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authorPaolo Abeni <pabeni@redhat.com>2023-04-13 14:30:22 +0300
committerPaolo Abeni <pabeni@redhat.com>2023-04-13 14:30:22 +0300
commit4033eaa68af6e3e9a8ec3819a9369d29aee8a2c4 (patch)
tree9269f15ccde69661ceecafbb02bac705b14d7b3f
parent21cdc87fa9d8e0f0104db5499a16e2be1f53516a (diff)
parent9a714997386ba110154dc444cdd0279f966151b2 (diff)
downloadlinux-4033eaa68af6e3e9a8ec3819a9369d29aee8a2c4.tar.xz
Merge branch 'net-use-read_once-write_once-for-ring-index-accesses'
Jakub Kicinski says: ==================== net: use READ_ONCE/WRITE_ONCE for ring index accesses Small follow up to the lockless ring stop/start macros. Update the doc and the drivers suggested by Eric: https://lore.kernel.org/all/CANn89iJrBGSybMX1FqrhCEMWT3Nnz2=2+aStsbbwpWzKHjk51g@mail.gmail.com/ ==================== Link: https://lore.kernel.org/r/20230412015038.674023-1-kuba@kernel.org Signed-off-by: Paolo Abeni <pabeni@redhat.com>
-rw-r--r--Documentation/networking/driver.rst61
-rw-r--r--drivers/net/ethernet/broadcom/bnxt/bnxt.c6
-rw-r--r--drivers/net/ethernet/broadcom/bnxt/bnxt.h9
-rw-r--r--drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c6
-rw-r--r--drivers/net/ethernet/mellanox/mlx4/en_tx.c8
5 files changed, 42 insertions, 48 deletions
diff --git a/Documentation/networking/driver.rst b/Documentation/networking/driver.rst
index 4071f2c00f8b..4f5dfa9c022e 100644
--- a/Documentation/networking/driver.rst
+++ b/Documentation/networking/driver.rst
@@ -47,30 +47,43 @@ for a driver implementing scatter-gather this means:
.. code-block:: c
+ static u32 drv_tx_avail(struct drv_ring *dr)
+ {
+ u32 used = READ_ONCE(dr->prod) - READ_ONCE(dr->cons);
+
+ return dr->tx_ring_size - (used & bp->tx_ring_mask);
+ }
+
static netdev_tx_t drv_hard_start_xmit(struct sk_buff *skb,
struct net_device *dev)
{
struct drv *dp = netdev_priv(dev);
+ struct netdev_queue *txq;
+ struct drv_ring *dr;
+ int idx;
+
+ idx = skb_get_queue_mapping(skb);
+ dr = dp->tx_rings[idx];
+ txq = netdev_get_tx_queue(dev, idx);
- lock_tx(dp);
//...
- /* This is a hard error log it. */
- if (TX_BUFFS_AVAIL(dp) <= (skb_shinfo(skb)->nr_frags + 1)) {
+ /* This should be a very rare race - log it. */
+ if (drv_tx_avail(dr) <= skb_shinfo(skb)->nr_frags + 1) {
netif_stop_queue(dev);
- unlock_tx(dp);
- printk(KERN_ERR PFX "%s: BUG! Tx Ring full when queue awake!\n",
- dev->name);
+ netdev_warn(dev, "Tx Ring full when queue awake!\n");
return NETDEV_TX_BUSY;
}
//... queue packet to card ...
- //... update tx consumer index ...
- if (TX_BUFFS_AVAIL(dp) <= (MAX_SKB_FRAGS + 1))
- netif_stop_queue(dev);
+ netdev_tx_sent_queue(txq, skb->len);
+
+ //... update tx producer index using WRITE_ONCE() ...
+
+ if (!netif_txq_maybe_stop(txq, drv_tx_avail(dr),
+ MAX_SKB_FRAGS + 1, 2 * MAX_SKB_FRAGS))
+ dr->stats.stopped++;
- //...
- unlock_tx(dp);
//...
return NETDEV_TX_OK;
}
@@ -79,30 +92,10 @@ And then at the end of your TX reclamation event handling:
.. code-block:: c
- if (netif_queue_stopped(dp->dev) &&
- TX_BUFFS_AVAIL(dp) > (MAX_SKB_FRAGS + 1))
- netif_wake_queue(dp->dev);
-
-For a non-scatter-gather supporting card, the three tests simply become:
-
-.. code-block:: c
-
- /* This is a hard error log it. */
- if (TX_BUFFS_AVAIL(dp) <= 0)
-
-and:
-
-.. code-block:: c
-
- if (TX_BUFFS_AVAIL(dp) == 0)
-
-and:
-
-.. code-block:: c
+ //... update tx consumer index using WRITE_ONCE() ...
- if (netif_queue_stopped(dp->dev) &&
- TX_BUFFS_AVAIL(dp) > 0)
- netif_wake_queue(dp->dev);
+ netif_txq_completed_wake(txq, cmpl_pkts, cmpl_bytes,
+ drv_tx_avail(dr), 2 * MAX_SKB_FRAGS);
Lockless queue stop / wake helper macros
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index f7602d8d79e3..92289ab2f34a 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -472,7 +472,7 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev)
prod = NEXT_TX(prod);
tx_push->doorbell =
cpu_to_le32(DB_KEY_TX_PUSH | DB_LONG_TX_PUSH | prod);
- txr->tx_prod = prod;
+ WRITE_ONCE(txr->tx_prod, prod);
tx_buf->is_push = 1;
netdev_tx_sent_queue(txq, skb->len);
@@ -583,7 +583,7 @@ normal_tx:
wmb();
prod = NEXT_TX(prod);
- txr->tx_prod = prod;
+ WRITE_ONCE(txr->tx_prod, prod);
if (!netdev_xmit_more() || netif_xmit_stopped(txq))
bnxt_txr_db_kick(bp, txr, prod);
@@ -688,7 +688,7 @@ next_tx_int:
dev_kfree_skb_any(skb);
}
- txr->tx_cons = cons;
+ WRITE_ONCE(txr->tx_cons, cons);
__netif_txq_completed_wake(txq, nr_pkts, tx_bytes,
bnxt_tx_avail(bp, txr), bp->tx_wake_thresh,
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
index 18cac98ba58e..080e73496066 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
@@ -2231,13 +2231,12 @@ struct bnxt {
#define SFF_MODULE_ID_QSFP28 0x11
#define BNXT_MAX_PHY_I2C_RESP_SIZE 64
-static inline u32 bnxt_tx_avail(struct bnxt *bp, struct bnxt_tx_ring_info *txr)
+static inline u32 bnxt_tx_avail(struct bnxt *bp,
+ const struct bnxt_tx_ring_info *txr)
{
- /* Tell compiler to fetch tx indices from memory. */
- barrier();
+ u32 used = READ_ONCE(txr->tx_prod) - READ_ONCE(txr->tx_cons);
- return bp->tx_ring_size -
- ((txr->tx_prod - txr->tx_cons) & bp->tx_ring_mask);
+ return bp->tx_ring_size - (used & bp->tx_ring_mask);
}
static inline void bnxt_writeq(struct bnxt *bp, u64 val,
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
index 5843c93b1711..4efa5fe6972b 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
@@ -64,7 +64,7 @@ struct bnxt_sw_tx_bd *bnxt_xmit_bd(struct bnxt *bp,
int frag_len;
prod = NEXT_TX(prod);
- txr->tx_prod = prod;
+ WRITE_ONCE(txr->tx_prod, prod);
/* first fill up the first buffer */
frag_tx_buf = &txr->tx_buf_ring[prod];
@@ -94,7 +94,7 @@ struct bnxt_sw_tx_bd *bnxt_xmit_bd(struct bnxt *bp,
/* Sync TX BD */
wmb();
prod = NEXT_TX(prod);
- txr->tx_prod = prod;
+ WRITE_ONCE(txr->tx_prod, prod);
return tx_buf;
}
@@ -161,7 +161,7 @@ void bnxt_tx_int_xdp(struct bnxt *bp, struct bnxt_napi *bnapi, int nr_pkts)
}
tx_cons = NEXT_TX(tx_cons);
}
- txr->tx_cons = tx_cons;
+ WRITE_ONCE(txr->tx_cons, tx_cons);
if (rx_doorbell_needed) {
tx_buf = &txr->tx_buf_ring[last_tx_cons];
bnxt_db_write(bp, &rxr->rx_db, tx_buf->rx_prod);
diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index 2f79378fbf6e..65cb63f6c465 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -228,7 +228,9 @@ void mlx4_en_deactivate_tx_ring(struct mlx4_en_priv *priv,
static inline bool mlx4_en_is_tx_ring_full(struct mlx4_en_tx_ring *ring)
{
- return ring->prod - ring->cons > ring->full_size;
+ u32 used = READ_ONCE(ring->prod) - READ_ONCE(ring->cons);
+
+ return used > ring->full_size;
}
static void mlx4_en_stamp_wqe(struct mlx4_en_priv *priv,
@@ -1083,7 +1085,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
op_own |= cpu_to_be32(MLX4_WQE_CTRL_IIP);
}
- ring->prod += nr_txbb;
+ WRITE_ONCE(ring->prod, ring->prod + nr_txbb);
/* If we used a bounce buffer then copy descriptor back into place */
if (unlikely(bounce))
@@ -1214,7 +1216,7 @@ netdev_tx_t mlx4_en_xmit_frame(struct mlx4_en_rx_ring *rx_ring,
rx_ring->xdp_tx++;
- ring->prod += MLX4_EN_XDP_TX_NRTXBB;
+ WRITE_ONCE(ring->prod, ring->prod + MLX4_EN_XDP_TX_NRTXBB);
/* Ensure new descriptor hits memory
* before setting ownership of this descriptor to HW