blob: 4bfde0e99ed5169d7220204c39070faa387f57ab (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
|
#ifndef __LINUX_LOCKREF_H
#define __LINUX_LOCKREF_H
/*
* Locked reference counts.
*
* These are different from just plain atomic refcounts in that they
* are atomic with respect to the spinlock that goes with them. In
* particular, there can be implementations that don't actually get
* the spinlock for the common decrement/increment operations, but they
* still have to check that the operation is done semantically as if
* the spinlock had been taken (using a cmpxchg operation that covers
* both the lock and the count word, or using memory transactions, for
* example).
*/
#include <linux/spinlock.h>
#include <generated/bounds.h>
#define USE_CMPXCHG_LOCKREF \
(IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \
IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4)
struct lockref {
union {
#if USE_CMPXCHG_LOCKREF
aligned_u64 lock_count;
#endif
struct {
spinlock_t lock;
unsigned int count;
};
};
};
extern void lockref_get(struct lockref *);
extern int lockref_get_not_zero(struct lockref *);
extern int lockref_get_or_lock(struct lockref *);
extern int lockref_put_or_lock(struct lockref *);
extern void lockref_mark_dead(struct lockref *);
extern int lockref_get_not_dead(struct lockref *);
/* Must be called under spinlock for reliable results */
static inline int __lockref_is_dead(const struct lockref *l)
{
return ((int)l->count < 0);
}
#endif /* __LINUX_LOCKREF_H */
|
