XFCE session lock-up
I am running XFCE 4.12 under Slackware 14.2, with an X session launched with startx -- -listen tcp. I have noticed the following sequence of events:
Add a launcher to one of the panels - e.g the top one.
Right click on the launcher added above and click on Properties.
Configure this launcher so that it will attempt to execute the following command:
where some-command stands for anything - even a nonexistent command will do.
- Fill out the rest of the entries in the launcher creation menu.
- At this point the launcher is present in your panel.
- Click on the launcher above.
Assuming that you have not invoked the sudo command in this session, clicking on the launcher will cause the sudo command to attempt to prompt you for a password. However, because of the way it has been launched, you will never see the prompt. And what is really bad is that your XFCE session locks up. Completely. Nothing works - not only does it not respond to mouse or keyboard events any more but, in addition, the output from any running applications stops being updated - e.g. I have a clock app in the panel, and it just remains frozen at the second when the action described was undertaken. The same happened with the top application that was running in terminal emulator at the time.
Doing a kill -9 on the sudo (from e.g. an SSH shell) won't solve the problem. That is, the sudo process is killed, but the XFCE remains utterly unresponsive. The simplest way out that I found is to kill the X server - which is, of course, a painful way to proceed, especially if your session has been up more than just a few days.
Notice that if the launcher is defined with the Run in terminal option set then a terminal emulator is indeed created, and the prompt can be seen. In this case, the XFCE session won't lock up.
I used the sudo command to illustrate the problem in the simplest way. The fact is, any command executed by the launcher which attempts to prompt the user for input in the same way as sudo does will have the same effect.