Re: [Xen-devel] null pointer in domU

[Tupshin Harper <tupshin@xxxxxxxxxxx>]

Keir Fraser wrote:

> domU got a response from dom0 containing an unexpected request id.
> domU tried to lookup the skbuff corresponding to the id, but read
> garbage (because the id was not currently in use). It crashed when it
> tried to dereference the garbage skbuff pointer.
>
> This is rather nasty -- it's not clear whether dom0 or domU is at
> fault (dom0 may have forgotten about the id, or corrupted its own
> state, or the response from dom0 could be at fault). And it must be
> hard to trigger as we have had no other reports of this. :-(
>
>  -- Keir
>
Well thanks for the analysis :)

And yes, it must be hard to trigger, because I've had multiple weeks of
uptime running 8+ domUs with no problems. It might be interesting that
the domU that crashed is the only one doing routing, and it also was
under a moderately high traffic load at the time that it crashed. If you
have any inclination to add some debug code to try to look for and
analyze this problem, I'd be happy to run custom builds for either my
dom0 or domU.

Thanks.

BTW, is there any reccomended way of detecting a crashed domU and
restarting it?

-Tupshin

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