:27

NuncEstBibendum
Member
Registered: 2017-10-13
Posts: 6

Xfwm4 locking up

I have come across a rather insidious and annoying situation in XFCE, and my hope is that someone here may point out how to fix it when it rears its ugly head.

    From my XFCE 4.12 desktop, I sometimes access a remote desktop (also running XFCE 4.12) with the following command:

    ssvnc -cmd -ssh remote-system:0 -passwd $HOME/.vnc/passwd

In essence, this is going to create an SSH tunnel to remote-system, and then connecting through this tunnel to the desktop in the console at remote-system. The -passwd option simply takes a password from $HOME/.vnc/passwd and supplies it to remote-system for VNC authentication. Since the connection is established through an SSH tunnel, this does not really add much; it is there just in case attempts are made to connect to this desktop directly. Not really an option from the external world in my setup, anyway. But, I digress.

    The command above works seamlessly, as long as the connection to remote-system is completed with public key authentication. With password
authentication, one is prompted for the password, at least once, maybe even more than once. Since I do use public key authentication, I created an XFCE launcher in my top panel, so that when I click on it the command above is executed, and I access the desktop at remote-system automagically. Copacetic.

    Here's the problem: if and when, for whatever reason, the ssvnc command above prompts for a password (be it because I forgot to add my private key to my SSH agent, or because remote-system refuses to do public key authentication - both things have happened to me) on clicking on the XFCE launcher, my whole XFCE desktop locks up. Whatever applications I have running in it keep running all right, but the desktop stops accepting input from mouse and keyboard. I can still move the pointer, but any clicks from the mouse are ignored. Applets that I have added to my top panel freeze up - for instance, I have network and CPU activity applets that, under normal circumstances, keep displaying activity as changing bars. When the above happens they just freeze up.

    The one that seems to be locking up is the XFCE windows manager, xfwm4. When I kill it by hand, the desktop becomes unlocked - but, since I do not have a window manager any longer, all of my applications are all jumbled up, one on top of another. At this point, my only solution consists of relaunching X - which, as you can imagine, when I had hundreds of applications running, can be a painful proposition.

    Can anybody suggest a mechanism to recover gracefully from this - i.e. without having to kill xfwm4? I can still access this system e.g. by ssh, so I can manage processes in it. Killing the ssvnc command above by hand won't do anything in this respect. That ssvnc command issues an ssh command to create the tunnel - killing it by hand also does not do anything. The problem is clearly in xfwm4, that gets locked up. I tried a kill -HUP on it, to no avail. A simple kill also does nothing, whereas a kill -9 just kills it for good (for bad, in this case) - it does not get restarted.

    Any ideas to try? I could of course stop using that launcher. However, I would really like to find out how to get xfwm4 to become responsive again.

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#2 2018-11-30 20:52:46

NuncEstBibendum
Member
Registered: 2017-10-13
Posts: 6

Re: Xfwm4 locking up

In case this helps:

From a VT I did xfwm4 --replace --display :0.0 --sm-client-id <client-id>, where <client-id> is obtained from the output of ps awux | egrep xwfm4.  The output from the replace command is the following:

Waiting for current window manager (Xfwm4) on screen :0.0 to exit:................ Failed

(xfwm4:2278): xfwm4-WARNING ***: Previous window manager (Xfwm4) on screen :0.0 is not exiting

(xfwm4:2278): xfwm4-WARNING ***: Could not find a screen to manage, exiting

Can a separate, non-XFCE command really bring the xfwm4 window manager down to its knees so easily and irretrievably?

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#3 2018-12-01 00:56:56

ToZ
Moderator
From: Canada
Registered: 2011-06-02
Posts: 4,832

Re: Xfwm4 locking up

What if you enable the "Run in Terminal" option of the launcher? This way if a password prompt is presented, you'll have an opportunity to type it in and should avoid the hang all together.

ssh also has a "BatchMode" parameter that if set to yes, prevents the password authentication prompt and the command will then silently fail (and not hang the system).

As for xfwm4 hanging, it might be a good idea to create a bug report.

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#4 2018-12-03 14:01:08

NuncEstBibendum
Member
Registered: 2017-10-13
Posts: 6

Re: Xfwm4 locking up

Thanks, that's a useful suggestion. I believe I will create a bug report - xfwm4 shouldn't lock up like that.

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