netdev - [PATCH net 11/11] ibmvnic: remove ndo_poll

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Message-Id: <20180927163201.56609-12-edumazet@google.com>
Date:   Thu, 27 Sep 2018 09:32:01 -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>,
        Aviad Krawczyk <aviad.krawczyk@...wei.com>,
        Song Liu <songliubraving@...com>,
        Douglas Miller <dougmill@...ux.vnet.ibm.com>,
        Yisen Zhuang <yisen.zhuang@...wei.com>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Harish Patil <harish.patil@...ium.com>,
        Manish Chopra <manish.chopra@...ium.com>,
        Netanel Belgazal <netanel@...zon.com>,
        Solarflare linux maintainers <linux-net-drivers@...arflare.com>,
        Thomas Falcon <tlfalcon@...ux.vnet.ibm.com>,
        John Allen <jallen@...ux.vnet.ibm.com>
Subject: [PATCH net 11/11] ibmvnic: 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.

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

ibmvnic_netpoll_controller() was completely wrong anyway,
as it was scheduling NAPI to service RX queues (instead of TX),
so I doubt netpoll ever worked on this driver.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Thomas Falcon <tlfalcon@...ux.vnet.ibm.com>
Cc: John Allen <jallen@...ux.vnet.ibm.com>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 16 ----------------
 1 file changed, 16 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 4f0daf67b18df2dcf11d7a406ebc1982e0fee466..699ef942b615c3a22053ba1419399317a6642cfa 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -2207,19 +2207,6 @@ static int ibmvnic_poll(struct napi_struct *napi, int budget)
 	return frames_processed;
 }
 
-#ifdef CONFIG_NET_POLL_CONTROLLER
-static void ibmvnic_netpoll_controller(struct net_device *dev)
-{
-	struct ibmvnic_adapter *adapter = netdev_priv(dev);
-	int i;
-
-	replenish_pools(netdev_priv(dev));
-	for (i = 0; i < adapter->req_rx_queues; i++)
-		ibmvnic_interrupt_rx(adapter->rx_scrq[i]->irq,
-				     adapter->rx_scrq[i]);
-}
-#endif
-
 static int wait_for_reset(struct ibmvnic_adapter *adapter)
 {
 	int rc, ret;
@@ -2292,9 +2279,6 @@ static const struct net_device_ops ibmvnic_netdev_ops = {
 	.ndo_set_mac_address	= ibmvnic_set_mac,
 	.ndo_validate_addr	= eth_validate_addr,
 	.ndo_tx_timeout		= ibmvnic_tx_timeout,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller	= ibmvnic_netpoll_controller,
-#endif
 	.ndo_change_mtu		= ibmvnic_change_mtu,
 	.ndo_features_check     = ibmvnic_features_check,
 };
-- 
2.19.0.605.g01d371f741-goog