netdev - mlx5: net_device.addr_list_lock usage before initialization

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Date:   Tue, 13 Dec 2016 14:22:46 +0100 (CET)
From:   Sebastian Ott <sebott@...ux.vnet.ibm.com>
To:     Saeed Mahameed <saeedm@...lanox.com>,
        Matan Barak <matanb@...lanox.com>,
        Leon Romanovsky <leonro@...lanox.com>
cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: mlx5: net_device.addr_list_lock usage before initialization

Hi,

I ran into the following lockdep complaint:

[    7.059561] INFO: trying to register non-static key.
[    7.059566] the code is fine but needs lockdep annotation.
[    7.059570] turning off the locking correctness validator.
[    7.059579] CPU: 6 PID: 6 Comm: kworker/u32:0 Not tainted 4.9.0-02683-g784243e-dirty #77
[    7.059582] Hardware name: IBM              2964 N96              704              (LPAR)
[    7.061260] Workqueue: mlx5e mlx5e_set_rx_mode_work [mlx5_core]
[    7.061268] Stack:
[    7.061270]        00000000f95739c0 00000000f9573a50 0000000000000003 0000000000000000
[    7.061278]        00000000f9573af0 00000000f9573a68 00000000f9573a68 0000000000000020
[    7.061286]        0000000000000000 0000000000000020 000000000000000a 000000000000000a
[    7.061294]        000000000000000c 00000000f9573ab8 0000000000000000 0000000000000000
[    7.061301]        00000000008a1038 0000000000112a50 00000000f9573a50 00000000f9573aa8
[    7.061314] Call Trace:
[    7.061321] ([<000000000011292a>] show_trace+0x8a/0xe0)
[    7.061327]  [<0000000000112a00>] show_stack+0x80/0xd8
[    7.061334]  [<00000000005cdce6>] dump_stack+0x96/0xd8
[    7.061338]  [<00000000001ae352>] register_lock_class+0x1d2/0x530
[    7.061341]  [<00000000001b33f6>] __lock_acquire+0xfe/0x7d8
[    7.061345]  [<00000000001b4394>] lock_acquire+0x30c/0x358
[    7.061352]  [<000000000089454c>] _raw_spin_lock_bh+0x64/0xa0
[    7.062171]  [<000003ff81465858>] mlx5e_set_rx_mode_work+0x248/0x490 [mlx5_core]
[    7.062178]  [<0000000000163864>] process_one_work+0x41c/0x830
[    7.062181]  [<0000000000163f2c>] worker_thread+0x2b4/0x478
[    7.062186]  [<000000000016c46c>] kthread+0x15c/0x170
[    7.062190]  [<0000000000895a52>] kernel_thread_starter+0x6/0xc
[    7.062193]  [<0000000000895a4c>] kernel_thread_starter+0x0/0xc
[    7.062196] INFO: lockdep is turned off.

The problematic lock is net_device.addr_list_lock whose usage is
asynchronously triggered by:

mlx5e_add -> mlx5e_attach -> mlx5e_attach_netdev -> mlx5e_nic_enable 
[workq] mlx5e_set_rx_mode_work -> mlx5e_handle_netdev_addr -> mlx5e_sync_netdev_addr

Initialization of this lock is triggered by:
mlx5e_add -> register_netdev

...after the call to mlx5e_attach which is obviously racy.

Regards,
Sebastian