Subject: [net 09/10] net/mlx5e: Do not produce metadata freelist entries in Tx port ts WQE xmit

From: Saeed Mahameed <[email-masked]>
Date: Tue, 26 Mar 2024 07:46:45 -0700

From: Rahul Rameshbabu <[email-masked]>

Free Tx port timestamping metadata entries in the NAPI poll context and
consume metadata enties in the WQE xmit path. Do not free a Tx port
timestamping metadata entry in the WQE xmit path even in the error path to
avoid a race between two metadata entry producers.

Fixes: 3178308ad4ca ("net/mlx5e: Make tx_port_ts logic resilient to out-of-order CQEs")
Signed-off-by: Rahul Rameshbabu <[email-masked]>
Reviewed-by: Tariq Toukan <[email-masked]>
Signed-off-by: Saeed Mahameed <[email-masked]>
---
 drivers/net/ethernet/mellanox/mlx5/core/en/ptp.h | 8 +++++++-
 drivers/net/ethernet/mellanox/mlx5/core/en_tx.c  | 7 +++----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/ptp.h b/drivers/net/ethernet/mellanox/mlx5/core/en/ptp.h
index 86f1854698b4..883c044852f1 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/ptp.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/ptp.h
@@ -95,9 +95,15 @@ static inline void mlx5e_ptp_metadata_fifo_push(struct mlx5e_ptp_metadata_fifo *
 }
 
 static inline u8
+mlx5e_ptp_metadata_fifo_peek(struct mlx5e_ptp_metadata_fifo *fifo)
+{
+	return fifo->data[fifo->mask & fifo->cc];
+}
+
+static inline void
 mlx5e_ptp_metadata_fifo_pop(struct mlx5e_ptp_metadata_fifo *fifo)
 {
-	return fifo->data[fifo->mask & fifo->cc++];
+	fifo->cc++;
 }
 
 static inline void
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
index 2fa076b23fbe..e21a3b4128ce 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
@@ -398,6 +398,8 @@ mlx5e_txwqe_complete(struct mlx5e_txqsq *sq, struct sk_buff *skb,
 		     (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP))) {
 		u8 metadata_index = be32_to_cpu(eseg->flow_table_metadata);
 
+		mlx5e_ptp_metadata_fifo_pop(&sq->ptpsq->metadata_freelist);
+
 		mlx5e_skb_cb_hwtstamp_init(skb);
 		mlx5e_ptp_metadata_map_put(&sq->ptpsq->metadata_map, skb,
 					   metadata_index);
@@ -496,9 +498,6 @@ mlx5e_sq_xmit_wqe(struct mlx5e_txqsq *sq, struct sk_buff *skb,
 
 err_drop:
 	stats->dropped++;
-	if (unlikely(sq->ptpsq && (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)))
-		mlx5e_ptp_metadata_fifo_push(&sq->ptpsq->metadata_freelist,
-					     be32_to_cpu(eseg->flow_table_metadata));
 	dev_kfree_skb_any(skb);
 	mlx5e_tx_flush(sq);
 }
@@ -657,7 +656,7 @@ static void mlx5e_cqe_ts_id_eseg(struct mlx5e_ptpsq *ptpsq, struct sk_buff *skb,
 {
 	if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP))
 		eseg->flow_table_metadata =
-			cpu_to_be32(mlx5e_ptp_metadata_fifo_pop(&ptpsq->metadata_freelist));
+			cpu_to_be32(mlx5e_ptp_metadata_fifo_peek(&ptpsq->metadata_freelist));
 }
 
 static void mlx5e_txwqe_build_eseg(struct mlx5e_priv *priv, struct mlx5e_txqsq *sq,
-- 
2.44.0