1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __LINUX_LOCKREF_H 3 #define __LINUX_LOCKREF_H 4 5 /* 6 * Locked reference counts. 7 * 8 * These are different from just plain atomic refcounts in that they 9 * are atomic with respect to the spinlock that goes with them. In 10 * particular, there can be implementations that don't actually get 11 * the spinlock for the common decrement/increment operations, but they 12 * still have to check that the operation is done semantically as if 13 * the spinlock had been taken (using a cmpxchg operation that covers 14 * both the lock and the count word, or using memory transactions, for 15 * example). 16 */ 17 18 #include <linux/spinlock.h> 19 #include <generated/bounds.h> 20 21 #define USE_CMPXCHG_LOCKREF \ 22 (IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \ 23 IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4) 24 25 struct lockref { 26 union { 27 #if USE_CMPXCHG_LOCKREF 28 aligned_u64 lock_count; 29 #endif 30 struct { 31 spinlock_t lock; 32 int count; 33 }; 34 }; 35 }; 36 37 /** 38 * lockref_init - Initialize a lockref 39 * @lockref: pointer to lockref structure 40 * @count: initial count 41 */ 42 static inline void lockref_init(struct lockref *lockref, unsigned int count) 43 { 44 spin_lock_init(&lockref->lock); 45 lockref->count = count; 46 } 47 48 void lockref_get(struct lockref *lockref); 49 int lockref_put_return(struct lockref *lockref); 50 bool lockref_get_not_zero(struct lockref *lockref); 51 bool lockref_put_or_lock(struct lockref *lockref); 52 53 void lockref_mark_dead(struct lockref *lockref); 54 bool lockref_get_not_dead(struct lockref *lockref); 55 56 /* Must be called under spinlock for reliable results */ 57 static inline bool __lockref_is_dead(const struct lockref *l) 58 { 59 return ((int)l->count < 0); 60 } 61 62 #endif /* __LINUX_LOCKREF_H */ 63