task kworker/u:0 blocked for more than 120 seconds

[Lei Wen]

Hi list,

I recently find a strange issue over 3.4 kernel.
The scenario is doing the hotplug test over ARM platfrom, and when the
hotplugged
out cpu1 want to get back in again, seems it stuck at cpu_stop_cpu_callback.

The task backtrace is as below:
PID: 21749  TASK: d194b300  CPU: 0   COMMAND: "kworker/u:0"
 #0 [<c05d6ff0>] (__schedule) from [<c05d5604>]
 #1 [<c05d5604>] (schedule_timeout) from [<c05d6a34>]
 #2 [<c05d6a34>] (wait_for_common) from [<c01543c8>]
 #3 [<c01543c8>] (kthread_create_on_node) from [<c05cf524>]
 #4 [<c05cf524>] (cpu_stop_cpu_callback) from [<c0159664>]
 #5 [<c0159664>] (notifier_call_chain) from [<c0139a84>]
 #6 [<c0139a84>] (__cpu_notify) from [<c05cdda4>]
 #7 [<c05cdda4>] (_cpu_up) from [<c05cdeb0>]
 #8 [<c05cdeb0>] (cpu_up) from [<c05c3bf8>]
 #9 [<c05c3bf8>] (hotplug_timer) from [<c014fe24>]
#10 [<c014fe24>] (process_one_work) from [<c0150240>]
#11 [<c0150240>] (worker_thread) from [<c01541b4>]
#12 [<c01541b4>] (kthread) from [<c0113ed8>]

Since I have full memory dump, and could do further analysis, do you
have any idea
that what kind of info need to provide to get it root caused?

Thanks,
Lei
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