linux-kernel - Re: [PATCHv2] PM: dpm: add module param to backtrace all CPUs

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Message-ID: <CAJZ5v0hBzgJP2L0yg4JtP2c=NxA=MqAY_m+9GJ9P8kszb1hWvw@mail.gmail.com>
Date: Wed, 8 Oct 2025 13:23:33 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Dhruva Gole <d-gole@...com>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>, "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: [PATCHv2] PM: dpm: add module param to backtrace all CPUs

On Wed, Oct 8, 2025 at 12:14 PM Dhruva Gole <d-gole@...com> wrote:
>
> On Oct 07, 2025 at 15:35:40 +0900, Sergey Senozhatsky wrote:
> > Add dpm_watchdog_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.
>
> This will indeed be really helpful for debugging some nasty bugs!
>
> >
> > Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
> > ---
> >  drivers/base/power/main.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> >
> > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> > index e83503bdc1fd..7a8807ec9a5d 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"
> > @@ -515,6 +516,11 @@ struct dpm_watchdog {
> >  #define DECLARE_DPM_WATCHDOG_ON_STACK(wd) \
> >       struct dpm_watchdog wd
> >
> > +static bool __read_mostly dpm_watchdog_all_cpu_backtrace;
> > +module_param(dpm_watchdog_all_cpu_backtrace, bool, 0644);
> > +MODULE_PARM_DESC(dpm_watchdog_all_cpu_backtrace,
> > +              "Backtrace all CPUs on DPM watchdog timeout");
> > +
>
> Have you considered runtime configurability instead of a module param?

This one can be updated at run time AFAICS.