Commit 6626bff2 authored Jan 25, 2009 by Thomas Gleixner

hrtimer: prevent negative expiry value after clock_was_set()



Impact: prevent false positive WARN_ON() in clockevents_program_event()

clock_was_set() changes the base->offset of CLOCK_REALTIME and
enforces the reprogramming of the clockevent device to expire timers
which are based on CLOCK_REALTIME. If the clock change is large enough
then the subtraction of the timer expiry value and base->offset can
become negative which triggers the warning in
clockevents_program_event(). 

Check the subtraction result and set a negative value to 0.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

parent 5b74f9e0

kernel/hrtimer.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -501,6 +501,13 @@ static void hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base)
		continue;
		timer = rb_entry(base->first, struct hrtimer, node);
		expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
		/*
		* clock_was_set() has changed base->offset so the
		* result might be negative. Fix it up to prevent a
		* false positive in clockevents_program_event()
		*/
		if (expires.tv64 < 0)
		expires.tv64 = 0;
		if (expires.tv64 < cpu_base->expires_next.tv64)
		cpu_base->expires_next = expires;
		}