diff mbox

[4/4] time: Avoid making adjustments if we havne't accumulated anything

Message ID 1345595449-34965-5-git-send-email-john.stultz@linaro.org
State Accepted
Commit bf2ac312195155511a0f79325515cbb61929898a
Headers show

Commit Message

John Stultz Aug. 22, 2012, 12:30 a.m. UTC
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.

Cc: Ingo Molnar <mingo@kernel.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
 kernel/time/timekeeping.c |    4 ++++
 1 file changed, 4 insertions(+)
diff mbox

Patch

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index a5a9389..0c1485e 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1152,6 +1152,10 @@  static void update_wall_time(void)
 	offset = (clock->read(clock) - clock->cycle_last) & clock->mask;
 #endif
 
+	/* Check if there's really nothing to do */
+	if (offset < tk->cycle_interval)
+		goto out;
+
 	/*
 	 * With NO_HZ we may have to accumulate many cycle_intervals
 	 * (think "ticks") worth of time at once. To do this efficiently,