timekeeping: update xtime_cache when time(zone) changes

xtime_cache needs to be updated whenever xtime and or wall_to_monotic
are changed. Otherwise users of xtime_cache might see a stale (and in
the case of timezone changes utterly wrong) value until the next
update happens.

Fixup the obvious places, which miss this update.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <johnstul@us.ibm.com>
Tested-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/time.h

@@ -122,6 +122,7 @@ extern void monotonic_to_bootbased(struct timespec *ts);
 extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
 extern int timekeeping_is_continuous(void);
 extern void update_wall_time(void);
+extern void update_xtime_cache(u64 nsec);
 
 /**
  * timespec_to_ns - Convert timespec to nanoseconds

kernel/time.c

@@ -129,6 +129,7 @@ static inline void warp_clock(void)
 	write_seqlock_irq(&xtime_lock);
 	wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60;
 	xtime.tv_sec += sys_tz.tz_minuteswest * 60;
+	update_xtime_cache(0);
 	write_sequnlock_irq(&xtime_lock);
 	clock_was_set();
 }

kernel/time/timekeeping.c

@@ -47,7 +47,7 @@ struct timespec wall_to_monotonic __attribute__ ((aligned (16)));
 static unsigned long total_sleep_time;		/* seconds */
 
 static struct timespec xtime_cache __attribute__ ((aligned (16)));
-static inline void update_xtime_cache(u64 nsec)
+void update_xtime_cache(u64 nsec)
 {
 	xtime_cache = xtime;
 	timespec_add_ns(&xtime_cache, nsec);
@@ -145,6 +145,7 @@ int do_settimeofday(struct timespec *tv)
 
 	set_normalized_timespec(&xtime, sec, nsec);
 	set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
+	update_xtime_cache(0);
 
 	clock->error = 0;
 	ntp_clear();
@@ -252,8 +253,8 @@ void __init timekeeping_init(void)
 	xtime.tv_nsec = 0;
 	set_normalized_timespec(&wall_to_monotonic,
 		-xtime.tv_sec, -xtime.tv_nsec);
+	update_xtime_cache(0);
 	total_sleep_time = 0;
-
 	write_sequnlock_irqrestore(&xtime_lock, flags);
 }
 
@@ -290,6 +291,7 @@ static int timekeeping_resume(struct sys_device *dev)
 	}
 	/* Make sure that we have the correct xtime reference */
 	timespec_add_ns(&xtime, timekeeping_suspend_nsecs);
+	update_xtime_cache(0);
 	/* re-base the last cycle value */
 	clock->cycle_last = clocksource_read(clock);
 	clock->error = 0;