[patch 12/28] clockevents: prevent endless loop in periodic broadcast handler

[Greg KH <gregkh@suse.de>]

[-- Attachment #1: timer-fix-02.patch --]
[-- Type: text/plain, Size: 1686 bytes --]

2.6.25-stable review patch.  If anyone has any objections, please let us
know.

------------------
From: Thomas Gleixner <tglx@linutronix.de>

commit d4496b39559c6d43f83e4c08b899984f8b8089b5 upstream

The reprogramming of the periodic broadcast handler was broken,
when the first programming returned -ETIME. The clockevents code
stores the new expiry value in the clock events device next_event field
only when the programming time has not been elapsed yet. The loop in
question calculates the new expiry value from the next_event value
and therefor never increases.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 kernel/time/tick-broadcast.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -174,6 +174,8 @@ static void tick_do_periodic_broadcast(v
  */
 static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 {
+	ktime_t next;
+
 	tick_do_periodic_broadcast();
 
 	/*
@@ -184,10 +186,13 @@ static void tick_handle_periodic_broadca
 
 	/*
 	 * Setup the next period for devices, which do not have
-	 * periodic mode:
+	 * periodic mode. We read dev->next_event first and add to it
+	 * when the event alrady expired. clockevents_program_event()
+	 * sets dev->next_event only when the event is really
+	 * programmed to the device.
 	 */
-	for (;;) {
-		ktime_t next = ktime_add(dev->next_event, tick_period);
+	for (next = dev->next_event; ;) {
+		next = ktime_add(next, tick_period);
 
 		if (!clockevents_program_event(dev, next, ktime_get()))
 			return;

--