1 #ifndef __LINUX_OSQ_LOCK_H 2 #define __LINUX_OSQ_LOCK_H 3 4 /* 5 * An MCS like lock especially tailored for optimistic spinning for sleeping 6 * lock implementations (mutex, rwsem, etc). 7 */ 8 struct optimistic_spin_node { 9 struct optimistic_spin_node *next, *prev; 10 int locked; /* 1 if lock acquired */ 11 int cpu; /* encoded CPU # + 1 value */ 12 }; 13 14 struct optimistic_spin_queue { 15 /* 16 * Stores an encoded value of the CPU # of the tail node in the queue. 17 * If the queue is empty, then it's set to OSQ_UNLOCKED_VAL. 18 */ 19 atomic_t tail; 20 }; 21 22 #define OSQ_UNLOCKED_VAL (0) 23 24 /* Init macro and function. */ 25 #define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) } 26 27 static inline void osq_lock_init(struct optimistic_spin_queue *lock) 28 { 29 atomic_set(&lock->tail, OSQ_UNLOCKED_VAL); 30 } 31 32 extern bool osq_lock(struct optimistic_spin_queue *lock); 33 extern void osq_unlock(struct optimistic_spin_queue *lock); 34 35 static inline bool osq_is_locked(struct optimistic_spin_queue *lock) 36 { 37 return atomic_read(&lock->tail) != OSQ_UNLOCKED_VAL; 38 } 39 40 #endif 41