tty: Move the handling of the tty release logic

Now that we don't have tty->termios tied to drivers->tty we can untangle
the logic here. In addition we can push the removal logic out of the
destructor path.

At that point we can think about sorting out tty_port and console and all
the other ugly hangovers.
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/pty.c

@@ -527,12 +527,6 @@ static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 	return tty;
 }
 
-static void pty_unix98_shutdown(struct tty_struct *tty)
-{
-	tty_driver_remove_tty(tty->driver, tty);
-	/* We have our own method as we don't use the tty index */
-}
-
 /* We have no need to install and remove our tty objects as devpts does all
    the work for us */
 
@@ -558,9 +552,8 @@ static const struct tty_operations ptm_unix98_ops = {
 	.unthrottle = pty_unthrottle,
 	.set_termios = pty_set_termios,
 	.ioctl = pty_unix98_ioctl,
-	.shutdown = pty_unix98_shutdown,
-	.cleanup = pty_cleanup,
-	.resize = pty_resize
+	.resize = pty_resize,
+	.cleanup = pty_cleanup
 };
 
 static const struct tty_operations pty_unix98_ops = {
@@ -575,7 +568,6 @@ static const struct tty_operations pty_unix98_ops = {
 	.chars_in_buffer = pty_chars_in_buffer,
 	.unthrottle = pty_unthrottle,
 	.set_termios = pty_set_termios,
-	.shutdown = pty_unix98_shutdown,
 	.cleanup = pty_cleanup,
 };
 

drivers/tty/tty_io.c

@@ -1249,16 +1249,16 @@ int tty_init_termios(struct tty_struct *tty)
 	struct ktermios *tp;
 	int idx = tty->index;
 
-	tp = tty->driver->termios[idx];
-	if (tp == NULL) {
-		tp = kmalloc(sizeof(struct ktermios), GFP_KERNEL);
-		if (tp == NULL)
-			return -ENOMEM;
-		*tp = tty->driver->init_termios;
-		tty->driver->termios[idx] = tp;
+	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
+		tty->termios = tty->driver->init_termios;
+	else {
+		/* Check for lazy saved data */
+		tp = tty->driver->termios[idx];
+		if (tp != NULL)
+			tty->termios = *tp;
+		else
+			tty->termios = tty->driver->init_termios;
 	}
-	tty->termios = *tp;
-
 	/* Compatibility until drivers always set this */
 	tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios);
 	tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios);
@@ -1437,24 +1437,24 @@ void tty_free_termios(struct tty_struct *tty)
 {
 	struct ktermios *tp;
 	int idx = tty->index;
-	/* Kill this flag and push into drivers for locking etc */
-	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) {
-		/* FIXME: Locking on ->termios array */
-		tp = tty->driver->termios[idx];
-		tty->driver->termios[idx] = NULL;
-		kfree(tp);
+
+	/* If the port is going to reset then it has no termios to save */
+	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
+		return;
+
+	/* Stash the termios data */
+	tp = tty->driver->termios[idx];
+	if (tp == NULL) {
+		tp = kmalloc(sizeof(struct ktermios), GFP_KERNEL);
+		if (tp == NULL) {
+			pr_warn("tty: no memory to save termios state.\n");
+			return;
+		}
 	}
-	else
-		*tty->driver->termios[idx] = tty->termios;
+	*tp = tty->termios;
 }
 EXPORT_SYMBOL(tty_free_termios);
 
-void tty_shutdown(struct tty_struct *tty)
-{
-	tty_driver_remove_tty(tty->driver, tty);
-	tty_free_termios(tty);
-}
-EXPORT_SYMBOL(tty_shutdown);
 
 /**
  *	release_one_tty		-	release tty structure memory
@@ -1498,11 +1498,6 @@ static void queue_release_one_tty(struct kref *kref)
 {
 	struct tty_struct *tty = container_of(kref, struct tty_struct, kref);
 
-	if (tty->ops->shutdown)
-		tty->ops->shutdown(tty);
-	else
-		tty_shutdown(tty);
-
 	/* The hangup queue is now free so we can reuse it rather than
 	   waste a chunk of memory for each port */
 	INIT_WORK(&tty->hangup_work, release_one_tty);
@@ -1542,6 +1537,11 @@ static void release_tty(struct tty_struct *tty, int idx)
 	/* This should always be true but check for the moment */
 	WARN_ON(tty->index != idx);
 
+	if (tty->ops->shutdown)
+		tty->ops->shutdown(tty);
+	tty_free_termios(tty);
+	tty_driver_remove_tty(tty->driver, tty);
+
 	if (tty->link)
 		tty_kref_put(tty->link);
 	tty_kref_put(tty);

drivers/tty/vt/vt.c

@@ -2850,7 +2850,6 @@ static void con_shutdown(struct tty_struct *tty)
 	console_lock();
 	vc->port.tty = NULL;
 	console_unlock();
-	tty_shutdown(tty);
 }
 
 static int default_italic_color    = 2; // green (ASCII)

drivers/usb/serial/usb-serial.c

@@ -305,8 +305,7 @@ static void serial_close(struct tty_struct *tty, struct file *filp)
  * Do the resource freeing and refcount dropping for the port.
  * Avoid freeing the console.
  *
- * Called asynchronously after the last tty kref is dropped,
- * and the tty layer has already done the tty_shutdown(tty);
+ * Called asynchronously after the last tty kref is dropped.
  */
 static void serial_cleanup(struct tty_struct *tty)
 {

include/linux/tty.h

@@ -423,7 +423,6 @@ extern void tty_unthrottle(struct tty_struct *tty);
 extern int tty_do_resize(struct tty_struct *tty, struct winsize *ws);
 extern void tty_driver_remove_tty(struct tty_driver *driver,
 				  struct tty_struct *tty);
-extern void tty_shutdown(struct tty_struct *tty);
 extern void tty_free_termios(struct tty_struct *tty);
 extern int is_current_pgrp_orphaned(void);
 extern struct pid *tty_get_pgrp(struct tty_struct *tty);

include/linux/tty_driver.h

@@ -45,14 +45,9 @@
  *
  * void (*shutdown)(struct tty_struct * tty);
  *
- * 	This routine is called synchronously when a particular tty device
- *	is closed for the last time freeing up the resources.
- *	Note that tty_shutdown() is not called if ops->shutdown is defined.
- *	This means one is responsible to take care of calling ops->remove (e.g.
- *	via tty_driver_remove_tty) and releasing tty->termios.
- *	Note that this hook may be called from *all* the contexts where one
- *	uses tty refcounting (e.g. tty_port_tty_get).
- *
+ * 	This routine is called under the tty lock when a particular tty device
+ *	is closed for the last time. It executes before the tty resources
+ *	are freed so may execute while another function holds a tty kref.
  *
  * void (*cleanup)(struct tty_struct * tty);
  *