On Thu, Dec 22, 2005 at 22:41:48 -0800, Rajaram Suryanarayanan wrote:
> Hi,
>
> I wrote a simple kernel module to play with the process descriptor structure of a process. I have given the code below.
>
> int init_module(void)
> {
>
> printk(KERN_INFO "Hello Process \n");
> printk(KERN_INFO "Parent process ID :%d \n",current->parent->pid);
> printk(KERN_INFO "Parent process state :%d \n",current->parent->state);
> printk(KERN_INFO "Parent process uid :%d \n",current->parent->uid);
> printk(KERN_INFO "Parent process priority :%d \n",current->parent->prio);
>
> /* Change the parent process state to unrannable */
> current->parent->state= -1;
> return 0;
>
> }
>
> By this code, I am trying to print the details of the parent process of
> the current process ( current process is insmod and its parent process is
> the bash shell from which I issued insmod command, if I am not wrong ).
Yes, you are right.
> Also I try to change the state of the bash shell to -1 ( unrunnable ).
I see it in the comment, but that state does not seem to actually exist.
> I see that the current->parent->state is printed as 1 . I see that process
> state > 0 is stopped , as defined in "struct task_struct". Then why it is
> printed as 1 when the bash shell is actually running ?
No, it's not actually running. It's waiting for it's child to exit or be
stopped, inside wait syscall. State 1 is TASK_INTERRUPTIBLE.
> Also by changing the state of the bash shell to -1, I expected it to hang
> or something like that. But that did not happen.
>
> Could anyone please let me know what is wrong with my approach..?
Don't use the numbers. Use the symbolic values TASK_RUNNING,
TASK_INTERRUPTIBLE, TASK_UNINTERRUPTIBLE and so on.
However, that's not the major problem. The major problem is, that it's only
permitted to alter your own state (that is set_current_state) except
well-defined case of waking up a process on a wait-queue.
--
Jan 'Bulb' Hudec <bulb@xxxxxx>
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