Commits
Eric Dumazet committed 9650388b5c5
ipv4: arp: fix a lockdep splat in arp_solicit()
Yan Burman reported following lockdep warning :
=============================================
[ INFO: possible recursive locking detected ]
3.7.0+ #24 Not tainted
---------------------------------------------
swapper/1/0 is trying to acquire lock:
(&n->lock){++--..}, at: [<ffffffff8139f56e>] __neigh_event_send
+0x2e/0x2f0
but task is already holding lock:
(&n->lock){++--..}, at: [<ffffffff813f63f4>] arp_solicit+0x1d4/0x280
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&n->lock);
lock(&n->lock);
*** DEADLOCK ***
May be due to missing lock nesting notation
4 locks held by swapper/1/0:
#0: (((&n->timer))){+.-...}, at: [<ffffffff8104b350>]
call_timer_fn+0x0/0x1c0
#1: (&n->lock){++--..}, at: [<ffffffff813f63f4>] arp_solicit
+0x1d4/0x280
#2: (rcu_read_lock_bh){.+....}, at: [<ffffffff81395400>]
dev_queue_xmit+0x0/0x5d0
#3: (rcu_read_lock_bh){.+....}, at: [<ffffffff813cb41e>]
ip_finish_output+0x13e/0x640
stack backtrace:
Pid: 0, comm: swapper/1 Not tainted 3.7.0+ #24
Call Trace:
<IRQ> [<ffffffff8108c7ac>] validate_chain+0xdcc/0x11f0
[<ffffffff8108d570>] ? __lock_acquire+0x440/0xc30
[<ffffffff81120565>] ? kmem_cache_free+0xe5/0x1c0
[<ffffffff8108d570>] __lock_acquire+0x440/0xc30
[<ffffffff813c3570>] ? inet_getpeer+0x40/0x600
[<ffffffff8108d570>] ? __lock_acquire+0x440/0xc30
[<ffffffff8139f56e>] ? __neigh_event_send+0x2e/0x2f0
[<ffffffff8108ddf5>] lock_acquire+0x95/0x140
[<ffffffff8139f56e>] ? __neigh_event_send+0x2e/0x2f0
[<ffffffff8108d570>] ? __lock_acquire+0x440/0xc30
[<ffffffff81448d4b>] _raw_write_lock_bh+0x3b/0x50
[<ffffffff8139f56e>] ? __neigh_event_send+0x2e/0x2f0
[<ffffffff8139f56e>] __neigh_event_send+0x2e/0x2f0
[<ffffffff8139f99b>] neigh_resolve_output+0x16b/0x270
[<ffffffff813cb62d>] ip_finish_output+0x34d/0x640
[<ffffffff813cb41e>] ? ip_finish_output+0x13e/0x640
[<ffffffffa046f146>] ? vxlan_xmit+0x556/0xbec [vxlan]
[<ffffffff813cb9a0>] ip_output+0x80/0xf0
[<ffffffff813ca368>] ip_local_out+0x28/0x80
[<ffffffffa046f25a>] vxlan_xmit+0x66a/0xbec [vxlan]
[<ffffffffa046f146>] ? vxlan_xmit+0x556/0xbec [vxlan]
[<ffffffff81394a50>] ? skb_gso_segment+0x2b0/0x2b0
[<ffffffff81449355>] ? _raw_spin_unlock_irqrestore+0x65/0x80
[<ffffffff81394c57>] ? dev_queue_xmit_nit+0x207/0x270
[<ffffffff813950c8>] dev_hard_start_xmit+0x298/0x5d0
[<ffffffff813956f3>] dev_queue_xmit+0x2f3/0x5d0
[<ffffffff81395400>] ? dev_hard_start_xmit+0x5d0/0x5d0
[<ffffffff813f5788>] arp_xmit+0x58/0x60
[<ffffffff813f59db>] arp_send+0x3b/0x40
[<ffffffff813f6424>] arp_solicit+0x204/0x280
[<ffffffff813a1a70>] ? neigh_add+0x310/0x310
[<ffffffff8139f515>] neigh_probe+0x45/0x70
[<ffffffff813a1c10>] neigh_timer_handler+0x1a0/0x2a0
[<ffffffff8104b3cf>] call_timer_fn+0x7f/0x1c0
[<ffffffff8104b350>] ? detach_if_pending+0x120/0x120
[<ffffffff8104b748>] run_timer_softirq+0x238/0x2b0
[<ffffffff813a1a70>] ? neigh_add+0x310/0x310
[<ffffffff81043e51>] __do_softirq+0x101/0x280
[<ffffffff814518cc>] call_softirq+0x1c/0x30
[<ffffffff81003b65>] do_softirq+0x85/0xc0
[<ffffffff81043a7e>] irq_exit+0x9e/0xc0
[<ffffffff810264f8>] smp_apic_timer_interrupt+0x68/0xa0
[<ffffffff8145122f>] apic_timer_interrupt+0x6f/0x80
<EOI> [<ffffffff8100a054>] ? mwait_idle+0xa4/0x1c0
[<ffffffff8100a04b>] ? mwait_idle+0x9b/0x1c0
[<ffffffff8100a6a9>] cpu_idle+0x89/0xe0
[<ffffffff81441127>] start_secondary+0x1b2/0x1b6
Bug is from arp_solicit(), releasing the neigh lock after arp_send()
In case of vxlan, we eventually need to write lock a neigh lock later.
Its a false positive, but we can get rid of it without lockdep
annotations.
We can instead use neigh_ha_snapshot() helper.
Reported-by: Yan Burman <yanb@mellanox.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>