Messages in this thread Patch in this message | | | From | Rob Herring <> | Subject | [PATCH 06/11] net: calxedaxgmac: fix race with tx queue stop/wake | Date | Mon, 26 Aug 2013 17:45:21 -0500 |
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From: Rob Herring <rob.herring@calxeda.com>
Since the xgmac transmit start and completion work locklessly, it is possible for xgmac_xmit to stop the tx queue after the xgmac_tx_complete has run resulting in the tx queue never being woken up. Fix this by ensuring that ring buffer index updates are visible and serialize the queue wake with netif_tx_lock.
The implementation used here was copied from drivers/net/ethernet/broadcom/tg3.c.
Signed-off-by: Rob Herring <rob.herring@calxeda.com> --- drivers/net/ethernet/calxeda/xgmac.c | 25 +++++++++++++++++++------ 1 file changed, 19 insertions(+), 6 deletions(-)
diff --git a/drivers/net/ethernet/calxeda/xgmac.c b/drivers/net/ethernet/calxeda/xgmac.c index f630855..cd5872c 100644 --- a/drivers/net/ethernet/calxeda/xgmac.c +++ b/drivers/net/ethernet/calxeda/xgmac.c @@ -410,6 +410,9 @@ struct xgmac_priv { #define dma_ring_space(h, t, s) CIRC_SPACE(h, t, s) #define dma_ring_cnt(h, t, s) CIRC_CNT(h, t, s) +#define tx_dma_ring_space(p) \ + dma_ring_space((p)->tx_head, (p)->tx_tail, DMA_TX_RING_SZ) + /* XGMAC Descriptor Access Helpers */ static inline void desc_set_buf_len(struct xgmac_dma_desc *p, u32 buf_sz) { @@ -886,9 +889,14 @@ static void xgmac_tx_complete(struct xgmac_priv *priv) priv->tx_tail = dma_ring_incr(entry, DMA_TX_RING_SZ); } - if (dma_ring_space(priv->tx_head, priv->tx_tail, DMA_TX_RING_SZ) > - MAX_SKB_FRAGS) - netif_wake_queue(priv->dev); + /* Ensure tx_tail is visible to xgmac_xmit */ + smp_mb(); + if (unlikely(netif_queue_stopped(priv->dev))) { + netif_tx_lock(priv->dev); + if (tx_dma_ring_space(priv) > MAX_SKB_FRAGS) + netif_wake_queue(priv->dev); + netif_tx_unlock(priv->dev); + } } static void xgmac_tx_timeout_work(struct work_struct *work) @@ -1125,10 +1133,15 @@ static netdev_tx_t xgmac_xmit(struct sk_buff *skb, struct net_device *dev) priv->tx_head = dma_ring_incr(entry, DMA_TX_RING_SZ); - if (dma_ring_space(priv->tx_head, priv->tx_tail, DMA_TX_RING_SZ) < - MAX_SKB_FRAGS) + /* Ensure tx_head update is visible to tx completion */ + smp_mb(); + if (unlikely(tx_dma_ring_space(priv) < MAX_SKB_FRAGS)) { netif_stop_queue(dev); - + /* Ensure netif_stop_queue is visible to tx completion */ + smp_mb(); + if (tx_dma_ring_space(priv) > MAX_SKB_FRAGS) + netif_wake_queue(dev); + } return NETDEV_TX_OK; } -- 1.8.1.2
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