usbcore: khubd and busy-port handling

We don't want khubd to start interfering in the device-resume process
merely because the PORT_STATUS_C_SUSPEND feature happens to be set.
Ports need to be marked as busy while a resume is taking place.

In addition, so long as ports are marked as busy, khubd won't be able to
clear their various status-change features.  On an interrupt-driven root
hub this could lead to an interrupt storm.  Root hub IRQs should not be
re-enabled until the busy_bits value is equal to 0.

This patch (as765) fixes these two potential problems.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/hub.c

@@ -1658,6 +1658,8 @@ hub_port_resume(struct usb_hub *hub, int port1, struct usb_device *udev)
 
 	// dev_dbg(hub->intfdev, "resume port %d\n", port1);
 
+	set_bit(port1, hub->busy_bits);
+
 	/* see 7.1.7.7; affects power usage, but not budgeting */
 	status = clear_port_feature(hub->hdev,
 			port1, USB_PORT_FEAT_SUSPEND);
@@ -1707,6 +1709,10 @@ hub_port_resume(struct usb_hub *hub, int port1, struct usb_device *udev)
 	if (status < 0)
 		hub_port_logical_disconnect(hub, port1);
 
+	clear_bit(port1, hub->busy_bits);
+	if (!hub->hdev->parent && !hub->busy_bits[0])
+		usb_enable_root_hub_irq(hub->hdev->bus);
+
 	return status;
 }
 
@@ -2690,7 +2696,7 @@ static void hub_events(void)
 
 		/* If this is a root hub, tell the HCD it's okay to
 		 * re-enable port-change interrupts now. */
-		if (!hdev->parent)
+		if (!hdev->parent && !hub->busy_bits[0])
 			usb_enable_root_hub_irq(hdev->bus);
 
 loop:
@@ -2865,6 +2871,9 @@ int usb_reset_device(struct usb_device *udev)
 			break;
 	}
 	clear_bit(port1, parent_hub->busy_bits);
+	if (!parent_hdev->parent && !parent_hub->busy_bits[0])
+		usb_enable_root_hub_irq(parent_hdev->bus);
+
 	if (ret < 0)
 		goto re_enumerate;
  

drivers/usb/core/hub.h

@@ -212,7 +212,8 @@ struct usb_hub {
 	unsigned long		event_bits[1];	/* status change bitmask */
 	unsigned long		change_bits[1];	/* ports with logical connect
 							status change */
-	unsigned long		busy_bits[1];	/* ports being reset */
+	unsigned long		busy_bits[1];	/* ports being reset or
+							resumed */
 #if USB_MAXCHILDREN > 31 /* 8*sizeof(unsigned long) - 1 */
 #error event_bits[] is too short!
 #endif