Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [ 187/218] time: Avoid making adjustments if we havent accumulated anything | Date | Fri, 28 Sep 2012 13:16:44 -0700 |
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3.4-stable review patch. If anyone has any objections, please let me know.
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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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