USB: remove use of the bus rwsem, as it doesn't really protect anything.

The driver core stopped using the rwsem a long time ago, yet the USB
core still grabbed the lock, thinking it protected something.  This
patch removes that useless use.

Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Oliver Neukum <oneukum@suse.de>
Cc: David Brownell <david-b@pacbell.net>
Cc: linux-usb-devel <linux-usb-devel@lists.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

4 files changed, 7 insertions, 22 deletions

diff --git a/drivers/usb/core/devices.c b/drivers/usb/core/devices.c
index aefc7987120d..6753ca059ee4 100644
--- a/drivers/usb/core/devices.c
+++ b/drivers/usb/core/devices.c
@@ -246,7 +246,6 @@ static char *usb_dump_interface_descriptor(char *start, char *end,
 
         if (start > end)
                 return start;
-        down_read(&usb_bus_type.subsys.rwsem);
         if (iface) {
                 driver_name = (iface->dev.driver
                                 ? iface->dev.driver->name
@@ -263,7 +262,6 @@ static char *usb_dump_interface_descriptor(char *start, char *end,
                          desc->bInterfaceSubClass,
                          desc->bInterfaceProtocol,
                          driver_name);
-        up_read(&usb_bus_type.subsys.rwsem);
         return start;
 }
 
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 36e7a843bf91..fc3545ddb06e 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -421,14 +421,11 @@ static int claimintf(struct dev_state *ps, unsigned int ifnum)
         if (test_bit(ifnum, &ps->ifclaimed))
                 return 0;
 
-        /* lock against other changes to driver bindings */
-        down_write(&usb_bus_type.subsys.rwsem);
         intf = usb_ifnum_to_if(dev, ifnum);
         if (!intf)
                 err = -ENOENT;
         else
                 err = usb_driver_claim_interface(&usbfs_driver, intf, ps);
-        up_write(&usb_bus_type.subsys.rwsem);
         if (err == 0)
                 set_bit(ifnum, &ps->ifclaimed);
         return err;
@@ -444,8 +441,6 @@ static int releaseintf(struct dev_state *ps, unsigned int ifnum)
         if (ifnum >= 8*sizeof(ps->ifclaimed))
                 return err;
         dev = ps->dev;
-        /* lock against other changes to driver bindings */
-        down_write(&usb_bus_type.subsys.rwsem);
         intf = usb_ifnum_to_if(dev, ifnum);
         if (!intf)
                 err = -ENOENT;
@@ -453,7 +448,6 @@ static int releaseintf(struct dev_state *ps, unsigned int ifnum)
                 usb_driver_release_interface(&usbfs_driver, intf);
                 err = 0;
         }
-        up_write(&usb_bus_type.subsys.rwsem);
         return err;
 }
 
@@ -813,7 +807,6 @@ static int proc_getdriver(struct dev_state *ps, void __user *arg)
 
         if (copy_from_user(&gd, arg, sizeof(gd)))
                 return -EFAULT;
-        down_read(&usb_bus_type.subsys.rwsem);
         intf = usb_ifnum_to_if(ps->dev, gd.interface);
         if (!intf || !intf->dev.driver)
                 ret = -ENODATA;
@@ -822,7 +815,6 @@ static int proc_getdriver(struct dev_state *ps, void __user *arg)
                                 sizeof(gd.driver));
                 ret = (copy_to_user(arg, &gd, sizeof(gd)) ? -EFAULT : 0);
         }
-        up_read(&usb_bus_type.subsys.rwsem);
         return ret;
 }
 
@@ -1351,15 +1343,12 @@ static int proc_ioctl(struct dev_state *ps, struct usbdevfs_ioctl *ctl)
 
         /* disconnect kernel driver from interface */
         case USBDEVFS_DISCONNECT:
-
-                down_write(&usb_bus_type.subsys.rwsem);
                 if (intf->dev.driver) {
                         driver = to_usb_driver(intf->dev.driver);
                         dev_dbg (&intf->dev, "disconnect by usbfs\n");
                         usb_driver_release_interface(driver, intf);
                 } else
                         retval = -ENODATA;
-                up_write(&usb_bus_type.subsys.rwsem);
                 break;
 
         /* let kernel drivers try to (re)bind to the interface */
@@ -1371,7 +1360,6 @@ static int proc_ioctl(struct dev_state *ps, struct usbdevfs_ioctl *ctl)
 
         /* talk directly to the interface's driver */
         default:
-                down_read(&usb_bus_type.subsys.rwsem);
                 if (intf->dev.driver)
                         driver = to_usb_driver(intf->dev.driver);
                 if (driver == NULL || driver->ioctl == NULL) {
@@ -1381,7 +1369,6 @@ static int proc_ioctl(struct dev_state *ps, struct usbdevfs_ioctl *ctl)
                         if (retval == -ENOIOCTLCMD)
                                 retval = -ENOTTY;
                 }
-                up_read(&usb_bus_type.subsys.rwsem);
         }
 
         /* cleanup and return */
diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 9e3e943f313c..e6dd2b9210f6 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -287,9 +287,9 @@ static int usb_unbind_interface(struct device *dev)
  * way to bind to an interface is to return the private data from
  * the driver's probe() method.
  *
- * Callers must own the device lock and the driver model's usb_bus_type.subsys
- * writelock.  So driver probe() entries don't need extra locking,
- * but other call contexts may need to explicitly claim those locks.
+ * Callers must own the device lock, so driver probe() entries don't need
+ * extra locking, but other call contexts may need to explicitly claim that
+ * lock.
  */
 int usb_driver_claim_interface(struct usb_driver *driver,
                                 struct usb_interface *iface, void* priv)
@@ -330,9 +330,9 @@ EXPORT_SYMBOL(usb_driver_claim_interface);
  * also causes the driver disconnect() method to be called.
  *
  * This call is synchronous, and may not be used in an interrupt context.
- * Callers must own the device lock and the driver model's usb_bus_type.subsys
- * writelock.  So driver disconnect() entries don't need extra locking,
- * but other call contexts may need to explicitly claim those locks.
+ * Callers must own the device lock, so driver disconnect() entries don't
+ * need extra locking, but other call contexts may need to explicitly claim
+ * that lock.
  */
 void usb_driver_release_interface(struct usb_driver *driver,
                                         struct usb_interface *iface)
diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index 217a3d6d0a06..c359ccb32998 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -1349,7 +1349,7 @@ static void release_interface(struct device *dev)
  *
  * This call is synchronous. The calling context must be able to sleep,
  * must own the device lock, and must not hold the driver model's USB
- * bus rwsem; usb device driver probe() methods cannot use this routine.
+ * bus mutex; usb device driver probe() methods cannot use this routine.
  *
  * Returns zero on success, or else the status code returned by the
  * underlying call that failed.  On successful completion, each interface