[PATCH] USB: Remove USB private semaphore

This patch (as605) removes the private udev->serialize semaphore,
relying instead on the locking provided by the embedded struct device's
semaphore.  The changes are confined to the core, except that the
usb_trylock_device routine now uses the return convention of
down_trylock rather than down_read_trylock (they return opposite values
for no good reason).

A couple of other associated changes are included as well:

	Now that we aren't concerned about HCDs that avoid using the
	hcd glue layer, usb_disconnect no longer needs to acquire the
	usb_bus_lock -- that can be done by usb_remove_hcd where it
	belongs.

	Devices aren't locked over the same scope of code in
	usb_new_device and hub_port_connect_change as they used to be.
	This shouldn't cause any trouble.

Along with the preceding driver core patch, this needs a lot of testing.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/devices.c

@@ -545,10 +545,10 @@ static ssize_t usb_device_dump(char __user **buffer, size_t *nbytes, loff_t *ski
 		struct usb_device *childdev = usbdev->children[chix];
 
 		if (childdev) {
-			down(&childdev->serialize);
+			usb_lock_device(childdev);
 			ret = usb_device_dump(buffer, nbytes, skip_bytes, file_offset, childdev,
 					bus, level + 1, chix, ++cnt);
-			up(&childdev->serialize);
+			usb_unlock_device(childdev);
 			if (ret == -EFAULT)
 				return total_written;
 			total_written += ret;

drivers/usb/core/devio.c

@@ -1349,9 +1349,7 @@ static int proc_ioctl(struct dev_state *ps, struct usbdevfs_ioctl *ctl)
 	/* let kernel drivers try to (re)bind to the interface */
 	case USBDEVFS_CONNECT:
 		usb_unlock_device(ps->dev);
-		usb_lock_all_devices();
 		bus_rescan_devices(intf->dev.bus);
-		usb_unlock_all_devices();
 		usb_lock_device(ps->dev);
 		break;
 

drivers/usb/core/driver.c

@@ -432,9 +432,7 @@ int usb_register_driver(struct usb_driver *new_driver, struct module *owner)
 	spin_lock_init(&new_driver->dynids.lock);
 	INIT_LIST_HEAD(&new_driver->dynids.list);
 
-	usb_lock_all_devices();
 	retval = driver_register(&new_driver->driver);
-	usb_unlock_all_devices();
 
 	if (!retval) {
 		pr_info("%s: registered new driver %s\n",
@@ -465,11 +463,9 @@ void usb_deregister(struct usb_driver *driver)
 {
 	pr_info("%s: deregistering driver %s\n", usbcore_name, driver->name);
 
-	usb_lock_all_devices();
 	usb_remove_newid_file(driver);
 	usb_free_dynids(driver);
 	driver_unregister(&driver->driver);
-	usb_unlock_all_devices();
 
 	usbfs_update_special();
 }

drivers/usb/core/hcd.c

@@ -857,9 +857,7 @@ static int register_root_hub (struct usb_device *usb_dev,
 		return (retval < 0) ? retval : -EMSGSIZE;
 	}
 
-	usb_lock_device (usb_dev);
 	retval = usb_new_device (usb_dev);
-	usb_unlock_device (usb_dev);
 	if (retval) {
 		usb_dev->bus->root_hub = NULL;
 		dev_err (parent_dev, "can't register root hub for %s, %d\n",
@@ -1891,7 +1889,10 @@ void usb_remove_hcd(struct usb_hcd *hcd)
 	spin_lock_irq (&hcd_root_hub_lock);
 	hcd->rh_registered = 0;
 	spin_unlock_irq (&hcd_root_hub_lock);
+
+	down(&usb_bus_list_lock);
 	usb_disconnect(&hcd->self.root_hub);
+	up(&usb_bus_list_lock);
 
 	hcd->poll_rh = 0;
 	del_timer_sync(&hcd->rh_timer);

drivers/usb/core/hub.c

@@ -32,7 +32,7 @@
 #include "hub.h"
 
 /* Protect struct usb_device->state and ->children members
- * Note: Both are also protected by ->serialize, except that ->state can
+ * Note: Both are also protected by ->dev.sem, except that ->state can
  * change to USB_STATE_NOTATTACHED even when the semaphore isn't held. */
 static DEFINE_SPINLOCK(device_state_lock);
 
@@ -975,8 +975,8 @@ static int locktree(struct usb_device *udev)
 			/* when everyone grabs locks top->bottom,
 			 * non-overlapping work may be concurrent
 			 */
-			down(&udev->serialize);
-			up(&hdev->serialize);
+			usb_lock_device(udev);
+			usb_unlock_device(hdev);
 			return t + 1;
 		}
 	}
@@ -1132,16 +1132,10 @@ void usb_disconnect(struct usb_device **pdev)
 	 * this quiesces everyting except pending urbs.
 	 */
 	usb_set_device_state(udev, USB_STATE_NOTATTACHED);
-
-	/* lock the bus list on behalf of HCDs unregistering their root hubs */
-	if (!udev->parent) {
-		down(&usb_bus_list_lock);
-		usb_lock_device(udev);
-	} else
-		down(&udev->serialize);
-
 	dev_info (&udev->dev, "USB disconnect, address %d\n", udev->devnum);
 
+	usb_lock_device(udev);
+
 	/* Free up all the children before we remove this device */
 	for (i = 0; i < USB_MAXCHILDREN; i++) {
 		if (udev->children[i])
@@ -1169,11 +1163,7 @@ void usb_disconnect(struct usb_device **pdev)
 	*pdev = NULL;
 	spin_unlock_irq(&device_state_lock);
 
-	if (!udev->parent) {
-		usb_unlock_device(udev);
-		up(&usb_bus_list_lock);
-	} else
-		up(&udev->serialize);
+	usb_unlock_device(udev);
 
 	device_unregister(&udev->dev);
 }
@@ -1243,8 +1233,8 @@ static inline void show_string(struct usb_device *udev, char *id, char *string)
  *
  * This is called with devices which have been enumerated, but not yet
  * configured.  The device descriptor is available, but not descriptors
- * for any device configuration.  The caller must have locked udev and
- * either the parent hub (if udev is a normal device) or else the
+ * for any device configuration.  The caller must have locked either
+ * the parent hub (if udev is a normal device) or else the
  * usb_bus_list_lock (if udev is a root hub).  The parent's pointer to
  * udev has already been installed, but udev is not yet visible through
  * sysfs or other filesystem code.
@@ -1254,8 +1244,7 @@ static inline void show_string(struct usb_device *udev, char *id, char *string)
  *
  * This call is synchronous, and may not be used in an interrupt context.
  *
- * Only the hub driver should ever call this; root hub registration
- * uses it indirectly.
+ * Only the hub driver or root-hub registrar should ever call this.
  */
 int usb_new_device(struct usb_device *udev)
 {
@@ -1364,6 +1353,8 @@ int usb_new_device(struct usb_device *udev)
 	}
 	usb_create_sysfs_dev_files (udev);
 
+	usb_lock_device(udev);
+
 	/* choose and set the configuration. that registers the interfaces
 	 * with the driver core, and lets usb device drivers bind to them.
 	 */
@@ -1385,6 +1376,8 @@ int usb_new_device(struct usb_device *udev)
 	/* USB device state == configured ... usable */
 	usb_notify_add_device(udev);
 
+	usb_unlock_device(udev);
+
 	return 0;
 
 fail:
@@ -1872,11 +1865,8 @@ int usb_resume_device(struct usb_device *udev)
 	usb_unlock_device(udev);
 
 	/* rebind drivers that had no suspend() */
-	if (status == 0) {
-		usb_lock_all_devices();
+	if (status == 0)
 		bus_rescan_devices(&usb_bus_type);
-		usb_unlock_all_devices();
-	}
 	return status;
 }
 
@@ -1889,14 +1879,14 @@ static int remote_wakeup(struct usb_device *udev)
 	/* don't repeat RESUME sequence if this device
 	 * was already woken up by some other task
 	 */
-	down(&udev->serialize);
+	usb_lock_device(udev);
 	if (udev->state == USB_STATE_SUSPENDED) {
 		dev_dbg(&udev->dev, "RESUME (wakeup)\n");
 		/* TRSMRCY = 10 msec */
 		msleep(10);
 		status = finish_device_resume(udev);
 	}
-	up(&udev->serialize);
+	usb_unlock_device(udev);
 #endif
 	return status;
 }
@@ -1997,7 +1987,7 @@ static int hub_resume(struct usb_interface *intf)
 
 		if (!udev || status < 0)
 			continue;
-		down (&udev->serialize);
+		usb_lock_device(udev);
 		if (portstat & USB_PORT_STAT_SUSPEND)
 			status = hub_port_resume(hub, port1, udev);
 		else {
@@ -2008,7 +1998,7 @@ static int hub_resume(struct usb_interface *intf)
 				hub_port_logical_disconnect(hub, port1);
 			}
 		}
-		up(&udev->serialize);
+		usb_unlock_device(udev);
 	}
 	}
 #endif
@@ -2573,7 +2563,6 @@ static void hub_port_connect_change(struct usb_hub *hub, int port1,
 		 * udev becomes globally accessible, although presumably
 		 * no one will look at it until hdev is unlocked.
 		 */
-		down (&udev->serialize);
 		status = 0;
 
 		/* We mustn't add new devices if the parent hub has
@@ -2597,7 +2586,6 @@ static void hub_port_connect_change(struct usb_hub *hub, int port1,
 			}
 		}
 
-		up (&udev->serialize);
 		if (status)
 			goto loop_disable;