Re: [PATCH v5 2/2] PM: dpm_watchdog: Allow disabling DPM watchdog by default

[Greg Kroah-Hartman]

On Wed, Jul 01, 2026 at 04:56:40AM +0000, Tzung-Bi Shih wrote:
> Introduce the "dpm_watchdog_enabled" module parameter to allow the DPM
> watchdog to be enabled or disabled at boot time and runtime.

As I say all the time, this isn't the 1990's, please don't add new
module parameters as they are a pain to manage and maintain over time
(as you found out with my rejection of patch 1/2 here...)

> Additionally, introduce the CONFIG_DPM_WATCHDOG_ENABLED Kconfig option
> to set default value of the module parameter at compile time.
> 
> This provides flexibility for systems that want the watchdog code
> compiled in but inactive by default, allowing it to be enabled only when
> needed.
> 
> Signed-off-by: Tzung-Bi Shih <tzungbi@xxxxxxxxxx>
> ---
> v5: No changes.
> 
> v4: https://lore.kernel.org/all/20260611021219.2093476-2-tzungbi@xxxxxxxxxx
> - Rewrite the commit message to indicate the module parameter is the
>   main change in the patch.
> - DPM_WATCHDOG_DEFAULT_ENABLED -> DPM_WATCHDOG_ENABLED.
> 
> v3: https://lore.kernel.org/all/20260608021526.1023248-3-tzungbi@xxxxxxxxxx
> - Add "PM" tag (was missing).
> - Update the format and specify dependencies in kernel-parameters.txt.
> - Update the help message in Kconfig to reflect that dpm_watchdog_enabled
>   can be set at runtime as well.
> 
> v2: https://lore.kernel.org/all/20260604090756.2884671-3-tzungbi@xxxxxxxxxx
> - Use module parameter and bool for dpm_watchdog_enabled.
> - Use IS_ENABLED().
> 
> v1: https://lore.kernel.org/all/20260528103215.505795-1-tzungbi@xxxxxxxxxx
> ---
>  Documentation/admin-guide/kernel-parameters.txt |  7 +++++++
>  drivers/base/power/main.c                       | 11 +++++++++++
>  kernel/power/Kconfig                            | 10 ++++++++++
>  3 files changed, 28 insertions(+)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index b5493a7f8f22..46c20e1b5f05 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -47,6 +47,7 @@
>  	PCI	PCI bus support is enabled.
>  	PCIE	PCI Express support is enabled.
>  	PCMCIA	The PCMCIA subsystem is enabled.
> +	PM	Power Management support is enabled.
>  	PNP	Plug & Play support is enabled.
>  	PPC	PowerPC architecture is enabled.
>  	PPT	Parallel port support is enabled.
> @@ -5354,6 +5355,12 @@ Kernel parameters
>  	pm_debug_messages	[SUSPEND,KNL]
>  			Enable suspend/resume debug messages during boot up.
>  
> +	pm_sleep.dpm_watchdog_enabled=
> +			[PM] Enable or disable the DPM watchdog.  Requires
> +			CONFIG_PM_SLEEP and CONFIG_DPM_WATCHDOG enabled.
> +			Format: <bool>
> +			Default value is set by CONFIG_DPM_WATCHDOG_ENABLED.
> +
>  	pnp.debug=1	[PNP]
>  			Enable PNP debug messages (depends on the
>  			CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index c6a3300cfb7a..f58945758868 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -535,6 +535,11 @@ module_param(dpm_watchdog_all_cpu_backtrace, bool, 0644);
>  MODULE_PARM_DESC(dpm_watchdog_all_cpu_backtrace,
>  		 "Backtrace all CPUs on DPM watchdog timeout");
>  
> +static bool __read_mostly dpm_watchdog_enabled =
> +				IS_ENABLED(CONFIG_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;
> @@ -630,6 +635,9 @@ static void dpm_watchdog_set(struct dpm_watchdog *wd, struct device *dev)
>  {
>  	struct timer_list *timer = &wd->timer;
>  
> +	if (!dpm_watchdog_enabled)
> +		return;
> +
>  	wd->dev = dev;
>  	wd->tsk = current;
>  	wd->fatal = dpm_watchdog_timeout == dpm_watchdog_warning_timeout;
> @@ -648,6 +656,9 @@ static void dpm_watchdog_clear(struct dpm_watchdog *wd)
>  {
>  	struct timer_list *timer = &wd->timer;
>  
> +	if (!dpm_watchdog_enabled)
> +		return;
> +
>  	timer_delete_sync(timer);
>  	timer_destroy_on_stack(timer);
>  }
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 530c897311d4..508ceabc4d2e 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -268,6 +268,16 @@ config DPM_WATCHDOG
>  	  captured in pstore device for inspection in subsequent
>  	  boot session.
>  
> +config DPM_WATCHDOG_ENABLED
> +	bool "Enable DPM watchdog by default"
> +	depends on DPM_WATCHDOG
> +	default y

Only do this if you can not boot without the option enabled, which I do
not think is the case here.

thanks,

greg k-h