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.
Signed-off-by: J William Piggott <elseifthen@xxxxxxx>
---
sys-utils/hwclock.c | 99 +++++++++++++++++++++++++++++------------------------
1 file changed, 55 insertions(+), 44 deletions(-)
diff --git a/sys-utils/hwclock.c b/sys-utils/hwclock.c
index 474e04f..ef7bd89 100644
--- a/sys-utils/hwclock.c
+++ b/sys-utils/hwclock.c
@@ -437,6 +437,45 @@ mktime_tz(struct tm tm, const bool universal,
}
/*
+ * Do the drift adjustment calculation.
+ *
+ * The way we have to set the clock, we need the adjustment in two parts:
+ *
+ * 1) an integer number of seconds (return as *adjustment_p)
+ * 2) a positive fraction of a second (less than 1) (return as *retro_p)
+ *
+ * The sum of these two values is the adjustment needed. Positive means to
+ * advance the clock or insert seconds. Negative means to retard the clock
+ * or remove seconds.
+ */
+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)
+{
+ 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;
+ 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);
+ }
+}
+
+/*
* Read the hardware clock and return the current time via <tm> argument.
*
* Use the method indicated by <method> argument to access the hardware
@@ -793,7 +832,7 @@ static int interpret_date_string(const char *date_opt, time_t * const time_p)
}
/*
- * Set the System Clock to time 'newtime'.
+ * Set the System Clock to time 'newtime' plus any drift correction.
*
* Also set the kernel time zone value to the value indicated by the TZ
* environment variable and/or /usr/lib/zoneinfo/, interpreted as tzset()
@@ -807,8 +846,8 @@ 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,
- const bool testing)
+set_system_clock(struct adjtime *adjtime_p, const bool hclock_valid,
+ const time_t newtime, const bool testing)
{
int retcode;
@@ -834,6 +873,16 @@ set_system_clock(const bool hclock_valid, const time_t newtime,
if (broken->tm_isdst)
minuteswest -= 60;
#endif
+ int adjustment;
+ /* Number of seconds the Hardware Clock has drifted. */
+ double retro;
+ /* Fraction of second the Hardware Clock has drifted. */
+ calculate_adjustment(adjtime_p->drift_factor,
+ adjtime_p->last_adj_time,
+ adjtime_p->not_adjusted,
+ newtime, &adjustment, &retro);
+ tv.tv_sec += adjustment;
+ tv.tv_usec += retro * 1E6;
if (debug) {
printf(_("Calling settimeofday:\n"));
@@ -1072,45 +1121,6 @@ adjust_drift_factor(struct adjtime *adjtime_p,
}
/*
- * Do the drift adjustment calculation.
- *
- * The way we have to set the clock, we need the adjustment in two parts:
- *
- * 1) an integer number of seconds (return as *adjustment_p)
- * 2) a positive fraction of a second (less than 1) (return as *retro_p)
- *
- * The sum of these two values is the adjustment needed. Positive means to
- * advance the clock or insert seconds. Negative means to retard the clock
- * or remove seconds.
- */
-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)
-{
- 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;
- 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);
- }
-}
-
-/*
* Write the contents of the <adjtime> structure to its disk file.
*
* But if the contents are clean (unchanged since read from disk), don't
@@ -1313,7 +1323,8 @@ manipulate_clock(const bool show, const bool adjust, const bool noadjfile,
}
if (!noadjfile
- && (adjust || set || systohc || (!utc && !local_opt) || predict)) {
+ && (adjust || set || systohc ||
+ hctosys || (!utc && !local_opt) || predict)) {
rc = read_adjtime(&adjtime);
if (rc)
return rc;
@@ -1393,7 +1404,7 @@ manipulate_clock(const bool show, const bool adjust, const bool noadjfile,
hclock_valid, hclocktime, (double)
read_time.tv_usec / 1E6);
} else if (hctosys) {
- rc = set_system_clock(hclock_valid, hclocktime, testing);
+ rc = set_system_clock(&adjtime, hclock_valid, hclocktime, testing);
if (rc) {
printf(_("Unable to set system clock.\n"));
return rc;
--
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