Hi Dinesh...
> Sorry for being late in replying back. I have used
> schedule_timeout and it is working fine. But curious
> to know what wrong is going on while using wait
> queues.
> I am working on kernel 2.4.20
> Here is full code:
[deleted]...
> set_current_state(TASK_INTERRUPTIBLE);
I think this is the problem. You set a running task into sleeping state,
but didn't quickly follow it with re-scheduling function (that
implicitly use wait queue too). What happen here was, your kernel
thread was declared in sleeping state, time slice was running out, your
thread was kicked out from CPU but wasn't runnable anymore.
Actually, you don't need it, because interruptible_sleep_time_out do it
all for your.
I'll give another example how it is really done if you want to do it on
very low level way. Take a look on wait_for_completion(). Comments are
added inline:
void wait_for_completion(struct completion *x)
{
spin_lock_irq(&x->wait.lock);
if (!x->done) {
// [Mulyadi]: declare a wait queue
DECLARE_WAITQUEUE(wait, current);
wait.flags |= WQ_FLAG_EXCLUSIVE;
// [Mulyadi]: add to the wait queue first
__add_wait_queue_tail(&x->wait, &wait);
do {
// [Mulyadi]: and then mark the current task as interruptible
__set_current_state(TASK_UNINTERRUPTIBLE);
spin_unlock_irq(&x->wait.lock);
// [Mulyadi]: feel free to reschedule
schedule();
spin_lock_irq(&x->wait.lock);
} while (!x->done);
// [Mulyadi]: if you are done with it, remove the task from wait queue
__remove_wait_queue(&x->wait, &wait);
}
x->done--;
spin_unlock_irq(&x->wait.lock);
}
That way, the kernel knows that you're asking to be woken up when a
signal is delivered, an event happens or simply because of timeout.
So the conclusion is, as far as I know, declare a waitqueue, insert the
task to waitqueue, and set the task state. Don't mess this order...
regards,
Mulyadi
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