[PATCH v2 2/2] powerpc: update pci_controller.refcount for PCI devices and buses

[Andrew Donnellan]

On 10/08/16 10:44, Mauricio Faria de Oliveira wrote:
> This patch employs the refcount in struct pci_controller to track
> the references from PCI devices and buses (struct pci_dev/pci_bus).
>
> In order to do that without modifying any PCI scan/probe approach
> (e.g., PCI_PROBE_DEVTREE and PCI_PROBE_NORMAL), it leverages some
> of the PCI arch-specific callback: pci_(add|release)_device() and
> pci_(add|remove)_bus().
>
> (a small change is required for PCI_PROBE_DEVTREE, which makes it
> consistent with PCI_PROBE_NORMAL - the pci_dev should inherit the
> parent pci_bus's phb pointer - see pci_setup_device() in probe.c)
>
> This also has the advantage that locking for kref_(get|put)() is
> satisfied by the 'pci_rescan_remove_lock' mutex, which is normal
> practice for usage of the PCI subsystem - thus already in place.
> More details added in comment on pcibios_release_device().
>
> Signed-off-by: Mauricio Faria de Oliveira <mauricfo at linux.vnet.ibm.com>

>  void pcibios_release_device(struct pci_dev *dev)
>  {
>  	struct pci_controller *phb = pci_bus_to_host(dev->bus);
>
> +	pr_debug("PCI %s, pci_dev %p, phb %p\n", dev_name(&dev->dev), dev, phb);
> +
>  	eeh_remove_device(dev);
>
>  	if (phb->controller_ops.release_device)
>  		phb->controller_ops.release_device(dev);
> +
> +	if (unlikely(!phb))
> +		pr_warn("%s: PCI device %s has null PHB; refcount bug!",
> +			__func__, dev_name(&dev->dev)); /* WARN_ON ahead */

This should probably go before trying to dereference phb->controller_ops 
above?


-- 
Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnellan at au1.ibm.com  IBM Australia Limited