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Commit aff22d3f authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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

Pull timer fix from Ingo Molnar:
 "This tree contains a clockevents regression fix for certain ARM
  subarchitectures"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  clockevents: Sanitize ticks to nsec conversion
parents e2756f5e 97b94106

kernel/time/clockevents.c

+50 −15
Original line number Diff line number Diff line
@@ -33,29 +33,64 @@ struct ce_unbind { 
	int res;

};



/**

 * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds

 * @latch:	value to convert

 * @evt:	pointer to clock event device descriptor

 *

 * Math helper, returns latch value converted to nanoseconds (bound checked)

 */

u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)

static u64 cev_delta2ns(unsigned long latch, struct clock_event_device *evt,

			bool ismax)

{

	u64 clc = (u64) latch << evt->shift;

	u64 rnd;



	if (unlikely(!evt->mult)) {

		evt->mult = 1;

		WARN_ON(1);

	}

	rnd = (u64) evt->mult - 1;



	/*

	 * Upper bound sanity check. If the backwards conversion is

	 * not equal latch, we know that the above shift overflowed.

	 */

	if ((clc >> evt->shift) != (u64)latch)

		clc = ~0ULL;



	/*

	 * Scaled math oddities:

	 *

	 * For mult <= (1 << shift) we can safely add mult - 1 to

	 * prevent integer rounding loss. So the backwards conversion

	 * from nsec to device ticks will be correct.

	 *

	 * For mult > (1 << shift), i.e. device frequency is > 1GHz we

	 * need to be careful. Adding mult - 1 will result in a value

	 * which when converted back to device ticks can be larger

	 * than latch by up to (mult - 1) >> shift. For the min_delta

	 * calculation we still want to apply this in order to stay

	 * above the minimum device ticks limit. For the upper limit

	 * we would end up with a latch value larger than the upper

	 * limit of the device, so we omit the add to stay below the

	 * device upper boundary.

	 *

	 * Also omit the add if it would overflow the u64 boundary.

	 */

	if ((~0ULL - clc > rnd) &&

	    (!ismax || evt->mult <= (1U << evt->shift)))

		clc += rnd;



	do_div(clc, evt->mult);

	if (clc < 1000)

		clc = 1000;

	if (clc > KTIME_MAX)

		clc = KTIME_MAX;



	return clc;

	/* Deltas less than 1usec are pointless noise */

	return clc > 1000 ? clc : 1000;

}



/**

 * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds

 * @latch:	value to convert

 * @evt:	pointer to clock event device descriptor

 *

 * Math helper, returns latch value converted to nanoseconds (bound checked)

 */

u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)

{

	return cev_delta2ns(latch, evt, false);

}

EXPORT_SYMBOL_GPL(clockevent_delta2ns);
@@ -380,8 +415,8 @@ void clockevents_config(struct clock_event_device *dev, u32 freq) 
		sec = 600;



	clockevents_calc_mult_shift(dev, freq, sec);

	dev->min_delta_ns = clockevent_delta2ns(dev->min_delta_ticks, dev);

	dev->max_delta_ns = clockevent_delta2ns(dev->max_delta_ticks, dev);

	dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);

	dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);

}



/**