linux-kernel - Re: [PATCH] PM: dpm: add module param to backtrace all CPUs

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Message-ID: <CAAFQd5DQGdTSw0k4fX48qO=5XW1phScmSEYw=JmTOMuATcGjog@mail.gmail.com>
Date: Thu, 31 Jul 2025 14:06:32 +0900
From: Tomasz Figa <tfiga@...omium.org>
To: Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Pavel Machek <pavel@...nel.org>, linux-pm@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PM: dpm: add module param to backtrace all CPUs

On Thu, Jul 31, 2025 at 12:01 PM Sergey Senozhatsky
<senozhatsky@...omium.org> wrote:
>
> Add dpm_all_cpu_backtrace module parameter which controls
> all CPU backtrace dump before DPM panics the system.  This
> is expected to help understanding what might have caused
> device timeout.
>
> Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
> ---
>  drivers/base/power/main.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index dbf5456cd891..23abad9f039f 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -34,6 +34,7 @@
>  #include <linux/cpufreq.h>
>  #include <linux/devfreq.h>
>  #include <linux/timer.h>
> +#include <linux/nmi.h>
>
>  #include "../base.h"
>  #include "power.h"
> @@ -517,6 +518,9 @@ struct dpm_watchdog {
>  #define DECLARE_DPM_WATCHDOG_ON_STACK(wd) \
>         struct dpm_watchdog wd
>
> +static bool __read_mostly dpm_all_cpu_backtrace;
> +module_param(dpm_all_cpu_backtrace, bool, 0644);
> +
>  /**
>   * dpm_watchdog_handler - Driver suspend / resume watchdog handler.
>   * @t: The timer that PM watchdog depends on.
> @@ -532,8 +536,12 @@ static void dpm_watchdog_handler(struct timer_list *t)
>         unsigned int time_left;
>
>         if (wd->fatal) {
> +               unsigned int this_cpu = smp_processor_id();
> +
>                 dev_emerg(wd->dev, "**** DPM device timeout ****\n");
>                 show_stack(wd->tsk, NULL, KERN_EMERG);
> +               if (dpm_all_cpu_backtrace)
> +                       trigger_allbutcpu_cpu_backtrace(this_cpu);
>                 panic("%s %s: unrecoverable failure\n",
>                         dev_driver_string(wd->dev), dev_name(wd->dev));
>         }
> --
> 2.50.1.565.gc32cd1483b-goog
>

Reviewed-by: Tomasz Figa <tfiga@...omium.org>

Best,
Tomasz