5 files changed, 40 insertions, 24 deletions

diff --git a/kernel/acct.c b/kernel/acct.c
index 70d0d88e5554..24f0f8b2ba72 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -468,7 +468,7 @@ static void do_acct_process(struct file *file)
         }
 #endif
         do_div(elapsed, AHZ);
-        ac.ac_btime = xtime.tv_sec - elapsed;
+        ac.ac_btime = get_seconds() - elapsed;
         /* we really need to bite the bullet and change layout */
         ac.ac_uid = current->uid;
         ac.ac_gid = current->gid;
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index eb1ddebd2c04..c21ca6bfaa66 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -141,11 +141,7 @@ static void hrtimer_get_softirq_time(struct hrtimer_cpu_base *base)
 
         do {
                 seq = read_seqbegin(&xtime_lock);
-#ifdef CONFIG_NO_HZ
-                getnstimeofday(&xts);
-#else
-                xts = xtime;
-#endif
+                xts = current_kernel_time();
                 tom = wall_to_monotonic;
         } while (read_seqretry(&xtime_lock, seq));
 
diff --git a/kernel/time.c b/kernel/time.c
index 5b81da08bbdb..2289a8d68314 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -215,22 +215,6 @@ asmlinkage long sys_adjtimex(struct timex __user *txc_p)
         return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
 }
 
-inline struct timespec current_kernel_time(void)
-{
-        struct timespec now;
-        unsigned long seq;
-
-        do {
-                seq = read_seqbegin(&xtime_lock);
-                
-                now = xtime;
-        } while (read_seqretry(&xtime_lock, seq));
-
-        return now; 
-}
-
-EXPORT_SYMBOL(current_kernel_time);
-
 /**
  * current_fs_time - Return FS time
  * @sb: Superblock.
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 88c81026e003..acc417b5a9b7 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -47,10 +47,22 @@ EXPORT_SYMBOL(xtime_lock);
 struct timespec xtime __attribute__ ((aligned (16)));
 struct timespec wall_to_monotonic __attribute__ ((aligned (16)));
 static unsigned long total_sleep_time;          /* seconds */
-
 EXPORT_SYMBOL(xtime);
 
 
+#ifdef CONFIG_NO_HZ
+static struct timespec xtime_cache __attribute__ ((aligned (16)));
+static inline void update_xtime_cache(u64 nsec)
+{
+        xtime_cache = xtime;
+        timespec_add_ns(&xtime_cache, nsec);
+}
+#else
+#define xtime_cache xtime
+/* We do *not* want to evaluate the argument for this case */
+#define update_xtime_cache(n) do { } while (0)
+#endif
+
 static struct clocksource *clock; /* pointer to current clocksource */
 
 
@@ -478,6 +490,8 @@ void update_wall_time(void)
         xtime.tv_nsec = (s64)clock->xtime_nsec >> clock->shift;
         clock->xtime_nsec -= (s64)xtime.tv_nsec << clock->shift;
 
+        update_xtime_cache(cyc2ns(clock, offset));
+
         /* check to see if there is a new clocksource to use */
         change_clocksource();
         update_vsyscall(&xtime, clock);
@@ -509,3 +523,25 @@ void monotonic_to_bootbased(struct timespec *ts)
 {
         ts->tv_sec += total_sleep_time;
 }
+
+unsigned long get_seconds(void)
+{
+        return xtime_cache.tv_sec;
+}
+EXPORT_SYMBOL(get_seconds);
+
+
+struct timespec current_kernel_time(void)
+{
+        struct timespec now;
+        unsigned long seq;
+
+        do {
+                seq = read_seqbegin(&xtime_lock);
+
+                now = xtime_cache;
+        } while (read_seqretry(&xtime_lock, seq));
+
+        return now;
+}
+EXPORT_SYMBOL(current_kernel_time);
diff --git a/kernel/tsacct.c b/kernel/tsacct.c
index 658f638c402c..c122131a122f 100644
--- a/kernel/tsacct.c
+++ b/kernel/tsacct.c
@@ -39,7 +39,7 @@ void bacct_add_tsk(struct taskstats *stats, struct task_struct *tsk)
         ac_etime = timespec_to_ns(&ts);
         do_div(ac_etime, NSEC_PER_USEC);
         stats->ac_etime = ac_etime;
-        stats->ac_btime = xtime.tv_sec - ts.tv_sec;
+        stats->ac_btime = get_seconds() - ts.tv_sec;
         if (thread_group_leader(tsk)) {
                 stats->ac_exitcode = tsk->exit_code;
                 if (tsk->flags & PF_FORKNOEXEC)