From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754036Ab2IQAuu (ORCPT ); Sun, 16 Sep 2012 20:50:50 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:33410 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753090Ab2IQAtm (ORCPT ); Sun, 16 Sep 2012 20:49:42 -0400 Message-Id: <20120917003637.135114814@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Mon, 17 Sep 2012 01:37:44 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, John Stultz , Prarit Bhargava , Ingo Molnar , Thomas Gleixner Subject: [ 079/135] time: Avoid making adjustments if we havent accumulated anything In-Reply-To: <20120917003625.784119135@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:21c:bfff:fe03:f805 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: John Stultz This is a -stable backport of bf2ac312195155511a0f79325515cbb61929898a 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 Cc: Linux Kernel Signed-off-by: John Stultz --- kernel/time/timekeeping.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1033,6 +1033,10 @@ 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) + return; + timekeeper.xtime_nsec = (s64)xtime.tv_nsec << timekeeper.shift; /*