USB: change locking for device-level autosuspend
This patch (as1323) changes the locking requirements for
usb_autosuspend_device(), usb_autoresume_device(), and
usb_try_autosuspend_device(). This isn't a very important change;
mainly it's meant to make the locking more uniform.
The most tricky part of the patch involves changes to usbdev_open().
To avoid an ABBA locking problem, it was necessary to reduce the
region protected by usbfs_mutex. Since that mutex now protects only
against simultaneous open and remove, this posed no difficulty -- its
scope was larger than necessary.
And it turns out that usbfs_mutex is no longer needed in
usbdev_release() at all. The list of usbfs "ps" structures is now
protected by the device lock instead of by usbfs_mutex.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index fcafb2d..2b39583 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1478,8 +1478,7 @@
* driver requires remote-wakeup capability during autosuspend but remote
* wakeup is disabled, the autosuspend will fail.
*
- * Often the caller will hold @udev's device lock, but this is not
- * necessary.
+ * The caller must hold @udev's device lock.
*
* This routine can run only in process context.
*/
@@ -1503,6 +1502,8 @@
* for an active interface is greater than 0, or autosuspend is not allowed
* for any other reason, no autosuspend request will be queued.
*
+ * The caller must hold @udev's device lock.
+ *
* This routine can run only in process context.
*/
void usb_try_autosuspend_device(struct usb_device *udev)
@@ -1526,8 +1527,7 @@
* @udev's usage counter is incremented to prevent subsequent autosuspends.
* However if the autoresume fails then the usage counter is re-decremented.
*
- * Often the caller will hold @udev's device lock, but this is not
- * necessary (and attempting it might cause deadlock).
+ * The caller must hold @udev's device lock.
*
* This routine can run only in process context.
*/
