aboutsummaryrefslogtreecommitdiffstats
path: root/include/linux/atomic.h
blob: 5b08a8540ecfc3e6bcb5bf8b6fbef4d19df93f55 (plain)
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
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
/* Atomic operations usable in machine independent code */
#ifndef _LINUX_ATOMIC_H
#define _LINUX_ATOMIC_H
#include <asm/atomic.h>

/**
 * atomic_add_unless - add unless the number is already a given value
 * @v: pointer of type atomic_t
 * @a: the amount to add to v...
 * @u: ...unless v is equal to u.
 *
 * Atomically adds @a to @v, so long as @v was not already @u.
 * Returns non-zero if @v was not @u, and zero otherwise.
 */
static inline int atomic_add_unless(atomic_t *v, int a, int u)
{
	return __atomic_add_unless(v, a, u) != u;
}

/**
 * atomic_inc_not_zero - increment unless the number is zero
 * @v: pointer of type atomic_t
 *
 * Atomically increments @v by 1, so long as @v is non-zero.
 * Returns non-zero if @v was non-zero, and zero otherwise.
 */
#ifndef atomic_inc_not_zero
#define atomic_inc_not_zero(v)		atomic_add_unless((v), 1, 0)
#endif

/**
 * atomic_inc_not_zero_hint - increment if not null
 * @v: pointer of type atomic_t
 * @hint: probable value of the atomic before the increment
 *
 * This version of atomic_inc_not_zero() gives a hint of probable
 * value of the atomic. This helps processor to not read the memory
 * before doing the atomic read/modify/write cycle, lowering
 * number of bus transactions on some arches.
 *
 * Returns: 0 if increment was not done, 1 otherwise.
 */
#ifndef atomic_inc_not_zero_hint
static inline int atomic_inc_not_zero_hint(atomic_t *v, int hint)
{
	int val, c = hint;

	/* sanity test, should be removed by compiler if hint is a constant */
	if (!hint)
		return atomic_inc_not_zero(v);

	do {
		val = atomic_cmpxchg(v, c, c + 1);
		if (val == c)
			return 1;
		c = val;
	} while (c);

	return 0;
}
#endif

#ifndef atomic_inc_unless_negative
static inline int atomic_inc_unless_negative(atomic_t *p)
{
	int v, v1;
	for (v = 0; v >= 0; v = v1) {
		v1 = atomic_cmpxchg(p, v, v + 1);
		if (likely(v1 == v))
			return 1;
	}
	return 0;
}
#endif

#ifndef atomic_dec_unless_positive
static inline int atomic_dec_unless_positive(atomic_t *p)
{
	int v, v1;
	for (v = 0; v <= 0; v = v1) {
		v1 = atomic_cmpxchg(p, v, v - 1);
		if (likely(v1 == v))
			return 1;
	}
	return 0;
}
#endif

/*
 * atomic_dec_if_positive - decrement by 1 if old value positive
 * @v: pointer of type atomic_t
 *
 * The function returns the old value of *v minus 1, even if
 * the atomic variable, v, was not decremented.
 */
#ifndef atomic_dec_if_positive
static inline int atomic_dec_if_positive(atomic_t *v)
{
	int c, old, dec;
	c = atomic_read(v);
	for (;;) {
		dec = c - 1;
		if (unlikely(dec < 0))
			break;
		old = atomic_cmpxchg((v), c, dec);
		if (likely(old == c))
			break;
		c = old;
	}
	return dec;
}
#endif

#ifndef CONFIG_ARCH_HAS_ATOMIC_OR
static inline void atomic_or(int i, atomic_t *v)
{
	int old;
	int new;

	do {
		old = atomic_read(v);
		new = old | i;
	} while (atomic_cmpxchg(v, old, new) != old);
}
#endif /* #ifndef CONFIG_ARCH_HAS_ATOMIC_OR */

#include <asm-generic/atomic-long.h>
#ifdef CONFIG_GENERIC_ATOMIC64
#include <asm-generic/atomic64.h>
#endif
#endif /* _LINUX_ATOMIC_H */