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sched/deadline: Add SCHED_DEADLINE inheritance logic

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Some method to deal with rt-mutexes and make sched_dl interact with
the current PI-coded is needed, raising all but trivial issues, that
needs (according to us) to be solved with some restructuring of
the pi-code (i.e., going toward a proxy execution-ish implementation).

This is under development, in the meanwhile, as a temporary solution,
what this commits does is:

 - ensure a pi-lock owner with waiters is never throttled down. Instead,
   when it runs out of runtime, it immediately gets replenished and it's
   deadline is postponed;

 - the scheduling parameters (relative deadline and default runtime)
   used for that replenishments --during the whole period it holds the
   pi-lock-- are the ones of the waiting task with earliest deadline.

Acting this way, we provide some kind of boosting to the lock-owner,
still by using the existing (actually, slightly modified by the previous
commit) pi-architecture.

We would stress the fact that this is only a surely needed, all but
clean solution to the problem. In the end it's only a way to re-start
discussion within the community. So, as always, comments, ideas, rants,
etc.. are welcome! :-)

Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
[ Added !RT_MUTEXES build fix. ]
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1383831828-15501-11-git-send-email-juri.lelli@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Dario Faggioli
2013-11-07 14:43:44 +01:00
committed by Ingo Molnar
parent fb00aca474
commit 2d3d891d33
9 changed files with 134 additions and 54 deletions
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36
kernel/sched/core.c
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@@ -947,7 +947,7 @@ static inline void check_class_changed(struct rq *rq, struct task_struct *p,
if (prev_class->switched_from)
prev_class->switched_from(rq, p);
p->sched_class->switched_to(rq, p);
} else if (oldprio != p->prio)
} else if (oldprio != p->prio || dl_task(p))
p->sched_class->prio_changed(rq, p, oldprio);
}
@@ -2781,7 +2781,7 @@ EXPORT_SYMBOL(sleep_on_timeout);
*/
void rt_mutex_setprio(struct task_struct *p, int prio)
{
int oldprio, on_rq, running;
int oldprio, on_rq, running, enqueue_flag = 0;
struct rq *rq;
const struct sched_class *prev_class;
@@ -2808,6 +2808,7 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
}
trace_sched_pi_setprio(p, prio);
p->pi_top_task = rt_mutex_get_top_task(p);
oldprio = p->prio;
prev_class = p->sched_class;
on_rq = p->on_rq;
@@ -2817,19 +2818,42 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
if (running)
p->sched_class->put_prev_task(rq, p);
if (dl_prio(prio))
/*
* Boosting condition are:
* 1. -rt task is running and holds mutex A
* --> -dl task blocks on mutex A
*
* 2. -dl task is running and holds mutex A
* --> -dl task blocks on mutex A and could preempt the
* running task
*/
if (dl_prio(prio)) {
if (!dl_prio(p->normal_prio) || (p->pi_top_task &&
dl_entity_preempt(&p->pi_top_task->dl, &p->dl))) {
p->dl.dl_boosted = 1;
p->dl.dl_throttled = 0;
enqueue_flag = ENQUEUE_REPLENISH;
} else
p->dl.dl_boosted = 0;
p->sched_class = &dl_sched_class;
else if (rt_prio(prio))
} else if (rt_prio(prio)) {
if (dl_prio(oldprio))
p->dl.dl_boosted = 0;
if (oldprio < prio)
enqueue_flag = ENQUEUE_HEAD;
p->sched_class = &rt_sched_class;
else
} else {
if (dl_prio(oldprio))
p->dl.dl_boosted = 0;
p->sched_class = &fair_sched_class;
}
p->prio = prio;
if (running)
p->sched_class->set_curr_task(rq);
if (on_rq)
enqueue_task(rq, p, oldprio < prio ? ENQUEUE_HEAD : 0);
enqueue_task(rq, p, enqueue_flag);
check_class_changed(rq, p, prev_class, oldprio);
out_unlock: