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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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![Peter Zijlstra](/assets/img/avatar_default.png)
Make the rt group scheduler compile time configurable. Keep it experimental for now. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
1220 lines
28 KiB
C
1220 lines
28 KiB
C
/*
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* Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
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* policies)
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*/
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#ifdef CONFIG_SMP
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static inline int rt_overloaded(struct rq *rq)
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{
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return atomic_read(&rq->rd->rto_count);
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}
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static inline void rt_set_overload(struct rq *rq)
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{
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cpu_set(rq->cpu, rq->rd->rto_mask);
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/*
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* Make sure the mask is visible before we set
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* the overload count. That is checked to determine
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* if we should look at the mask. It would be a shame
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* if we looked at the mask, but the mask was not
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* updated yet.
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*/
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wmb();
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atomic_inc(&rq->rd->rto_count);
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}
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static inline void rt_clear_overload(struct rq *rq)
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{
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/* the order here really doesn't matter */
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atomic_dec(&rq->rd->rto_count);
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cpu_clear(rq->cpu, rq->rd->rto_mask);
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}
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static void update_rt_migration(struct rq *rq)
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{
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if (rq->rt.rt_nr_migratory && (rq->rt.rt_nr_running > 1)) {
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if (!rq->rt.overloaded) {
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rt_set_overload(rq);
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rq->rt.overloaded = 1;
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}
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} else if (rq->rt.overloaded) {
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rt_clear_overload(rq);
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rq->rt.overloaded = 0;
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}
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}
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#endif /* CONFIG_SMP */
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static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
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{
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return container_of(rt_se, struct task_struct, rt);
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}
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static inline int on_rt_rq(struct sched_rt_entity *rt_se)
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{
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return !list_empty(&rt_se->run_list);
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}
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#ifdef CONFIG_RT_GROUP_SCHED
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static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
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{
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if (!rt_rq->tg)
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return RUNTIME_INF;
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return rt_rq->tg->rt_runtime;
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}
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#define for_each_leaf_rt_rq(rt_rq, rq) \
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list_for_each_entry(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
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static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
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{
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return rt_rq->rq;
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}
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static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
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{
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return rt_se->rt_rq;
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}
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#define for_each_sched_rt_entity(rt_se) \
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for (; rt_se; rt_se = rt_se->parent)
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static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
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{
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return rt_se->my_q;
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}
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static void enqueue_rt_entity(struct sched_rt_entity *rt_se);
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static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
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static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
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{
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struct sched_rt_entity *rt_se = rt_rq->rt_se;
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if (rt_se && !on_rt_rq(rt_se) && rt_rq->rt_nr_running) {
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struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
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enqueue_rt_entity(rt_se);
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if (rt_rq->highest_prio < curr->prio)
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resched_task(curr);
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}
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}
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static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
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{
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struct sched_rt_entity *rt_se = rt_rq->rt_se;
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if (rt_se && on_rt_rq(rt_se))
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dequeue_rt_entity(rt_se);
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}
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static inline int rt_rq_throttled(struct rt_rq *rt_rq)
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{
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return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
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}
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static int rt_se_boosted(struct sched_rt_entity *rt_se)
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{
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struct rt_rq *rt_rq = group_rt_rq(rt_se);
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struct task_struct *p;
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if (rt_rq)
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return !!rt_rq->rt_nr_boosted;
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p = rt_task_of(rt_se);
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return p->prio != p->normal_prio;
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}
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#else
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static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
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{
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if (sysctl_sched_rt_runtime == -1)
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return RUNTIME_INF;
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return (u64)sysctl_sched_rt_runtime * NSEC_PER_USEC;
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}
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#define for_each_leaf_rt_rq(rt_rq, rq) \
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for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
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static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
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{
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return container_of(rt_rq, struct rq, rt);
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}
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static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
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{
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struct task_struct *p = rt_task_of(rt_se);
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struct rq *rq = task_rq(p);
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return &rq->rt;
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}
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#define for_each_sched_rt_entity(rt_se) \
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for (; rt_se; rt_se = NULL)
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static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
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{
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return NULL;
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}
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static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
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{
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}
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static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
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{
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}
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static inline int rt_rq_throttled(struct rt_rq *rt_rq)
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{
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return rt_rq->rt_throttled;
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}
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#endif
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static inline int rt_se_prio(struct sched_rt_entity *rt_se)
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{
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#ifdef CONFIG_RT_GROUP_SCHED
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struct rt_rq *rt_rq = group_rt_rq(rt_se);
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if (rt_rq)
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return rt_rq->highest_prio;
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#endif
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return rt_task_of(rt_se)->prio;
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}
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static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
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{
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u64 runtime = sched_rt_runtime(rt_rq);
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if (runtime == RUNTIME_INF)
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return 0;
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if (rt_rq->rt_throttled)
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return rt_rq_throttled(rt_rq);
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if (rt_rq->rt_time > runtime) {
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struct rq *rq = rq_of_rt_rq(rt_rq);
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rq->rt_throttled = 1;
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rt_rq->rt_throttled = 1;
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if (rt_rq_throttled(rt_rq)) {
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sched_rt_rq_dequeue(rt_rq);
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return 1;
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}
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}
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return 0;
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}
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static void update_sched_rt_period(struct rq *rq)
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{
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struct rt_rq *rt_rq;
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u64 period;
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while (rq->clock > rq->rt_period_expire) {
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period = (u64)sysctl_sched_rt_period * NSEC_PER_USEC;
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rq->rt_period_expire += period;
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for_each_leaf_rt_rq(rt_rq, rq) {
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u64 runtime = sched_rt_runtime(rt_rq);
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rt_rq->rt_time -= min(rt_rq->rt_time, runtime);
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if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
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rt_rq->rt_throttled = 0;
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sched_rt_rq_enqueue(rt_rq);
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}
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}
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rq->rt_throttled = 0;
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}
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}
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/*
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* Update the current task's runtime statistics. Skip current tasks that
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* are not in our scheduling class.
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*/
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static void update_curr_rt(struct rq *rq)
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{
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struct task_struct *curr = rq->curr;
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struct sched_rt_entity *rt_se = &curr->rt;
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struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
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u64 delta_exec;
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if (!task_has_rt_policy(curr))
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return;
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delta_exec = rq->clock - curr->se.exec_start;
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if (unlikely((s64)delta_exec < 0))
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delta_exec = 0;
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schedstat_set(curr->se.exec_max, max(curr->se.exec_max, delta_exec));
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curr->se.sum_exec_runtime += delta_exec;
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curr->se.exec_start = rq->clock;
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cpuacct_charge(curr, delta_exec);
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rt_rq->rt_time += delta_exec;
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if (sched_rt_runtime_exceeded(rt_rq))
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resched_task(curr);
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}
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static inline
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void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
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{
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WARN_ON(!rt_prio(rt_se_prio(rt_se)));
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rt_rq->rt_nr_running++;
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#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
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if (rt_se_prio(rt_se) < rt_rq->highest_prio)
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rt_rq->highest_prio = rt_se_prio(rt_se);
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#endif
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#ifdef CONFIG_SMP
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if (rt_se->nr_cpus_allowed > 1) {
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struct rq *rq = rq_of_rt_rq(rt_rq);
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rq->rt.rt_nr_migratory++;
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}
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update_rt_migration(rq_of_rt_rq(rt_rq));
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#endif
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#ifdef CONFIG_RT_GROUP_SCHED
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if (rt_se_boosted(rt_se))
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rt_rq->rt_nr_boosted++;
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#endif
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}
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static inline
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void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
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{
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WARN_ON(!rt_prio(rt_se_prio(rt_se)));
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WARN_ON(!rt_rq->rt_nr_running);
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rt_rq->rt_nr_running--;
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#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
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if (rt_rq->rt_nr_running) {
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struct rt_prio_array *array;
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WARN_ON(rt_se_prio(rt_se) < rt_rq->highest_prio);
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if (rt_se_prio(rt_se) == rt_rq->highest_prio) {
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/* recalculate */
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array = &rt_rq->active;
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rt_rq->highest_prio =
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sched_find_first_bit(array->bitmap);
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} /* otherwise leave rq->highest prio alone */
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} else
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rt_rq->highest_prio = MAX_RT_PRIO;
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#endif
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#ifdef CONFIG_SMP
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if (rt_se->nr_cpus_allowed > 1) {
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struct rq *rq = rq_of_rt_rq(rt_rq);
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rq->rt.rt_nr_migratory--;
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}
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update_rt_migration(rq_of_rt_rq(rt_rq));
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#endif /* CONFIG_SMP */
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#ifdef CONFIG_RT_GROUP_SCHED
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if (rt_se_boosted(rt_se))
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rt_rq->rt_nr_boosted--;
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WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
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#endif
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}
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static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
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{
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struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
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struct rt_prio_array *array = &rt_rq->active;
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struct rt_rq *group_rq = group_rt_rq(rt_se);
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if (group_rq && rt_rq_throttled(group_rq))
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return;
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list_add_tail(&rt_se->run_list, array->queue + rt_se_prio(rt_se));
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__set_bit(rt_se_prio(rt_se), array->bitmap);
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inc_rt_tasks(rt_se, rt_rq);
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}
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static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
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{
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struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
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struct rt_prio_array *array = &rt_rq->active;
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list_del_init(&rt_se->run_list);
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if (list_empty(array->queue + rt_se_prio(rt_se)))
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__clear_bit(rt_se_prio(rt_se), array->bitmap);
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dec_rt_tasks(rt_se, rt_rq);
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}
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/*
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* Because the prio of an upper entry depends on the lower
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* entries, we must remove entries top - down.
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*
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* XXX: O(1/2 h^2) because we can only walk up, not down the chain.
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* doesn't matter much for now, as h=2 for GROUP_SCHED.
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*/
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static void dequeue_rt_stack(struct task_struct *p)
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{
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struct sched_rt_entity *rt_se, *top_se;
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/*
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* dequeue all, top - down.
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*/
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do {
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rt_se = &p->rt;
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top_se = NULL;
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for_each_sched_rt_entity(rt_se) {
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if (on_rt_rq(rt_se))
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top_se = rt_se;
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}
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if (top_se)
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dequeue_rt_entity(top_se);
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} while (top_se);
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}
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/*
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* Adding/removing a task to/from a priority array:
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*/
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static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
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{
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struct sched_rt_entity *rt_se = &p->rt;
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if (wakeup)
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rt_se->timeout = 0;
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dequeue_rt_stack(p);
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/*
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* enqueue everybody, bottom - up.
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*/
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for_each_sched_rt_entity(rt_se)
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enqueue_rt_entity(rt_se);
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inc_cpu_load(rq, p->se.load.weight);
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}
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static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
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{
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struct sched_rt_entity *rt_se = &p->rt;
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struct rt_rq *rt_rq;
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update_curr_rt(rq);
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dequeue_rt_stack(p);
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/*
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* re-enqueue all non-empty rt_rq entities.
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*/
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for_each_sched_rt_entity(rt_se) {
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rt_rq = group_rt_rq(rt_se);
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if (rt_rq && rt_rq->rt_nr_running)
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enqueue_rt_entity(rt_se);
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}
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dec_cpu_load(rq, p->se.load.weight);
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}
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/*
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* Put task to the end of the run list without the overhead of dequeue
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* followed by enqueue.
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*/
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static
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void requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
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{
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struct rt_prio_array *array = &rt_rq->active;
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list_move_tail(&rt_se->run_list, array->queue + rt_se_prio(rt_se));
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}
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static void requeue_task_rt(struct rq *rq, struct task_struct *p)
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{
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struct sched_rt_entity *rt_se = &p->rt;
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struct rt_rq *rt_rq;
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for_each_sched_rt_entity(rt_se) {
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rt_rq = rt_rq_of_se(rt_se);
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requeue_rt_entity(rt_rq, rt_se);
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}
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}
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static void yield_task_rt(struct rq *rq)
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{
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requeue_task_rt(rq, rq->curr);
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}
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#ifdef CONFIG_SMP
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static int find_lowest_rq(struct task_struct *task);
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static int select_task_rq_rt(struct task_struct *p, int sync)
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{
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struct rq *rq = task_rq(p);
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/*
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* If the current task is an RT task, then
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* try to see if we can wake this RT task up on another
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* runqueue. Otherwise simply start this RT task
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* on its current runqueue.
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*
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* We want to avoid overloading runqueues. Even if
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* the RT task is of higher priority than the current RT task.
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* RT tasks behave differently than other tasks. If
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* one gets preempted, we try to push it off to another queue.
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* So trying to keep a preempting RT task on the same
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* cache hot CPU will force the running RT task to
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* a cold CPU. So we waste all the cache for the lower
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* RT task in hopes of saving some of a RT task
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* that is just being woken and probably will have
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* cold cache anyway.
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*/
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if (unlikely(rt_task(rq->curr)) &&
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(p->rt.nr_cpus_allowed > 1)) {
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int cpu = find_lowest_rq(p);
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return (cpu == -1) ? task_cpu(p) : cpu;
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}
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/*
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* Otherwise, just let it ride on the affined RQ and the
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* post-schedule router will push the preempted task away
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*/
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return task_cpu(p);
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}
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#endif /* CONFIG_SMP */
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|
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/*
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* Preempt the current task with a newly woken task if needed:
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*/
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static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p)
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{
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if (p->prio < rq->curr->prio)
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resched_task(rq->curr);
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}
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static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
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struct rt_rq *rt_rq)
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{
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struct rt_prio_array *array = &rt_rq->active;
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struct sched_rt_entity *next = NULL;
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struct list_head *queue;
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int idx;
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idx = sched_find_first_bit(array->bitmap);
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BUG_ON(idx >= MAX_RT_PRIO);
|
|
|
|
queue = array->queue + idx;
|
|
next = list_entry(queue->next, struct sched_rt_entity, run_list);
|
|
|
|
return next;
|
|
}
|
|
|
|
static struct task_struct *pick_next_task_rt(struct rq *rq)
|
|
{
|
|
struct sched_rt_entity *rt_se;
|
|
struct task_struct *p;
|
|
struct rt_rq *rt_rq;
|
|
|
|
rt_rq = &rq->rt;
|
|
|
|
if (unlikely(!rt_rq->rt_nr_running))
|
|
return NULL;
|
|
|
|
if (rt_rq_throttled(rt_rq))
|
|
return NULL;
|
|
|
|
do {
|
|
rt_se = pick_next_rt_entity(rq, rt_rq);
|
|
BUG_ON(!rt_se);
|
|
rt_rq = group_rt_rq(rt_se);
|
|
} while (rt_rq);
|
|
|
|
p = rt_task_of(rt_se);
|
|
p->se.exec_start = rq->clock;
|
|
return p;
|
|
}
|
|
|
|
static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
|
|
{
|
|
update_curr_rt(rq);
|
|
p->se.exec_start = 0;
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
/* Only try algorithms three times */
|
|
#define RT_MAX_TRIES 3
|
|
|
|
static int double_lock_balance(struct rq *this_rq, struct rq *busiest);
|
|
static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
|
|
|
|
static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
|
|
{
|
|
if (!task_running(rq, p) &&
|
|
(cpu < 0 || cpu_isset(cpu, p->cpus_allowed)) &&
|
|
(p->rt.nr_cpus_allowed > 1))
|
|
return 1;
|
|
return 0;
|
|
}
|
|
|
|
/* Return the second highest RT task, NULL otherwise */
|
|
static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
|
|
{
|
|
struct task_struct *next = NULL;
|
|
struct sched_rt_entity *rt_se;
|
|
struct rt_prio_array *array;
|
|
struct rt_rq *rt_rq;
|
|
int idx;
|
|
|
|
for_each_leaf_rt_rq(rt_rq, rq) {
|
|
array = &rt_rq->active;
|
|
idx = sched_find_first_bit(array->bitmap);
|
|
next_idx:
|
|
if (idx >= MAX_RT_PRIO)
|
|
continue;
|
|
if (next && next->prio < idx)
|
|
continue;
|
|
list_for_each_entry(rt_se, array->queue + idx, run_list) {
|
|
struct task_struct *p = rt_task_of(rt_se);
|
|
if (pick_rt_task(rq, p, cpu)) {
|
|
next = p;
|
|
break;
|
|
}
|
|
}
|
|
if (!next) {
|
|
idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
|
|
goto next_idx;
|
|
}
|
|
}
|
|
|
|
return next;
|
|
}
|
|
|
|
static DEFINE_PER_CPU(cpumask_t, local_cpu_mask);
|
|
|
|
static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask)
|
|
{
|
|
int lowest_prio = -1;
|
|
int lowest_cpu = -1;
|
|
int count = 0;
|
|
int cpu;
|
|
|
|
cpus_and(*lowest_mask, task_rq(task)->rd->online, task->cpus_allowed);
|
|
|
|
/*
|
|
* Scan each rq for the lowest prio.
|
|
*/
|
|
for_each_cpu_mask(cpu, *lowest_mask) {
|
|
struct rq *rq = cpu_rq(cpu);
|
|
|
|
/* We look for lowest RT prio or non-rt CPU */
|
|
if (rq->rt.highest_prio >= MAX_RT_PRIO) {
|
|
/*
|
|
* if we already found a low RT queue
|
|
* and now we found this non-rt queue
|
|
* clear the mask and set our bit.
|
|
* Otherwise just return the queue as is
|
|
* and the count==1 will cause the algorithm
|
|
* to use the first bit found.
|
|
*/
|
|
if (lowest_cpu != -1) {
|
|
cpus_clear(*lowest_mask);
|
|
cpu_set(rq->cpu, *lowest_mask);
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
/* no locking for now */
|
|
if ((rq->rt.highest_prio > task->prio)
|
|
&& (rq->rt.highest_prio >= lowest_prio)) {
|
|
if (rq->rt.highest_prio > lowest_prio) {
|
|
/* new low - clear old data */
|
|
lowest_prio = rq->rt.highest_prio;
|
|
lowest_cpu = cpu;
|
|
count = 0;
|
|
}
|
|
count++;
|
|
} else
|
|
cpu_clear(cpu, *lowest_mask);
|
|
}
|
|
|
|
/*
|
|
* Clear out all the set bits that represent
|
|
* runqueues that were of higher prio than
|
|
* the lowest_prio.
|
|
*/
|
|
if (lowest_cpu > 0) {
|
|
/*
|
|
* Perhaps we could add another cpumask op to
|
|
* zero out bits. Like cpu_zero_bits(cpumask, nrbits);
|
|
* Then that could be optimized to use memset and such.
|
|
*/
|
|
for_each_cpu_mask(cpu, *lowest_mask) {
|
|
if (cpu >= lowest_cpu)
|
|
break;
|
|
cpu_clear(cpu, *lowest_mask);
|
|
}
|
|
}
|
|
|
|
return count;
|
|
}
|
|
|
|
static inline int pick_optimal_cpu(int this_cpu, cpumask_t *mask)
|
|
{
|
|
int first;
|
|
|
|
/* "this_cpu" is cheaper to preempt than a remote processor */
|
|
if ((this_cpu != -1) && cpu_isset(this_cpu, *mask))
|
|
return this_cpu;
|
|
|
|
first = first_cpu(*mask);
|
|
if (first != NR_CPUS)
|
|
return first;
|
|
|
|
return -1;
|
|
}
|
|
|
|
static int find_lowest_rq(struct task_struct *task)
|
|
{
|
|
struct sched_domain *sd;
|
|
cpumask_t *lowest_mask = &__get_cpu_var(local_cpu_mask);
|
|
int this_cpu = smp_processor_id();
|
|
int cpu = task_cpu(task);
|
|
int count = find_lowest_cpus(task, lowest_mask);
|
|
|
|
if (!count)
|
|
return -1; /* No targets found */
|
|
|
|
/*
|
|
* There is no sense in performing an optimal search if only one
|
|
* target is found.
|
|
*/
|
|
if (count == 1)
|
|
return first_cpu(*lowest_mask);
|
|
|
|
/*
|
|
* At this point we have built a mask of cpus representing the
|
|
* lowest priority tasks in the system. Now we want to elect
|
|
* the best one based on our affinity and topology.
|
|
*
|
|
* We prioritize the last cpu that the task executed on since
|
|
* it is most likely cache-hot in that location.
|
|
*/
|
|
if (cpu_isset(cpu, *lowest_mask))
|
|
return cpu;
|
|
|
|
/*
|
|
* Otherwise, we consult the sched_domains span maps to figure
|
|
* out which cpu is logically closest to our hot cache data.
|
|
*/
|
|
if (this_cpu == cpu)
|
|
this_cpu = -1; /* Skip this_cpu opt if the same */
|
|
|
|
for_each_domain(cpu, sd) {
|
|
if (sd->flags & SD_WAKE_AFFINE) {
|
|
cpumask_t domain_mask;
|
|
int best_cpu;
|
|
|
|
cpus_and(domain_mask, sd->span, *lowest_mask);
|
|
|
|
best_cpu = pick_optimal_cpu(this_cpu,
|
|
&domain_mask);
|
|
if (best_cpu != -1)
|
|
return best_cpu;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* And finally, if there were no matches within the domains
|
|
* just give the caller *something* to work with from the compatible
|
|
* locations.
|
|
*/
|
|
return pick_optimal_cpu(this_cpu, lowest_mask);
|
|
}
|
|
|
|
/* Will lock the rq it finds */
|
|
static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
|
|
{
|
|
struct rq *lowest_rq = NULL;
|
|
int tries;
|
|
int cpu;
|
|
|
|
for (tries = 0; tries < RT_MAX_TRIES; tries++) {
|
|
cpu = find_lowest_rq(task);
|
|
|
|
if ((cpu == -1) || (cpu == rq->cpu))
|
|
break;
|
|
|
|
lowest_rq = cpu_rq(cpu);
|
|
|
|
/* if the prio of this runqueue changed, try again */
|
|
if (double_lock_balance(rq, lowest_rq)) {
|
|
/*
|
|
* We had to unlock the run queue. In
|
|
* the mean time, task could have
|
|
* migrated already or had its affinity changed.
|
|
* Also make sure that it wasn't scheduled on its rq.
|
|
*/
|
|
if (unlikely(task_rq(task) != rq ||
|
|
!cpu_isset(lowest_rq->cpu,
|
|
task->cpus_allowed) ||
|
|
task_running(rq, task) ||
|
|
!task->se.on_rq)) {
|
|
|
|
spin_unlock(&lowest_rq->lock);
|
|
lowest_rq = NULL;
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* If this rq is still suitable use it. */
|
|
if (lowest_rq->rt.highest_prio > task->prio)
|
|
break;
|
|
|
|
/* try again */
|
|
spin_unlock(&lowest_rq->lock);
|
|
lowest_rq = NULL;
|
|
}
|
|
|
|
return lowest_rq;
|
|
}
|
|
|
|
/*
|
|
* If the current CPU has more than one RT task, see if the non
|
|
* running task can migrate over to a CPU that is running a task
|
|
* of lesser priority.
|
|
*/
|
|
static int push_rt_task(struct rq *rq)
|
|
{
|
|
struct task_struct *next_task;
|
|
struct rq *lowest_rq;
|
|
int ret = 0;
|
|
int paranoid = RT_MAX_TRIES;
|
|
|
|
if (!rq->rt.overloaded)
|
|
return 0;
|
|
|
|
next_task = pick_next_highest_task_rt(rq, -1);
|
|
if (!next_task)
|
|
return 0;
|
|
|
|
retry:
|
|
if (unlikely(next_task == rq->curr)) {
|
|
WARN_ON(1);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* It's possible that the next_task slipped in of
|
|
* higher priority than current. If that's the case
|
|
* just reschedule current.
|
|
*/
|
|
if (unlikely(next_task->prio < rq->curr->prio)) {
|
|
resched_task(rq->curr);
|
|
return 0;
|
|
}
|
|
|
|
/* We might release rq lock */
|
|
get_task_struct(next_task);
|
|
|
|
/* find_lock_lowest_rq locks the rq if found */
|
|
lowest_rq = find_lock_lowest_rq(next_task, rq);
|
|
if (!lowest_rq) {
|
|
struct task_struct *task;
|
|
/*
|
|
* find lock_lowest_rq releases rq->lock
|
|
* so it is possible that next_task has changed.
|
|
* If it has, then try again.
|
|
*/
|
|
task = pick_next_highest_task_rt(rq, -1);
|
|
if (unlikely(task != next_task) && task && paranoid--) {
|
|
put_task_struct(next_task);
|
|
next_task = task;
|
|
goto retry;
|
|
}
|
|
goto out;
|
|
}
|
|
|
|
deactivate_task(rq, next_task, 0);
|
|
set_task_cpu(next_task, lowest_rq->cpu);
|
|
activate_task(lowest_rq, next_task, 0);
|
|
|
|
resched_task(lowest_rq->curr);
|
|
|
|
spin_unlock(&lowest_rq->lock);
|
|
|
|
ret = 1;
|
|
out:
|
|
put_task_struct(next_task);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* TODO: Currently we just use the second highest prio task on
|
|
* the queue, and stop when it can't migrate (or there's
|
|
* no more RT tasks). There may be a case where a lower
|
|
* priority RT task has a different affinity than the
|
|
* higher RT task. In this case the lower RT task could
|
|
* possibly be able to migrate where as the higher priority
|
|
* RT task could not. We currently ignore this issue.
|
|
* Enhancements are welcome!
|
|
*/
|
|
static void push_rt_tasks(struct rq *rq)
|
|
{
|
|
/* push_rt_task will return true if it moved an RT */
|
|
while (push_rt_task(rq))
|
|
;
|
|
}
|
|
|
|
static int pull_rt_task(struct rq *this_rq)
|
|
{
|
|
int this_cpu = this_rq->cpu, ret = 0, cpu;
|
|
struct task_struct *p, *next;
|
|
struct rq *src_rq;
|
|
|
|
if (likely(!rt_overloaded(this_rq)))
|
|
return 0;
|
|
|
|
next = pick_next_task_rt(this_rq);
|
|
|
|
for_each_cpu_mask(cpu, this_rq->rd->rto_mask) {
|
|
if (this_cpu == cpu)
|
|
continue;
|
|
|
|
src_rq = cpu_rq(cpu);
|
|
/*
|
|
* We can potentially drop this_rq's lock in
|
|
* double_lock_balance, and another CPU could
|
|
* steal our next task - hence we must cause
|
|
* the caller to recalculate the next task
|
|
* in that case:
|
|
*/
|
|
if (double_lock_balance(this_rq, src_rq)) {
|
|
struct task_struct *old_next = next;
|
|
|
|
next = pick_next_task_rt(this_rq);
|
|
if (next != old_next)
|
|
ret = 1;
|
|
}
|
|
|
|
/*
|
|
* Are there still pullable RT tasks?
|
|
*/
|
|
if (src_rq->rt.rt_nr_running <= 1)
|
|
goto skip;
|
|
|
|
p = pick_next_highest_task_rt(src_rq, this_cpu);
|
|
|
|
/*
|
|
* Do we have an RT task that preempts
|
|
* the to-be-scheduled task?
|
|
*/
|
|
if (p && (!next || (p->prio < next->prio))) {
|
|
WARN_ON(p == src_rq->curr);
|
|
WARN_ON(!p->se.on_rq);
|
|
|
|
/*
|
|
* There's a chance that p is higher in priority
|
|
* than what's currently running on its cpu.
|
|
* This is just that p is wakeing up and hasn't
|
|
* had a chance to schedule. We only pull
|
|
* p if it is lower in priority than the
|
|
* current task on the run queue or
|
|
* this_rq next task is lower in prio than
|
|
* the current task on that rq.
|
|
*/
|
|
if (p->prio < src_rq->curr->prio ||
|
|
(next && next->prio < src_rq->curr->prio))
|
|
goto skip;
|
|
|
|
ret = 1;
|
|
|
|
deactivate_task(src_rq, p, 0);
|
|
set_task_cpu(p, this_cpu);
|
|
activate_task(this_rq, p, 0);
|
|
/*
|
|
* We continue with the search, just in
|
|
* case there's an even higher prio task
|
|
* in another runqueue. (low likelyhood
|
|
* but possible)
|
|
*
|
|
* Update next so that we won't pick a task
|
|
* on another cpu with a priority lower (or equal)
|
|
* than the one we just picked.
|
|
*/
|
|
next = p;
|
|
|
|
}
|
|
skip:
|
|
spin_unlock(&src_rq->lock);
|
|
}
|
|
|
|
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 (unlikely(rt_task(prev)) && rq->rt.highest_prio > prev->prio)
|
|
pull_rt_task(rq);
|
|
}
|
|
|
|
static void post_schedule_rt(struct rq *rq)
|
|
{
|
|
/*
|
|
* If we have more than one rt_task queued, then
|
|
* see if we can push the other rt_tasks off to other CPUS.
|
|
* Note we may release the rq lock, and since
|
|
* the lock was owned by prev, we need to release it
|
|
* first via finish_lock_switch and then reaquire it here.
|
|
*/
|
|
if (unlikely(rq->rt.overloaded)) {
|
|
spin_lock_irq(&rq->lock);
|
|
push_rt_tasks(rq);
|
|
spin_unlock_irq(&rq->lock);
|
|
}
|
|
}
|
|
|
|
|
|
static void task_wake_up_rt(struct rq *rq, struct task_struct *p)
|
|
{
|
|
if (!task_running(rq, p) &&
|
|
(p->prio >= rq->rt.highest_prio) &&
|
|
rq->rt.overloaded)
|
|
push_rt_tasks(rq);
|
|
}
|
|
|
|
static unsigned long
|
|
load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
|
|
unsigned long max_load_move,
|
|
struct sched_domain *sd, enum cpu_idle_type idle,
|
|
int *all_pinned, int *this_best_prio)
|
|
{
|
|
/* don't touch RT tasks */
|
|
return 0;
|
|
}
|
|
|
|
static int
|
|
move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
|
|
struct sched_domain *sd, enum cpu_idle_type idle)
|
|
{
|
|
/* don't touch RT tasks */
|
|
return 0;
|
|
}
|
|
|
|
static void set_cpus_allowed_rt(struct task_struct *p, cpumask_t *new_mask)
|
|
{
|
|
int weight = cpus_weight(*new_mask);
|
|
|
|
BUG_ON(!rt_task(p));
|
|
|
|
/*
|
|
* Update the migration status of the RQ if we have an RT task
|
|
* which is running AND changing its weight value.
|
|
*/
|
|
if (p->se.on_rq && (weight != p->rt.nr_cpus_allowed)) {
|
|
struct rq *rq = task_rq(p);
|
|
|
|
if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
|
|
rq->rt.rt_nr_migratory++;
|
|
} else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
|
|
BUG_ON(!rq->rt.rt_nr_migratory);
|
|
rq->rt.rt_nr_migratory--;
|
|
}
|
|
|
|
update_rt_migration(rq);
|
|
}
|
|
|
|
p->cpus_allowed = *new_mask;
|
|
p->rt.nr_cpus_allowed = weight;
|
|
}
|
|
|
|
/* Assumes rq->lock is held */
|
|
static void join_domain_rt(struct rq *rq)
|
|
{
|
|
if (rq->rt.overloaded)
|
|
rt_set_overload(rq);
|
|
}
|
|
|
|
/* Assumes rq->lock is held */
|
|
static void leave_domain_rt(struct rq *rq)
|
|
{
|
|
if (rq->rt.overloaded)
|
|
rt_clear_overload(rq);
|
|
}
|
|
|
|
/*
|
|
* When switch from the rt queue, we bring ourselves to a position
|
|
* that we might want to pull RT tasks from other runqueues.
|
|
*/
|
|
static void switched_from_rt(struct rq *rq, struct task_struct *p,
|
|
int running)
|
|
{
|
|
/*
|
|
* If there are other RT tasks then we will reschedule
|
|
* and the scheduling of the other RT tasks will handle
|
|
* the balancing. But if we are the last RT task
|
|
* we may need to handle the pulling of RT tasks
|
|
* now.
|
|
*/
|
|
if (!rq->rt.rt_nr_running)
|
|
pull_rt_task(rq);
|
|
}
|
|
#endif /* CONFIG_SMP */
|
|
|
|
/*
|
|
* When switching a task to RT, we may overload the runqueue
|
|
* with RT tasks. In this case we try to push them off to
|
|
* other runqueues.
|
|
*/
|
|
static void switched_to_rt(struct rq *rq, struct task_struct *p,
|
|
int running)
|
|
{
|
|
int check_resched = 1;
|
|
|
|
/*
|
|
* If we are already running, then there's nothing
|
|
* that needs to be done. But if we are not running
|
|
* we may need to preempt the current running task.
|
|
* If that current running task is also an RT task
|
|
* then see if we can move to another run queue.
|
|
*/
|
|
if (!running) {
|
|
#ifdef CONFIG_SMP
|
|
if (rq->rt.overloaded && push_rt_task(rq) &&
|
|
/* Don't resched if we changed runqueues */
|
|
rq != task_rq(p))
|
|
check_resched = 0;
|
|
#endif /* CONFIG_SMP */
|
|
if (check_resched && p->prio < rq->curr->prio)
|
|
resched_task(rq->curr);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Priority of the task has changed. This may cause
|
|
* us to initiate a push or pull.
|
|
*/
|
|
static void prio_changed_rt(struct rq *rq, struct task_struct *p,
|
|
int oldprio, int running)
|
|
{
|
|
if (running) {
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* If our priority decreases while running, we
|
|
* may need to pull tasks to this runqueue.
|
|
*/
|
|
if (oldprio < p->prio)
|
|
pull_rt_task(rq);
|
|
/*
|
|
* If there's a higher priority task waiting to run
|
|
* then reschedule.
|
|
*/
|
|
if (p->prio > rq->rt.highest_prio)
|
|
resched_task(p);
|
|
#else
|
|
/* For UP simply resched on drop of prio */
|
|
if (oldprio < p->prio)
|
|
resched_task(p);
|
|
#endif /* CONFIG_SMP */
|
|
} else {
|
|
/*
|
|
* This task is not running, but if it is
|
|
* greater than the current running task
|
|
* then reschedule.
|
|
*/
|
|
if (p->prio < rq->curr->prio)
|
|
resched_task(rq->curr);
|
|
}
|
|
}
|
|
|
|
static void watchdog(struct rq *rq, struct task_struct *p)
|
|
{
|
|
unsigned long soft, hard;
|
|
|
|
if (!p->signal)
|
|
return;
|
|
|
|
soft = p->signal->rlim[RLIMIT_RTTIME].rlim_cur;
|
|
hard = p->signal->rlim[RLIMIT_RTTIME].rlim_max;
|
|
|
|
if (soft != RLIM_INFINITY) {
|
|
unsigned long next;
|
|
|
|
p->rt.timeout++;
|
|
next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
|
|
if (p->rt.timeout > next)
|
|
p->it_sched_expires = p->se.sum_exec_runtime;
|
|
}
|
|
}
|
|
|
|
static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
|
|
{
|
|
update_curr_rt(rq);
|
|
|
|
watchdog(rq, p);
|
|
|
|
/*
|
|
* RR tasks need a special form of timeslice management.
|
|
* FIFO tasks have no timeslices.
|
|
*/
|
|
if (p->policy != SCHED_RR)
|
|
return;
|
|
|
|
if (--p->rt.time_slice)
|
|
return;
|
|
|
|
p->rt.time_slice = DEF_TIMESLICE;
|
|
|
|
/*
|
|
* Requeue to the end of queue if we are not the only element
|
|
* on the queue:
|
|
*/
|
|
if (p->rt.run_list.prev != p->rt.run_list.next) {
|
|
requeue_task_rt(rq, p);
|
|
set_tsk_need_resched(p);
|
|
}
|
|
}
|
|
|
|
static void set_curr_task_rt(struct rq *rq)
|
|
{
|
|
struct task_struct *p = rq->curr;
|
|
|
|
p->se.exec_start = rq->clock;
|
|
}
|
|
|
|
const struct sched_class rt_sched_class = {
|
|
.next = &fair_sched_class,
|
|
.enqueue_task = enqueue_task_rt,
|
|
.dequeue_task = dequeue_task_rt,
|
|
.yield_task = yield_task_rt,
|
|
#ifdef CONFIG_SMP
|
|
.select_task_rq = select_task_rq_rt,
|
|
#endif /* CONFIG_SMP */
|
|
|
|
.check_preempt_curr = check_preempt_curr_rt,
|
|
|
|
.pick_next_task = pick_next_task_rt,
|
|
.put_prev_task = put_prev_task_rt,
|
|
|
|
#ifdef CONFIG_SMP
|
|
.load_balance = load_balance_rt,
|
|
.move_one_task = move_one_task_rt,
|
|
.set_cpus_allowed = set_cpus_allowed_rt,
|
|
.join_domain = join_domain_rt,
|
|
.leave_domain = leave_domain_rt,
|
|
.pre_schedule = pre_schedule_rt,
|
|
.post_schedule = post_schedule_rt,
|
|
.task_wake_up = task_wake_up_rt,
|
|
.switched_from = switched_from_rt,
|
|
#endif
|
|
|
|
.set_curr_task = set_curr_task_rt,
|
|
.task_tick = task_tick_rt,
|
|
|
|
.prio_changed = prio_changed_rt,
|
|
.switched_to = switched_to_rt,
|
|
};
|