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    Subject[ 187/218] time: Avoid making adjustments if we havent accumulated anything
    Date
    3.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: John Stultz <john.stultz@linaro.org>

    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>
    ---
    kernel/time/timekeeping.c | 5 ++++-
    1 file changed, 4 insertions(+), 1 deletion(-)

    --- 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,



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