Subject: [PATCH usbnet v2.1] mtu change needs to stop RX

From: Soohoon Lee <[email-masked]>
Date: Fri, 24 Jun 2016 00:30:16 +0000

When MTU is changed unlink_urbs() flushes RX Q but mean while usbnet_bh() can fill up the Q at the same time.
Depends on which HCD is down there unlink takes long time then the flush never ends.

Signed-off-by: Soohoon Lee <[email-masked]>
Reviewed-by: Kimball Murray <[email-masked]>

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 61ba464..ce72dd0 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -395,8 +395,11 @@ int usbnet_change_mtu (struct net_device *net, int new_mtu)
        dev->hard_mtu = net->mtu + net->hard_header_len;
        if (dev->rx_urb_size == old_hard_mtu) {
                dev->rx_urb_size = dev->hard_mtu;
-               if (dev->rx_urb_size > old_rx_urb_size)
+               if (dev->rx_urb_size > old_rx_urb_size) {
+                       usbnet_pause_rx(dev);
                        usbnet_unlink_rx_urbs(dev);
+                       usbnet_resume_rx(dev);
+               }
        }

        /* max qlen depend on hard_mtu and rx_urb_size */
@@ -1509,6 +1512,7 @@ static void usbnet_bh (unsigned long param)
                   netif_device_present (dev->net) &&
                   netif_carrier_ok(dev->net) &&
                   !timer_pending (&dev->delay) &&
+                  !test_bit (EVENT_RX_PAUSED, &dev->flags) &&
                   !test_bit (EVENT_RX_HALT, &dev->flags)) {
                int     temp = dev->rxq.qlen;