linux-kernel - [PATCH v3] psi: fix avg trigger being fired unexpectedly.

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Message-Id: <20250710071128.1637175-1-yeoreum.yun@arm.com>
Date: Thu, 10 Jul 2025 08:11:28 +0100
From: Yeoreum Yun <yeoreum.yun@....com>
To: hannes@...xchg.org,
	surenb@...gle.com,
	peterz@...radead.org,
	mingo@...hat.com,
	juri.lelli@...hat.com,
	vincent.guittot@...aro.org,
	dietmar.eggemann@....com,
	rostedt@...dmis.org,
	bsegall@...gle.com,
	mgorman@...e.de,
	vschneid@...hat.com
Cc: linux-kernel@...r.kernel.org,
	Yeoreum Yun <yeoreum.yun@....com>
Subject: [PATCH v3] psi: fix avg trigger being fired unexpectedly.

commit 915a087e4c473("psi: Fix trigger being fired unexpectedly at initial")
fixes unexpected event fired when group->total accumulated for PSI_POLL.
But, for PSI_AVGS, win->value should be initialized with group->total[PSI_AVGS].
Moreover, to get exact initial value for win->value, it should be set
under each trigger lock to avoid concurrent changes to group->total[].

Signed-off-by: Yeoreum Yun <yeoreum.yun@....com>
Acked-by: Suren Baghdasaryan <surenb@...gle.com>
---
Patch History
=============
from v2 to v3:
  - change author
  - rebase to v6.16-rc5
  - https://lore.kernel.org/all/20240226211237.48415-1-ppbuk5246@gmail.com/

from v1 to v2:
  - fix commit message
  - https://lore.kernel.org/all/20240226194642.47530-1-ppbuk5246@gmail.com/#t
---
 kernel/sched/psi.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index ad04a5c3162a..00cf7acb5eb3 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -1337,9 +1337,6 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, char *buf,
 	t->state = state;
 	t->threshold = threshold_us * NSEC_PER_USEC;
 	t->win.size = window_us * NSEC_PER_USEC;
-	window_reset(&t->win, sched_clock(),
-			group->total[PSI_POLL][t->state], 0);
-
 	t->event = 0;
 	t->last_event_time = 0;
 	t->of = of;
@@ -1350,6 +1347,8 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, char *buf,

 	if (privileged) {
 		mutex_lock(&group->rtpoll_trigger_lock);
+		window_reset(&t->win, sched_clock(),
+				group->total[PSI_POLL][t->state], 0);

 		if (!rcu_access_pointer(group->rtpoll_task)) {
 			struct task_struct *task;
@@ -1375,6 +1374,9 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, char *buf,
 	} else {
 		mutex_lock(&group->avgs_lock);

+		window_reset(&t->win, sched_clock(),
+				group->total[PSI_AVGS][t->state], 0);
+
 		list_add(&t->node, &group->avg_triggers);
 		group->avg_nr_triggers[t->state]++;

--
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}