Generic part of an interface to allow debuggers to update time after
having halted the system for perhaps extended periods of time. This
generally requires arch-dependent changes, too, unless the arch-
dependent time handling is already overflow-safe.

Signed-Off-By: Jan Beulich <jbeulich@novell.com>

Index: 2.6.14-nlkd/include/linux/jiffies.h
===================================================================
--- 2.6.14-nlkd.orig/include/linux/jiffies.h	2005-11-09 10:40:17.000000000 +0100
+++ 2.6.14-nlkd/include/linux/jiffies.h	2005-11-04 16:19:34.000000000 +0100
@@ -83,6 +83,11 @@
  */
 extern u64 __jiffy_data jiffies_64;
 extern unsigned long volatile __jiffy_data jiffies;
+#ifndef CONFIG_DEBUG_KERNEL
+# define debugger_jiffies 0
+#else
+extern u64 debugger_jiffies;
+#endif
 
 #if (BITS_PER_LONG < 64)
 u64 get_jiffies_64(void);
Index: 2.6.14-nlkd/kernel/timer.c
===================================================================
--- 2.6.14-nlkd.orig/kernel/timer.c	2005-11-09 10:40:17.000000000 +0100
+++ 2.6.14-nlkd/kernel/timer.c	2005-11-07 15:20:27.000000000 +0100
@@ -46,6 +46,10 @@ static void time_interpolator_update(lon
 #define time_interpolator_update(x)
 #endif
 
+#ifdef CONFIG_DEBUG_KERNEL
+u64 debugger_jiffies;
+#endif
+
 /*
  * per-CPU timer vector definitions:
  */
@@ -935,6 +939,28 @@ static inline void update_times(void)
 	ticks = jiffies - wall_jiffies;
 	if (ticks) {
 		wall_jiffies += ticks;
+#ifndef debugger_jiffies
+		if (ticks > 1
+		    && debugger_jiffies
+		    && jiffies_64 - debugger_jiffies > 1) {
+			u64 nsec64 = (u64)(ticks - 1) * tick_nsec;
+			unsigned long nsec = do_div(nsec64, NSEC_PER_SEC);
+			unsigned long sec = nsec64;
+
+			if (sec > 0
+			    && xtime.tv_nsec + nsec + tick_nsec < NSEC_PER_SEC) {
+				/* Make sure xtime.tv_nsec exceeds a second when
+				   checked (in update_wall_time). */
+				sec--;
+				nsec += NSEC_PER_SEC;
+			}
+			xtime.tv_sec += sec;
+			xtime.tv_nsec += nsec;
+			touch_softlockup_watchdog();
+			ticks = 1;
+		}
+		debugger_jiffies = 0;
+#endif
 		update_wall_time(ticks);
 	}
 	calc_load(ticks);