From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934928AbcKNR1w (ORCPT ); Mon, 14 Nov 2016 12:27:52 -0500 Received: from shards.monkeyblade.net ([184.105.139.130]:37484 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934596AbcKNR1r (ORCPT ); Mon, 14 Nov 2016 12:27:47 -0500 Date: Mon, 14 Nov 2016 12:27:44 -0500 (EST) Message-Id: <20161114.122744.544066951483789132.davem@davemloft.net> To: hayeswang@realtek.com Cc: mlord@pobox.com, netdev@vger.kernel.org, nic_swsd@realtek.com, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org Subject: Re: [PATCH net 2/2] r8152: rx descriptor check From: David Miller In-Reply-To: <0835B3720019904CB8F7AA43166CEEB20104EBCC@RTITMBSV03.realtek.com.tw> References: <20161113.123954.2134945576362221851.davem@davemloft.net> <0835B3720019904CB8F7AA43166CEEB20104EBCC@RTITMBSV03.realtek.com.tw> X-Mailer: Mew version 6.7 on Emacs 24.5 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Mon, 14 Nov 2016 08:28:17 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Hayes Wang Date: Mon, 14 Nov 2016 07:23:51 +0000 > Mark Lord [mailto:mlord@pobox.com] >> Sent: Monday, November 14, 2016 4:34 AM > [...] >> Perhaps the driver >> is somehow accessing the buffer space again after doing usb_submit_urb()? >> That would certainly produce this kind of behaviour. > > I don't think so. First, the driver only read the received buffer. > That is, the driver would not change (or write) the data. Second, > The driver would lose the point address of the received buffer > after submitting the urb to the USB host controller, until the > transfer is completed by the USB host controller. That is, the > driver doesn't how to access the buffer after calling usb_submit_urb(). This is why it's most likely some DMA implementation issue or similar.