Re: suspend blockers & Android integration

[Ingo Molnar <mingo@elte.hu>]

* Arve Hj?nnev?g <arve@android.com> wrote:

> On Thu, Jun 3, 2010 at 4:23 PM, Ingo Molnar <mingo@elte.hu> wrote:
> ...
> > ?- Controlled auto-suspend: drivers (such as input) could on wakeup
> > ? automatically set the 'minimum wakeup latency' value of wakee tasks to a
> > ? lower value. This automatically prevents another auto-suspend in the near
> > ? future: up to the point the wakee task increases its latency (via the
> > ? scheduler syscall) again and allows suspend again.
> >
> 
> How do you clear the latency value in a safe way? If another wakeup event 
> happens right after your wakee task is done processing the last event and 
> decides to increase its latency, auto suspend will be allowed even though 
> you have an unprocessed wakeup event. Also how do you know which task will 
> read the event if it is not already waiting for it?

The easiest solution would be to not do any of that initially. (If it's ever a 
concern we could subtract/add without destroying the nesting property)

Why do you need to track input wakeups? It's rather fragile and rather 
unnecessary - the idle drivers know it very well how to not go into the 
deepest idle mode already today. We wont hit C8 on laptops when you are using 
the desktop.

> > ? This means there will be no surprise suspends for a task that may take a
> > ? bit longer than usual to finish its work. [ Detail: this would only be done
> > ? for tasks that have a non-default (non-infinity) task->latency value - to
> > ? prevent the input driver from lowering latency values (and preventing
> > ? future suspends) just because some unaware apps are running and using input
> > ? drivers. ]
> 
> Don't you need two inifinity values for this?

Yes - any value above the max idle latency in the system will do.

Thanks,

	Ingo