TTY: introduce deinit helpers for proper ldisc shutdown

Introduce deinitialize_tty_struct which should be called after
initialize_tty_struct and before successfull tty_ldisc_setup.

It calls tty_ldisc_deinit which is opposite of tty_ldisc_init. It only
puts a reference to ldisc and assigns NULL to tty->ldisc.

It will be used to shut down ldisc when tty_release cannot be called
yet.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index e19e1364711..5d01d32e2cf 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -956,6 +956,19 @@ void tty_ldisc_init(struct tty_struct *tty)
         tty_ldisc_assign(tty, ld);
 }
 
+/**
+ *      tty_ldisc_init          -       ldisc cleanup for new tty
+ *      @tty: tty that was allocated recently
+ *
+ *      The tty structure must not becompletely set up (tty_ldisc_setup) when
+ *      this call is made.
+ */
+void tty_ldisc_deinit(struct tty_struct *tty)
+{
+        put_ldisc(tty->ldisc);
+        tty_ldisc_assign(tty, NULL);
+}
+
 void tty_ldisc_begin(void)
 {
         /* Setup the default TTY line discipline. */