From patchwork Fri May 31 18:15:40 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Robert Hancock X-Patchwork-Id: 1108515 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=sedsystems.ca Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45FtKv3q7Sz9s5c for ; Sat, 1 Jun 2019 04:30:27 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727140AbfEaSa0 (ORCPT ); Fri, 31 May 2019 14:30:26 -0400 Received: from sed198n136.SEDSystems.ca ([198.169.180.136]:25532 "EHLO sed198n136.sedsystems.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727122AbfEaSaZ (ORCPT ); Fri, 31 May 2019 14:30:25 -0400 X-Greylist: delayed 854 seconds by postgrey-1.27 at vger.kernel.org; Fri, 31 May 2019 14:30:19 EDT Received: from barney.sedsystems.ca (barney [198.169.180.121]) by sed198n136.sedsystems.ca with ESMTP id x4VIGUL9030727 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 31 May 2019 12:16:30 -0600 (CST) Received: from SED.RFC1918.192.168.sedsystems.ca (eng1n65.eng.sedsystems.ca [172.21.1.65]) by barney.sedsystems.ca (8.14.7/8.14.4) with ESMTP id x4VIG5Dq043766 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Fri, 31 May 2019 12:16:14 -0600 From: Robert Hancock To: netdev@vger.kernel.org Cc: anirudh@xilinx.com, John.Linn@xilinx.com, Robert Hancock Subject: [PATCH net-next 08/13] net: axienet: Fix race condition causing TX hang Date: Fri, 31 May 2019 12:15:40 -0600 Message-Id: <1559326545-28825-9-git-send-email-hancock@sedsystems.ca> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1559326545-28825-1-git-send-email-hancock@sedsystems.ca> References: <1559326545-28825-1-git-send-email-hancock@sedsystems.ca> X-Scanned-By: MIMEDefang 2.64 on 198.169.180.136 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org It is possible that the interrupt handler fires and frees up space in the TX ring in between checking for sufficient TX ring space and stopping the TX queue in axienet_start_xmit. If this happens, the queue wake from the interrupt handler will occur before the queue is stopped, causing a lost wakeup and the adapter's transmit hanging. To avoid this, after stopping the queue, check again whether there is sufficient space in the TX ring. If so, wake up the queue again. Signed-off-by: Robert Hancock --- drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c index f2a8c5c..9949e67 100644 --- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c @@ -629,6 +629,10 @@ static void axienet_start_xmit_done(struct net_device *ndev) ndev->stats.tx_packets += packets; ndev->stats.tx_bytes += size; + + /* Matches barrier in axienet_start_xmit */ + smp_mb(); + netif_wake_queue(ndev); } @@ -684,9 +688,19 @@ static inline int axienet_check_tx_bd_space(struct axienet_local *lp, cur_p = &lp->tx_bd_v[lp->tx_bd_tail]; if (axienet_check_tx_bd_space(lp, num_frag)) { - if (!netif_queue_stopped(ndev)) - netif_stop_queue(ndev); - return NETDEV_TX_BUSY; + if (netif_queue_stopped(ndev)) + return NETDEV_TX_BUSY; + + netif_stop_queue(ndev); + + /* Matches barrier in axienet_start_xmit_done */ + smp_mb(); + + /* Space might have just been freed - check again */ + if (axienet_check_tx_bd_space(lp, num_frag)) + return NETDEV_TX_BUSY; + + netif_wake_queue(ndev); } if (skb->ip_summed == CHECKSUM_PARTIAL) {