Comment # 26 on bug 966255 from Fabian Vogt

(In reply to Jacob W from comment #25)
> Created attachment 667207 [details]
> cryptsetup boot password prompt goes into background as a job

That's not the plymouth prompt, so a totally different issue.
It didn't even try to use plymouth for password asking.

> Password prompt is not shown and plymouth theme never shows up, instead it freezes the system where VT switching does not work.

If even the cursor stops blinking, the kernel either froze or panics -> kernel
bug.
To confirm, run on a booted system as root on a TTY:

> rcxdm stop
> plymouthd --no-daemon --no-boot-log --tty=/dev/tty0 --debug --mode=boot

and on a different tty also as root

> plymouth show-splash

and you should the the splash screen (on TTY7).

> Forcing the system to boot without plymouth (press e on grub's kernel list) shows what looks like cryptsetup trying to prompt for the password, but instead instantly being backgrounded as a job. After more processes go through their boot procedure, the boot process stops and looks frozen. If I press a button on the keyboard, it forces the password prompt to re-appear. Now I can enter my password and everything works from there.

It's not backgrounded, it's the current TTY so systemd uses it, although it's
also being used by something else... -> systemd bug(?)