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sched: rt-group: deal with PI

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Steven mentioned the fun case where a lock holding task will be throttled.

Simple fix: allow groups that have boosted tasks to run anyway.

If a runnable task in a throttled group gets boosted the dequeue/enqueue
done by rt_mutex_setprio() is enough to unthrottle the group.

This is ofcourse not quite correct. Two possible ways forward are:
  - second prio array for boosted tasks
  - boost to a prio ceiling (this would also work for deadline scheduling)

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2008-02-13 15:45:39 +01:00 committed by Ingo Molnar
parent 4cf5d77a6e
commit 23b0fdfc92
2 changed files with 41 additions and 5 deletions
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3
kernel/sched.c
View File

@ -362,6 +362,8 @@ struct rt_rq {
u64 rt_time;
#ifdef CONFIG_FAIR_GROUP_SCHED
unsigned long rt_nr_boosted;
struct rq *rq;
struct list_head leaf_rt_rq_list;
struct task_group *tg;
@ -7112,6 +7114,7 @@ static void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq)
rt_rq->rt_throttled = 0;
#ifdef CONFIG_FAIR_GROUP_SCHED
rt_rq->rt_nr_boosted = 0;
rt_rq->rq = rq;
#endif
}

43
kernel/sched_rt.c
View File

@ -110,6 +110,23 @@ static void sched_rt_ratio_dequeue(struct rt_rq *rt_rq)
dequeue_rt_entity(rt_se);
}
static inline int rt_rq_throttled(struct rt_rq *rt_rq)
{
return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
}
static int rt_se_boosted(struct sched_rt_entity *rt_se)
{
struct rt_rq *rt_rq = group_rt_rq(rt_se);
struct task_struct *p;
if (rt_rq)
return !!rt_rq->rt_nr_boosted;
p = rt_task_of(rt_se);
return p->prio != p->normal_prio;
}
#else
static inline unsigned int sched_rt_ratio(struct rt_rq *rt_rq)
@ -149,6 +166,10 @@ static inline void sched_rt_ratio_dequeue(struct rt_rq *rt_rq)
{
}
static inline int rt_rq_throttled(struct rt_rq *rt_rq)
{
return rt_rq->rt_throttled;
}
#endif
static inline int rt_se_prio(struct sched_rt_entity *rt_se)
@ -172,7 +193,7 @@ static int sched_rt_ratio_exceeded(struct rt_rq *rt_rq)
return 0;
if (rt_rq->rt_throttled)
return 1;
return rt_rq_throttled(rt_rq);
period = (u64)sysctl_sched_rt_period * NSEC_PER_MSEC;
ratio = (period * rt_ratio) >> SCHED_RT_FRAC_SHIFT;
@ -183,8 +204,10 @@ static int sched_rt_ratio_exceeded(struct rt_rq *rt_rq)
rq->rt_throttled = 1;
rt_rq->rt_throttled = 1;
sched_rt_ratio_dequeue(rt_rq);
return 1;
if (rt_rq_throttled(rt_rq)) {
sched_rt_ratio_dequeue(rt_rq);
return 1;
}
}
return 0;
@ -265,6 +288,10 @@ void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
update_rt_migration(rq_of_rt_rq(rt_rq));
#endif
#ifdef CONFIG_FAIR_GROUP_SCHED
if (rt_se_boosted(rt_se))
rt_rq->rt_nr_boosted++;
#endif
}
static inline
@ -295,6 +322,12 @@ void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
update_rt_migration(rq_of_rt_rq(rt_rq));
#endif /* CONFIG_SMP */
#ifdef CONFIG_FAIR_GROUP_SCHED
if (rt_se_boosted(rt_se))
rt_rq->rt_nr_boosted--;
WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
#endif
}
static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
@ -303,7 +336,7 @@ static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
struct rt_prio_array *array = &rt_rq->active;
struct rt_rq *group_rq = group_rt_rq(rt_se);
if (group_rq && group_rq->rt_throttled)
if (group_rq && rt_rq_throttled(group_rq))
return;
list_add_tail(&rt_se->run_list, array->queue + rt_se_prio(rt_se));
@ -496,7 +529,7 @@ static struct task_struct *pick_next_task_rt(struct rq *rq)
if (unlikely(!rt_rq->rt_nr_running))
return NULL;
if (sched_rt_ratio_exceeded(rt_rq))
if (rt_rq_throttled(rt_rq))
return NULL;
do {