[PATCH] hv_netvsc: remove ndo_poll_controller

[Tim Gardner]

From: Stephen Hemminger <stephen at networkplumber.org>

BugLink: https://bugs.launchpad.net/bugs/1924314

Similar to other patches from ERic.

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.

In netvsc driver it uses NAPI for TX completions. The default
poll_napi will do this for us now and avoid the capture.

Signed-off-by: Stephen Hemminger <sthemmin at microsoft.com>
Cc: Haiyang Zhang <haiyangz at microsoft.com>
Cc: Eric Dumazet <edumazet at google.com>
Reviewed-by: Haiyang Zhang <haiyangz at microsoft.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(backported from commit 2a7f8c3b1d3feedee3aa319ac220cbde3725b5d5)
[rtg - minor context adjustment]
Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
---
 drivers/net/hyperv/netvsc_drv.c | 23 -----------------------
 1 file changed, 23 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 087c05eefdf49..e5c8769a3d399 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -1649,26 +1649,6 @@ netvsc_set_rxnfc(struct net_device *ndev, struct ethtool_rxnfc *info)
 	return -EOPNOTSUPP;
 }
 
-#ifdef CONFIG_NET_POLL_CONTROLLER
-static void netvsc_poll_controller(struct net_device *dev)
-{
-	struct net_device_context *ndc = netdev_priv(dev);
-	struct netvsc_device *ndev;
-	int i;
-
-	rcu_read_lock();
-	ndev = rcu_dereference(ndc->nvdev);
-	if (ndev) {
-		for (i = 0; i < ndev->num_chn; i++) {
-			struct netvsc_channel *nvchan = &ndev->chan_table[i];
-
-			napi_schedule(&nvchan->napi);
-		}
-	}
-	rcu_read_unlock();
-}
-#endif
-
 static u32 netvsc_get_rxfh_key_size(struct net_device *dev)
 {
 	return NETVSC_HASH_KEYLEN;
@@ -1875,9 +1855,6 @@ static const struct net_device_ops device_ops = {
 	.ndo_select_queue =		netvsc_select_queue,
 	.ndo_get_stats64 =		netvsc_get_stats64,
 	.ndo_bpf =			netvsc_bpf,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller =		netvsc_poll_controller,
-#endif
 };
 
 /*
-- 
2.17.1