From 765cdc209cb89fb81215310a066cd0a3018ffef7 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 21 Sep 2018 15:27:52 -0700 Subject: [PATCH] tun: 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. tun 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 Signed-off-by: David S. Miller --- drivers/net/tun.c | 43 ------------------------------------------- 1 file changed, 43 deletions(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index ebd07ad82431..e2648b5a3861 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1153,43 +1153,6 @@ static netdev_features_t tun_net_fix_features(struct net_device *dev, return (features & tun->set_features) | (features & ~TUN_USER_FEATURES); } -#ifdef CONFIG_NET_POLL_CONTROLLER -static void tun_poll_controller(struct net_device *dev) -{ - /* - * Tun only receives frames when: - * 1) the char device endpoint gets data from user space - * 2) the tun socket gets a sendmsg call from user space - * If NAPI is not enabled, since both of those are synchronous - * operations, we are guaranteed never to have pending data when we poll - * for it so there is nothing to do here but return. - * We need this though so netpoll recognizes us as an interface that - * supports polling, which enables bridge devices in virt setups to - * still use netconsole - * If NAPI is enabled, however, we need to schedule polling for all - * queues unless we are using napi_gro_frags(), which we call in - * process context and not in NAPI context. - */ - struct tun_struct *tun = netdev_priv(dev); - - if (tun->flags & IFF_NAPI) { - struct tun_file *tfile; - int i; - - if (tun_napi_frags_enabled(tun)) - return; - - rcu_read_lock(); - for (i = 0; i < tun->numqueues; i++) { - tfile = rcu_dereference(tun->tfiles[i]); - if (tfile->napi_enabled) - napi_schedule(&tfile->napi); - } - rcu_read_unlock(); - } - return; -} -#endif static void tun_set_headroom(struct net_device *dev, int new_hr) { @@ -1283,9 +1246,6 @@ static const struct net_device_ops tun_netdev_ops = { .ndo_start_xmit = tun_net_xmit, .ndo_fix_features = tun_net_fix_features, .ndo_select_queue = tun_select_queue, -#ifdef CONFIG_NET_POLL_CONTROLLER - .ndo_poll_controller = tun_poll_controller, -#endif .ndo_set_rx_headroom = tun_set_headroom, .ndo_get_stats64 = tun_net_get_stats64, }; @@ -1365,9 +1325,6 @@ static const struct net_device_ops tap_netdev_ops = { .ndo_set_mac_address = eth_mac_addr, .ndo_validate_addr = eth_validate_addr, .ndo_select_queue = tun_select_queue, -#ifdef CONFIG_NET_POLL_CONTROLLER - .ndo_poll_controller = tun_poll_controller, -#endif .ndo_features_check = passthru_features_check, .ndo_set_rx_headroom = tun_set_headroom, .ndo_get_stats64 = tun_net_get_stats64,