sched_clock: stop maximum check on NO HZ

[linux-2.6-omap-h63xx.git] / kernel / sched_clock.c

diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c
index 42b81fa38cbd254987dbedef0f0bd047766d36e3..97159e225a7755f2b1b6f7bef1b7ebb71ca72551 100644 (file)
--- a/kernel/sched_clock.c
+++ b/kernel/sched_clock.c
@@ -45,6 +45,9 @@ struct sched_clock_data {
        u64                     tick_raw;
        u64                     tick_gtod;
        u64                     clock;
+#ifdef CONFIG_NO_HZ
+       int                     check_max;
+#endif
 };
 
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct sched_clock_data, sched_clock_data);
@@ -76,11 +79,45 @@ void sched_clock_init(void)
                scd->tick_raw = 0;
                scd->tick_gtod = ktime_now;
                scd->clock = ktime_now;
+#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
  *
@@ -112,7 +149,7 @@ static void __update_sched_clock(struct sched_clock_data *scd, u64 now)
         */
        max_clock = scd->tick_gtod + (2 + delta_jiffies) * TICK_NSEC;
 
-       if (unlikely(clock + delta > max_clock)) {
+       if (unlikely(clock + delta > max_clock) && check_max(scd)) {
                if (clock < max_clock)
                        clock = max_clock;
                else