1 #ifndef __LINUX_LOCKREF_H 2 #define __LINUX_LOCKREF_H 3 4 /* 5 * Locked reference counts. 6 * 7 * These are different from just plain atomic refcounts in that they 8 * are atomic with respect to the spinlock that goes with them. In 9 * particular, there can be implementations that don't actually get 10 * the spinlock for the common decrement/increment operations, but they 11 * still have to check that the operation is done semantically as if 12 * the spinlock had been taken (using a cmpxchg operation that covers 13 * both the lock and the count word, or using memory transactions, for 14 * example). 15 */ 16 17 #include <linux/spinlock.h> 18 #include <generated/bounds.h> 19 20 #define USE_CMPXCHG_LOCKREF \ 21 (IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \ 22 IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4) 23 24 struct lockref { 25 union { 26 #if USE_CMPXCHG_LOCKREF 27 aligned_u64 lock_count; 28 #endif 29 struct { 30 spinlock_t lock; 31 int count; 32 }; 33 }; 34 }; 35 36 extern void lockref_get(struct lockref *); 37 extern int lockref_put_return(struct lockref *); 38 extern int lockref_get_not_zero(struct lockref *); 39 extern int lockref_get_or_lock(struct lockref *); 40 extern int lockref_put_or_lock(struct lockref *); 41 42 extern void lockref_mark_dead(struct lockref *); 43 extern int lockref_get_not_dead(struct lockref *); 44 45 /* Must be called under spinlock for reliable results */ 46 static inline int __lockref_is_dead(const struct lockref *l) 47 { 48 return ((int)l->count < 0); 49 } 50 51 #endif /* __LINUX_LOCKREF_H */ 52