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    SubjectRe: suspend blockers & Android integration

    * Ingo Molnar <mingo@elte.hu> wrote:

    > - Create a 'deep idle' mode that suspends. This, if all constraints
    > are met, is triggered by the scheduler automatically: just like the other
    > idle modes are triggered currently. This approach fixes the wakeup
    > races because an incoming wakeup event will set need_resched() and
    > abort the suspend.
    >
    > ( This mode can even use the existing suspend code to bring stuff down,
    > therefore it also solves the pending timer problem and works even on
    > PC style x86. )

    Note that this does not necessarily have to be implemented as 'execute suspend
    from the idle task' code: scheduling from the idle task, while can certainly
    be made to work, is a somewhat recursive concept that we might want to avoid
    for robustness reasons.

    Instead, the 'deepest idle' (suspend) method could consist of a wakeup of a
    kernel thread (or of any of the existing kernel threads such as the migration
    thread) - which kernel thread then does a race-free suspend: it offlines all
    but one CPU [on platforms that need that] and then initiates the suspend - but
    aborts the attempt if there's any sign of wakeup activity.

    Thanks,

    Ingo


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