From mboxrd@z Thu Jan  1 00:00:00 1970
From: Shawn Lin <shawn.lin@rock-chips.com>
Subject: System hung for reg_check_changs_work()-> rtnl_lock()->mutex_lock()
Date: Mon, 21 May 2018 11:47:03 +0800
Message-ID: <aa65282a-b7f9-757f-8690-64c27df44e90@rock-chips.com>
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Cc: shawn.lin@rock-chips.com, Dmitry Vyukov <dvyukov@google.com>,
        "David S. Miller" <davem@davemloft.net>,
        syzkaller-bugs@googlegroups.com
To: netdev@vger.kernel.org
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Hi,

I found this hung for several times these days, and seems syzbot already
reported a similar problem. Is there any patch(es) for that?

Successfully initialized wpa_supplicant
[  240.091941] INFO: task kworker/u8:1:39 blocked for more than 120 seconds.
[  240.092004]       Not tainted 4.4.126 #1
[  240.092026] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
disables this message.
[  240.092047] kworker/u8:1    D ffffff8008084dfc     0    39      2 
0x00000000
[  240.092116] Workqueue: events_power_efficient reg_check_chans_work
[  240.092153] Call trace:
[  240.092191] [<ffffff8008084dfc>] __switch_to+0x84/0xa0
[  240.092228] [<ffffff80086299f0>] __schedule+0x428/0x45c
[  240.092260] [<ffffff8008629a98>] schedule+0x74/0x94
[  240.092295] [<ffffff8008629e44>] schedule_preempt_disabled+0x20/0x38
[  240.092332] [<ffffff800862b13c>] __mutex_lock_slowpath+0xc0/0x138
[  240.092364] [<ffffff800862b1e0>] mutex_lock+0x2c/0x40
[  240.092399] [<ffffff80084eb820>] rtnl_lock+0x14/0x1c
[  240.092428] [<ffffff80085ce2a0>] reg_check_chans_work+0x2c/0x1f0
[  240.092463] [<ffffff80080abbac>] process_one_work+0x1b0/0x294
[  240.092494] [<ffffff80080ac904>] worker_thread+0x2d8/0x398
[  240.092524] [<ffffff80080b0f04>] kthread+0xc8/0xd8
[  240.092567] [<ffffff8008082e80>] ret_from_fork+0x10/0x50
[  240.092594] Kernel panic - not syncing: hung_task: blocked tasks
[  240.101163] CPU: 0 PID: 30 Comm: khungtaskd Not tainted 4.4.126 #1
[  240.101729] Hardware name: Rockchip RK3308 evb analog mic board (DT)
[  240.102302] Call trace:
[  240.102546] [<ffffff800808731c>] dump_backtrace+0x0/0x1c4
[  240.103044] [<ffffff80080874f4>] show_stack+0x14/0x1c
[  240.103521] [<ffffff800823f4b4>] dump_stack+0x94/0xbc
[  240.104000] [<ffffff800810a80c>] panic+0xd8/0x228
[  240.104446] [<ffffff80080fb228>] proc_dohung_task_timeout_secs+0x0/0x40
[  240.105050] [<ffffff80080b0f04>] kthread+0xc8/0xd8
[  240.105500] [<ffffff8008082e80>] ret_from_fork+0x10/0x50
[  240.106065] CPU1: stopping
[  240.106348] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.4.126 #1