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Date: Tue, 12 Mar 2024 06:10:38 +0000
From: "levi.yun" <ppbuk5246@gmail.com>
To: hannes@cmpxchg.org, surenb@google.com, peterz@infradead.org,
	mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org,
	dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com,
	mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] psi: Fix avg trigger being fired unexpectedly.
Message-ID: <Ze_x3kovSFe4z9SO@Levi-MacBook-Pro.local>
References: <20240226211237.48415-1-ppbuk5246@gmail.com>
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In-Reply-To: <20240226211237.48415-1-ppbuk5246@gmail.com>

Gentle ping..

On Mon, Feb 26, 2024 at 09:12:37PM +0000, Levi Yun wrote:
> 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: Levi Yun <ppbuk5246@gmail.com>
> Acked-by: Suren Baghdasaryan <surenb@google.com>
> ---
> v2: Fix commit message.
> ---
>  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 7b4aa5809c0f..e7f66ab2ad3e 100644
> --- a/kernel/sched/psi.c
> +++ b/kernel/sched/psi.c
> @@ -1323,9 +1323,6 @@ 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;
> @@ -1336,6 +1333,8 @@ 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;
> @@ -1361,6 +1360,9 @@ 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]++;
>
> --
> 2.39.2