Messages in this thread Patch in this message | | | Date | Wed, 29 Oct 2014 14:43:17 +0530 | From | Heena Sirwani <> | Subject | [PATCH v7] timekeeping: Added a function to return tv_sec portion of ktime_get_ts64() |
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The following patch replaces all instances of time_t with time64_t i.e. change the type used for representing time from 32-bit to 64-bit. All 32-bit kernels to date use a signed 32-bit time_t type, which can only represent time until January 2038. Since embedded systems running 32-bit Linux are going to survive beyond that date, we have to change all current uses, in a backwards compatible way.
The patch also changes the function get_seconds() that returns a 32-bit integer to ktime_get_seconds() that returns seconds as 64-bit integer.
The patch changes the type of ticks from time_t to u32. We keep ticks as 32-bits as the function uses 32-bit arithmetic which would prove less expensive than 64-bit arithmetic and the function is expected to be called atleast once every 32 seconds.
Signed-off-by: Heena Sirwani <heenasirwani@gmail.com> --- Changes in v7: - Reordered assignments in tk_update_ktime_data() to improve readability.
include/linux/timekeeper_internal.h | 2 ++ include/linux/timekeeping.h | 1 + kernel/time/timekeeping.c | 31 ++++++++++++++++++++++++++++--- 3 files changed, 31 insertions(+), 3 deletions(-)
diff --git a/include/linux/timekeeper_internal.h b/include/linux/timekeeper_internal.h index 95640dc..92e5e9d 100644 --- a/include/linux/timekeeper_internal.h +++ b/include/linux/timekeeper_internal.h @@ -42,6 +42,7 @@ struct tk_read_base { * struct timekeeper - Structure holding internal timekeeping values. * @tkr: The readout base structure * @xtime_sec: Current CLOCK_REALTIME time in seconds + * @ktime_sec: Current CLOCK_MONOTONIC time in seconds * @wall_to_monotonic: CLOCK_REALTIME to CLOCK_MONOTONIC offset * @offs_real: Offset clock monotonic -> clock realtime * @offs_boot: Offset clock monotonic -> clock boottime @@ -77,6 +78,7 @@ struct tk_read_base { struct timekeeper { struct tk_read_base tkr; u64 xtime_sec; + u64 ktime_sec; struct timespec64 wall_to_monotonic; ktime_t offs_real; ktime_t offs_boot; diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h index 1caa6b0..115d55e 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); diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index ec1791f..7136a33 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -418,6 +418,8 @@ EXPORT_SYMBOL_GPL(pvclock_gtod_unregister_notifier); static inline void tk_update_ktime_data(struct timekeeper *tk) { s64 nsec; + u64 seconds; + s64 nsec_offset; /* * The xtime based monotonic readout is: @@ -426,13 +428,18 @@ static inline void tk_update_ktime_data(struct timekeeper *tk) * nsec = base_mono + now(); * ==> base_mono = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec */ - nsec = (s64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec); - nsec *= NSEC_PER_SEC; - nsec += tk->wall_to_monotonic.tv_nsec; + seconds = (s64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec); + nsec_offset = tk->wall_to_monotonic.tv_nsec; + nsec = seconds * NSEC_PER_SEC; + nsec += nsec_offset; tk->tkr.base_mono = ns_to_ktime(nsec); /* Update the monotonic raw base */ tk->base_raw = timespec64_to_ktime(tk->raw_time); + + if (((long)(tk->tkr.xtime_nsec >> tk->tkr.shift) + nsec_offset) >= NSEC_PER_SEC) + seconds += 1; + tk->ktime_sec = seconds; } /* must hold timekeeper_lock */ @@ -648,6 +655,24 @@ void ktime_get_ts64(struct timespec64 *ts) } EXPORT_SYMBOL_GPL(ktime_get_ts64); +time64_t ktime_get_seconds(void) +{ + time64_t seconds; + struct timekeeper *tk = &tk_core.timekeeper; + unsigned int seq; + + WARN_ON(timekeeping_suspended); + + do { + seq = read_seqcount_begin(&tk_core.seq); + seconds = tk->ktime_sec; + + } while (read_seqcount_retry(&tk_core.seq, seq)); + + return seconds; +} +EXPORT_SYMBOL_GPL(ktime_get_seconds); + #ifdef CONFIG_NTP_PPS /** -- 1.9.1
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