emacs-lock-unlockable-modes is a variable defined in `emacs-lock.el'.
Its value is
((shell-mode . all) (telnet-mode . all))

Alist of auto-unlockable modes.
Each element is a pair (MAJOR-MODE . ACTION), where ACTION is
one of `kill', `exit' or `all'. Buffers with matching major
modes are auto-unlocked for the specific action if their
inferior processes are not alive. If this variable is t, all
buffers associated to inferior processes are auto-unlockable
for both actions (NOT RECOMMENDED).

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.