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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAJZ5v0jAdsyHKsfRtW+Crh_aDY_uryvNekTBivcdPVGAL4UyPQ@mail.gmail.com>
Date: Tue, 19 Aug 2025 21:35:04 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Pavel Machek <pavel@...nel.org>, 
	Tomasz Figa <tfiga@...omium.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 5:01 AM 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 exclusively about the DPM watchdog, so the module parameter
name should reflect that.

Also, it is not quite clear which module this is going to belong to,
so a comment with this information would be helpful.

> 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
>