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    SubjectRe: [PATCH] timers: consider slack value in mod_timer()
    From
    On Sat, May 21, 2011 at 6:58 PM, Sebastian Andrzej Siewior
    <sebastian@breakpoint.cc> wrote:
    > There is an optimization which does not update the timer if the timer
    > was pending and the expiration time was unchanged.
    > Since commit 3bbb9ec9 ("timers: Introduce the concept of timer slack for
    > legacy timers") this optimization is no longer applied for timers where
    > the expiration time got extended due to the slack value. So here it adds
    > the check again after the expiration time might have been updated.
    >
    > Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
    > ---
    >  kernel/timer.c |    2 ++
    >  1 files changed, 2 insertions(+), 0 deletions(-)
    >
    > diff --git a/kernel/timer.c b/kernel/timer.c
    > index fd61986..bf09726 100644
    > --- a/kernel/timer.c
    > +++ b/kernel/timer.c
    > @@ -804,6 +804,8 @@ int mod_timer(struct timer_list *timer, unsigned long expires)
    >                return 1;
    >
    >        expires = apply_slack(timer, expires);

    So, why not move above line up, then we can use the recalculated
    expires?

    Thanks,
    Yong

    > +       if (timer_pending(timer) && timer->expires == expires)
    > +               return 1;
    >
    >        return __mod_timer(timer, expires, false, TIMER_NOT_PINNED);
    >  }
    > --
    > 1.7.4.4
    >
    > --
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