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    SubjectRe: [PATCH] hrtimers: Special-case zero length sleeps
    On Wed, Feb 15, 2012 at 03:40:24PM +0100, Thomas Gleixner wrote:
    > > + * be scheduled. Special case that to avoid actually putting them
    > > + * to sleep for the duration of the slack.
    > > + */
    > > + if (rqtp->tv_sec == 0 && rqtp->tv_nsec == 0)
    > > + slack = 0;
    >
    > That's pretty pointless. You can simply return 0 here as
    > do_nanosleep() will not call the scheduler on an already expired
    > timer, which is always true for a relative timer with delta 0.

    I'm actually starting to wonder about the applications doing this. We
    default to adding a small amount of slack even if the application has
    done sleep(0), which will mean that the timer hasn't expired at this
    point. Do we then go through the scheduler differently? Are these
    applications actually relying on an invalid assumption?

    --
    Matthew Garrett | mjg59@srcf.ucam.org


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