Merge branch 'pci/locking'

- Make pci_stop_dev() and pci_destroy_dev() concurrent safe (Keith Busch)

- Move __pci_walk_bus() mutex up into the caller, which avoids the need for
  a parameter to control locking (Keith Busch)

- Simplify __pci_walk_bus() by making it recursive (Keith Busch)

- Unexport pci_walk_bus_locked(), which is only used internally by the PCI
  core (Keith Busch)

* pci/locking:
  PCI: Unexport pci_walk_bus_locked()
  PCI: Convert __pci_walk_bus() to be recursive
  PCI: Move __pci_walk_bus() mutex to where we need it
  PCI: Make pci_destroy_dev() concurrent safe
  PCI: Make pci_stop_dev() concurrent safe

3 files changed, 44 insertions, 46 deletions

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index e0a2441be6d3..d015d5821cef 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -358,7 +358,7 @@ void pci_bus_add_device(struct pci_dev *dev)
 	if (retval < 0 && retval != -EPROBE_DEFER)
 		pci_warn(dev, "device attach failed (%d)\n", retval);
 
-	pci_dev_assign_added(dev, true);
+	pci_dev_assign_added(dev);
 
 	if (dev_of_node(&dev->dev) && pci_is_bridge(dev)) {
 		retval = of_platform_populate(dev_of_node(&dev->dev), NULL, NULL,
@@ -399,41 +399,23 @@ void pci_bus_add_devices(const struct pci_bus *bus)
 }
 EXPORT_SYMBOL(pci_bus_add_devices);
 
-static void __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
-			   void *userdata, bool locked)
+static int __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
+			  void *userdata)
 {
 	struct pci_dev *dev;
-	struct pci_bus *bus;
-	struct list_head *next;
-	int retval;
+	int ret = 0;
 
-	bus = top;
-	if (!locked)
-		down_read(&pci_bus_sem);
-	next = top->devices.next;
-	for (;;) {
-		if (next == &bus->devices) {
-			/* end of this bus, go up or finish */
-			if (bus == top)
+	list_for_each_entry(dev, &top->devices, bus_list) {
+		ret = cb(dev, userdata);
+		if (ret)
+			break;
+		if (dev->subordinate) {
+			ret = __pci_walk_bus(dev->subordinate, cb, userdata);
+			if (ret)
 				break;
-			next = bus->self->bus_list.next;
-			bus = bus->self->bus;
-			continue;
 		}
-		dev = list_entry(next, struct pci_dev, bus_list);
-		if (dev->subordinate) {
-			/* this is a pci-pci bridge, do its devices next */
-			next = dev->subordinate->devices.next;
-			bus = dev->subordinate;
-		} else
-			next = dev->bus_list.next;
-
-		retval = cb(dev, userdata);
-		if (retval)
-			break;
 	}
-	if (!locked)
-		up_read(&pci_bus_sem);
+	return ret;
 }
 
 /**
@@ -451,7 +433,9 @@ static void __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void
  */
 void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *), void *userdata)
 {
-	__pci_walk_bus(top, cb, userdata, false);
+	down_read(&pci_bus_sem);
+	__pci_walk_bus(top, cb, userdata);
+	up_read(&pci_bus_sem);
 }
 EXPORT_SYMBOL_GPL(pci_walk_bus);
 
@@ -459,9 +443,8 @@ void pci_walk_bus_locked(struct pci_bus *top, int (*cb)(struct pci_dev *, void *
 {
 	lockdep_assert_held(&pci_bus_sem);
 
-	__pci_walk_bus(top, cb, userdata, true);
+	__pci_walk_bus(top, cb, userdata);
 }
-EXPORT_SYMBOL_GPL(pci_walk_bus_locked);
 
 struct pci_bus *pci_bus_get(struct pci_bus *bus)
 {
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 1d5c519e19b1..0024eb0f3e0e 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -323,6 +323,9 @@ void __pci_bus_assign_resources(const struct pci_bus *bus,
 				struct list_head *realloc_head,
 				struct list_head *fail_head);
 bool pci_bus_clip_resource(struct pci_dev *dev, int idx);
+void pci_walk_bus_locked(struct pci_bus *top,
+			 int (*cb)(struct pci_dev *, void *),
+			 void *userdata);
 
 const char *pci_resource_name(struct pci_dev *dev, unsigned int i);
 
@@ -493,10 +496,18 @@ static inline int pci_dev_set_disconnected(struct pci_dev *dev, void *unused)
 #define PCI_DEV_ADDED 0
 #define PCI_DPC_RECOVERED 1
 #define PCI_DPC_RECOVERING 2
+#define PCI_DEV_REMOVED 3
 
-static inline void pci_dev_assign_added(struct pci_dev *dev, bool added)
+static inline void pci_dev_assign_added(struct pci_dev *dev)
 {
-	assign_bit(PCI_DEV_ADDED, &dev->priv_flags, added);
+	smp_mb__before_atomic();
+	set_bit(PCI_DEV_ADDED, &dev->priv_flags);
+	smp_mb__after_atomic();
+}
+
+static inline bool pci_dev_test_and_clear_added(struct pci_dev *dev)
+{
+	return test_and_clear_bit(PCI_DEV_ADDED, &dev->priv_flags);
 }
 
 static inline bool pci_dev_is_added(const struct pci_dev *dev)
@@ -504,6 +515,11 @@ static inline bool pci_dev_is_added(const struct pci_dev *dev)
 	return test_bit(PCI_DEV_ADDED, &dev->priv_flags);
 }
 
+static inline bool pci_dev_test_and_set_removed(struct pci_dev *dev)
+{
+	return test_and_set_bit(PCI_DEV_REMOVED, &dev->priv_flags);
+}
+
 #ifdef CONFIG_PCIEAER
 #include <linux/aer.h>
 
diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
index e4ce1145aa3e..1f35945459fd 100644
--- a/drivers/pci/remove.c
+++ b/drivers/pci/remove.c
@@ -33,21 +33,20 @@ static void pci_stop_dev(struct pci_dev *dev)
 {
 	pci_pme_active(dev, false);
 
-	if (pci_dev_is_added(dev)) {
-		device_for_each_child(dev->dev.parent, dev_of_node(&dev->dev),
-				      pci_pwrctl_unregister);
-		device_release_driver(&dev->dev);
-		pci_proc_detach_device(dev);
-		pci_remove_sysfs_dev_files(dev);
-		of_pci_remove_node(dev);
-
-		pci_dev_assign_added(dev, false);
-	}
+	if (!pci_dev_test_and_clear_added(dev))
+		return;
+
+	device_for_each_child(dev->dev.parent, dev_of_node(&dev->dev),
+			      pci_pwrctl_unregister);
+	device_release_driver(&dev->dev);
+	pci_proc_detach_device(dev);
+	pci_remove_sysfs_dev_files(dev);
+	of_pci_remove_node(dev);
 }
 
 static void pci_destroy_dev(struct pci_dev *dev)
 {
-	if (!dev->dev.kobj.parent)
+	if (pci_dev_test_and_set_removed(dev))
 		return;
 
 	pci_npem_remove(dev);