Re: [PATCH]xend: fix dual destroy

[Jim Fehlig <jfehlig@novell.com>]

Cui, Dexuan wrote:
> After changeset 18030 and 18064 were checked in, I found some issues
> when creating HVM domains with devices assigned:
>
> In XendDomainInfo.py, we have the call trace: the global function
> create() => vm.start()  => _constructDomain().
> In _constructDomain(), we invoke xc.test_assign_device() and when the
> function fails (maybe because iommu=1 is not specified in grub entry
> since iommu is 0 by defaut now; maybe because the device doesn't exist;
> maybe because the device has been assigned, or something) we raise
> VmError;
> Then start() will invoke self.destroy() and re-raise the exception;
> Next, the global create() will invoke vm.destroy() again; finally,
> _cleanupVm()  and "self.metrics.destroy()" will be invoked again. Here
> when we execute metrics.destroy() for the second time, the deregister()
> in XendAPIStore.py will complain: there is no such an element in the
> dict __classes and a KeyError exception is raised!
>
> We can avoid the dual destroy by adding a check as follows.
>   

Thanks.  Finding the right place to destroy the metrics object made me 
quite nervous.  Thought I had been through enough testing after c/s 
18064 to have gotten it right :-/.  Even more discouraging - xend still 
has a significant leak.

Jim