3 files changed, 14 insertions, 114 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5270d449ff9d..ea436bc1a0e2 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1572,28 +1572,13 @@ static inline void sched_clock_idle_sleep_event(void)
 static inline void sched_clock_idle_wakeup_event(u64 delta_ns)
 {
 }
-
-#ifdef CONFIG_NO_HZ
-static inline void sched_clock_tick_stop(int cpu)
-{
-}
-
-static inline void sched_clock_tick_start(int cpu)
-{
-}
-#endif
-
-#else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */
+#else
 extern void sched_clock_init(void);
 extern u64 sched_clock_cpu(int cpu);
 extern void sched_clock_tick(void);
 extern void sched_clock_idle_sleep_event(void);
 extern void sched_clock_idle_wakeup_event(u64 delta_ns);
-#ifdef CONFIG_NO_HZ
-extern void sched_clock_tick_stop(int cpu);
-extern void sched_clock_tick_start(int cpu);
 #endif
-#endif /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */
 
 /*
  * For kernel-internal use: high-speed (but slightly incorrect) per-cpu
diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c
index 5a2dc7d8fd98..9a7844158ae8 100644
--- a/kernel/sched_clock.c
+++ b/kernel/sched_clock.c
@@ -44,11 +44,6 @@ unsigned long long __attribute__((weak)) sched_clock(void)
 
 #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
 
-#define MULTI_SHIFT 15
-/* Max is double, Min is 1/2 */
-#define MAX_MULTI (2LL << MULTI_SHIFT)
-#define MIN_MULTI (1LL << (MULTI_SHIFT-1))
-
 struct sched_clock_data {
         /*
          * Raw spinlock - this is a special case: this might be called
@@ -62,10 +57,6 @@ struct sched_clock_data {
         u64                     tick_raw;
         u64                     tick_gtod;
         u64                     clock;
-        s64                     multi;
-#ifdef CONFIG_NO_HZ
-        int                     check_max;
-#endif
 };
 
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct sched_clock_data, sched_clock_data);
@@ -97,53 +88,18 @@ void sched_clock_init(void)
                 scd->tick_raw = 0;
                 scd->tick_gtod = ktime_now;
                 scd->clock = ktime_now;
-                scd->multi = 1 << MULTI_SHIFT;
-#ifdef CONFIG_NO_HZ
-                scd->check_max = 1;
-#endif
         }
 
         sched_clock_running = 1;
 }
 
-#ifdef CONFIG_NO_HZ
-/*
- * The dynamic ticks makes the delta jiffies inaccurate. This
- * prevents us from checking the maximum time update.
- * Disable the maximum check during stopped ticks.
- */
-void sched_clock_tick_stop(int cpu)
-{
-        struct sched_clock_data *scd = cpu_sdc(cpu);
-
-        scd->check_max = 0;
-}
-
-void sched_clock_tick_start(int cpu)
-{
-        struct sched_clock_data *scd = cpu_sdc(cpu);
-
-        scd->check_max = 1;
-}
-
-static int check_max(struct sched_clock_data *scd)
-{
-        return scd->check_max;
-}
-#else
-static int check_max(struct sched_clock_data *scd)
-{
-        return 1;
-}
-#endif /* CONFIG_NO_HZ */
-
 /*
  * update the percpu scd from the raw @now value
  *
  *  - filter out backward motion
  *  - use jiffies to generate a min,max window to clip the raw values
  */
-static void __update_sched_clock(struct sched_clock_data *scd, u64 now, u64 *time)
+static void __update_sched_clock(struct sched_clock_data *scd, u64 now)
 {
         unsigned long now_jiffies = jiffies;
         long delta_jiffies = now_jiffies - scd->tick_jiffies;
@@ -152,31 +108,16 @@ static void __update_sched_clock(struct sched_clock_data *scd, u64 now, u64 *tim
         s64 delta = now - scd->prev_raw;
 
         WARN_ON_ONCE(!irqs_disabled());
-
-        /*
-         * At schedule tick the clock can be just under the gtod. We don't
-         * want to push it too prematurely.
-         */
-        min_clock = scd->tick_gtod + (delta_jiffies * TICK_NSEC);
-        if (min_clock > TICK_NSEC)
-                min_clock -= TICK_NSEC / 2;
+        min_clock = scd->tick_gtod + delta_jiffies * TICK_NSEC;
 
         if (unlikely(delta < 0)) {
                 clock++;
                 goto out;
         }
 
-        /*
-         * The clock must stay within a jiffie of the gtod.
-         * But since we may be at the start of a jiffy or the end of one
-         * we add another jiffy buffer.
-         */
-        max_clock = scd->tick_gtod + (2 + delta_jiffies) * TICK_NSEC;
-
-        delta *= scd->multi;
-        delta >>= MULTI_SHIFT;
+        max_clock = min_clock + TICK_NSEC;
 
-        if (unlikely(clock + delta > max_clock) && check_max(scd)) {
+        if (unlikely(clock + delta > max_clock)) {
                 if (clock < max_clock)
                         clock = max_clock;
                 else
@@ -189,12 +130,9 @@ static void __update_sched_clock(struct sched_clock_data *scd, u64 now, u64 *tim
         if (unlikely(clock < min_clock))
                 clock = min_clock;
 
-        if (time)
-                *time = clock;
-        else {
-                scd->prev_raw = now;
-                scd->clock = clock;
-        }
+        scd->prev_raw = now;
+        scd->tick_jiffies = now_jiffies;
+        scd->clock = clock;
 }
 
 static void lock_double_clock(struct sched_clock_data *data1,
@@ -238,26 +176,21 @@ u64 sched_clock_cpu(int cpu)
                 now -= scd->tick_gtod;
 
                 __raw_spin_unlock(&my_scd->lock);
-
-                __update_sched_clock(scd, now, &clock);
-
-                __raw_spin_unlock(&scd->lock);
-
         } else {
                 __raw_spin_lock(&scd->lock);
-                __update_sched_clock(scd, now, NULL);
-                clock = scd->clock;
-                __raw_spin_unlock(&scd->lock);
         }
 
+        __update_sched_clock(scd, now);
+        clock = scd->clock;
+
+        __raw_spin_unlock(&scd->lock);
+
         return clock;
 }
 
 void sched_clock_tick(void)
 {
         struct sched_clock_data *scd = this_scd();
-        unsigned long now_jiffies = jiffies;
-        s64 mult, delta_gtod, delta_raw;
         u64 now, now_gtod;
 
         if (unlikely(!sched_clock_running))
@@ -269,29 +202,14 @@ void sched_clock_tick(void)
         now = sched_clock();
 
         __raw_spin_lock(&scd->lock);
-        __update_sched_clock(scd, now, NULL);
+        __update_sched_clock(scd, now);
         /*
          * update tick_gtod after __update_sched_clock() because that will
          * already observe 1 new jiffy; adding a new tick_gtod to that would
          * increase the clock 2 jiffies.
          */
-        delta_gtod = now_gtod - scd->tick_gtod;
-        delta_raw = now - scd->tick_raw;
-
-        if ((long)delta_raw > 0) {
-                mult = delta_gtod << MULTI_SHIFT;
-                do_div(mult, delta_raw);
-                scd->multi = mult;
-                if (scd->multi > MAX_MULTI)
-                        scd->multi = MAX_MULTI;
-                else if (scd->multi < MIN_MULTI)
-                        scd->multi = MIN_MULTI;
-        } else
-                scd->multi = 1 << MULTI_SHIFT;
-
         scd->tick_raw = now;
         scd->tick_gtod = now_gtod;
-        scd->tick_jiffies = now_jiffies;
         __raw_spin_unlock(&scd->lock);
 }
 
@@ -321,7 +239,6 @@ void sched_clock_idle_wakeup_event(u64 delta_ns)
         __raw_spin_lock(&scd->lock);
         scd->prev_raw = now;
         scd->clock += delta_ns;
-        scd->multi = 1 << MULTI_SHIFT;
         __raw_spin_unlock(&scd->lock);
 
         touch_softlockup_watchdog();
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 825b4c00fe44..f5da526424a9 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -289,7 +289,6 @@ void tick_nohz_stop_sched_tick(int inidle)
                         ts->tick_stopped = 1;
                         ts->idle_jiffies = last_jiffies;
                         rcu_enter_nohz();
-                        sched_clock_tick_stop(cpu);
                 }
 
                 /*
@@ -392,7 +391,6 @@ void tick_nohz_restart_sched_tick(void)
         select_nohz_load_balancer(0);
         now = ktime_get();
         tick_do_update_jiffies64(now);
-        sched_clock_tick_start(cpu);
         cpu_clear(cpu, nohz_cpu_mask);
 
         /*