Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757995AbcDHHuz (ORCPT ); Fri, 8 Apr 2016 03:50:55 -0400 Received: from caladan.dune.hu ([78.24.191.180]:36332 "EHLO arrakis.dune.hu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757935AbcDHHuv (ORCPT ); Fri, 8 Apr 2016 03:50:51 -0400 From: John Crispin To: "David S. Miller" Cc: Felix Fietkau , Matthias Brugger , =?UTF-8?q?Sean=20Wang=20=28=E7=8E=8B=E5=BF=97=E4=BA=98=29?= , netdev@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, John Crispin Subject: [PATCH V3 5/8] net: mediatek: fix TX locking Date: Fri, 8 Apr 2016 00:54:08 +0200 Message-Id: <1460069651-1234-6-git-send-email-blogic@openwrt.org> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1460069651-1234-1-git-send-email-blogic@openwrt.org> References: <1460069651-1234-1-git-send-email-blogic@openwrt.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3247 Lines: 96 Inside the TX path there is a lock inside the tx_map function. This is however too late. The patch moves the lock to the start of the xmit function right before the free count check of the DMA ring happens. If we do not do this, the code becomes racy leading to TX stalls and dropped packets. This happens as there are 2 netdevs running on the same physical DMA ring. Signed-off-by: John Crispin --- Changes in V3 * fix a typo in the comment drivers/net/ethernet/mediatek/mtk_eth_soc.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c index 4ebc42e..7b76075 100644 --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c @@ -536,7 +536,6 @@ static int mtk_tx_map(struct sk_buff *skb, struct net_device *dev, struct mtk_eth *eth = mac->hw; struct mtk_tx_dma *itxd, *txd; struct mtk_tx_buf *tx_buf; - unsigned long flags; dma_addr_t mapped_addr; unsigned int nr_frags; int i, n_desc = 1; @@ -568,11 +567,6 @@ static int mtk_tx_map(struct sk_buff *skb, struct net_device *dev, if (unlikely(dma_mapping_error(&dev->dev, mapped_addr))) return -ENOMEM; - /* normally we can rely on the stack not calling this more than once, - * however we have 2 queues running ont he same ring so we need to lock - * the ring access - */ - spin_lock_irqsave(ð->page_lock, flags); WRITE_ONCE(itxd->txd1, mapped_addr); tx_buf->flags |= MTK_TX_FLAGS_SINGLE0; dma_unmap_addr_set(tx_buf, dma_addr0, mapped_addr); @@ -632,8 +626,6 @@ static int mtk_tx_map(struct sk_buff *skb, struct net_device *dev, WRITE_ONCE(itxd->txd3, (TX_DMA_SWC | TX_DMA_PLEN0(skb_headlen(skb)) | (!nr_frags * TX_DMA_LS0))); - spin_unlock_irqrestore(ð->page_lock, flags); - netdev_sent_queue(dev, skb->len); skb_tx_timestamp(skb); @@ -661,8 +653,6 @@ err_dma: itxd = mtk_qdma_phys_to_virt(ring, itxd->txd2); } while (itxd != txd); - spin_unlock_irqrestore(ð->page_lock, flags); - return -ENOMEM; } @@ -712,14 +702,22 @@ static int mtk_start_xmit(struct sk_buff *skb, struct net_device *dev) struct mtk_eth *eth = mac->hw; struct mtk_tx_ring *ring = ð->tx_ring; struct net_device_stats *stats = &dev->stats; + unsigned long flags; bool gso = false; int tx_num; + /* normally we can rely on the stack not calling this more than once, + * however we have 2 queues running on the same ring so we need to lock + * the ring access + */ + spin_lock_irqsave(ð->page_lock, flags); + tx_num = mtk_cal_txd_req(skb); if (unlikely(atomic_read(&ring->free_count) <= tx_num)) { mtk_stop_queue(eth); netif_err(eth, tx_queued, dev, "Tx Ring full when queue awake!\n"); + spin_unlock_irqrestore(ð->page_lock, flags); return NETDEV_TX_BUSY; } @@ -747,10 +745,12 @@ static int mtk_start_xmit(struct sk_buff *skb, struct net_device *dev) ring->thresh)) mtk_wake_queue(eth); } + spin_unlock_irqrestore(ð->page_lock, flags); return NETDEV_TX_OK; drop: + spin_unlock_irqrestore(ð->page_lock, flags); stats->tx_dropped++; dev_kfree_skb(skb); return NETDEV_TX_OK; -- 1.7.10.4