netdev - [PATCH net 10/15] mlx4: remove ndo_poll

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Message-Id: <20180921222752.101307-11-edumazet@google.com>
Date:   Fri, 21 Sep 2018 15:27:47 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Michael Chan <michael.chan@...adcom.com>,
        Ariel Elior <ariel.elior@...ium.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Song Liu <songliubraving@...com>,
        Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>
Subject: [PATCH net 10/15] mlx4: remove ndo_poll_controller

As diagnosed by Song Liu, ndo_poll_controller() can
be very dangerous on loaded hosts, since the cpu
calling ndo_poll_controller() might steal all NAPI
contexts (for all RX/TX queues of the NIC). This capture
can last for unlimited amount of time, since one
cpu is generally not able to drain all the queues under load.

mlx4 uses NAPI for TX completions, so we better let core
networking stack call the napi->poll() to avoid the capture.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Tariq Toukan <tariqt@...lanox.com>
---
 .../net/ethernet/mellanox/mlx4/en_netdev.c    | 20 -------------------
 1 file changed, 20 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
index 6785661d1a72627d7cc6895359e0ece284577d96..fe49384eba48cb3f75bd33f5bfb9cf1fa15af791 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
@@ -1286,20 +1286,6 @@ static void mlx4_en_do_set_rx_mode(struct work_struct *work)
 	mutex_unlock(&mdev->state_lock);
 }
 
-#ifdef CONFIG_NET_POLL_CONTROLLER
-static void mlx4_en_netpoll(struct net_device *dev)
-{
-	struct mlx4_en_priv *priv = netdev_priv(dev);
-	struct mlx4_en_cq *cq;
-	int i;
-
-	for (i = 0; i < priv->tx_ring_num[TX]; i++) {
-		cq = priv->tx_cq[TX][i];
-		napi_schedule(&cq->napi);
-	}
-}
-#endif
-
 static int mlx4_en_set_rss_steer_rules(struct mlx4_en_priv *priv)
 {
 	u64 reg_id;
@@ -2946,9 +2932,6 @@ static const struct net_device_ops mlx4_netdev_ops = {
 	.ndo_tx_timeout		= mlx4_en_tx_timeout,
 	.ndo_vlan_rx_add_vid	= mlx4_en_vlan_rx_add_vid,
 	.ndo_vlan_rx_kill_vid	= mlx4_en_vlan_rx_kill_vid,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller	= mlx4_en_netpoll,
-#endif
 	.ndo_set_features	= mlx4_en_set_features,
 	.ndo_fix_features	= mlx4_en_fix_features,
 	.ndo_setup_tc		= __mlx4_en_setup_tc,
@@ -2983,9 +2966,6 @@ static const struct net_device_ops mlx4_netdev_ops_master = {
 	.ndo_set_vf_link_state	= mlx4_en_set_vf_link_state,
 	.ndo_get_vf_stats       = mlx4_en_get_vf_stats,
 	.ndo_get_vf_config	= mlx4_en_get_vf_config,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller	= mlx4_en_netpoll,
-#endif
 	.ndo_set_features	= mlx4_en_set_features,
 	.ndo_fix_features	= mlx4_en_fix_features,
 	.ndo_setup_tc		= __mlx4_en_setup_tc,
-- 
2.19.0.444.g18242da7ef-goog