After an upgrade from 2.9.2 to 2.10.2 the site was working normally in the browser, and the system login page accepted credentials. After that was a white screen.
Turning on error logging in admin.php produced the following error:
A Database Error Occurred
Error Number: 1054
Unknown column 'login_state' in 'field list'
Line Number: 731
The database table exp_update_log indicates successful update to v2.10.2