Re: [Xen-devel] Xen 4.7 crash

[Aaron Cornelius <aaron.cornelius@xxxxxxxxxxxxxxx>]

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

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