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Message-Id: <eee0b50afdea829c727d6210afb8299a4cf30981.1337348892.git.richardcochran@gmail.com>
Date: Fri, 18 May 2012 16:09:56 +0200
From: Richard Cochran <richardcochran@...il.com>
To: <linux-kernel@...r.kernel.org>
Cc: John Stultz <john.stultz@...aro.org>,
Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH RFC V2 4/6] time: introduce leap second functional interface
This patch adds a new private leap second interface for use by the NTP
code. In addition to methods for starting and ending leap seconds, the
interface provides a way to get the correct UTC time of day even during
a leap second.
Signed-off-by: Richard Cochran <richardcochran@...il.com>
---
kernel/time/leap-seconds.h | 21 +++++++
kernel/time/timekeeping.c | 129 ++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 150 insertions(+), 0 deletions(-)
create mode 100644 kernel/time/leap-seconds.h
diff --git a/kernel/time/leap-seconds.h b/kernel/time/leap-seconds.h
new file mode 100644
index 0000000..3dea7b0
--- /dev/null
+++ b/kernel/time/leap-seconds.h
@@ -0,0 +1,21 @@
+/*
+ * linux/kernel/time/leap-seconds.h
+ *
+ * Functional interface to the timekeeper code,
+ * for use by the NTP code.
+ *
+ */
+#ifndef __LINUX_KERNEL_TIME_LEAP_SECONDS_H
+#define __LINUX_KERNEL_TIME_LEAP_SECONDS_H
+
+#include <linux/time.h>
+
+int timekeeping_gettod_status(struct timespec *ts, time_t *offset);
+
+void timekeeping_delete_leap_second(void);
+
+void timekeeping_finish_leap_second(void);
+
+void timekeeping_insert_leap_second(void);
+
+#endif
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index ac04de4..eab03fb 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -21,6 +21,8 @@
#include <linux/tick.h>
#include <linux/stop_machine.h>
+#include "leap-seconds.h"
+
/* Structure holding internal timekeeping values. */
struct timekeeper {
/* Current clocksource used for timekeeping. */
@@ -1290,3 +1292,130 @@ void xtime_update(unsigned long ticks)
do_timer(ticks);
write_sequnlock(&xtime_lock);
}
+
+/**
+ * zero_hour - Returns the time of the next zero hour.
+ */
+static time_t zero_hour(time_t now)
+{
+ time_t days = now / 86400;
+ time_t zero = (1 + days) * 86400;
+ return zero;
+}
+
+/**
+ * timekeeping_delete_leap_second - Delete a leap second today.
+ */
+void timekeeping_delete_leap_second(void)
+{
+ unsigned long flags;
+
+ write_seqlock_irqsave(&timekeeper.lock, flags);
+
+ if (timekeeper.leap_state == LEAP_IDLE) {
+ timekeeper.utc_epoch = zero_hour(timekeeper.xtime.tv_sec);
+ timekeeper.leap_state = LEAP_DEL_PENDING;
+ }
+ write_sequnlock_irqrestore(&timekeeper.lock, flags);
+}
+
+/**
+ * timekeeping_finish_leap_second - Advance the leap second threshold.
+ */
+void timekeeping_finish_leap_second(void)
+{
+ unsigned long flags;
+
+ write_seqlock_irqsave(&timekeeper.lock, flags);
+
+ if (timekeeper.leap_state == LEAP_INS_DONE ||
+ timekeeper.leap_state == LEAP_DEL_DONE) {
+ timekeeper.utc_epoch = LONG_MAX;
+ timekeeper.leap_state = LEAP_IDLE;
+ }
+ write_sequnlock_irqrestore(&timekeeper.lock, flags);
+}
+
+/**
+ * timekeeping_insert_leap_second - Add a leap second today.
+ */
+void timekeeping_insert_leap_second(void)
+{
+ unsigned long flags;
+
+ write_seqlock_irqsave(&timekeeper.lock, flags);
+
+ if (timekeeper.leap_state == LEAP_IDLE) {
+ timekeeper.utc_epoch = zero_hour(timekeeper.xtime.tv_sec);
+ timekeeper.leap_state = LEAP_INS_PENDING;
+ }
+ write_sequnlock_irqrestore(&timekeeper.lock, flags);
+}
+
+/**
+ * timekeeping_gettod_status - Get the current time, TAI offset,
+ * and leap second status.
+ */
+int timekeeping_gettod_status(struct timespec *ts, time_t *offset)
+{
+ int code = TIME_OK, leap_state;
+ time_t diff, epoch, taioff;
+ unsigned long seq;
+ s64 nsecs;
+
+ WARN_ON(timekeeping_suspended);
+
+ do {
+ seq = read_seqbegin(&timekeeper.lock);
+ *ts = timekeeper.xtime;
+ nsecs = timekeeping_get_ns();
+ nsecs += arch_gettimeoffset();
+ taioff = timekeeper.tai_offset;
+ epoch = timekeeper.utc_epoch;
+ leap_state = timekeeper.leap_state;
+ } while (read_seqretry(&timekeeper.lock, seq));
+
+ timespec_add_ns(ts, nsecs);
+
+ switch (leap_state) {
+ case LEAP_IDLE:
+ break;
+
+ case LEAP_INS_PENDING:
+ diff = epoch - ts->tv_sec;
+ if (diff > 0) {
+ code = TIME_INS;
+ } else {
+ code = diff ? TIME_WAIT : TIME_OOP;
+ ts->tv_sec--;
+ taioff++;
+ }
+ break;
+
+ case LEAP_INS_DONE:
+ diff = epoch - ts->tv_sec;
+ if (diff > 0)
+ code = TIME_OOP;
+ else
+ code = TIME_WAIT;
+ break;
+
+ case LEAP_DEL_PENDING:
+ diff = epoch - ts->tv_sec;
+ if (diff < 2) {
+ code = TIME_WAIT;
+ ts->tv_sec++;
+ taioff--;
+ } else {
+ code = TIME_DEL;
+ }
+ break;
+
+ case LEAP_DEL_DONE:
+ code = TIME_WAIT;
+ break;
+ }
+
+ *offset = taioff;
+ return code;
+}
--
1.7.2.5
--
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