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Commit 63070a79 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

hrtimer: catch expired CLOCK_REALTIME timers early 



A CLOCK_REALTIME timer, which has an absolute expiry time less than
the clock realtime offset calls with a negative delta into the clock
events code and triggers the WARN_ON() there.

This is a false positive and needs to be prevented. Check the result
of timer->expires - timer->base->offset right away and return -ETIME
right away.

Thanks to Frans Pop, who reported the problem and tested the fixes.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarFrans Pop <elendil@planet.nl>
parent 5a7780e7

kernel/hrtimer.c

+11 −0
Original line number Diff line number Diff line
@@ -442,6 +442,8 @@ static int hrtimer_reprogram(struct hrtimer *timer, 
	ktime_t expires = ktime_sub(timer->expires, base->offset);

	int res;



	WARN_ON_ONCE(timer->expires.tv64 < 0);



	/*

	 * When the callback is running, we do not reprogram the clock event

	 * device. The timer callback is either running on a different CPU or
@@ -452,6 +454,15 @@ static int hrtimer_reprogram(struct hrtimer *timer, 
	if (hrtimer_callback_running(timer))

		return 0;



	/*

	 * CLOCK_REALTIME timer might be requested with an absolute

	 * expiry time which is less than base->offset. Nothing wrong

	 * about that, just avoid to call into the tick code, which

	 * has now objections against negative expiry values.

	 */

	if (expires.tv64 < 0)

		return -ETIME;



	if (expires.tv64 >= expires_next->tv64)

		return 0;