linux-kernel - [PATCH] sched/rt: Add a check for calling update_curr

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Date:   Tue,  6 Nov 2018 23:57:31 +0800
From:   Muchun Song <smuchun@...il.com>
To:     mingo@...nel.org, peterz@...radead.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] sched/rt: Add a check for calling update_curr_rt()

We may dequeue prev's rt_rq in put_prev_task() only when RT
bandwidth is enabled. If RT bandwidth is disabled, it is
unnecessary for us to call update_curr_rt(). So we add a check
there.

Signed-off-by: Muchun Song <smuchun@...il.com>
---
 kernel/sched/rt.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 9aa3287ce301..7761a75d9b87 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1564,10 +1564,11 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 	}
 
 	/*
-	 * We may dequeue prev's rt_rq in put_prev_task().
-	 * So, we update time before rt_queued check.
+	 * We may dequeue prev's rt_rq in put_prev_task()
+	 * only when RT bandwidth is enabled. So, we
+	 * update time before rt_queued check.
 	 */
-	if (prev->sched_class == &rt_sched_class)
+	if (rt_bandwidth_enabled() && prev->sched_class == &rt_sched_class)
 		update_curr_rt(rq);
 
 	if (!rt_rq->rt_queued)
-- 
2.17.1