PCI: add locking to the pci device lists.

This also creates two new functions, pci_get_device() and pci_get_subsys()
which should be used from now on instead of pci_find_device() and
pci_find_subsys().

Thanks to Chris Wright and Andrew Morton for help in reviewing these changes.

drivers/pci/hotplug.c

@@ -173,6 +173,24 @@ int pci_visit_dev (struct pci_visit *fn, struct pci_dev_wrapped *wrapped_dev,
 }
 EXPORT_SYMBOL(pci_visit_dev);
 
+static void pci_destroy_dev(struct pci_dev *dev)
+{
+	pci_proc_detach_device(dev);
+	device_unregister(&dev->dev);
+
+	/* Remove the device from the device lists, and prevent any further
+	 * list accesses from this device */
+	spin_lock(&pci_bus_lock);
+	list_del(&dev->bus_list);
+	list_del(&dev->global_list);
+	dev->bus_list.next = dev->bus_list.prev = NULL;
+	dev->global_list.next = dev->global_list.prev = NULL;
+	spin_unlock(&pci_bus_lock);
+
+	pci_free_resources(dev);
+	pci_put_dev(dev);
+}
+
 /**
  * pci_remove_device_safe - remove an unused hotplug device
  * @dev: the device to remove
@@ -186,11 +204,7 @@ int pci_remove_device_safe(struct pci_dev *dev)
 {
 	if (pci_dev_driver(dev))
 		return -EBUSY;
-	device_unregister(&dev->dev);
-	list_del(&dev->bus_list);
-	list_del(&dev->global_list);
-	pci_free_resources(dev);
-	pci_proc_detach_device(dev);
+	pci_destroy_dev(dev);
 	return 0;
 }
 EXPORT_SYMBOL(pci_remove_device_safe);
@@ -237,17 +251,15 @@ void pci_remove_bus_device(struct pci_dev *dev)
 		pci_remove_behind_bridge(dev);
 		pci_proc_detach_bus(b);
 
+		spin_lock(&pci_bus_lock);
 		list_del(&b->node);
+		spin_unlock(&pci_bus_lock);
+
 		kfree(b);
 		dev->subordinate = NULL;
 	}
 
-	device_unregister(&dev->dev);
-	list_del(&dev->bus_list);
-	list_del(&dev->global_list);
-	pci_free_resources(dev);
-	pci_proc_detach_device(dev);
-	pci_put_dev(dev);
+	pci_destroy_dev(dev);
 }
 
 /**

drivers/pci/pci.h

@@ -58,3 +58,6 @@ struct pci_visit {
 extern int pci_visit_dev(struct pci_visit *fn,
 			 struct pci_dev_wrapped *wrapped_dev,
 			 struct pci_bus_wrapped *wrapped_parent);
+
+/* Lock for read/write access to pci device and bus lists */
+extern spinlock_t pci_bus_lock;

drivers/pci/proc.c

@@ -308,39 +308,45 @@ static struct file_operations proc_bus_pci_operations = {
 /* iterator */
 static void *pci_seq_start(struct seq_file *m, loff_t *pos)
 {
-	struct list_head *p = &pci_devices;
+	struct pci_dev *dev = NULL;
 	loff_t n = *pos;
 
-	/* XXX: surely we need some locking for traversing the list? */
+	dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, dev);
 	while (n--) {
-		p = p->next;
-		if (p == &pci_devices)
-			return NULL;
+		dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, dev);
+		if (dev == NULL)
+			goto exit;
 	}
-	return p;
+exit:
+	return dev;
 }
+
 static void *pci_seq_next(struct seq_file *m, void *v, loff_t *pos)
 {
-	struct list_head *p = v;
+	struct pci_dev *dev = v;
+
 	(*pos)++;
-	return p->next != &pci_devices ? (void *)p->next : NULL;
+	dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, dev);
+	return dev;
 }
+
 static void pci_seq_stop(struct seq_file *m, void *v)
 {
-	/* release whatever locks we need */
+	if (v) {
+		struct pci_dev *dev = v;
+		pci_put_dev(dev);
+	}
 }
 
 static int show_device(struct seq_file *m, void *v)
 {
-	struct list_head *p = v;
-	const struct pci_dev *dev;
+	const struct pci_dev *dev = v;
 	const struct pci_driver *drv;
 	int i;
 
-	if (p == &pci_devices)
+	if (dev == NULL)
 		return 0;
 
-	dev = pci_dev_g(p);
 	drv = pci_dev_driver(dev);
 	seq_printf(m, "%02x%02x\t%04x%04x\t%x",
 			dev->bus->number,
@@ -455,19 +461,18 @@ int pci_proc_detach_bus(struct pci_bus* bus)
  */
 static int show_dev_config(struct seq_file *m, void *v)
 {
-	struct list_head *p = v;
-	struct pci_dev *dev;
+	struct pci_dev *dev = v;
+	struct pci_dev *first_dev;
 	struct pci_driver *drv;
 	u32 class_rev;
 	unsigned char latency, min_gnt, max_lat, *class;
 	int reg;
 
-	if (p == &pci_devices) {
+	first_dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, NULL);
+	if (dev == first_dev)
 		seq_puts(m, "PCI devices found:\n");
-		return 0;
-	}
+	pci_put_dev(first_dev);
 
-	dev = pci_dev_g(p);
 	drv = pci_dev_driver(dev);
 
 	pci_read_config_dword(dev, PCI_CLASS_REVISION, &class_rev);

drivers/pci/search.c

+/*
+ * 	PCI searching functions.
+ *
+ *	Copyright 1993 -- 1997 Drew Eckhardt, Frederic Potter,
+ *				David Mosberger-Tang
+ *	Copyright 1997 -- 2000 Martin Mares <mj@ucw.cz>
+ *	Copyright 2003 -- Greg Kroah-Hartman <greg@kroah.com>
+ */
+
 #include <linux/pci.h>
 #include <linux/module.h>
 
+spinlock_t pci_bus_lock = SPIN_LOCK_UNLOCKED;
+
 static struct pci_bus *
 pci_do_find_bus(struct pci_bus* bus, unsigned char busnr)
 {
@@ -52,11 +63,15 @@ pci_find_bus(unsigned char busnr)
 struct pci_bus * 
 pci_find_next_bus(const struct pci_bus *from)
 {
-	struct list_head *n = from ? from->node.next : pci_root_buses.next;
+	struct list_head *n;
 	struct pci_bus *b = NULL;
 
+	WARN_ON(irqs_disabled());
+	spin_lock(&pci_bus_lock);
+	n = from ? from->node.next : pci_root_buses.next;
 	if (n != &pci_root_buses)
 		b = pci_bus_b(n);
+	spin_unlock(&pci_bus_lock);
 	return b;
 }
 
@@ -97,24 +112,36 @@ pci_find_slot(unsigned int bus, unsigned int devfn)
  * device structure is returned.  Otherwise, %NULL is returned.
  * A new search is initiated by passing %NULL to the @from argument.
  * Otherwise if @from is not %NULL, searches continue from next device on the global list.
+ *
+ * NOTE: Do not use this function anymore, use pci_get_subsys() instead, as
+ * the pci device returned by this function can disappear at any moment in
+ * time.
  */
 struct pci_dev *
 pci_find_subsys(unsigned int vendor, unsigned int device,
 		unsigned int ss_vendor, unsigned int ss_device,
 		const struct pci_dev *from)
 {
-	struct list_head *n = from ? from->global_list.next : pci_devices.next;
+	struct list_head *n;
+	struct pci_dev *dev;
+
+	WARN_ON(irqs_disabled());
+	spin_lock(&pci_bus_lock);
+	n = from ? from->global_list.next : pci_devices.next;
 
-	while (n != &pci_devices) {
-		struct pci_dev *dev = pci_dev_g(n);
+	while (n && (n != &pci_devices)) {
+		dev = pci_dev_g(n);
 		if ((vendor == PCI_ANY_ID || dev->vendor == vendor) &&
 		    (device == PCI_ANY_ID || dev->device == device) &&
 		    (ss_vendor == PCI_ANY_ID || dev->subsystem_vendor == ss_vendor) &&
 		    (ss_device == PCI_ANY_ID || dev->subsystem_device == ss_device))
-			return dev;
+			goto exit;
 		n = n->next;
 	}
-	return NULL;
+	dev = NULL;
+exit:
+	spin_unlock(&pci_bus_lock);
+	return dev;
 }
 
 /**
@@ -128,6 +155,10 @@ pci_find_subsys(unsigned int vendor, unsigned int device,
  * returned.  Otherwise, %NULL is returned.
  * A new search is initiated by passing %NULL to the @from argument.
  * Otherwise if @from is not %NULL, searches continue from next device on the global list.
+ * 
+ * NOTE: Do not use this function anymore, use pci_get_device() instead, as
+ * the pci device returned by this function can disappear at any moment in
+ * time.
  */
 struct pci_dev *
 pci_find_device(unsigned int vendor, unsigned int device, const struct pci_dev *from)
@@ -135,6 +166,77 @@ pci_find_device(unsigned int vendor, unsigned int device, const struct pci_dev *
 	return pci_find_subsys(vendor, device, PCI_ANY_ID, PCI_ANY_ID, from);
 }
 
+/**
+ * pci_get_subsys - begin or continue searching for a PCI device by vendor/subvendor/device/subdevice id
+ * @vendor: PCI vendor id to match, or %PCI_ANY_ID to match all vendor ids
+ * @device: PCI device id to match, or %PCI_ANY_ID to match all device ids
+ * @ss_vendor: PCI subsystem vendor id to match, or %PCI_ANY_ID to match all vendor ids
+ * @ss_device: PCI subsystem device id to match, or %PCI_ANY_ID to match all device ids
+ * @from: Previous PCI device found in search, or %NULL for new search.
+ *
+ * Iterates through the list of known PCI devices.  If a PCI device is
+ * found with a matching @vendor, @device, @ss_vendor and @ss_device, a pointer to its
+ * device structure is returned, and the reference count to the device is
+ * incremented.  Otherwise, %NULL is returned.  A new search is initiated by
+ * passing %NULL to the @from argument.  Otherwise if @from is not %NULL,
+ * searches continue from next device on the global list.
+ * The reference count for @from is always decremented if it is not %NULL.
+ */
+struct pci_dev * 
+pci_get_subsys(unsigned int vendor, unsigned int device,
+	       unsigned int ss_vendor, unsigned int ss_device,
+	       struct pci_dev *from)
+{
+	struct list_head *n;
+	struct pci_dev *dev;
+
+	WARN_ON(irqs_disabled());
+	spin_lock(&pci_bus_lock);
+	n = from ? from->global_list.next : pci_devices.next;
+
+	while (n && (n != &pci_devices)) {
+		dev = pci_dev_g(n);
+		if ((vendor == PCI_ANY_ID || dev->vendor == vendor) &&
+		    (device == PCI_ANY_ID || dev->device == device) &&
+		    (ss_vendor == PCI_ANY_ID || dev->subsystem_vendor == ss_vendor) &&
+		    (ss_device == PCI_ANY_ID || dev->subsystem_device == ss_device))
+			goto exit;
+		n = n->next;
+	}
+	dev = NULL;
+exit:
+	pci_put_dev(from);
+	dev = pci_get_dev(dev);
+	spin_unlock(&pci_bus_lock);
+	return dev;
+}
+
+/**
+ * pci_get_device - begin or continue searching for a PCI device by vendor/device id
+ * @vendor: PCI vendor id to match, or %PCI_ANY_ID to match all vendor ids
+ * @device: PCI device id to match, or %PCI_ANY_ID to match all device ids
+ * @from: Previous PCI device found in search, or %NULL for new search.
+ *
+ * Iterates through the list of known PCI devices.  If a PCI device is
+ * found with a matching @vendor and @device, a pointer to its device structure is
+ * returned.  Otherwise, %NULL is returned.
+ * A new search is initiated by passing %NULL to the @from argument.
+ * Otherwise if @from is not %NULL, searches continue from next device on the global list.
+ *
+ * Iterates through the list of known PCI devices.  If a PCI device is
+ * found with a matching @vendor and @device, the reference count to the
+ * device is incremented and a pointer to its device structure is returned.
+ * Otherwise, %NULL is returned.  A new search is initiated by passing %NULL
+ * to the @from argument.  Otherwise if @from is not %NULL, searches continue
+ * from next device on the global list.  The reference count for @from is
+ * always decremented if it is not %NULL.
+ */
+struct pci_dev *
+pci_get_device(unsigned int vendor, unsigned int device, struct pci_dev *from)
+{
+	return pci_get_subsys(vendor, device, PCI_ANY_ID, PCI_ANY_ID, from);
+}
+
 
 /**
  * pci_find_device_reverse - begin or continue searching for a PCI device by vendor/device id
@@ -151,16 +253,24 @@ pci_find_device(unsigned int vendor, unsigned int device, const struct pci_dev *
 struct pci_dev *
 pci_find_device_reverse(unsigned int vendor, unsigned int device, const struct pci_dev *from)
 {
-	struct list_head *n = from ? from->global_list.prev : pci_devices.prev;
+	struct list_head *n;
+	struct pci_dev *dev;
 
-	while (n != &pci_devices) {
-		struct pci_dev *dev = pci_dev_g(n);
+	WARN_ON(irqs_disabled());
+	spin_lock(&pci_bus_lock);
+	n = from ? from->global_list.prev : pci_devices.prev;
+
+	while (n && (n != &pci_devices)) {
+		dev = pci_dev_g(n);
 		if ((vendor == PCI_ANY_ID || dev->vendor == vendor) &&
 		    (device == PCI_ANY_ID || dev->device == device))
-			return dev;
+			goto exit;
 		n = n->prev;
 	}
-	return NULL;
+	dev = NULL;
+exit:
+	spin_unlock(&pci_bus_lock);
+	return dev;
 }
 
 
@@ -179,15 +289,22 @@ pci_find_device_reverse(unsigned int vendor, unsigned int device, const struct p
 struct pci_dev *
 pci_find_class(unsigned int class, const struct pci_dev *from)
 {
-	struct list_head *n = from ? from->global_list.next : pci_devices.next;
+	struct list_head *n;
+	struct pci_dev *dev;
 
-	while (n != &pci_devices) {
-		struct pci_dev *dev = pci_dev_g(n);
+	spin_lock(&pci_bus_lock);
+	n = from ? from->global_list.next : pci_devices.next;
+
+	while (n && (n != &pci_devices)) {
+		dev = pci_dev_g(n);
 		if (dev->class == class)
-			return dev;
+			goto exit;
 		n = n->next;
 	}
-	return NULL;
+	dev = NULL;
+exit:
+	spin_unlock(&pci_bus_lock);
+	return dev;
 }
 
 EXPORT_SYMBOL(pci_find_bus);
@@ -196,3 +313,5 @@ EXPORT_SYMBOL(pci_find_device);
 EXPORT_SYMBOL(pci_find_device_reverse);
 EXPORT_SYMBOL(pci_find_slot);
 EXPORT_SYMBOL(pci_find_subsys);
+EXPORT_SYMBOL(pci_get_device);
+EXPORT_SYMBOL(pci_get_subsys);

include/linux/pci.h

@@ -566,6 +566,10 @@ struct pci_dev *pci_find_slot (unsigned int bus, unsigned int devfn);
 int pci_find_capability (struct pci_dev *dev, int cap);
 struct pci_bus * pci_find_next_bus(const struct pci_bus *from);
 
+struct pci_dev *pci_get_device (unsigned int vendor, unsigned int device, struct pci_dev *from);
+struct pci_dev *pci_get_subsys (unsigned int vendor, unsigned int device,
+				unsigned int ss_vendor, unsigned int ss_device,
+				struct pci_dev *from);
 int pci_bus_read_config_byte (struct pci_bus *bus, unsigned int devfn, int where, u8 *val);
 int pci_bus_read_config_word (struct pci_bus *bus, unsigned int devfn, int where, u16 *val);
 int pci_bus_read_config_dword (struct pci_bus *bus, unsigned int devfn, int where, u32 *val);
@@ -688,6 +692,13 @@ static inline struct pci_dev *pci_find_subsys(unsigned int vendor, unsigned int
 unsigned int ss_vendor, unsigned int ss_device, const struct pci_dev *from)
 { return NULL; }
 
+static inline struct pci_dev *pci_get_device (unsigned int vendor, unsigned int device, struct pci_dev *from)
+{ return NULL; }
+
+static inline struct pci_dev *pci_get_subsys (unsigned int vendor, unsigned int device,
+unsigned int ss_vendor, unsigned int ss_device, struct pci_dev *from)
+{ return NULL; }
+
 static inline void pci_set_master(struct pci_dev *dev) { }
 static inline int pci_enable_device(struct pci_dev *dev) { return -EIO; }
 static inline void pci_disable_device(struct pci_dev *dev) { }