1 /* Atomic operations usable in machine independent code */
2 #ifndef _LINUX_ATOMIC_H
3 #define _LINUX_ATOMIC_H
4 #include <asm/atomic.h>
5
6 /**
7 * atomic_add_unless - add unless the number is already a given value
8 * @v: pointer of type atomic_t
9 * @a: the amount to add to v...
10 * @u: ...unless v is equal to u.
11 *
12 * Atomically adds @a to @v, so long as @v was not already @u.
13 * Returns non-zero if @v was not @u, and zero otherwise.
14 */
atomic_add_unless(atomic_t * v,int a,int u)15 static inline int atomic_add_unless(atomic_t *v, int a, int u)
16 {
17 return __atomic_add_unless(v, a, u) != u;
18 }
19
20 /**
21 * atomic_inc_not_zero - increment unless the number is zero
22 * @v: pointer of type atomic_t
23 *
24 * Atomically increments @v by 1, so long as @v is non-zero.
25 * Returns non-zero if @v was non-zero, and zero otherwise.
26 */
27 #ifndef atomic_inc_not_zero
28 #define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
29 #endif
30
31 /**
32 * atomic_inc_not_zero_hint - increment if not null
33 * @v: pointer of type atomic_t
34 * @hint: probable value of the atomic before the increment
35 *
36 * This version of atomic_inc_not_zero() gives a hint of probable
37 * value of the atomic. This helps processor to not read the memory
38 * before doing the atomic read/modify/write cycle, lowering
39 * number of bus transactions on some arches.
40 *
41 * Returns: 0 if increment was not done, 1 otherwise.
42 */
43 #ifndef atomic_inc_not_zero_hint
atomic_inc_not_zero_hint(atomic_t * v,int hint)44 static inline int atomic_inc_not_zero_hint(atomic_t *v, int hint)
45 {
46 int val, c = hint;
47
48 /* sanity test, should be removed by compiler if hint is a constant */
49 if (!hint)
50 return atomic_inc_not_zero(v);
51
52 do {
53 val = atomic_cmpxchg(v, c, c + 1);
54 if (val == c)
55 return 1;
56 c = val;
57 } while (c);
58
59 return 0;
60 }
61 #endif
62
63 #ifndef atomic_inc_unless_negative
atomic_inc_unless_negative(atomic_t * p)64 static inline int atomic_inc_unless_negative(atomic_t *p)
65 {
66 int v, v1;
67 for (v = 0; v >= 0; v = v1) {
68 v1 = atomic_cmpxchg(p, v, v + 1);
69 if (likely(v1 == v))
70 return 1;
71 }
72 return 0;
73 }
74 #endif
75
76 #ifndef atomic_dec_unless_positive
atomic_dec_unless_positive(atomic_t * p)77 static inline int atomic_dec_unless_positive(atomic_t *p)
78 {
79 int v, v1;
80 for (v = 0; v <= 0; v = v1) {
81 v1 = atomic_cmpxchg(p, v, v - 1);
82 if (likely(v1 == v))
83 return 1;
84 }
85 return 0;
86 }
87 #endif
88
89 /*
90 * atomic_dec_if_positive - decrement by 1 if old value positive
91 * @v: pointer of type atomic_t
92 *
93 * The function returns the old value of *v minus 1, even if
94 * the atomic variable, v, was not decremented.
95 */
96 #ifndef atomic_dec_if_positive
atomic_dec_if_positive(atomic_t * v)97 static inline int atomic_dec_if_positive(atomic_t *v)
98 {
99 int c, old, dec;
100 c = atomic_read(v);
101 for (;;) {
102 dec = c - 1;
103 if (unlikely(dec < 0))
104 break;
105 old = atomic_cmpxchg((v), c, dec);
106 if (likely(old == c))
107 break;
108 c = old;
109 }
110 return dec;
111 }
112 #endif
113
114 #ifndef CONFIG_ARCH_HAS_ATOMIC_OR
atomic_or(int i,atomic_t * v)115 static inline void atomic_or(int i, atomic_t *v)
116 {
117 int old;
118 int new;
119
120 do {
121 old = atomic_read(v);
122 new = old | i;
123 } while (atomic_cmpxchg(v, old, new) != old);
124 }
125 #endif /* #ifndef CONFIG_ARCH_HAS_ATOMIC_OR */
126
127 #include <asm-generic/atomic-long.h>
128 #ifdef CONFIG_GENERIC_ATOMIC64
129 #include <asm-generic/atomic64.h>
130 #endif
131 #endif /* _LINUX_ATOMIC_H */
132