Re: [PATCH v2 8/8] PCI: pciehp: Check that the device is really present before touching it

[Mika Westerberg]

On Fri, Oct 20, 2017 at 04:15:02PM -0500, Bjorn Helgaas wrote:
> > +
> > +		/* Check if the device is really there anymore */
> > +		present = presence ? pci_device_is_present(dev) : false;
> > +
> > +		if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE && present) {
> >  			pci_read_config_byte(dev, PCI_BRIDGE_CONTROL, &bctl);
> 
> I don't like this fix because it's still racy.  We always have to be deal
> with a config read that returns 0xffffffff, even if we previously checked
> pci_device_is_present().  The device might have disappeared in the interim.

That's a fair point. I guess it is better just to check if bctl holds
0xffff before we decide it is a display device.

I'll rework this patch and send an updated version separately.