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Subject[NTP 5/9] add time_adjust to tick length
This folds update_ntp_one_tick() into second_overflow() and adds
time_adjust to the tick length, this makes time_next_adjust unnecessary.
This slightly changes the adjtime() behaviour, instead of applying it to
the next tick, it's applied to the next second.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
---
include/linux/timex.h | 1
kernel/time/ntp.c | 71 ++++++++++++--------------------------------------
kernel/timer.c | 2 -
3 files changed, 18 insertions(+), 56 deletions(-)
Index: linux-2.6-mm/include/linux/timex.h
===================================================================
--- linux-2.6-mm.orig/include/linux/timex.h
+++ linux-2.6-mm/include/linux/timex.h
@@ -216,7 +216,6 @@ extern long time_freq; /* frequency off
extern long time_reftime; /* time at last adjustment (s) */

extern long time_adjust; /* The amount of adjtime left */
-extern long time_next_adjust; /* Value for time_adjust at next tick */

extern void ntp_clear(void);
extern void ntp_update_frequency(void);
Index: linux-2.6-mm/kernel/time/ntp.c
===================================================================
--- linux-2.6-mm.orig/kernel/time/ntp.c
+++ linux-2.6-mm/kernel/time/ntp.c
@@ -28,8 +28,9 @@ unsigned long tick_usec = TICK_USEC; /
unsigned long tick_nsec; /* ACTHZ period (nsec) */
static u64 tick_length, tick_length_base;

-/* Don't completely fail for HZ > 500. */
-int tickadj = 500/HZ ? : 1; /* microsecs */
+#define MAX_TICKADJ 500 /* microsecs */
+#define MAX_TICKADJ_SCALED (((u64)(MAX_TICKADJ * NSEC_PER_USEC) << \
+ TICK_LENGTH_SHIFT) / HZ)

/*
* phase-lock loop variables
@@ -46,7 +47,6 @@ long time_esterror = NTP_PHASE_LIMIT; /*
long time_freq; /* frequency offset (scaled ppm)*/
long time_reftime; /* time at last adjustment (s) */
long time_adjust;
-long time_next_adjust;

/**
* ntp_clear - Clears the NTP state variables
@@ -166,46 +166,19 @@ void second_overflow(void)
time_adj = max(time_adj, ((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC);
time_offset -= time_adj;
tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE);
-}
-
-/*
- * Returns how many microseconds we need to add to xtime this tick
- * in doing an adjustment requested with adjtime.
- */
-static long adjtime_adjustment(void)
-{
- long time_adjust_step;
-
- time_adjust_step = time_adjust;
- if (time_adjust_step) {
- /*
- * We are doing an adjtime thing. Prepare time_adjust_step to
- * be within bounds. Note that a positive time_adjust means we
- * want the clock to run faster.
- *
- * Limit the amount of the step to be in the range
- * -tickadj .. +tickadj
- */
- time_adjust_step = min(time_adjust_step, (long)tickadj);
- time_adjust_step = max(time_adjust_step, (long)-tickadj);
- }
- return time_adjust_step;
-}
-
-/* in the NTP reference this is called "hardclock()" */
-void update_ntp_one_tick(void)
-{
- long time_adjust_step;

- time_adjust_step = adjtime_adjustment();
- if (time_adjust_step)
- /* Reduce by this step the amount of time left */
- time_adjust -= time_adjust_step;
-
- /* Changes by adjtime() do not take effect till next tick. */
- if (time_next_adjust != 0) {
- time_adjust = time_next_adjust;
- time_next_adjust = 0;
+ if (unlikely(time_adjust)) {
+ if (time_adjust > MAX_TICKADJ) {
+ time_adjust -= MAX_TICKADJ;
+ tick_length += MAX_TICKADJ_SCALED;
+ } else if (time_adjust < -MAX_TICKADJ) {
+ time_adjust += MAX_TICKADJ;
+ tick_length -= MAX_TICKADJ_SCALED;
+ } else {
+ time_adjust = 0;
+ tick_length += (s64)(time_adjust * NSEC_PER_USEC /
+ HZ) << TICK_LENGTH_SHIFT;
+ }
}
}

@@ -219,14 +192,7 @@ void update_ntp_one_tick(void)
*/
u64 current_tick_length(void)
{
- u64 ret;
-
- /* calculate the finest interval NTP will allow.
- */
- ret = tick_length;
- ret += (u64)(adjtime_adjustment() * 1000) << TICK_LENGTH_SHIFT;
-
- return ret;
+ return tick_length;
}


@@ -269,7 +235,7 @@ int do_adjtimex(struct timex *txc)
result = time_state; /* mostly `TIME_OK' */

/* Save for later - semantics of adjtime is to return old value */
- save_adjust = time_next_adjust ? time_next_adjust : time_adjust;
+ save_adjust = time_adjust;

#if 0 /* STA_CLOCKERR is never set yet */
time_status &= ~STA_CLOCKERR; /* reset STA_CLOCKERR */
@@ -316,8 +282,7 @@ int do_adjtimex(struct timex *txc)
if (txc->modes & ADJ_OFFSET) { /* values checked earlier */
if (txc->modes == ADJ_OFFSET_SINGLESHOT) {
/* adjtime() is independent from ntp_adjtime() */
- if ((time_next_adjust = txc->offset) == 0)
- time_adjust = 0;
+ time_adjust = txc->offset;
}
else if (time_status & STA_PLL) {
ltemp = txc->offset;
Index: linux-2.6-mm/kernel/timer.c
===================================================================
--- linux-2.6-mm.orig/kernel/timer.c
+++ linux-2.6-mm/kernel/timer.c
@@ -943,8 +943,6 @@ static void update_wall_time(void)
/* interpolator bits */
time_interpolator_update(clock->xtime_interval
>> clock->shift);
- /* increment the NTP state machine */
- update_ntp_one_tick();

/* accumulate error between NTP and clock interval */
clock->error += current_tick_length();
--

-
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