All,
This patch breaks up the complex nesting of code in ntp_adjtimex() by
creating a ntp_hardupdate() function and simplifying some of the logic.
This also follows the documented NTP spec somewhat better.
Any comments or feedback would be greatly appreciated.
thanks
-john
linux-2.6.13-rc3_timeofday-ntp-part4_B4.patch
============================================
diff --git a/kernel/ntp.c b/kernel/ntp.c
--- a/kernel/ntp.c
+++ b/kernel/ntp.c
@@ -69,6 +69,9 @@ static long time_reftime;
long time_adjust;
static long time_next_adjust;
+/* Required to safely shift negative values */
+#define shiftR(x,s) (x < 0) ? (-((-x) >> (s))) : ((x) >> (s))
+
int ntp_advance(void)
{
long time_adjust_step, delta_nsec;
@@ -244,12 +247,79 @@ void second_overflow(void)
#endif
}
+/**
+ * ntp_hardupdate - Calculates the offset and freq values
+ * offset: current offset
+ * tv: timeval holding the current time
+ *
+ * Private function, called only by ntp_adjtimex
+ *
+ * This function is called when an offset adjustment is requested.
+ * It calculates the offset adjustment and manipulates the
+ * frequency adjustement accordingly.
+ */
+static int ntp_hardupdate(long offset, struct timespec tv)
+{
+ int ret;
+ long current_offset, interval;
+
+ ret = 0;
+ if (!(time_status & STA_PLL))
+ return ret;
+
+ current_offset = offset;
+ /* Make sure offset is bounded by MAXPHASE */
+ current_offset = min(current_offset, MAXPHASE);
+ current_offset = max(current_offset, -MAXPHASE);
+ time_offset = current_offset << SHIFT_UPDATE;
+
+ if (time_status & STA_FREQHOLD || time_reftime == 0)
+ time_reftime = tv.tv_sec;
+
+ /* calculate seconds since last call to hardupdate */
+ interval = tv.tv_sec - time_reftime;
+ time_reftime = tv.tv_sec;
+
+ /*
+ * Select whether the frequency is to be controlled
+ * and in which mode (PLL or FLL). Clamp to the operating
+ * range. Ugly multiply/divide should be replaced someday.
+ */
+ if ((time_status & STA_FLL) && (interval >= MINSEC)) {
+ long offset_ppm;
+
+ offset_ppm = time_offset / interval;
+ offset_ppm <<= (SHIFT_USEC - SHIFT_UPDATE);
+
+ time_freq += shiftR(offset_ppm, SHIFT_KH);
+
+ } else if ((time_status & STA_PLL) && (interval < MAXSEC)) {
+ long damping, offset_ppm;
+
+ offset_ppm = offset * interval;
+
+ damping = (2 * time_constant) + SHIFT_KF - SHIFT_USEC;
+
+ time_freq += shiftR(offset_ppm, damping);
+
+ } else { /* calibration interval out of bounds (p. 12) */
+ ret = TIME_ERROR;
+ }
+
+ /* bound time_freq */
+ time_freq = min(time_freq, time_tolerance);
+ time_freq = max(time_freq, -time_tolerance);
+
+ return ret;
+}
+
+
/* adjtimex mainly allows reading (and writing, if superuser) of
* kernel time-keeping variables. used by xntpd.
*/
int ntp_adjtimex(struct timex *txc)
{
- long ltemp, mtemp, save_adjust;
+ long save_adjust;
int result;
/* Now we validate the data before disabling interrupts */
@@ -321,63 +391,9 @@ int ntp_adjtimex(struct timex *txc)
/* adjtime() is independent from ntp_adjtime() */
if ((time_next_adjust = txc->offset) == 0)
time_adjust = 0;
- } else if (time_status & STA_PLL) {
- ltemp = txc->offset;
-
- /*
- * Scale the phase adjustment and
- * clamp to the operating range.
- */
- if (ltemp > MAXPHASE)
- time_offset = MAXPHASE << SHIFT_UPDATE;
- else if (ltemp < -MAXPHASE)
- time_offset = -(MAXPHASE
- << SHIFT_UPDATE);
- else
- time_offset = ltemp << SHIFT_UPDATE;
-
- /*
- * Select whether the frequency is to be controlled
- * and in which mode (PLL or FLL). Clamp to the operating
- * range. Ugly multiply/divide should be replaced someday.
- */
-
- if (time_status & STA_FREQHOLD || time_reftime == 0)
- time_reftime = xtime.tv_sec;
-
- mtemp = xtime.tv_sec - time_reftime;
- time_reftime = xtime.tv_sec;
-
- if (time_status & STA_FLL) {
- if (mtemp >= MINSEC) {
- ltemp = (time_offset / mtemp) << (SHIFT_USEC -
- SHIFT_UPDATE);
- if (ltemp < 0)
- time_freq -= -ltemp >> SHIFT_KH;
- else
- time_freq += ltemp >> SHIFT_KH;
- } else /* calibration interval too short (p. 12) */
- result = TIME_ERROR;
- } else { /* PLL mode */
- if (mtemp < MAXSEC) {
- ltemp *= mtemp;
- if (ltemp < 0)
- time_freq -= -ltemp >> (time_constant +
- time_constant +
- SHIFT_KF - SHIFT_USEC);
- else
- time_freq += ltemp >> (time_constant +
- time_constant +
- SHIFT_KF - SHIFT_USEC);
- } else /* calibration interval too long (p. 12) */
- result = TIME_ERROR;
- }
-
- if (time_freq > time_tolerance)
- time_freq = time_tolerance;
- else if (time_freq < -time_tolerance)
- time_freq = -time_tolerance;
- } /* STA_PLL */
+ else if (ntp_hardupdate(txc->offset, xtime))
+ result = TIME_ERROR;
+ }
} /* txc->modes & ADJ_OFFSET */
if (txc->modes & ADJ_TICK) {
-
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