[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 1/3] virtio-ccw: remove qdev_unparent in unplug
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCH 1/3] virtio-ccw: remove qdev_unparent in unplug routing |
Date: |
Mon, 11 Mar 2013 13:04:47 +0100 |
On Fri, 8 Mar 2013 21:11:13 +0100
Alexander Graf <address@hidden> wrote:
>
> On 25.02.2013, at 12:10, Christian Borntraeger wrote:
>
> > On 25/02/13 11:44, Paolo Bonzini wrote:
> >> Il 25/02/2013 09:09, Christian Borntraeger ha scritto:
> >>> Hmm, the old sequence was
> >>>
> >>> object_unparent(OBJECT(dev));
> >>> qdev_free(dev) ---+
> >>> |
> >>> V
> >>> ...
> >>> object_unparent(OBJECT(dev)); now the last reference is gone,
> >>> object is freed
> >>> object_unref(OBJECT(dev)); now the reference of a deleted
> >>> object becomes -1
> >>> ...
> >>>
> >>> Isnt that a problem in itself that we modify a reference counter in an
> >>> deleted object?
> >>
> >> The second object_unparent should do nothing. So before you had:
> >>
> >> object_unparent(OBJECT(dev)); leaves refcount=1
> >> qdev_free(dev) ---+
> >> |
> >> V
> >> object_unparent(OBJECT(dev)); do nothing
> >> object_unref(OBJECT(dev)); refcount=0, object freed
> >>
> >> After the object_unref was removed you had:
> >>
> >> object_unparent(OBJECT(dev)); refcount=0, object freed
> >> qdev_free(dev) ---+
> >> |
> >> V
> >> object_unparent(OBJECT(dev)); dangling pointer!
> >>
> >
> >
> > Got it. Thanks
>
> So is the patch valid?
To my understanding, yes.
>
>
> Alex
>