[4.2.y-ckt stable] Patch "net/mlx4_en: fix spurious timestamping callbacks" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    net/mlx4_en: fix spurious timestamping callbacks

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    https://git.launchpad.net/~canonical-kernel/linux/+git/linux-stable-ckt/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt10.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 46f59986f54890458ad379562d77015bb9e6a540 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet at google.com>
Date: Sat, 23 Apr 2016 11:35:46 -0700
Subject: net/mlx4_en: fix spurious timestamping callbacks

commit fc96256c906362e845d848d0f6a6354450059e81 upstream.

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 at google.com>
Cc: Willem de Bruijn <willemb at google.com>
Reviewed-by: Eran Ben Elisha <eranbe at mellanox.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 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 c10d98f..a1b4301 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -400,7 +400,6 @@ static bool mlx4_en_process_tx_cq(struct net_device *dev,
 	u32 packets = 0;
 	u32 bytes = 0;
 	int factor = priv->cqe_factor;
-	u64 timestamp = 0;
 	int done = 0;
 	int budget = priv->tx_work_limit;
 	u32 last_nr_txbb;
@@ -440,9 +439,12 @@ static bool mlx4_en_process_tx_cq(struct net_device *dev,
 		new_index = be16_to_cpu(cqe->wqe_index) & size_mask;

 		do {
+			u64 timestamp = 0;
+
 			txbbs_skipped += last_nr_txbb;
 			ring_index = (ring_index + 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 */
--
2.7.4