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

[Rafael J. Wysocki]

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.

Thanks!