Hello, Anrea.
On Wed, Nov 09, 2011 at 06:29:42PM +0100, Andrea Arcangeli wrote:
> My point is if what happens is:
>
> freezer CPU khugepaged
> ------
> assert freezing
> wake_up(interruptible)
> __set_current_state(interruptible)
> schedule()
>
> are we still hanging then?
Yeap, you're right. I was thinking INTERRUPTILBE was being set before
try_to_freeze().
> And I think it's silly to use wait_event_freezable_timeout if I
> don't have any waitqueue to wait on.
I'm confused. You're doing add_wait_queue() before
schedule_timeout_interruptible(). prepare_to_wait() is essentially
add_wait_queue() + set_current_state(). What am I missing? ie. why
not do the following?
prepare_to_wait(INTERRUPTIBLE);
try_to_freeze();
schedule_timeout();
try_to_freeze();
finish_wait();
or even simpler,
wait_event_freezable_timeout(wq, false, timeout);
In terms of overhead, there is no appreciable difference from
add_wait_queue();
schedule_timeout_interruptible();
remove_wait_queue()
Or is the logic there scheduled to change?
> +signed long __sched schedule_timeout_freezable(signed long timeout)
> +{
> + do
> + set_current_state(TASK_INTERRUPTIBLE);
> + while (try_to_freeze());
> + return schedule_timeout(timeout);
> +}
> +EXPORT_SYMBOL(schedule_timeout_freezable);
Hmmm... I don't know. I really hope all freezable tasks stick to
higher level interface. It's way too easy to get things wrong and eat
either freezing or actual wakeup condition.
Thank you.
--
tejun
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