Re: kernel panic on device removal when using a workqueue and delayed_work

[Frank SchÃfer]

Am 31.10.2011 04:11, schrieb Yong Zhang:
> On Sun, Oct 30, 2011 at 08:19:10PM +0100, Frank Schïfer wrote:
> > Hi,
> >
> > with the following simple kernel module, I have a good chance to get
> > a kernel panic when I unplug the device:
> >
> >
> > #include<linux/workqueue.h>
> > #include<linux/usb.h>
> > #include<linux/module.h>
> >
> > MODULE_AUTHOR("Nobody");
> > MODULE_DESCRIPTION("example driver for causing kernel panic");
> > MODULE_LICENSE("GPL");
> >
> > static struct delayed_work poll_work;
> >
> > static void poll(struct work_struct *work)
> > {
> >      schedule_delayed_work(&poll_work,
> >                    msecs_to_jiffies(100));
> > }
> >
> > 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 const struct usb_device_id device_table[] = {
> >      {USB_DEVICE(0x1234, 0x5678)},
> >      {}
> > };
> >
> > MODULE_DEVICE_TABLE(usb, device_table);
> >
> > static struct usb_driver test_driver = {
> >      .name       = "test",
> >      .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);
> >
> >
> >
> >
> > A picture of the backtrace (the machine immediately turns off
> > without saving a backtrace) can be found at
> >
> > http://imageshack.us/photo/my-images/823/img075gv.jpg
> >
> > Kernel version is 3.1.0.
> >
> >
> > This is the first time I'm using a workqueue, so there is a good
> > chance that I missed something...
> You should cancel the work you have armed before exit.
> See cancel_delayed_work().
That's what I'm doing (see above).
Did you read the code ? ;-)

Regards,
Frank Schaefer
> > Or is this a kernel bug ?
> I don't think so.
>
> Thanks,
> Yong

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