Re: [PATCH net 09/11] sfc: remove ndo_poll_controller
On 27/09/18 17:31, Eric Dumazet wrote:
> 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
> Cc: Edward Cree
> Cc: Bert Kenward
> Cc: Solarflare linux maintainers
Acked-By: Bert Kenward
> ---
> drivers/net/ethernet/sfc/efx.c | 26 --
> 1 file changed, 26 deletions(-)
>
> diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
> index
> 330233286e785254f5f29c87f9557a305974f606..3d0dd39c289e05b8a7a6778363461ef5698dc62b
> 100644
> --- a/drivers/net/ethernet/sfc/efx.c
> +++ b/drivers/net/ethernet/sfc/efx.c
> @@ -2206,29 +2206,6 @@ static void efx_fini_napi(struct efx_nic *efx)
> efx_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 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
> @@ -2509,9 +2486,6 @@ static const struct net_device_ops efx_netdev_ops = {
> #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,
>
[PATCH net 09/11] sfc: 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 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
Cc: Edward Cree
Cc: Bert Kenward
Cc: Solarflare linux maintainers
---
drivers/net/ethernet/sfc/efx.c | 26 --
1 file changed, 26 deletions(-)
diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index
330233286e785254f5f29c87f9557a305974f606..3d0dd39c289e05b8a7a6778363461ef5698dc62b
100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -2206,29 +2206,6 @@ static void efx_fini_napi(struct efx_nic *efx)
efx_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 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
@@ -2509,9 +2486,6 @@ static const struct net_device_ops efx_netdev_ops = {
#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,
--
2.19.0.605.g01d371f741-goog
