time: Avoid making adjustments if we haven't accumulated anything
commit bf2ac312195155511a0f79325515cbb61929898a upstream.
If update_wall_time() is called and the current offset isn't large
enough to accumulate, avoid re-calling timekeeping_adjust which may
change the clock freq and can cause 1ns inconsistencies with
CLOCK_REALTIME_COARSE/CLOCK_MONOTONIC_COARSE.
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Link: http://lkml.kernel.org/r/1345595449-34965-5-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index dd31d0e..104d549 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1057,9 +1057,12 @@
#else
offset = (clock->read(clock) - clock->cycle_last) & clock->mask;
#endif
+ /* Check if there's really nothing to do */
+ if (offset < timekeeper.cycle_interval)
+ goto out;
+
timekeeper.xtime_nsec = (s64)timekeeper.xtime.tv_nsec <<
timekeeper.shift;
-
/*
* With NO_HZ we may have to accumulate many cycle_intervals
* (think "ticks") worth of time at once. To do this efficiently,