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    SubjectRe: suspend blockers & Android integration

    * 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


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