On Fri, Jul 05, 2013 at 02:06:32PM +0400, Kirill Tkhai wrote:
> The patch introduces new primitives for waking up tasks, latencies of which
> are appreciable by user directly, that need the first-order interactivity.
>
> The appliable area is not wide. It's generally input subsystem and wake_ups
> of tasks waiting for user actions: keyboard press, mouse movement etc.
Ha! before you know it tons of drivers are using this because they all
think their interrupts it the most important thing on earth.. seriously!
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 01970c8..8b8b328 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -1226,8 +1226,21 @@ out:
> return cpu;
> }
>
> -static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
> +static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p,
> int flags)
> {
> + /*
> + * If:
> + *
> + * - the newly woken task is of equal priority to the current task
> + * - the newly woken task is non-migratable while current is migratable
> + * - current will be preempted on the next reschedule
> + *
> + * we should check to see if current can readily move to a different
> + * cpu. If so, we will reschedule to allow the push logic to try
> + * to move current somewhere else, making room for our non-migratable
> + * task.
> + */
> +
> if (rq->curr->nr_cpus_allowed == 1)
> return;
>
> @@ -1235,7 +1248,8 @@ static void check_preempt_equal_prio(struct rq *rq,
> struct task_struct *p)
> && cpupri_find(&rq->rd->cpupri, p, NULL))
> return;
>
> - if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
> + if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL) &&
> + !(flags & WF_PREEMPT))
> return;
>
> /*
> @@ -1246,7 +1260,15 @@ static void check_preempt_equal_prio(struct rq *rq,
> struct task_struct *p)
> requeue_task_rt(rq, p, 1);
> resched_task(rq->curr);
> }
> +#else /* !CONFIG_SMP */
> +static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p,
> int flags)
> +{
> + if (!(flags & WF_PREEMPT))
> + return;
>
> + requeue_task_rt(rq, p, 1);
> + resched_task(rq->curr);
> +}
You can't do this:
http://pubs.opengroup.org/onlinepubs/009696899/functions/xsh_chap02_08.html
SCHED_FIFO;
2) When a blocked thread becomes a runnable thread, it becomes the tail
of the thread list for its priority.
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