1 files changed, 97 insertions, 0 deletions
diff --git a/kernel/trace/trace-clock.c b/kernel/trace/trace-clock.c
new file mode 100644
index 00000000000..3ed1667aacb
--- /dev/null
+++ b/kernel/trace/trace-clock.c
@@ -0,0 +1,97 @@
+/*
+ * kernel/trace/trace-clock.c
+ *
+ * (C) Copyright	2008 -
+ * 		Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca)
+ *
+ * Generic kernel tracing clock for architectures without TSC.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/timer.h>
+#include <linux/workqueue.h>
+#include <linux/cpu.h>
+#include <linux/timex.h>
+#include <linux/bitops.h>
+#include <linux/trace-clock.h>
+#include <linux/jiffies.h>
+
+static int trace_clock_refcount;
+static DEFINE_MUTEX(trace_clock_mutex);
+static struct timer_list trace_clock_timer;
+/*
+ * bits 0..12 : counter, atomically incremented
+ * bits 13..{32,64} : time counter, incremented each jiffy.
+ */
+atomic_long_t trace_clock_var;
+EXPORT_SYMBOL(trace_clock_var);
+
+static void trace_clock_update(void)
+{
+	long old_clock, new_clock;
+	unsigned long ticks;
+
+	/*
+	 * Make sure we keep track of delayed timer.
+	 */
+	ticks = jiffies - trace_clock_timer.expires + 1;
+	/* Don't update if ticks is zero, time would go backward. */
+	if (unlikely(!ticks))
+		return;
+	do {
+		old_clock = atomic_long_read(&trace_clock_var);
+		new_clock = (old_clock + (ticks << TRACE_CLOCK_SHIFT))
+			& (~((1 << TRACE_CLOCK_SHIFT) - 1));
+	} while (atomic_long_cmpxchg(&trace_clock_var, old_clock, new_clock)
+			!= old_clock);
+}
+
+static void trace_clock_timer_fct(unsigned long data)
+{
+	trace_clock_update();
+	trace_clock_timer.expires = jiffies + 1;
+	add_timer(&trace_clock_timer);
+}
+
+static void enable_trace_clock(void)
+{
+	init_timer(&trace_clock_timer);
+	/* trace_clock_update() reads expires */
+	trace_clock_timer.function = trace_clock_timer_fct;
+	trace_clock_timer.expires = jiffies + 1;
+	trace_clock_update();
+	add_timer(&trace_clock_timer);
+}
+
+static void disable_trace_clock(void)
+{
+	del_timer_sync(&trace_clock_timer);
+}
+
+void get_trace_clock(void)
+{
+	get_synthetic_tsc();
+	mutex_lock(&trace_clock_mutex);
+	if (trace_clock_refcount++)
+		goto end;
+	enable_trace_clock();
+end:
+	mutex_unlock(&trace_clock_mutex);
+}
+EXPORT_SYMBOL_GPL(get_trace_clock);
+
+void put_trace_clock(void)
+{
+	mutex_lock(&trace_clock_mutex);
+	WARN_ON(trace_clock_refcount <= 0);
+	if (trace_clock_refcount != 1)
+		goto end;
+	disable_trace_clock();
+end:
+	trace_clock_refcount--;
+	mutex_unlock(&trace_clock_mutex);
+	put_synthetic_tsc();
+}
+EXPORT_SYMBOL_GPL(put_trace_clock);