--- kernel/time/timekeeping.c

+++ kernel/time/timekeeping.c

@@ -168,8 +168,15 @@ int __read_mostly timekeeping_suspended;

static struct timespec xtime_cache __attribute__ ((aligned (16)));

void update_xtime_cache(u64 nsec)

{

- xtime_cache = xtime;

- timespec_add_ns(&xtime_cache, nsec);

+ /*

+ * Use temporary variable so get_seconds() cannot catch

+ * an intermediate xtime_cache.tv_sec value.

+ * The ACCESS_ONCE() keeps the compiler from optimizing

+ * out the intermediate value.

+ */

+ struct timespec ts = xtime;

+ timespec_add_ns(&ts, nsec);

+ ACCESS_ONCE(xtime_cache) = ts;

}

/* must hold xtime_lock */