drivers: usb: core: Minimize irq disabling in usb_sg_cancel()

Restructure usb_sg_cancel() so we don't have to disable interrupts
while cancelling the URBs.

Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: David Mosberger <davidm@egauge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/message.c

@@ -577,31 +577,28 @@ EXPORT_SYMBOL_GPL(usb_sg_wait);
 void usb_sg_cancel(struct usb_sg_request *io)
 {
 	unsigned long flags;
+	int i, retval;
 
 	spin_lock_irqsave(&io->lock, flags);
-
-	/* shut everything down, if it didn't already */
-	if (!io->status) {
-		int i;
-
-		io->status = -ECONNRESET;
-		spin_unlock(&io->lock);
-		for (i = 0; i < io->entries; i++) {
-			int retval;
-
-			usb_block_urb(io->urbs[i]);
-
-			retval = usb_unlink_urb(io->urbs[i]);
-			if (retval != -EINPROGRESS
-					&& retval != -ENODEV
-					&& retval != -EBUSY
-					&& retval != -EIDRM)
-				dev_warn(&io->dev->dev, "%s, unlink --> %d\n",
-					__func__, retval);
-		}
-		spin_lock(&io->lock);
+	if (io->status) {
+		spin_unlock_irqrestore(&io->lock, flags);
+		return;
 	}
+	/* shut everything down */
+	io->status = -ECONNRESET;
 	spin_unlock_irqrestore(&io->lock, flags);
+
+	for (i = io->entries - 1; i >= 0; --i) {
+		usb_block_urb(io->urbs[i]);
+
+		retval = usb_unlink_urb(io->urbs[i]);
+		if (retval != -EINPROGRESS
+		    && retval != -ENODEV
+		    && retval != -EBUSY
+		    && retval != -EIDRM)
+			dev_warn(&io->dev->dev, "%s, unlink --> %d\n",
+				 __func__, retval);
+	}
 }
 EXPORT_SYMBOL_GPL(usb_sg_cancel);