[PATCH 22/46] USB: remove use of the bus rwsem, as it doesn't really protect anything.

Greg Kroah-Hartman
2007-04-27T18:57:43Z

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>
---
drivers/usb/core/devices.c | 2 --
drivers/usb/core/devio.c | 13 -------------
drivers/usb/core/driver.c | 12 ++++++------
drivers/usb/core/message.c | 2 +-
4 files changed, 7 insertions(+), 22 deletions(-)

diff --git a/drivers/usb/core/devices.c b/drivers/usb/core/devices.c
index aefc798..6753ca0 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 36e7a84..fc3545d 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 9e3e943..e6dd2b9 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 217a3d6..c359ccb 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
--
1.5.1.2