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1baca4ce16
Introduces data structures relevant for implementing dynamic migration of -deadline tasks and the logic for checking if runqueues are overloaded with -deadline tasks and for choosing where a task should migrate, when it is the case. Adds also dynamic migrations to SCHED_DEADLINE, so that tasks can be moved among CPUs when necessary. It is also possible to bind a task to a (set of) CPU(s), thus restricting its capability of migrating, or forbidding migrations at all. The very same approach used in sched_rt is utilised: - -deadline tasks are kept into CPU-specific runqueues, - -deadline tasks are migrated among runqueues to achieve the following: * on an M-CPU system the M earliest deadline ready tasks are always running; * affinity/cpusets settings of all the -deadline tasks is always respected. Therefore, this very special form of "load balancing" is done with an active method, i.e., the scheduler pushes or pulls tasks between runqueues when they are woken up and/or (de)scheduled. IOW, every time a preemption occurs, the descheduled task might be sent to some other CPU (depending on its deadline) to continue executing (push). On the other hand, every time a CPU becomes idle, it might pull the second earliest deadline ready task from some other CPU. To enforce this, a pull operation is always attempted before taking any scheduling decision (pre_schedule()), as well as a push one after each scheduling decision (post_schedule()). In addition, when a task arrives or wakes up, the best CPU where to resume it is selected taking into account its affinity mask, the system topology, but also its deadline. E.g., from the scheduling point of view, the best CPU where to wake up (and also where to push) a task is the one which is running the task with the latest deadline among the M executing ones. In order to facilitate these decisions, per-runqueue "caching" of the deadlines of the currently running and of the first ready task is used. Queued but not running tasks are also parked in another rb-tree to speed-up pushes. Signed-off-by: Juri Lelli <juri.lelli@gmail.com> Signed-off-by: Dario Faggioli <raistlin@linux.it> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1383831828-15501-5-git-send-email-juri.lelli@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2031 lines
46 KiB
C
2031 lines
46 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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#include "sched.h"
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#include <linux/slab.h>
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int sched_rr_timeslice = RR_TIMESLICE;
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static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);
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struct rt_bandwidth def_rt_bandwidth;
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static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer)
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{
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struct rt_bandwidth *rt_b =
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container_of(timer, struct rt_bandwidth, rt_period_timer);
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ktime_t now;
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int overrun;
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int idle = 0;
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for (;;) {
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now = hrtimer_cb_get_time(timer);
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overrun = hrtimer_forward(timer, now, rt_b->rt_period);
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if (!overrun)
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break;
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idle = do_sched_rt_period_timer(rt_b, overrun);
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}
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return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
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}
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void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime)
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{
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rt_b->rt_period = ns_to_ktime(period);
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rt_b->rt_runtime = runtime;
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raw_spin_lock_init(&rt_b->rt_runtime_lock);
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hrtimer_init(&rt_b->rt_period_timer,
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CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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rt_b->rt_period_timer.function = sched_rt_period_timer;
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}
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static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
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{
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if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
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return;
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if (hrtimer_active(&rt_b->rt_period_timer))
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return;
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raw_spin_lock(&rt_b->rt_runtime_lock);
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start_bandwidth_timer(&rt_b->rt_period_timer, rt_b->rt_period);
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raw_spin_unlock(&rt_b->rt_runtime_lock);
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}
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void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq)
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{
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struct rt_prio_array *array;
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int i;
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array = &rt_rq->active;
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for (i = 0; i < MAX_RT_PRIO; i++) {
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INIT_LIST_HEAD(array->queue + i);
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__clear_bit(i, array->bitmap);
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}
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/* delimiter for bitsearch: */
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__set_bit(MAX_RT_PRIO, array->bitmap);
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#if defined CONFIG_SMP
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rt_rq->highest_prio.curr = MAX_RT_PRIO;
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rt_rq->highest_prio.next = MAX_RT_PRIO;
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rt_rq->rt_nr_migratory = 0;
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rt_rq->overloaded = 0;
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plist_head_init(&rt_rq->pushable_tasks);
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#endif
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rt_rq->rt_time = 0;
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rt_rq->rt_throttled = 0;
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rt_rq->rt_runtime = 0;
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raw_spin_lock_init(&rt_rq->rt_runtime_lock);
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}
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#ifdef CONFIG_RT_GROUP_SCHED
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static void destroy_rt_bandwidth(struct rt_bandwidth *rt_b)
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{
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hrtimer_cancel(&rt_b->rt_period_timer);
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}
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#define rt_entity_is_task(rt_se) (!(rt_se)->my_q)
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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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#ifdef CONFIG_SCHED_DEBUG
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WARN_ON_ONCE(!rt_entity_is_task(rt_se));
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#endif
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return container_of(rt_se, struct task_struct, rt);
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}
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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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void free_rt_sched_group(struct task_group *tg)
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{
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int i;
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if (tg->rt_se)
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destroy_rt_bandwidth(&tg->rt_bandwidth);
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for_each_possible_cpu(i) {
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if (tg->rt_rq)
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kfree(tg->rt_rq[i]);
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if (tg->rt_se)
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kfree(tg->rt_se[i]);
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}
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kfree(tg->rt_rq);
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kfree(tg->rt_se);
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}
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void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
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struct sched_rt_entity *rt_se, int cpu,
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struct sched_rt_entity *parent)
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{
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struct rq *rq = cpu_rq(cpu);
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rt_rq->highest_prio.curr = MAX_RT_PRIO;
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rt_rq->rt_nr_boosted = 0;
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rt_rq->rq = rq;
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rt_rq->tg = tg;
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tg->rt_rq[cpu] = rt_rq;
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tg->rt_se[cpu] = rt_se;
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if (!rt_se)
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return;
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if (!parent)
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rt_se->rt_rq = &rq->rt;
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else
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rt_se->rt_rq = parent->my_q;
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rt_se->my_q = rt_rq;
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rt_se->parent = parent;
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INIT_LIST_HEAD(&rt_se->run_list);
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}
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int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
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{
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struct rt_rq *rt_rq;
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struct sched_rt_entity *rt_se;
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int i;
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tg->rt_rq = kzalloc(sizeof(rt_rq) * nr_cpu_ids, GFP_KERNEL);
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if (!tg->rt_rq)
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goto err;
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tg->rt_se = kzalloc(sizeof(rt_se) * nr_cpu_ids, GFP_KERNEL);
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if (!tg->rt_se)
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goto err;
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init_rt_bandwidth(&tg->rt_bandwidth,
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ktime_to_ns(def_rt_bandwidth.rt_period), 0);
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for_each_possible_cpu(i) {
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rt_rq = kzalloc_node(sizeof(struct rt_rq),
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GFP_KERNEL, cpu_to_node(i));
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if (!rt_rq)
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goto err;
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rt_se = kzalloc_node(sizeof(struct sched_rt_entity),
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GFP_KERNEL, cpu_to_node(i));
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if (!rt_se)
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goto err_free_rq;
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init_rt_rq(rt_rq, cpu_rq(i));
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rt_rq->rt_runtime = tg->rt_bandwidth.rt_runtime;
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init_tg_rt_entry(tg, rt_rq, rt_se, i, parent->rt_se[i]);
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}
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return 1;
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err_free_rq:
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kfree(rt_rq);
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err:
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return 0;
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}
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#else /* CONFIG_RT_GROUP_SCHED */
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#define rt_entity_is_task(rt_se) (1)
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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 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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void free_rt_sched_group(struct task_group *tg) { }
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int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
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{
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return 1;
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}
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#endif /* CONFIG_RT_GROUP_SCHED */
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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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if (!rq->online)
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return;
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cpumask_set_cpu(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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* Matched by the barrier in pull_rt_task().
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*/
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smp_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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if (!rq->online)
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return;
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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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cpumask_clear_cpu(rq->cpu, rq->rd->rto_mask);
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}
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static void update_rt_migration(struct rt_rq *rt_rq)
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{
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if (rt_rq->rt_nr_migratory && rt_rq->rt_nr_total > 1) {
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if (!rt_rq->overloaded) {
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rt_set_overload(rq_of_rt_rq(rt_rq));
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rt_rq->overloaded = 1;
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}
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} else if (rt_rq->overloaded) {
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rt_clear_overload(rq_of_rt_rq(rt_rq));
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rt_rq->overloaded = 0;
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}
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}
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static void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
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{
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struct task_struct *p;
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if (!rt_entity_is_task(rt_se))
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return;
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p = rt_task_of(rt_se);
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rt_rq = &rq_of_rt_rq(rt_rq)->rt;
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rt_rq->rt_nr_total++;
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if (p->nr_cpus_allowed > 1)
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rt_rq->rt_nr_migratory++;
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update_rt_migration(rt_rq);
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}
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static void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
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{
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struct task_struct *p;
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if (!rt_entity_is_task(rt_se))
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return;
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p = rt_task_of(rt_se);
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rt_rq = &rq_of_rt_rq(rt_rq)->rt;
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rt_rq->rt_nr_total--;
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if (p->nr_cpus_allowed > 1)
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rt_rq->rt_nr_migratory--;
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update_rt_migration(rt_rq);
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}
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static inline int has_pushable_tasks(struct rq *rq)
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{
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return !plist_head_empty(&rq->rt.pushable_tasks);
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}
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static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
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{
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plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
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plist_node_init(&p->pushable_tasks, p->prio);
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plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks);
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/* Update the highest prio pushable task */
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if (p->prio < rq->rt.highest_prio.next)
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rq->rt.highest_prio.next = p->prio;
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}
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static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
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{
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plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
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/* Update the new highest prio pushable task */
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if (has_pushable_tasks(rq)) {
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p = plist_first_entry(&rq->rt.pushable_tasks,
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struct task_struct, pushable_tasks);
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rq->rt.highest_prio.next = p->prio;
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} else
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rq->rt.highest_prio.next = MAX_RT_PRIO;
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}
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#else
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static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
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{
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}
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static inline void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
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{
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}
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static inline
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void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
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{
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}
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static inline
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void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
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{
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}
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#endif /* CONFIG_SMP */
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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->rt_runtime;
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}
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static inline u64 sched_rt_period(struct rt_rq *rt_rq)
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{
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return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
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}
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typedef struct task_group *rt_rq_iter_t;
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static inline struct task_group *next_task_group(struct task_group *tg)
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{
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do {
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tg = list_entry_rcu(tg->list.next,
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typeof(struct task_group), list);
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} while (&tg->list != &task_groups && task_group_is_autogroup(tg));
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if (&tg->list == &task_groups)
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tg = NULL;
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return tg;
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}
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#define for_each_rt_rq(rt_rq, iter, rq) \
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for (iter = container_of(&task_groups, typeof(*iter), list); \
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(iter = next_task_group(iter)) && \
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(rt_rq = iter->rt_rq[cpu_of(rq)]);)
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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, bool head);
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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 task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
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struct sched_rt_entity *rt_se;
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int cpu = cpu_of(rq_of_rt_rq(rt_rq));
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rt_se = rt_rq->tg->rt_se[cpu];
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if (rt_rq->rt_nr_running) {
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if (rt_se && !on_rt_rq(rt_se))
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enqueue_rt_entity(rt_se, false);
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if (rt_rq->highest_prio.curr < 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;
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int cpu = cpu_of(rq_of_rt_rq(rt_rq));
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rt_se = rt_rq->tg->rt_se[cpu];
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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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#ifdef CONFIG_SMP
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static inline const struct cpumask *sched_rt_period_mask(void)
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{
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return this_rq()->rd->span;
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}
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#else
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static inline const struct cpumask *sched_rt_period_mask(void)
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{
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return cpu_online_mask;
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}
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#endif
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static inline
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struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
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{
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return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
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}
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static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
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{
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return &rt_rq->tg->rt_bandwidth;
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}
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|
|
#else /* !CONFIG_RT_GROUP_SCHED */
|
|
|
|
static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
|
|
{
|
|
return rt_rq->rt_runtime;
|
|
}
|
|
|
|
static inline u64 sched_rt_period(struct rt_rq *rt_rq)
|
|
{
|
|
return ktime_to_ns(def_rt_bandwidth.rt_period);
|
|
}
|
|
|
|
typedef struct rt_rq *rt_rq_iter_t;
|
|
|
|
#define for_each_rt_rq(rt_rq, iter, rq) \
|
|
for ((void) iter, rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
|
|
|
|
#define for_each_sched_rt_entity(rt_se) \
|
|
for (; rt_se; rt_se = NULL)
|
|
|
|
static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
|
|
{
|
|
return NULL;
|
|
}
|
|
|
|
static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
|
|
{
|
|
if (rt_rq->rt_nr_running)
|
|
resched_task(rq_of_rt_rq(rt_rq)->curr);
|
|
}
|
|
|
|
static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
|
|
{
|
|
}
|
|
|
|
static inline int rt_rq_throttled(struct rt_rq *rt_rq)
|
|
{
|
|
return rt_rq->rt_throttled;
|
|
}
|
|
|
|
static inline const struct cpumask *sched_rt_period_mask(void)
|
|
{
|
|
return cpu_online_mask;
|
|
}
|
|
|
|
static inline
|
|
struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
|
|
{
|
|
return &cpu_rq(cpu)->rt;
|
|
}
|
|
|
|
static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
|
|
{
|
|
return &def_rt_bandwidth;
|
|
}
|
|
|
|
#endif /* CONFIG_RT_GROUP_SCHED */
|
|
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* We ran out of runtime, see if we can borrow some from our neighbours.
|
|
*/
|
|
static int do_balance_runtime(struct rt_rq *rt_rq)
|
|
{
|
|
struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
|
|
struct root_domain *rd = rq_of_rt_rq(rt_rq)->rd;
|
|
int i, weight, more = 0;
|
|
u64 rt_period;
|
|
|
|
weight = cpumask_weight(rd->span);
|
|
|
|
raw_spin_lock(&rt_b->rt_runtime_lock);
|
|
rt_period = ktime_to_ns(rt_b->rt_period);
|
|
for_each_cpu(i, rd->span) {
|
|
struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
|
|
s64 diff;
|
|
|
|
if (iter == rt_rq)
|
|
continue;
|
|
|
|
raw_spin_lock(&iter->rt_runtime_lock);
|
|
/*
|
|
* Either all rqs have inf runtime and there's nothing to steal
|
|
* or __disable_runtime() below sets a specific rq to inf to
|
|
* indicate its been disabled and disalow stealing.
|
|
*/
|
|
if (iter->rt_runtime == RUNTIME_INF)
|
|
goto next;
|
|
|
|
/*
|
|
* From runqueues with spare time, take 1/n part of their
|
|
* spare time, but no more than our period.
|
|
*/
|
|
diff = iter->rt_runtime - iter->rt_time;
|
|
if (diff > 0) {
|
|
diff = div_u64((u64)diff, weight);
|
|
if (rt_rq->rt_runtime + diff > rt_period)
|
|
diff = rt_period - rt_rq->rt_runtime;
|
|
iter->rt_runtime -= diff;
|
|
rt_rq->rt_runtime += diff;
|
|
more = 1;
|
|
if (rt_rq->rt_runtime == rt_period) {
|
|
raw_spin_unlock(&iter->rt_runtime_lock);
|
|
break;
|
|
}
|
|
}
|
|
next:
|
|
raw_spin_unlock(&iter->rt_runtime_lock);
|
|
}
|
|
raw_spin_unlock(&rt_b->rt_runtime_lock);
|
|
|
|
return more;
|
|
}
|
|
|
|
/*
|
|
* Ensure this RQ takes back all the runtime it lend to its neighbours.
|
|
*/
|
|
static void __disable_runtime(struct rq *rq)
|
|
{
|
|
struct root_domain *rd = rq->rd;
|
|
rt_rq_iter_t iter;
|
|
struct rt_rq *rt_rq;
|
|
|
|
if (unlikely(!scheduler_running))
|
|
return;
|
|
|
|
for_each_rt_rq(rt_rq, iter, rq) {
|
|
struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
|
|
s64 want;
|
|
int i;
|
|
|
|
raw_spin_lock(&rt_b->rt_runtime_lock);
|
|
raw_spin_lock(&rt_rq->rt_runtime_lock);
|
|
/*
|
|
* Either we're all inf and nobody needs to borrow, or we're
|
|
* already disabled and thus have nothing to do, or we have
|
|
* exactly the right amount of runtime to take out.
|
|
*/
|
|
if (rt_rq->rt_runtime == RUNTIME_INF ||
|
|
rt_rq->rt_runtime == rt_b->rt_runtime)
|
|
goto balanced;
|
|
raw_spin_unlock(&rt_rq->rt_runtime_lock);
|
|
|
|
/*
|
|
* Calculate the difference between what we started out with
|
|
* and what we current have, that's the amount of runtime
|
|
* we lend and now have to reclaim.
|
|
*/
|
|
want = rt_b->rt_runtime - rt_rq->rt_runtime;
|
|
|
|
/*
|
|
* Greedy reclaim, take back as much as we can.
|
|
*/
|
|
for_each_cpu(i, rd->span) {
|
|
struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
|
|
s64 diff;
|
|
|
|
/*
|
|
* Can't reclaim from ourselves or disabled runqueues.
|
|
*/
|
|
if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
|
|
continue;
|
|
|
|
raw_spin_lock(&iter->rt_runtime_lock);
|
|
if (want > 0) {
|
|
diff = min_t(s64, iter->rt_runtime, want);
|
|
iter->rt_runtime -= diff;
|
|
want -= diff;
|
|
} else {
|
|
iter->rt_runtime -= want;
|
|
want -= want;
|
|
}
|
|
raw_spin_unlock(&iter->rt_runtime_lock);
|
|
|
|
if (!want)
|
|
break;
|
|
}
|
|
|
|
raw_spin_lock(&rt_rq->rt_runtime_lock);
|
|
/*
|
|
* We cannot be left wanting - that would mean some runtime
|
|
* leaked out of the system.
|
|
*/
|
|
BUG_ON(want);
|
|
balanced:
|
|
/*
|
|
* Disable all the borrow logic by pretending we have inf
|
|
* runtime - in which case borrowing doesn't make sense.
|
|
*/
|
|
rt_rq->rt_runtime = RUNTIME_INF;
|
|
rt_rq->rt_throttled = 0;
|
|
raw_spin_unlock(&rt_rq->rt_runtime_lock);
|
|
raw_spin_unlock(&rt_b->rt_runtime_lock);
|
|
}
|
|
}
|
|
|
|
static void __enable_runtime(struct rq *rq)
|
|
{
|
|
rt_rq_iter_t iter;
|
|
struct rt_rq *rt_rq;
|
|
|
|
if (unlikely(!scheduler_running))
|
|
return;
|
|
|
|
/*
|
|
* Reset each runqueue's bandwidth settings
|
|
*/
|
|
for_each_rt_rq(rt_rq, iter, rq) {
|
|
struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
|
|
|
|
raw_spin_lock(&rt_b->rt_runtime_lock);
|
|
raw_spin_lock(&rt_rq->rt_runtime_lock);
|
|
rt_rq->rt_runtime = rt_b->rt_runtime;
|
|
rt_rq->rt_time = 0;
|
|
rt_rq->rt_throttled = 0;
|
|
raw_spin_unlock(&rt_rq->rt_runtime_lock);
|
|
raw_spin_unlock(&rt_b->rt_runtime_lock);
|
|
}
|
|
}
|
|
|
|
static int balance_runtime(struct rt_rq *rt_rq)
|
|
{
|
|
int more = 0;
|
|
|
|
if (!sched_feat(RT_RUNTIME_SHARE))
|
|
return more;
|
|
|
|
if (rt_rq->rt_time > rt_rq->rt_runtime) {
|
|
raw_spin_unlock(&rt_rq->rt_runtime_lock);
|
|
more = do_balance_runtime(rt_rq);
|
|
raw_spin_lock(&rt_rq->rt_runtime_lock);
|
|
}
|
|
|
|
return more;
|
|
}
|
|
#else /* !CONFIG_SMP */
|
|
static inline int balance_runtime(struct rt_rq *rt_rq)
|
|
{
|
|
return 0;
|
|
}
|
|
#endif /* CONFIG_SMP */
|
|
|
|
static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
|
|
{
|
|
int i, idle = 1, throttled = 0;
|
|
const struct cpumask *span;
|
|
|
|
span = sched_rt_period_mask();
|
|
#ifdef CONFIG_RT_GROUP_SCHED
|
|
/*
|
|
* FIXME: isolated CPUs should really leave the root task group,
|
|
* whether they are isolcpus or were isolated via cpusets, lest
|
|
* the timer run on a CPU which does not service all runqueues,
|
|
* potentially leaving other CPUs indefinitely throttled. If
|
|
* isolation is really required, the user will turn the throttle
|
|
* off to kill the perturbations it causes anyway. Meanwhile,
|
|
* this maintains functionality for boot and/or troubleshooting.
|
|
*/
|
|
if (rt_b == &root_task_group.rt_bandwidth)
|
|
span = cpu_online_mask;
|
|
#endif
|
|
for_each_cpu(i, span) {
|
|
int enqueue = 0;
|
|
struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
|
|
struct rq *rq = rq_of_rt_rq(rt_rq);
|
|
|
|
raw_spin_lock(&rq->lock);
|
|
if (rt_rq->rt_time) {
|
|
u64 runtime;
|
|
|
|
raw_spin_lock(&rt_rq->rt_runtime_lock);
|
|
if (rt_rq->rt_throttled)
|
|
balance_runtime(rt_rq);
|
|
runtime = rt_rq->rt_runtime;
|
|
rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
|
|
if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
|
|
rt_rq->rt_throttled = 0;
|
|
enqueue = 1;
|
|
|
|
/*
|
|
* Force a clock update if the CPU was idle,
|
|
* lest wakeup -> unthrottle time accumulate.
|
|
*/
|
|
if (rt_rq->rt_nr_running && rq->curr == rq->idle)
|
|
rq->skip_clock_update = -1;
|
|
}
|
|
if (rt_rq->rt_time || rt_rq->rt_nr_running)
|
|
idle = 0;
|
|
raw_spin_unlock(&rt_rq->rt_runtime_lock);
|
|
} else if (rt_rq->rt_nr_running) {
|
|
idle = 0;
|
|
if (!rt_rq_throttled(rt_rq))
|
|
enqueue = 1;
|
|
}
|
|
if (rt_rq->rt_throttled)
|
|
throttled = 1;
|
|
|
|
if (enqueue)
|
|
sched_rt_rq_enqueue(rt_rq);
|
|
raw_spin_unlock(&rq->lock);
|
|
}
|
|
|
|
if (!throttled && (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF))
|
|
return 1;
|
|
|
|
return idle;
|
|
}
|
|
|
|
static inline int rt_se_prio(struct sched_rt_entity *rt_se)
|
|
{
|
|
#ifdef CONFIG_RT_GROUP_SCHED
|
|
struct rt_rq *rt_rq = group_rt_rq(rt_se);
|
|
|
|
if (rt_rq)
|
|
return rt_rq->highest_prio.curr;
|
|
#endif
|
|
|
|
return rt_task_of(rt_se)->prio;
|
|
}
|
|
|
|
static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
|
|
{
|
|
u64 runtime = sched_rt_runtime(rt_rq);
|
|
|
|
if (rt_rq->rt_throttled)
|
|
return rt_rq_throttled(rt_rq);
|
|
|
|
if (runtime >= sched_rt_period(rt_rq))
|
|
return 0;
|
|
|
|
balance_runtime(rt_rq);
|
|
runtime = sched_rt_runtime(rt_rq);
|
|
if (runtime == RUNTIME_INF)
|
|
return 0;
|
|
|
|
if (rt_rq->rt_time > runtime) {
|
|
struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
|
|
|
|
/*
|
|
* Don't actually throttle groups that have no runtime assigned
|
|
* but accrue some time due to boosting.
|
|
*/
|
|
if (likely(rt_b->rt_runtime)) {
|
|
static bool once = false;
|
|
|
|
rt_rq->rt_throttled = 1;
|
|
|
|
if (!once) {
|
|
once = true;
|
|
printk_sched("sched: RT throttling activated\n");
|
|
}
|
|
} else {
|
|
/*
|
|
* In case we did anyway, make it go away,
|
|
* replenishment is a joke, since it will replenish us
|
|
* with exactly 0 ns.
|
|
*/
|
|
rt_rq->rt_time = 0;
|
|
}
|
|
|
|
if (rt_rq_throttled(rt_rq)) {
|
|
sched_rt_rq_dequeue(rt_rq);
|
|
return 1;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Update the current task's runtime statistics. Skip current tasks that
|
|
* are not in our scheduling class.
|
|
*/
|
|
static void update_curr_rt(struct rq *rq)
|
|
{
|
|
struct task_struct *curr = rq->curr;
|
|
struct sched_rt_entity *rt_se = &curr->rt;
|
|
struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
|
|
u64 delta_exec;
|
|
|
|
if (curr->sched_class != &rt_sched_class)
|
|
return;
|
|
|
|
delta_exec = rq_clock_task(rq) - curr->se.exec_start;
|
|
if (unlikely((s64)delta_exec <= 0))
|
|
return;
|
|
|
|
schedstat_set(curr->se.statistics.exec_max,
|
|
max(curr->se.statistics.exec_max, delta_exec));
|
|
|
|
curr->se.sum_exec_runtime += delta_exec;
|
|
account_group_exec_runtime(curr, delta_exec);
|
|
|
|
curr->se.exec_start = rq_clock_task(rq);
|
|
cpuacct_charge(curr, delta_exec);
|
|
|
|
sched_rt_avg_update(rq, delta_exec);
|
|
|
|
if (!rt_bandwidth_enabled())
|
|
return;
|
|
|
|
for_each_sched_rt_entity(rt_se) {
|
|
rt_rq = rt_rq_of_se(rt_se);
|
|
|
|
if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
|
|
raw_spin_lock(&rt_rq->rt_runtime_lock);
|
|
rt_rq->rt_time += delta_exec;
|
|
if (sched_rt_runtime_exceeded(rt_rq))
|
|
resched_task(curr);
|
|
raw_spin_unlock(&rt_rq->rt_runtime_lock);
|
|
}
|
|
}
|
|
}
|
|
|
|
#if defined CONFIG_SMP
|
|
|
|
static void
|
|
inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
|
|
{
|
|
struct rq *rq = rq_of_rt_rq(rt_rq);
|
|
|
|
#ifdef CONFIG_RT_GROUP_SCHED
|
|
/*
|
|
* Change rq's cpupri only if rt_rq is the top queue.
|
|
*/
|
|
if (&rq->rt != rt_rq)
|
|
return;
|
|
#endif
|
|
if (rq->online && prio < prev_prio)
|
|
cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
|
|
}
|
|
|
|
static void
|
|
dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
|
|
{
|
|
struct rq *rq = rq_of_rt_rq(rt_rq);
|
|
|
|
#ifdef CONFIG_RT_GROUP_SCHED
|
|
/*
|
|
* Change rq's cpupri only if rt_rq is the top queue.
|
|
*/
|
|
if (&rq->rt != rt_rq)
|
|
return;
|
|
#endif
|
|
if (rq->online && rt_rq->highest_prio.curr != prev_prio)
|
|
cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
|
|
}
|
|
|
|
#else /* CONFIG_SMP */
|
|
|
|
static inline
|
|
void inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
|
|
static inline
|
|
void dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
|
|
|
|
#endif /* CONFIG_SMP */
|
|
|
|
#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
|
|
static void
|
|
inc_rt_prio(struct rt_rq *rt_rq, int prio)
|
|
{
|
|
int prev_prio = rt_rq->highest_prio.curr;
|
|
|
|
if (prio < prev_prio)
|
|
rt_rq->highest_prio.curr = prio;
|
|
|
|
inc_rt_prio_smp(rt_rq, prio, prev_prio);
|
|
}
|
|
|
|
static void
|
|
dec_rt_prio(struct rt_rq *rt_rq, int prio)
|
|
{
|
|
int prev_prio = rt_rq->highest_prio.curr;
|
|
|
|
if (rt_rq->rt_nr_running) {
|
|
|
|
WARN_ON(prio < prev_prio);
|
|
|
|
/*
|
|
* This may have been our highest task, and therefore
|
|
* we may have some recomputation to do
|
|
*/
|
|
if (prio == prev_prio) {
|
|
struct rt_prio_array *array = &rt_rq->active;
|
|
|
|
rt_rq->highest_prio.curr =
|
|
sched_find_first_bit(array->bitmap);
|
|
}
|
|
|
|
} else
|
|
rt_rq->highest_prio.curr = MAX_RT_PRIO;
|
|
|
|
dec_rt_prio_smp(rt_rq, prio, prev_prio);
|
|
}
|
|
|
|
#else
|
|
|
|
static inline void inc_rt_prio(struct rt_rq *rt_rq, int prio) {}
|
|
static inline void dec_rt_prio(struct rt_rq *rt_rq, int prio) {}
|
|
|
|
#endif /* CONFIG_SMP || CONFIG_RT_GROUP_SCHED */
|
|
|
|
#ifdef CONFIG_RT_GROUP_SCHED
|
|
|
|
static void
|
|
inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
|
|
{
|
|
if (rt_se_boosted(rt_se))
|
|
rt_rq->rt_nr_boosted++;
|
|
|
|
if (rt_rq->tg)
|
|
start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
|
|
}
|
|
|
|
static void
|
|
dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
|
|
{
|
|
if (rt_se_boosted(rt_se))
|
|
rt_rq->rt_nr_boosted--;
|
|
|
|
WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
|
|
}
|
|
|
|
#else /* CONFIG_RT_GROUP_SCHED */
|
|
|
|
static void
|
|
inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
|
|
{
|
|
start_rt_bandwidth(&def_rt_bandwidth);
|
|
}
|
|
|
|
static inline
|
|
void dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) {}
|
|
|
|
#endif /* CONFIG_RT_GROUP_SCHED */
|
|
|
|
static inline
|
|
void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
|
|
{
|
|
int prio = rt_se_prio(rt_se);
|
|
|
|
WARN_ON(!rt_prio(prio));
|
|
rt_rq->rt_nr_running++;
|
|
|
|
inc_rt_prio(rt_rq, prio);
|
|
inc_rt_migration(rt_se, rt_rq);
|
|
inc_rt_group(rt_se, rt_rq);
|
|
}
|
|
|
|
static inline
|
|
void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
|
|
{
|
|
WARN_ON(!rt_prio(rt_se_prio(rt_se)));
|
|
WARN_ON(!rt_rq->rt_nr_running);
|
|
rt_rq->rt_nr_running--;
|
|
|
|
dec_rt_prio(rt_rq, rt_se_prio(rt_se));
|
|
dec_rt_migration(rt_se, rt_rq);
|
|
dec_rt_group(rt_se, rt_rq);
|
|
}
|
|
|
|
static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
|
|
{
|
|
struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
|
|
struct rt_prio_array *array = &rt_rq->active;
|
|
struct rt_rq *group_rq = group_rt_rq(rt_se);
|
|
struct list_head *queue = array->queue + rt_se_prio(rt_se);
|
|
|
|
/*
|
|
* Don't enqueue the group if its throttled, or when empty.
|
|
* The latter is a consequence of the former when a child group
|
|
* get throttled and the current group doesn't have any other
|
|
* active members.
|
|
*/
|
|
if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
|
|
return;
|
|
|
|
if (head)
|
|
list_add(&rt_se->run_list, queue);
|
|
else
|
|
list_add_tail(&rt_se->run_list, queue);
|
|
__set_bit(rt_se_prio(rt_se), array->bitmap);
|
|
|
|
inc_rt_tasks(rt_se, rt_rq);
|
|
}
|
|
|
|
static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
|
|
{
|
|
struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
|
|
struct rt_prio_array *array = &rt_rq->active;
|
|
|
|
list_del_init(&rt_se->run_list);
|
|
if (list_empty(array->queue + rt_se_prio(rt_se)))
|
|
__clear_bit(rt_se_prio(rt_se), array->bitmap);
|
|
|
|
dec_rt_tasks(rt_se, rt_rq);
|
|
}
|
|
|
|
/*
|
|
* Because the prio of an upper entry depends on the lower
|
|
* entries, we must remove entries top - down.
|
|
*/
|
|
static void dequeue_rt_stack(struct sched_rt_entity *rt_se)
|
|
{
|
|
struct sched_rt_entity *back = NULL;
|
|
|
|
for_each_sched_rt_entity(rt_se) {
|
|
rt_se->back = back;
|
|
back = rt_se;
|
|
}
|
|
|
|
for (rt_se = back; rt_se; rt_se = rt_se->back) {
|
|
if (on_rt_rq(rt_se))
|
|
__dequeue_rt_entity(rt_se);
|
|
}
|
|
}
|
|
|
|
static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
|
|
{
|
|
dequeue_rt_stack(rt_se);
|
|
for_each_sched_rt_entity(rt_se)
|
|
__enqueue_rt_entity(rt_se, head);
|
|
}
|
|
|
|
static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
|
|
{
|
|
dequeue_rt_stack(rt_se);
|
|
|
|
for_each_sched_rt_entity(rt_se) {
|
|
struct rt_rq *rt_rq = group_rt_rq(rt_se);
|
|
|
|
if (rt_rq && rt_rq->rt_nr_running)
|
|
__enqueue_rt_entity(rt_se, false);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Adding/removing a task to/from a priority array:
|
|
*/
|
|
static void
|
|
enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
|
|
{
|
|
struct sched_rt_entity *rt_se = &p->rt;
|
|
|
|
if (flags & ENQUEUE_WAKEUP)
|
|
rt_se->timeout = 0;
|
|
|
|
enqueue_rt_entity(rt_se, flags & ENQUEUE_HEAD);
|
|
|
|
if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
|
|
enqueue_pushable_task(rq, p);
|
|
|
|
inc_nr_running(rq);
|
|
}
|
|
|
|
static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
|
|
{
|
|
struct sched_rt_entity *rt_se = &p->rt;
|
|
|
|
update_curr_rt(rq);
|
|
dequeue_rt_entity(rt_se);
|
|
|
|
dequeue_pushable_task(rq, p);
|
|
|
|
dec_nr_running(rq);
|
|
}
|
|
|
|
/*
|
|
* Put task to the head or the end of the run list without the overhead of
|
|
* dequeue followed by enqueue.
|
|
*/
|
|
static void
|
|
requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
|
|
{
|
|
if (on_rt_rq(rt_se)) {
|
|
struct rt_prio_array *array = &rt_rq->active;
|
|
struct list_head *queue = array->queue + rt_se_prio(rt_se);
|
|
|
|
if (head)
|
|
list_move(&rt_se->run_list, queue);
|
|
else
|
|
list_move_tail(&rt_se->run_list, queue);
|
|
}
|
|
}
|
|
|
|
static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
|
|
{
|
|
struct sched_rt_entity *rt_se = &p->rt;
|
|
struct rt_rq *rt_rq;
|
|
|
|
for_each_sched_rt_entity(rt_se) {
|
|
rt_rq = rt_rq_of_se(rt_se);
|
|
requeue_rt_entity(rt_rq, rt_se, head);
|
|
}
|
|
}
|
|
|
|
static void yield_task_rt(struct rq *rq)
|
|
{
|
|
requeue_task_rt(rq, rq->curr, 0);
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
static int find_lowest_rq(struct task_struct *task);
|
|
|
|
static int
|
|
select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
|
|
{
|
|
struct task_struct *curr;
|
|
struct rq *rq;
|
|
|
|
if (p->nr_cpus_allowed == 1)
|
|
goto out;
|
|
|
|
/* For anything but wake ups, just return the task_cpu */
|
|
if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
|
|
goto out;
|
|
|
|
rq = cpu_rq(cpu);
|
|
|
|
rcu_read_lock();
|
|
curr = ACCESS_ONCE(rq->curr); /* unlocked access */
|
|
|
|
/*
|
|
* If the current task on @p's runqueue is an RT task, then
|
|
* try to see if we can wake this RT task up on another
|
|
* runqueue. Otherwise simply start this RT task
|
|
* on its current runqueue.
|
|
*
|
|
* We want to avoid overloading runqueues. If the woken
|
|
* task is a higher priority, then it will stay on this CPU
|
|
* and the lower prio task should be moved to another CPU.
|
|
* Even though this will probably make the lower prio task
|
|
* lose its cache, we do not want to bounce a higher task
|
|
* around just because it gave up its CPU, perhaps for a
|
|
* lock?
|
|
*
|
|
* For equal prio tasks, we just let the scheduler sort it out.
|
|
*
|
|
* Otherwise, just let it ride on the affined RQ and the
|
|
* post-schedule router will push the preempted task away
|
|
*
|
|
* This test is optimistic, if we get it wrong the load-balancer
|
|
* will have to sort it out.
|
|
*/
|
|
if (curr && unlikely(rt_task(curr)) &&
|
|
(curr->nr_cpus_allowed < 2 ||
|
|
curr->prio <= p->prio)) {
|
|
int target = find_lowest_rq(p);
|
|
|
|
if (target != -1)
|
|
cpu = target;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
out:
|
|
return cpu;
|
|
}
|
|
|
|
static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
|
|
{
|
|
if (rq->curr->nr_cpus_allowed == 1)
|
|
return;
|
|
|
|
if (p->nr_cpus_allowed != 1
|
|
&& cpupri_find(&rq->rd->cpupri, p, NULL))
|
|
return;
|
|
|
|
if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
|
|
return;
|
|
|
|
/*
|
|
* There appears to be other cpus that can accept
|
|
* current and none to run 'p', so lets reschedule
|
|
* to try and push current away:
|
|
*/
|
|
requeue_task_rt(rq, p, 1);
|
|
resched_task(rq->curr);
|
|
}
|
|
|
|
#endif /* CONFIG_SMP */
|
|
|
|
/*
|
|
* Preempt the current task with a newly woken task if needed:
|
|
*/
|
|
static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flags)
|
|
{
|
|
if (p->prio < rq->curr->prio) {
|
|
resched_task(rq->curr);
|
|
return;
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* 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 (p->prio == rq->curr->prio && !test_tsk_need_resched(rq->curr))
|
|
check_preempt_equal_prio(rq, p);
|
|
#endif
|
|
}
|
|
|
|
static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
|
|
struct rt_rq *rt_rq)
|
|
{
|
|
struct rt_prio_array *array = &rt_rq->active;
|
|
struct sched_rt_entity *next = NULL;
|
|
struct list_head *queue;
|
|
int idx;
|
|
|
|
idx = sched_find_first_bit(array->bitmap);
|
|
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 (!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_task(rq);
|
|
|
|
return p;
|
|
}
|
|
|
|
static struct task_struct *pick_next_task_rt(struct rq *rq)
|
|
{
|
|
struct task_struct *p = _pick_next_task_rt(rq);
|
|
|
|
/* The running task is never eligible for pushing */
|
|
if (p)
|
|
dequeue_pushable_task(rq, p);
|
|
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* We detect this state here so that we can avoid taking the RQ
|
|
* lock again later if there is no need to push
|
|
*/
|
|
rq->post_schedule = has_pushable_tasks(rq);
|
|
#endif
|
|
|
|
return p;
|
|
}
|
|
|
|
static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
|
|
{
|
|
update_curr_rt(rq);
|
|
|
|
/*
|
|
* The previous task needs to be made eligible for pushing
|
|
* if it is still active
|
|
*/
|
|
if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1)
|
|
enqueue_pushable_task(rq, p);
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
/* Only try algorithms three times */
|
|
#define RT_MAX_TRIES 3
|
|
|
|
static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
|
|
{
|
|
if (!task_running(rq, p) &&
|
|
cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
|
|
return 1;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Return the highest pushable rq's task, which is suitable to be executed
|
|
* on the cpu, NULL otherwise
|
|
*/
|
|
static struct task_struct *pick_highest_pushable_task(struct rq *rq, int cpu)
|
|
{
|
|
struct plist_head *head = &rq->rt.pushable_tasks;
|
|
struct task_struct *p;
|
|
|
|
if (!has_pushable_tasks(rq))
|
|
return NULL;
|
|
|
|
plist_for_each_entry(p, head, pushable_tasks) {
|
|
if (pick_rt_task(rq, p, cpu))
|
|
return p;
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
|
|
|
|
static int find_lowest_rq(struct task_struct *task)
|
|
{
|
|
struct sched_domain *sd;
|
|
struct cpumask *lowest_mask = __get_cpu_var(local_cpu_mask);
|
|
int this_cpu = smp_processor_id();
|
|
int cpu = task_cpu(task);
|
|
|
|
/* Make sure the mask is initialized first */
|
|
if (unlikely(!lowest_mask))
|
|
return -1;
|
|
|
|
if (task->nr_cpus_allowed == 1)
|
|
return -1; /* No other targets possible */
|
|
|
|
if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
|
|
return -1; /* No targets found */
|
|
|
|
/*
|
|
* 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 (cpumask_test_cpu(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 (!cpumask_test_cpu(this_cpu, lowest_mask))
|
|
this_cpu = -1; /* Skip this_cpu opt if not among lowest */
|
|
|
|
rcu_read_lock();
|
|
for_each_domain(cpu, sd) {
|
|
if (sd->flags & SD_WAKE_AFFINE) {
|
|
int best_cpu;
|
|
|
|
/*
|
|
* "this_cpu" is cheaper to preempt than a
|
|
* remote processor.
|
|
*/
|
|
if (this_cpu != -1 &&
|
|
cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
|
|
rcu_read_unlock();
|
|
return this_cpu;
|
|
}
|
|
|
|
best_cpu = cpumask_first_and(lowest_mask,
|
|
sched_domain_span(sd));
|
|
if (best_cpu < nr_cpu_ids) {
|
|
rcu_read_unlock();
|
|
return best_cpu;
|
|
}
|
|
}
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
/*
|
|
* And finally, if there were no matches within the domains
|
|
* just give the caller *something* to work with from the compatible
|
|
* locations.
|
|
*/
|
|
if (this_cpu != -1)
|
|
return this_cpu;
|
|
|
|
cpu = cpumask_any(lowest_mask);
|
|
if (cpu < nr_cpu_ids)
|
|
return cpu;
|
|
return -1;
|
|
}
|
|
|
|
/* 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 ||
|
|
!cpumask_test_cpu(lowest_rq->cpu,
|
|
tsk_cpus_allowed(task)) ||
|
|
task_running(rq, task) ||
|
|
!task->on_rq)) {
|
|
|
|
double_unlock_balance(rq, lowest_rq);
|
|
lowest_rq = NULL;
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* If this rq is still suitable use it. */
|
|
if (lowest_rq->rt.highest_prio.curr > task->prio)
|
|
break;
|
|
|
|
/* try again */
|
|
double_unlock_balance(rq, lowest_rq);
|
|
lowest_rq = NULL;
|
|
}
|
|
|
|
return lowest_rq;
|
|
}
|
|
|
|
static struct task_struct *pick_next_pushable_task(struct rq *rq)
|
|
{
|
|
struct task_struct *p;
|
|
|
|
if (!has_pushable_tasks(rq))
|
|
return NULL;
|
|
|
|
p = plist_first_entry(&rq->rt.pushable_tasks,
|
|
struct task_struct, pushable_tasks);
|
|
|
|
BUG_ON(rq->cpu != task_cpu(p));
|
|
BUG_ON(task_current(rq, p));
|
|
BUG_ON(p->nr_cpus_allowed <= 1);
|
|
|
|
BUG_ON(!p->on_rq);
|
|
BUG_ON(!rt_task(p));
|
|
|
|
return p;
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
|
|
if (!rq->rt.overloaded)
|
|
return 0;
|
|
|
|
next_task = pick_next_pushable_task(rq);
|
|
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 migrated.
|
|
*
|
|
* We need to make sure that the task is still on the same
|
|
* run-queue and is also still the next task eligible for
|
|
* pushing.
|
|
*/
|
|
task = pick_next_pushable_task(rq);
|
|
if (task_cpu(next_task) == rq->cpu && task == next_task) {
|
|
/*
|
|
* The task hasn't migrated, and is still the next
|
|
* eligible task, but we failed to find a run-queue
|
|
* to push it to. Do not retry in this case, since
|
|
* other cpus will pull from us when ready.
|
|
*/
|
|
goto out;
|
|
}
|
|
|
|
if (!task)
|
|
/* No more tasks, just exit */
|
|
goto out;
|
|
|
|
/*
|
|
* Something has shifted, try again.
|
|
*/
|
|
put_task_struct(next_task);
|
|
next_task = task;
|
|
goto retry;
|
|
}
|
|
|
|
deactivate_task(rq, next_task, 0);
|
|
set_task_cpu(next_task, lowest_rq->cpu);
|
|
activate_task(lowest_rq, next_task, 0);
|
|
ret = 1;
|
|
|
|
resched_task(lowest_rq->curr);
|
|
|
|
double_unlock_balance(rq, lowest_rq);
|
|
|
|
out:
|
|
put_task_struct(next_task);
|
|
|
|
return ret;
|
|
}
|
|
|
|
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;
|
|
struct rq *src_rq;
|
|
|
|
if (likely(!rt_overloaded(this_rq)))
|
|
return 0;
|
|
|
|
/*
|
|
* Match the barrier from rt_set_overloaded; this guarantees that if we
|
|
* see overloaded we must also see the rto_mask bit.
|
|
*/
|
|
smp_rmb();
|
|
|
|
for_each_cpu(cpu, this_rq->rd->rto_mask) {
|
|
if (this_cpu == cpu)
|
|
continue;
|
|
|
|
src_rq = cpu_rq(cpu);
|
|
|
|
/*
|
|
* Don't bother taking the src_rq->lock if the next highest
|
|
* task is known to be lower-priority than our current task.
|
|
* This may look racy, but if this value is about to go
|
|
* logically higher, the src_rq will push this task away.
|
|
* And if its going logically lower, we do not care
|
|
*/
|
|
if (src_rq->rt.highest_prio.next >=
|
|
this_rq->rt.highest_prio.curr)
|
|
continue;
|
|
|
|
/*
|
|
* We can potentially drop this_rq's lock in
|
|
* double_lock_balance, and another CPU could
|
|
* alter this_rq
|
|
*/
|
|
double_lock_balance(this_rq, src_rq);
|
|
|
|
/*
|
|
* We can pull only a task, which is pushable
|
|
* on its rq, and no others.
|
|
*/
|
|
p = pick_highest_pushable_task(src_rq, this_cpu);
|
|
|
|
/*
|
|
* Do we have an RT task that preempts
|
|
* the to-be-scheduled task?
|
|
*/
|
|
if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
|
|
WARN_ON(p == src_rq->curr);
|
|
WARN_ON(!p->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
|
|
*/
|
|
if (p->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 likelihood
|
|
* but possible)
|
|
*/
|
|
}
|
|
skip:
|
|
double_unlock_balance(this_rq, src_rq);
|
|
}
|
|
|
|
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 (rq->rt.highest_prio.curr > prev->prio)
|
|
pull_rt_task(rq);
|
|
}
|
|
|
|
static void post_schedule_rt(struct rq *rq)
|
|
{
|
|
push_rt_tasks(rq);
|
|
}
|
|
|
|
/*
|
|
* If we are not running and we are not going to reschedule soon, we should
|
|
* try to push tasks away now
|
|
*/
|
|
static void task_woken_rt(struct rq *rq, struct task_struct *p)
|
|
{
|
|
if (!task_running(rq, p) &&
|
|
!test_tsk_need_resched(rq->curr) &&
|
|
has_pushable_tasks(rq) &&
|
|
p->nr_cpus_allowed > 1 &&
|
|
(dl_task(rq->curr) || rt_task(rq->curr)) &&
|
|
(rq->curr->nr_cpus_allowed < 2 ||
|
|
rq->curr->prio <= p->prio))
|
|
push_rt_tasks(rq);
|
|
}
|
|
|
|
static void set_cpus_allowed_rt(struct task_struct *p,
|
|
const struct cpumask *new_mask)
|
|
{
|
|
struct rq *rq;
|
|
int weight;
|
|
|
|
BUG_ON(!rt_task(p));
|
|
|
|
if (!p->on_rq)
|
|
return;
|
|
|
|
weight = cpumask_weight(new_mask);
|
|
|
|
/*
|
|
* Only update if the process changes its state from whether it
|
|
* can migrate or not.
|
|
*/
|
|
if ((p->nr_cpus_allowed > 1) == (weight > 1))
|
|
return;
|
|
|
|
rq = task_rq(p);
|
|
|
|
/*
|
|
* The process used to be able to migrate OR it can now migrate
|
|
*/
|
|
if (weight <= 1) {
|
|
if (!task_current(rq, p))
|
|
dequeue_pushable_task(rq, p);
|
|
BUG_ON(!rq->rt.rt_nr_migratory);
|
|
rq->rt.rt_nr_migratory--;
|
|
} else {
|
|
if (!task_current(rq, p))
|
|
enqueue_pushable_task(rq, p);
|
|
rq->rt.rt_nr_migratory++;
|
|
}
|
|
|
|
update_rt_migration(&rq->rt);
|
|
}
|
|
|
|
/* Assumes rq->lock is held */
|
|
static void rq_online_rt(struct rq *rq)
|
|
{
|
|
if (rq->rt.overloaded)
|
|
rt_set_overload(rq);
|
|
|
|
__enable_runtime(rq);
|
|
|
|
cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
|
|
}
|
|
|
|
/* Assumes rq->lock is held */
|
|
static void rq_offline_rt(struct rq *rq)
|
|
{
|
|
if (rq->rt.overloaded)
|
|
rt_clear_overload(rq);
|
|
|
|
__disable_runtime(rq);
|
|
|
|
cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
|
|
}
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
/*
|
|
* 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 (!p->on_rq || rq->rt.rt_nr_running)
|
|
return;
|
|
|
|
if (pull_rt_task(rq))
|
|
resched_task(rq->curr);
|
|
}
|
|
|
|
void init_sched_rt_class(void)
|
|
{
|
|
unsigned int i;
|
|
|
|
for_each_possible_cpu(i) {
|
|
zalloc_cpumask_var_node(&per_cpu(local_cpu_mask, i),
|
|
GFP_KERNEL, cpu_to_node(i));
|
|
}
|
|
}
|
|
#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 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 (p->on_rq && rq->curr != p) {
|
|
#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)
|
|
{
|
|
if (!p->on_rq)
|
|
return;
|
|
|
|
if (rq->curr == p) {
|
|
#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. Note, the above pull_rt_task
|
|
* can release the rq lock and p could migrate.
|
|
* Only reschedule if p is still on the same runqueue.
|
|
*/
|
|
if (p->prio > rq->rt.highest_prio.curr && rq->curr == p)
|
|
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;
|
|
|
|
/* max may change after cur was read, this will be fixed next tick */
|
|
soft = task_rlimit(p, RLIMIT_RTTIME);
|
|
hard = task_rlimit_max(p, RLIMIT_RTTIME);
|
|
|
|
if (soft != RLIM_INFINITY) {
|
|
unsigned long next;
|
|
|
|
if (p->rt.watchdog_stamp != jiffies) {
|
|
p->rt.timeout++;
|
|
p->rt.watchdog_stamp = jiffies;
|
|
}
|
|
|
|
next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
|
|
if (p->rt.timeout > next)
|
|
p->cputime_expires.sched_exp = p->se.sum_exec_runtime;
|
|
}
|
|
}
|
|
|
|
static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
|
|
{
|
|
struct sched_rt_entity *rt_se = &p->rt;
|
|
|
|
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 = sched_rr_timeslice;
|
|
|
|
/*
|
|
* Requeue to the end of queue if we (and all of our ancestors) are not
|
|
* the only element on the queue
|
|
*/
|
|
for_each_sched_rt_entity(rt_se) {
|
|
if (rt_se->run_list.prev != rt_se->run_list.next) {
|
|
requeue_task_rt(rq, p, 0);
|
|
set_tsk_need_resched(p);
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
|
|
static void set_curr_task_rt(struct rq *rq)
|
|
{
|
|
struct task_struct *p = rq->curr;
|
|
|
|
p->se.exec_start = rq_clock_task(rq);
|
|
|
|
/* The running task is never eligible for pushing */
|
|
dequeue_pushable_task(rq, p);
|
|
}
|
|
|
|
static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
|
|
{
|
|
/*
|
|
* Time slice is 0 for SCHED_FIFO tasks
|
|
*/
|
|
if (task->policy == SCHED_RR)
|
|
return sched_rr_timeslice;
|
|
else
|
|
return 0;
|
|
}
|
|
|
|
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,
|
|
|
|
.check_preempt_curr = check_preempt_curr_rt,
|
|
|
|
.pick_next_task = pick_next_task_rt,
|
|
.put_prev_task = put_prev_task_rt,
|
|
|
|
#ifdef CONFIG_SMP
|
|
.select_task_rq = select_task_rq_rt,
|
|
|
|
.set_cpus_allowed = set_cpus_allowed_rt,
|
|
.rq_online = rq_online_rt,
|
|
.rq_offline = rq_offline_rt,
|
|
.pre_schedule = pre_schedule_rt,
|
|
.post_schedule = post_schedule_rt,
|
|
.task_woken = task_woken_rt,
|
|
.switched_from = switched_from_rt,
|
|
#endif
|
|
|
|
.set_curr_task = set_curr_task_rt,
|
|
.task_tick = task_tick_rt,
|
|
|
|
.get_rr_interval = get_rr_interval_rt,
|
|
|
|
.prio_changed = prio_changed_rt,
|
|
.switched_to = switched_to_rt,
|
|
};
|
|
|
|
#ifdef CONFIG_SCHED_DEBUG
|
|
extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq);
|
|
|
|
void print_rt_stats(struct seq_file *m, int cpu)
|
|
{
|
|
rt_rq_iter_t iter;
|
|
struct rt_rq *rt_rq;
|
|
|
|
rcu_read_lock();
|
|
for_each_rt_rq(rt_rq, iter, cpu_rq(cpu))
|
|
print_rt_rq(m, cpu, rt_rq);
|
|
rcu_read_unlock();
|
|
}
|
|
#endif /* CONFIG_SCHED_DEBUG */
|