From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 01B101ED38 for ; Tue, 25 Jul 2023 11:27:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7945BC433C8; Tue, 25 Jul 2023 11:27:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1690284458; bh=oFvLVnOjlOMkQy5i+xTqESVIpafWkJb4rw1tGyNWUhA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SioEwWGK64pC7sHZ6o1LSIJjtPIZE5tnAELekHc6hNmejoM7z3jjz1dlgVAiEt8av aDqDvh8LRskXU9cjAbAzX1i1aHdSo/rxF1SqQR3NxFfMZWlU+KWhjL0pd4/IzNZFX1 +ptbmFAlis92bcBUDsHpDpHCAtQH3hpAB04uVV0I= 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 5.10 363/509] igc: Fix inserting of empty frame for launchtime Date: Tue, 25 Jul 2023 12:45:02 +0200 Message-ID: <20230725104610.340790809@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230725104553.588743331@linuxfoundation.org> References: <20230725104553.588743331@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 051b1048eb41b..631ce793fb2ec 100644 --- a/drivers/net/ethernet/intel/igc/igc_main.c +++ b/drivers/net/ethernet/intel/igc/igc_main.c @@ -918,7 +918,7 @@ 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