Re: [Qemu-devel] [PATCH 01/15] qdev: do not reset a device until the parent has been initialized

[Michael S. Tsirkin]

On Mon, Dec 17, 2012 at 06:52:03PM +0200, Michael S. Tsirkin wrote:
> On Mon, Dec 17, 2012 at 05:24:36PM +0100, Paolo Bonzini wrote:
> > When a device creates a bus and more devices as part of its init callback, 
> > the
> > child device could be reset while the parent is still only partly 
> > initialized.
> > In this case, the right thing to do is to delay resetting the child.  Do not
> > do it at all in qdev_init, instead use qdev_reset_all to reset 
> > already-created
> > devices when the state goes from CREATED to INITIALIZED.
> > 
> > This happens when hotplugging a usb-storage device.  Without this patch,
> > initialization of a hotplugged usb-storage device would run in pre-order.
> > Initialization of a coldplugged usb-storage device would run according to
> > qdev_reset_all semantics (pre-order right now, post-order later in the
> > series).
> 
> Is this a problem or just not pretty?
> 
> >  This patch makes things consistent.
> > 
> > Signed-off-by: Paolo Bonzini <address@hidden>
> > ---
> >  hw/qdev.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/hw/qdev.c b/hw/qdev.c
> > index 599382c..2fdf4ac 100644
> > --- a/hw/qdev.c
> > +++ b/hw/qdev.c
> > @@ -176,8 +176,9 @@ int qdev_init(DeviceState *dev)
> >                                         dev->alias_required_for_version);
> >      }
> >      dev->state = DEV_STATE_INITIALIZED;
> > -    if (dev->hotplugged) {
> > -        device_reset(dev);
> > +    if (dev->hotplugged &&
> > +        dev->parent_bus->parent->state == DEV_STATE_INITIALIZED) {
> > +        qdev_reset_all(dev);
> 
> Let's add a comment explaining the why of this test, and when
> will reset happen if it does not trigger here.

Also - shouldn't device init be delayed as well?
What do you think?

> >      }
> >      return 0;
> >  }
> > -- 
> > 1.8.0.2
> >