Re: [Xen-devel] Re: [Xen-changelog] The dom destroy path is doing a dom_get on a non-existent domain to

[Robert Read <robert@xxxxxxxxxxxxx>]

On Sep 14, 2005, at 18:07 , Dan Smith wrote:

> > # HG changeset patch
> > # User shand@xxxxxxxxxxxxxxxxxxxxxxxxxxx
> > # Node ID fb72c78604c673bb07915675620bce3b7630e323
> > # Parent  122779b57b40600dcaf2d147ca82ec23da8e2c96
> <snip>
>
>
> > It then handles the exception in dom_get by returning None, which
> > callers already expect to mean failure.
> This is not actually true, right?  There are several places in the
> code that blindly use the return value of dom_get(), assuming that it
> is actually anything but None.  The closest example is in the update()
> function, several lines down:
>
>   self.info = info or dom_get(self.domid)
Ah, my bad. I misinterpreted this as a boolean expression at first  
glance.  Note, dom_get was already returning None when the domain  
wasn't found, but another exception was preventing it from getting  
that far. We're just moving the exceptions around, now.

>   self.memory = self.info['mem_kb'] / 1024
>
> Clearly, we need to decide what behavior dom_get() is expected to
> have.  Do we expect it to return None if the domid is not found, or do
> we expect the domain we're asking about to always be present
> (i.e. throw an exception if not)?
>
> If nobody has strong feelings either way, I'll work up a patch to fix
> it.
My original fix was to allow dom_get to raise the exception, and I  
just ignored it in delete(), since we are not expecting to find the  
domain in the first place there.  On second thought, this was  
probably a better approach, since the other uses of dom_get would be  
better off if they got exceptions instead of None.
robert

> --
> Dan Smith
> IBM Linux Technology Center
> Open Hypervisor Team
> email: danms@xxxxxxxxxx
>
>
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--
Robert Read
robert@xxxxxxxxxxxxx



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