On 09/20/2010 11:10 AM, Jiri Kosina wrote:
> Thanks Matt and Phill for confirming the line that triggers the oops. As I 
> am not able to reproduce it myself, it's a bit tricky to track down what 
> went wrong.
> 
> Could you please apply the patch below? It's printing the hid <-> hiddev 
> <-> usb_interface connections at various stages of probing and open. 
> Hopefully it'll reveal a little bit what goes wrong and where.
> 
> Thanks.
> 
> 
> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> index 3f72924..3159a63 100644
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -1155,6 +1155,8 @@ int hid_connect(struct hid_device *hdev, unsigned int connect_mask)
>  	unsigned int i;
>  	int len;
>  
> +	printk("HID debug: hid_connect() -- hid: %p\n", hdev);
> +
>  	if (hdev->quirks & HID_QUIRK_HIDDEV_FORCE)
>  		connect_mask |= (HID_CONNECT_HIDDEV_FORCE | HID_CONNECT_HIDDEV);
>  	if (hdev->quirks & HID_QUIRK_HIDINPUT_FORCE)
> @@ -1169,8 +1171,11 @@ int hid_connect(struct hid_device *hdev, unsigned int connect_mask)
>  		hdev->claimed |= HID_CLAIMED_INPUT;
>  	if ((connect_mask & HID_CONNECT_HIDDEV) && hdev->hiddev_connect &&
>  			!hdev->hiddev_connect(hdev,
> -				connect_mask & HID_CONNECT_HIDDEV_FORCE))
> +				connect_mask & HID_CONNECT_HIDDEV_FORCE)) {
>  		hdev->claimed |= HID_CLAIMED_HIDDEV;
> +		printk("HID debug: hid_connect() -- after hiddev_connect(), hid: %p, hiddev: %p\n",
> +				hdev, hdev->hiddev);
> +	}
>  	if ((connect_mask & HID_CONNECT_HIDRAW) && !hidraw_connect(hdev))
>  		hdev->claimed |= HID_CLAIMED_HIDRAW;
>  
> diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c
> index 599041a..d2491a1 100644
> --- a/drivers/hid/usbhid/hid-core.c
> +++ b/drivers/hid/usbhid/hid-core.c
> @@ -1148,6 +1148,7 @@ static int usbhid_probe(struct usb_interface *intf, const struct usb_device_id *
>  	if (IS_ERR(hid))
>  		return PTR_ERR(hid);
>  
> +	printk("HID debug: usbhid_probe() -- set intfdata(%p, %p)\n", intf, hid);
>  	usb_set_intfdata(intf, hid);
>  	hid->ll_driver = &usb_hid_driver;
>  	hid->hid_output_raw_report = usbhid_output_raw_report;
> diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
> index 681e620..9aab39a 100644
> --- a/drivers/hid/usbhid/hiddev.c
> +++ b/drivers/hid/usbhid/hiddev.c
> @@ -282,6 +282,8 @@ static int hiddev_open(struct inode *inode, struct file *file)
>  	list->hiddev = hiddev;
>  	file->private_data = list;
>  
> +	printk("HID debug: hiddev_open(): hid: %p, hiddev: %p, intf: %p\n",
> +			hid, hiddev, intf);
>  	/*
>  	 * no need for locking because the USB major number
>  	 * is shared which usbcore guards against disconnect
> @@ -892,6 +894,8 @@ int hiddev_connect(struct hid_device *hid, unsigned int force)
>  	hid->hiddev = hiddev;
>  	hiddev->hid = hid;
>  	hiddev->exist = 1;
> +	printk("HID debug: hiddev_connect() -- hid: %p, hiddev: %p, intf: %p\n",
> +			hid, hiddev, usbhid->intf);
>  	retval = usb_register_dev(usbhid->intf, &hiddev_class);
>  	if (retval) {
>  		err_hid("Not able to get a minor for this device.");
> @@ -912,6 +916,8 @@ void hiddev_disconnect(struct hid_device *hid)
>  	struct hiddev *hiddev = hid->hiddev;
>  	struct usbhid_device *usbhid = hid->driver_data;
>  
> +	printk("HID debug: hiddev_disconnect() -- hid: %p, usbhid: %p, hiddev: %p\n",
> +			hid, usbhid, hiddev);
>  	mutex_lock(&hiddev->existancelock);
>  	hiddev->exist = 0;
>  	mutex_unlock(&hiddev->existancelock);
> 

dmesg attached.  Note: the timestamp of the BUG corresponds to hal startup when the external mouse is plugged in before booting.