Patch "Fix OpenSSH pty regression on close" has been added to the 4.4-stable tree

@@ -600,7 +600,7 @@ static ssize_t n_hdlc_tty_read(struct tt
 	add_wait_queue(&tty->read_wait, &wait);
 
 	for (;;) {
-		if (test_bit(TTY_OTHER_DONE, &tty->flags)) {
+		if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
 			ret = -EIO;
 			break;
 		}

@@ -828,7 +828,7 @@ static unsigned int n_hdlc_tty_poll(stru
 		/* set bits for operations that won't block */
 		if (n_hdlc->rx_buf_list.head)
 			mask |= POLLIN | POLLRDNORM;	/* readable */
-		if (test_bit(TTY_OTHER_DONE, &tty->flags))
+		if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 			mask |= POLLHUP;
 		if (tty_hung_up_p(filp))
 			mask |= POLLHUP;

102 lines not on this page · raw message

@@ -59,7 +59,7 @@ static void pty_close(struct tty_struct
 	if (!tty->link)
 		return;
 	set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
-	tty_flip_buffer_push(tty->link->port);
+	wake_up_interruptible(&tty->link->read_wait);
 	wake_up_interruptible(&tty->link->write_wait);
 	if (tty->driver->subtype == PTY_TYPE_MASTER) {
 		set_bit(TTY_OTHER_CLOSED, &tty->flags);

@@ -247,9 +247,7 @@ static int pty_open(struct tty_struct *t
 		goto out;
 
 	clear_bit(TTY_IO_ERROR, &tty->flags);
-	/* TTY_OTHER_CLOSED must be cleared before TTY_OTHER_DONE */
 	clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
-	clear_bit(TTY_OTHER_DONE, &tty->link->flags);
 	set_bit(TTY_THROTTLED, &tty->flags);
 	return 0;
 

@@ -37,29 +37,6 @@
 
 #define TTY_BUFFER_PAGE	(((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~0xFF)
 
-/*
- * If all tty flip buffers have been processed by flush_to_ldisc() or
- * dropped by tty_buffer_flush(), check if the linked pty has been closed.
- * If so, wake the reader/poll to process
- */
-static inline void check_other_closed(struct tty_struct *tty)
-{
-	unsigned long flags, old;
-
-	/* transition from TTY_OTHER_CLOSED => TTY_OTHER_DONE must be atomic */
-	for (flags = ACCESS_ONCE(tty->flags);
-	     test_bit(TTY_OTHER_CLOSED, &flags);
-	     ) {
-		old = flags;
-		__set_bit(TTY_OTHER_DONE, &flags);
-		flags = cmpxchg(&tty->flags, old, flags);
-		if (old == flags) {
-			wake_up_interruptible(&tty->read_wait);
-			break;
-		}
-	}
-}
-
 /**
  *	tty_buffer_lock_exclusive	-	gain exclusive access to buffer
  *	tty_buffer_unlock_exclusive	-	release exclusive access

@@ -254,8 +231,6 @@ void tty_buffer_flush(struct tty_struct
 	if (ld && ld->ops->flush_buffer)
 		ld->ops->flush_buffer(tty);
 
-	check_other_closed(tty);
-
 	atomic_dec(&buf->priority);
 	mutex_unlock(&buf->lock);
 }

@@ -505,10 +480,8 @@ static void flush_to_ldisc(struct work_s
 		 */
 		count = smp_load_acquire(&head->commit) - head->read;
 		if (!count) {
-			if (next == NULL) {
-				check_other_closed(tty);
+			if (next == NULL)
 				break;
-			}
 			buf->head = next;
 			tty_buffer_free(port, head);
 			continue;

@@ -597,3 +570,8 @@ bool tty_buffer_cancel_work(struct tty_p
 {
 	return cancel_work_sync(&port->buf.work);
 }
+
+void tty_buffer_flush_work(struct tty_port *port)
+{
+	flush_work(&port->buf.work);
+}

@@ -338,7 +338,6 @@ struct tty_file_private {
 #define TTY_EXCLUSIVE 		3	/* Exclusive open mode */
 #define TTY_DEBUG 		4	/* Debugging */
 #define TTY_DO_WRITE_WAKEUP 	5	/* Call write_wakeup after queuing new */
-#define TTY_OTHER_DONE		6	/* Closed pty has completed input processing */
 #define TTY_LDISC_OPEN	 	11	/* Line discipline is open */
 #define TTY_PTY_LOCK 		16	/* pty private */
 #define TTY_NO_WRITE_SPLIT 	17	/* Preserve write boundaries to driver */

@@ -469,6 +468,7 @@ extern void tty_buffer_init(struct tty_p
 extern void tty_buffer_set_lock_subclass(struct tty_port *port);
 extern bool tty_buffer_restart_work(struct tty_port *port);
 extern bool tty_buffer_cancel_work(struct tty_port *port);
+extern void tty_buffer_flush_work(struct tty_port *port);
 extern speed_t tty_termios_baud_rate(struct ktermios *termios);
 extern speed_t tty_termios_input_baud_rate(struct ktermios *termios);
 extern void tty_termios_encode_baud_rate(struct ktermios *termios,