[GIT pull] timer fixes for 2.6.30

[GIT pull] timer fixes for 2.6.30

[Thomas Gleixner]

Linus,

Please pull the latest timers/urgent git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git timers/urgent

Thanks,

	tglx

------------------>
John Stultz (1):
      clockevents: prevent endless loop in tick_handle_periodic()


 kernel/time/tick-common.c |   12 +++++++++++-
 1 files changed, 11 insertions(+), 1 deletions(-)

diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 21a5ca8..83c4417 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -93,7 +93,17 @@ void tick_handle_periodic(struct clock_event_device *dev)
 	for (;;) {
 		if (!clockevents_program_event(dev, next, ktime_get()))
 			return;
-		tick_periodic(cpu);
+		/*
+		 * Have to be careful here. If we're in oneshot mode,
+		 * before we call tick_periodic() in a loop, we need
+		 * to be sure we're using a real hardware clocksource.
+		 * Otherwise we could get trapped in an infinite
+		 * loop, as the tick_periodic() increments jiffies,
+		 * when then will increment time, posibly causing
+		 * the loop to trigger again and again.
+		 */
+		if (timekeeping_valid_for_hres())
+			tick_periodic(cpu);
 		next = ktime_add(next, tick_period);
 	}
 }