1 files changed, 266 insertions, 0 deletions
diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c
new file mode 100644
index 0000000..a0b0852
--- /dev/null
+++ b/kernel/sched_clock.c
@@ -0,0 +1,266 @@
+/*
+ * sched_clock for unstable cpu clocks
+ *
+ *  Copyright (C) 2008 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
+ *
+ *  Updates and enhancements:
+ *    Copyright (C) 2008 Red Hat, Inc. Steven Rostedt <srostedt@redhat.com>
+ *
+ * Based on code by:
+ *   Ingo Molnar <mingo@redhat.com>
+ *   Guillaume Chazarain <guichaz@gmail.com>
+ *
+ * Create a semi stable clock from a mixture of other events, including:
+ *  - gtod
+ *  - sched_clock()
+ *  - explicit idle events
+ *
+ * We use gtod as base and the unstable clock deltas. The deltas are filtered,
+ * making it monotonic and keeping it within an expected window.
+ *
+ * Furthermore, explicit sleep and wakeup hooks allow us to account for time
+ * that is otherwise invisible (TSC gets stopped).
+ *
+ * The clock: sched_clock_cpu() is monotonic per cpu, and should be somewhat
+ * consistent between cpus (never more than 2 jiffies difference).
+ */
+#include <linux/sched.h>
+#include <linux/percpu.h>
+#include <linux/spinlock.h>
+#include <linux/ktime.h>
+#include <linux/module.h>
+
+/*
+ * Scheduler clock - returns current time in nanosec units.
+ * This is default implementation.
+ * Architectures and sub-architectures can override this.
+ */
+unsigned long long __attribute__((weak)) sched_clock(void)
+{
+	return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ);
+}
+
+static __read_mostly int sched_clock_running;
+
+#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
+
+struct sched_clock_data {
+	/*
+	 * Raw spinlock - this is a special case: this might be called
+	 * from within instrumentation code so we dont want to do any
+	 * instrumentation ourselves.
+	 */
+	raw_spinlock_t		lock;
+
+	u64			tick_raw;
+	u64			tick_gtod;
+	u64			clock;
+};
+
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct sched_clock_data, sched_clock_data);
+
+static inline struct sched_clock_data *this_scd(void)
+{
+	return &__get_cpu_var(sched_clock_data);
+}
+
+static inline struct sched_clock_data *cpu_sdc(int cpu)
+{
+	return &per_cpu(sched_clock_data, cpu);
+}
+
+void sched_clock_init(void)
+{
+	u64 ktime_now = ktime_to_ns(ktime_get());
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		struct sched_clock_data *scd = cpu_sdc(cpu);
+
+		scd->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
+		scd->tick_raw = 0;
+		scd->tick_gtod = ktime_now;
+		scd->clock = ktime_now;
+	}
+
+	sched_clock_running = 1;
+}
+
+/*
+ * min,max except they take wrapping into account
+ */
+
+static inline u64 wrap_min(u64 x, u64 y)
+{
+	return (s64)(x - y) < 0 ? x : y;
+}
+
+static inline u64 wrap_max(u64 x, u64 y)
+{
+	return (s64)(x - y) > 0 ? x : y;
+}
+
+/*
+ * update the percpu scd from the raw @now value
+ *
+ *  - filter out backward motion
+ *  - use the GTOD tick value to create a window to filter crazy TSC values
+ */
+static u64 __update_sched_clock(struct sched_clock_data *scd, u64 now)
+{
+	s64 delta = now - scd->tick_raw;
+	u64 clock, min_clock, max_clock;
+
+	WARN_ON_ONCE(!irqs_disabled());
+
+	if (unlikely(delta < 0))
+		delta = 0;
+
+	/*
+	 * scd->clock = clamp(scd->tick_gtod + delta,
+	 * 		      max(scd->tick_gtod, scd->clock),
+	 * 		      scd->tick_gtod + TICK_NSEC);
+	 */
+
+	clock = scd->tick_gtod + delta;
+	min_clock = wrap_max(scd->tick_gtod, scd->clock);
+	max_clock = wrap_max(scd->clock, scd->tick_gtod + TICK_NSEC);
+
+	clock = wrap_max(clock, min_clock);
+	clock = wrap_min(clock, max_clock);
+
+	scd->clock = clock;
+
+	return scd->clock;
+}
+
+static void lock_double_clock(struct sched_clock_data *data1,
+				struct sched_clock_data *data2)
+{
+	if (data1 < data2) {
+		__raw_spin_lock(&data1->lock);
+		__raw_spin_lock(&data2->lock);
+	} else {
+		__raw_spin_lock(&data2->lock);
+		__raw_spin_lock(&data1->lock);
+	}
+}
+
+u64 sched_clock_cpu(int cpu)
+{
+	struct sched_clock_data *scd = cpu_sdc(cpu);
+	u64 now, clock, this_clock, remote_clock;
+
+	if (unlikely(!sched_clock_running))
+		return 0ull;
+
+	WARN_ON_ONCE(!irqs_disabled());
+	now = sched_clock();
+
+	if (cpu != raw_smp_processor_id()) {
+		struct sched_clock_data *my_scd = this_scd();
+
+		lock_double_clock(scd, my_scd);
+
+		this_clock = __update_sched_clock(my_scd, now);
+		remote_clock = scd->clock;
+
+		/*
+		 * Use the opportunity that we have both locks
+		 * taken to couple the two clocks: we take the
+		 * larger time as the latest time for both
+		 * runqueues. (this creates monotonic movement)
+		 */
+		if (likely((s64)(remote_clock - this_clock) < 0)) {
+			clock = this_clock;
+			scd->clock = clock;
+		} else {
+			/*
+			 * Should be rare, but possible:
+			 */
+			clock = remote_clock;
+			my_scd->clock = remote_clock;
+		}
+
+		__raw_spin_unlock(&my_scd->lock);
+	} else {
+		__raw_spin_lock(&scd->lock);
+		clock = __update_sched_clock(scd, now);
+	}
+
+	__raw_spin_unlock(&scd->lock);
+
+	return clock;
+}
+
+void sched_clock_tick(void)
+{
+	struct sched_clock_data *scd = this_scd();
+	u64 now, now_gtod;
+
+	if (unlikely(!sched_clock_running))
+		return;
+
+	WARN_ON_ONCE(!irqs_disabled());
+
+	now_gtod = ktime_to_ns(ktime_get());
+	now = sched_clock();
+
+	__raw_spin_lock(&scd->lock);
+	scd->tick_raw = now;
+	scd->tick_gtod = now_gtod;
+	__update_sched_clock(scd, now);
+	__raw_spin_unlock(&scd->lock);
+}
+
+/*
+ * We are going deep-idle (irqs are disabled):
+ */
+void sched_clock_idle_sleep_event(void)
+{
+	sched_clock_cpu(smp_processor_id());
+}
+EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event);
+
+/*
+ * We just idled delta nanoseconds (called with irqs disabled):
+ */
+void sched_clock_idle_wakeup_event(u64 delta_ns)
+{
+	if (timekeeping_suspended)
+		return;
+
+	sched_clock_tick();
+	touch_softlockup_watchdog();
+}
+EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
+
+#else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */
+
+void sched_clock_init(void)
+{
+	sched_clock_running = 1;
+}
+
+u64 sched_clock_cpu(int cpu)
+{
+	if (unlikely(!sched_clock_running))
+		return 0;
+
+	return sched_clock();
+}
+
+#endif
+
+unsigned long long cpu_clock(int cpu)
+{
+	unsigned long long clock;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	clock = sched_clock_cpu(cpu);
+	local_irq_restore(flags);
+
+	return clock;
+}
+EXPORT_SYMBOL_GPL(cpu_clock);