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>

2 files changed, 12 insertions, 2 deletions

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 3924dd080be..bdf5be09965 100644
--- a/drivers/usb/core/hub.c
+++ b/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;
  
diff --git a/drivers/usb/core/hub.h b/drivers/usb/core/hub.h
index 29d5f45a845..0f8e82a4d48 100644
--- a/drivers/usb/core/hub.h
+++ b/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