linux-kernel - Re: [PATCH] Watchdog: Checking timeout invalid if hardware heartbeat range is configured

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Date:   Thu, 21 Apr 2022 14:11:06 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Liu Xinpeng <liuxp11@...natelecom.cn>, wim@...ux-watchdog.org
Cc:     linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Watchdog: Checking timeout invalid if hardware heartbeat
 range is configured

On 4/21/22 07:22, Liu Xinpeng wrote:
> The timeout should be invalid when it is out of the hardware
> timeout range.
> 
> ACPI watchdog: Using watchdog_timeout_invalid to check parameter
> timeout invalid
> 
> Signed-off-by: Liu Xinpeng <liuxp11@...natelecom.cn>
> ---
>   drivers/watchdog/wdat_wdt.c |  3 +--
>   include/linux/watchdog.h    | 17 ++++++++++++-----
>   2 files changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/watchdog/wdat_wdt.c b/drivers/watchdog/wdat_wdt.c
> index 195c8c004b69..d166d33ce7ae 100644
> --- a/drivers/watchdog/wdat_wdt.c
> +++ b/drivers/watchdog/wdat_wdt.c
> @@ -450,8 +450,7 @@ static int wdat_wdt_probe(struct platform_device *pdev)
>   	 * watchdog properly after it has opened the device. In some cases
>   	 * the BIOS default is too short and causes immediate reboot.
>   	 */
> -	if (timeout * 1000 < wdat->wdd.min_hw_heartbeat_ms ||
> -	    timeout * 1000 > wdat->wdd.max_hw_heartbeat_ms) {
> +	if (watchdog_timeout_invalid(&wdat->wdd, timeout)) {
>   		dev_warn(dev, "Invalid timeout %d given, using %d\n",
>   			 timeout, WDAT_DEFAULT_TIMEOUT);
>   		timeout = WDAT_DEFAULT_TIMEOUT;
> diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
> index 99660197a36c..e82daeef0b26 100644
> --- a/include/linux/watchdog.h
> +++ b/include/linux/watchdog.h
> @@ -167,6 +167,15 @@ static inline void watchdog_stop_ping_on_suspend(struct watchdog_device *wdd)
>   /* Use the following function to check if a timeout value is invalid */
>   static inline bool watchdog_timeout_invalid(struct watchdog_device *wdd, unsigned int t)
>   {
> +	/*
> +	 * If a maximum/minimum hardware timeout is configured,
> +	 * the timeout is invalid when it is out of the range.
> +	 */
> +	if (wdd->max_hw_heartbeat_ms)
> +		return t * 1000 > wdd->max_hw_heartbeat_ms;
> +	if (wdd->min_hw_heartbeat_ms)
> +		return t * 1000 < wdd->min_hw_heartbeat_ms;
> +

I have no idea what problem you are trying to solve, but this is
completely wrong: It defeats the purpose of having separate minimum
and maximum HW timeouts and configured timeout values. The watchdog
core takes care of those situations.

NACK.

Guenter

>   	/*
>   	 * The timeout is invalid if
>   	 * - the requested value is larger than UINT_MAX / 1000
> @@ -174,13 +183,11 @@ static inline bool watchdog_timeout_invalid(struct watchdog_device *wdd, unsigne
>   	 * or
>   	 * - the requested value is smaller than the configured minimum timeout,
>   	 * or
> -	 * - a maximum hardware timeout is not configured, a maximum timeout
> -	 *   is configured, and the requested value is larger than the
> -	 *   configured maximum timeout.
> +	 * - maximum timeout is configured, and the requested value is larger than
> +	 * the configured maximum timeout.
>   	 */
>   	return t > UINT_MAX / 1000 || t < wdd->min_timeout ||
> -		(!wdd->max_hw_heartbeat_ms && wdd->max_timeout &&
> -		 t > wdd->max_timeout);
> +		(wdd->max_timeout && t > wdd->max_timeout);
>   }
>   
>   /* Use the following function to check if a pretimeout value is invalid */