Re: SIGKILL and a sleeping kernel module

[Srinivas Ganji <srinivasganji.kernel@xxxxxxxxx>]

On Wed, Feb 20, 2013 at 11:59 AM, Srinivas Ganji <srinivasganji.kernel@xxxxxxxxx> wrote:

On Tue, Feb 19, 2013 at 5:02 PM, Kevin Wilson <wkevils@xxxxxxxxx> wrote:

Hi,

Thanks about the info about ps.
This raises two new questions:
1)  The following code is a very basic kernel module (based on my
previous code, removing somethings).
I do not understand something:
I call
  /* sleep for a millisecond */
    msleep(1);

    printk("calling do_exit\n");

    msleep(60000);

In my understanding, after 1 millisecond, it should have been
available to the scheduler, and after returning to the line after
msleep(1), it should print "calling do_exit". However,
I see no such log message. Any ideas why ? can something be
added to enable this ?

2)How can I create a kernel thread so that it will be in
TASK_INTERRUPTIBLE state ? there must be a way,
since I see many kernel threads where ps shows "S" in the
status coumn.

struct task_struct *task;

int thread_function(void *data)
{
    int exit_sig = SIGKILL;

    printk("in %s\n",__func__);

    /* sleep for a millisecond */
    msleep(1);

    printk("calling do_exit\n");

    msleep(60000);

    do_exit(exit_sig);

    return 0;
}

static int kernel_init(void)
    {

    printk("in kernel_init\n");

    task = kthread_create(thread_function,NULL,"MY_KERNEL_THREAD");
    return 0;
}

static void kernel_exit(void)
    {
    printk("in kernel_exit\n");
    kthread_stop(task);
    }


module_init(kernel_init);
module_exit(kernel_exit);

rgs

Kevin

After creating the kernel thread, you can use wake_up_process(task) call which will run your thread function.

Generally, when we create a kernel thread using kthread_create, 

the process is created in an unrunnable state. It will not start running until explicitly woken up via wake_up_process(). The kthread_create() followed by wake_up_process() is done by a single call kthread_run().

I hope this helps you.

Regards

Srinivas G. 

 

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