usb: gadget: function: u_ether: don't starve tx request queue

If we don't guarantee that we will always get an
interrupt at least when we're queueing our very last
request, we could fall into situation where we queue
every request with 'no_interrupt' set. This will
cause the link to get stuck.

The behavior above has been triggered with g_ether
and dwc3.

Cc: <stable@vger.kernel.org>
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
index 9c8c9ed1dc9e0b2186e60e66488ea1159f22d7b8..fe1811650dbc3d9fb0fc6a983486cbae3b653475 100644 (file)
--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -590,8 +590,9 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
 
        /* throttle high/super speed IRQ rate back slightly */
        if (gadget_is_dualspeed(dev->gadget))
-               req->no_interrupt = (dev->gadget->speed == USB_SPEED_HIGH ||
-                                    dev->gadget->speed == USB_SPEED_SUPER)
+               req->no_interrupt = (((dev->gadget->speed == USB_SPEED_HIGH ||
+                                      dev->gadget->speed == USB_SPEED_SUPER)) &&
+                                       !list_empty(&dev->tx_reqs))
                        ? ((atomic_read(&dev->tx_qlen) % dev->qmult) != 0)
                        : 0;