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(&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(&lock->tail) != OSQ_UNLOCKED_VAL; 34} 35 36#endif 37