[PATCH] generic: vsyscall-gtod support for GENERIC_TIME

Provides generic infrastructure for vsyscall-gtod.

[akpm@osdl.org: cleanup]
Signed-off-by: NJohn 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: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/linux/clocksource.h

@@ -47,6 +47,7 @@ struct clocksource;
  * @mult:		cycle to nanosecond multiplier
  * @shift:		cycle to nanosecond divisor (power of two)
  * @flags:		flags describing special properties
+ * @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 mult;
 	u32 shift;
 	unsigned long flags;
+	cycle_t (*vread)(void);
 
 	/* timekeeping specific data, ignore */
 	cycle_t cycle_last, cycle_interval;
@@ -197,4 +199,12 @@ extern int clocksource_register(struct clocksource*);
 extern struct clocksource* clocksource_get_next(void);
 extern void clocksource_change_rating(struct clocksource *cs, int rating);
 
+#ifdef CONFIG_GENERIC_TIME_VSYSCALL
+extern void update_vsyscall(struct timespec *ts, struct clocksource *c);
+#else
+static inline void update_vsyscall(struct timespec *ts, struct clocksource *c)
+{
+}
+#endif
+
 #endif /* _LINUX_CLOCKSOURCE_H */

kernel/timer.c

@@ -1174,6 +1174,7 @@ static void update_wall_time(void)
 
 	/* check to see if there is a new clocksource to use */
 	change_clocksource();
+	update_vsyscall(&xtime, clock);
 }
 
 /*