Messages in this thread | | | Subject | Re: [Question] sched: Should nr_uninterruptible be decremented in ttwu_do_activate()? | From | Peter Zijlstra <> | Date | Thu, 12 Jan 2012 08:25:30 +0100 |
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On Thu, 2012-01-12 at 12:09 +0600, Rakib Mullick wrote: > 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,
Yes it will be, the only way to get on that list is throught ttwu_queue_remote() at which point tasks are TASK_WAKING.
> 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.
That's the entire point. But all ways to ttwu_queue_remote() explicitly set ->sched_contributes_to_load.
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