1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __LINUX_OSQ_LOCK_H
3#define __LINUX_OSQ_LOCK_H
4
5/*
6 * An MCS like lock especially tailored for optimistic spinning for sleeping
7 * lock implementations (mutex, rwsem, etc).
8 */
9
10struct optimistic_spin_queue {
11 /*
12 * Stores an encoded value of the CPU # of the tail node in the queue.
13 * If the queue is empty, then it's set to OSQ_UNLOCKED_VAL.
14 */
15 atomic_t tail;
16};
17
18#define OSQ_UNLOCKED_VAL (0)
19
20/* Init macro and function. */
21#define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) }
22
23static inline void osq_lock_init(struct optimistic_spin_queue *lock)
24{
25 atomic_set(v: &lock->tail, OSQ_UNLOCKED_VAL);
26}
27
28extern bool osq_lock(struct optimistic_spin_queue *lock);
29extern void osq_unlock(struct optimistic_spin_queue *lock);
30
31static inline bool osq_is_locked(struct optimistic_spin_queue *lock)
32{
33 return atomic_read(v: &lock->tail) != OSQ_UNLOCKED_VAL;
34}
35
36#endif
37

source code of linux/include/linux/osq_lock.h