From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759745Ab2IKTEr (ORCPT ); Tue, 11 Sep 2012 15:04:47 -0400 Received: from e9.ny.us.ibm.com ([32.97.182.139]:60573 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753613Ab2IKTEn (ORCPT ); Tue, 11 Sep 2012 15:04:43 -0400 From: John Stultz To: stable@vger.kernel.org Cc: John Stultz , Prarit Bhargava , Ingo Molnar , Thomas Gleixner , Linux Kernel Subject: [PATCH 2/3] 3.4.y: time: Avoid making adjustments if we haven't accumulated anything Date: Tue, 11 Sep 2012 15:04:18 -0400 Message-Id: <1347390259-54838-3-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1347390259-54838-1-git-send-email-john.stultz@linaro.org> References: <1347390259-54838-1-git-send-email-john.stultz@linaro.org> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12091119-7182-0000-0000-000002970BCB Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Cc: stable@vger.kernel.org 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 | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index dd31d0e..104d549 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, -- 1.7.9.5