Messages in this thread | | | Date | Thu, 12 Jan 2012 12:09:27 +0600 | Subject | Re: [Question] sched: Should nr_uninterruptible be decremented in ttwu_do_activate()? | From | Rakib Mullick <> |
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On Wed, Jan 11, 2012 at 11:29 PM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: > On Wed, 2012-01-11 at 23:22 +0600, Rakib Mullick wrote: >> Hello all, >> >> In ttwu_do_activate(), we're decrementing nr_uninterruptible if >> p->sched_contributes_to_load (for SMP=y). But, we're also decrementing >> nr_uninterruptible from activate_task at the same path. Why we're >> doing it twice for a single task activation path? > > activate_task() does: > > if (task_contributes_to_load(p)) > rq->nr_uninterruptible--; > > Now task_contributes_to_load() reads like: > > #define task_contributes_to_load(task) \ > ((task->state & TASK_UNINTERRUPTIBLE) != 0 && \ > (task->flags & PF_FREEZING) == 0) > > which will be false, since we've set TASK_WAKING.
Enough confusing. TASK_WAKING will be set when called from try_to_wake_up(). ttwu_do_activate() gets called from other places: scheduler_ipi() and sched_ttwu_pending() (at the time of cpu goes down). TASK_WAKING will be not set at that time, moreover it is possible that, task has p->sched_contributes_to_load is set and latter on gets wake up by sched_ttwu_pending/scheduler_ipi() call.
Thanks, Rakib -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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