hi Alan:
>
> I originally tried using usb_reset_device, and it caused a deadlock:
>
> Unplug the HID device.
>
> I/O error occurs. hid_io_error schedules reset_work.
>
> The reset_work callback routine is hid_reset. It calls
> usb_reset_device.
>
> The reset fails because the device is gone. At the end of the
> reset, hid_post_reset is called.
>
> hid_post_reset returns 1 because hid_get_class_descriptor
> fails.
>
> Because the post_reset routine failed, usb_reset_device calls
> usb_unbind_and_rebind_marked_interfaces.
"usb_unbind_and_rebind_marked_interfaces" is called if config
parameter is not null,
it seems no matter post_reset routine fail or not.
>
> That routine indirectly calls usbhid_disconnect.
Why that routine, usb_reset_device, will call usbhid_disconnect?
No matter port reset success or fail, usbhid_disconnect should not be
called except that did happen disconnection.
>
> usbhid_disconnect calls usbhid_close by way of
> hid_destroy_device.
below is the content of hid_destroy and hid_remove_device, but I
cannot find where usbhid_close be called by way of hid_destroy_device.
static void hid_remove_device(struct hid_device *hdev)
{
if (hdev->status & HID_STAT_ADDED) {
device_del(&hdev->dev);
hid_debug_unregister(hdev);
hdev->status &= ~HID_STAT_ADDED;
}
kfree(hdev->dev_rdesc);
hdev->dev_rdesc = NULL;
hdev->dev_rsize = 0;
}
void hid_destroy_device(struct hid_device *hdev)
{
hid_remove_device(hdev);
put_device(&hdev->dev);
}
>
> usbhid_close calls hid_cancel_delayed_stuff.
>
> hid_cancel_delayed_stuff calls cancel_work_sync for reset_work.
>
> So the reset_work routine tries to cancel itself synchronously while it
> is running. usb_queue_reset_device was carefully written to avoid such
> deadlocks.
>
thanks for your help,
--
To unsubscribe from this list: send the line "unsubscribe linux-input" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
