• Eric Dumazet's avatar
    net: l2tp_eth: use LLTX to avoid LOCKDEP splats · a2842a1e
    Eric Dumazet authored
    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: [<e0fc73ec>]
    l2tp_xmit_skb+0x173/0x47e [l2tp_core]
    [ 8683.928121]
    [ 8683.928121] but task is already holding lock:
    [ 8683.928121]  (_xmit_ETHER#2){+.-...}, at: [<c02f062d>]
    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]        [<c015a561>] lock_acquire+0x71/0x85
    [ 8683.928121]        [<c034da2d>] _raw_spin_lock+0x33/0x40
    [ 8683.928121]        [<c0304e0c>] ip_send_reply+0xf2/0x1ce
    [ 8683.928121]        [<c0317dbc>] tcp_v4_send_reset+0x153/0x16f
    [ 8683.928121]        [<c0317f4a>] tcp_v4_do_rcv+0x172/0x194
    [ 8683.928121]        [<c031929b>] tcp_v4_rcv+0x387/0x5a0
    [ 8683.928121]        [<c03001d0>] ip_local_deliver_finish+0x13a/0x1e9
    [ 8683.928121]        [<c0300645>] NF_HOOK.clone.11+0x46/0x4d
    [ 8683.928121]        [<c030075b>] ip_local_deliver+0x41/0x45
    [ 8683.928121]        [<c03005dd>] ip_rcv_finish+0x31a/0x33c
    [ 8683.928121]        [<c0300645>] NF_HOOK.clone.11+0x46/0x4d
    [ 8683.928121]        [<c0300960>] ip_rcv+0x201/0x23d
    [ 8683.928121]        [<c02de91b>] __netif_receive_skb+0x329/0x378
    [ 8683.928121]        [<c02deae8>] netif_receive_skb+0x4e/0x7d
    [ 8683.928121]        [<e08d5ef3>] rtl8139_poll+0x243/0x33d [8139too]
    [ 8683.928121]        [<c02df103>] net_rx_action+0x90/0x15d
    [ 8683.928121]        [<c012b2b5>] __do_softirq+0x7b/0x118
    [ 8683.928121]
    [ 8683.928121] -> #0 (slock-AF_INET){+.-...}:
    [ 8683.928121]        [<c0159f1b>] __lock_acquire+0x9a3/0xc27
    [ 8683.928121]        [<c015a561>] lock_acquire+0x71/0x85
    [ 8683.928121]        [<c034da2d>] _raw_spin_lock+0x33/0x40
    [ 8683.928121]        [<e0fc73ec>] l2tp_xmit_skb+0x173/0x47e
    [l2tp_core]
    [ 8683.928121]        [<e0fe31fb>] l2tp_eth_dev_xmit+0x1a/0x2f
    [l2tp_eth]
    [ 8683.928121]        [<c02e01e7>] dev_hard_start_xmit+0x333/0x3f2
    [ 8683.928121]        [<c02f064c>] sch_direct_xmit+0x55/0x119
    [ 8683.928121]        [<c02e0528>] dev_queue_xmit+0x282/0x418
    [ 8683.928121]        [<c031f4fb>] NF_HOOK.clone.19+0x45/0x4c
    [ 8683.928121]        [<c031f524>] arp_xmit+0x22/0x24
    [ 8683.928121]        [<c031f567>] arp_send+0x41/0x48
    [ 8683.928121]        [<c031fa7d>] arp_process+0x289/0x491
    [ 8683.928121]        [<c031f4fb>] NF_HOOK.clone.19+0x45/0x4c
    [ 8683.928121]        [<c031f7a0>] arp_rcv+0xb1/0xc3
    [ 8683.928121]        [<c02de91b>] __netif_receive_skb+0x329/0x378
    [ 8683.928121]        [<c02de9d3>] process_backlog+0x69/0x130
    [ 8683.928121]        [<c02df103>] net_rx_action+0x90/0x15d
    [ 8683.928121]        [<c012b2b5>] __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: [<c02dbc10>]
    rcu_lock_acquire+0x0/0x30
    [ 8683.928121]  #1:  (rcu_read_lock_bh){.+....}, at: [<c02dbc10>]
    rcu_lock_acquire+0x0/0x30
    [ 8683.928121]  #2:  (_xmit_ETHER#2){+.-...}, at: [<c02f062d>]
    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]  [<c034bdd2>] ? printk+0x18/0x1a
    [ 8683.928121]  [<c0158904>] print_circular_bug+0x1ac/0x1b6
    [ 8683.928121]  [<c0159f1b>] __lock_acquire+0x9a3/0xc27
    [ 8683.928121]  [<c015a561>] lock_acquire+0x71/0x85
    [ 8683.928121]  [<e0fc73ec>] ? l2tp_xmit_skb+0x173/0x47e [l2tp_core]
    [ 8683.928121]  [<c034da2d>] _raw_spin_lock+0x33/0x40
    [ 8683.928121]  [<e0fc73ec>] ? l2tp_xmit_skb+0x173/0x47e [l2tp_core]
    [ 8683.928121]  [<e0fc73ec>] l2tp_xmit_skb+0x173/0x47e [l2tp_core]
    [ 8683.928121]  [<e0fe31fb>] l2tp_eth_dev_xmit+0x1a/0x2f [l2tp_eth]
    [ 8683.928121]  [<c02e01e7>] dev_hard_start_xmit+0x333/0x3f2
    [ 8683.928121]  [<c02f064c>] sch_direct_xmit+0x55/0x119
    [ 8683.928121]  [<c02e0528>] dev_queue_xmit+0x282/0x418
    [ 8683.928121]  [<c02e02a6>] ? dev_hard_start_xmit+0x3f2/0x3f2
    [ 8683.928121]  [<c031f4fb>] NF_HOOK.clone.19+0x45/0x4c
    [ 8683.928121]  [<c031f524>] arp_xmit+0x22/0x24
    [ 8683.928121]  [<c02e02a6>] ? dev_hard_start_xmit+0x3f2/0x3f2
    [ 8683.928121]  [<c031f567>] arp_send+0x41/0x48
    [ 8683.928121]  [<c031fa7d>] arp_process+0x289/0x491
    [ 8683.928121]  [<c031f7f4>] ? __neigh_lookup.clone.20+0x42/0x42
    [ 8683.928121]  [<c031f4fb>] NF_HOOK.clone.19+0x45/0x4c
    [ 8683.928121]  [<c031f7a0>] arp_rcv+0xb1/0xc3
    [ 8683.928121]  [<c031f7f4>] ? __neigh_lookup.clone.20+0x42/0x42
    [ 8683.928121]  [<c02de91b>] __netif_receive_skb+0x329/0x378
    [ 8683.928121]  [<c02de9d3>] process_backlog+0x69/0x130
    [ 8683.928121]  [<c02df103>] net_rx_action+0x90/0x15d
    [ 8683.928121]  [<c012b2b5>] __do_softirq+0x7b/0x118
    [ 8683.928121]  [<c012b23a>] ? local_bh_enable+0xd/0xd
    [ 8683.928121]  <IRQ>  [<c012b4d0>] ? irq_exit+0x41/0x91
    [ 8683.928121]  [<c0103c6f>] ? do_IRQ+0x79/0x8d
    [ 8683.928121]  [<c0157ea1>] ? trace_hardirqs_off_caller+0x2e/0x86
    [ 8683.928121]  [<c034ef6e>] ? common_interrupt+0x2e/0x34
    [ 8683.928121]  [<c0108a33>] ? default_idle+0x23/0x38
    [ 8683.928121]  [<c01091a8>] ? cpu_idle+0x55/0x6f
    [ 8683.928121]  [<c033df25>] ? rest_init+0xa1/0xa7
    [ 8683.928121]  [<c033de84>] ? __read_lock_failed+0x14/0x14
    [ 8683.928121]  [<c0498745>] ? start_kernel+0x303/0x30a
    [ 8683.928121]  [<c0498209>] ? repair_env_string+0x51/0x51
    [ 8683.928121]  [<c04980a8>] ? 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: 's avatarEric Dumazet <edumazet@google.com>
    Reported-by: Denys Fedoryshchenko's avatarDenys Fedoryshchenko <denys@visp.net.lb>
    Cc: James Chapman <jchapman@katalix.com>
    Cc: Hong zhi guo <honkiko@gmail.com>
    Cc: Francois Romieu <romieu@fr.zoreil.com>
    Signed-off-by: 's avatarDavid S. Miller <davem@davemloft.net>
    a2842a1e
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