usbnet: ratelimit kevent may have been dropped warnings

From commit 9532021da6da48351ce48a079c673df8e3930b4a upstream.

when something goes wrong, a flood of these messages can be
generated by usbnet (thousands per second).  This doesn't
generally *help* the condition so this patch ratelimits the
rate of their generation.

There's an underlying problem in usbnet's kevent deferral
mechanism which needs fixing, specifically that events *can*
get dropped and not handled.  This patch doesn't address this,
but just mitigates fallout caused by the current implemention.

Signed-off-by: Steve Glendinning <steve.glendinning@shawell.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Change-Id: I708632185ca0b310c4082cab3571a2d6552bf135
CRs-Fixed: 430579
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 740c717..e9130f6 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -333,10 +333,12 @@
 void usbnet_defer_kevent (struct usbnet *dev, int work)
 {
 	set_bit (work, &dev->flags);
-	if (!schedule_work (&dev->kevent))
-		netdev_err(dev->net, "kevent %d may have been dropped\n", work);
-	else
+	if (!schedule_work (&dev->kevent)) {
+		if (net_ratelimit())
+			netdev_err(dev->net, "kevent %d may have been dropped\n", work);
+	} else {
 		netdev_dbg(dev->net, "kevent %d scheduled\n", work);
+	}
 }
 EXPORT_SYMBOL_GPL(usbnet_defer_kevent);