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-rw-r--r--include/linux/timex.h3
-rw-r--r--kernel/timer.c39
2 files changed, 37 insertions, 5 deletions
diff --git a/include/linux/timex.h b/include/linux/timex.h
index 04a4a8cb4ed..b7ca1204e42 100644
--- a/include/linux/timex.h
+++ b/include/linux/timex.h
@@ -345,6 +345,9 @@ time_interpolator_reset(void)
#endif /* !CONFIG_TIME_INTERPOLATION */
+/* Returns how long ticks are at present, in ns / 2^(SHIFT_SCALE-10). */
+extern u64 current_tick_length(void);
+
#endif /* KERNEL */
#endif /* LINUX_TIMEX_H */
diff --git a/kernel/timer.c b/kernel/timer.c
index b9dad399467..fe3a9a9f832 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -717,12 +717,16 @@ static void second_overflow(void)
#endif
}
-/* in the NTP reference this is called "hardclock()" */
-static void update_wall_time_one_tick(void)
+/*
+ * Returns how many microseconds we need to add to xtime this tick
+ * in doing an adjustment requested with adjtime.
+ */
+static long adjtime_adjustment(void)
{
- long time_adjust_step, delta_nsec;
+ long time_adjust_step;
- if ((time_adjust_step = time_adjust) != 0 ) {
+ time_adjust_step = time_adjust;
+ if (time_adjust_step) {
/*
* We are doing an adjtime thing. Prepare time_adjust_step to
* be within bounds. Note that a positive time_adjust means we
@@ -733,10 +737,19 @@ static void update_wall_time_one_tick(void)
*/
time_adjust_step = min(time_adjust_step, (long)tickadj);
time_adjust_step = max(time_adjust_step, (long)-tickadj);
+ }
+ return time_adjust_step;
+}
+/* in the NTP reference this is called "hardclock()" */
+static void update_wall_time_one_tick(void)
+{
+ long time_adjust_step, delta_nsec;
+
+ time_adjust_step = adjtime_adjustment();
+ if (time_adjust_step)
/* Reduce by this step the amount of time left */
time_adjust -= time_adjust_step;
- }
delta_nsec = tick_nsec + time_adjust_step * 1000;
/*
* Advance the phase, once it gets to one microsecond, then
@@ -759,6 +772,22 @@ static void update_wall_time_one_tick(void)
}
/*
+ * Return how long ticks are at the moment, that is, how much time
+ * update_wall_time_one_tick will add to xtime next time we call it
+ * (assuming no calls to do_adjtimex in the meantime).
+ * The return value is in fixed-point nanoseconds with SHIFT_SCALE-10
+ * bits to the right of the binary point.
+ * This function has no side-effects.
+ */
+u64 current_tick_length(void)
+{
+ long delta_nsec;
+
+ delta_nsec = tick_nsec + adjtime_adjustment() * 1000;
+ return ((u64) delta_nsec << (SHIFT_SCALE - 10)) + time_adj;
+}
+
+/*
* Using a loop looks inefficient, but "ticks" is
* usually just one (we shouldn't be losing ticks,
* we're doing this this way mainly for interrupt