[PATCH net v2] net: usb: kaweth: remove TX queue manipulation in kaweth_set_rx_mode

[Ziyi Guo]

kaweth_set_rx_mode(), the ndo_set_rx_mode callback, calls
netif_stop_queue() and netif_wake_queue(). These are TX queue flow
control functions unrelated to RX multicast configuration.

The premature netif_wake_queue() can re-enable TX while tx_urb is still
in-flight, leading to a double usb_submit_urb() on the same URB:

kaweth_start_xmit() {
    netif_stop_queue();
    usb_submit_urb(kaweth->tx_urb);
}

kaweth_set_rx_mode() {
    netif_stop_queue();
    netif_wake_queue();             // wakes TX queue before URB is done
}

kaweth_start_xmit() {
    netif_stop_queue();
    usb_submit_urb(kaweth->tx_urb); // URB submitted while active
}

This triggers the WARN in usb_submit_urb():

  "URB submitted while active"

This is a similar class of bug fixed in rtl8150 by

- commit 958baf5eaee3 ("net: usb: Remove disruptive netif_wake_queue in rtl8150_set_multicast").

Also kaweth_set_rx_mode() is already functionally broken, the
real set_rx_mode action is performed by kaweth_async_set_rx_mode(),
which in turn is not a no-op only at ndo_open() time.

Suggested-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Ziyi Guo <n7l8m4@xxxxxxxxxxxxxxxxxx>
---
v2:
 - Add fixes tag, net prefix and Suggested-by tag.
 - Add explanation of safety of removing netif_stop_queue().

 drivers/net/usb/kaweth.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/net/usb/kaweth.c b/drivers/net/usb/kaweth.c
index c9efb7df892e..e01d14f6c366 100644
--- a/drivers/net/usb/kaweth.c
+++ b/drivers/net/usb/kaweth.c
@@ -765,7 +765,6 @@ static void kaweth_set_rx_mode(struct net_device *net)
 
 	netdev_dbg(net, "Setting Rx mode to %d\n", packet_filter_bitmap);
 
-	netif_stop_queue(net);
 
 	if (net->flags & IFF_PROMISC) {
 		packet_filter_bitmap |= KAWETH_PACKET_FILTER_PROMISCUOUS;
@@ -775,7 +774,6 @@ static void kaweth_set_rx_mode(struct net_device *net)
 	}
 
 	kaweth->packet_filter_bitmap = packet_filter_bitmap;
-	netif_wake_queue(net);
 }
 
 /****************************************************************
-- 
2.34.1