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authorMiroslav Lichvar <mlichvar@redhat.com>2013-08-01 19:31:35 +0200
committerJohn Stultz <john.stultz@linaro.org>2013-08-22 12:33:38 -0700
commita97ad0c4b447a132a322cedc3a5f7fa4cab4b304 (patch)
tree75d527386d058d33bef205dec11ed277ed8d9188 /kernel/time
parent397bbf6dee50bb1f07cbdb464c41b0f5b7a85493 (diff)
ntp: Make periodic RTC update more reliable
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>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/ntp.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 8f5b3b98577b..ab1fa7cb8912 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;