From a2842a1e66329798d66563b52faec1a299ec4f73 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 25 Jun 2012 05:35:45 +0000 Subject: [PATCH] net: l2tp_eth: use LLTX to avoid LOCKDEP splats Denys Fedoryshchenko reported a LOCKDEP issue with l2tp code. [ 8683.927442] ====================================================== [ 8683.927555] [ INFO: possible circular locking dependency detected ] [ 8683.927672] 3.4.1-build-0061 #14 Not tainted [ 8683.927782] ------------------------------------------------------- [ 8683.927895] swapper/0/0 is trying to acquire lock: [ 8683.928007] (slock-AF_INET){+.-...}, at: [] l2tp_xmit_skb+0x173/0x47e [l2tp_core] [ 8683.928121] [ 8683.928121] but task is already holding lock: [ 8683.928121] (_xmit_ETHER#2){+.-...}, at: [] sch_direct_xmit+0x36/0x119 [ 8683.928121] [ 8683.928121] which lock already depends on the new lock. [ 8683.928121] [ 8683.928121] [ 8683.928121] the existing dependency chain (in reverse order) is: [ 8683.928121] [ 8683.928121] -> #1 (_xmit_ETHER#2){+.-...}: [ 8683.928121] [] lock_acquire+0x71/0x85 [ 8683.928121] [] _raw_spin_lock+0x33/0x40 [ 8683.928121] [] ip_send_reply+0xf2/0x1ce [ 8683.928121] [] tcp_v4_send_reset+0x153/0x16f [ 8683.928121] [] tcp_v4_do_rcv+0x172/0x194 [ 8683.928121] [] tcp_v4_rcv+0x387/0x5a0 [ 8683.928121] [] ip_local_deliver_finish+0x13a/0x1e9 [ 8683.928121] [] NF_HOOK.clone.11+0x46/0x4d [ 8683.928121] [] ip_local_deliver+0x41/0x45 [ 8683.928121] [] ip_rcv_finish+0x31a/0x33c [ 8683.928121] [] NF_HOOK.clone.11+0x46/0x4d [ 8683.928121] [] ip_rcv+0x201/0x23d [ 8683.928121] [] __netif_receive_skb+0x329/0x378 [ 8683.928121] [] netif_receive_skb+0x4e/0x7d [ 8683.928121] [] rtl8139_poll+0x243/0x33d [8139too] [ 8683.928121] [] net_rx_action+0x90/0x15d [ 8683.928121] [] __do_softirq+0x7b/0x118 [ 8683.928121] [ 8683.928121] -> #0 (slock-AF_INET){+.-...}: [ 8683.928121] [] __lock_acquire+0x9a3/0xc27 [ 8683.928121] [] lock_acquire+0x71/0x85 [ 8683.928121] [] _raw_spin_lock+0x33/0x40 [ 8683.928121] [] l2tp_xmit_skb+0x173/0x47e [l2tp_core] [ 8683.928121] [] l2tp_eth_dev_xmit+0x1a/0x2f [l2tp_eth] [ 8683.928121] [] dev_hard_start_xmit+0x333/0x3f2 [ 8683.928121] [] sch_direct_xmit+0x55/0x119 [ 8683.928121] [] dev_queue_xmit+0x282/0x418 [ 8683.928121] [] NF_HOOK.clone.19+0x45/0x4c [ 8683.928121] [] arp_xmit+0x22/0x24 [ 8683.928121] [] arp_send+0x41/0x48 [ 8683.928121] [] arp_process+0x289/0x491 [ 8683.928121] [] NF_HOOK.clone.19+0x45/0x4c [ 8683.928121] [] arp_rcv+0xb1/0xc3 [ 8683.928121] [] __netif_receive_skb+0x329/0x378 [ 8683.928121] [] process_backlog+0x69/0x130 [ 8683.928121] [] net_rx_action+0x90/0x15d [ 8683.928121] [] __do_softirq+0x7b/0x118 [ 8683.928121] [ 8683.928121] other info that might help us debug this: [ 8683.928121] [ 8683.928121] Possible unsafe locking scenario: [ 8683.928121] [ 8683.928121] CPU0 CPU1 [ 8683.928121] ---- ---- [ 8683.928121] lock(_xmit_ETHER#2); [ 8683.928121] lock(slock-AF_INET); [ 8683.928121] lock(_xmit_ETHER#2); [ 8683.928121] lock(slock-AF_INET); [ 8683.928121] [ 8683.928121] *** DEADLOCK *** [ 8683.928121] [ 8683.928121] 3 locks held by swapper/0/0: [ 8683.928121] #0: (rcu_read_lock){.+.+..}, at: [] rcu_lock_acquire+0x0/0x30 [ 8683.928121] #1: (rcu_read_lock_bh){.+....}, at: [] rcu_lock_acquire+0x0/0x30 [ 8683.928121] #2: (_xmit_ETHER#2){+.-...}, at: [] sch_direct_xmit+0x36/0x119 [ 8683.928121] [ 8683.928121] stack backtrace: [ 8683.928121] Pid: 0, comm: swapper/0 Not tainted 3.4.1-build-0061 #14 [ 8683.928121] Call Trace: [ 8683.928121] [] ? printk+0x18/0x1a [ 8683.928121] [] print_circular_bug+0x1ac/0x1b6 [ 8683.928121] [] __lock_acquire+0x9a3/0xc27 [ 8683.928121] [] lock_acquire+0x71/0x85 [ 8683.928121] [] ? l2tp_xmit_skb+0x173/0x47e [l2tp_core] [ 8683.928121] [] _raw_spin_lock+0x33/0x40 [ 8683.928121] [] ? l2tp_xmit_skb+0x173/0x47e [l2tp_core] [ 8683.928121] [] l2tp_xmit_skb+0x173/0x47e [l2tp_core] [ 8683.928121] [] l2tp_eth_dev_xmit+0x1a/0x2f [l2tp_eth] [ 8683.928121] [] dev_hard_start_xmit+0x333/0x3f2 [ 8683.928121] [] sch_direct_xmit+0x55/0x119 [ 8683.928121] [] dev_queue_xmit+0x282/0x418 [ 8683.928121] [] ? dev_hard_start_xmit+0x3f2/0x3f2 [ 8683.928121] [] NF_HOOK.clone.19+0x45/0x4c [ 8683.928121] [] arp_xmit+0x22/0x24 [ 8683.928121] [] ? dev_hard_start_xmit+0x3f2/0x3f2 [ 8683.928121] [] arp_send+0x41/0x48 [ 8683.928121] [] arp_process+0x289/0x491 [ 8683.928121] [] ? __neigh_lookup.clone.20+0x42/0x42 [ 8683.928121] [] NF_HOOK.clone.19+0x45/0x4c [ 8683.928121] [] arp_rcv+0xb1/0xc3 [ 8683.928121] [] ? __neigh_lookup.clone.20+0x42/0x42 [ 8683.928121] [] __netif_receive_skb+0x329/0x378 [ 8683.928121] [] process_backlog+0x69/0x130 [ 8683.928121] [] net_rx_action+0x90/0x15d [ 8683.928121] [] __do_softirq+0x7b/0x118 [ 8683.928121] [] ? local_bh_enable+0xd/0xd [ 8683.928121] [] ? irq_exit+0x41/0x91 [ 8683.928121] [] ? do_IRQ+0x79/0x8d [ 8683.928121] [] ? trace_hardirqs_off_caller+0x2e/0x86 [ 8683.928121] [] ? common_interrupt+0x2e/0x34 [ 8683.928121] [] ? default_idle+0x23/0x38 [ 8683.928121] [] ? cpu_idle+0x55/0x6f [ 8683.928121] [] ? rest_init+0xa1/0xa7 [ 8683.928121] [] ? __read_lock_failed+0x14/0x14 [ 8683.928121] [] ? start_kernel+0x303/0x30a [ 8683.928121] [] ? repair_env_string+0x51/0x51 [ 8683.928121] [] ? i386_start_kernel+0xa8/0xaf It appears that like most virtual devices, l2tp should be converted to LLTX mode. This patch takes care of statistics using atomic_long in both RX and TX paths, and fix a bug in l2tp_eth_dev_recv(), which was caching skb->data before a pskb_may_pull() call. Signed-off-by: Eric Dumazet Reported-by: Denys Fedoryshchenko Cc: James Chapman Cc: Hong zhi guo Cc: Francois Romieu Signed-off-by: David S. Miller --- net/l2tp/l2tp_eth.c | 43 ++++++++++++++++++++++++++++++++----------- 1 file changed, 32 insertions(+), 11 deletions(-) diff --git a/net/l2tp/l2tp_eth.c b/net/l2tp/l2tp_eth.c index c3738f49646a..47b259fccd27 100644 --- a/net/l2tp/l2tp_eth.c +++ b/net/l2tp/l2tp_eth.c @@ -42,6 +42,11 @@ struct l2tp_eth { struct sock *tunnel_sock; struct l2tp_session *session; struct list_head list; + atomic_long_t tx_bytes; + atomic_long_t tx_packets; + atomic_long_t rx_bytes; + atomic_long_t rx_packets; + atomic_long_t rx_errors; }; /* via l2tp_session_priv() */ @@ -88,24 +93,40 @@ static int l2tp_eth_dev_xmit(struct sk_buff *skb, struct net_device *dev) struct l2tp_eth *priv = netdev_priv(dev); struct l2tp_session *session = priv->session; - dev->stats.tx_bytes += skb->len; - dev->stats.tx_packets++; + atomic_long_add(skb->len, &priv->tx_bytes); + atomic_long_inc(&priv->tx_packets); l2tp_xmit_skb(session, skb, session->hdr_len); return NETDEV_TX_OK; } +static struct rtnl_link_stats64 *l2tp_eth_get_stats64(struct net_device *dev, + struct rtnl_link_stats64 *stats) +{ + struct l2tp_eth *priv = netdev_priv(dev); + + stats->tx_bytes = atomic_long_read(&priv->tx_bytes); + stats->tx_packets = atomic_long_read(&priv->tx_packets); + stats->rx_bytes = atomic_long_read(&priv->rx_bytes); + stats->rx_packets = atomic_long_read(&priv->rx_packets); + stats->rx_errors = atomic_long_read(&priv->rx_errors); + return stats; +} + + static struct net_device_ops l2tp_eth_netdev_ops = { .ndo_init = l2tp_eth_dev_init, .ndo_uninit = l2tp_eth_dev_uninit, .ndo_start_xmit = l2tp_eth_dev_xmit, + .ndo_get_stats64 = l2tp_eth_get_stats64, }; static void l2tp_eth_dev_setup(struct net_device *dev) { ether_setup(dev); - dev->priv_flags &= ~IFF_TX_SKB_SHARING; + dev->priv_flags &= ~IFF_TX_SKB_SHARING; + dev->features |= NETIF_F_LLTX; dev->netdev_ops = &l2tp_eth_netdev_ops; dev->destructor = free_netdev; } @@ -114,17 +135,17 @@ static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb, { struct l2tp_eth_sess *spriv = l2tp_session_priv(session); struct net_device *dev = spriv->dev; + struct l2tp_eth *priv = netdev_priv(dev); if (session->debug & L2TP_MSG_DATA) { unsigned int length; - u8 *ptr = skb->data; length = min(32u, skb->len); if (!pskb_may_pull(skb, length)) goto error; pr_debug("%s: eth recv\n", session->name); - print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, ptr, length); + print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length); } if (!pskb_may_pull(skb, sizeof(ETH_HLEN))) @@ -139,15 +160,15 @@ static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb, nf_reset(skb); if (dev_forward_skb(dev, skb) == NET_RX_SUCCESS) { - dev->stats.rx_packets++; - dev->stats.rx_bytes += data_len; - } else - dev->stats.rx_errors++; - + atomic_long_inc(&priv->rx_packets); + atomic_long_add(data_len, &priv->rx_bytes); + } else { + atomic_long_inc(&priv->rx_errors); + } return; error: - dev->stats.rx_errors++; + atomic_long_inc(&priv->rx_errors); kfree_skb(skb); } -- 2.20.1