Toggle Emacs Lock mode in the current buffer.
If called with a plain prefix argument, ask for the locking mode
to be used. With any other prefix ARG, turn mode on if ARG is
positive, off otherwise. If called from Lisp, enable the mode if
ARG is omitted or nil.
Initially, if the user does not pass an explicit locking mode, it
defaults to `emacs-lock-default-locking-mode' (which see);
afterwards, the locking mode most recently set on the buffer is
When called from Elisp code, ARG can be any locking mode:
exit -- Emacs cannot exit while the buffer is locked
kill -- the buffer cannot be killed, but Emacs can exit as usual
all -- the buffer is locked against both actions Other values are interpreted as usual. (fn &optional ARG)