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>

3 files changed, 29 insertions, 0 deletions

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 026bf2f6f5f2..f5dd23520fe3 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2887,6 +2887,20 @@ void initialize_tty_struct(struct tty_struct *tty,
 }
 
 /**
+ *      deinitialize_tty_struct
+ *      @tty: tty to deinitialize
+ *
+ *      This subroutine deinitializes a tty structure that has been newly
+ *      allocated but tty_release cannot be called on that yet.
+ *
+ *      Locking: none - tty in question must not be exposed at this point
+ */
+void deinitialize_tty_struct(struct tty_struct *tty)
+{
+        tty_ldisc_deinit(tty);
+}
+
+/**
  *      tty_put_char    -       write one character to a tty
  *      @tty: tty
  *      @ch: character
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index e19e13647116..5d01d32e2cf0 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. */
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 9f469c700550..4db4ca79f895 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -472,6 +472,7 @@ extern int tty_add_file(struct tty_struct *tty, struct file *file);
 extern void free_tty_struct(struct tty_struct *tty);
 extern void initialize_tty_struct(struct tty_struct *tty,
                 struct tty_driver *driver, int idx);
+extern void deinitialize_tty_struct(struct tty_struct *tty);
 extern struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,
                                                                 int first_ok);
 extern int tty_release(struct inode *inode, struct file *filp);
@@ -525,6 +526,7 @@ extern int tty_set_ldisc(struct tty_struct *tty, int ldisc);
 extern int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty);
 extern void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty);
 extern void tty_ldisc_init(struct tty_struct *tty);
+extern void tty_ldisc_deinit(struct tty_struct *tty);
 extern void tty_ldisc_begin(void);
 /* This last one is just for the tty layer internals and shouldn't be used elsewhere */
 extern void tty_ldisc_enable(struct tty_struct *tty);