perf tools: Introduce trigger class

#ifndef __TRIGGER_H_

#define __TRIGGER_H_ 1

#include "util/debug.h"

#include "asm/bug.h"

/*

 * Use trigger to model operations which need to be executed when

 * an event (a signal, for example) is observed.

 *

 * States and transits:

 *

 *

 *  OFF--(on)--> READY --(hit)--> HIT

 *                 ^               |

 *                 |            (ready)

 *                 |               |

 *                  \_____________/

 *

 * is_hit and is_ready are two key functions to query the state of

 * a trigger. is_hit means the event already happen; is_ready means the

 * trigger is waiting for the event.

 */

struct trigger {

	volatile enum {

		TRIGGER_ERROR		= -2,

		TRIGGER_OFF		= -1,

		TRIGGER_READY		= 0,

		TRIGGER_HIT		= 1,

	} state;

	const char *name;

};

#define TRIGGER_WARN_ONCE(t, exp) \

	WARN_ONCE(t->state != exp, "trigger '%s' state transist error: %d in %s()\n", \

		  t->name, t->state, __func__)

static inline bool trigger_is_available(struct trigger *t)

{

	return t->state >= 0;

}

static inline bool trigger_is_error(struct trigger *t)

{

	return t->state <= TRIGGER_ERROR;

}

static inline void trigger_on(struct trigger *t)

{

	TRIGGER_WARN_ONCE(t, TRIGGER_OFF);

	t->state = TRIGGER_READY;

}

static inline void trigger_ready(struct trigger *t)

{

	if (!trigger_is_available(t))

		return;

	t->state = TRIGGER_READY;

}

static inline void trigger_hit(struct trigger *t)

{

	if (!trigger_is_available(t))

		return;

	TRIGGER_WARN_ONCE(t, TRIGGER_READY);

	t->state = TRIGGER_HIT;

}

static inline void trigger_off(struct trigger *t)

{

	if (!trigger_is_available(t))

		return;

	t->state = TRIGGER_OFF;

}

static inline void trigger_error(struct trigger *t)

{

	t->state = TRIGGER_ERROR;

}

static inline bool trigger_is_ready(struct trigger *t)

{

	return t->state == TRIGGER_READY;

}

static inline bool trigger_is_hit(struct trigger *t)

{

	return t->state == TRIGGER_HIT;

}

#define DEFINE_TRIGGER(n) \

struct trigger n = {.state = TRIGGER_OFF, .name = #n}

#endif