tty: n_tty: simplify process_output()

Using guard(mutex), the function can be written in a much more efficient
way.

Signed-off-by: Jiri Slaby (SUSE) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Jiri Slaby (SUSE)

drivers/tty/n_tty.c

@@ -488,19 +488,13 @@ static int do_output_char(u8 c, struct tty_struct *tty, int space)
 static int process_output(u8 c, struct tty_struct *tty)
 {
 	struct n_tty_data *ldata = tty->disc_data;
-	unsigned int space;
-	int retval;
 
-	mutex_lock(&ldata->output_lock);
+	guard(mutex)(&ldata->output_lock);
 
-	space = tty_write_room(tty);
-	retval = do_output_char(c, tty, space);
-
-	mutex_unlock(&ldata->output_lock);
-	if (retval < 0)
+	if (do_output_char(c, tty, tty_write_room(tty)) < 0)
 		return -1;
-	else
-		return 0;
+
+	return 0;
 }
 
 /**