From: john stultz <johnstul@us.ibm.com>

Provides generic infrastructure for vsyscall-gtod.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andi Kleen <ak@muc.de>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 include/linux/clocksource.h |    8 ++++++++
 kernel/timer.c              |    1 +
 2 files changed, 9 insertions(+)

diff -puN include/linux/clocksource.h~generic-vsyscall-gtod-support-for-generic_time include/linux/clocksource.h
--- a/include/linux/clocksource.h~generic-vsyscall-gtod-support-for-generic_time
+++ a/include/linux/clocksource.h
@@ -46,6 +46,7 @@ typedef u64 cycle_t;
  * @shift:		cycle to nanosecond divisor (power of two)
  * @update_callback:	called when safe to alter clocksource values
  * @is_continuous:	defines if clocksource is free-running.
+ * @vread:		vsyscall based read
  * @cycle_interval:	Used internally by timekeeping core, please ignore.
  * @xtime_interval:	Used internally by timekeeping core, please ignore.
  */
@@ -59,6 +60,7 @@ struct clocksource {
 	u32 shift;
 	int (*update_callback)(void);
 	int is_continuous;
+	cycle_t (*vread)(void);
 
 	/* timekeeping specific data, ignore */
 	cycle_t cycle_last, cycle_interval;
@@ -182,4 +184,10 @@ int clocksource_register(struct clocksou
 void clocksource_reselect(void);
 struct clocksource* clocksource_get_next(void);
 
+#ifdef CONFIG_GENERIC_TIME_VSYSCALL
+extern void update_vsyscall(struct timespec *ts, struct clocksource *c);
+#else
+#define update_vsyscall(now, c) do { } while(0)
+#endif
+
 #endif /* _LINUX_CLOCKSOURCE_H */
diff -puN kernel/timer.c~generic-vsyscall-gtod-support-for-generic_time kernel/timer.c
--- a/kernel/timer.c~generic-vsyscall-gtod-support-for-generic_time
+++ a/kernel/timer.c
@@ -1199,6 +1199,7 @@ static void update_wall_time(void)
 		hrtimer_clock_notify();
 		clocksource_calculate_interval(clock, tick_nsec);
 	}
+	update_vsyscall(&xtime, clock);
 }
 
 /*
_