sys_macosx: synchronise RTC from system time

When the rtcsync directive is specified in the chronyd config file,
chronyd will update the RTC via settimeofday() every 60 minutes if
the system time is synchronised to NTP.

diff --git a/chrony.texi.in b/chrony.texi.in
index 4bb212a6f1e556138aba27cc2f42c05535037bea..532d8f1a32b06da3a490dab63e82c2a9c2755d28 100644 (file)
--- a/chrony.texi.in
+++ b/chrony.texi.in
@@ -2844,12 +2844,17 @@ Note that this setting is overriden when the @code{hwclockfile} directive
 @node rtcsync directive
 @subsection rtcsync
 
-The @code{rtcsync} directive will enable a kernel mode where the
-system time is copied to the real time clock (RTC) every 11 minutes.
+The @code{rtcsync} directive enables a mode where the system time is
+periodically copied to the real time clock (RTC).
 
-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} directive is used.
+
+On Mac OS X, chronyd will perform the RTC copy every 60 minutes when the
+system clock is in a synchronised state.
+
+On other systems this directive does nothing.
 @c }}}
 @c {{{ sched_priority
 @node sched_priority directive

diff --git a/sys_macosx.c b/sys_macosx.c
index 36981ba9021414c607929d72d365e9e03a19e0a3..266d2ad8121eaf8e80a7a0b7a0e88cfe8f612ea7 100644 (file)
--- a/sys_macosx.c
+++ b/sys_macosx.c
@@ -38,6 +38,7 @@
 #include <pthread.h>
 
 #include "sys_macosx.h"
+#include "conf.h"
 #include "localp.h"
 #include "logging.h"
 #include "sched.h"
@@ -88,6 +89,11 @@ static struct timeval Tdrift;
 
 #define NANOS_PER_MSEC (1000000ULL)
 
+/* RTC synchronisation - once an hour */
+
+static struct timeval last_rtc_sync;
+#define RTC_SYNC_INTERVAL (60 * 60.0)
+
 /* ================================================== */
 
 static void
@@ -105,6 +111,7 @@ clock_initialise(void)
     LOG_FATAL(LOGF_SysMacOSX, "gettimeofday() failed");
   }
   Tdrift = T0;
+  last_rtc_sync = T0;
 
   newadj.tv_sec = 0;
   newadj.tv_usec = 0;
@@ -317,7 +324,8 @@ drift_removal_timeout(SCH_ArbitraryArgument not_used)
 
 /* ================================================== */
 
-/* use est_error to calculate the drift_removal_interval */
+/* use est_error to calculate the drift_removal_interval and
+   update the RTC */
 
 static void
 set_sync_status(int synchronised, double est_error, double max_error)
@@ -327,6 +335,20 @@ 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;
+
+      SCH_GetLastEventTime(NULL, NULL, &now);
+      UTI_DiffTimevalsToDouble(&rtc_sync_elapsed, &now, &last_rtc_sync);
+      if (fabs(rtc_sync_elapsed) >= RTC_SYNC_INTERVAL) {
+        /* update the RTC by applying a step of 0.0 secs */
+        apply_step_offset(0.0);
+        last_rtc_sync = now;
+        DEBUG_LOG(LOGF_SysMacOSX, "rtc synchronised");
+      }
+    }
+
     interval = ERROR_WEIGHT * est_error / (fabs(current_freq) + FREQUENCY_RES);
     drift_removal_interval = MAX(interval, DRIFT_REMOVAL_INTERVAL_MIN);