From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754665AbdL1Rb1 (ORCPT ); Thu, 28 Dec 2017 12:31:27 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:58908 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754353AbdL1ROA (ORCPT ); Thu, 28 Dec 2017 12:14:00 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Marc Kleine-Budde" , "Wolfgang Grandegger" Date: Thu, 28 Dec 2017 17:05:44 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 130/204] can: gs_usb: fix busy loop if no more TX context is available In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.52-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Wolfgang Grandegger commit 97819f943063b622eca44d3644067c190dc75039 upstream. If sending messages with no cable connected, it quickly happens that there is no more TX context available. Then "gs_can_start_xmit()" returns with "NETDEV_TX_BUSY" and the upper layer does retry immediately keeping the CPU busy. To fix that issue, I moved "atomic_dec(&dev->active_tx_urbs)" from "gs_usb_xmit_callback()" to the TX done handling in "gs_usb_receive_bulk_callback()". Renaming "active_tx_urbs" to "active_tx_contexts" and moving it into "gs_[alloc|free]_tx_context()" would also make sense. Signed-off-by: Wolfgang Grandegger Signed-off-by: Marc Kleine-Budde Signed-off-by: Ben Hutchings --- drivers/net/can/usb/gs_usb.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) --- a/drivers/net/can/usb/gs_usb.c +++ b/drivers/net/can/usb/gs_usb.c @@ -356,6 +356,8 @@ static void gs_usb_recieve_bulk_callback gs_free_tx_context(txc); + atomic_dec(&dev->active_tx_urbs); + netif_wake_queue(netdev); } @@ -444,14 +446,6 @@ static void gs_usb_xmit_callback(struct urb->transfer_buffer_length, urb->transfer_buffer, urb->transfer_dma); - - atomic_dec(&dev->active_tx_urbs); - - if (!netif_device_present(netdev)) - return; - - if (netif_queue_stopped(netdev)) - netif_wake_queue(netdev); } static netdev_tx_t gs_can_start_xmit(struct sk_buff *skb, struct net_device *netdev)