USB: xhci: Use GFP_ATOMIC while holding spinlocks.

The xHCI functions to queue an URB onto the hardware rings must be called
with the xhci spinlock held.  Those functions will allocate memory, and
take a gfp_t memory flags argument.  We must pass them the GFP_ATOMIC
flag, since we don't want the memory allocation to attempt to sleep while
waiting for more memory to become available.
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/xhci-hcd.c

@@ -601,10 +601,13 @@ int xhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flags)
 		goto exit;
 	}
 	if (usb_endpoint_xfer_control(&urb->ep->desc))
-		ret = xhci_queue_ctrl_tx(xhci, mem_flags, urb,
+		/* We have a spinlock and interrupts disabled, so we must pass
+		 * atomic context to this function, which may allocate memory.
+		 */
+		ret = xhci_queue_ctrl_tx(xhci, GFP_ATOMIC, urb,
 				slot_id, ep_index);
 	else if (usb_endpoint_xfer_bulk(&urb->ep->desc))
-		ret = xhci_queue_bulk_tx(xhci, mem_flags, urb,
+		ret = xhci_queue_bulk_tx(xhci, GFP_ATOMIC, urb,
 				slot_id, ep_index);
 	else
 		ret = -EINVAL;