tty: Add a kref count

Introduce a kref to the tty structure and use it to protect the tty->signal
tty references. For now we don't introduce it for anything else.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/linux/tty.h b/include/linux/tty.h
index e3612c3ac19..b6e6c26883e 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -209,6 +209,7 @@ struct tty_operations;
 
 struct tty_struct {
 	int	magic;
+	struct kref kref;
 	struct tty_driver *driver;
 	const struct tty_operations *ops;
 	int index;
@@ -311,6 +312,23 @@ extern int kmsg_redirect;
 extern void console_init(void);
 extern int vcs_init(void);
 
+/**
+ *	tty_kref_get		-	get a tty reference
+ *	@tty: tty device
+ *
+ *	Return a new reference to a tty object. The caller must hold
+ *	sufficient locks/counts to ensure that their existing reference cannot
+ *	go away
+ */
+
+extern inline struct tty_struct *tty_kref_get(struct tty_struct *tty)
+{
+	if (tty)
+		kref_get(&tty->kref);
+	return tty;
+}
+extern void tty_kref_put(struct tty_struct *tty);
+
 extern int tty_paranoia_check(struct tty_struct *tty, struct inode *inode,
 			      const char *routine);
 extern char *tty_name(struct tty_struct *tty, char *buf);