linux-kernel - [RFC PATCH 2/2] sched/idle: Add a description for play_idle

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Message-Id: <20240410045417.3048209-3-quic_atulpant@quicinc.com>
Date: Wed, 10 Apr 2024 10:24:17 +0530
From: Atul Pant <quic_atulpant@...cinc.com>
To: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com, rafael@...nel.org,
        daniel.lezcano@...aro.org
Cc: Atul Pant <quic_atulpant@...cinc.com>, kernel@...cinc.com,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: [RFC PATCH 2/2] sched/idle: Add a description for play_idle_precise

Since runtime accounting of any RT idle thread is prevented, add a
description about this function that it runs idle loops on a cpu
without these threads being preempted due to RT throttling.

Signed-off-by: Atul Pant <quic_atulpant@...cinc.com>
---
 kernel/sched/idle.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 5007b25c5bc6..7aaf3679f50a 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -334,6 +334,11 @@ static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer)
 	return HRTIMER_NORESTART;
 }
 
+/*
+ * This function runs idle loops on a cpu, whose policy is set as SCHED_FIFO.
+ * Despite being a rt thread, runtime for it is not accounted, thus preventing
+ * its preemption due to rt-throttling
+ */
 void play_idle_precise(u64 duration_ns, u64 latency_ns)
 {
 	struct idle_timer it;
-- 
2.25.1