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authorHeena Sirwani <heenasirwani@gmail.com>2014-10-29 16:01:16 +0530
committerThomas Gleixner <tglx@linutronix.de>2014-10-29 15:15:40 +0100
commit9e3680b1750b9a62680b0262c9f438de98b77655 (patch)
tree771803b021b50766f7fadb318db8230b514ac128 /include/linux/timekeeping.h
parentcac7f2429872d3733dc3f9915857b1691da2eb2f (diff)
downloadlinux-linaro-stable-9e3680b1750b9a62680b0262c9f438de98b77655.tar.gz
timekeeping: Provide fast accessor to the seconds part of CLOCK_MONOTONIC
This is the counterpart to get_seconds() based on CLOCK_MONOTONIC. The use case for this interface are kernel internal coarse grained timestamps which do neither require the nanoseconds fraction of current time nor the CLOCK_REALTIME properties. Such timestamps can currently only retrieved by calling ktime_get_ts64() and using the tv_sec field of the returned timespec64. That's inefficient as it involves the read of the clocksource, math operations and must be protected by the timekeeper sequence counter. To avoid the sequence counter protection we restrict the return value to unsigned 32bit on 32bit machines. This covers ~136 years of uptime and therefor an overflow is not expected to hit anytime soon. To avoid math in the function we calculate the current seconds portion of CLOCK_MONOTONIC when the timekeeper gets updated in tk_update_ktime_data() similar to the CLOCK_REALTIME counterpart xtime_sec. [ tglx: Massaged changelog, simplified and commented the update function, added docbook comment ] Signed-off-by: Heena Sirwani <heenasirwani@gmail.com> Reviewed-by: Arnd Bergman <arnd@arndb.de> Cc: John Stultz <john.stultz@linaro.org> Cc: opw-kernel@googlegroups.com Link: http://lkml.kernel.org/r/da0b63f4bdf3478909f92becb35861197da3a905.1414578445.git.heenasirwani@gmail.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'include/linux/timekeeping.h')
-rw-r--r--include/linux/timekeeping.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 1caa6b04fdc5..115d55e11bc9 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -28,6 +28,7 @@ struct timespec __current_kernel_time(void);
struct timespec get_monotonic_coarse(void);
extern void getrawmonotonic(struct timespec *ts);
extern void ktime_get_ts64(struct timespec64 *ts);
+extern time64_t ktime_get_seconds(void);
extern int __getnstimeofday64(struct timespec64 *tv);
extern void getnstimeofday64(struct timespec64 *tv);