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Message-ID: <20141029091317.GA1138@heena-HP-Compaq-8200-Elite-MT-PC>
Date: Wed, 29 Oct 2014 14:43:17 +0530
From: Heena Sirwani <heenasirwani@...il.com>
To: linux-kernel@...r.kernel.org
Cc: john.stultz@...aro.org, tglx@...utronix.de, arnd@...db.de
Subject: [PATCH v7] timekeeping: Added a function to return tv_sec portion of
ktime_get_ts64()
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@...il.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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