sched: count # of queued RT tasks

This patch adds accounting to keep track of the number of RT tasks running
on a runqueue. This information will be used in later patches.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/sched.c

@@ -342,6 +342,7 @@ struct rt_rq {
 	struct rt_prio_array active;
 	int rt_load_balance_idx;
 	struct list_head *rt_load_balance_head, *rt_load_balance_curr;
+	unsigned long rt_nr_running;
 };
 
 /*

kernel/sched_rt.c

@@ -26,13 +26,28 @@ static void update_curr_rt(struct rq *rq)
 	cpuacct_charge(curr, delta_exec);
 }
 
+static inline void inc_rt_tasks(struct task_struct *p, struct rq *rq)
+{
+	WARN_ON(!rt_task(p));
+	rq->rt.rt_nr_running++;
+}
+
+static inline void dec_rt_tasks(struct task_struct *p, struct rq *rq)
+{
+	WARN_ON(!rt_task(p));
+	WARN_ON(!rq->rt.rt_nr_running);
+	rq->rt.rt_nr_running--;
+}
+
 static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
 {
 	struct rt_prio_array *array = &rq->rt.active;
 
 	list_add_tail(&p->run_list, array->queue + p->prio);
 	__set_bit(p->prio, array->bitmap);
 	inc_cpu_load(rq, p->se.load.weight);
+
+	inc_rt_tasks(p, rq);
 }
 
 /*
@@ -48,6 +63,8 @@ static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
 	if (list_empty(array->queue + p->prio))
 		__clear_bit(p->prio, array->bitmap);
 	dec_cpu_load(rq, p->se.load.weight);
+
+	dec_rt_tasks(p, rq);
 }
 
 /*