netdev - [PATCH net 13/15] bnxt: remove ndo_poll

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Date:   Fri, 21 Sep 2018 15:27:50 -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 13/15] bnxt: 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.

bnxt 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: Michael Chan <michael.chan@...adcom.com>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c | 18 ------------------
 1 file changed, 18 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 177587f9c3f1e8560c16e2fc4e05b7edff4e0011..61957b0bbd8c9f46773ff26ac9d14759b96c3960 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -7672,21 +7672,6 @@ static void bnxt_tx_timeout(struct net_device *dev)
 	bnxt_queue_sp_work(bp);
 }
 
-#ifdef CONFIG_NET_POLL_CONTROLLER
-static void bnxt_poll_controller(struct net_device *dev)
-{
-	struct bnxt *bp = netdev_priv(dev);
-	int i;
-
-	/* Only process tx rings/combined rings in netpoll mode. */
-	for (i = 0; i < bp->tx_nr_rings; i++) {
-		struct bnxt_tx_ring_info *txr = &bp->tx_ring[i];
-
-		napi_schedule(&txr->bnapi->napi);
-	}
-}
-#endif
-
 static void bnxt_timer(struct timer_list *t)
 {
 	struct bnxt *bp = from_timer(bp, t, timer);
@@ -8519,9 +8504,6 @@ static const struct net_device_ops bnxt_netdev_ops = {
 	.ndo_set_vf_link_state	= bnxt_set_vf_link_state,
 	.ndo_set_vf_spoofchk	= bnxt_set_vf_spoofchk,
 	.ndo_set_vf_trust	= bnxt_set_vf_trust,
-#endif
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller	= bnxt_poll_controller,
 #endif
 	.ndo_setup_tc           = bnxt_setup_tc,
 #ifdef CONFIG_RFS_ACCEL
-- 
2.19.0.444.g18242da7ef-goog