| 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 | extern void lockref_get(struct lockref *); |
| 38 | extern int lockref_put_return(struct lockref *); |
| 39 | extern int lockref_get_not_zero(struct lockref *); |
| 40 | extern int lockref_get_or_lock(struct lockref *); |
| 41 | extern int lockref_put_or_lock(struct lockref *); |
| 42 | |
| 43 | extern void lockref_mark_dead(struct lockref *); |
| 44 | extern int lockref_get_not_dead(struct lockref *); |
| 45 | |
| 46 | /* Must be called under spinlock for reliable results */ |
| 47 | static inline int __lockref_is_dead(const struct lockref *l) |
| 48 | { |
| 49 | return ((int)l->count < 0); |
| 50 | } |
| 51 | |
| 52 | #endif /* __LINUX_LOCKREF_H */ |