path: root/kernel
diff options
authorMiroslav Lichvar <mlichvar@redhat.com>2013-08-01 19:31:35 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-12-08 07:29:28 -0800
commit9baca2ff1035fbdc7f910a4b6fb34d4bec3f443b (patch)
treeac75d1ab045271da6b89cc243b4d1ee543cb65d1 /kernel
parent72b9401c2f5ac465d97969ef7933753642bde8bf (diff)
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index bb2215174f0..af8d1d4f3d5 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)
- 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;