netdev - [PATCH net 11/15] mlx5: remove ndo_poll

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Date:   Fri, 21 Sep 2018 15:27:48 -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 11/15] mlx5: 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.

mlx5 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: Saeed Mahameed <saeedm@...lanox.com>
---
 .../net/ethernet/mellanox/mlx5/core/en_main.c | 19 -------------------
 1 file changed, 19 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 5a7939e7019026aa9c08d4fba759f95cb0a813c5..54118b77dc1f6d478c5b08e7c01526dd3e5dc740 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -4315,22 +4315,6 @@ static int mlx5e_xdp(struct net_device *dev, struct netdev_bpf *xdp)
 	}
 }
 
-#ifdef CONFIG_NET_POLL_CONTROLLER
-/* Fake "interrupt" called by netpoll (eg netconsole) to send skbs without
- * reenabling interrupts.
- */
-static void mlx5e_netpoll(struct net_device *dev)
-{
-	struct mlx5e_priv *priv = netdev_priv(dev);
-	struct mlx5e_channels *chs = &priv->channels;
-
-	int i;
-
-	for (i = 0; i < chs->num; i++)
-		napi_schedule(&chs->c[i]->napi);
-}
-#endif
-
 static const struct net_device_ops mlx5e_netdev_ops = {
 	.ndo_open                = mlx5e_open,
 	.ndo_stop                = mlx5e_close,
@@ -4356,9 +4340,6 @@ static const struct net_device_ops mlx5e_netdev_ops = {
 #ifdef CONFIG_MLX5_EN_ARFS
 	.ndo_rx_flow_steer	 = mlx5e_rx_flow_steer,
 #endif
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller     = mlx5e_netpoll,
-#endif
 #ifdef CONFIG_MLX5_ESWITCH
 	/* SRIOV E-Switch NDOs */
 	.ndo_set_vf_mac          = mlx5e_set_vf_mac,
-- 
2.19.0.444.g18242da7ef-goog