# Why Mathematica hangs when closing local kernel from the splash screen?

I just discovered something interesting. When closing the kernel from the splash screen, Mathematica hangs.

This is 11.2 running on windows 7 home edition, 64 bit.

These are the steps to reproduce the problem. (1) start mathematica. (2) Click on the new document from the Welcome screen which comes right after M starts. (3). Now close the document just opened using the Close option. (4) This gets you to the splash screen, which should look like this

(5) open the Evaluation menu that shows on the above screen and select Quit kernel -> Local

Now Mathematica hangs. Here is small movie

The task manager shows FE running at full CPU. Only way to recover is to kill the process. I also never see the pop-up message which asks if I really want to kill the local kernel as normally happens. I searched for that pop-up message window and do not see it on the desktop anywhere.

Does this happen to others? This is reproducible for me. I close M many times and get this hangs each time using the above steps. Why does it happen? Is this known issue?

I think what happens is that FE is not able to display the pop-up windows which asks for confirmation of killing the kernel. And that is where it is stuck at.

## Update

I think I discovered something important why it hangs. After doing the steps above, and now the FE is hanged, when I simply moved any other application window over on top of the splash screen to cover it, now the pop-up window asking me if I want to really quit the kernel shows up !

This behavior seems to indicate a dynamic problem. Because with dynamics, when one covers it from display, it goes to sleep also.

Here is a movie showing this. Just blocking the splash screen with any other app on the desktop solves this. You can see once I blocked the splash screen, the pop-up menu shows up ! Now I clicked OK and FE no longer hanged.

• I can't reproduce this in my 11.2 on a similarly configured system. When I quit the kernel as you do, the kernel remains dead and the FE remains operational. Even if I do New Notebook, and then close the notebook to come back to this screen again. One possibility I would consider is that you might have a Dynamic somewhere in a \$FrontEnd option setting that is hitting the kernel. That setting might be inherited by the farewell notebook, perhaps interacting with mouseovers (depending upon the option). – John Fultz Nov 27 '17 at 16:31
• @JohnFultz thanks for looking at it. I can reproduce it all the time. If there is more information you need, will be happy to post it. This my be related to why the WRI CDF player download manager also do not start on my PC. It also hangs. mathematica.stackexchange.com/questions/160718/… I do not know. I can reproduce this from fresh startup. So I have nothing else running. I also DISABLED dynamics, before closing the kernel, and it still hanged ! – Nasser Nov 27 '17 at 16:53
• @Nasser have you modified that notebook in the layout? – ihojnicki Nov 27 '17 at 22:59
• @ihojnicki sorry, I do not understand. Which notebook did I modify? Instructions as given above: Start M. Open new notebook. Close notebook right away. Splash screen comes up. Now close local kernel. It hangs. Each time. These are the 4 steps needed on my PC to make it hangs. I do not modify anything. – Nasser Nov 28 '17 at 1:01
• @Nasser, the dialog that you quit the kernel from. There is a gray bar that is supposed to be on the bottom. What does the option inspector report for the WindowSize for that notebook? – ihojnicki Nov 28 '17 at 12:36