From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bert Kenward Subject: Re: [PATCH net 10/11] sfc-falcon: remove ndo_poll_controller Date: Fri, 28 Sep 2018 08:30:18 +0100 Message-ID: References: <20180927163201.56609-1-edumazet@google.com> <20180927163201.56609-11-edumazet@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: netdev , Michael Chan , Aviad Krawczyk , Song Liu , Douglas Miller , Yisen Zhuang , "Michael S . Tsirkin" , Jason Wang , Harish Patil , Manish Chopra , Netanel Belgazal , "Solarflare linux maintainers" , Thomas Falcon , Edward Cree To: Eric Dumazet , "David S . Miller" Return-path: Received: from dispatch1-us1.ppe-hosted.com ([67.231.154.164]:51160 "EHLO dispatch1-us1.ppe-hosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726106AbeI1Nwy (ORCPT ); Fri, 28 Sep 2018 09:52:54 -0400 In-Reply-To: <20180927163201.56609-11-edumazet@google.com> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 27/09/18 17:32, 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-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 > Cc: Solarflare linux maintainers > Cc: Edward Cree > Cc: Bert Kenward Acked-By: Bert Kenward > --- > 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, >