- Add the possibility to reuse the already last used timeout when patting

  the watchdog, via the watchdog(9) interface.
  For that, the WD_LASTVAL bitwise operation is used. It is mutually
  exclusive with any explicit timout passing to the watchdogs.
  The last timeout can be returned via the wdog_kern_last_timeout()
  KPI.
- Add the possibility to pat the watchdogs installed via the watchdog(9)
  interface from the kernel.
  In order to do that the new KPI wdog_kern_pat() is offered and it does
  accept normalized nanoseconds or WD_LASTVAL.
- Avoid to pass WD_ACTIVE down in the watchdog handlers. All the control
  bit processing should over to the upper layer functions and not passed
  down to the handlers at all.

These changes are intended to be used in order to fix up the watchdog
tripping in situation when the userland is busted, but protection is still
wanted (examples: shutdown syncing / disk dumping).

Sponsored by:	Sandvine Incorporated
Reviewed by:	emaste, des, cognet
MFC after:	2 weeks

3 files changed, 60 insertions, 21 deletions

diff --git a/sys/ddb/db_command.c b/sys/ddb/db_command.c
index d8c8cb006a31..21cb7c5940de 100644
--- a/sys/ddb/db_command.c
+++ b/sys/ddb/db_command.c
@@ -724,14 +724,6 @@ db_watchdog(dummy1, dummy2, dummy3, dummy4)
 	} else if ((tout & WD_INTERVAL) == WD_TO_NEVER) {
 		db_error("Out of range watchdog interval\n");
 		return;
-	} else {
-
-		/*
-		 * XXX: Right now we only support WD_ACTIVE, in the future we
-		 * may be possibly needing a more convoluted function for
-		 * dealing with different cases.
-		 */
-		tout |= WD_ACTIVE;
 	}
 	EVENTHANDLER_INVOKE(watchdog_list, tout, &i);
 }
diff --git a/sys/dev/watchdog/watchdog.c b/sys/dev/watchdog/watchdog.c
index 06498c956c9c..e7edf31c4b7a 100644
--- a/sys/dev/watchdog/watchdog.c
+++ b/sys/dev/watchdog/watchdog.c
@@ -40,35 +40,73 @@ __FBSDID("$FreeBSD$");
 #include <machine/bus.h>
 
 static struct cdev *wd_dev;
+static volatile u_int wd_last_u;
+
+static int
+kern_do_pat(u_int utim)
+{
+	int error;
+
+	if ((utim & WD_LASTVAL) != 0 && (utim & WD_INTERVAL) > 0)
+		return (EINVAL);
+
+	if ((utim & WD_LASTVAL) != 0) {
+		MPASS((wd_last_u & ~WD_INTERVAL) == 0);
+		utim &= ~WD_LASTVAL;
+		utim |= wd_last_u;
+	} else
+		wd_last_u = (utim & WD_INTERVAL);
+	if ((utim & WD_INTERVAL) == WD_TO_NEVER) {
+		utim = 0;
+
+		/* Assume all is well; watchdog signals failure. */
+		error = 0;
+	} else {
+		/* Assume no watchdog available; watchdog flags success */
+		error = EOPNOTSUPP;
+	}
+	EVENTHANDLER_INVOKE(watchdog_list, utim, &error);
+	return (error);
+}
 
 static int
 wd_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data,
     int flags __unused, struct thread *td)
 {
-	int error;
 	u_int u;
 
 	if (cmd != WDIOCPATPAT)
 		return (ENOIOCTL);
 	u = *(u_int *)data;
-	if (u & ~(WD_ACTIVE | WD_PASSIVE | WD_INTERVAL))
+	if (u & ~(WD_ACTIVE | WD_PASSIVE | WD_LASTVAL | WD_INTERVAL))
 		return (EINVAL);
 	if ((u & (WD_ACTIVE | WD_PASSIVE)) == (WD_ACTIVE | WD_PASSIVE))
 		return (EINVAL);
-	if ((u & (WD_ACTIVE | WD_PASSIVE)) == 0 && (u & WD_INTERVAL) > 0)
+	if ((u & (WD_ACTIVE | WD_PASSIVE)) == 0 && ((u & WD_INTERVAL) > 0 ||
+	    (u & WD_LASTVAL) != 0))
 		return (EINVAL);
 	if (u & WD_PASSIVE)
 		return (ENOSYS);	/* XXX Not implemented yet */
-	if ((u & WD_INTERVAL) == WD_TO_NEVER) {
-		u = 0;
-		/* Assume all is well; watchdog signals failure. */
-		error = 0;
-	} else {
-		/* Assume no watchdog available; watchdog flags success */
-		error = EOPNOTSUPP;
-	}
-	EVENTHANDLER_INVOKE(watchdog_list, u, &error);
-	return (error);
+	u &= ~(WD_ACTIVE | WD_PASSIVE);
+
+	return (kern_do_pat(u));
+}
+
+u_int
+wdog_kern_last_timeout(void)
+{
+
+	return (wd_last_u);
+}
+
+int
+wdog_kern_pat(u_int utim)
+{
+
+	if (utim & ~(WD_LASTVAL | WD_INTERVAL))
+		return (EINVAL);
+
+	return (kern_do_pat(utim));
 }
 
 static struct cdevsw wd_cdevsw = {
diff --git a/sys/sys/watchdog.h b/sys/sys/watchdog.h
index 941077593384..ba58a7c69a5d 100644
--- a/sys/sys/watchdog.h
+++ b/sys/sys/watchdog.h
@@ -50,6 +50,12 @@
 	 * right to the kernel.
  	 */
 
+#define WD_LASTVAL	0x0200000
+	/*
+	 * Use the already last used timeout value.
+	 * The kernel will use as timeout the last valid timeout provided.
+ 	 */
+
 #define WD_INTERVAL	0x00000ff
 	/*
 	 * Mask for duration bits.
@@ -78,6 +84,9 @@
 typedef void (*watchdog_fn)(void *, u_int, int *);
 
 EVENTHANDLER_DECLARE(watchdog_list, watchdog_fn);
+
+u_int	wdog_kern_last_timeout(void);
+int	wdog_kern_pat(u_int utim);
 #endif
 
 #endif /* _SYS_WATCHDOG_H */