From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752784Ab3KSUZl (ORCPT ); Tue, 19 Nov 2013 15:25:41 -0500 Received: from shards.monkeyblade.net ([149.20.54.216]:57821 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752355Ab3KSUZj (ORCPT ); Tue, 19 Nov 2013 15:25:39 -0500 Date: Tue, 19 Nov 2013 15:25:36 -0500 (EST) Message-Id: <20131119.152536.146706009595105149.davem@davemloft.net> To: hayeswang@realtek.com Cc: netdev@vger.kernel.org, nic_swsd@realtek.com, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org Subject: Re: [PATCH net v4 3/4] r8152: support stopping/waking tx queue From: David Miller In-Reply-To: <1384831511-1625-4-git-send-email-hayeswang@realtek.com> References: <1384502279-9959-1-git-send-email-hayeswang@realtek.com> <1384831511-1625-1-git-send-email-hayeswang@realtek.com> <1384831511-1625-4-git-send-email-hayeswang@realtek.com> X-Mailer: Mew version 6.5 on Emacs 24.1 / 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-4.5.1 (shards.monkeyblade.net [0.0.0.0]); Tue, 19 Nov 2013 12:25:38 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Hayes Wang Date: Tue, 19 Nov 2013 11:25:10 +0800 > The maximum packet number which a tx aggregation buffer could contain > is the buffer size / (packet size + descriptor size). > > If the tx buffer is empty and the tx queue length is more than the > maximum value which is defined above, stop the tx queue. Wake the tx > queue after any queued packet is filled in a available tx buffer. > > Signed-off-by: Hayes Wang This is racy. You have nothing which synchronizes r8152_tx_agg_fill() and rtl8152_start_xmit(), therefore: > + if (netif_queue_stopped(tp->netdev)) > + netif_wake_queue(tp->netdev); > + A netif_stop_queue() can occur right after the netif_queue_stopped() check, meaning you can end up with the queue being stopped forever and the TX queue stuck. I am finding this patch series _very_ tiring, every single time I take the time to review it, I find major problems.