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authorJohn Stultz <john.stultz@linaro.org>2012-09-11 15:04:18 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-10-02 10:30:36 -0700
commit80257cbe62ea0919153c43421746269ab68473bf (patch)
tree8d1286bedf3fee0cbca60ca8c2029a71577401e9 /kernel
parent8e878154f5658ba93cf9bb2b491a930ec195de3d (diff)
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/time/timekeeping.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index dd31d0e96bcb..104d549f9df1 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1057,9 +1057,12 @@ static void update_wall_time(void)
#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,