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Date: Tue, 9 Dec 2014 15:52:59 +0100 (CET)
From: Thomas Gleixner <tglx@...utronix.de>
To: Linus Torvalds <torvalds@...ux-foundation.org>
cc: LKML <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Ingo Molnar <mingo@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>, Arnd Bergman <arnd@...db.de>
Subject: [GIT pull] More 2038 timer work for 3.19
Linus,
please pull the latest timers-2038-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers-2038-for-linus
Two more patches for the ongoing 2038 work:
- New accessors to clock MONOTONIC and REALTIME seconds
This is a seperate branch as Arnd has follow up work depending on
this.
Thanks,
tglx
------------------>
Heena Sirwani (2):
timekeeping: Provide fast accessor to the seconds part of CLOCK_MONOTONIC
timekeeping: Provide y2038 safe accessor to the seconds portion of CLOCK_REALTIME
include/linux/timekeeper_internal.h | 2 ++
include/linux/timekeeping.h | 2 ++
kernel/time/timekeeping.c | 68 ++++++++++++++++++++++++++++++++++---
3 files changed, 67 insertions(+), 5 deletions(-)
diff --git a/include/linux/timekeeper_internal.h b/include/linux/timekeeper_internal.h
index 95640dcd1899..05af9a334893 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;
+ unsigned long 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 1caa6b04fdc5..91454dea2bc6 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -28,6 +28,8 @@ 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 time64_t ktime_get_real_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 ec1791fae965..0aef92a0a701 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -417,7 +417,8 @@ EXPORT_SYMBOL_GPL(pvclock_gtod_unregister_notifier);
*/
static inline void tk_update_ktime_data(struct timekeeper *tk)
{
- s64 nsec;
+ u64 seconds;
+ u32 nsec;
/*
* The xtime based monotonic readout is:
@@ -426,13 +427,22 @@ 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;
- tk->tkr.base_mono = ns_to_ktime(nsec);
+ seconds = (u64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec);
+ nsec = (u32) tk->wall_to_monotonic.tv_nsec;
+ tk->tkr.base_mono = ns_to_ktime(seconds * NSEC_PER_SEC + nsec);
/* Update the monotonic raw base */
tk->base_raw = timespec64_to_ktime(tk->raw_time);
+
+ /*
+ * The sum of the nanoseconds portions of xtime and
+ * wall_to_monotonic can be greater/equal one second. Take
+ * this into account before updating tk->ktime_sec.
+ */
+ nsec += (u32)(tk->tkr.xtime_nsec >> tk->tkr.shift);
+ if (nsec >= NSEC_PER_SEC)
+ seconds++;
+ tk->ktime_sec = seconds;
}
/* must hold timekeeper_lock */
@@ -648,6 +658,54 @@ void ktime_get_ts64(struct timespec64 *ts)
}
EXPORT_SYMBOL_GPL(ktime_get_ts64);
+/**
+ * ktime_get_seconds - Get the seconds portion of CLOCK_MONOTONIC
+ *
+ * Returns the seconds portion of CLOCK_MONOTONIC with a single non
+ * serialized read. tk->ktime_sec is of type 'unsigned long' so this
+ * works on both 32 and 64 bit systems. On 32 bit systems the readout
+ * covers ~136 years of uptime which should be enough to prevent
+ * premature wrap arounds.
+ */
+time64_t ktime_get_seconds(void)
+{
+ struct timekeeper *tk = &tk_core.timekeeper;
+
+ WARN_ON(timekeeping_suspended);
+ return tk->ktime_sec;
+}
+EXPORT_SYMBOL_GPL(ktime_get_seconds);
+
+/**
+ * ktime_get_real_seconds - Get the seconds portion of CLOCK_REALTIME
+ *
+ * Returns the wall clock seconds since 1970. This replaces the
+ * get_seconds() interface which is not y2038 safe on 32bit systems.
+ *
+ * For 64bit systems the fast access to tk->xtime_sec is preserved. On
+ * 32bit systems the access must be protected with the sequence
+ * counter to provide "atomic" access to the 64bit tk->xtime_sec
+ * value.
+ */
+time64_t ktime_get_real_seconds(void)
+{
+ struct timekeeper *tk = &tk_core.timekeeper;
+ time64_t seconds;
+ unsigned int seq;
+
+ if (IS_ENABLED(CONFIG_64BIT))
+ return tk->xtime_sec;
+
+ do {
+ seq = read_seqcount_begin(&tk_core.seq);
+ seconds = tk->xtime_sec;
+
+ } while (read_seqcount_retry(&tk_core.seq, seq));
+
+ return seconds;
+}
+EXPORT_SYMBOL_GPL(ktime_get_real_seconds);
+
#ifdef CONFIG_NTP_PPS
/**
--
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