time: Only do nanosecond rounding on GENERIC_TIME_VSYSCALL_OLD systems

[karo-tx-linux.git] / kernel / time / timekeeping.c

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index ce618010c373c0dc795565f91d2494e13037a893..16280ff3cf82933015bebc248af1288ad8b53d10 100644 (file)
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1062,6 +1062,33 @@ static cycle_t logarithmic_accumulation(struct timekeeper *tk, cycle_t offset,
        return offset;
 }
 
+#ifdef CONFIG_GENERIC_TIME_VSYSCALL_OLD
+static inline void old_vsyscall_fixup(struct timekeeper *tk)
+{
+       s64 remainder;
+
+       /*
+       * Store only full nanoseconds into xtime_nsec after rounding
+       * it up and add the remainder to the error difference.
+       * XXX - This is necessary to avoid small 1ns inconsistnecies caused
+       * by truncating the remainder in vsyscalls. However, it causes
+       * additional work to be done in timekeeping_adjust(). Once
+       * the vsyscall implementations are converted to use xtime_nsec
+       * (shifted nanoseconds), and CONFIG_GENERIC_TIME_VSYSCALL_OLD
+       * users are removed, this can be killed.
+       */
+       remainder = tk->xtime_nsec & ((1ULL << tk->shift) - 1);
+       tk->xtime_nsec -= remainder;
+       tk->xtime_nsec += 1ULL << tk->shift;
+       tk->ntp_error += remainder << tk->ntp_error_shift;
+
+}
+#else
+#define old_vsyscall_fixup(tk)
+#endif
+
+
+
 /**
  * update_wall_time - Uses the current clocksource to increment the wall time
  *
@@ -1073,7 +1100,6 @@ static void update_wall_time(void)
        cycle_t offset;
        int shift = 0, maxshift;
        unsigned long flags;
-       s64 remainder;
 
        write_seqlock_irqsave(&tk->lock, flags);
 
@@ -1115,20 +1141,11 @@ static void update_wall_time(void)
        /* correct the clock when NTP error is too big */
        timekeeping_adjust(tk, offset);
 
-
        /*
-       * Store only full nanoseconds into xtime_nsec after rounding
-       * it up and add the remainder to the error difference.
-       * XXX - This is necessary to avoid small 1ns inconsistnecies caused
-       * by truncating the remainder in vsyscalls. However, it causes
-       * additional work to be done in timekeeping_adjust(). Once
-       * the vsyscall implementations are converted to use xtime_nsec
-       * (shifted nanoseconds), this can be killed.
-       */
-       remainder = tk->xtime_nsec & ((1ULL << tk->shift) - 1);
-       tk->xtime_nsec -= remainder;
-       tk->xtime_nsec += 1ULL << tk->shift;
-       tk->ntp_error += remainder << tk->ntp_error_shift;
+        * XXX This can be killed once everyone converts
+        * to the new update_vsyscall.
+        */
+       old_vsyscall_fixup(tk);
 
        /*
         * Finally, make sure that after the rounding