locking/lock_events: Use raw_cpu_{add,inc}() for stats

DECLARE_PER_CPU(unsigned long, lockevents[lockevent_num]);

/*

 * The purpose of the lock event counting subsystem is to provide a low

 * overhead way to record the number of specific locking events by using

 * percpu counters. It is the percpu sum that matters, not specifically

 * how many of them happens in each cpu.

 *

 * It is possible that the same percpu counter may be modified in both

 * the process and interrupt contexts. For architectures that perform

 * percpu operation with multiple instructions, it is possible to lose

 * count if a process context percpu update is interrupted in the middle

 * and the same counter is updated in the interrupt context. Therefore,

 * the generated percpu sum may not be precise. The error, if any, should

 * be small and insignificant.

 *

 * For those architectures that do multi-instruction percpu operation,

 * preemption in the middle and moving the task to another cpu may cause

 * a larger error in the count. Again, this will be few and far between.

 * Given the imprecise nature of the count and the possibility of resetting

 * the count and doing the measurement again, this is not really a big

 * problem.

 *

 * To get a better picture of what is happening under the hood, it is

 * suggested that a few measurements should be taken with the counts

 * reset in between to stamp out outliner because of these possible

 * error conditions.

 *

 * To minimize overhead, we use __this_cpu_*() in all cases except when

 * CONFIG_DEBUG_PREEMPT is defined. In this particular case, this_cpu_*()

 * will be used to avoid the appearance of unwanted BUG messages.

 */

#ifdef CONFIG_DEBUG_PREEMPT

#define lockevent_percpu_inc(x)		this_cpu_inc(x)

#define lockevent_percpu_add(x, v)	this_cpu_add(x, v)

#else

#define lockevent_percpu_inc(x)		__this_cpu_inc(x)

#define lockevent_percpu_add(x, v)	__this_cpu_add(x, v)

#endif

/*

 * Increment the PV qspinlock statistical counters

 * Increment the statistical counters. use raw_cpu_inc() because of lower

 * overhead and we don't care if we loose the occasional update.

 */

static inline void __lockevent_inc(enum lock_events event, bool cond)

{

	if (cond)

		lockevent_percpu_inc(lockevents[event]);

		raw_cpu_inc(lockevents[event]);

}

#define lockevent_inc(ev)	  __lockevent_inc(LOCKEVENT_ ##ev, true)

static inline void __lockevent_add(enum lock_events event, int inc)

{

	lockevent_percpu_add(lockevents[event], inc);

	raw_cpu_add(lockevents[event], inc);

}

#define lockevent_add(ev, c)	__lockevent_add(LOCKEVENT_ ##ev, c)