Merge branch 'timers-2038-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull more 2038 timer work from Thomas Gleixner:
 "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"

* 'timers-2038-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  timekeeping: Provide y2038 safe accessor to the seconds portion of CLOCK_REALTIME
  timekeeping: Provide fast accessor to the seconds part of CLOCK_MONOTONIC

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 961fea373f83..9b63d13ba82b 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -28,6 +28,8 @@ struct timespec __current_kernel_time(void);
 struct timespec64 get_monotonic_coarse64(void);
 extern void getrawmonotonic64(struct timespec64 *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 2dc0646258ae..6a931852082f 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
 
 /**