[PATCH 12/20 v3] sched/fair: Support not wakeup case in select_idle_sibling

[Vincent Guittot]

With push callback mecanism, select_task_rq_fair() can be called for a
task that is already enqueued. Task into account this case when choosing
an idle CPU.

Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
---
 kernel/sched/fair.c | 31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f2a0d2c2bb63..980eda9c935a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8187,10 +8187,27 @@ static int choose_sched_idle_rq(struct rq *rq, struct task_struct *p)
 	return sched_idle_rq(rq) && !task_has_idle_policy(p);
 }
 
+static int idle_rq_without(struct rq *rq, struct task_struct *p);
+static unsigned int task_running_on_cpu(int cpu, struct task_struct *p);
+
+static int choose_idle_rq_without(struct rq *rq, struct task_struct *p)
+{
+	if (rq->nr_running != 1)
+		return 0;
+
+	if (!task_running_on_cpu(cpu_of(rq), p))
+		return 0;
+
+	return idle_rq_without(rq, p);
+}
+
 static int choose_idle_cpu(int cpu, struct task_struct *p)
 {
+	struct rq *rq = cpu_rq(cpu);
+
 	return available_idle_cpu(cpu) ||
-	       choose_sched_idle_rq(cpu_rq(cpu), p);
+	       choose_sched_idle_rq(rq, p) ||
+	       choose_idle_rq_without(rq, p);
 }
 
 static void
@@ -12968,23 +12985,21 @@ static unsigned int task_running_on_cpu(int cpu, struct task_struct *p)
 }
 
 /**
- * idle_cpu_without - would a given CPU be idle without p ?
+ * idle_rq_without - would a given CPU be idle without p ?
  * @cpu: the processor on which idleness is tested.
  * @p: task which should be ignored.
  *
  * Return: 1 if the CPU would be idle. 0 otherwise.
  */
-static int idle_cpu_without(int cpu, struct task_struct *p)
+static int idle_rq_without(struct rq *rq, struct task_struct *p)
 {
-	struct rq *rq = cpu_rq(cpu);
-
 	if (rq->curr != rq->idle && rq->curr != p)
 		return 0;
 
 	/*
 	 * rq->nr_running can't be used but an updated version without the
 	 * impact of p on cpu must be used instead. The updated nr_running
-	 * be computed and tested before calling idle_cpu_without().
+	 * be computed and tested before calling idle_rq_without().
 	 */
 
 	if (rq->ttwu_pending)
@@ -13027,9 +13042,9 @@ static inline void update_sg_wakeup_stats(struct sched_domain *sd,
 		sgs->sum_nr_running += nr_running;
 
 		/*
-		 * No need to call idle_cpu_without() if nr_running is not 0
+		 * No need to call idle_rq_without() if nr_running is not 0
 		 */
-		if (!nr_running && idle_cpu_without(i, p))
+		if (!nr_running && idle_rq_without(rq, p))
 			sgs->idle_cpus++;
 
 		/* Check if task fits in the CPU */
-- 
2.53.0