Re: [Qemu-devel] [PATCH 1.3 0/5] QOM/qdev lifetime fixes

[Anthony Liguori <aliguori@us.ibm.com>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> These patches fix problems in the handling of freeing QOM/qdev
> objects.  Together, they fix hot-unplug of USB mass storage devices,
> which crashed with an assertion failure.
>
> I'm not 100% sure, but I think we were always leaking the scsi-disk in
> pre-QOM days.  Now we're freeing it properly, and the assertion proves it.
>
> However, I don't like particularly the assertion in object_delete.  Once
> we're sure we've fixed all bugs, we should remove it, because it prevents
> a fully correct tracking of references.
>
> In this case, for example, there is still one reference to the scsi-disk
> in the MSDState's scsi_dev member.  We don't have neither an object_ref
> nor an object_unref for it, so it happens to work.  If we had an
> object_ref, the matching object_unref would be in dc->exit.  But then
> we'd trip on the assertion failure again, because the SCSI bus is removed
> (thus calling qdev_free on the scsi-dev) before dc->exit is called.
>
> I have more patches to actually make the reference count of devices
> and buses fully correct, but they are even more scary than these, so
> they should wait for 1.4.
>

Applied. Thanks.

My patches didn't fix Peter's problem but yours do, I figured we'd take
your version in 1.3 and then for 1.4 I can attempt to rework them.

Regards,

Anthony Liguori

> Paolo Bonzini (5):
>   qom: fix refcount of non-heap-allocated objects
>   qdev: move bus removal to object_unparent
>   qom: make object_delete usable for statically-allocated objects
>   qdev: simplify (de)allocation of buses
>   qom: make object_finalize static
>
>  hw/qdev-core.h        |  5 -----
>  hw/qdev.c             | 26 ++++++++++++++------------
>  hw/pci.c              |  2 +-
>  hw/sysbus.c           |  2 +-
>  include/qemu/object.h | 29 ++++++++++++++++++++---------
>  qom/object.c          | 12 +++++++++---
>  6 files changed, 45 insertions(+), 31 deletions(-)
>
> -- 
> 1.8.0