From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 511DDC433FE for ; Wed, 16 Nov 2022 08:56:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233027AbiKPI4G (ORCPT ); Wed, 16 Nov 2022 03:56:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51758 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230429AbiKPI4D (ORCPT ); Wed, 16 Nov 2022 03:56:03 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8229C1142; Wed, 16 Nov 2022 00:56:01 -0800 (PST) Received: from dggpeml500024.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4NBxhn1yD4zmW28; Wed, 16 Nov 2022 16:55:37 +0800 (CST) Received: from dggpeml500006.china.huawei.com (7.185.36.76) by dggpeml500024.china.huawei.com (7.185.36.10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Wed, 16 Nov 2022 16:55:59 +0800 Received: from [10.174.178.240] (10.174.178.240) by dggpeml500006.china.huawei.com (7.185.36.76) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Wed, 16 Nov 2022 16:55:58 +0800 Subject: Re: [PATCH net v2 3/3] net: nixge: fix tx queue handling To: Francois Romieu CC: , , , , , , References: <1668525024-38409-1-git-send-email-zhangchangzhong@huawei.com> <1668525024-38409-4-git-send-email-zhangchangzhong@huawei.com> From: Zhang Changzhong Message-ID: Date: Wed, 16 Nov 2022 16:55:58 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.240] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpeml500006.china.huawei.com (7.185.36.76) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/11/16 7:04, Francois Romieu wrote: > Zhang Changzhong : >> Currently the driver check for available space at the beginning of >> nixge_start_xmit(), and when there is not enough space for this packet, >> it returns NETDEV_TX_OK, which casues packet loss and memory leak. >> >> Instead the queue should be stopped after the packet is added to the BD >> when there may not be enough space for next packet. In addition, the >> queue should be wakeup only if there is enough space for a packet with >> max frags. >> >> Fixes: 492caffa8a1a ("net: ethernet: nixge: Add support for National Instruments XGE netdev") >> Signed-off-by: Zhang Changzhong >> --- >> drivers/net/ethernet/ni/nixge.c | 54 +++++++++++++++++++++++++++++------------ >> 1 file changed, 38 insertions(+), 16 deletions(-) >> >> diff --git a/drivers/net/ethernet/ni/nixge.c b/drivers/net/ethernet/ni/nixge.c >> index 91b7ebc..3776a03 100644 >> --- a/drivers/net/ethernet/ni/nixge.c >> +++ b/drivers/net/ethernet/ni/nixge.c > [...] >> static netdev_tx_t nixge_start_xmit(struct sk_buff *skb, >> @@ -518,10 +523,15 @@ static netdev_tx_t nixge_start_xmit(struct sk_buff *skb, >> cur_p = &priv->tx_bd_v[priv->tx_bd_tail]; >> tx_skb = &priv->tx_skb[priv->tx_bd_tail]; >> >> - if (nixge_check_tx_bd_space(priv, num_frag + 1)) { >> - if (!netif_queue_stopped(ndev)) >> - netif_stop_queue(ndev); >> - return NETDEV_TX_OK; >> + if (unlikely(nixge_check_tx_bd_space(priv, num_frag + 1))) { >> + /* Should not happen as last start_xmit call should have >> + * checked for sufficient space and queue should only be >> + * woken when sufficient space is available. >> + */ > > Almost. IRQ triggering after nixge_start_xmit::netif_stop_queue and > before nixge_start_xmit::smp_mb may wrongly wake queue. > I don't know what you mean by "wronly wake queue". The queue is woken only when there is sufficient for next packet. > Call me timorous but I would feel more confortable if this code could > be tested on real hardware before being fed into -net. > I agree with you, hope someone can test and correct it. Thanks, Changzhong