Windows 10 prompted me to restart to install the Creators Update. It's now been sitting for a little over an hour on "Getting Windows ready. Don't turn off your computer". I can still move the mouse around and the dots are still spinning, but there's no activity on the disk.

I'm not sure what my options are at this point. I'm almost 100% sure it's frozen, so I may be in the position to turn it off with the power button, but I don't want to lose everything. Any suggestions?

EDIT: about 30 seconds after posting this, it restarted on its own. It's now on the "Working on updates... this will take a while" screen, so all seems good. I'm still not sure why it was so slow, but maybe it has something to do with my OS drive (SSD) being nearly full, so it might have had to write and install small chunks of the update at a time if it didn't have enough space.