[linux-2.6-block.git] / include / linux / osq_lock.h

#ifndef __LINUX_OSQ_LOCK_H
#define __LINUX_OSQ_LOCK_H

/*
 * An MCS like lock especially tailored for optimistic spinning for sleeping
 * lock implementations (mutex, rwsem, etc).
 */
struct optimistic_spin_node {
	struct optimistic_spin_node *next, *prev;
	int locked; /* 1 if lock acquired */
	int cpu; /* encoded CPU # + 1 value */
};

struct optimistic_spin_queue {
	/*
	 * Stores an encoded value of the CPU # of the tail node in the queue.
	 * If the queue is empty, then it's set to OSQ_UNLOCKED_VAL.
	 */
	atomic_t tail;
};

#define OSQ_UNLOCKED_VAL (0)

/* Init macro and function. */
#define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) }

static inline void osq_lock_init(struct optimistic_spin_queue *lock)
{
	atomic_set(&lock->tail, OSQ_UNLOCKED_VAL);
}

extern bool osq_lock(struct optimistic_spin_queue *lock);
extern void osq_unlock(struct optimistic_spin_queue *lock);

#endif
Commit	Line	Data
90631822 JL	1	#ifndef __LINUX_OSQ_LOCK_H
	2	#define __LINUX_OSQ_LOCK_H
	3
	4	/*
	5	* An MCS like lock especially tailored for optimistic spinning for sleeping
	6	* lock implementations (mutex, rwsem, etc).
	7	*/
d84b6728 DB	8	struct optimistic_spin_node {
	9	struct optimistic_spin_node next, prev;
	10	int locked; /* 1 if lock acquired */
	11	int cpu; /* encoded CPU # + 1 value */
	12	};
90631822 JL	13
	14	struct optimistic_spin_queue {
	15	/*
	16	* Stores an encoded value of the CPU # of the tail node in the queue.
	17	* If the queue is empty, then it's set to OSQ_UNLOCKED_VAL.
	18	*/
	19	atomic_t tail;
	20	};
	21
d84b6728 DB	22	#define OSQ_UNLOCKED_VAL (0)
d84b6728 DB	23
4d9d951e JL	24	/* Init macro and function. */
	25	#define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) }
	26
	27	static inline void osq_lock_init(struct optimistic_spin_queue *lock)
	28	{
	29	atomic_set(&lock->tail, OSQ_UNLOCKED_VAL);
	30	}
	31
d84b6728 DB	32	extern bool osq_lock(struct optimistic_spin_queue *lock);
	33	extern void osq_unlock(struct optimistic_spin_queue *lock);
	34
90631822	35	#endif