Hi, Peter
On 02/11/2014 08:17 PM, tip-bot for Peter Zijlstra wrote:
[snip]
> +
> +idle:
> +#ifdef CONFIG_SMP
> + idle_enter_fair(rq);
> + /*
> + * We must set idle_stamp _before_ calling idle_balance(), such that we
> + * measure the duration of idle_balance() as idle time.
> + */
> + rq->idle_stamp = rq_clock(rq);
> + if (idle_balance(rq)) { /* drops rq->lock */
Since idle_balance() will release the rq lock, will it happen that some
rt or dl tasks was waken up and enqueued before it hold the lock again?
Should we recheck 'rq->nr_running == rq->cfs.h_nr_running' here before
goto pick fair entity to make sure the priority?
May be like:
if (idle_balance(rq) &&
rq->nr_running == rq->cfs.h_nr_running)
Regards,
Michael Wang
> + rq->idle_stamp = 0;
> + goto again;
> + }
> +#endif
> +
> + return NULL;
> }
>
> /*
> diff --git a/kernel/sched/idle_task.c b/kernel/sched/idle_task.c
> index 721371b..f7d03af 100644
> --- a/kernel/sched/idle_task.c
> +++ b/kernel/sched/idle_task.c
> @@ -13,13 +13,8 @@ select_task_rq_idle(struct task_struct *p, int cpu, int sd_flag, int flags)
> {
> return task_cpu(p); /* IDLE tasks as never migrated */
> }
> -
> -static void pre_schedule_idle(struct rq *rq, struct task_struct *prev)
> -{
> - idle_exit_fair(rq);
> - rq_last_tick_reset(rq);
> -}
> #endif /* CONFIG_SMP */
> +
> /*
> * Idle tasks are unconditionally rescheduled:
> */
> @@ -56,6 +51,10 @@ dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
>
> static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
> {
> +#ifdef CONFIG_SMP
> + idle_exit_fair(rq);
> + rq_last_tick_reset(rq);
> +#endif
> }
>
> static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
> @@ -99,7 +98,6 @@ const struct sched_class idle_sched_class = {
>
> #ifdef CONFIG_SMP
> .select_task_rq = select_task_rq_idle,
> - .pre_schedule = pre_schedule_idle,
> #endif
>
> .set_curr_task = set_curr_task_idle,
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index a15ca1c..72f9ec7 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -229,6 +229,8 @@ int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
>
> #ifdef CONFIG_SMP
>
> +static int pull_rt_task(struct rq *this_rq);
> +
> static inline int rt_overloaded(struct rq *rq)
> {
> return atomic_read(&rq->rd->rto_count);
> @@ -1330,6 +1332,12 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev)
> struct task_struct *p;
> struct rt_rq *rt_rq = &rq->rt;
>
> +#ifdef CONFIG_SMP
> + /* Try to pull RT tasks here if we lower this rq's prio */
> + if (rq->rt.highest_prio.curr > prev->prio)
> + pull_rt_task(rq);
> +#endif
> +
> if (!rt_rq->rt_nr_running)
> return NULL;
>
> @@ -1721,13 +1729,6 @@ skip:
> return ret;
> }
>
> -static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
> -{
> - /* Try to pull RT tasks here if we lower this rq's prio */
> - if (rq->rt.highest_prio.curr > prev->prio)
> - pull_rt_task(rq);
> -}
> -
> static void post_schedule_rt(struct rq *rq)
> {
> push_rt_tasks(rq);
> @@ -2004,7 +2005,6 @@ const struct sched_class rt_sched_class = {
> .set_cpus_allowed = set_cpus_allowed_rt,
> .rq_online = rq_online_rt,
> .rq_offline = rq_offline_rt,
> - .pre_schedule = pre_schedule_rt,
> .post_schedule = post_schedule_rt,
> .task_woken = task_woken_rt,
> .switched_from = switched_from_rt,
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index c534cf4..1bf34c2 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1118,7 +1118,6 @@ struct sched_class {
> int (*select_task_rq)(struct task_struct *p, int task_cpu, int sd_flag, int flags);
> void (*migrate_task_rq)(struct task_struct *p, int next_cpu);
>
> - void (*pre_schedule) (struct rq *this_rq, struct task_struct *task);
> void (*post_schedule) (struct rq *this_rq);
> void (*task_waking) (struct task_struct *task);
> void (*task_woken) (struct rq *this_rq, struct task_struct *task);
> --
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