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 struct optimistic_spin_node { 10 struct optimistic_spin_node *next, *prev; 11 int locked; /* 1 if lock acquired */ 12 int cpu; /* encoded CPU # + 1 value */ 13 }; 14 15 struct optimistic_spin_queue { 16 /* 17 * Stores an encoded value of the CPU # of the tail node in the queue. 18 * If the queue is empty, then it's set to OSQ_UNLOCKED_VAL. 19 */ 20 atomic_t tail; 21 }; 22 23 #define OSQ_UNLOCKED_VAL (0) 24 25 /* Init macro and function. */ 26 #define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) } 27 osq_lock_init(struct optimistic_spin_queue * lock)28 static inline void osq_lock_init(struct optimistic_spin_queue *lock) 29 { 30 atomic_set(&lock->tail, OSQ_UNLOCKED_VAL); 31 } 32 33 extern bool osq_lock(struct optimistic_spin_queue *lock); 34 extern void osq_unlock(struct optimistic_spin_queue *lock); 35 osq_is_locked(struct optimistic_spin_queue * lock)36 static inline bool osq_is_locked(struct optimistic_spin_queue *lock) 37 { 38 return atomic_read(&lock->tail) != OSQ_UNLOCKED_VAL; 39 } 40 41 #endif 42