[PATCH v2] watchdog: new option to skip ping in close

[PATCH v2] watchdog: new option to skip ping in close

[David Teigland]

If a daemon has /dev/watchdog open, and exits (say by crashing or
sigkill), watchdog_release() generates a new watchdog_ping(), extending
the life of the machine.  However, the daemon may require control over
whether or not the watchdog is pinged, and the ping generated by close
compromises this control.

Signed-off-by: David Teigland <teigland@redhat.com>
---
 drivers/watchdog/watchdog_dev.c |    7 ++++++-
 include/linux/watchdog.h        |    2 ++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index ef8edec..47ae7fe 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -394,6 +394,9 @@ static long watchdog_ioctl(struct file *file, unsigned int cmd,
 		if (err)
 			return err;
 		return put_user(val, p);
+	case WDIOC_NOCLOSEPING:
+		set_bit(WDOG_NO_CLOSE_PING, &wdd->status);
+		return 0;
 	default:
 		return -ENOTTY;
 	}
@@ -480,7 +483,9 @@ static int watchdog_release(struct inode *inode, struct file *file)
 		if (!test_bit(WDOG_UNREGISTERED, &wdd->status))
 			dev_crit(wdd->dev, "watchdog did not stop!\n");
 		mutex_unlock(&wdd->lock);
-		watchdog_ping(wdd);
+
+		if (!test_bit(WDOG_NO_CLOSE_PING, &wdd->status))
+			watchdog_ping(wdd);
 	}
 
 	/* Allow the owner module to be unloaded again */
diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
index da70f0f..4fa10ff 100644
--- a/include/linux/watchdog.h
+++ b/include/linux/watchdog.h
@@ -31,6 +31,7 @@ struct watchdog_info {
 #define	WDIOC_SETPRETIMEOUT	_IOWR(WATCHDOG_IOCTL_BASE, 8, int)
 #define	WDIOC_GETPRETIMEOUT	_IOR(WATCHDOG_IOCTL_BASE, 9, int)
 #define	WDIOC_GETTIMELEFT	_IOR(WATCHDOG_IOCTL_BASE, 10, int)
+#define	WDIOC_NOCLOSEPING	_IOR(WATCHDOG_IOCTL_BASE, 11, int)
 
 #define	WDIOF_UNKNOWN		-1	/* Unknown flag error */
 #define	WDIOS_UNKNOWN		-1	/* Unknown status error */
@@ -140,6 +141,7 @@ struct watchdog_device {
 #define WDOG_ALLOW_RELEASE	2	/* Did we receive the magic char ? */
 #define WDOG_NO_WAY_OUT		3	/* Is 'nowayout' feature set ? */
 #define WDOG_UNREGISTERED	4	/* Has the device been unregistered */
+#define WDOG_NO_CLOSE_PING	5	/* Do not ping in watchdog_release() */
 };
 
 #ifdef CONFIG_WATCHDOG_NOWAYOUT
-- 
1.7.10.1.362.g242cab3

Re: [PATCH v2] watchdog: new option to skip ping in close

[Hans de Goede]

Hi,

Code wise this version gets an ACK from me, API wise I'm not sure, so
lets see what Wim Van Sebroeck (the watchdog subsys maintainer) has to
say on this patch.

Regards,

Hans


On 08/07/2012 08:27 PM, David Teigland wrote:
> If a daemon has /dev/watchdog open, and exits (say by crashing or
> sigkill), watchdog_release() generates a new watchdog_ping(), extending
> the life of the machine.  However, the daemon may require control over
> whether or not the watchdog is pinged, and the ping generated by close
> compromises this control.
>
> Signed-off-by: David Teigland <teigland@redhat.com>
> ---
>   drivers/watchdog/watchdog_dev.c |    7 ++++++-
>   include/linux/watchdog.h        |    2 ++
>   2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
> index ef8edec..47ae7fe 100644
> --- a/drivers/watchdog/watchdog_dev.c
> +++ b/drivers/watchdog/watchdog_dev.c
> @@ -394,6 +394,9 @@ static long watchdog_ioctl(struct file *file, unsigned int cmd,
>   		if (err)
>   			return err;
>   		return put_user(val, p);
> +	case WDIOC_NOCLOSEPING:
> +		set_bit(WDOG_NO_CLOSE_PING, &wdd->status);
> +		return 0;
>   	default:
>   		return -ENOTTY;
>   	}
> @@ -480,7 +483,9 @@ static int watchdog_release(struct inode *inode, struct file *file)
>   		if (!test_bit(WDOG_UNREGISTERED, &wdd->status))
>   			dev_crit(wdd->dev, "watchdog did not stop!\n");
>   		mutex_unlock(&wdd->lock);
> -		watchdog_ping(wdd);
> +
> +		if (!test_bit(WDOG_NO_CLOSE_PING, &wdd->status))
> +			watchdog_ping(wdd);
>   	}
>
>   	/* Allow the owner module to be unloaded again */
> diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
> index da70f0f..4fa10ff 100644
> --- a/include/linux/watchdog.h
> +++ b/include/linux/watchdog.h
> @@ -31,6 +31,7 @@ struct watchdog_info {
>   #define	WDIOC_SETPRETIMEOUT	_IOWR(WATCHDOG_IOCTL_BASE, 8, int)
>   #define	WDIOC_GETPRETIMEOUT	_IOR(WATCHDOG_IOCTL_BASE, 9, int)
>   #define	WDIOC_GETTIMELEFT	_IOR(WATCHDOG_IOCTL_BASE, 10, int)
> +#define	WDIOC_NOCLOSEPING	_IOR(WATCHDOG_IOCTL_BASE, 11, int)
>
>   #define	WDIOF_UNKNOWN		-1	/* Unknown flag error */
>   #define	WDIOS_UNKNOWN		-1	/* Unknown status error */
> @@ -140,6 +141,7 @@ struct watchdog_device {
>   #define WDOG_ALLOW_RELEASE	2	/* Did we receive the magic char ? */
>   #define WDOG_NO_WAY_OUT		3	/* Is 'nowayout' feature set ? */
>   #define WDOG_UNREGISTERED	4	/* Has the device been unregistered */
> +#define WDOG_NO_CLOSE_PING	5	/* Do not ping in watchdog_release() */
>   };
>
>   #ifdef CONFIG_WATCHDOG_NOWAYOUT
>