1atomic_ops(3C) Standard C Library Functions atomic_ops(3C)
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6 atomic_ops - atomic operations
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9 #include <atomic.h>
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13 This collection of functions provides atomic memory operations. There
14 are 8 different classes of atomic operations:
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16 atomic_add(3C) These functions provide an atomic addition of a
17 signed value to a variable.
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20 atomic_and(3C) These functions provide an atomic logical 'and' of a
21 value to a variable.
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24 atomic_bits(3C) These functions provide atomic bit setting and
25 clearing within a variable.
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28 atomic_cas(3C) These functions provide an atomic comparison of a
29 value with a variable. If the comparison is equal,
30 then swap in a new value for the variable, returning
31 the old value of the variable in either case.
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34 atomic_dec(3C) These functions provide an atomic decrement on a
35 variable.
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38 atomic_inc(3C) These functions provide an atomic increment on a
39 variable.
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42 atomic_or(3C) These functions provide an atomic logical 'or' of a
43 value to a variable.
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46 atomic_swap(3C) These functions provide an atomic swap of a value
47 with a variable, returning the old value of the
48 variable.
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52 See attributes(5) for descriptions of the following attributes:
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57 ┌─────────────────────────────┬─────────────────────────────┐
58 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
59 ├─────────────────────────────┼─────────────────────────────┤
60 │Interface Stability │Stable │
61 ├─────────────────────────────┼─────────────────────────────┤
62 │MT-Level │MT-Safe │
63 └─────────────────────────────┴─────────────────────────────┘
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66 atomic_add(3C), atomic_and(3C), atomic_bits(3C), atomic_cas(3C),
67 atomic_dec(3C), atomic_inc(3C), atomic_or(3C), atomic_swap(3C), mem‐
68 bar_ops(3C), attributes(5)
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71 Atomic instructions ensure global visibility of atomically-modified
72 variables on completion. In a relaxed store order system, this does
73 not guarantee that the visibility of other variables will be synchro‐
74 nized with the completion of the atomic instruction. If such synchro‐
75 nization is required, memory barrier instructions must be used. See
76 membar_ops(3C).
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79 Atomic instructions can be expensive since they require synchronization
80 to occur at a hardware level. This means they should be used with care
81 to ensure that forcing hardware level synchronization occurs a minimum
82 number of times. For example, if you have several variables that need
83 to be incremented as a group, and each needs to be done atomically,
84 then do so with a mutex lock protecting all of them being incremented
85 rather than using the atomic_inc(3C) operation on each of them.
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89SunOS 5.11 12 Aug 2004 atomic_ops(3C)