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SubjectRe: kernel panic on device removal when using a workqueue and delayed_work
On Sun, Oct 30, 2011 at 08:19:10PM +0100, Frank Sch�fer 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().

> Or is this a kernel bug ?

I don't think so.

Thanks,
Yong
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