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Date: Sun, 30 Oct 2011 20:19:10 +0100
From: =?ISO-8859-15?Q?Frank_Sch=E4fer?= <fschaefer.oss@googlemail.com>
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To: linux-kernel@vger.kernel.org
Subject: kernel panic on device removal when using a workqueue and delayed_work
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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...
Or is this a kernel bug ?


Regards,
Frank Schaefer