Re: [Qemu-devel] [for-2.12 6/7] pci: Eliminate redundant PCIDevice::bus pointer

[Marcel Apfelbaum]

On 29/11/2017 13:41, Eduardo Habkost wrote:
> On Wed, Nov 29, 2017 at 12:54:04PM +0200, Marcel Apfelbaum wrote:
> > On 29/11/2017 10:46, David Gibson wrote:
> > > The bus pointer in PCIDevice is basically redundant with QOM information.
> > > It's always initialized to the qdev_get_parent_bus(), the only difference
> > > is the type.
> > >
> > > Therefore this patch eliminates the field, instead creating a pci_get_bus()
> > > helper to do the type mangling to derive it conveniently from the QOM
> > > Device object underneath.
> >
> >
> > Hi David,
> >
> > I personally don't see why the caching of the bus bothers you.
> > It makes the code a little easier to read, but indeed is a duplication
> > of data; let's see what Michael has to say, is a matter of
> > taste I suppose.
>
> I'm all for removing duplication of data because it makes the
> code less fragile.  We don't even take care of clearing
> pci_dev->bus when the device is removed from the bus, so there's
> a window between unplugging a device and actually freeing the
> object where pci_dev->bus can become a dangling pointer.

This is a good point.

Reviewed-by: Marcel Apfelbaum <address@hidden>

Thanks,
Marcel

> Reviewed-by: Eduardo Habkost <address@hidden>