PCI: Hold pci_slot_mutex while searching bus->slots list

Previously, pci_setup_device() and similar functions searched the
pci_bus->slots list without any locking. It was possible for another
thread to update the list while we searched it.

Add pci_dev_assign_slot() to search the list while holding pci_slot_mutex.

[bhelgaas: changelog, fold in CONFIG_SYSFS fix]
Tested-by: Guenter Roeck <[e-mail]>
Signed-off-by: Yijing Wang <[e-mail]>
Signed-off-by: Bjorn Helgaas <[e-mail]>

arch/powerpc/kernel/pci_of_scan.c

···
 {
 	struct pci_dev *dev;
 	const char *type;
-	struct pci_slot *slot;
 
 	dev = pci_alloc_dev(bus);
 	if (!dev)
···
 	dev->needs_freset = 0;		/* pcie fundamental reset required */
 	set_pcie_port_type(dev);
 
-	list_for_each_entry(slot, &dev->bus->slots, list)
-		if (PCI_SLOT(dev->devfn) == slot->number)
-			dev->slot = slot;
-
+	pci_dev_assign_slot(dev);
 	dev->vendor = get_int_prop(node, "vendor-id", 0xffff);
 	dev->device = get_int_prop(node, "device-id", 0xffff);
 	dev->subsystem_vendor = get_int_prop(node, "subsystem-vendor-id", 0);

arch/sparc/kernel/pci.c

···
 					 struct pci_bus *bus, int devfn)
 {
 	struct dev_archdata *sd;
-	struct pci_slot *slot;
 	struct platform_device *op;
 	struct pci_dev *dev;
 	const char *type;
···
 	dev->multifunction = 0;		/* maybe a lie? */
 	set_pcie_port_type(dev);
 
-	list_for_each_entry(slot, &dev->bus->slots, list)
-		if (PCI_SLOT(dev->devfn) == slot->number)
-			dev->slot = slot;
-
+	pci_dev_assign_slot(dev);
 	dev->vendor = of_getintprop_default(node, "vendor-id", 0xffff);
 	dev->device = of_getintprop_default(node, "device-id", 0xffff);
 	dev->subsystem_vendor =

drivers/pci/probe.c

···
 {
 	u32 class;
 	u8 hdr_type;
-	struct pci_slot *slot;
 	int pos = 0;
 	struct pci_bus_region region;
 	struct resource *res;
···
 	dev->error_state = pci_channel_io_normal;
 	set_pcie_port_type(dev);
 
-	list_for_each_entry(slot, &dev->bus->slots, list)
-		if (PCI_SLOT(dev->devfn) == slot->number)
-			dev->slot = slot;
-
+	pci_dev_assign_slot(dev);
 	/* Assume 32-bit PCI; let 64-bit PCI cards (which are far rarer)
 	   set this higher, assuming the system even supports it.  */
 	dev->dma_mask = 0xffffffff;

drivers/pci/slot.c

···
 	return result;
 }
 
+void pci_dev_assign_slot(struct pci_dev *dev)
+{
+	struct pci_slot *slot;
+
+	mutex_lock(&pci_slot_mutex);
+	list_for_each_entry(slot, &dev->bus->slots, list)
+		if (PCI_SLOT(dev->devfn) == slot->number)
+			dev->slot = slot;
+	mutex_unlock(&pci_slot_mutex);
+}
+
 static struct pci_slot *get_slot(struct pci_bus *parent, int slot_nr)
 {
 	struct pci_slot *slot;

include/linux/pci.h

···
 				 const char *name,
 				 struct hotplug_slot *hotplug);
 void pci_destroy_slot(struct pci_slot *slot);
+#ifdef CONFIG_SYSFS
+void pci_dev_assign_slot(struct pci_dev *dev);
+#else
+static inline void pci_dev_assign_slot(struct pci_dev *dev) { }
+#endif
 int pci_scan_slot(struct pci_bus *bus, int devfn);
 struct pci_dev *pci_scan_single_device(struct pci_bus *bus, int devfn);
 void pci_device_add(struct pci_dev *dev, struct pci_bus *bus);