Description of problem:
If you have a root partition protected with LUKS and restart with 'reboot', on next boot you are never prompted to enter your LUKS passphrase and the boot never completes.
Version-Release number of selected component (if applicable):
4.9.6-200.fc25.x86_64 and 4.9.4-201.fc25.x86_64
Steps to Reproduce:
1. log into gnome as a normal user
2. Open gnome-terminal
3. sudo su -
At boot screen the LUKS passphrase prompt is not displayed as it is from a cold poweron. Boot never completes, waits indefinitely
Same behaviour as cold poweron and grub / plymouth displays LUKS passphrase.
I think that's unlikely. There is very little difference between a reboot and a cold boot. Maybe try booting without "quiet rhgb" on the kernel commadn line and enter the password through the text interface.
I've just tested this again on Fedora 25 4.10.10-200-fc25.x86_64 and it correctly prompts for LUKS passphrase at boot time