TTY: switch tty_flip_buffer_push

Now, we start converting tty buffer functions to actually use
tty_port. This will allow us to get rid of the need of tty in many
call sites. Only tty_port will needed and hence no more
tty_port_tty_get in those paths.

Now, the one where most of tty_port_tty_get gets removed:
tty_flip_buffer_push.

IOW we also closed all the races in drivers not using tty_port_tty_get
at all yet.

Also we move tty_flip_buffer_push declaration from include/linux/tty.h
to include/linux/tty_flip.h to all others while we are changing it
anyway.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/um/drivers/chan.h

@@ -27,8 +27,7 @@ struct chan {
 	void *data;
 };
 
-extern void chan_interrupt(struct line *line,
-			   struct tty_struct *tty, int irq);
+extern void chan_interrupt(struct line *line, int irq);
 extern int parse_chan_pair(char *str, struct line *line, int device,
 			   const struct chan_opts *opts, char **error_out);
 extern int write_chan(struct chan *chan, const char *buf, int len,

arch/um/drivers/chan_kern.c

@@ -131,11 +131,9 @@ void chan_enable_winch(struct chan *chan, struct tty_struct *tty)
 static void line_timer_cb(struct work_struct *work)
 {
 	struct line *line = container_of(work, struct line, task.work);
-	struct tty_struct *tty = tty_port_tty_get(&line->port);
 
 	if (!line->throttled)
-		chan_interrupt(line, tty, line->driver->read_irq);
-	tty_kref_put(tty);
+		chan_interrupt(line, line->driver->read_irq);
 }
 
 int enable_chan(struct line *line)
@@ -546,7 +544,7 @@ int parse_chan_pair(char *str, struct line *line, int device,
 	return 0;
 }
 
-void chan_interrupt(struct line *line, struct tty_struct *tty, int irq)
+void chan_interrupt(struct line *line, int irq)
 {
 	struct tty_port *port = &line->port;
 	struct chan *chan = line->chan_in;
@@ -570,8 +568,11 @@ void chan_interrupt(struct line *line, struct tty_struct *tty, int irq)
 		reactivate_fd(chan->fd, irq);
 	if (err == -EIO) {
 		if (chan->primary) {
-			if (tty != NULL)
+			struct tty_struct *tty = tty_port_tty_get(&line->port);
+			if (tty != NULL) {
 				tty_hangup(tty);
+				tty_kref_put(tty);
+			}
 			if (line->chan_out != chan)
 				close_one_chan(line->chan_out, 1);
 		}
@@ -580,6 +581,5 @@ void chan_interrupt(struct line *line, struct tty_struct *tty, int irq)
 			return;
 	}
  out:
-	if (tty)
-		tty_flip_buffer_push(tty);
+	tty_flip_buffer_push(port);
 }

arch/um/drivers/line.c

@@ -19,11 +19,10 @@ static irqreturn_t line_interrupt(int irq, void *data)
 {
 	struct chan *chan = data;
 	struct line *line = chan->line;
-	struct tty_struct *tty = tty_port_tty_get(&line->port);
 
 	if (line)
-		chan_interrupt(line, tty, irq);
-	tty_kref_put(tty);
+		chan_interrupt(line, irq);
+
 	return IRQ_HANDLED;
 }
 
@@ -234,7 +233,7 @@ void line_unthrottle(struct tty_struct *tty)
 	struct line *line = tty->driver_data;
 
 	line->throttled = 0;
-	chan_interrupt(line, tty, line->driver->read_irq);
+	chan_interrupt(line, line->driver->read_irq);
 
 	/*
 	 * Maybe there is enough stuff pending that calling the interrupt