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    SubjectRe: [linux-pm] [PATCH] PM: Make it possible to avoid wakeup events from being lost
    On Sat, 26 Jun 2010, David Brownell wrote:

    > > > basically, I think the notion of counting wakeup
    > > > events seems dubious on common hardware, ...
    > > I disagree. 
    > >
    > > The "counting" isn't meant as a way of keeping track of the absolute
    > > number of these events.  It's more like a technique for seeing how many
    > > remain outstanding at any time.
    > But if you can't count them with any
    > reliability, you can't know *that* either... so
    > there must be a a problem with that model.

    Why do you say we can't count them with any reliability?

    Or, let's put it another way: You'll grant that we can count _some_ set
    of events. Given that, you'll probably also grant that we can keep
    track of their number reliably enough to know when the count has
    dropped to 0. Then this becomes a question of how closely does the set
    of events we can count match up with the set of "wakeup" events?

    In fact, it doesn't have to match up perfectly. There may be a few
    wakeup events where we don't really care if one of them occurs while
    the system is going to sleep and the sleep isn't delayed or aborted.
    (Although by definition this is never _supposed_ to happen, there may
    be cases where we just don't care.) The other possibility is
    relatively harmless too: an event that wouldn't wake up a sleeping
    system nevertheless can delay or abort a suspend-in-progress.

    So overall I don't see a problem with this. Do you have any especially
    pernicious failure modes in mind?

    Alan Stern

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