backdrop_session_commit in core/includes/session.inc

Commits the current session, if necessary.

backdrop_session_initialize in core/includes/session.inc

Initializes the session handler, starting a session if needed.

backdrop_session_regenerate in core/includes/session.inc

Called when an anonymous user becomes authenticated or vice-versa.

drupal_session_start in core/includes/drupal.inc

Starts a session forcefully, preserving already set session data.

update.php in core/update.php

Administrative page for handling updates from one Backdrop version to another.

_backdrop_session_regenerate_existing in core/includes/session.inc

Regenerates an existing session.