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[2003:ea:8f23:2800:f440:c2bc:7fec:c7f5]) by smtp.googlemail.com with ESMTPSA id t23sm14077293wmn.4.2020.11.14.12.50.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 14 Nov 2020 12:50:04 -0800 (PST) From: Heiner Kallweit To: Jakub Kicinski , David Miller , Realtek linux nic maintainers Cc: "netdev@vger.kernel.org" Subject: [PATCH net-next] r8169: improve rtl8169_start_xmit Message-ID: <80085451-3eaf-507a-c7c0-08d607c46fbc@gmail.com> Date: Sat, 14 Nov 2020 21:49:53 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.4.3 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Improve the following in rtl8169_start_xmit: - tp->cur_tx can be accessed in parallel by rtl_tx(), therefore annotate the race by using WRITE_ONCE - avoid checking stop_queue a second time by moving the doorbell check - netif_stop_queue() uses atomic operation set_bit() that includes a full memory barrier on some platforms, therefore use smp_mb__after_atomic to avoid overhead Signed-off-by: Heiner Kallweit --- drivers/net/ethernet/realtek/r8169_main.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c index 8910e900e..940fc6590 100644 --- a/drivers/net/ethernet/realtek/r8169_main.c +++ b/drivers/net/ethernet/realtek/r8169_main.c @@ -4226,7 +4226,7 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb, /* rtl_tx needs to see descriptor changes before updated tp->cur_tx */ smp_wmb(); - tp->cur_tx += frags + 1; + WRITE_ONCE(tp->cur_tx, tp->cur_tx + frags + 1); stop_queue = !rtl_tx_slots_avail(tp, MAX_SKB_FRAGS); if (unlikely(stop_queue)) { @@ -4235,13 +4235,6 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb, */ smp_wmb(); netif_stop_queue(dev); - door_bell = true; - } - - if (door_bell) - rtl8169_doorbell(tp); - - if (unlikely(stop_queue)) { /* Sync with rtl_tx: * - publish queue status and cur_tx ring index (write barrier) * - refresh dirty_tx ring index (read barrier). @@ -4249,11 +4242,15 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb, * status and forget to wake up queue, a racing rtl_tx thread * can't. */ - smp_mb(); + smp_mb__after_atomic(); if (rtl_tx_slots_avail(tp, MAX_SKB_FRAGS)) netif_start_queue(dev); + door_bell = true; } + if (door_bell) + rtl8169_doorbell(tp); + return NETDEV_TX_OK; err_dma_1: