linux-kernel - [PATCH] sched/rt: fix incorrect schedstats for rt thread

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Message-ID: <20260108031309.2754003-1-dengjun.su@mediatek.com>
Date: Thu, 8 Jan 2026 11:13:07 +0800
From: Dengjun Su <dengjun.su@...iatek.com>
To: <linux-kernel@...r.kernel.org>
CC: <dengjun.su@...iatek.com>, <mike.zhang@...iatek.com>,
	<haiqiang.gong@...iatek.com>, <peijun.huang@...iatek.com>, Ingo Molnar
	<mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Juri Lelli
	<juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt
	<rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman
	<mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>, Matthias Brugger
	<matthias.bgg@...il.com>, AngeloGioacchino Del Regno
	<angelogioacchino.delregno@...labora.com>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-mediatek@...ts.infradead.org>
Subject: [PATCH] sched/rt: fix incorrect schedstats for rt thread

For RT thread, only 'set_next_task_rt' will call
'update_stats_wait_end_rt' to update schedstats information.
However, during the RT migration process,
'update_stats_wait_start_rt' will be called twice, which
will cause the values of wait_max and wait_sum to be incorrect.
The specific output as follows:
$ cat /proc/6046/task/6046/sched | grep wait
wait_start                                   :             0.000000
wait_max                                     :        496717.080029
wait_sum                                     :       7921540.776553

Add 'update_stats_wait_end_rt' in 'update_stats_dequeue_rt' to
update schedstats information when dequeue_task.

Signed-off-by: Dengjun Su <dengjun.su@...iatek.com>
---
 kernel/sched/rt.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index f1867fe8e5c5..12f2efddca9f 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1302,13 +1302,18 @@ update_stats_dequeue_rt(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se,
 			int flags)
 {
 	struct task_struct *p = NULL;
+	struct rq *rq = rq_of_rt_rq(rt_rq);
 
 	if (!schedstat_enabled())
 		return;
 
-	if (rt_entity_is_task(rt_se))
+	if (rt_entity_is_task(rt_se)) {
 		p = rt_task_of(rt_se);
 
+		if (p != rq->curr)
+			update_stats_wait_end_rt(rt_rq, rt_se);
+	}
+
 	if ((flags & DEQUEUE_SLEEP) && p) {
 		unsigned int state;
 
-- 
2.43.0