Re: [Qemu-devel] [PATCH 01/16] qdev: fix hot-unplug

[Paolo Bonzini <pbonzini@redhat.com>]

On 02/03/2012 03:27 PM, Anthony Liguori wrote:
> On 02/02/2012 10:45 AM, Paolo Bonzini wrote:
>> The reference that is returned by qdev_device_add is never given
>> back, so that device_del does not cause the refcount to go to zero
>> (and thus does nothing).
>>
>> Signed-off-by: Paolo Bonzini<pbonzini@redhat.com>
>
> This isn't needed in qom-upstream.14. Here's why:
>
> object_init does not increase the reference count
>
> object_property_add_child increases the reference count
> object_new increases the reference count
>
> object_delete decrements the reference count
> object_property_del_child decreases the reference count
>
> object_delete calls object_property_del_child(obj->parent, obj)
>
> qdev_device_add calls object_new and object_property_add_child
> -> ref == 2
>
> qdev_device_del calls object_delete
> -> ref -= 2
>
> In qom-upstream.13, object_delete wasn't calling
> object_property_del_child which is why you saw the behavior you did.
> This problem would still exist with a composed device so dropping the
> reference here isn't enough.

I trust you for now. :)

It really seems like my patch is obviously correct so, if it's not 
needed anymore there may be another bug elsewhere that masks it.

Paolo