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Re: [Xen-devel] xen-4.6: xenstored crashes during domain->interface access

On 26.01.2016 11:58, Stefan Bader wrote:
> Hi,
> while playing around with xen-4.6 I stumbled over an odd problem and am
> wondering whether anybody has seen the same. A method to relatively quickly
> reproduce this for me seems to:
> - Start one domU (PV or HVM does not seem to matter)
> - Repeatedly call xenstore-ls a few times
> I think I never got beyond 10 repeats when the xenstore-ls call suddenly locks
> up and xenstored crashes with a SIGBUS error. In the majority of cases (I 
> think
> I saw one different), the crash happens while accessing 
> conn->domain->interface
> in tools/xenstore/xenstored_domain.c:domain_can_read().
> Looking at the corefile produced by xenstored I now got at least one case 
> where
> the pointer still matches the previously mapped value. Though I think I had 
> also
> at least one run (with less debugging added) where it seemed to be really 
> wrong.
> There is more info at [1] in case someone is interested.
> I need to repeat a few more times to see how consistent the whole thing is. 
> Does
> this happen for anybody else? Any advice what I should look at (in the sense 
> of
> gathering better data)?

Just as an update and confirmation for Ian and Bastian: Debian testing is fine.
I have not dug into the specifics but its not the Xen package side at all.
Something in our 4.3 kernel causes this. Unfortunately without any hint in
dmesg. But since we move to 4.4 soon and I cannot reproduce it with the pending
4.4 build it seems good enough to me.

> Thanks,
> Stefan
> [1] https://bugs.launchpad.net/ubuntu/+source/xen/+bug/1538049

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