TTY/Serial fixes for 4.1-rc4

Here's some TTY and serial driver fixes for reported issues.  All of
 these have been in linux-next successfully.
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'tty-4.1-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

Pull tty/serial fixes from Greg KH:
 "Here's some TTY and serial driver fixes for reported issues.

  All of these have been in linux-next successfully"

* tag 'tty-4.1-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  pty: Fix input race when closing
  tty/n_gsm.c: fix a memory leak when gsmtty is removed
  Revert "serial/amba-pl011: Leave the TX IRQ alone when the UART is not open"
  serial: omap: Fix error handling in probe
  earlycon: Revert log warnings

Documentation/serial/tty.txt

@@ -198,6 +198,9 @@ TTY_IO_ERROR		If set, causes all subsequent userspace read/write
 
 TTY_OTHER_CLOSED	Device is a pty and the other side has closed.
 
+TTY_OTHER_DONE		Device is a pty and the other side has closed and
+			all pending input processing has been completed.
+
 TTY_NO_WRITE_SPLIT	Prevent driver from splitting up writes into
 			smaller chunks.
 

drivers/tty/n_gsm.c

@@ -3170,7 +3170,7 @@ static int gsmtty_break_ctl(struct tty_struct *tty, int state)
 	return gsmtty_modem_update(dlci, encode);
 }
 
-static void gsmtty_remove(struct tty_driver *driver, struct tty_struct *tty)
+static void gsmtty_cleanup(struct tty_struct *tty)
 {
 	struct gsm_dlci *dlci = tty->driver_data;
 	struct gsm_mux *gsm = dlci->gsm;
@@ -3178,7 +3178,6 @@ static void gsmtty_remove(struct tty_driver *driver, struct tty_struct *tty)
 	dlci_put(dlci);
 	dlci_put(gsm->dlci[0]);
 	mux_put(gsm);
-	driver->ttys[tty->index] = NULL;
 }
 
 /* Virtual ttys for the demux */
@@ -3199,7 +3198,7 @@ static const struct tty_operations gsmtty_ops = {
 	.tiocmget		= gsmtty_tiocmget,
 	.tiocmset		= gsmtty_tiocmset,
 	.break_ctl		= gsmtty_break_ctl,
-	.remove			= gsmtty_remove,
+	.cleanup		= gsmtty_cleanup,
 };
 
 

drivers/tty/n_hdlc.c

@@ -600,7 +600,7 @@ static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
 	add_wait_queue(&tty->read_wait, &wait);
 
 	for (;;) {
-		if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
+		if (test_bit(TTY_OTHER_DONE, &tty->flags)) {
 			ret = -EIO;
 			break;
 		}
@@ -828,7 +828,7 @@ static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
 		/* set bits for operations that won't block */
 		if (n_hdlc->rx_buf_list.head)
 			mask |= POLLIN | POLLRDNORM;	/* readable */
-		if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
+		if (test_bit(TTY_OTHER_DONE, &tty->flags))
 			mask |= POLLHUP;
 		if (tty_hung_up_p(filp))
 			mask |= POLLHUP;

drivers/tty/n_tty.c

@@ -1949,6 +1949,18 @@ static inline int input_available_p(struct tty_struct *tty, int poll)
 		return ldata->commit_head - ldata->read_tail >= amt;
 }
 
+static inline int check_other_done(struct tty_struct *tty)
+{
+	int done = test_bit(TTY_OTHER_DONE, &tty->flags);
+	if (done) {
+		/* paired with cmpxchg() in check_other_closed(); ensures
+		 * read buffer head index is not stale
+		 */
+		smp_mb__after_atomic();
+	}
+	return done;
+}
+
 /**
  *	copy_from_read_buf	-	copy read data directly
  *	@tty: terminal device
@@ -2167,7 +2179,7 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
 	struct n_tty_data *ldata = tty->disc_data;
 	unsigned char __user *b = buf;
 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
-	int c;
+	int c, done;
 	int minimum, time;
 	ssize_t retval = 0;
 	long timeout;
@@ -2235,8 +2247,10 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
 		    ((minimum - (b - buf)) >= 1))
 			ldata->minimum_to_wake = (minimum - (b - buf));
 
+		done = check_other_done(tty);
+
 		if (!input_available_p(tty, 0)) {
-			if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
+			if (done) {
 				retval = -EIO;
 				break;
 			}
@@ -2443,12 +2457,12 @@ static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
 
 	poll_wait(file, &tty->read_wait, wait);
 	poll_wait(file, &tty->write_wait, wait);
+	if (check_other_done(tty))
+		mask |= POLLHUP;
 	if (input_available_p(tty, 1))
 		mask |= POLLIN | POLLRDNORM;
 	if (tty->packet && tty->link->ctrl_status)
 		mask |= POLLPRI | POLLIN | POLLRDNORM;
-	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
-		mask |= POLLHUP;
 	if (tty_hung_up_p(file))
 		mask |= POLLHUP;
 	if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {

drivers/tty/pty.c

@@ -53,9 +53,8 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
 	/* Review - krefs on tty_link ?? */
 	if (!tty->link)
 		return;
-	tty_flush_to_ldisc(tty->link);
 	set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
-	wake_up_interruptible(&tty->link->read_wait);
+	tty_flip_buffer_push(tty->link->port);
 	wake_up_interruptible(&tty->link->write_wait);
 	if (tty->driver->subtype == PTY_TYPE_MASTER) {
 		set_bit(TTY_OTHER_CLOSED, &tty->flags);
@@ -243,7 +242,9 @@ static int pty_open(struct tty_struct *tty, struct file *filp)
 		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;
 

drivers/tty/serial/amba-pl011.c

@@ -1639,6 +1639,9 @@ static int pl011_startup(struct uart_port *port)
 
 	writew(uap->vendor->ifls, uap->port.membase + UART011_IFLS);
 
+	/* Assume that TX IRQ doesn't work until we see one: */
+	uap->tx_irq_seen = 0;
+
 	spin_lock_irq(&uap->port.lock);
 
 	/* restore RTS and DTR */
@@ -1702,7 +1705,7 @@ static void pl011_shutdown(struct uart_port *port)
 	spin_lock_irq(&uap->port.lock);
 	uap->im = 0;
 	writew(uap->im, uap->port.membase + UART011_IMSC);
-	writew(0xffff & ~UART011_TXIS, uap->port.membase + UART011_ICR);
+	writew(0xffff, uap->port.membase + UART011_ICR);
 	spin_unlock_irq(&uap->port.lock);
 
 	pl011_dma_shutdown(uap);

drivers/tty/serial/earlycon.c

@@ -187,13 +187,8 @@ static int __init param_setup_earlycon(char *buf)
 		return 0;
 
 	err = setup_earlycon(buf);
-	if (err == -ENOENT) {
-		pr_warn("no match for %s\n", buf);
-		err = 0;
-	} else if (err == -EALREADY) {
-		pr_warn("already registered\n");
-		err = 0;
-	}
+	if (err == -ENOENT || err == -EALREADY)
+		return 0;
 	return err;
 }
 early_param("earlycon", param_setup_earlycon);

drivers/tty/serial/omap-serial.c

@@ -1735,6 +1735,8 @@ static int serial_omap_probe(struct platform_device *pdev)
 err_add_port:
 	pm_runtime_put(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
+	pm_qos_remove_request(&up->pm_qos_request);
+	device_init_wakeup(up->dev, false);
 err_rs485:
 err_port_line:
 	return ret;

drivers/tty/tty_buffer.c

@@ -37,6 +37,28 @@
 
 #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
@@ -229,6 +251,8 @@ void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld)
 	if (ld && ld->ops->flush_buffer)
 		ld->ops->flush_buffer(tty);
 
+	check_other_closed(tty);
+
 	atomic_dec(&buf->priority);
 	mutex_unlock(&buf->lock);
 }
@@ -471,8 +495,10 @@ static void flush_to_ldisc(struct work_struct *work)
 		smp_rmb();
 		count = head->commit - head->read;
 		if (!count) {
-			if (next == NULL)
+			if (next == NULL) {
+				check_other_closed(tty);
 				break;
+			}
 			buf->head = next;
 			tty_buffer_free(port, head);
 			continue;
@@ -488,19 +514,6 @@ static void flush_to_ldisc(struct work_struct *work)
 	tty_ldisc_deref(disc);
 }
 
-/**
- *	tty_flush_to_ldisc
- *	@tty: tty to push
- *
- *	Push the terminal flip buffers to the line discipline.
- *
- *	Must not be called from IRQ context.
- */
-void tty_flush_to_ldisc(struct tty_struct *tty)
-{
-	flush_work(&tty->port->buf.work);
-}
-
 /**
  *	tty_flip_buffer_push	-	terminal
  *	@port: tty port to push

include/linux/tty.h

@@ -339,6 +339,7 @@ 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 */
@@ -462,7 +463,6 @@ extern int tty_hung_up_p(struct file *filp);
 extern void do_SAK(struct tty_struct *tty);
 extern void __do_SAK(struct tty_struct *tty);
 extern void no_tty(void);
-extern void tty_flush_to_ldisc(struct tty_struct *tty);
 extern void tty_buffer_free_all(struct tty_port *port);
 extern void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld);
 extern void tty_buffer_init(struct tty_port *port);