Messages in this thread | | | Date | Sun, 28 Feb 2010 13:33:13 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 07/43] sched: implement try_to_wake_up_local() |
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Wow ;)
I didn't read the whole series yet, still I'd like to ask a couple of questions right now. Tejun, I am just trying to understand this code.
On 02/26, Tejun Heo wrote: > > @@ -2438,6 +2438,10 @@ static inline void ttwu_post_activation(struct task_struct *p, struct rq *rq, > rq->idle_stamp = 0; > } > #endif > + /* > + * Wake up is complete, fire wake up notifier. This allows > + * try_to_wake_up_local() to be called from wake up notifiers. > + */ > if (success) > fire_sched_notifiers(p, wakeup);
Could you explain the comment? ttwu_post_activation() sets state = TASK_RUNNING few lines above, what try_to_wake_up_local() can do if called from ->wakeup() notifier ?
> +bool try_to_wake_up_local(struct task_struct *p, unsigned int state, > + int wake_flags) > +{ > ... > + if (!p->se.on_rq) { > + if (likely(!task_running(rq, p))) { > + schedstat_inc(rq, ttwu_count); > + schedstat_inc(rq, ttwu_local); > + } > + ttwu_activate(p, rq, wake_flags & WF_SYNC, false, true); > + success = true; > + }
Shouldn't try_to_wake_up_local() check task_contributes_to_load() to account ->nr_uninterruptible?
> @@ -5498,6 +5549,11 @@ need_resched_nonpreemptible: > if (unlikely(signal_pending_state(prev->state, prev))) { > prev->state = TASK_RUNNING; > } else { > + /* > + * Fire sleep notifier before changing any scheduler > + * state. This allows try_to_wake_up_local() to be > + * called from sleep notifiers. > + */ > fire_sched_notifiers(prev, sleep); > deactivate_task(rq, prev, 1);
Again, I don't understand the comment... If ->sleep() notifier wakes up this task, we shouldn't do deactivate_task() ?
Probably both comment mean a notifier could wake up another task bound to this rq, in this case it looks a bit confusing, imho.
Off-topic, but it is a bit sad wait_task_inactive() can not use ->sleep() notifier to avoid schedule_timeout(), afaics we can't add the notifier to !current task.
Oleg.
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