# What's the error: Khelp module "ertt" unload ...



## elimelech007 (Feb 22, 2021)

When the system shuts down, it writes the following error: 


```
Khelp module "ertt" unload until its refcount drops from 1 to 0
```


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## PMc (Feb 22, 2021)

That seems normal.

This is some module that allows to plug in routines into the tcp handling, in order to change anti-congestion schemes and such (and probably other things, but that is what it is commonly used for).
I doubt that the tcp stack is fully unraveled at shutdown, so probably this thing does not reach a state where it could cleanly let go.


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## Mjölnir (Feb 23, 2021)

It would be interesting to know which parts of the kernel keep working when the system is shut down.  IIRC the machine replies to ICMP packets and goes back online on a WOL?


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## PMc (Feb 23, 2021)

Mjölnir said:


> It would be interesting to know which parts of the kernel keep working when the system is shut down.  IIRC the machine replies to ICMP packets and goes back online on a WOL?


I'm not sure about the WOL. What I can see is undeliverable packets being reported until very late (and then I don't know if the reporting or rather the ip is shut down). I think there is just no point in removing the ip-stack, and probably nobody ever considered how it could be done.
Then these khelp/ertt things, they do congestion control in a stateful fashion, so as they keep states of things, they will always have a refcount as long as packets can flow.


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