7 files changed, 287 insertions, 122 deletions

diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 620b58abdc32..20a8920029ee 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -20,6 +20,8 @@
 #include <linux/sysdev.h>
 #include <linux/tick.h>
 
+#include "tick-internal.h"
+
 /* The registered clock event devices */
 static LIST_HEAD(clockevent_devices);
 static LIST_HEAD(clockevents_released);
@@ -37,10 +39,9 @@ static DEFINE_SPINLOCK(clockevents_lock);
  *
  * Math helper, returns latch value converted to nanoseconds (bound checked)
  */
-unsigned long clockevent_delta2ns(unsigned long latch,
-                                  struct clock_event_device *evt)
+u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
 {
-        u64 clc = ((u64) latch << evt->shift);
+        u64 clc = (u64) latch << evt->shift;
 
         if (unlikely(!evt->mult)) {
                 evt->mult = 1;
@@ -50,10 +51,10 @@ unsigned long clockevent_delta2ns(unsigned long latch,
         do_div(clc, evt->mult);
         if (clc < 1000)
                 clc = 1000;
-        if (clc > LONG_MAX)
-                clc = LONG_MAX;
+        if (clc > KTIME_MAX)
+                clc = KTIME_MAX;
 
-        return (unsigned long) clc;
+        return clc;
 }
 EXPORT_SYMBOL_GPL(clockevent_delta2ns);
 
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 5e18c6ab2c6a..e85c23404d34 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -39,7 +39,7 @@ void timecounter_init(struct timecounter *tc,
         tc->cycle_last = cc->read(cc);
         tc->nsec = start_tstamp;
 }
-EXPORT_SYMBOL(timecounter_init);
+EXPORT_SYMBOL_GPL(timecounter_init);
 
 /**
  * timecounter_read_delta - get nanoseconds since last call of this function
@@ -83,7 +83,7 @@ u64 timecounter_read(struct timecounter *tc)
 
         return nsec;
 }
-EXPORT_SYMBOL(timecounter_read);
+EXPORT_SYMBOL_GPL(timecounter_read);
 
 u64 timecounter_cyc2time(struct timecounter *tc,
                          cycle_t cycle_tstamp)
@@ -105,7 +105,60 @@ u64 timecounter_cyc2time(struct timecounter *tc,
 
         return nsec;
 }
-EXPORT_SYMBOL(timecounter_cyc2time);
+EXPORT_SYMBOL_GPL(timecounter_cyc2time);
+
+/**
+ * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks
+ * @mult:       pointer to mult variable
+ * @shift:      pointer to shift variable
+ * @from:       frequency to convert from
+ * @to:         frequency to convert to
+ * @minsec:     guaranteed runtime conversion range in seconds
+ *
+ * The function evaluates the shift/mult pair for the scaled math
+ * operations of clocksources and clockevents.
+ *
+ * @to and @from are frequency values in HZ. For clock sources @to is
+ * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock
+ * event @to is the counter frequency and @from is NSEC_PER_SEC.
+ *
+ * The @minsec conversion range argument controls the time frame in
+ * seconds which must be covered by the runtime conversion with the
+ * calculated mult and shift factors. This guarantees that no 64bit
+ * overflow happens when the input value of the conversion is
+ * multiplied with the calculated mult factor. Larger ranges may
+ * reduce the conversion accuracy by chosing smaller mult and shift
+ * factors.
+ */
+void
+clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec)
+{
+        u64 tmp;
+        u32 sft, sftacc= 32;
+
+        /*
+         * Calculate the shift factor which is limiting the conversion
+         * range:
+         */
+        tmp = ((u64)minsec * from) >> 32;
+        while (tmp) {
+                tmp >>=1;
+                sftacc--;
+        }
+
+        /*
+         * Find the conversion shift/mult pair which has the best
+         * accuracy and fits the maxsec conversion range:
+         */
+        for (sft = 32; sft > 0; sft--) {
+                tmp = (u64) to << sft;
+                do_div(tmp, from);
+                if ((tmp >> sftacc) == 0)
+                        break;
+        }
+        *mult = tmp;
+        *shift = sft;
+}
 
 /*[Clocksource internal variables]---------
  * curr_clocksource:
@@ -413,6 +466,47 @@ void clocksource_touch_watchdog(void)
         clocksource_resume_watchdog();
 }
 
+/**
+ * clocksource_max_deferment - Returns max time the clocksource can be deferred
+ * @cs:         Pointer to clocksource
+ *
+ */
+static u64 clocksource_max_deferment(struct clocksource *cs)
+{
+        u64 max_nsecs, max_cycles;
+
+        /*
+         * Calculate the maximum number of cycles that we can pass to the
+         * cyc2ns function without overflowing a 64-bit signed result. The
+         * maximum number of cycles is equal to ULLONG_MAX/cs->mult which
+         * is equivalent to the below.
+         * max_cycles < (2^63)/cs->mult
+         * max_cycles < 2^(log2((2^63)/cs->mult))
+         * max_cycles < 2^(log2(2^63) - log2(cs->mult))
+         * max_cycles < 2^(63 - log2(cs->mult))
+         * max_cycles < 1 << (63 - log2(cs->mult))
+         * Please note that we add 1 to the result of the log2 to account for
+         * any rounding errors, ensure the above inequality is satisfied and
+         * no overflow will occur.
+         */
+        max_cycles = 1ULL << (63 - (ilog2(cs->mult) + 1));
+
+        /*
+         * The actual maximum number of cycles we can defer the clocksource is
+         * determined by the minimum of max_cycles and cs->mask.
+         */
+        max_cycles = min_t(u64, max_cycles, (u64) cs->mask);
+        max_nsecs = clocksource_cyc2ns(max_cycles, cs->mult, cs->shift);
+
+        /*
+         * To ensure that the clocksource does not wrap whilst we are idle,
+         * limit the time the clocksource can be deferred by 12.5%. Please
+         * note a margin of 12.5% is used because this can be computed with
+         * a shift, versus say 10% which would require division.
+         */
+        return max_nsecs - (max_nsecs >> 5);
+}
+
 #ifdef CONFIG_GENERIC_TIME
 
 /**
@@ -511,6 +605,9 @@ static void clocksource_enqueue(struct clocksource *cs)
  */
 int clocksource_register(struct clocksource *cs)
 {
+        /* calculate max idle time permitted for this clocksource */
+        cs->max_idle_ns = clocksource_max_deferment(cs);
+
         mutex_lock(&clocksource_mutex);
         clocksource_enqueue(cs);
         clocksource_select();
@@ -580,7 +677,7 @@ sysfs_show_current_clocksources(struct sys_device *dev,
  * @count:      length of buffer
  *
  * Takes input from sysfs interface for manually overriding the default
- * clocksource selction.
+ * clocksource selection.
  */
 static ssize_t sysfs_override_clocksource(struct sys_device *dev,
                                           struct sysdev_attribute *attr,
diff --git a/kernel/time/tick-oneshot.c b/kernel/time/tick-oneshot.c
index a96c0e2b89cf..0a8a213016f0 100644
--- a/kernel/time/tick-oneshot.c
+++ b/kernel/time/tick-oneshot.c
@@ -50,9 +50,9 @@ int tick_dev_program_event(struct clock_event_device *dev, ktime_t expires,
                                 dev->min_delta_ns += dev->min_delta_ns >> 1;
 
                         printk(KERN_WARNING
-                               "CE: %s increasing min_delta_ns to %lu nsec\n",
+                               "CE: %s increasing min_delta_ns to %llu nsec\n",
                                dev->name ? dev->name : "?",
-                               dev->min_delta_ns << 1);
+                               (unsigned long long) dev->min_delta_ns << 1);
 
                         i = 0;
                 }
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 89aed5933ed4..f992762d7f51 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -134,18 +134,13 @@ __setup("nohz=", setup_tick_nohz);
  * value. We do this unconditionally on any cpu, as we don't know whether the
  * cpu, which has the update task assigned is in a long sleep.
  */
-static void tick_nohz_update_jiffies(void)
+static void tick_nohz_update_jiffies(ktime_t now)
 {
         int cpu = smp_processor_id();
         struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
         unsigned long flags;
-        ktime_t now;
-
-        if (!ts->tick_stopped)
-                return;
 
         cpumask_clear_cpu(cpu, nohz_cpu_mask);
-        now = ktime_get();
         ts->idle_waketime = now;
 
         local_irq_save(flags);
@@ -155,20 +150,17 @@ static void tick_nohz_update_jiffies(void)
         touch_softlockup_watchdog();
 }
 
-static void tick_nohz_stop_idle(int cpu)
+static void tick_nohz_stop_idle(int cpu, ktime_t now)
 {
         struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+        ktime_t delta;
 
-        if (ts->idle_active) {
-                ktime_t now, delta;
-                now = ktime_get();
-                delta = ktime_sub(now, ts->idle_entrytime);
-                ts->idle_lastupdate = now;
-                ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
-                ts->idle_active = 0;
+        delta = ktime_sub(now, ts->idle_entrytime);
+        ts->idle_lastupdate = now;
+        ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
+        ts->idle_active = 0;
 
-                sched_clock_idle_wakeup_event(0);
-        }
+        sched_clock_idle_wakeup_event(0);
 }
 
 static ktime_t tick_nohz_start_idle(struct tick_sched *ts)
@@ -216,6 +208,7 @@ void tick_nohz_stop_sched_tick(int inidle)
         struct tick_sched *ts;
         ktime_t last_update, expires, now;
         struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
+        u64 time_delta;
         int cpu;
 
         local_irq_save(flags);
@@ -263,7 +256,7 @@ void tick_nohz_stop_sched_tick(int inidle)
 
                 if (ratelimit < 10) {
                         printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n",
-                               local_softirq_pending());
+                               (unsigned int) local_softirq_pending());
                         ratelimit++;
                 }
                 goto end;
@@ -275,14 +268,18 @@ void tick_nohz_stop_sched_tick(int inidle)
                 seq = read_seqbegin(&xtime_lock);
                 last_update = last_jiffies_update;
                 last_jiffies = jiffies;
+                time_delta = timekeeping_max_deferment();
         } while (read_seqretry(&xtime_lock, seq));
 
-        /* Get the next timer wheel timer */
-        next_jiffies = get_next_timer_interrupt(last_jiffies);
-        delta_jiffies = next_jiffies - last_jiffies;
-
-        if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu))
+        if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) ||
+            arch_needs_cpu(cpu)) {
+                next_jiffies = last_jiffies + 1;
                 delta_jiffies = 1;
+        } else {
+                /* Get the next timer wheel timer */
+                next_jiffies = get_next_timer_interrupt(last_jiffies);
+                delta_jiffies = next_jiffies - last_jiffies;
+        }
         /*
          * Do not stop the tick, if we are only one off
          * or if the cpu is required for rcu
@@ -294,22 +291,51 @@ void tick_nohz_stop_sched_tick(int inidle)
         if ((long)delta_jiffies >= 1) {
 
                 /*
-                * calculate the expiry time for the next timer wheel
-                * timer
-                */
-                expires = ktime_add_ns(last_update, tick_period.tv64 *
-                                   delta_jiffies);
-
-                /*
                  * If this cpu is the one which updates jiffies, then
                  * give up the assignment and let it be taken by the
                  * cpu which runs the tick timer next, which might be
                  * this cpu as well. If we don't drop this here the
                  * jiffies might be stale and do_timer() never
-                 * invoked.
+                 * invoked. Keep track of the fact that it was the one
+                 * which had the do_timer() duty last. If this cpu is
+                 * the one which had the do_timer() duty last, we
+                 * limit the sleep time to the timekeeping
+                 * max_deferement value which we retrieved
+                 * above. Otherwise we can sleep as long as we want.
                  */
-                if (cpu == tick_do_timer_cpu)
+                if (cpu == tick_do_timer_cpu) {
                         tick_do_timer_cpu = TICK_DO_TIMER_NONE;
+                        ts->do_timer_last = 1;
+                } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) {
+                        time_delta = KTIME_MAX;
+                        ts->do_timer_last = 0;
+                } else if (!ts->do_timer_last) {
+                        time_delta = KTIME_MAX;
+                }
+
+                /*
+                 * calculate the expiry time for the next timer wheel
+                 * timer. delta_jiffies >= NEXT_TIMER_MAX_DELTA signals
+                 * that there is no timer pending or at least extremely
+                 * far into the future (12 days for HZ=1000). In this
+                 * case we set the expiry to the end of time.
+                 */
+                if (likely(delta_jiffies < NEXT_TIMER_MAX_DELTA)) {
+                        /*
+                         * Calculate the time delta for the next timer event.
+                         * If the time delta exceeds the maximum time delta
+                         * permitted by the current clocksource then adjust
+                         * the time delta accordingly to ensure the
+                         * clocksource does not wrap.
+                         */
+                        time_delta = min_t(u64, time_delta,
+                                           tick_period.tv64 * delta_jiffies);
+                }
+
+                if (time_delta < KTIME_MAX)
+                        expires = ktime_add_ns(last_update, time_delta);
+                else
+                        expires.tv64 = KTIME_MAX;
 
                 if (delta_jiffies > 1)
                         cpumask_set_cpu(cpu, nohz_cpu_mask);
@@ -342,22 +368,19 @@ void tick_nohz_stop_sched_tick(int inidle)
 
                 ts->idle_sleeps++;
 
+                /* Mark expires */
+                ts->idle_expires = expires;
+
                 /*
-                 * delta_jiffies >= NEXT_TIMER_MAX_DELTA signals that
-                 * there is no timer pending or at least extremly far
-                 * into the future (12 days for HZ=1000). In this case
-                 * we simply stop the tick timer:
+                 * If the expiration time == KTIME_MAX, then
+                 * in this case we simply stop the tick timer.
                  */
-                if (unlikely(delta_jiffies >= NEXT_TIMER_MAX_DELTA)) {
-                        ts->idle_expires.tv64 = KTIME_MAX;
+                 if (unlikely(expires.tv64 == KTIME_MAX)) {
                         if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
                                 hrtimer_cancel(&ts->sched_timer);
                         goto out;
                 }
 
-                /* Mark expiries */
-                ts->idle_expires = expires;
-
                 if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
                         hrtimer_start(&ts->sched_timer, expires,
                                       HRTIMER_MODE_ABS_PINNED);
@@ -436,7 +459,11 @@ void tick_nohz_restart_sched_tick(void)
         ktime_t now;
 
         local_irq_disable();
-        tick_nohz_stop_idle(cpu);
+        if (ts->idle_active || (ts->inidle && ts->tick_stopped))
+                now = ktime_get();
+
+        if (ts->idle_active)
+                tick_nohz_stop_idle(cpu, now);
 
         if (!ts->inidle || !ts->tick_stopped) {
                 ts->inidle = 0;
@@ -450,7 +477,6 @@ void tick_nohz_restart_sched_tick(void)
 
         /* Update jiffies first */
         select_nohz_load_balancer(0);
-        now = ktime_get();
         tick_do_update_jiffies64(now);
         cpumask_clear_cpu(cpu, nohz_cpu_mask);
 
@@ -584,22 +610,18 @@ static void tick_nohz_switch_to_nohz(void)
  * timer and do not touch the other magic bits which need to be done
  * when idle is left.
  */
-static void tick_nohz_kick_tick(int cpu)
+static void tick_nohz_kick_tick(int cpu, ktime_t now)
 {
 #if 0
         /* Switch back to 2.6.27 behaviour */
 
         struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
-        ktime_t delta, now;
-
-        if (!ts->tick_stopped)
-                return;
+        ktime_t delta;
 
         /*
          * Do not touch the tick device, when the next expiry is either
          * already reached or less/equal than the tick period.
          */
-        now = ktime_get();
         delta = ktime_sub(hrtimer_get_expires(&ts->sched_timer), now);
         if (delta.tv64 <= tick_period.tv64)
                 return;
@@ -608,9 +630,26 @@ static void tick_nohz_kick_tick(int cpu)
 #endif
 }
 
+static inline void tick_check_nohz(int cpu)
+{
+        struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+        ktime_t now;
+
+        if (!ts->idle_active && !ts->tick_stopped)
+                return;
+        now = ktime_get();
+        if (ts->idle_active)
+                tick_nohz_stop_idle(cpu, now);
+        if (ts->tick_stopped) {
+                tick_nohz_update_jiffies(now);
+                tick_nohz_kick_tick(cpu, now);
+        }
+}
+
 #else
 
 static inline void tick_nohz_switch_to_nohz(void) { }
+static inline void tick_check_nohz(int cpu) { }
 
 #endif /* NO_HZ */
 
@@ -620,11 +659,7 @@ static inline void tick_nohz_switch_to_nohz(void) { }
 void tick_check_idle(int cpu)
 {
         tick_check_oneshot_broadcast(cpu);
-#ifdef CONFIG_NO_HZ
-        tick_nohz_stop_idle(cpu);
-        tick_nohz_update_jiffies();
-        tick_nohz_kick_tick(cpu);
-#endif
+        tick_check_nohz(cpu);
 }
 
 /*
diff --git a/kernel/time/timecompare.c b/kernel/time/timecompare.c
index 71e7f1a19156..96ff643a5a59 100644
--- a/kernel/time/timecompare.c
+++ b/kernel/time/timecompare.c
@@ -40,7 +40,7 @@ ktime_t timecompare_transform(struct timecompare *sync,
 
         return ns_to_ktime(nsec);
 }
-EXPORT_SYMBOL(timecompare_transform);
+EXPORT_SYMBOL_GPL(timecompare_transform);
 
 int timecompare_offset(struct timecompare *sync,
                        s64 *offset,
@@ -131,7 +131,7 @@ int timecompare_offset(struct timecompare *sync,
 
         return used;
 }
-EXPORT_SYMBOL(timecompare_offset);
+EXPORT_SYMBOL_GPL(timecompare_offset);
 
 void __timecompare_update(struct timecompare *sync,
                           u64 source_tstamp)
@@ -188,4 +188,4 @@ void __timecompare_update(struct timecompare *sync,
                 }
         }
 }
-EXPORT_SYMBOL(__timecompare_update);
+EXPORT_SYMBOL_GPL(__timecompare_update);
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index c3a4e2907eaa..af4135f05825 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -165,19 +165,12 @@ struct timespec raw_time;
 /* flag for if timekeeping is suspended */
 int __read_mostly timekeeping_suspended;
 
-static struct timespec xtime_cache __attribute__ ((aligned (16)));
-void update_xtime_cache(u64 nsec)
-{
-        xtime_cache = xtime;
-        timespec_add_ns(&xtime_cache, nsec);
-}
-
 /* must hold xtime_lock */
 void timekeeping_leap_insert(int leapsecond)
 {
         xtime.tv_sec += leapsecond;
         wall_to_monotonic.tv_sec -= leapsecond;
-        update_vsyscall(&xtime, timekeeper.clock);
+        update_vsyscall(&xtime, timekeeper.clock, timekeeper.mult);
 }
 
 #ifdef CONFIG_GENERIC_TIME
@@ -332,12 +325,10 @@ int do_settimeofday(struct timespec *tv)
 
         xtime = *tv;
 
-        update_xtime_cache(0);
-
         timekeeper.ntp_error = 0;
         ntp_clear();
 
-        update_vsyscall(&xtime, timekeeper.clock);
+        update_vsyscall(&xtime, timekeeper.clock, timekeeper.mult);
 
         write_sequnlock_irqrestore(&xtime_lock, flags);
 
@@ -488,6 +479,17 @@ int timekeeping_valid_for_hres(void)
 }
 
 /**
+ * timekeeping_max_deferment - Returns max time the clocksource can be deferred
+ *
+ * Caller must observe xtime_lock via read_seqbegin/read_seqretry to
+ * ensure that the clocksource does not change!
+ */
+u64 timekeeping_max_deferment(void)
+{
+        return timekeeper.clock->max_idle_ns;
+}
+
+/**
  * read_persistent_clock -  Return time from the persistent clock.
  *
  * Weak dummy function for arches that do not yet support it.
@@ -548,7 +550,6 @@ void __init timekeeping_init(void)
         }
         set_normalized_timespec(&wall_to_monotonic,
                                 -boot.tv_sec, -boot.tv_nsec);
-        update_xtime_cache(0);
         total_sleep_time.tv_sec = 0;
         total_sleep_time.tv_nsec = 0;
         write_sequnlock_irqrestore(&xtime_lock, flags);
@@ -582,7 +583,6 @@ static int timekeeping_resume(struct sys_device *dev)
                 wall_to_monotonic = timespec_sub(wall_to_monotonic, ts);
                 total_sleep_time = timespec_add_safe(total_sleep_time, ts);
         }
-        update_xtime_cache(0);
         /* re-base the last cycle value */
         timekeeper.clock->cycle_last = timekeeper.clock->read(timekeeper.clock);
         timekeeper.ntp_error = 0;
@@ -723,6 +723,49 @@ static void timekeeping_adjust(s64 offset)
 }
 
 /**
+ * logarithmic_accumulation - shifted accumulation of cycles
+ *
+ * This functions accumulates a shifted interval of cycles into
+ * into a shifted interval nanoseconds. Allows for O(log) accumulation
+ * loop.
+ *
+ * Returns the unconsumed cycles.
+ */
+static cycle_t logarithmic_accumulation(cycle_t offset, int shift)
+{
+        u64 nsecps = (u64)NSEC_PER_SEC << timekeeper.shift;
+
+        /* If the offset is smaller then a shifted interval, do nothing */
+        if (offset < timekeeper.cycle_interval<<shift)
+                return offset;
+
+        /* Accumulate one shifted interval */
+        offset -= timekeeper.cycle_interval << shift;
+        timekeeper.clock->cycle_last += timekeeper.cycle_interval << shift;
+
+        timekeeper.xtime_nsec += timekeeper.xtime_interval << shift;
+        while (timekeeper.xtime_nsec >= nsecps) {
+                timekeeper.xtime_nsec -= nsecps;
+                xtime.tv_sec++;
+                second_overflow();
+        }
+
+        /* Accumulate into raw time */
+        raw_time.tv_nsec += timekeeper.raw_interval << shift;;
+        while (raw_time.tv_nsec >= NSEC_PER_SEC) {
+                raw_time.tv_nsec -= NSEC_PER_SEC;
+                raw_time.tv_sec++;
+        }
+
+        /* Accumulate error between NTP and clock interval */
+        timekeeper.ntp_error += tick_length << shift;
+        timekeeper.ntp_error -= timekeeper.xtime_interval <<
+                                (timekeeper.ntp_error_shift + shift);
+
+        return offset;
+}
+
+/**
  * update_wall_time - Uses the current clocksource to increment the wall time
  *
  * Called from the timer interrupt, must hold a write on xtime_lock.
@@ -731,7 +774,7 @@ void update_wall_time(void)
 {
         struct clocksource *clock;
         cycle_t offset;
-        u64 nsecs;
+        int shift = 0, maxshift;
 
         /* Make sure we're fully resumed: */
         if (unlikely(timekeeping_suspended))
@@ -745,33 +788,22 @@ void update_wall_time(void)
 #endif
         timekeeper.xtime_nsec = (s64)xtime.tv_nsec << timekeeper.shift;
 
-        /* normally this loop will run just once, however in the
-         * case of lost or late ticks, it will accumulate correctly.
+        /*
+         * With NO_HZ we may have to accumulate many cycle_intervals
+         * (think "ticks") worth of time at once. To do this efficiently,
+         * we calculate the largest doubling multiple of cycle_intervals
+         * that is smaller then the offset. We then accumulate that
+         * chunk in one go, and then try to consume the next smaller
+         * doubled multiple.
          */
+        shift = ilog2(offset) - ilog2(timekeeper.cycle_interval);
+        shift = max(0, shift);
+        /* Bound shift to one less then what overflows tick_length */
+        maxshift = (8*sizeof(tick_length) - (ilog2(tick_length)+1)) - 1;
+        shift = min(shift, maxshift);
         while (offset >= timekeeper.cycle_interval) {
-                u64 nsecps = (u64)NSEC_PER_SEC << timekeeper.shift;
-
-                /* accumulate one interval */
-                offset -= timekeeper.cycle_interval;
-                clock->cycle_last += timekeeper.cycle_interval;
-
-                timekeeper.xtime_nsec += timekeeper.xtime_interval;
-                if (timekeeper.xtime_nsec >= nsecps) {
-                        timekeeper.xtime_nsec -= nsecps;
-                        xtime.tv_sec++;
-                        second_overflow();
-                }
-
-                raw_time.tv_nsec += timekeeper.raw_interval;
-                if (raw_time.tv_nsec >= NSEC_PER_SEC) {
-                        raw_time.tv_nsec -= NSEC_PER_SEC;
-                        raw_time.tv_sec++;
-                }
-
-                /* accumulate error between NTP and clock interval */
-                timekeeper.ntp_error += tick_length;
-                timekeeper.ntp_error -= timekeeper.xtime_interval <<
-                                        timekeeper.ntp_error_shift;
+                offset = logarithmic_accumulation(offset, shift);
+                shift--;
         }
 
         /* correct the clock when NTP error is too big */
@@ -807,11 +839,8 @@ void update_wall_time(void)
         timekeeper.ntp_error += timekeeper.xtime_nsec <<
                                 timekeeper.ntp_error_shift;
 
-        nsecs = clocksource_cyc2ns(offset, timekeeper.mult, timekeeper.shift);
-        update_xtime_cache(nsecs);
-
         /* check to see if there is a new clocksource to use */
-        update_vsyscall(&xtime, timekeeper.clock);
+        update_vsyscall(&xtime, timekeeper.clock, timekeeper.mult);
 }
 
 /**
@@ -846,13 +875,13 @@ void monotonic_to_bootbased(struct timespec *ts)
 
 unsigned long get_seconds(void)
 {
-        return xtime_cache.tv_sec;
+        return xtime.tv_sec;
 }
 EXPORT_SYMBOL(get_seconds);
 
 struct timespec __current_kernel_time(void)
 {
-        return xtime_cache;
+        return xtime;
 }
 
 struct timespec current_kernel_time(void)
@@ -862,8 +891,7 @@ struct timespec current_kernel_time(void)
 
         do {
                 seq = read_seqbegin(&xtime_lock);
-
-                now = xtime_cache;
+                now = xtime;
         } while (read_seqretry(&xtime_lock, seq));
 
         return now;
@@ -877,8 +905,7 @@ struct timespec get_monotonic_coarse(void)
 
         do {
                 seq = read_seqbegin(&xtime_lock);
-
-                now = xtime_cache;
+                now = xtime;
                 mono = wall_to_monotonic;
         } while (read_seqretry(&xtime_lock, seq));
 
diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
index 1b5b7aa2fdfd..9d80db4747d4 100644
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -150,6 +150,9 @@ static void print_cpu(struct seq_file *m, int cpu, u64 now)
         P_ns(expires_next);
         P(hres_active);
         P(nr_events);
+        P(nr_retries);
+        P(nr_hangs);
+        P_ns(max_hang_time);
 #endif
 #undef P
 #undef P_ns
@@ -204,10 +207,12 @@ print_tickdevice(struct seq_file *m, struct tick_device *td, int cpu)
                 return;
         }
         SEQ_printf(m, "%s\n", dev->name);
-        SEQ_printf(m, " max_delta_ns:   %lu\n", dev->max_delta_ns);
-        SEQ_printf(m, " min_delta_ns:   %lu\n", dev->min_delta_ns);
-        SEQ_printf(m, " mult:           %lu\n", dev->mult);
-        SEQ_printf(m, " shift:          %d\n", dev->shift);
+        SEQ_printf(m, " max_delta_ns:   %llu\n",
+                   (unsigned long long) dev->max_delta_ns);
+        SEQ_printf(m, " min_delta_ns:   %llu\n",
+                   (unsigned long long) dev->min_delta_ns);
+        SEQ_printf(m, " mult:           %u\n", dev->mult);
+        SEQ_printf(m, " shift:          %u\n", dev->shift);
         SEQ_printf(m, " mode:           %d\n", dev->mode);
         SEQ_printf(m, " next_event:     %Ld nsecs\n",
                    (unsigned long long) ktime_to_ns(dev->next_event));
@@ -252,7 +257,7 @@ static int timer_list_show(struct seq_file *m, void *v)
         u64 now = ktime_to_ns(ktime_get());
         int cpu;
 
-        SEQ_printf(m, "Timer List Version: v0.4\n");
+        SEQ_printf(m, "Timer List Version: v0.5\n");
         SEQ_printf(m, "HRTIMER_MAX_CLOCK_BASES: %d\n", HRTIMER_MAX_CLOCK_BASES);
         SEQ_printf(m, "now at %Ld nsecs\n", (unsigned long long)now);