INFO: task snmpd:398 blocked for more than 120 seconds.

[Norbert van Bolhuis]

Joakim Tjernlund wrote:
>>> I can't make out what is causing this hang every now an then:
>>>
>>> INFO: task snmpd:398 blocked for more than 120 seconds.
>> My problem with that 'error' message is that there is no way
>> for a driver to disable it on a per-process basis.
>> We have some processes whose 'normal state' is to sleep
>> uninterruptibly in the kernel. Shutdown is handled by
>> an explicit request (not by sending a signal).
>> The processes could be kernel worker threads (except that
>> is is ~impossible to handle them exiting from a loadble
>> kernel module) so are actually children of a daemon sat
>> inside an ioctl() request that never terminates!
>>
>> However, on the face of it, your case does look as though
>> the mutex is fubar'ed.
>>
>> Might be worth (somehow) dumping the mutex state.
> 
> ehh, it is locked, isn't it? How to find who locked it
> and forgot to release it?
> 

You could add show_state to check_hung_task

It worked for me while solving some (application) task hangups.

---
N. van Bolhuis.