From: John Stultz <john.stultz@linaro.org>
Date: Tue, 18 Sep 2012 01:38:46 +0000 (-0400)
Subject: time: Avoid making adjustments if we haven't accumulated anything
X-Git-Tag: v2.6.34.14~75
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=b4e2564c9f5ba83af10076d029a7507b7a33b870;p=thirdparty%2Fkernel%2Fstable.git

time: Avoid making adjustments if we haven't accumulated anything

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>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 0d59077c3fe80..bbdad71aa90f5 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -849,6 +849,10 @@ void update_wall_time(void)
 #else
 	offset = timekeeper.cycle_interval;
 #endif
+	/* Check if there's really nothing to do */
+	if (offset < timekeeper.cycle_interval)
+		return;
+
 	timekeeper.xtime_nsec = (s64)xtime.tv_nsec << timekeeper.shift;
 
 	/*