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sys_macosx: synchronise RTC from system time

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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.
This commit is contained in:
Bryan Christianson 2015-12-04 00:15:49 +13:00 committed by Miroslav Lichvar
parent 302abf8480
commit 86e0399ea9
2 changed files with 33 additions and 6 deletions
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15
chrony.texi.in
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@ -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

24
sys_macosx.c
View file

@ -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);