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 */
8struct 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};
13
14struct 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
22#define OSQ_UNLOCKED_VAL (0)
23
24/* Init macro and function. */
25#define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) }
26
27static inline void osq_lock_init(struct optimistic_spin_queue *lock)
28{
29	atomic_set(&lock->tail, OSQ_UNLOCKED_VAL);
30}
31
32extern bool osq_lock(struct optimistic_spin_queue *lock);
33extern void osq_unlock(struct optimistic_spin_queue *lock);
34
35#endif
36