[PATCH] USB: Dequeuing of root-hub URBs

This patch fixes a tiny SMP-type hole in root-hub synchronization.
Although the HCD glue layer properly unlinks root-hub status URBs
synchronously, it doesn't do so for URBs sent to endpoint 0.  This patch
copies some code from usb_kill_urb, to make such unlinks wait until the
host controller driver has finished handling the URB.  This behavior is
required for hcd_endpoint_disable to work correctly.

The patch also renames usb_rh_status_dequeue to usb_rh_urb_dequeue (to
better describe its updated function) and declares the routine static.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/usb/core/hcd.c

@@ -568,11 +568,12 @@ static int rh_urb_enqueue (struct usb_hcd *hcd, struct urb *urb)
 
 /*-------------------------------------------------------------------------*/
 
-int usb_rh_status_dequeue (struct usb_hcd *hcd, struct urb *urb)
+static int usb_rh_urb_dequeue (struct usb_hcd *hcd, struct urb *urb)
 {
 	unsigned long	flags;
 
 	/* note:  always a synchronous unlink */
+	if ((unsigned long) urb == hcd->rh_timer.data) {
 		del_timer_sync (&hcd->rh_timer);
 		hcd->rh_timer.data = 0;
 
@@ -580,6 +581,21 @@ int usb_rh_status_dequeue (struct usb_hcd *hcd, struct urb *urb)
 		urb->hcpriv = NULL;
 		usb_hcd_giveback_urb (hcd, urb, NULL);
 		local_irq_restore (flags);
+
+	} else if (usb_pipeendpoint(urb->pipe) == 0) {
+		spin_lock_irq(&urb->lock);	/* from usb_kill_urb */
+		++urb->reject;
+		spin_unlock_irq(&urb->lock);
+
+		wait_event(usb_kill_urb_queue,
+				atomic_read(&urb->use_count) == 0);
+
+		spin_lock_irq(&urb->lock);
+		--urb->reject;
+		spin_unlock_irq(&urb->lock);
+	} else
+		return -EINVAL;
+
 	return 0;
 }
 
@@ -1171,8 +1187,8 @@ unlink1 (struct usb_hcd *hcd, struct urb *urb)
 {
 	int		value;
 
-	if (urb == (struct urb *) hcd->rh_timer.data)
-		value = usb_rh_status_dequeue (hcd, urb);
+	if (urb->dev == hcd->self.root_hub)
+		value = usb_rh_urb_dequeue (hcd, urb);
 	else {
 
 		/* The only reason an HCD might fail this call is if
@@ -1260,7 +1276,7 @@ static int hcd_unlink_urb (struct urb *urb, int status)
 	 * never get completion IRQs ... maybe even the ones we need to
 	 * finish unlinking the initial failed usb_set_address().
 	 */
-	if (!hcd->saw_irq && hcd->rh_timer.data != (unsigned long) urb) {
+	if (!hcd->saw_irq && hcd->self.root_hub != urb->dev) {
 		dev_warn (hcd->self.controller, "Unlink after no-IRQ?  "
 			"Different ACPI or APIC settings may help."
 			"\n");

drivers/usb/core/hcd.h

@@ -215,7 +215,6 @@ struct hc_driver {
 
 extern void usb_hcd_giveback_urb (struct usb_hcd *hcd, struct urb *urb, struct pt_regs *regs);
 extern void usb_bus_init (struct usb_bus *bus);
-extern int usb_rh_status_dequeue (struct usb_hcd *hcd, struct urb *urb);
 
 #ifdef CONFIG_PCI
 struct pci_dev;