From f6c19f6e88428f2885ee53b892cad3f237993fba Mon Sep 17 00:00:00 2001
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Tue, 10 May 2011 23:16:21 -0400
Subject: [PATCH] Add fallback wrapper for kernels without
 CONFIG_HAVE_TRACE_CLOCK

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 ltt-ring-buffer-client.h |  2 +-
 ltt-tracer.h             |  2 +-
 trace-clock.h            | 75 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 77 insertions(+), 2 deletions(-)
 create mode 100644 trace-clock.h

diff --git a/ltt-ring-buffer-client.h b/ltt-ring-buffer-client.h
index c2e53f35..248cee0e 100644
--- a/ltt-ring-buffer-client.h
+++ b/ltt-ring-buffer-client.h
@@ -10,7 +10,7 @@
 
 #include <linux/module.h>
 #include <linux/types.h>
-#include <linux/trace-clock.h>
+#include "trace-clock.h"
 #include "ltt-events.h"
 #include "ltt-tracer.h"
 
diff --git a/ltt-tracer.h b/ltt-tracer.h
index 2f947b7e..ef5e815b 100644
--- a/ltt-tracer.h
+++ b/ltt-tracer.h
@@ -16,10 +16,10 @@
 #include <linux/cache.h>
 #include <linux/timex.h>
 #include <linux/wait.h>
-#include <linux/trace-clock.h>
 #include <asm/atomic.h>
 #include <asm/local.h>
 
+#include "trace-clock.h"
 #include "ltt-tracer-core.h"
 #include "ltt-events.h"
 
diff --git a/trace-clock.h b/trace-clock.h
new file mode 100644
index 00000000..ca09704d
--- /dev/null
+++ b/trace-clock.h
@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2011 Mathieu Desnoyers (mathieu.desnoyers@efficios.com)
+ *
+ * Contains LTTng trace clock mapping to LTTng trace clock or mainline monotonic
+ * clock. This wrapper depends on CONFIG_HIGH_RES_TIMERS=y.
+ *
+ * Dual LGPL v2.1/GPL v2 license.
+ */
+
+#ifndef _LTT_TRACE_CLOCK_H
+#define _LTT_TRACE_CLOCK_H
+
+#ifdef CONFIG_HAVE_TRACE_CLOCK
+#include <linux/trace-clock.h>
+#else /* CONFIG_HAVE_TRACE_CLOCK */
+
+#include <linux/hardirq.h>
+#include <linux/ktime.h>
+#include <linux/time.h>
+#include <linux/hrtimer.h>
+
+static inline u64 trace_clock_monotonic_wrapper(void)
+{
+	ktime_t ktime;
+
+	/*
+	 * Refuse to trace from NMIs with this wrapper, because an NMI could
+	 * nest over the xtime write seqlock and deadlock.
+	 */
+	if (in_nmi())
+		return 0;
+
+	ktime = ktime_get();
+	return (u64) ktime.tv64;
+}
+
+static inline u32 trace_clock_read32(void)
+{
+	return (u32) trace_clock_monotonic_wrapper();
+}
+
+static inline u64 trace_clock_read64(void)
+{
+	return (u64) trace_clock_monotonic_wrapper();
+}
+
+static inline u64 trace_clock_frequency(void)
+{
+	return (u64)NSEC_PER_SEC;
+}
+
+static inline u32 trace_clock_freq_scale(void)
+{
+	return 1;
+}
+
+static inline int get_trace_clock(void)
+{
+	printk(KERN_WARNING "LTTng: Using mainline kernel monotonic clock.\n");
+	printk(KERN_WARNING "  * NMIs will not be traced,\n");
+	printk(KERN_WARNING "  * expect significant performance degradation compared to the\n");
+	printk(KERN_WARNING "    LTTng trace clocks.\n");
+	printk(KERN_WARNING "You should consider deploying a kernel with the the LTTng kernel\n");
+	printk(KERN_WARNING "patches, or, better, ask the Linux tracing maintainers to integrate\n");
+	printk(KERN_WARNING "them if you care deeply about this.\n");
+	return 0;
+}
+
+static inline void put_trace_clock(void)
+{
+}
+
+#endif /* CONFIG_HAVE_TRACE_CLOCK */
+
+#endif /* _LTT_TRACE_CLOCK_H */
-- 
2.34.1