net: hns3: fix for TX queue not restarted problem

There is timing window between ring_space checking and
netif_stop_subqueue when transmiting a SKB, and the TX BD
cleaning may be executed during the time window, which may
caused TX queue not restarted problem.

This patch fixes it by rechecking the ring_space after
netif_stop_subqueue to make sure TX queue is restarted.

Also, the ring->next_to_clean is updated even when pkts is
zero, because all the TX BD cleaned may be non-SKB, so it
needs to check if TX queue need to be restarted.

Fixes: 76ad4f0ee747 ("net: hns3: Add support of HNS3 Ethernet Driver for hip08 SoC")
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
index ba0536802b1399181eb069d9949c14f428bb1e8b..e2730319bd433f7aa8d92e5c09ad88f477575e69 100644 (file)
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
@@ -1287,8 +1287,10 @@ static bool hns3_skb_need_linearized(struct sk_buff *skb, unsigned int *bd_size,
 }
 
 static int hns3_nic_maybe_stop_tx(struct hns3_enet_ring *ring,
+                                 struct net_device *netdev,
                                  struct sk_buff **out_skb)
 {
+       struct hns3_nic_priv *priv = netdev_priv(netdev);
        unsigned int bd_size[HNS3_MAX_TSO_BD_NUM + 1U];
        struct sk_buff *skb = *out_skb;
        unsigned int bd_num;
@@ -1320,10 +1322,23 @@ static int hns3_nic_maybe_stop_tx(struct hns3_enet_ring *ring,
        }
 
 out:
-       if (unlikely(ring_space(ring) < bd_num))
-               return -EBUSY;
+       if (likely(ring_space(ring) >= bd_num))
+               return bd_num;
 
-       return bd_num;
+       netif_stop_subqueue(netdev, ring->queue_index);
+       smp_mb(); /* Memory barrier before checking ring_space */
+
+       /* Start queue in case hns3_clean_tx_ring has just made room
+        * available and has not seen the queue stopped state performed
+        * by netif_stop_subqueue above.
+        */
+       if (ring_space(ring) >= bd_num && netif_carrier_ok(netdev) &&
+           !test_bit(HNS3_NIC_STATE_DOWN, &priv->state)) {
+               netif_start_subqueue(netdev, ring->queue_index);
+               return bd_num;
+       }
+
+       return -EBUSY;
 }
 
 static void hns3_clear_desc(struct hns3_enet_ring *ring, int next_to_use_orig)
@@ -1400,13 +1415,13 @@ netdev_tx_t hns3_nic_net_xmit(struct sk_buff *skb, struct net_device *netdev)
        /* Prefetch the data used later */
        prefetch(skb->data);
 
-       ret = hns3_nic_maybe_stop_tx(ring, &skb);
+       ret = hns3_nic_maybe_stop_tx(ring, netdev, &skb);
        if (unlikely(ret <= 0)) {
                if (ret == -EBUSY) {
                        u64_stats_update_begin(&ring->syncp);
                        ring->stats.tx_busy++;
                        u64_stats_update_end(&ring->syncp);
-                       goto out_net_tx_busy;
+                       return NETDEV_TX_BUSY;
                } else if (ret == -ENOMEM) {
                        u64_stats_update_begin(&ring->syncp);
                        ring->stats.sw_err_cnt++;
@@ -1457,12 +1472,6 @@ netdev_tx_t hns3_nic_net_xmit(struct sk_buff *skb, struct net_device *netdev)
 out_err_tx_ok:
        dev_kfree_skb_any(skb);
        return NETDEV_TX_OK;
-
-out_net_tx_busy:
-       netif_stop_subqueue(netdev, ring->queue_index);
-       smp_mb(); /* Commit all data before submit */
-
-       return NETDEV_TX_BUSY;
 }
 
 static int hns3_nic_net_set_mac_address(struct net_device *netdev, void *p)
@@ -2519,7 +2528,7 @@ void hns3_clean_tx_ring(struct hns3_enet_ring *ring)
        dev_queue = netdev_get_tx_queue(netdev, ring->tqp->tqp_index);
        netdev_tx_completed_queue(dev_queue, pkts, bytes);
 
-       if (unlikely(pkts && netif_carrier_ok(netdev) &&
+       if (unlikely(netif_carrier_ok(netdev) &&
                     ring_space(ring) > HNS3_MAX_TSO_BD_NUM)) {
                /* Make sure that anybody stopping the queue after this
                 * sees the new next_to_clean.