sched: cfs core, kernel/sched_rt.c
add kernel/sched_rt.c: SCHED_FIFO/SCHED_RR support. The behavior
and semantics of SCHED_FIFO/SCHED_RR tasks is unchanged.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
new file mode 100644
index 0000000..1192a27
--- /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,
+};