USB CDC NCM: tx_fixup() race condition fix

- tx_fixup() can be called from either timer callback or from xmit()
  in usbnet, so spinlock is added to avoid concurrency-related problem.
- minor correction due to checkpatch warning for some line over 80
  chars after previous patch was applied.
Signed-off-by: Alexey Orishko <alexey.orishko@stericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/cdc_ncm.c

@@ -54,7 +54,7 @@
 #include <linux/usb/usbnet.h>
 #include <linux/usb/cdc.h>
 
-#define	DRIVER_VERSION				"30-Nov-2010"
+#define	DRIVER_VERSION				"17-Jan-2011"
 
 /* CDC NCM subclass 3.2.1 */
 #define USB_CDC_NCM_NDP16_LENGTH_MIN		0x10
@@ -868,15 +868,19 @@ static void cdc_ncm_tx_timeout(unsigned long arg)
 	if (ctx->tx_timer_pending != 0) {
 		ctx->tx_timer_pending--;
 		restart = 1;
-	} else
+	} else {
 		restart = 0;
+	}
 
 	spin_unlock(&ctx->mtx);
 
-	if (restart)
+	if (restart) {
+		spin_lock(&ctx->mtx);
 		cdc_ncm_tx_timeout_start(ctx);
-	else if (ctx->netdev != NULL)
+		spin_unlock(&ctx->mtx);
+	} else if (ctx->netdev != NULL) {
 		usbnet_start_xmit(NULL, ctx->netdev);
+	}
 }
 
 static struct sk_buff *
@@ -900,7 +904,6 @@ cdc_ncm_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
 	skb_out = cdc_ncm_fill_tx_frame(ctx, skb);
 	if (ctx->tx_curr_skb != NULL)
 		need_timer = 1;
-	spin_unlock(&ctx->mtx);
 
 	/* Start timer, if there is a remaining skb */
 	if (need_timer)
@@ -908,6 +911,8 @@ cdc_ncm_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
 
 	if (skb_out)
 		dev->net->stats.tx_packets += ctx->tx_curr_frame_num;
+
+	spin_unlock(&ctx->mtx);
 	return skb_out;
 
 error: