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 E57AAEB64DC for ; Fri, 21 Jul 2023 16:13:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232462AbjGUQNy (ORCPT ); Fri, 21 Jul 2023 12:13:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39092 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232220AbjGUQNe (ORCPT ); Fri, 21 Jul 2023 12:13:34 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4191C4491 for ; Fri, 21 Jul 2023 09:13:08 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 23BAE61D30 for ; Fri, 21 Jul 2023 16:13:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3203FC433C8; Fri, 21 Jul 2023 16:13:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1689955987; bh=N7opixyqbVsy3FDh/oxoCuuVY/2WOjnKgbDVr222iQk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2Hlg8H4uN7T0QYzDOQmMFWmeQzNNCAbAzCIvLAoqXEaB5gBECX4N6FBLa5tl9O8Xe pi02SOYCDO9wLShFvjBqtCx93hiirclim+W2PUK0/3B4QkWvPenAGfZVfoO/jYadXt 3yFlrFQ53slajQGB5tqNQnmrx+0fzBkCU1cuLTWk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Florian Kauer , Kurt Kanzenbach , Naama Meir , Tony Nguyen , Sasha Levin Subject: [PATCH 6.4 077/292] igc: Fix inserting of empty frame for launchtime Date: Fri, 21 Jul 2023 18:03:06 +0200 Message-ID: <20230721160532.114558644@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230721160528.800311148@linuxfoundation.org> References: <20230721160528.800311148@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Florian Kauer [ Upstream commit 0bcc62858d6ba62cbade957d69745e6adeed5f3d ] The insertion of an empty frame was introduced with commit db0b124f02ba ("igc: Enhance Qbv scheduling by using first flag bit") in order to ensure that the current cycle has at least one packet if there is some packet to be scheduled for the next cycle. However, the current implementation does not properly check if a packet is already scheduled for the current cycle. Currently, an empty packet is always inserted if and only if txtime >= end_of_cycle && txtime > last_tx_cycle but since last_tx_cycle is always either the end of the current cycle (end_of_cycle) or the end of a previous cycle, the second part (txtime > last_tx_cycle) is always true unless txtime == last_tx_cycle. What actually needs to be checked here is if the last_tx_cycle was already written within the current cycle, so an empty frame should only be inserted if and only if txtime >= end_of_cycle && end_of_cycle > last_tx_cycle. This patch does not only avoid an unnecessary insertion, but it can actually be harmful to insert an empty packet if packets are already scheduled in the current cycle, because it can lead to a situation where the empty packet is actually processed as the first packet in the upcoming cycle shifting the packet with the first_flag even one cycle into the future, finally leading to a TX hang. The TX hang can be reproduced on a i225 with: sudo tc qdisc replace dev enp1s0 parent root handle 100 taprio \ num_tc 1 \ map 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \ queues 1@0 \ base-time 0 \ sched-entry S 01 300000 \ flags 0x1 \ txtime-delay 500000 \ clockid CLOCK_TAI sudo tc qdisc replace dev enp1s0 parent 100:1 etf \ clockid CLOCK_TAI \ delta 500000 \ offload \ skip_sock_check and traffic generator sudo trafgen -i traffic.cfg -o enp1s0 --cpp -n0 -q -t1400ns with traffic.cfg #define ETH_P_IP 0x0800 { /* Ethernet Header */ 0x30, 0x1f, 0x9a, 0xd0, 0xf0, 0x0e, # MAC Dest - adapt as needed 0x24, 0x5e, 0xbe, 0x57, 0x2e, 0x36, # MAC Src - adapt as needed const16(ETH_P_IP), /* IPv4 Header */ 0b01000101, 0, # IPv4 version, IHL, TOS const16(1028), # IPv4 total length (UDP length + 20 bytes (IP header)) const16(2), # IPv4 ident 0b01000000, 0, # IPv4 flags, fragmentation off 64, # IPv4 TTL 17, # Protocol UDP csumip(14, 33), # IPv4 checksum /* UDP Header */ 10, 0, 48, 1, # IP Src - adapt as needed 10, 0, 48, 10, # IP Dest - adapt as needed const16(5555), # UDP Src Port const16(6666), # UDP Dest Port const16(1008), # UDP length (UDP header 8 bytes + payload length) csumudp(14, 34), # UDP checksum /* Payload */ fill('W', 1000), } and the observed message with that is for example igc 0000:01:00.0 enp1s0: Detected Tx Unit Hang Tx Queue <0> TDH <32> TDT <3c> next_to_use <3c> next_to_clean <32> buffer_info[next_to_clean] time_stamp next_to_watch <00000000632a1828> jiffies desc.status <1048000> Fixes: db0b124f02ba ("igc: Enhance Qbv scheduling by using first flag bit") Signed-off-by: Florian Kauer Reviewed-by: Kurt Kanzenbach Tested-by: Naama Meir Signed-off-by: Tony Nguyen Signed-off-by: Sasha Levin --- drivers/net/ethernet/intel/igc/igc_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c index 96a2f6e6f6b8a..44aa4342cbbb5 100644 --- a/drivers/net/ethernet/intel/igc/igc_main.c +++ b/drivers/net/ethernet/intel/igc/igc_main.c @@ -1029,7 +1029,7 @@ static __le32 igc_tx_launchtime(struct igc_ring *ring, ktime_t txtime, *first_flag = true; ring->last_ff_cycle = baset_est; - if (ktime_compare(txtime, ring->last_tx_cycle) > 0) + if (ktime_compare(end_of_cycle, ring->last_tx_cycle) > 0) *insert_empty = true; } } -- 2.39.2