1 files changed, 33 insertions, 38 deletions

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index e91c29f961c9..83d3555a6998 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -58,27 +58,23 @@ struct clocksource *clock;
 
 #ifdef CONFIG_GENERIC_TIME
 /**
- * __get_nsec_offset - Returns nanoseconds since last call to periodic_hook
+ * clocksource_forward_now - update clock to the current time
  *
- * private function, must hold xtime_lock lock when being
- * called. Returns the number of nanoseconds since the
- * last call to update_wall_time() (adjusted by NTP scaling)
+ * Forward the current clock to update its state since the last call to
+ * update_wall_time(). This is useful before significant clock changes,
+ * as it avoids having to deal with this time offset explicitly.
  */
-static inline s64 __get_nsec_offset(void)
+static void clocksource_forward_now(void)
 {
         cycle_t cycle_now, cycle_delta;
-        s64 ns_offset;
+        s64 nsec;
 
-        /* read clocksource: */
         cycle_now = clocksource_read(clock);
-
-        /* calculate the delta since the last update_wall_time: */
         cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
+        clock->cycle_last = cycle_now;
 
-        /* convert to nanoseconds: */
-        ns_offset = cyc2ns(clock, cycle_delta);
-
-        return ns_offset;
+        nsec = cyc2ns(clock, cycle_delta);
+        timespec_add_ns(&xtime, nsec);
 }
 
 /**
@@ -89,6 +85,7 @@ static inline s64 __get_nsec_offset(void)
  */
 void getnstimeofday(struct timespec *ts)
 {
+        cycle_t cycle_now, cycle_delta;
         unsigned long seq;
         s64 nsecs;
 
@@ -96,7 +93,15 @@ void getnstimeofday(struct timespec *ts)
                 seq = read_seqbegin(&xtime_lock);
 
                 *ts = xtime;
-                nsecs = __get_nsec_offset();
+
+                /* read clocksource: */
+                cycle_now = clocksource_read(clock);
+
+                /* calculate the delta since the last update_wall_time: */
+                cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
+
+                /* convert to nanoseconds: */
+                nsecs = cyc2ns(clock, cycle_delta);
 
         } while (read_seqretry(&xtime_lock, seq));
 
@@ -129,22 +134,22 @@ EXPORT_SYMBOL(do_gettimeofday);
  */
 int do_settimeofday(struct timespec *tv)
 {
+        struct timespec ts_delta;
         unsigned long flags;
-        time_t wtm_sec, sec = tv->tv_sec;
-        long wtm_nsec, nsec = tv->tv_nsec;
 
         if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
                 return -EINVAL;
 
         write_seqlock_irqsave(&xtime_lock, flags);
 
-        nsec -= __get_nsec_offset();
+        clocksource_forward_now();
+
+        ts_delta.tv_sec = tv->tv_sec - xtime.tv_sec;
+        ts_delta.tv_nsec = tv->tv_nsec - xtime.tv_nsec;
+        wall_to_monotonic = timespec_sub(wall_to_monotonic, ts_delta);
 
-        wtm_sec  = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
-        wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
+        xtime = *tv;
 
-        set_normalized_timespec(&xtime, sec, nsec);
-        set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
         update_xtime_cache(0);
 
         clock->error = 0;
@@ -170,22 +175,17 @@ EXPORT_SYMBOL(do_settimeofday);
 static void change_clocksource(void)
 {
         struct clocksource *new;
-        cycle_t now;
-        u64 nsec;
 
         new = clocksource_get_next();
 
         if (clock == new)
                 return;
 
-        new->cycle_last = 0;
-        now = clocksource_read(new);
-        nsec =  __get_nsec_offset();
-        timespec_add_ns(&xtime, nsec);
+        clocksource_forward_now();
 
         clock = new;
-        clock->cycle_last = now;
-
+        clock->cycle_last = 0;
+        clock->cycle_last = clocksource_read(new);
         clock->error = 0;
         clock->xtime_nsec = 0;
         clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
@@ -200,8 +200,8 @@ static void change_clocksource(void)
          */
 }
 #else
+static inline void clocksource_forward_now(void) { }
 static inline void change_clocksource(void) { }
-static inline s64 __get_nsec_offset(void) { return 0; }
 #endif
 
 /**
@@ -265,8 +265,6 @@ void __init timekeeping_init(void)
 static int timekeeping_suspended;
 /* time in seconds when suspend began */
 static unsigned long timekeeping_suspend_time;
-/* xtime offset when we went into suspend */
-static s64 timekeeping_suspend_nsecs;
 
 /**
  * timekeeping_resume - Resumes the generic timekeeping subsystem.
@@ -292,8 +290,6 @@ static int timekeeping_resume(struct sys_device *dev)
                 wall_to_monotonic.tv_sec -= sleep_length;
                 total_sleep_time += sleep_length;
         }
-        /* 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 = 0;
@@ -319,8 +315,7 @@ static int timekeeping_suspend(struct sys_device *dev, pm_message_t state)
         timekeeping_suspend_time = read_persistent_clock();
 
         write_seqlock_irqsave(&xtime_lock, flags);
-        /* Get the current xtime offset */
-        timekeeping_suspend_nsecs = __get_nsec_offset();
+        clocksource_forward_now();
         timekeeping_suspended = 1;
         write_sequnlock_irqrestore(&xtime_lock, flags);
 
@@ -461,10 +456,10 @@ void update_wall_time(void)
          */
         while (offset >= clock->cycle_interval) {
                 /* accumulate one interval */
-                clock->xtime_nsec += clock->xtime_interval;
-                clock->cycle_last += clock->cycle_interval;
                 offset -= clock->cycle_interval;
+                clock->cycle_last += clock->cycle_interval;
 
+                clock->xtime_nsec += clock->xtime_interval;
                 if (clock->xtime_nsec >= (u64)NSEC_PER_SEC << clock->shift) {
                         clock->xtime_nsec -= (u64)NSEC_PER_SEC << clock->shift;
                         xtime.tv_sec++;