On Mon, 28 Jun 2010, Rafael J. Wysocki wrote:
> > > +bool pm_get_wakeup_count(unsigned long *count)
> > > +{
> > > + bool ret;
> > > +
> > > + spin_lock_irq(&events_lock);
> > > + if (capable(CAP_SYS_ADMIN))
> > > + events_check_enabled = false;
> > > +
> > > + if (events_in_progress) {
> > > + DEFINE_WAIT(wait);
> > > +
> > > + do {
> > > + prepare_to_wait(&events_wait_queue, &wait,
> > > + TASK_INTERRUPTIBLE);
> > > + if (!events_in_progress)
> > > + break;
> > > + spin_unlock_irq(&events_lock);
> > > +
> > > + schedule();
> > > +
> > > + spin_lock_irq(&events_lock);
> > > + } while (!signal_pending(current));
> > > + finish_wait(&events_wait_queue, &wait);
> > > + }
> > > + *count = event_count;
> > > + ret = !events_in_progress;
> > > + spin_unlock_irq(&events_lock);
> > > + return ret;
> > > +}
> >
> > Here's a thought. Presumably pm_relax() will end up getting called a
> > lot more often than pm_get_wakeup_count(). Instead of using a wait
> > queue, you could make pm_get_wakeup_count() poll at 100-ms intervals.
> > The total overhead would be smaller.
>
> For that I'd need a separate kernel thread or a work item that would reschedule
> itself periodically, because pm_get_wakeup_count() is only called via
> /sys/power/wakeup_count. It would complicate things quite a bit which I'm not
> sure is worth it at this point.
What? All I'm saying is that the do-while loop above should be
replaced by a loop that sleeps for 100 ms instead of waiting on a
wait_queue. That is:
while (events_in_progress) {
if (signal_pending(current))
break;
spin_unlock_irq(&events_lock);
schedule_timeout_interruptible(msecs_to_jiffies(100));
spin_lock_irq(&events_lock);
}
And of course, get rid of events_wait_queue.
Alan Stern
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