2 * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
7 * Update the current task's runtime statistics. Skip current tasks that
8 * are not in our scheduling class.
10 static void update_curr_rt(struct rq *rq)
12 struct task_struct *curr = rq->curr;
15 if (!task_has_rt_policy(curr))
18 delta_exec = rq->clock - curr->se.exec_start;
19 if (unlikely((s64)delta_exec < 0))
22 schedstat_set(curr->se.exec_max, max(curr->se.exec_max, delta_exec));
24 curr->se.sum_exec_runtime += delta_exec;
25 curr->se.exec_start = rq->clock;
26 cpuacct_charge(curr, delta_exec);
29 static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
31 struct rt_prio_array *array = &rq->rt.active;
33 list_add_tail(&p->run_list, array->queue + p->prio);
34 __set_bit(p->prio, array->bitmap);
35 inc_cpu_load(rq, p->se.load.weight);
39 * Adding/removing a task to/from a priority array:
41 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
43 struct rt_prio_array *array = &rq->rt.active;
47 list_del(&p->run_list);
48 if (list_empty(array->queue + p->prio))
49 __clear_bit(p->prio, array->bitmap);
50 dec_cpu_load(rq, p->se.load.weight);
54 * Put task to the end of the run list without the overhead of dequeue
55 * followed by enqueue.
57 static void requeue_task_rt(struct rq *rq, struct task_struct *p)
59 struct rt_prio_array *array = &rq->rt.active;
61 list_move_tail(&p->run_list, array->queue + p->prio);
65 yield_task_rt(struct rq *rq)
67 requeue_task_rt(rq, rq->curr);
71 * Preempt the current task with a newly woken task if needed:
73 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p)
75 if (p->prio < rq->curr->prio)
76 resched_task(rq->curr);
79 static struct task_struct *pick_next_task_rt(struct rq *rq)
81 struct rt_prio_array *array = &rq->rt.active;
82 struct task_struct *next;
83 struct list_head *queue;
86 idx = sched_find_first_bit(array->bitmap);
87 if (idx >= MAX_RT_PRIO)
90 queue = array->queue + idx;
91 next = list_entry(queue->next, struct task_struct, run_list);
93 next->se.exec_start = rq->clock;
98 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
101 p->se.exec_start = 0;
106 * Load-balancing iterator. Note: while the runqueue stays locked
107 * during the whole iteration, the current task might be
108 * dequeued so the iterator has to be dequeue-safe. Here we
109 * achieve that by always pre-iterating before returning
112 static struct task_struct *load_balance_start_rt(void *arg)
115 struct rt_prio_array *array = &rq->rt.active;
116 struct list_head *head, *curr;
117 struct task_struct *p;
120 idx = sched_find_first_bit(array->bitmap);
121 if (idx >= MAX_RT_PRIO)
124 head = array->queue + idx;
127 p = list_entry(curr, struct task_struct, run_list);
131 rq->rt.rt_load_balance_idx = idx;
132 rq->rt.rt_load_balance_head = head;
133 rq->rt.rt_load_balance_curr = curr;
138 static struct task_struct *load_balance_next_rt(void *arg)
141 struct rt_prio_array *array = &rq->rt.active;
142 struct list_head *head, *curr;
143 struct task_struct *p;
146 idx = rq->rt.rt_load_balance_idx;
147 head = rq->rt.rt_load_balance_head;
148 curr = rq->rt.rt_load_balance_curr;
151 * If we arrived back to the head again then
152 * iterate to the next queue (if any):
154 if (unlikely(head == curr)) {
155 int next_idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
157 if (next_idx >= MAX_RT_PRIO)
161 head = array->queue + idx;
164 rq->rt.rt_load_balance_idx = idx;
165 rq->rt.rt_load_balance_head = head;
168 p = list_entry(curr, struct task_struct, run_list);
172 rq->rt.rt_load_balance_curr = curr;
178 load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
179 unsigned long max_load_move,
180 struct sched_domain *sd, enum cpu_idle_type idle,
181 int *all_pinned, int *this_best_prio)
183 struct rq_iterator rt_rq_iterator;
185 rt_rq_iterator.start = load_balance_start_rt;
186 rt_rq_iterator.next = load_balance_next_rt;
187 /* pass 'busiest' rq argument into
188 * load_balance_[start|next]_rt iterators
190 rt_rq_iterator.arg = busiest;
192 return balance_tasks(this_rq, this_cpu, busiest, max_load_move, sd,
193 idle, all_pinned, this_best_prio, &rt_rq_iterator);
197 move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
198 struct sched_domain *sd, enum cpu_idle_type idle)
200 struct rq_iterator rt_rq_iterator;
202 rt_rq_iterator.start = load_balance_start_rt;
203 rt_rq_iterator.next = load_balance_next_rt;
204 rt_rq_iterator.arg = busiest;
206 return iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
211 static void task_tick_rt(struct rq *rq, struct task_struct *p)
216 * RR tasks need a special form of timeslice management.
217 * FIFO tasks have no timeslices.
219 if (p->policy != SCHED_RR)
225 p->time_slice = DEF_TIMESLICE;
228 * Requeue to the end of queue if we are not the only element
231 if (p->run_list.prev != p->run_list.next) {
232 requeue_task_rt(rq, p);
233 set_tsk_need_resched(p);
237 static void set_curr_task_rt(struct rq *rq)
239 struct task_struct *p = rq->curr;
241 p->se.exec_start = rq->clock;
244 const struct sched_class rt_sched_class = {
245 .next = &fair_sched_class,
246 .enqueue_task = enqueue_task_rt,
247 .dequeue_task = dequeue_task_rt,
248 .yield_task = yield_task_rt,
250 .check_preempt_curr = check_preempt_curr_rt,
252 .pick_next_task = pick_next_task_rt,
253 .put_prev_task = put_prev_task_rt,
256 .load_balance = load_balance_rt,
257 .move_one_task = move_one_task_rt,
260 .set_curr_task = set_curr_task_rt,
261 .task_tick = task_tick_rt,