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1/* SPDX-License-Identifier: GPL-2.0 */2#ifndef __LINUX_OSQ_LOCK_H3#define __LINUX_OSQ_LOCK_H4 5/*6 * An MCS like lock especially tailored for optimistic spinning for sleeping7 * 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#endif37