linux-kernel - Re: [PATCH] PM / Wakeup / freezer: Check pm_wakeup_pending() before freeze

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Message-ID: <CAJZ5v0ia9k2nht1mnPaMRPt760LQc-5NLbMhmgOZ16phZzKFBQ@mail.gmail.com>
Date: Tue, 15 Apr 2025 20:33:57 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: liuyuan1 <liuyuan1@...o.com>
Cc: rafael@...nel.org, len.brown@...el.com, pavel@...nel.org, 
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	chenzhengding@...o.com
Subject: Re: [PATCH] PM / Wakeup / freezer: Check pm_wakeup_pending() before freeze_task()

On Tue, Mar 18, 2025 at 7:18 AM liuyuan1 <liuyuan1@...o.com> wrote:
>
> Check pm_wakeup_pending() before freeze_task() can reduce
> overhead by not freeze tasks in aborted case. freeze_task()
> will cause high cpu loading especially when system has a large
> number of tasks need to be freeze.
>
> Signed-off-by: liuyuan1 <liuyuan1@...o.com>
> ---
>  kernel/power/process.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/power/process.c b/kernel/power/process.c
> index 66ac067..84704b3 100644
> --- a/kernel/power/process.c
> +++ b/kernel/power/process.c
> @@ -49,6 +49,12 @@ static int try_to_freeze_tasks(bool user_only)
>
>         while (true) {
>                 todo = 0;
> +               if (pm_wakeup_pending()) {
> +                       wakeup = true;
> +                       todo++;

This is going to produce a confusing message below.

> +                       break;
> +               }
> +
>                 read_lock(&tasklist_lock);
>                 for_each_process_thread(g, p) {
>                         if (p == current || !freeze_task(p))
> @@ -66,11 +72,6 @@ static int try_to_freeze_tasks(bool user_only)
>                 if (!todo || time_after(jiffies, end_time))
>                         break;
>
> -               if (pm_wakeup_pending()) {
> -                       wakeup = true;
> -                       break;
> -               }
> -
>                 /*
>                  * We need to retry, but first give the freezing tasks some
>                  * time to enter the refrigerator.  Start with an initial
> --