Workqueue and kernel panic on device disconnect

[fschaefer.oss@googlemail.com (Frank Schäfer)]

Hi,

I'm trying to use a workqueue in a usb driver for polling the states of 
the device buttons.
That works fine, but when I disconnect the device, the kernel sometimes 
explodes.
The machine turns off immediately, without saving a backtrace (I will 
try to make a photo tomorrow)

The code:



static struct delayed_work poll_work;

static const struct usb_device_id device_table[] = {
     {USB_DEVICE(0x1234, 0x5678)},
     {}
};

static void poll(struct work_struct *work)
{
     schedule_delayed_work(&poll_work,
                   msecs_to_jiffies(100));
}

MODULE_DEVICE_TABLE(usb, device_table);

static int test_probe(struct usb_interface *intf,
               const struct usb_device_id *id)
{
     INIT_DELAYED_WORK(&poll_work, poll);
     schedule_delayed_work(&poll_work,
                   msecs_to_jiffies(100));
     return 0;
}

static void test_disconnect(struct usb_interface *intf)
{
     cancel_delayed_work_sync(&poll_work);
}

static struct usb_driver test_driver = {
     .name       = MODULE_NAME,
     .id_table   = device_table,
     .probe      = test_probe,
     .disconnect = test_disconnect,
};

static int __init test_mod_init(void)
{
     return usb_register(&test_driver);
}

static void __exit test_mod_exit(void)
{
     usb_deregister(&test_driver);
}

module_init(test_mod_init);
module_exit(test_mod_exit);


What am I doing wrong ?
Is there anything else I have to do in addition to calling 
cancel_delayed_work_sync() in the disconnect fcn ?

Thanks,
Frank Schaefer