On Tue, Dec 31, 2013 at 05:06:44PM +0100, Paolo Bonzini wrote:
> Il 31/12/2013 09:06, Amos Kong ha scritto:
> > When it fails to set properties, qdev's parent is already set
>
> Do not confuse the QOM parent (which is /machine/peripheral, of which
> the new device is a child) with the qdev parent bus (which has a link to
> the new device)!
>
> In general, you should add the device to the QOM tree before using it to
> set a link. So I believe that object_property_add_child should be
> called before qdev_set_parent_bus. This is the root cause of the bug;
> the fix then could be one of the following:
>
> 1) move qdev_set_parent_bus later;
>
> 2) move object_property_add_child before the setting of properties.
I agree to fix this problem by adjust the initialization order.
Thanks for the detail explain.
> I slightly prefer the first, so that initialization happens in this order:
>
> 1) create object
>
> 2) set properties -- if it fails, you can just unref the object
>
> 3) add child -- if it fails due to duplicate ID, you can again just
> unref the object
>
> 4) set parent bus (cannot fail)
>
> 5) realize -- if it fails, you need to unparent the object and unref the
> object
>
> 6) drop the reference now that the object is kept solidly alive by
> QOM/qdev, and return.
>
> This matches a bit more closely what happens with object-add, too.
>
> Paolo
--
Amos.
