netdev - [PATCH net 10/11] sfc-falcon: remove ndo_poll

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Date:   Thu, 27 Sep 2018 09:32:00 -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>,
        Edward Cree <ecree@...arflare.com>,
        Bert Kenward <bkenward@...arflare.com>
Subject: [PATCH net 10/11] sfc-falcon: 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.

sfc-falcon 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: Solarflare linux maintainers <linux-net-drivers@...arflare.com>
Cc: Edward Cree <ecree@...arflare.com>
Cc: Bert Kenward <bkenward@...arflare.com>
---
 drivers/net/ethernet/sfc/falcon/efx.c | 26 --------------------------
 1 file changed, 26 deletions(-)

diff --git a/drivers/net/ethernet/sfc/falcon/efx.c b/drivers/net/ethernet/sfc/falcon/efx.c
index dd5530a4f8c8936868aed7171bd9481f93730d76..03e2455c502eacd9a4fd5c7fd320a9edcf265f77 100644
--- a/drivers/net/ethernet/sfc/falcon/efx.c
+++ b/drivers/net/ethernet/sfc/falcon/efx.c
@@ -2052,29 +2052,6 @@ static void ef4_fini_napi(struct ef4_nic *efx)
 		ef4_fini_napi_channel(channel);
 }
 
-/**************************************************************************
- *
- * 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 ef4_netpoll(struct net_device *net_dev)
-{
-	struct ef4_nic *efx = netdev_priv(net_dev);
-	struct ef4_channel *channel;
-
-	ef4_for_each_channel(channel, efx)
-		ef4_schedule_channel(channel);
-}
-
-#endif
-
 /**************************************************************************
  *
  * Kernel net device interface
@@ -2250,9 +2227,6 @@ static const struct net_device_ops ef4_netdev_ops = {
 	.ndo_set_mac_address	= ef4_set_mac_address,
 	.ndo_set_rx_mode	= ef4_set_rx_mode,
 	.ndo_set_features	= ef4_set_features,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller = ef4_netpoll,
-#endif
 	.ndo_setup_tc		= ef4_setup_tc,
 #ifdef CONFIG_RFS_ACCEL
 	.ndo_rx_flow_steer	= ef4_filter_rfs,
-- 
2.19.0.605.g01d371f741-goog