| Re: [chrony-dev] [PATCH] Mac OS X - Synchronise RTC from system time |
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On Thu, Dec 03, 2015 at 08:44:16AM +1300, Bryan Christianson wrote:
> When the rtcsync directive is specified in the chronyd config file,
> chronyd will update the RTC via settimeofday() every 60 minutes if
> the time is syncronised to NTP.
Typo ------------^
> -This directive is supported only on Linux and cannot be used when the
> -normal RTC tracking is enabled, i.e. when the @code{rtcfile} directive
> -is used. On other systems this directive does nothing.
> +On Linux the RTC copy is performed by the kernel every 11 minutes. This
> +directive cannot be used when the normal RTC tracking is enabled,
> +i.e. when the @code{rtcfile} directiveis used.
Another typo ----------------------------^
> @@ -101,6 +107,10 @@ clock_initialise(void)
> drift_removal_interval = DRIFT_REMOVAL_INTERVAL;
> current_drift_removal_interval = DRIFT_REMOVAL_INTERVAL;
>
> + if (gettimeofday(&last_rtc_sync, NULL) < 0) {
> + LOG_FATAL(LOGF_SysMacOSX, "gettimeofday() failed");
> + }
> +
There is a gettimeofday() call just below that, so last_rtc_sync could
be set to T0.
> if (gettimeofday(&T0, NULL) < 0) {
> LOG_FATAL(LOGF_SysMacOSX, "gettimeofday() failed");
> }
> @@ -327,6 +339,21 @@ set_sync_status(int synchronised, double est_error, double max_error)
> if (!synchronised) {
> drift_removal_interval = MAX(drift_removal_interval, DRIFT_REMOVAL_INTERVAL);
> } else {
> + if (CNF_GetRtcSync()) {
> + struct timeval now;
> + double rtc_sync_elapsed;
> +
> + if (gettimeofday(&now, NULL))
> + LOG_FATAL(LOGF_SysMacOSX, "gettimeofday() failed");
To avoid the additional system call per clock update this could be
replaced with SCH_GetLastEventTime(NULL, NULL, &now) as a cheaper
alternative of getting current time.
> + UTI_DiffTimevalsToDouble(&rtc_sync_elapsed, &now, &last_rtc_sync);
> + if (rtc_sync_elapsed >= RTC_SYNC_INTERVAL) {
It might be better to use fabs(rtc_sync_elapsed) here to not get stuck
in case the clock is stepped back by a large amount since the last
update.
--
Miroslav Lichvar
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