From: Eric Dumazet <edumazet@google.com>
Date: Thu, 27 Sep 2018 09:31:59 -0700
Subject: sfc: remove ndo_poll_controller
Patch-mainline: v4.19-rc7
Git-commit: 9447a10ff607debe5e30cc438fb56925a559b9d9
References: bsc#1105555 FATE#326117

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.

sfc 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@google.com>
Cc: Edward Cree <ecree@solarflare.com>
Cc: Bert Kenward <bkenward@solarflare.com>
Cc: Solarflare linux maintainers <linux-net-drivers@solarflare.com>
Acked-By: Bert Kenward <bkenward@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/sfc/efx.c |   26 --------------------------
 1 file changed, 26 deletions(-)

--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -2209,29 +2209,6 @@ static void efx_fini_napi(struct efx_nic
 
 /**************************************************************************
  *
- * Kernel netpoll interface
- *
- *************************************************************************/
-
-#ifdef CONFIG_NET_POLL_CONTROLLER
-
-/* Although in the common case interrupts will be disabled, this is not
- * guaranteed. However, all our work happens inside the NAPI callback,
- * so no locking is required.
- */
-static void efx_netpoll(struct net_device *net_dev)
-{
-	struct efx_nic *efx = netdev_priv(net_dev);
-	struct efx_channel *channel;
-
-	efx_for_each_channel(channel, efx)
-		efx_schedule_channel(channel);
-}
-
-#endif
-
-/**************************************************************************
- *
  * Kernel net device interface
  *
  *************************************************************************/
@@ -2510,9 +2487,6 @@ static const struct net_device_ops efx_n
 #endif
 	.ndo_get_phys_port_id   = efx_get_phys_port_id,
 	.ndo_get_phys_port_name	= efx_get_phys_port_name,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller = efx_netpoll,
-#endif
 	.ndo_setup_tc		= efx_setup_tc,
 #ifdef CONFIG_RFS_ACCEL
 	.ndo_rx_flow_steer	= efx_filter_rfs,