[RFC 1/8] Implement getnsboottime kernel API

Glauber Costa
2010-08-30T16:23:43Z

From: Zachary Amsden <zamsden@redhat.com>

Add a kernel call to get the number of nanoseconds since boot. This
is generally useful enough to make it a generic call.

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
---
include/linux/time.h | 1 +
kernel/time/timekeeping.c | 27 +++++++++++++++++++++++++++
2 files changed, 28 insertions(+), 0 deletions(-)

diff --git a/include/linux/time.h b/include/linux/time.h
index ea3559f..5d04108 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -145,6 +145,7 @@ extern void getnstimeofday(struct timespec *tv);
extern void getrawmonotonic(struct timespec *ts);
extern void getboottime(struct timespec *ts);
extern void monotonic_to_bootbased(struct timespec *ts);
+extern s64 getnsboottime(void);

extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
extern int timekeeping_valid_for_hres(void);
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index caf8d4d..d250f0a 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -285,6 +285,33 @@ void ktime_get_ts(struct timespec *ts)
}
EXPORT_SYMBOL_GPL(ktime_get_ts);

+
+/**
+ * getnsboottime - get the bootbased clock in nsec format
+ *
+ * The function calculates the bootbased clock from the realtime
+ * clock and the wall_to_monotonic offset and stores the result
+ * in normalized timespec format in the variable pointed to by @ts.
+ */
+s64 getnsboottime(void)
+{
+ unsigned int seq;
+ s64 secs, nsecs;
+
+ WARN_ON(timekeeping_suspended);
+
+ do {
+ seq = read_seqbegin(&xtime_lock);
+ secs = xtime.tv_sec + wall_to_monotonic.tv_sec;
+ secs += total_sleep_time.tv_sec;
+ nsecs = xtime.tv_nsec + wall_to_monotonic.tv_nsec;
+ nsecs += total_sleep_time.tv_nsec + timekeeping_get_ns();
+
+ } while (read_seqretry(&xtime_lock, seq));
+ return nsecs + (secs * NSEC_PER_SEC);
+}
+EXPORT_SYMBOL_GPL(getnsboottime);
+
/**
* do_gettimeofday - Returns the time of day in a timeval
* @tv: pointer to the timeval to be set
--
1.6.2.2