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 10 struct 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 23 static inline void osq_lock_init(struct optimistic_spin_queue *lock) 24 { 25 atomic_set(&lock->tail, OSQ_UNLOCKED_VAL); 26 } 27 28 extern bool osq_lock(struct optimistic_spin_queue *lock); 29 extern void osq_unlock(struct optimistic_spin_queue *lock); 30 31 static 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