Re: Xen 4.7 crash

[Aaron Cornelius <aaron.cornelius@dornerworks.com>]

On 6/7/2016 5:53 AM, Ian Jackson wrote:
> Aaron Cornelius writes ("Re: [Xen-devel] Xen 4.7 crash"):
>> We realized that we had forgotten to remove the domain from the
>> permissions list when the domain is deleted (which would cause the error
>> we saw).  The application was updated to remove the domain from the
>> permissions list:
>> 1. retrieve the permissions with xs_get_permissions()
>> 2. find the domain ID that is being deleted
>> 3. memmove() the remaining domains down by 1 to "delete" the old domain
>> from the permissions list
>> 4. update the permissions with xs_set_permissions()
>>
>> After we made that change, a load test over the weekend confirmed that
>> the Xen crash no longer happens.  We checked this morning first thing
>> and confirmed that without this change the crash reliably occurs.
>
> This is rather odd behaviour.  I don't think xenstored should hang
> onto the domain's xs ring page just because the domain is still
> mentioned in a permission list.
>
> But it may do.  I haven't checked the code.  Are you using the
> ocaml xenstored (oxenstored) or the C one ?

I didn't remember specifying anything special when building the xen 
tools, but I did run into troubles where the ocaml tools appeared to 
conflict with the opam installed mirage packages and libraries. Running 
"sudo make dist-install" command installs the ocaml libraries as root 
which made using opam difficult.  So I did disable the ocaml tools 
during my build.

I double checked and confirmed that the C version of xenstored was 
built.  We will try to test the failure scenario with oxenstored to see 
if it behaves any differently.

- Aaron

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel