linux-kernel - Re: [PATCH v2 2/4] PM: freezer: Print tasks stuck in D-state during freeze

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Message-ID: <CAJZ5v0hyBg3mVhfERkTLUnARLrsGarvtKOnL=RrL9VGF5DNLsg@mail.gmail.com>
Date: Thu, 3 Jul 2025 16:40:15 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Zihuan Zhang <zhangzihuan@...inos.cn>
Cc: rafael@...nel.org, pavel@...nel.org, len.brown@...el.com, 
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] PM: freezer: Print tasks stuck in D-state during freeze

On Thu, Jun 19, 2025 at 5:54 AM Zihuan Zhang <zhangzihuan@...inos.cn> wrote:
>
> To help diagnose freezing delays caused by tasks stuck in D-state, this
> patch adds logging for tasks that are stuck in D-state during each retry
> of the freezer loop.  Such tasks are not killable and cannot be frozen,
> which can cause the system suspend process to retry many times
> before aborting.  This message can help developers identify which
> user-space or kernel tasks are blocking the freeze process.
>
> Signed-off-by: Zihuan Zhang <zhangzihuan@...inos.cn>
> ---
>  kernel/power/process.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/kernel/power/process.c b/kernel/power/process.c
> index 87616ca710ac..4007f621c2ad 100644
> --- a/kernel/power/process.c
> +++ b/kernel/power/process.c
> @@ -55,6 +55,9 @@ static int try_to_freeze_tasks(bool user_only)
>                         if (p == current || !freeze_task(p))
>                                 continue;
>
> +                       if (retry > 1 && READ_ONCE(p->__state) == TASK_UNINTERRUPTIBLE)
> +                               sched_show_task(p);
> +

This is going to be too noisy IMV.  Any chance to rate limit it somehow?

>                         todo++;
>                 }
>                 read_unlock(&tasklist_lock);
> --
> 2.25.1
>