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[3.11.y.z,extended,stable] Patch "ntp: Make periodic RTC update more reliable" has been added to staging queue

Message ID 1386772915-11054-1-git-send-email-luis.henriques@canonical.com
State New
Headers show

Commit Message

Luis Henriques Dec. 11, 2013, 2:41 p.m. UTC 
This is a note to let you know that I have just added a patch titled

    ntp: Make periodic RTC update more reliable

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

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From eb88e4710636ceec1daeda029c24ac57a695ed1c Mon Sep 17 00:00:00 2001
From: Miroslav Lichvar <mlichvar@redhat.com>
Date: Thu, 1 Aug 2013 19:31:35 +0200
Subject: ntp: Make periodic RTC update more reliable

commit a97ad0c4b447a132a322cedc3a5f7fa4cab4b304 upstream.

The current code requires that the scheduled update of the RTC happens
in the closest tick to the half of the second. This seems to be
difficult to achieve reliably. The scheduled work may be missing the
target time by a tick or two and be constantly rescheduled every second.

Relax the limit to 10 ticks. As a typical RTC drifts in the 11-minute
update interval by several milliseconds, this shouldn't affect the
overall accuracy of the RTC much.

Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: Josh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 kernel/time/ntp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--
1.8.3.2
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Patch

diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index bb22151..af8d1d4 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -475,6 +475,7 @@  static void sync_cmos_clock(struct work_struct *work)
 	 * called as close as possible to 500 ms before the new second starts.
 	 * This code is run on a timer.  If the clock is set, that timer
 	 * may not expire at the correct time.  Thus, we adjust...
+	 * We want the clock to be within a couple of ticks from the target.
 	 */
 	if (!ntp_synced()) {
 		/*
@@ -485,7 +486,7 @@  static void sync_cmos_clock(struct work_struct *work)
 	}

 	getnstimeofday(&now);
-	if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2) {
+	if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec * 5) {
 		struct timespec adjust = now;

 		fail = -ENODEV;