Re: Null Pointer BUG in uhci_hcd

Michael S. Zick
2009-07-08T16:38:54Z

On Wed July 8 2009, Michael S. Zick wrote:
> On Wed July 8 2009, Michael S. Zick wrote:
> > On Tue July 7 2009, Alan Stern wrote:
> > > On Tue, 7 Jul 2009, Michael S. Zick wrote:
> > >
> > > > On Tue July 7 2009, Alan Stern wrote:
> > > > > On Tue, 7 Jul 2009, Michael S. Zick wrote:
> > > > >
> > > > > > > It looks like there's a serious problem in your UHCI hardware.
> > > > > > > According to the log you posted, it's not working at all.
> > > > > > >
> > > > > >
> > > > > > I am using the x86-generic drivers - -
> > > > >
> > > > > Not a problem with the drivers, a problem in the hardware.
> > > > >
> > > >
> > > > Or hardware that works as the manufacturer intended, but differently
> > > > than expected. Same difference as "broken" when compared to "standard".
> > >
> > > No, hardware that doesn't work at all. As in "all reads return
> > > 0xffffffff" -- that's just a guess but something like it would account
> > > for what you saw.
> > >

I tried to combine the addition of the diagnostic print (BUG())
statements and the potential fix - -
This is what I put into the code for today's testing:

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index be86ae3..d686f1d 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -160,8 +160,10 @@ static inline char *portspeed(int portstatus)
}

/* Note that hdev or one of its children must be locked! */
-static inline struct usb_hub *hdev_to_hub(struct usb_device *hdev)
+static struct usb_hub *hdev_to_hub(struct usb_device *hdev)
{
+ if (!hdev || !hdev->actconfig)
+ return NULL;
return usb_get_intfdata(hdev->actconfig->interface[0]);
}

@@ -369,11 +371,16 @@ static void kick_khubd(struct usb_hub *hub)
{
unsigned long flags;

- /* Suppress autosuspend until khubd runs */
- to_usb_interface(hub->intfdev)->pm_usage_cnt = 1;
+ if (!hub) {
+ BUG();
+ return;
+ }

spin_lock_irqsave(&hub_event_lock, flags);
if (!hub->disconnected && list_empty(&hub->event_list)) {
+ /* Suppress autosuspend until khubd runs */
+ to_usb_interface(hub->intfdev)->pm_usage_cnt = 1;
+
list_add_tail(&hub->event_list, &hub_event_list);
wake_up(&khubd_wait);
}
@@ -382,8 +389,19 @@ static void kick_khubd(struct usb_hub *hub)

void usb_kick_khubd(struct usb_device *hdev)
{
- /* FIXME: What if hdev isn't bound to the hub driver? */
- kick_khubd(hdev_to_hub(hdev));
+ struct usb_hub *hub;
+
+ if (!hdev) {
+ BUG();
+ return;
+ }
+ hub = hdev_to_hub(hdev);
+ if (hub) {
+ kick_khubd(hub);
+ } else {
+ BUG();
+ return;
+ }
}

Mike