tty: Revert the tty locking series, it needs more work

This reverts the tty layer change to use per-tty locking, because it's
not correct yet, and fixing it will require some more deep surgery.

The main revert is d29f3ef39be4 ("tty_lock: Localise the lock"), but
there are several smaller commits that built upon it, they also get
reverted here. The list of reverted commits is:

  fde86d310886 - tty: add lockdep annotations
  8f6576ad476b - tty: fix ldisc lock inversion trace
  d3ca8b64b97e - pty: Fix lock inversion
  b1d679afd766 - tty: drop the pty lock during hangup
  abcefe5fc357 - tty/amiserial: Add missing argument for tty_unlock()
  fd11b42e3598 - cris: fix missing tty arg in wait_event_interruptible_tty call
  d29f3ef39be4 - tty_lock: Localise the lock

The revert had a trivial conflict in the 68360serial.c staging driver
that got removed in the meantime.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 14 deletions

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 65c7c62..5505ffc 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -47,7 +47,6 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
 	wake_up_interruptible(&tty->read_wait);
 	wake_up_interruptible(&tty->write_wait);
 	tty->packet = 0;
-	/* Review - krefs on tty_link ?? */
 	if (!tty->link)
 		return;
 	tty->link->packet = 0;
@@ -63,9 +62,9 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
 		        mutex_unlock(&devpts_mutex);
 		}
 #endif
-		tty_unlock(tty);
+		tty_unlock();
 		tty_vhangup(tty->link);
-		tty_lock(tty);
+		tty_lock();
 	}
 }
 
@@ -623,27 +622,26 @@ static int ptmx_open(struct inode *inode, struct file *filp)
 		return retval;
 
 	/* find a device that is not in use. */
-	mutex_lock(&devpts_mutex);
+	tty_lock();
 	index = devpts_new_index(inode);
+	tty_unlock();
 	if (index < 0) {
 		retval = index;
 		goto err_file;
 	}
 
-	mutex_unlock(&devpts_mutex);
-
 	mutex_lock(&tty_mutex);
+	mutex_lock(&devpts_mutex);
 	tty = tty_init_dev(ptm_driver, index);
+	mutex_unlock(&devpts_mutex);
+	tty_lock();
+	mutex_unlock(&tty_mutex);
 
 	if (IS_ERR(tty)) {
 		retval = PTR_ERR(tty);
 		goto out;
 	}
 
-	/* The tty returned here is locked so we can safely
-	   drop the mutex */
-	mutex_unlock(&tty_mutex);
-
 	set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 
 	tty_add_file(tty, filp);
@@ -656,17 +654,16 @@ static int ptmx_open(struct inode *inode, struct file *filp)
 	if (retval)
 		goto err_release;
 
-	tty_unlock(tty);
+	tty_unlock();
 	return 0;
 err_release:
-	tty_unlock(tty);
+	tty_unlock();
 	tty_release(inode, filp);
 	return retval;
 out:
-	mutex_unlock(&tty_mutex);
 	devpts_kill_index(inode, index);
+	tty_unlock();
 err_file:
-        mutex_unlock(&devpts_mutex);
 	tty_free_file(filp);
 	return retval;
 }