watchdog: new option to skip ping in close

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 <[email protected]>

---
  drivers/watchdog/watchdog_dev.c |    7 ++++++-
  include/linux/watchdog.h        |    2 ++
  2 files changed, 8 insertions(+), 1 deletion(-)

drivers/watchdog/watchdog_dev.c +6 -1

index ef8edec..47ae7fe 100644
@@ -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 */

include/linux/watchdog.h +2 -0

index da70f0f..4fa10ff 100644
@@ -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