Re: QEMU device refcounting when device creates a container MR

[Igor Mammedov]

Do On Thu, 10 Mar 2022 16:05:24 +0000
Peter Maydell <peter.maydell@linaro.org> wrote:

> On Thu, 10 Mar 2022 at 15:36, Igor Mammedov <imammedo@redhat.com> wrote:
> >
> > On Wed, 9 Mar 2022 16:56:21 +0000
> > Peter Maydell <peter.maydell@linaro.org> wrote:  
> > > ...also, in the device-introspect-test where I see this problem,
> > > unrealize is never going to be called anyway, because the device
> > > is only put through "instance_init" and then dereffed (which
> > > does not result in instance_finalize being called, because the
> > > refcount is still non-zero).  
> >
> > question is why introspected device is deferred instead of being
> > destroyed if it's no longer needed?  
> 
> ...because the reference count is not zero.
> 
> What is supposed to happen is:
>  * device is created (inited), and has refcount of 1
>  * introspection code does its thing
>  * introspection code derefs the device, and it gets deinited
> 
> This bug means that when the device is inited it has a refcount
> that is too high, and so despite the code that creates it
> correctly dereffing it, it's still lying around.

looks like ref count leak somewhere, instance_finalize() take care
of cleaning up instance_init() actions.
Do you have an example/reproducer?

> thanks
> -- PMM
>