Messages in this thread | | | Subject | Re: [PATCH 1/2] sched: Drop the need_resched() loop from cond_resched() | From | Peter Zijlstra <> | Date | Fri, 10 Jul 2009 17:00:45 +0200 |
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On Fri, 2009-07-10 at 16:49 +0200, Frederic Weisbecker wrote: > The schedule() function is a loop that reschedules the current task > while the TIF_NEED_RESCHED flag is set: > > void schedule(void) > { > need_resched: > /* schedule code */ > if (need_resched()) > goto need_resched; > } > > And cond_resched() repeat this loop: > > do { > add_preempt_count(PREEMPT_ACTIVE); > schedule(); > sub_preempt_count(PREEMPT_ACTIVE); > } while(need_resched()); > > This loop is needless because schedule() already did the check and > nothing can set TIF_NEED_RESCHED between schedule() exit and the loop > check in need_resched(). > > Then remove this needless loop. > > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> --- > kernel/sched.c | 8 +++----- > 1 files changed, 3 insertions(+), 5 deletions(-) > > diff --git a/kernel/sched.c b/kernel/sched.c > index 4d1e387..87ecac1 100644 > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -6613,11 +6613,9 @@ static void __cond_resched(void) > * PREEMPT_ACTIVE, which could trigger a second > * cond_resched() call. > */ > - do { > - add_preempt_count(PREEMPT_ACTIVE); > - schedule(); > - sub_preempt_count(PREEMPT_ACTIVE); > - } while (need_resched()); > + add_preempt_count(PREEMPT_ACTIVE); > + schedule(); > + sub_preempt_count(PREEMPT_ACTIVE); > } > > int __sched _cond_resched(void)
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