2.6.18 have watchdog thread woken by timer interrupt, instead
of hooking on timer wheel like 2.6.16. In this case, we need
change next_timer_interrupt to consider watchdog event in case
idle process decides to block a long time. This can effectively
fix the softlockup warning seen intermittently.

Signed-off-by Kevin Tian <kevin.tian@intel.com>

diff -r b3cca2636741 -r 99d1480afae8 linux-2.6-xen-sparse/include/linux/sched.h
--- a/linux-2.6-xen-sparse/include/linux/sched.h	Fri Feb 02 15:32:45 2007 +0800
+++ b/linux-2.6-xen-sparse/include/linux/sched.h	Fri Feb 02 21:08:49 2007 +0800
@@ -211,10 +211,15 @@ extern void scheduler_tick(void);
 extern void scheduler_tick(void);
 
 #ifdef CONFIG_DETECT_SOFTLOCKUP
+extern unsigned long softlockup_get_next_event(unsigned long expire);
 extern void softlockup_tick(void);
 extern void spawn_softlockup_task(void);
 extern void touch_softlockup_watchdog(void);
 #else
+static inline unsigned long softlockup_get_next_event(unsigned long expire)
+{
+	return expire;
+}
 static inline void softlockup_tick(void)
 {
 }
diff -r b3cca2636741 -r 99d1480afae8 linux-2.6-xen-sparse/kernel/softlockup.c
--- a/linux-2.6-xen-sparse/kernel/softlockup.c	Fri Feb 02 15:32:45 2007 +0800
+++ b/linux-2.6-xen-sparse/kernel/softlockup.c	Fri Feb 02 21:08:49 2007 +0800
@@ -40,6 +40,19 @@ void touch_softlockup_watchdog(void)
 }
 EXPORT_SYMBOL(touch_softlockup_watchdog);
 
+unsigned long softlockup_get_next_event(unsigned long expire)
+{
+	if (time_before(expire, jiffies + HZ) ||
+		did_panic ||
+			!per_cpu(watchdog_task, smp_processor_id()))
+		return expire;
+
+	/* Limit expire duration to maximum 1s, to allow watchdog
+	 * thread waken up appropriately by timer interrupt.
+	 */
+	return jiffies + HZ;
+}
+
 /*
  * This callback runs from the timer interrupt, and checks
  * whether the watchdog thread has hung or not:
diff -r b3cca2636741 -r 99d1480afae8 linux-2.6-xen-sparse/kernel/timer.c
--- a/linux-2.6-xen-sparse/kernel/timer.c	Fri Feb 02 15:32:45 2007 +0800
+++ b/linux-2.6-xen-sparse/kernel/timer.c	Fri Feb 02 21:08:49 2007 +0800
@@ -482,8 +482,10 @@ unsigned long next_timer_interrupt(void)
 		struct timespec tsdelta;
 		tsdelta = ktime_to_timespec(hr_delta);
 		hr_expires = timespec_to_jiffies(&tsdelta);
-		if (hr_expires < 3)
-			return hr_expires + jiffies;
+		if (hr_expires < 3) {
+			expires = hr_expires + jiffies;
+			goto done;
+		}
 	}
 	hr_expires += jiffies;
 
@@ -555,9 +557,11 @@ found:
 		return jiffies;
 
 	if (time_before(hr_expires, expires))
-		return hr_expires;
-
-	return expires;
+		expires = hr_expires;
+
+done:
+	/* Assure watchdog thread not blocked by tick-less model */
+	return softlockup_get_next_event(expires);
 }
 #endif