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| author | John Stultz <john.stultz@linaro.org> | 2012-09-11 15:04:18 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-10-02 10:30:36 -0700 |
| commit | 80257cbe62ea0919153c43421746269ab68473bf (patch) | |
| tree | 8d1286bedf3fee0cbca60ca8c2029a71577401e9 | |
| parent | 8e878154f5658ba93cf9bb2b491a930ec195de3d (diff) | |
| download | lwn-80257cbe62ea0919153c43421746269ab68473bf.tar.gz lwn-80257cbe62ea0919153c43421746269ab68473bf.zip | |
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>
| -rw-r--r-- | kernel/time/timekeeping.c | 5 |
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, |