[PATCH v4 1/2] sched/fair: set rq->idle_stamp at the end of the sched_balance_newidle

[Huang Shijie <shijie@os.amperecomputing.com>]

Save the idle_stamp at the beginning of sched_balance_newidle(),
if it cannot pull any task, set it for rq->idle_stamp.

This patch does not change the logic of rq->idle_stamp.

Signed-off-by: Huang Shijie <shijie@os.amperecomputing.com>
---
 kernel/sched/fair.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 769d7b7990df..c1a8fa043156 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12862,6 +12862,7 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
 	u64 t0, t1, curr_cost = 0;
 	struct sched_domain *sd;
 	int pulled_task = 0;
+	u64 idle_stamp;
 
 	update_misfit_status(NULL, this_rq);
 
@@ -12877,7 +12878,9 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
 	 * for CPU_NEWLY_IDLE, such that we measure the this duration
 	 * as idle time.
 	 */
-	this_rq->idle_stamp = rq_clock(this_rq);
+	idle_stamp = rq_clock(this_rq);
+
+	this_rq->idle_stamp = 0;
 
 	/*
 	 * Do not pull tasks towards !active CPUs...
@@ -12989,10 +12992,11 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
 	if (time_after(this_rq->next_balance, next_balance))
 		this_rq->next_balance = next_balance;
 
-	if (pulled_task)
-		this_rq->idle_stamp = 0;
-	else
+	if (!pulled_task) {
+		/* Set it here on purpose. */
+		this_rq->idle_stamp = idle_stamp;
 		nohz_newidle_balance(this_rq);
+	}
 
 	rq_repin_lock(this_rq, rf);
 
-- 
2.40.1