Allowing hctosys to drift compensate facilitates:
More precise setting of the System Clock early in
the boot process when --adjust cannot be used
because the file system is not writeable.
Applies sub second drift corrections immediately,
where as --adjust cannot.
Reduces boot time by not calling hwclock multiple
times, e.g., --hctosys early before fsck when the
file system is read-only, then --adjust later when
the file system is read-write and --hctosys again
for drift correction.
Use of --adjust elsewhere may no longer be
necessary.
Part II
After the original submission of this patch I
realized that now all operations except --systz
require drift corrected Hardware Clock time.
Therefore, it should be done only once early in
the process. Upon implementation of that premise
many improvements were facilitated:
* Adds drift correction to --hctosys.
* Adds setting system time with sub-second precision.
* Adds --get, a drift corrected 'show' operation.
* Improves drift factor calculation precision while
greatly simplifying its algorithm.
* Fixes --show bug, printing integer sub-seconds, and
now uses a more intuitive positive value.
* Fixes --predict bug, drift correction must be
negated to predict future RTC time.
* Reduces the number of function arguments and
lines of code.
Signed-off-by: J William Piggott <elseifthen@xxxxxxx>
---
sys-utils/hwclock.c | 205 +++++++++++++++++++++++-----------------------------
1 file changed, 91 insertions(+), 114 deletions(-)
diff --git a/sys-utils/hwclock.c b/sys-utils/hwclock.c
index 474e04f..0dd9ad6 100644
--- a/sys-utils/hwclock.c
+++ b/sys-utils/hwclock.c
@@ -181,6 +181,18 @@ static void read_date_from_file(struct tm *tm)
}
/*
+ * Type time_t to type timeval conversion.
+ */
+static struct timeval t2tv(time_t timet)
+{
+ struct timeval rettimeval;
+
+ rettimeval.tv_sec = timet;
+ rettimeval.tv_usec = 0;
+ return(rettimeval);
+}
+
+/*
* The difference in seconds between two times in "timeval" format.
*/
double time_diff(struct timeval subtrahend, struct timeval subtractor)
@@ -678,8 +690,7 @@ set_hardware_clock_exact(const time_t sethwtime,
* Include in the output the adjustment "sync_duration".
*/
static void
-display_time(const bool hclock_valid, const time_t systime,
- const double sync_duration)
+display_time(const bool hclock_valid, struct timeval hwctime)
{
if (!hclock_valid)
warnx(_
@@ -691,9 +702,9 @@ display_time(const bool hclock_valid, const time_t systime,
char *format = "%c";
char ctime_now[200];
- lt = localtime(&systime);
+ lt = localtime(&hwctime.tv_sec);
strftime(ctime_now, sizeof(ctime_now), format, lt);
- printf(_("%s %.6f seconds\n"), ctime_now, -(sync_duration));
+ printf(_("%s .%06d seconds\n"), ctime_now, (int)hwctime.tv_usec);
}
}
@@ -807,7 +818,7 @@ static int interpret_date_string(const char *date_opt, time_t * const time_p)
* have.
*/
static int
-set_system_clock(const bool hclock_valid, const time_t newtime,
+set_system_clock(const bool hclock_valid, const struct timeval newtime,
const bool testing)
{
int retcode;
@@ -818,15 +829,11 @@ set_system_clock(const bool hclock_valid, const time_t newtime,
"we cannot set the System Time from it."));
retcode = 1;
} else {
- struct timeval tv;
struct tm *broken;
int minuteswest;
int rc;
- tv.tv_sec = newtime;
- tv.tv_usec = 0;
-
- broken = localtime(&newtime);
+ broken = localtime(&newtime.tv_sec);
#ifdef HAVE_TM_GMTOFF
minuteswest = -broken->tm_gmtoff / 60; /* GNU extension */
#else
@@ -838,7 +845,7 @@ set_system_clock(const bool hclock_valid, const time_t newtime,
if (debug) {
printf(_("Calling settimeofday:\n"));
printf(_("\ttv.tv_sec = %ld, tv.tv_usec = %ld\n"),
- (long)tv.tv_sec, (long)tv.tv_usec);
+ (long)newtime.tv_sec, (long)newtime.tv_usec);
printf(_("\ttz.tz_minuteswest = %d\n"), minuteswest);
}
if (testing) {
@@ -848,7 +855,7 @@ set_system_clock(const bool hclock_valid, const time_t newtime,
} else {
const struct timezone tz = { minuteswest, 0 };
- rc = settimeofday(&tv, &tz);
+ rc = settimeofday(&newtime, &tz);
if (rc) {
if (errno == EPERM) {
warnx(_
@@ -974,9 +981,9 @@ static int set_system_clock_timezone(const bool universal, const bool testing)
*/
static void
adjust_drift_factor(struct adjtime *adjtime_p,
- const time_t nowtime,
+ const struct timeval nowtime,
const bool hclock_valid,
- const time_t hclocktime, const double sync_delay)
+ const struct timeval hclocktime)
{
if (!hclock_valid) {
if (debug)
@@ -989,7 +996,7 @@ adjust_drift_factor(struct adjtime *adjtime_p,
"calibration time is zero,\n"
"so history is bad and calibration startover "
"is necessary.\n"));
- } else if ((hclocktime - adjtime_p->last_calib_time) < 24 * 60 * 60) {
+ } else if ((hclocktime.tv_sec - adjtime_p->last_calib_time) < 24 * 60 * 60) {
if (debug)
printf(_("Not adjusting drift factor because it has "
"been less than a day since the last "
@@ -1009,39 +1016,16 @@ adjust_drift_factor(struct adjtime *adjtime_p,
* but 195 days + 1 second equals 195 days in floats.)
*/
const double sec_per_day = 24.0 * 60.0 * 60.0;
- double atime_per_htime;
- double adj_days, cal_days;
- double exp_drift, unc_drift;
double factor_adjust;
double drift_factor;
+ struct timeval lastCalib;
- /* Adjusted time units per hardware time unit */
- atime_per_htime = 1.0 + adjtime_p->drift_factor / sec_per_day;
+ lastCalib = t2tv(adjtime_p->last_calib_time);
- /* Days since last adjustment (in hardware clock time) */
- adj_days = (double)(hclocktime - adjtime_p->last_adj_time)
- / sec_per_day;
+ factor_adjust = time_diff(nowtime, hclocktime) /
+ (time_diff(nowtime, lastCalib) / sec_per_day);
- /* Expected drift (sec) since last adjustment */
- exp_drift = adj_days * adjtime_p->drift_factor
- + adjtime_p->not_adjusted;
-
- /* Uncorrected drift (sec) since last calibration */
- unc_drift = (double)(nowtime - hclocktime)
- + sync_delay - exp_drift;
-
- /* Days since last calibration (in hardware clock time) */
- cal_days = ((double)(adjtime_p->last_adj_time
- - adjtime_p->last_calib_time)
- + adjtime_p->not_adjusted)
- / (sec_per_day * atime_per_htime) + adj_days;
-
- /* Amount to add to previous drift factor */
- factor_adjust = unc_drift / cal_days;
-
- /* New drift factor */
drift_factor = adjtime_p->drift_factor + factor_adjust;
-
if (abs(drift_factor) > MAX_DRIFT) {
if (debug)
printf(_("Clock drift factor was calculated as "
@@ -1052,19 +1036,19 @@ adjust_drift_factor(struct adjtime *adjtime_p,
} else {
if (debug)
printf(_("Clock drifted %.1f seconds in the past "
- "%d seconds in spite of a drift factor of "
+ "%.1f seconds\nin spite of a drift factor of "
"%f seconds/day.\n"
"Adjusting drift factor by %f seconds/day\n"),
- unc_drift,
- (int)(nowtime - adjtime_p->last_calib_time),
+ time_diff(nowtime, hclocktime),
+ time_diff(nowtime, lastCalib),
adjtime_p->drift_factor, factor_adjust);
}
adjtime_p->drift_factor = drift_factor;
}
- adjtime_p->last_calib_time = nowtime;
+ adjtime_p->last_calib_time = nowtime.tv_sec;
- adjtime_p->last_adj_time = nowtime;
+ adjtime_p->last_adj_time = nowtime.tv_sec;
adjtime_p->not_adjusted = 0;
@@ -1087,26 +1071,23 @@ static void
calculate_adjustment(const double factor,
const time_t last_time,
const double not_adjusted,
- const time_t systime, int *adjustment_p, double *retro_p)
+ const time_t systime, struct timeval *tdrift_p)
{
double exact_adjustment;
exact_adjustment =
((double)(systime - last_time)) * factor / (24 * 60 * 60)
+ not_adjusted;
- *adjustment_p = FLOOR(exact_adjustment);
-
- *retro_p = exact_adjustment - (double)*adjustment_p;
+ tdrift_p->tv_sec = FLOOR(exact_adjustment);
+ tdrift_p->tv_usec = (exact_adjustment -
+ (double)tdrift_p->tv_sec) * 1E6;
if (debug) {
printf(P_("Time since last adjustment is %d second\n",
"Time since last adjustment is %d seconds\n",
(int)(systime - last_time)),
(int)(systime - last_time));
- printf(P_("Need to insert %d second and refer time back "
- "%.6f seconds ago\n",
- "Need to insert %d seconds and refer time back "
- "%.6f seconds ago\n", *adjustment_p),
- *adjustment_p, *retro_p);
+ printf(_("Calculated Hardware Clock drift is %ld.%06d seconds\n"),
+ (long)tdrift_p->tv_sec, (int)tdrift_p->tv_usec);
}
}
@@ -1200,7 +1181,7 @@ static void save_adjtime(const struct adjtime adjtime, const bool testing)
*/
static void
do_adjustment(struct adjtime *adjtime_p,
- const bool hclock_valid, const time_t hclocktime,
+ const bool hclock_valid, const struct timeval hclocktime,
const struct timeval read_time,
const bool universal, const bool testing)
{
@@ -1220,27 +1201,13 @@ do_adjustment(struct adjtime *adjtime_p,
printf(_("Not setting clock because drift factor %f is far too high.\n"),
adjtime_p->drift_factor);
} else {
- int adjustment;
- /* Number of seconds we must insert in the Hardware Clock */
- double retro;
- /*
- * Fraction of second we have to remove from clock after
- * inserting <adjustment> whole seconds.
- */
- calculate_adjustment(adjtime_p->drift_factor,
- adjtime_p->last_adj_time,
- adjtime_p->not_adjusted,
- hclocktime, &adjustment, &retro);
- if (adjustment > 0 || adjustment < -1) {
- set_hardware_clock_exact(hclocktime + adjustment,
- time_inc(read_time, -retro),
- universal, testing);
- adjtime_p->last_adj_time = hclocktime + adjustment;
- adjtime_p->not_adjusted = 0;
- adjtime_p->dirty = TRUE;
- } else if (debug)
- printf(_("Needed adjustment is less than one second, "
- "so not setting clock.\n"));
+ set_hardware_clock_exact(hclocktime.tv_sec,
+ time_inc(read_time,
+ -(hclocktime.tv_usec / 1E6)),
+ universal, testing);
+ adjtime_p->last_adj_time = hclocktime.tv_sec;
+ adjtime_p->not_adjusted = 0;
+ adjtime_p->dirty = TRUE;
}
}
@@ -1283,7 +1250,7 @@ manipulate_clock(const bool show, const bool adjust, const bool noadjfile,
const bool hctosys, const bool systohc, const bool systz,
const struct timeval startup_time,
const bool utc, const bool local_opt,
- const bool testing, const bool predict)
+ const bool testing, const bool predict, const bool get)
{
/* Contents of the adjtime file, or what they should be. */
struct adjtime adjtime;
@@ -1302,7 +1269,8 @@ manipulate_clock(const bool show, const bool adjust, const bool noadjfile,
* synchronized to its next clock tick when we
* started up. Defined only if hclock_valid is true.
*/
- time_t hclocktime = 0;
+ struct timeval hclocktime = { 0, 0 };
+ struct timeval tdrift;
/* local return code */
int rc = 0;
@@ -1312,13 +1280,12 @@ manipulate_clock(const bool show, const bool adjust, const bool noadjfile,
return EX_NOPERM;
}
- if (!noadjfile
- && (adjust || set || systohc || (!utc && !local_opt) || predict)) {
+ if (!noadjfile && !(systz && (utc || local_opt))) {
rc = read_adjtime(&adjtime);
if (rc)
return rc;
} else {
- /* A little trick to avoid reading the file if we don't have to */
+ /* A little trick to avoid writing the file if we don't have to */
adjtime.dirty = FALSE;
}
@@ -1330,7 +1297,7 @@ manipulate_clock(const bool show, const bool adjust, const bool noadjfile,
adjtime.dirty = TRUE;
}
- if (show || adjust || hctosys || (!noadjfile && !systz && !predict)) {
+ if (show || get || adjust || hctosys || (!noadjfile && !systz && !predict)) {
/* data from HW-clock are required */
rc = synchronize_to_clock_tick();
@@ -1353,26 +1320,40 @@ manipulate_clock(const bool show, const bool adjust, const bool noadjfile,
*/
if (!rc) {
rc = read_hardware_clock(universal,
- &hclock_valid, &hclocktime);
+ &hclock_valid, &hclocktime.tv_sec);
if (rc && !set && !systohc)
return EX_IOERR;
}
}
-
- if (show) {
- display_time(hclock_valid, hclocktime,
- time_diff(read_time, startup_time));
+ hclocktime = predict ? t2tv(set_time) : hclocktime;
+ calculate_adjustment(adjtime.drift_factor,
+ adjtime.last_adj_time,
+ adjtime.not_adjusted,
+ hclocktime.tv_sec, &tdrift);
+ if (!show && !predict)
+ hclocktime = time_inc(tdrift, hclocktime.tv_sec);
+ if (predict)
+ hclocktime = time_inc(hclocktime, (double)
+ -(tdrift.tv_sec + tdrift.tv_sec / 1E6));
+ if (show || get) {
+ display_time(hclock_valid,
+ time_inc(hclocktime, -time_diff
+ (read_time, startup_time)));
} else if (set) {
set_hardware_clock_exact(set_time, startup_time,
universal, testing);
if (!noadjfile)
- adjust_drift_factor(&adjtime, set_time,
- hclock_valid,
- hclocktime,
- time_diff(read_time, startup_time));
+ adjust_drift_factor(&adjtime,
+ time_inc(t2tv(set_time), time_diff
+ (read_time, startup_time)),
+ hclock_valid, hclocktime);
} else if (adjust) {
- do_adjustment(&adjtime, hclock_valid,
- hclocktime, read_time, universal, testing);
+ if (tdrift.tv_sec > 0 || tdrift.tv_sec < -1)
+ do_adjustment(&adjtime, hclock_valid,
+ hclocktime, read_time, universal, testing);
+ else
+ printf(_("Needed adjustment is less than one second, "
+ "so not setting clock.\n"));
} else if (systohc) {
struct timeval nowtime, reftime;
/*
@@ -1388,10 +1369,8 @@ manipulate_clock(const bool show, const bool adjust, const bool noadjfile,
reftime.tv_sec,
reftime, universal, testing);
if (!noadjfile)
- adjust_drift_factor(&adjtime, (time_t)
- reftime.tv_sec,
- hclock_valid, hclocktime, (double)
- read_time.tv_usec / 1E6);
+ adjust_drift_factor(&adjtime, nowtime,
+ hclock_valid, hclocktime);
} else if (hctosys) {
rc = set_system_clock(hclock_valid, hclocktime, testing);
if (rc) {
@@ -1405,19 +1384,12 @@ manipulate_clock(const bool show, const bool adjust, const bool noadjfile,
return rc;
}
} else if (predict) {
- int adjustment;
- double retro;
-
- calculate_adjustment(adjtime.drift_factor,
- adjtime.last_adj_time,
- adjtime.not_adjusted,
- set_time, &adjustment, &retro);
if (debug) {
printf(_
("At %ld seconds after 1969, RTC is predicted to read %ld seconds after 1969.\n"),
- set_time, set_time + adjustment);
+ set_time, (long)hclocktime.tv_sec);
}
- display_time(TRUE, set_time + adjustment, -retro);
+ display_time(TRUE, hclocktime);
}
if (!noadjfile)
save_adjtime(adjtime, testing);
@@ -1646,7 +1618,7 @@ int main(int argc, char **argv)
/* Variables set by various options; show may also be set later */
/* The options debug, badyear and epoch_option are global */
bool show, set, systohc, hctosys, systz, adjust, getepoch, setepoch,
- predict, compare;
+ predict, compare, get;
bool utc, testing, local_opt, noadjfile, directisa;
char *date_opt;
#ifdef __alpha__
@@ -1659,6 +1631,7 @@ int main(int argc, char **argv)
OPT_DATE,
OPT_DIRECTISA,
OPT_EPOCH,
+ OPT_GET,
OPT_GETEPOCH,
OPT_LOCALTIME,
OPT_NOADJFILE,
@@ -1706,13 +1679,14 @@ int main(int argc, char **argv)
{"adjfile", 1, 0, OPT_ADJFILE},
{"systz", 0, 0, OPT_SYSTZ},
{"predict-hc", 0, 0, OPT_PREDICT_HC},
+ {"get", 0, 0, OPT_GET},
{NULL, 0, NULL, 0}
};
static const ul_excl_t excl[] = { /* rows and cols in in ASCII order */
{ 'a','r','s','w',
- OPT_GETEPOCH, OPT_PREDICT_HC, OPT_SET,
- OPT_SETEPOCH, OPT_SYSTZ },
+ OPT_GET, OPT_GETEPOCH, OPT_PREDICT_HC,
+ OPT_SET, OPT_SETEPOCH, OPT_SYSTZ },
{ 'u', OPT_LOCALTIME},
{ OPT_ADJFILE, OPT_NOADJFILE },
{ 0 }
@@ -1749,7 +1723,7 @@ int main(int argc, char **argv)
/* Set option defaults */
show = set = systohc = hctosys = systz = adjust = noadjfile = predict =
- compare = FALSE;
+ compare = get = FALSE;
getepoch = setepoch = utc = local_opt = directisa = testing = debug = FALSE;
#ifdef __alpha__
ARCconsole = Jensen = SRM = funky_toy = badyear = FALSE;
@@ -1839,6 +1813,9 @@ int main(int argc, char **argv)
case OPT_PREDICT_HC:
predict = TRUE; /* --predict-hc */
break;
+ case OPT_GET:
+ get = TRUE; /* --get */
+ break;
#ifdef __linux__
case 'f':
rtc_dev_name = optarg; /* --rtc */
@@ -1896,7 +1873,7 @@ int main(int argc, char **argv)
}
if (!(show | set | systohc | hctosys | systz | adjust | getepoch
- | setepoch | predict | compare))
+ | setepoch | predict | compare | get))
show = 1; /* default to show */
if (getuid() == 0)
@@ -1953,7 +1930,7 @@ int main(int argc, char **argv)
} else
rc = manipulate_clock(show, adjust, noadjfile, set, set_time,
hctosys, systohc, systz, startup_time, utc,
- local_opt, testing, predict);
+ local_opt, testing, predict, get);
hwclock_exit(rc);
return rc; /* Not reached */
--
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