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.