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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 */ |