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

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 <[email protected]> know about it.

From: Felipe Balbi <[email protected]>
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 <[email protected]>

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.

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

@@ -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 [email protected] are

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