Re: [PATCH 2/8] powerpc/pci: Don't scan empty slot

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Tue, 2014-11-25 at 09:49 +1100, Gavin Shan wrote:
> In hotplug case, function pcibios_add_pci_devices() is called to
> rescan the specified PCI bus, which possibly doesn't have any child
> devices. Access to the PCI bus's child device node will cause kernel
> crash without exception. The patch adds two more conditions to avoid
> the kernel crash.
> 
> Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
> ---
>  arch/powerpc/kernel/pci-hotplug.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/pci-hotplug.c b/arch/powerpc/kernel/pci-hotplug.c
> index 6e2b4e3..ea5513b 100644
> --- a/arch/powerpc/kernel/pci-hotplug.c
> +++ b/arch/powerpc/kernel/pci-hotplug.c
> @@ -105,7 +105,7 @@ EXPORT_SYMBOL_GPL(pcibios_remove_pci_devices);
>   * is how this routine differs from other, similar pcibios
>   * routines.)
>   */
> -void pcibios_add_pci_devices(struct pci_bus * bus)
> +void pcibios_add_pci_devices(struct pci_bus *bus)

Unrelated whitespace change

>  {
>  	int slotno, mode, pass, max;
>  	struct pci_dev *dev;
> @@ -120,7 +120,8 @@ void pcibios_add_pci_devices(struct pci_bus * bus)
>  	if (mode == PCI_PROBE_DEVTREE) {
>  		/* use ofdt-based probe */
>  		of_rescan_bus(dn, bus);
> -	} else if (mode == PCI_PROBE_NORMAL) {
> +	} else if (mode == PCI_PROBE_NORMAL &&
> +		   dn->child && PCI_DN(dn->child)) {
>  		/*
>  		 * Use legacy probe. In the partial hotplug case, we
>  		 * probably have grandchildren devices unplugged. So