netdev - [PATCH 4/4] net/mlx4_en: Use atomic counter to decide when queue is full

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 21 Jun 2012 12:19:17 +0300
From:	Yevgeny Petrilin <yevgenyp@...lanox.co.il>
To:	davem@...emloft.net
Cc:	netdev@...r.kernel.org, Yevgeny Petrilin <yevgenyp@...lanox.co.il>
Subject: [PATCH 4/4] net/mlx4_en: Use atomic counter to decide when queue is full

The Transmit and transmit completion flows execute from different contexts,
which are not synchronized. Hence naive reading the of consumer index might
give wrong value by the time it is being used, That could lead to a state of transmit timeout.
Fix that by using atomic variable to maintain that index.

Signed-off-by: Yevgeny Petrilin <yevgenyp@...lanox.co.il>
---
 drivers/net/ethernet/mellanox/mlx4/en_tx.c   |   16 ++++++++--------
 drivers/net/ethernet/mellanox/mlx4/mlx4_en.h |    1 +
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index 019d856..f4b4703 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -165,6 +165,7 @@ int mlx4_en_activate_tx_ring(struct mlx4_en_priv *priv,
 	ring->last_nr_txbb = 1;
 	ring->poll_cnt = 0;
 	ring->blocked = 0;
+	atomic_set(&ring->inflight, 0);
 	memset(ring->tx_info, 0, ring->size * sizeof(struct mlx4_en_tx_info));
 	memset(ring->buf, 0, ring->buf_size);
 
@@ -364,15 +365,13 @@ static void mlx4_en_process_tx_cq(struct net_device *dev, struct mlx4_en_cq *cq)
 	wmb();
 	ring->cons += txbbs_skipped;
 	netdev_tx_completed_queue(ring->tx_queue, packets, bytes);
+	atomic_sub(txbbs_skipped, &ring->inflight);
 
 	/* Wakeup Tx queue if this ring stopped it */
-	if (unlikely(ring->blocked)) {
-		if ((u32) (ring->prod - ring->cons) <=
-		     ring->size - HEADROOM - MAX_DESC_TXBBS) {
-			ring->blocked = 0;
-			netif_tx_wake_queue(ring->tx_queue);
-			priv->port_stats.wake_queue++;
-		}
+	if (unlikely(ring->blocked && txbbs_skipped > 0)) {
+		ring->blocked = 0;
+		netif_tx_wake_queue(ring->tx_queue);
+		priv->port_stats.wake_queue++;
 	}
 }
 
@@ -588,7 +587,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 		vlan_tag = vlan_tx_tag_get(skb);
 
 	/* Check available TXBBs And 2K spare for prefetch */
-	if (unlikely(((int)(ring->prod - ring->cons)) >
+	if (unlikely(atomic_read(&ring->inflight) >
 		     ring->size - HEADROOM - MAX_DESC_TXBBS)) {
 		/* every full Tx ring stops queue */
 		netif_tx_stop_queue(ring->tx_queue);
@@ -710,6 +709,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 	}
 
 	ring->prod += nr_txbb;
+	atomic_add(nr_txbb, &ring->inflight);
 
 	/* If we used a bounce buffer then copy descriptor back into place */
 	if (bounce)
diff --git a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
index 225c20d..6a8a69d 100644
--- a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
+++ b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
@@ -257,6 +257,7 @@ struct mlx4_en_tx_ring {
 	struct mlx4_bf bf;
 	bool bf_enabled;
 	struct netdev_queue *tx_queue;
+	atomic_t inflight;
 };
 
 struct mlx4_en_rx_desc {
-- 
1.7.1

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html