linux-kernel - [PATCH 3.12 66/76] net/mlx4_en: fix spurious timestamping callbacks

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Message-Id: <c3892a66d27533817184f85d8787ba2cb8df3c63.1463648873.git.jslaby@suse.cz>
Date:	Thu, 19 May 2016 11:08:28 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
	Willem de Bruijn <willemb@...gle.com>,
	"David S . Miller" <davem@...emloft.net>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 66/76] net/mlx4_en: fix spurious timestamping callbacks

From: Eric Dumazet <edumazet@...gle.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

[ Upstream commit fc96256c906362e845d848d0f6a6354450059e81 ]

When multiple skb are TX-completed in a row, we might incorrectly keep
a timestamp of a prior skb and cause extra work.

Fixes: ec693d47010e8 ("net/mlx4_en: Add HW timestamping (TS) support")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Willem de Bruijn <willemb@...gle.com>
Reviewed-by: Eran Ben Elisha <eranbe@...lanox.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/net/ethernet/mellanox/mlx4/en_tx.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index 0698c82d6ff1..3d3cd0f1adf8 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -343,7 +343,6 @@ static void mlx4_en_process_tx_cq(struct net_device *dev, struct mlx4_en_cq *cq)
 	u32 packets = 0;
 	u32 bytes = 0;
 	int factor = priv->cqe_factor;
-	u64 timestamp = 0;
 
 	if (!priv->port_up)
 		return;
@@ -375,9 +374,12 @@ static void mlx4_en_process_tx_cq(struct net_device *dev, struct mlx4_en_cq *cq)
 		new_index = be16_to_cpu(cqe->wqe_index) & size_mask;
 
 		do {
+			u64 timestamp = 0;
+
 			txbbs_skipped += ring->last_nr_txbb;
 			ring_index = (ring_index + ring->last_nr_txbb) & size_mask;
-			if (ring->tx_info[ring_index].ts_requested)
+
+			if (unlikely(ring->tx_info[ring_index].ts_requested))
 				timestamp = mlx4_en_get_cqe_ts(cqe);
 
 			/* free next descriptor */
-- 
2.8.2