diff options
| -rw-r--r-- | kernel/sched_rt.c | 255 |
1 files changed, 255 insertions, 0 deletions
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c new file mode 100644 index 00000000000..1192a2741b9 --- /dev/null +++ b/kernel/sched_rt.c @@ -0,0 +1,255 @@ +/* + * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR + * policies) + */ + +/* + * Update the current task's runtime statistics. Skip current tasks that + * are not in our scheduling class. + */ +static inline void update_curr_rt(struct rq *rq, u64 now) +{ + struct task_struct *curr = rq->curr; + u64 delta_exec; + + if (!task_has_rt_policy(curr)) + return; + + delta_exec = now - curr->se.exec_start; + if (unlikely((s64)delta_exec < 0)) + delta_exec = 0; + if (unlikely(delta_exec > curr->se.exec_max)) + curr->se.exec_max = delta_exec; + + curr->se.sum_exec_runtime += delta_exec; + curr->se.exec_start = now; +} + +static void +enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup, u64 now) +{ + struct rt_prio_array *array = &rq->rt.active; + + list_add_tail(&p->run_list, array->queue + p->prio); + __set_bit(p->prio, array->bitmap); +} + +/* + * Adding/removing a task to/from a priority array: + */ +static void +dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep, u64 now) +{ + struct rt_prio_array *array = &rq->rt.active; + + update_curr_rt(rq, now); + + list_del(&p->run_list); + if (list_empty(array->queue + p->prio)) + __clear_bit(p->prio, array->bitmap); +} + +/* + * Put task to the end of the run list without the overhead of dequeue + * followed by enqueue. + */ +static void requeue_task_rt(struct rq *rq, struct task_struct *p) +{ + struct rt_prio_array *array = &rq->rt.active; + + list_move_tail(&p->run_list, array->queue + p->prio); +} + +static void +yield_task_rt(struct rq *rq, struct task_struct *p) +{ + requeue_task_rt(rq, p); +} + +/* + * Preempt the current task with a newly woken task if needed: + */ +static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p) +{ + if (p->prio < rq->curr->prio) + resched_task(rq->curr); +} + +static struct task_struct *pick_next_task_rt(struct rq *rq, u64 now) +{ + struct rt_prio_array *array = &rq->rt.active; + struct task_struct *next; + struct list_head *queue; + int idx; + + idx = sched_find_first_bit(array->bitmap); + if (idx >= MAX_RT_PRIO) + return NULL; + + queue = array->queue + idx; + next = list_entry(queue->next, struct task_struct, run_list); + + next->se.exec_start = now; + + return next; +} + +static void put_prev_task_rt(struct rq *rq, struct task_struct *p, u64 now) +{ + update_curr_rt(rq, now); + p->se.exec_start = 0; +} + +/* + * Load-balancing iterator. Note: while the runqueue stays locked + * during the whole iteration, the current task might be + * dequeued so the iterator has to be dequeue-safe. Here we + * achieve that by always pre-iterating before returning + * the current task: + */ +static struct task_struct *load_balance_start_rt(void *arg) +{ + struct rq *rq = arg; + struct rt_prio_array *array = &rq->rt.active; + struct list_head *head, *curr; + struct task_struct *p; + int idx; + + idx = sched_find_first_bit(array->bitmap); + if (idx >= MAX_RT_PRIO) + return NULL; + + head = array->queue + idx; + curr = head->prev; + + p = list_entry(curr, struct task_struct, run_list); + + curr = curr->prev; + + rq->rt.rt_load_balance_idx = idx; + rq->rt.rt_load_balance_head = head; + rq->rt.rt_load_balance_curr = curr; + + return p; +} + +static struct task_struct *load_balance_next_rt(void *arg) +{ + struct rq *rq = arg; + struct rt_prio_array *array = &rq->rt.active; + struct list_head *head, *curr; + struct task_struct *p; + int idx; + + idx = rq->rt.rt_load_balance_idx; + head = rq->rt.rt_load_balance_head; + curr = rq->rt.rt_load_balance_curr; + + /* + * If we arrived back to the head again then + * iterate to the next queue (if any): + */ + if (unlikely(head == curr)) { + int next_idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1); + + if (next_idx >= MAX_RT_PRIO) + return NULL; + + idx = next_idx; + head = array->queue + idx; + curr = head->prev; + + rq->rt.rt_load_balance_idx = idx; + rq->rt.rt_load_balance_head = head; + } + + p = list_entry(curr, struct task_struct, run_list); + + curr = curr->prev; + + rq->rt.rt_load_balance_curr = curr; + + return p; +} + +static int +load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest, + unsigned long max_nr_move, unsigned long max_load_move, + struct sched_domain *sd, enum cpu_idle_type idle, + int *all_pinned, unsigned long *load_moved) +{ + int this_best_prio, best_prio, best_prio_seen = 0; + int nr_moved; + struct rq_iterator rt_rq_iterator; + + best_prio = sched_find_first_bit(busiest->rt.active.bitmap); + this_best_prio = sched_find_first_bit(this_rq->rt.active.bitmap); + + /* + * Enable handling of the case where there is more than one task + * with the best priority. If the current running task is one + * of those with prio==best_prio we know it won't be moved + * and therefore it's safe to override the skip (based on load) + * of any task we find with that prio. + */ + if (busiest->curr->prio == best_prio) + best_prio_seen = 1; + + rt_rq_iterator.start = load_balance_start_rt; + rt_rq_iterator.next = load_balance_next_rt; + /* pass 'busiest' rq argument into + * load_balance_[start|next]_rt iterators + */ + rt_rq_iterator.arg = busiest; + + nr_moved = balance_tasks(this_rq, this_cpu, busiest, max_nr_move, + max_load_move, sd, idle, all_pinned, load_moved, + this_best_prio, best_prio, best_prio_seen, + &rt_rq_iterator); + + return nr_moved; +} + +static void task_tick_rt(struct rq *rq, struct task_struct *p) +{ + /* + * RR tasks need a special form of timeslice management. + * FIFO tasks have no timeslices. + */ + if (p->policy != SCHED_RR) + return; + + if (--p->time_slice) + return; + + p->time_slice = static_prio_timeslice(p->static_prio); + set_tsk_need_resched(p); + + /* put it at the end of the queue: */ + requeue_task_rt(rq, p); +} + +/* + * No parent/child timeslice management necessary for RT tasks, + * just activate them: + */ +static void task_new_rt(struct rq *rq, struct task_struct *p) +{ + activate_task(rq, p, 1); +} + +static struct sched_class rt_sched_class __read_mostly = { + .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, + + .load_balance = load_balance_rt, + + .task_tick = task_tick_rt, + .task_new = task_new_rt, +}; |