Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  time: Fix stupid KERN_WARN compile issue
  rtc: Avoid accumulating time drift in suspend/resume
  time: Avoid accumulating time drift in suspend/resume
  time: Catch invalid timespec sleep values in __timekeeping_inject_sleeptime

1 files changed, 28 insertions, 0 deletions

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 342408cf68dd..2b021b0e8507 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -604,6 +604,12 @@ static struct timespec timekeeping_suspend_time;
  */
 static void __timekeeping_inject_sleeptime(struct timespec *delta)
 {
+        if (!timespec_valid(delta)) {
+                printk(KERN_WARNING "__timekeeping_inject_sleeptime: Invalid "
+                                        "sleep delta value!\n");
+                return;
+        }
+
         xtime = timespec_add(xtime, *delta);
         wall_to_monotonic = timespec_sub(wall_to_monotonic, *delta);
         total_sleep_time = timespec_add(total_sleep_time, *delta);
@@ -686,12 +692,34 @@ static void timekeeping_resume(void)
 static int timekeeping_suspend(void)
 {
         unsigned long flags;
+        struct timespec         delta, delta_delta;
+        static struct timespec  old_delta;
 
         read_persistent_clock(&timekeeping_suspend_time);
 
         write_seqlock_irqsave(&xtime_lock, flags);
         timekeeping_forward_now();
         timekeeping_suspended = 1;
+
+        /*
+         * To avoid drift caused by repeated suspend/resumes,
+         * which each can add ~1 second drift error,
+         * try to compensate so the difference in system time
+         * and persistent_clock time stays close to constant.
+         */
+        delta = timespec_sub(xtime, timekeeping_suspend_time);
+        delta_delta = timespec_sub(delta, old_delta);
+        if (abs(delta_delta.tv_sec)  >= 2) {
+                /*
+                 * if delta_delta is too large, assume time correction
+                 * has occured and set old_delta to the current delta.
+                 */
+                old_delta = delta;
+        } else {
+                /* Otherwise try to adjust old_system to compensate */
+                timekeeping_suspend_time =
+                        timespec_add(timekeeping_suspend_time, delta_delta);
+        }
         write_sequnlock_irqrestore(&xtime_lock, flags);
 
         clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);