TTY: hvsi, use tty from tty_port

Now, we switch to the refcounted model and do not need hp->lock to
protect hp->tty anymore.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/hvc/hvsi.c

@@ -76,7 +76,6 @@ struct hvsi_struct {
 	wait_queue_head_t stateq; /* woken when HVSI state changes */
 	spinlock_t lock;
 	int index;
-	struct tty_struct *tty;
 	uint8_t throttle_buf[128];
 	uint8_t outbuf[N_OUTBUF]; /* to implement write_room and chars_in_buffer */
 	/* inbuf is for packet reassembly. leave a little room for leftovers. */
@@ -492,14 +491,17 @@ static irqreturn_t hvsi_interrupt(int irq, void *arg)
 {
 	struct hvsi_struct *hp = (struct hvsi_struct *)arg;
 	struct hvsi_struct *handshake;
+	struct tty_struct *tty;
 	unsigned long flags;
 	int again = 1;
 
 	pr_debug("%s\n", __func__);
 
+	tty = tty_port_tty_get(&hp->port);
+
 	while (again) {
 		spin_lock_irqsave(&hp->lock, flags);
-		again = hvsi_load_chunk(hp, hp->tty, &handshake);
+		again = hvsi_load_chunk(hp, tty, &handshake);
 		spin_unlock_irqrestore(&hp->lock, flags);
 
 		if (handshake) {
@@ -509,15 +511,16 @@ static irqreturn_t hvsi_interrupt(int irq, void *arg)
 	}
 
 	spin_lock_irqsave(&hp->lock, flags);
-	if (hp->tty && hp->n_throttle
-			&& (!test_bit(TTY_THROTTLED, &hp->tty->flags))) {
-		/* we weren't hung up and we weren't throttled, so we can deliver the
-		 * rest now */
-		hvsi_send_overflow(hp, hp->tty);
-		tty_flip_buffer_push(hp->tty);
+	if (tty && hp->n_throttle && !test_bit(TTY_THROTTLED, &tty->flags)) {
+		/* we weren't hung up and we weren't throttled, so we can
+		 * deliver the rest now */
+		hvsi_send_overflow(hp, tty);
+		tty_flip_buffer_push(tty);
 	}
 	spin_unlock_irqrestore(&hp->lock, flags);
 
+	tty_kref_put(tty);
+
 	return IRQ_HANDLED;
 }
 
@@ -724,8 +727,8 @@ static int hvsi_open(struct tty_struct *tty, struct file *filp)
 	if (hp->state == HVSI_FSP_DIED)
 		return -EIO;
 
+	tty_port_tty_set(&hp->port, tty);
 	spin_lock_irqsave(&hp->lock, flags);
-	hp->tty = tty;
 	hp->port.count++;
 	atomic_set(&hp->seqno, 0);
 	h_vio_signal(hp->vtermno, VIO_IRQ_ENABLE);
@@ -784,7 +787,7 @@ static void hvsi_close(struct tty_struct *tty, struct file *filp)
 	spin_lock_irqsave(&hp->lock, flags);
 
 	if (--hp->port.count == 0) {
-		hp->tty = NULL;
+		tty_port_tty_set(&hp->port, NULL);
 		hp->inbuf_end = hp->inbuf; /* discard remaining partial packets */
 
 		/* only close down connection if it is not the console */
@@ -830,12 +833,11 @@ static void hvsi_hangup(struct tty_struct *tty)
 
 	pr_debug("%s\n", __func__);
 
-	spin_lock_irqsave(&hp->lock, flags);
+	tty_port_tty_set(&hp->port, NULL);
 
+	spin_lock_irqsave(&hp->lock, flags);
 	hp->port.count = 0;
 	hp->n_outbuf = 0;
-	hp->tty = NULL;
-
 	spin_unlock_irqrestore(&hp->lock, flags);
 }
 
@@ -863,6 +865,7 @@ static void hvsi_write_worker(struct work_struct *work)
 {
 	struct hvsi_struct *hp =
 		container_of(work, struct hvsi_struct, writer.work);
+	struct tty_struct *tty;
 	unsigned long flags;
 #ifdef DEBUG
 	static long start_j = 0;
@@ -896,7 +899,11 @@ static void hvsi_write_worker(struct work_struct *work)
 		start_j = 0;
 #endif /* DEBUG */
 		wake_up_all(&hp->emptyq);
-		tty_wakeup(hp->tty);
+		tty = tty_port_tty_get(&hp->port);
+		if (tty) {
+			tty_wakeup(tty);
+			tty_kref_put(tty);
+		}
 	}
 
 out: