tty: Remove TTY_HUPPING

Now that tty_ldisc_hangup() does not drop the tty lock, it is no
longer possible to observe TTY_HUPPING while holding the tty lock
on another cpu.

Remove TTY_HUPPING bit definition.
Reviewed-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_io.c

@@ -690,9 +690,6 @@ static void __tty_hangup(struct tty_struct *tty, int exit_session)
 		return;
 	}
 
-	/* some functions below drop BTM, so we need this bit */
-	set_bit(TTY_HUPPING, &tty->flags);
-
 	/* inuse_filps is protected by the single tty lock,
 	   this really needs to change if we want to flush the
 	   workqueue with the lock held */
@@ -717,10 +714,6 @@ static void __tty_hangup(struct tty_struct *tty, int exit_session)
 	while (refs--)
 		tty_kref_put(tty);
 
-	/*
-	 * it drops BTM and thus races with reopen
-	 * we protect the race by TTY_HUPPING
-	 */
 	tty_ldisc_hangup(tty);
 
 	spin_lock_irq(&tty->ctrl_lock);
@@ -752,8 +745,6 @@ static void __tty_hangup(struct tty_struct *tty, int exit_session)
 	 * can't yet guarantee all that.
 	 */
 	set_bit(TTY_HUPPED, &tty->flags);
-	clear_bit(TTY_HUPPING, &tty->flags);
-
 	tty_unlock(tty);
 
 	if (f)
@@ -1461,8 +1452,7 @@ static int tty_reopen(struct tty_struct *tty)
 {
 	struct tty_driver *driver = tty->driver;
 
-	if (test_bit(TTY_CLOSING, &tty->flags) ||
-			test_bit(TTY_HUPPING, &tty->flags))
+	if (test_bit(TTY_CLOSING, &tty->flags))
 		return -EIO;
 
 	if (driver->type == TTY_DRIVER_TYPE_PTY &&

drivers/tty/tty_ldisc.c

@@ -544,8 +544,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 
 	old_ldisc = tty->ldisc;
 
-	if (test_bit(TTY_HUPPING, &tty->flags) ||
-	    test_bit(TTY_HUPPED, &tty->flags)) {
+	if (test_bit(TTY_HUPPED, &tty->flags)) {
 		/* We were raced by the hangup method. It will have stomped
 		   the ldisc data and closed the ldisc down */
 		tty_ldisc_enable_pair(tty, o_tty);

include/linux/tty.h

@@ -321,7 +321,6 @@ struct tty_file_private {
 #define TTY_PTY_LOCK 		16	/* pty private */
 #define TTY_NO_WRITE_SPLIT 	17	/* Preserve write boundaries to driver */
 #define TTY_HUPPED 		18	/* Post driver->hangup() */
-#define TTY_HUPPING 		21	/* ->hangup() in progress */
 #define TTY_LDISC_HALTED	22	/* Line discipline is halted */
 
 #define TTY_WRITE_FLUSH(tty) tty_write_flush((tty))