On 10/17/2014 08:37 AM, Jukka Rissanen wrote:
> Hi,
>
> I have seen the deadlock warnings from lockdep when pushing lot of data
> through a 6lowpan link. I was converting the read/write locks in 6lowpan
> to use RCU and it helped the situation slightly as I see the lockdep
> warning less now. I will send these patches soon to ml.
>
> I noticed that if I add huge amount of credits for the connection, then
> the issue is not seen. So when the credits are exhausted in receiving
> end, the l2cap sends message to other end, see the backtrace below
> (l2cap_recv_frame() followed by l2cap_do_send()).
>
> At the same time a lot of data is pushed through the 6lowpan link. These
> operations then conflict as seen in the log below.
>
> One way to reproduce the issue is like this:
>
> host1# nc -6 -l 9999 > /dev/null
>
> host2# nc -6 fe80::21e:abff:fe4c:5257%bt0 9999 < /dev/urandom
>
>
> Any ideas how to solve this?
The spin_lock() in hci_queue_acl() still needs to be spin_lock_bh().
Regards,
Peter Hurley
> Is there a bug in l2cap/hci layers or am I doing something wrong with
> 6lowpan connection?
>
>
> =================================
> [ INFO: inconsistent lock state ]
> 3.17.0-rc1-bt6lowpan #1 Not tainted
> ---------------------------------
> inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
> kworker/u3:1/384 [HC0[0]:SC0[0]:HE1:SE1] takes:
> (&(&list->lock)->rlock#6){+.?...}, at: [<f831dd4c>] hci_send_acl
> +0xac/0x290 [bluetooth]
> {IN-SOFTIRQ-W} state was registered at:
> [<c10915a3>] __lock_acquire+0x6d3/0x1d20
> [<c109325d>] lock_acquire+0x9d/0x140
> [<c1889c25>] _raw_spin_lock+0x45/0x80
> [<f831dd4c>] hci_send_acl+0xac/0x290 [bluetooth]
> [<f833efe0>] l2cap_do_send+0x60/0x100 [bluetooth]
> [<f8342bb0>] l2cap_chan_send+0x7f0/0x10e0 [bluetooth]
> [<f88dc8ee>] send_pkt+0x4e/0xa0 [bluetooth_6lowpan]
> [<f88dcd6e>] bt_xmit+0x42e/0x890 [bluetooth_6lowpan]
> [<c17742f4>] dev_hard_start_xmit+0x344/0x670
> [<c17749ad>] __dev_queue_xmit+0x38d/0x680
> [<c1774caf>] dev_queue_xmit+0xf/0x20
> [<c177b8b0>] neigh_connected_output+0x130/0x1a0
> [<c1812a63>] ip6_finish_output2+0x173/0x8c0
> [<c18182db>] ip6_finish_output+0x7b/0x1b0
> [<c18184a7>] ip6_output+0x97/0x2a0
> [<c183a46b>] mld_sendpack+0x5eb/0x650
> [<c183acc1>] mld_ifc_timer_expire+0x191/0x2f0
> [<c10ac385>] call_timer_fn+0x85/0x1c0
> [<c10acb72>] run_timer_softirq+0x192/0x280
> [<c104fd84>] __do_softirq+0xd4/0x300
> [<c10049fc>] do_softirq_own_stack+0x2c/0x40
> [<c1050136>] irq_exit+0x86/0xb0
> [<c188bd98>] smp_apic_timer_interrupt+0x38/0x50
> [<c188b6ce>] apic_timer_interrupt+0x32/0x38
> irq event stamp: 17003
> hardirqs last enabled at (17003): [<c188a065>]
> _raw_spin_unlock_irqrestore+0x55/0x70
> hardirqs last disabled at (17002): [<c1889e03>] _raw_spin_lock_irqsave
> +0x23/0x90
> softirqs last enabled at (6648): [<c104ff5c>] __do_softirq+0x2ac/0x300
> softirqs last disabled at (6619): [<c10049fc>] do_softirq_own_stack
> +0x2c/0x40
>
> other info that might help us debug this:
> Possible unsafe locking scenario:
>
> CPU0
> ----
> lock(&(&list->lock)->rlock#6);
> <Interrupt>
> lock(&(&list->lock)->rlock#6);
>
> *** DEADLOCK ***
>
> 3 locks held by kworker/u3:1/384:
> #0: ("%s"hdev->name#2){.+.+.+}, at: [<c10622c3>] process_one_work
> +0x113/0x4a0
> #1: ((&hdev->rx_work)){+.+.+.}, at: [<c10622c3>] process_one_work
> +0x113/0x4a0
> #2: (&chan->lock){+.+.+.}, at: [<f833e569>] l2cap_get_chan_by_dcid
> +0x89/0x90 [bluetooth]
>
> stack backtrace:
> CPU: 0 PID: 384 Comm: kworker/u3:1 Not tainted 3.17.0-rc1-bt6lowpan #1
> Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox
> 12/01/2006
> Workqueue: hci0 hci_rx_work [bluetooth]
> f4700000 00000000 f466bb90 c18821c1 c2344320 f466bbb0 c1880a94
> c1ad9264
> c1ad9201 c1ad95f8 f4700614 00000006 c108e0c0 f466bbe0 c108ea8c
> 00000006
> f4700000 f466bffc 323ca8b2 0000002a 00000004 f4700000 f4700618
> 00000003
> Call Trace:
> [<c18821c1>] dump_stack+0x4b/0x75
> [<c1880a94>] print_usage_bug.part.36+0x209/0x213
> [<c108e0c0>] ? check_usage_forwards+0x110/0x110
> [<c108ea8c>] mark_lock+0x11c/0x6e0
> [<c10915e4>] __lock_acquire+0x714/0x1d20
> [<c1004b6f>] ? dump_trace+0xcf/0x1f0
> [<c100a5f8>] ? sched_clock+0x8/0x10
> [<c1075da9>] ? sched_clock_local+0x49/0x180
> [<c109325d>] lock_acquire+0x9d/0x140
> [<f831dd4c>] ? hci_send_acl+0xac/0x290 [bluetooth]
> [<c1889c25>] _raw_spin_lock+0x45/0x80
> [<f831dd4c>] ? hci_send_acl+0xac/0x290 [bluetooth]
> [<f831dd4c>] hci_send_acl+0xac/0x290 [bluetooth]
> [<c108f0b4>] ? mark_held_locks+0x64/0x90
> [<c188a065>] ? _raw_spin_unlock_irqrestore+0x55/0x70
> [<f833efe0>] l2cap_do_send+0x60/0x100 [bluetooth]
> [<c108f32b>] ? trace_hardirqs_on+0xb/0x10
> [<c188a051>] ? _raw_spin_unlock_irqrestore+0x41/0x70
> [<c1763125>] ? skb_dequeue+0x45/0x60
> [<f8349785>] l2cap_recv_frame+0x23e5/0x2dc0 [bluetooth]
> [<c1075da9>] ? sched_clock_local+0x49/0x180
> [<c100a5f8>] ? sched_clock+0x8/0x10
> [<c1075da9>] ? sched_clock_local+0x49/0x180
> [<c10761ef>] ? sched_clock_cpu+0x10f/0x160
> [<c107183b>] ? get_parent_ip+0xb/0x40
> [<c10718bb>] ? preempt_count_add+0x4b/0xa0
> [<c13d09e2>] ? debug_smp_processor_id+0x12/0x20
> [<c108cc04>] ? get_lock_stats+0x24/0x40
> [<c108f0b4>] ? mark_held_locks+0x64/0x90
> [<c188716d>] ? __mutex_unlock_slowpath+0xcd/0x1b0
> [<c13d09ff>] ? __this_cpu_preempt_check+0xf/0x20
> [<c108f1d4>] ? trace_hardirqs_on_caller+0xf4/0x240
> [<c108c9a6>] ? trace_hardirqs_off_caller+0xb6/0x160
> [<f834b6a9>] l2cap_recv_acldata+0x2f9/0x340 [bluetooth]
> [<f8316a13>] ? hci_rx_work+0x113/0x4a0 [bluetooth]
> [<f8316c69>] hci_rx_work+0x369/0x4a0 [bluetooth]
> [<f8316a13>] ? hci_rx_work+0x113/0x4a0 [bluetooth]
> [<c106234a>] process_one_work+0x19a/0x4a0
> [<c10622c3>] ? process_one_work+0x113/0x4a0
> [<c10629e9>] worker_thread+0x39/0x440
> [<c10629b0>] ? init_pwq+0xc0/0xc0
> [<c1066dc8>] kthread+0xa8/0xc0
> [<c108f32b>] ? trace_hardirqs_on+0xb/0x10
> [<c188ad01>] ret_from_kernel_thread+0x21/0x30
> [<c1066d20>] ? kthread_create_on_node+0x160/0x160
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