[PATCH] HZ free ntp

Distangle the NTP update from HZ.  This is necessary for dynamic tick enabled
kernels.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 36 insertions, 16 deletions

diff --git a/include/linux/timex.h b/include/linux/timex.h
index 9a24e500c311..da929dbbea2a 100644
--- a/include/linux/timex.h
+++ b/include/linux/timex.h
@@ -286,6 +286,13 @@ static inline void time_interpolator_update(long delta_nsec)
 
 #define TICK_LENGTH_SHIFT       32
 
+#ifdef CONFIG_NO_HZ
+#define NTP_INTERVAL_FREQ  (2)
+#else
+#define NTP_INTERVAL_FREQ  (HZ)
+#endif
+#define NTP_INTERVAL_LENGTH (NSEC_PER_SEC/NTP_INTERVAL_FREQ)
+
 /* Returns how long ticks are at present, in ns / 2^(SHIFT_SCALE-10). */
 extern u64 current_tick_length(void);
 
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index f44e499e8fca..80666f6cd4f9 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -128,15 +128,20 @@ EXPORT_SYMBOL_GPL(ktime_get_ts);
 static void hrtimer_get_softirq_time(struct hrtimer_base *base)
 {
         ktime_t xtim, tomono;
+        struct timespec xts;
         unsigned long seq;
 
         do {
                 seq = read_seqbegin(&xtime_lock);
-                xtim = timespec_to_ktime(xtime);
-                tomono = timespec_to_ktime(wall_to_monotonic);
-
+#ifdef CONFIG_NO_HZ
+                getnstimeofday(&xts);
+#else
+                xts = xtime;
+#endif
         } while (read_seqretry(&xtime_lock, seq));
 
+        xtim = timespec_to_ktime(xts);
+        tomono = timespec_to_ktime(wall_to_monotonic);
         base[CLOCK_REALTIME].softirq_time = xtim;
         base[CLOCK_MONOTONIC].softirq_time = ktime_add(xtim, tomono);
 }
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 3afeaa3a73f9..eb12509e00bd 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -24,7 +24,7 @@ static u64 tick_length, tick_length_base;
 
 #define MAX_TICKADJ             500             /* microsecs */
 #define MAX_TICKADJ_SCALED      (((u64)(MAX_TICKADJ * NSEC_PER_USEC) << \
-                                  TICK_LENGTH_SHIFT) / HZ)
+                                  TICK_LENGTH_SHIFT) / NTP_INTERVAL_FREQ)
 
 /*
  * phase-lock loop variables
@@ -46,13 +46,17 @@ long time_adjust;
 
 static void ntp_update_frequency(void)
 {
-        tick_length_base = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << TICK_LENGTH_SHIFT;
-        tick_length_base += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT;
-        tick_length_base += (s64)time_freq << (TICK_LENGTH_SHIFT - SHIFT_NSEC);
+        u64 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
+                                << TICK_LENGTH_SHIFT;
+        second_length += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT;
+        second_length += (s64)time_freq << (TICK_LENGTH_SHIFT - SHIFT_NSEC);
 
-        do_div(tick_length_base, HZ);
+        tick_length_base = second_length;
 
-        tick_nsec = tick_length_base >> TICK_LENGTH_SHIFT;
+        do_div(second_length, HZ);
+        tick_nsec = second_length >> TICK_LENGTH_SHIFT;
+
+        do_div(tick_length_base, NTP_INTERVAL_FREQ);
 }
 
 /**
@@ -162,7 +166,7 @@ void second_overflow(void)
                         tick_length -= MAX_TICKADJ_SCALED;
                 } else {
                         tick_length += (s64)(time_adjust * NSEC_PER_USEC /
-                                             HZ) << TICK_LENGTH_SHIFT;
+                                        NTP_INTERVAL_FREQ) << TICK_LENGTH_SHIFT;
                         time_adjust = 0;
                 }
         }
@@ -239,7 +243,8 @@ int do_adjtimex(struct timex *txc)
                     result = -EINVAL;
                     goto leave;
                 }
-                time_freq = ((s64)txc->freq * NSEC_PER_USEC) >> (SHIFT_USEC - SHIFT_NSEC);
+                time_freq = ((s64)txc->freq * NSEC_PER_USEC)
+                                >> (SHIFT_USEC - SHIFT_NSEC);
             }
 
             if (txc->modes & ADJ_MAXERROR) {
@@ -309,7 +314,8 @@ int do_adjtimex(struct timex *txc)
                     freq_adj += time_freq;
                     freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC);
                     time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC);
-                    time_offset = (time_offset / HZ) << SHIFT_UPDATE;
+                    time_offset = (time_offset / NTP_INTERVAL_FREQ)
+                                        << SHIFT_UPDATE;
                 } /* STA_PLL */
             } /* txc->modes & ADJ_OFFSET */
             if (txc->modes & ADJ_TICK)
@@ -324,8 +330,10 @@ leave:	if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)
         if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
             txc->offset    = save_adjust;
         else
-            txc->offset    = shift_right(time_offset, SHIFT_UPDATE) * HZ / 1000;
-        txc->freq          = (time_freq / NSEC_PER_USEC) << (SHIFT_USEC - SHIFT_NSEC);
+            txc->offset    = shift_right(time_offset, SHIFT_UPDATE)
+                                * NTP_INTERVAL_FREQ / 1000;
+        txc->freq          = (time_freq / NSEC_PER_USEC)
+                                << (SHIFT_USEC - SHIFT_NSEC);
         txc->maxerror      = time_maxerror;
         txc->esterror      = time_esterror;
         txc->status        = time_status;
diff --git a/kernel/timer.c b/kernel/timer.c
index 4902181e10e6..4f9cc2a48beb 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -890,7 +890,7 @@ void __init timekeeping_init(void)
         ntp_clear();
 
         clock = clocksource_get_next();
-        clocksource_calculate_interval(clock, tick_nsec);
+        clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
         clock->cycle_last = clocksource_read(clock);
 
         write_sequnlock_irqrestore(&xtime_lock, flags);
@@ -1092,7 +1092,7 @@ static void update_wall_time(void)
         if (change_clocksource()) {
                 clock->error = 0;
                 clock->xtime_nsec = 0;
-                clocksource_calculate_interval(clock, tick_nsec);
+                clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
         }
 }