sched clock: revert various sched_clock() changes

[linux-beck.git] / kernel / sched_clock.c

diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c
index 5a2dc7d8fd984c01aeea5a163ec307a94593f82c..9a7844158ae8b3b74b3e544405392aeea91b1063 100644 (file)
--- 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();