[PATCH] ntp: 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>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 18 insertions, 55 deletions

diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 238ce47ef09d..65223b7ed810 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -22,8 +22,9 @@ unsigned long tick_usec = TICK_USEC; 		/* USER_HZ period (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
@@ -40,7 +41,6 @@ long time_esterror = NTP_PHASE_LIMIT;	/* estimated error (us)		*/
 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
@@ -160,46 +160,19 @@ 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;
+                }
         }
 }
 
@@ -213,14 +186,7 @@ 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;
 }
 
 
@@ -263,7 +229,7 @@ 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 */
@@ -310,8 +276,7 @@ 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;
diff --git a/kernel/timer.c b/kernel/timer.c
index 78d3fa10fcd6..654dd5df2417 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -937,8 +937,6 @@ 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();