Re: puting task to TASK_INTERRUPTIBLE before adding it to an wait queue

["Yitzchak Eidus" <ieidus@gmail.com>]

On 3/17/06, Yitzchak Eidus <ieidus@gmail.com> wrote:
> the function worker_thread in kernel 2.6.15.6  first put the task to
> TASK_INTERRUPTIBLE and only then add itself to an wait queue:
>         set_current_state(TASK_INTERRUPTIBLE);
>         while (!kthread_should_stop()) {
>                 add_wait_queue(&cwq->more_work, &wait);
> ....
> my question is, what will happen if the timeslice for the
> worker_thread will finished just before it add itself to the wait
> queue?
> wont it call schedule() that will find the task is in
> TASK_INTERRUPTIBLE state and remove it from the runqueue? ( that what
> schedule() should do no? )
> and then how will the kernel be able to call to worker_thread ever if
> it isnt in any list???
> thanks for the comments!
>

more over the whole loop look like that:
set_current_state(TASK_INTERRUPTIBLE);
	while (!kthread_should_stop()) {
		add_wait_queue(&cwq->more_work, &wait);
		if (list_empty(&cwq->worklist))
			schedule();
		else
			__set_current_state(TASK_RUNNING);
		remove_wait_queue(&cwq->more_work, &wait);

		if (!list_empty(&cwq->worklist))
			run_workqueue(cwq);
		set_current_state(TASK_INTERRUPTIBLE);
	}

what was the logic of putting the
set_current_state(TASK_INTERRUPTIBLE); before the loop and in the last
statement of the loop?

why not use something like this:
while (!kthread_should_stop()) {
		add_wait_queue(&cwq->more_work, &wait);
		set_current_state(TASK_INTERRUPTIBLE);
		if (list_empty(&cwq->worklist))
			schedule();
		else
			__set_current_state(TASK_RUNNING);
		remove_wait_queue(&cwq->more_work, &wait);

		if (!list_empty(&cwq->worklist))
			run_workqueue(cwq);
	}
that do the same thing without putting the task before the loop and in
the loop...?
( unless i am missing something? )