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    SubjectRe: [RFD] Automatic suspend
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    On Sat, Feb 28, 2009 at 2:53 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
    > On Saturday 28 February 2009, Arve Hjønnevåg wrote:
    >> Can you summarize what the problems with my current api are? I get the
    >> impression that you think the overhead of using a list is too high,
    >> and that timeout support should be removed because you think all
    >> drivers that use it are broken.
    >
    > In no particular order:
    > 1. One user space process can create an unlimited number of wakelocks.  This
    >   shouldn't be possible.  Moreover, it is not even necessary for any process
    >   to have more than one wakelock held at any time.

    This has been addressed. A user space process cannot create more
    wakelocks than it has filedescriptors.

    > 2. Timeouts are wrong, because they don't really _solve_ any problem.  They are
    >   useful for working around the fact that you can't or you don't want to
    >   modify every piece of code that in principle should take a wakelock and
    >   that's it.

    Yes, timeouts are sometimes wrong, but they are not always wrong. I
    gave two examples where the use of timeouts was not incorrect.

    >  However,  entire concept of having one code path acting on
    >   behalf of another one on a hunch that it might be doing something making
    >   suspend undesirable is conceptually broken IMO.

    OK. Do you have an alternative?

    I my opinion this is how the entire system works if you do autosuspend
    without a mechanism like wakelocks.

    > 3. The overhead of using a list is unnecessary and _therefore_ too high (not
    >   just too high).

    It is only unnecessary if you do not want accounting or timeouts. The
    overhead of a timer going off when it is not needed (if you push
    timeouts to the drivers) is way higher then the overhead putting
    wakelocks on a list.

    > 4. There seems to be a race between user space wakelocks and the freezer
    >   (perhaps I overlooked something, in which case please disregard this item).

    You are missing something. Wakelocks overlap.

    > 5. The name "wakelocks" is confusing, because they aren't locks and they
    >   affect suspend, not wake.

    I can change the name. Currently suspend_blocker seems to be
    acceptable many people, but some don't like this name either.

    > 6. Last time I saw the patches they were barely commented and the changelogs
    >   didn't describe the code well (if at all).

    I have not added many inline comments, but I did add the kerneldoc
    comments you requested, and a lot of documentation since the first
    patches.

    > 7. There's no clear distinction between debug/stats code and the basic
    >   functionality.

    I don't think this is still true.

    --
    Arve Hjønnevåg
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