Panic in the udp_input() under heavy load

Maxim Sobolev sobomax at
Mon Nov 7 22:58:07 UTC 2011

On 11/7/2011 10:24 AM, Bjoern A. Zeeb wrote:
> Unlikely; the inp is properly locked there and the udp info attach
> better still be valid there; your problem is most likely elsewhere;
> try to see if you have other threads and see what they do at the same
> time, etc.  You would need to race with udp_detach();  you also want
> to make sure that the inp still looks sane from either ddb or a dump
> and we are not talking about random memory corruption here.

Well, as you can see from the trace it points pretty strongly to that 
piece of code. And as I said this panic is completely reproducible, 
we've seen it at least 5 times to date in exactly this location. 
Unfortunately the trace is rather long so we could not capture it in 
full before, until we've switched to the 80x50 mode.

If it was a memory corruption it would be just random fault, while here 
we have it failing in this point reliably.

Unfortunately the panic happens in the driver thread context (I 
believe), so the KDB/dump is not working. After panicing the machine 
just hangs there. Keyboard is not working and I need to do a hard reset.

Is there any other explanation that you can think of? Is it possible for 
some other portion of the code (i.e. network driver, DMA engine etc) to 
trash this structure by writing something off bound? Or something along 
the lines?


Maksym Sobolyev
Sippy Software, Inc.
Internet Telephony (VoIP) Experts
Tel: +1-646-651-1110
Fax: +1-866-857-6942
MSN: sales at
Skype: SippySoft

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