I had Windows 2012 R2 stuck at reboot with the spinner spinning with the screen pictured in the question. The way I got into this state was I clicked the Reboot/Restart button in Windows Update and then responded “Yes” to the prompt of whether it was OK to restart even though other users were logged in. Then it displayed the “Restarting” screen forever. I think it was confused, it was supposed to show me if I wanted to close my apps first before proceeding but was instead showing the Rebooting screen forever.
I was accessing the server via
mstsc (RDP), so to get out of this situation, I pressed ctrl+alt+end (which is like pressing ctrl+alt+del on the remote computer). This came up with the security options display. I then clicked on “Sign out”. This caused the screen to display “Signing out…” for a few seconds before showing me the prompt of whether or not I wanted to save my files or Restart anyway. I clicked Restart anyway to proceed.
After that, Server signed me out. When I logged back in, I saw that the server uptime was still more than a couple minutes. So I initiated a reboot again and it finally went -_-.