From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965121Ab2I1Ubj (ORCPT ); Fri, 28 Sep 2012 16:31:39 -0400 Received: from mail-da0-f46.google.com ([209.85.210.46]:56440 "EHLO mail-da0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1032890Ab2I1Ubc (ORCPT ); Fri, 28 Sep 2012 16:31:32 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , alan@lxorguk.ukuu.org.uk, John Stultz , Prarit Bhargava , Ingo Molnar , Thomas Gleixner Subject: [ 187/218] time: Avoid making adjustments if we havent accumulated anything Date: Fri, 28 Sep 2012 13:16:44 -0700 Message-Id: <20120928201522.985255719@linuxfoundation.org> X-Mailer: git-send-email 1.7.12.1.428.g652398a In-Reply-To: <20120928201501.208384923@linuxfoundation.org> References: <20120928201501.208384923@linuxfoundation.org> User-Agent: quilt/0.60-2.1.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: John Stultz 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 Cc: Prarit Bhargava Cc: Ingo Molnar Link: http://lkml.kernel.org/r/1345595449-34965-5-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner Signed-off-by: John Stultz Signed-off-by: Greg Kroah-Hartman --- 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,