Patch "usb: gadget: u_ether: remove interrupt throttling" has been added to the 4.4-stable tree

Patch "usb: gadget: u_ether: remove interrupt throttling" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    usb: gadget: u_ether: remove interrupt throttling

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     usb-gadget-u_ether-remove-interrupt-throttling.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From fd9afd3cbe404998d732be6cc798f749597c5114 Mon Sep 17 00:00:00 2001
From: Felipe Balbi <felipe.balbi@linux.intel.com>
Date: Tue, 1 Nov 2016 13:20:22 +0200
Subject: usb: gadget: u_ether: remove interrupt throttling
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Felipe Balbi <felipe.balbi@linux.intel.com>

commit fd9afd3cbe404998d732be6cc798f749597c5114 upstream.

According to Dave Miller "the networking stack has a
hard requirement that all SKBs which are transmitted
must have their completion signalled in a fininte
amount of time. This is because, until the SKB is
freed by the driver, it holds onto socket,
netfilter, and other subsystem resources."

In summary, this means that using TX IRQ throttling
for the networking gadgets is, at least, complex and
we should avoid it for the time being.

Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Tested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Suggested-by: David Miller <davem@davemloft.net>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/gadget/function/u_ether.c |    8 --------
 1 file changed, 8 deletions(-)

--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -594,14 +594,6 @@ static netdev_tx_t eth_start_xmit(struct
 
 	req->length = length;
 
-	/* 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)) &&
-					!list_empty(&dev->tx_reqs))
-			? ((atomic_read(&dev->tx_qlen) % dev->qmult) != 0)
-			: 0;
-
 	retval = usb_ep_queue(in, req, GFP_ATOMIC);
 	switch (retval) {
 	default:


Patches currently in stable-queue which might be from felipe.balbi@linux.intel.com are

queue-4.4/usb-gadget-u_ether-remove-interrupt-throttling.patch