Re: [PATCH v3 3/3] PM: dpm_watchdog: Add sysctl interface for DPM watchdog timeouts

[Rafael J. Wysocki]

On Tue, Jun 9, 2026 at 11:02 AM Tzung-Bi Shih <tzungbi@xxxxxxxxxx> wrote:
>
> On Mon, Jun 08, 2026 at 04:22:35PM +0200, Rafael J. Wysocki wrote:
> > On Mon, Jun 8, 2026 at 4:16 AM Tzung-Bi Shih <tzungbi@xxxxxxxxxx> wrote:
> > >
> > > Introduce sysctl knobs to allow configuring DPM watchdog timeouts at
> > > runtime.
> > >
> > > Currently, these timeouts are fixed at compile time via
> > > CONFIG_DPM_WATCHDOG_TIMEOUT and CONFIG_DPM_WATCHDOG_WARNING_TIMEOUT.
> > > This limits flexibility if the timeouts need to be adjusted for
> > > different testing scenarios or hardware behaviors without rebuilding
> > > the kernel.
> > >
> > > Add the following sysctl files under /proc/sys/kernel/:
> > > - dpm_watchdog_timeout_secs: The total timeout before panic. The
> > >   maximum value is capped at CONFIG_DPM_WATCHDOG_TIMEOUT to prevent
> > >   unreasonably large timeouts.
> > > - dpm_watchdog_warning_timeout_secs: The warning timeout. The maximum
> > >   value is capped at the current dpm_watchdog_timeout_secs.
> > > Both sysctls have a minimum value of 1.
> > >
> > > Signed-off-by: Tzung-Bi Shih <tzungbi@xxxxxxxxxx>
> > > ---
> > > v3:
> > > - No changes.
> > >
> > > v2: https://lore.kernel.org/all/20260604090756.2884671-4-tzungbi@xxxxxxxxxx
> > > - New to the series.
> > >
> > > v1: Doesn't exist.
> > >
> > >  drivers/base/power/main.c | 61 ++++++++++++++++++++++++++++++++++++---
> > >  1 file changed, 57 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> > > index 7822c29b7c8d..c1a4b30fafb2 100644
> > > --- a/drivers/base/power/main.c
> > > +++ b/drivers/base/power/main.c
> > > @@ -28,6 +28,7 @@
> > >  #include <linux/interrupt.h>
> > >  #include <linux/sched.h>
> > >  #include <linux/sched/debug.h>
> > > +#include <linux/sysctl.h>
> > >  #include <linux/async.h>
> > >  #include <linux/suspend.h>
> > >  #include <trace/events/power.h>
> > > @@ -539,6 +540,58 @@ static bool __read_mostly dpm_watchdog_enabled =
> > >  module_param(dpm_watchdog_enabled, bool, 0644);
> > >  MODULE_PARM_DESC(dpm_watchdog_enabled, "Enable DPM watchdog");
> > >
> > > +static unsigned int __read_mostly dpm_watchdog_timeout = CONFIG_DPM_WATCHDOG_TIMEOUT;
> > > +static unsigned int __read_mostly dpm_watchdog_warning_timeout =
> > > +                                               CONFIG_DPM_WATCHDOG_WARNING_TIMEOUT;
> > > +static const unsigned int dpm_watchdog_timeout_max = CONFIG_DPM_WATCHDOG_TIMEOUT;
> > > +
> > > +static int proc_dodpm_watchdog_timeout_secs(const struct ctl_table *table,
> > > +                                           int write, void *buffer,
> > > +                                           size_t *lenp, loff_t *ppos)
> > > +{
> > > +       struct ctl_table ctl = *table;
> > > +       unsigned int val = dpm_watchdog_timeout;
> > > +       int ret;
> > > +
> > > +       ctl.data = &val;
> > > +       ret = proc_douintvec_minmax(&ctl, write, buffer, lenp, ppos);
> > > +       if (ret || !write)
> > > +               return ret;
> > > +
> > > +       if (val < dpm_watchdog_warning_timeout)
> > > +               dpm_watchdog_warning_timeout = val;
> > > +       dpm_watchdog_timeout = val;
> > > +
> > > +       return 0;
> > > +}
> > > +
> > > +static const struct ctl_table dpm_watchdog_sysctls[] = {
> > > +       {
> > > +               .procname       = "dpm_watchdog_timeout_secs",
> > > +               .maxlen         = sizeof(unsigned int),
> > > +               .mode           = 0644,
> > > +               .proc_handler   = proc_dodpm_watchdog_timeout_secs,
> > > +               .extra1         = SYSCTL_ONE,
> > > +               .extra2         = (void *)&dpm_watchdog_timeout_max,
> > > +       },
> > > +       {
> > > +               .procname       = "dpm_watchdog_warning_timeout_secs",
> > > +               .data           = &dpm_watchdog_warning_timeout,
> > > +               .maxlen         = sizeof(unsigned int),
> > > +               .mode           = 0644,
> > > +               .proc_handler   = proc_douintvec_minmax,
> > > +               .extra1         = SYSCTL_ONE,
> > > +               .extra2         = (void *)&dpm_watchdog_timeout,
> > > +       },
> > > +};
> > > +
> > > +static int __init dpm_watchdog_sysctl_init(void)
> > > +{
> > > +       register_sysctl_init("kernel", dpm_watchdog_sysctls);
> > > +       return 0;
> > > +}
> > > +subsys_initcall(dpm_watchdog_sysctl_init);
> > > +
> > >  /**
> > >   * dpm_watchdog_handler - Driver suspend / resume watchdog handler.
> > >   * @t: The timer that PM watchdog depends on.
> > > @@ -564,9 +617,9 @@ static void dpm_watchdog_handler(struct timer_list *t)
> > >                         dev_driver_string(wd->dev), dev_name(wd->dev));
> > >         }
> > >
> > > -       time_left = CONFIG_DPM_WATCHDOG_TIMEOUT - CONFIG_DPM_WATCHDOG_WARNING_TIMEOUT;
> > > +       time_left = dpm_watchdog_timeout - dpm_watchdog_warning_timeout;
> > >         dev_warn(wd->dev, "**** DPM device timeout after %u seconds; %u seconds until panic ****\n",
> > > -                CONFIG_DPM_WATCHDOG_WARNING_TIMEOUT, time_left);
> > > +                dpm_watchdog_warning_timeout, time_left);
> > >         show_stack(wd->tsk, NULL, KERN_WARNING);
> > >
> > >         wd->fatal = true;
> > > @@ -587,11 +640,11 @@ static void dpm_watchdog_set(struct dpm_watchdog *wd, struct device *dev)
> > >
> > >         wd->dev = dev;
> > >         wd->tsk = current;
> > > -       wd->fatal = CONFIG_DPM_WATCHDOG_TIMEOUT == CONFIG_DPM_WATCHDOG_WARNING_TIMEOUT;
> > > +       wd->fatal = dpm_watchdog_timeout == dpm_watchdog_warning_timeout;
> > >
> > >         timer_setup_on_stack(timer, dpm_watchdog_handler, 0);
> > >         /* use same timeout value for both suspend and resume */
> > > -       timer->expires = jiffies + HZ * CONFIG_DPM_WATCHDOG_WARNING_TIMEOUT;
> > > +       timer->expires = jiffies + HZ * dpm_watchdog_warning_timeout;
> > >         add_timer(timer);
> > >  }
> > >
> > > --
> >
> > I think that this can be applied without the other two patches in the
> > series, so please let me know if you want me to apply it separately.
>
> Ack.  The patch does have adjacent hunks with the preceding patch, which
> might cause minor contextual conflicts if applied independently.

That's not a problem.

> Would you want me to reorder the series in the next version to make this
> the first patch?  In case the rest two patches may still take some time
> to review.

I'll pick it up as is, so it can make it into 7.2.