On Mon, Sep 8, 2014 at 8:53 PM, Joe Stringer <joestrin...@nicira.com> wrote:
> Was there a particular tool or config flag that you used to detect this
> error / generate this output?
>
I compile kernel with debugging options. CONFIG_PROVE_LOCKING detects
most of deadlocks in kernel, you do not need any other tool.
> On 8 September 2014 14:01, Pravin B Shelar <pshe...@nicira.com> wrote:
>>
>> packet execute is setting egress_tun_info in skb->cb, rather
>> than packet->cb. skb is netlink msg skb. This causes corruption
>> in netlink skb state stored in skb->cb (NETLINK_CB) which
>> results in following deadlock in netlink code.
>>
>> =============================================
>> [ INFO: possible recursive locking detected ]
>> 3.2.62 #2
>> ---------------------------------------------
>> handler55/22851 is trying to acquire lock:
>> (genl_mutex){+.+.+.}, at: [<ffffffff81471ad7>] genl_lock+0x17/0x20
>>
>> but task is already holding lock:
>> (genl_mutex){+.+.+.}, at: [<ffffffff81471ad7>] genl_lock+0x17/0x20
>>
>> other info that might help us debug this:
>> Possible unsafe locking scenario:
>>
>> CPU0
>> ----
>> lock(genl_mutex);
>> lock(genl_mutex);
>>
>> *** DEADLOCK ***
>>
>> May be due to missing lock nesting notation
>>
>> 1 lock held by handler55/22851:
>> #0: (genl_mutex){+.+.+.}, at: [<ffffffff81471ad7>] genl_lock+0x17/0x20
>>
>> stack backtrace:
>> Pid: 22851, comm: handler55 Tainted: G O 3.2.62 #2
>> Call Trace:
>> [<ffffffff81097bb2>] print_deadlock_bug+0xf2/0x100
>> [<ffffffff81099b99>] validate_chain+0x579/0x860
>> [<ffffffff8109a17c>] __lock_acquire+0x2fc/0x4f0
>> [<ffffffff8109aab0>] lock_acquire+0xa0/0x180
>> [<ffffffff81519070>] __mutex_lock_common+0x60/0x420
>> [<ffffffff8151959a>] mutex_lock_nested+0x4a/0x60
>> [<ffffffff81471ad7>] genl_lock+0x17/0x20
>> [<ffffffff81471af6>] genl_rcv+0x16/0x40
>> [<ffffffff8146ff72>] netlink_unicast+0x2f2/0x310
>> [<ffffffff81470159>] netlink_ack+0x109/0x1f0
>> [<ffffffff8147030b>] netlink_rcv_skb+0xcb/0xd0
>> [<ffffffff81471b05>] genl_rcv+0x25/0x40
>> [<ffffffff8146ff72>] netlink_unicast+0x2f2/0x310
>> [<ffffffff8147134c>] netlink_sendmsg+0x28c/0x3d0
>> [<ffffffff8143375f>] sock_sendmsg+0xef/0x120
>> [<ffffffff81435766>] ___sys_sendmsg+0x416/0x430
>> [<ffffffff81435949>] __sys_sendmsg+0x49/0x90
>> [<ffffffff814359a9>] sys_sendmsg+0x19/0x20
>> [<ffffffff8152432b>] system_call_fastpath+0x16/0x1b
>>
>> Reported-by: Joe Stringer <joestrin...@nicira.com>
>> Signed-off-by: Pravin B Shelar <pshe...@nicira.com>
>> ---
>> datapath/datapath.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/datapath/datapath.c b/datapath/datapath.c
>> index fae0ac7..d851cab 100644
>> --- a/datapath/datapath.c
>> +++ b/datapath/datapath.c
>> @@ -569,7 +569,7 @@ static int ovs_packet_cmd_execute(struct sk_buff *skb,
>> struct genl_info *info)
>>
>> rcu_assign_pointer(flow->sf_acts, acts);
>> OVS_CB(packet)->pkt_key = &flow->key;
>> - OVS_CB(skb)->egress_tun_info = NULL;
>> + OVS_CB(packet)->egress_tun_info = NULL;
>> packet->priority = flow->key.phy.priority;
>> packet->mark = flow->key.phy.skb_mark;
>>
>> --
>> 1.9.3
>>
>
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