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Subject[PATCH] ftrace: add tracepoint for xtime
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

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
include/trace/events/xtime.h | 38 ++++++++++++++++++++++++++++++++++++++
kernel/time/ntp.c | 2 ++
kernel/time/timekeeping.c | 5 +++++
3 files changed, 45 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..f07bb64
--- /dev/null
+++ b/include/trace/events/xtime.h
@@ -0,0 +1,38 @@
+#if !defined(_TRACE_XTIME_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_XTIME_H
+
+#include <linux/time.h>
+#include <linux/tracepoint.h>
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM xtime
+
+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 7fc6437..33db762 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -14,6 +14,7 @@
#include <linux/timex.h>
#include <linux/time.h>
#include <linux/mm.h>
+#include <trace/events/xtime.h>

/*
* NTP timekeeping variables:
@@ -220,6 +221,7 @@ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
break;
}
update_vsyscall(&xtime, clock);
+ trace_gtod_update_xtime(&xtime, &wall_to_monotonic);

write_sequnlock(&xtime_lock);

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index e8c77d9..798f93e 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -19,6 +19,9 @@
#include <linux/time.h>
#include <linux/tick.h>

+#define CREATE_TRACE_POINTS
+#include <trace/events/xtime.h>
+

/*
* This read-write spinlock protects us from races in SMP while
@@ -171,6 +174,7 @@ int do_settimeofday(struct timespec *tv)
ntp_clear();

update_vsyscall(&xtime, clock);
+ trace_gtod_update_xtime(&xtime, &wall_to_monotonic);

write_sequnlock_irqrestore(&xtime_lock, flags);

@@ -568,6 +572,7 @@ void update_wall_time(void)
/* check to see if there is a new clocksource to use */
change_clocksource();
update_vsyscall(&xtime, clock);
+ trace_gtod_update_xtime(&xtime, &wall_to_monotonic);
}

/**
--
1.6.1.2


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