From 23b0fdfc9299b137bd126e9dc22f62a59dae546d Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 13 Feb 2008 15:45:39 +0100 Subject: sched: rt-group: deal with PI 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 Signed-off-by: Ingo Molnar --- kernel/sched.c | 3 +++ kernel/sched_rt.c | 43 ++++++++++++++++++++++++++++++++++++++----- 2 files changed, 41 insertions(+), 5 deletions(-) (limited to 'kernel') diff --git a/kernel/sched.c b/kernel/sched.c index 88a17c7128c..cecaea67ae9 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -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 } diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index 274b40d7bef..8d426938123 100644 --- a/kernel/sched_rt.c +++ b/kernel/sched_rt.c @@ -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 { -- cgit v1.2.3-70-g09d2