tty: n_gsm: improve software flowcontrol

index 4a43ef5d7..0cad08fa 100644
@@ -152,6 +152,7 @@ struct gsm_dlci {
 	/* Flow control */
 	int throttled;		/* Private copy of throttle state */
 	int constipated;	/* Throttle status for outgoing */
+	struct list_head constipated_list; /* msg's removed from tx queue */
 	/* Packetised I/O */
 	struct sk_buff *skb;	/* Frame being sent */
 	struct sk_buff_head skb_list;	/* Queued frames */

@@ -684,7 +685,8 @@ static void gsm_data_kick(struct gsm_mux *gsm)
 	int skip_sof = 0;
 
 	list_for_each_entry_safe(msg, nmsg, &gsm->tx_list, list) {
-		if (gsm->constipated && msg->addr)
+		if (gsm->constipated && msg->addr ||
+		    gsm->dlci[msg->addr]->constipated)
 			continue;
 		if (gsm->encoding != 0) {
 			gsm->txframe[0] = GSM1_SOF;

@@ -931,7 +933,7 @@ static void gsm_dlci_data_sweep(struct gsm_mux *gsm)
 	int len;
 	/* Priority ordering: We should do priority with RR of the groups */
 	int i = 1;
-
+	struct tty_struct *tty;
 	while (i < NUM_DLCI) {
 		struct gsm_dlci *dlci;
 

@@ -946,6 +948,13 @@ static void gsm_dlci_data_sweep(struct gsm_mux *gsm)
 			len = gsm_dlci_data_output(gsm, dlci);
 		else
 			len = gsm_dlci_data_output_framed(gsm, dlci);
+
+		if (len >= 0) {
+			tty = tty_port_tty_get(&dlci->port);
+			if (tty)
+				tty_wakeup(dlci->port.tty);
+		}
+
 		if (len < 0)
 			break;
 		/* DLCI empty - try the next */

@@ -1029,7 +1038,8 @@ static void gsm_process_modem(struct tty_struct *tty, struct gsm_dlci *dlci,
 	int  mlines = 0;
 	u8 brk = 0;
 	int fc;
-
+	struct gsm_msg *msg, *nmsg;
+	unsigned long flags;
 	/* The modem status command can either contain one octet (v.24 signals)
 	   or two octets (v.24 signals + break signals). The length field will
 	   either be 2 or 3 respectively. This is specified in section

@@ -1047,8 +1057,27 @@ static void gsm_process_modem(struct tty_struct *tty, struct gsm_dlci *dlci,
 	if (fc && !dlci->constipated) {
 		/* Need to throttle our output on this device */
 		dlci->constipated = 1;
+		spin_lock_irqsave(&dlci->gsm->tx_lock, flags);
+		list_for_each_entry_safe(msg, nmsg, &dlci->gsm->tx_list, list) {
+			list_del(&msg->list);	/* remove from msgqueue */
+			/* add to list of messages which could not be sent
+			   because of constipation */
+			list_add_tail(&msg->list, &dlci->constipated_list);
+			dlci->gsm->tx_bytes -= msg->len;
+		}
+		spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags);
+
 	} else if (!fc && dlci->constipated) {
 		dlci->constipated = 0;
+		spin_lock_irqsave(&dlci->gsm->tx_lock, flags);
+		list_for_each_entry_safe(msg, nmsg, &dlci->constipated_list,
+					 list) {
+			list_del(&msg->list);	/* remove from msgqueue */
+			/* add to global messagequeue */
+			list_add_tail(&msg->list,  &dlci->gsm->tx_list);
+			dlci->gsm->tx_bytes += msg->len;
+		}
+		spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags);
 		gsm_dlci_data_kick(dlci);
 	}
 

@@ -1640,6 +1669,7 @@ static struct gsm_dlci *gsm_dlci_alloc(struct gsm_mux *gsm, int addr)
 		kfree(dlci);
 		return NULL;
 	}
+	INIT_LIST_HEAD(&dlci->constipated_list);
 
 	skb_queue_head_init(&dlci->skb_list);
 	init_timer(&dlci->t1);

@@ -2956,7 +2986,7 @@ static void gsmtty_close(struct tty_struct *tty, struct file *filp)
 {
 	struct gsm_dlci *dlci = tty->driver_data;
 	struct gsm_mux *gsm;
-
+	struct gsm_msg *msg, *nmsg;
 	if (dlci == NULL)
 		return;
 	if (dlci->state == DLCI_CLOSED)

@@ -2965,6 +2995,12 @@ static void gsmtty_close(struct tty_struct *tty, struct file *filp)
 	gsm_destroy_network(dlci);
 	mutex_unlock(&dlci->mutex);
 	gsm = dlci->gsm;
+
+	list_for_each_entry_safe(msg, nmsg, &dlci->constipated_list, list) {
+		list_del(&msg->list);
+		kfree(msg);
+	}
+
 	if (tty_port_close_start(&dlci->port, tty, filp) == 0)
 		goto out;
 	gsm_dlci_begin_close(dlci);