[PATCH 2/3] ftrace: add tracepoint for xtime

[Zhaolei <zhaolei@cn.fujitsu.com>]

From: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>

This patch can trace current xtime and wall_to_monotonic. Then user can
use ctime() to convert them to wall time which is easier to be understood,
especially for flight-recorder which need to get trace event from a kernel
dump file.

Example of ftrace output:
          <idle>-0     [000] 20118.489849: gtod_update_xtime: xtime=1243265589.999999824 wall_to_monotonic=3051713268.744158739
           <...>-4020  [001] 20118.489855: sys_open(filename: bf9e66e0, flags: 98800, mode: bf9e66e0)
           <...>-4020  [001] 20118.489873: sys_open -> 0xffffffec

ctime(1243265590) = date:Mon May 25 11:33:10 2009
So we can realize the task with pid 4020 open a file at
Mon May 25 11:33:10 2009

Changelog:
v1->v2: Rebased by Zhao Lei <zhaolei@cn.fujitsu.com>

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 include/trace/events/xtime.h |   38 ++++++++++++++++++++++++++++++++++++++
 kernel/time/ntp.c            |    4 ++++
 kernel/time/timekeeping.c    |    6 ++++++
 3 files changed, 48 insertions(+), 0 deletions(-)
 create mode 100644 include/trace/events/xtime.h

diff --git a/include/trace/events/xtime.h b/include/trace/events/xtime.h
new file mode 100644
index 0000000..398e679
--- /dev/null
+++ b/include/trace/events/xtime.h
@@ -0,0 +1,38 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM xtime
+
+#if !defined(_TRACE_XTIME_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_XTIME_H
+
+#include <linux/time.h>
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(gtod_update_xtime,
+
+	TP_PROTO(struct timespec *xtime, struct timespec *wall_to_monotonic),
+
+	TP_ARGS(xtime, wall_to_monotonic),
+
+	TP_STRUCT__entry(
+		__field(	long,	xtime_sec		)
+		__field(	long,	xtime_nsec		)
+		__field(	long,	wall_to_monotonic_sec	)
+		__field(	long,	wall_to_monotonic_nsec	)
+	),
+
+	TP_fast_assign(
+		__entry->xtime_sec		= xtime->tv_sec;
+		__entry->xtime_nsec		= xtime->tv_nsec;
+		__entry->wall_to_monotonic_sec	= wall_to_monotonic->tv_sec;
+		__entry->wall_to_monotonic_nsec	= wall_to_monotonic->tv_nsec;
+	),
+
+	TP_printk("xtime=%ld.%09ld wall_to_monotonic=%ld.%09ld",
+		  __entry->xtime_sec, __entry->xtime_nsec,
+		  __entry->wall_to_monotonic_sec, __entry->wall_to_monotonic_nsec)
+);
+
+#endif /* _TRACE_XTIME_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 4800f93..fc2f13a 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -15,6 +15,8 @@
 #include <linux/time.h>
 #include <linux/mm.h>
 
+#include <trace/events/xtime.h>
+
 /*
  * NTP timekeeping variables:
  */
@@ -218,6 +220,8 @@ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
 		break;
 	}
 
+	trace_gtod_update_xtime(&xtime, &wall_to_monotonic);
+
 	write_sequnlock(&xtime_lock);
 
 	return res;
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 03cbeb3..2e57a87 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -20,6 +20,9 @@
 #include <linux/tick.h>
 #include <linux/stop_machine.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/xtime.h>
+
 /* Structure holding internal timekeeping values. */
 struct timekeeper {
 	/* Current clocksource used for timekeeping. */
@@ -338,6 +341,8 @@ int do_settimeofday(struct timespec *tv)
 
 	update_vsyscall(&xtime, timekeeper.clock);
 
+	trace_gtod_update_xtime(&xtime, &wall_to_monotonic);
+
 	write_sequnlock_irqrestore(&xtime_lock, flags);
 
 	/* signal hrtimers about time change */
@@ -811,6 +816,7 @@ void update_wall_time(void)
 
 	/* check to see if there is a new clocksource to use */
 	update_vsyscall(&xtime, timekeeper.clock);
+	trace_gtod_update_xtime(&xtime, &wall_to_monotonic);
 }
 
 /**
-- 
1.5.5.3