Manual Pages for UNIX Operating System command usage for man atomic_ops

Standard C Library Functions                       atomic_ops(3C)



NAME
     atomic_ops - atomic operations

SYNOPSIS
     #include 


DESCRIPTION
     This collection of functions provides atomic  memory  opera-
     tions. There are 8 different classes of atomic operations:

     atomic_add(3C)     These functions provide an  atomic  addi-
                        tion of a signed value to a variable.


     atomic_and(3C)     These functions provide an atomic logical
                        'and' of a value to a variable.


     atomic_bits(3C)    These functions provide atomic  bit  set-
                        ting and clearing within a variable.


     atomic_cas(3C)     These functions provide  an  atomic  com-
                        parison  of  a  value with a variable. If
                        the comparison is equal, then swap  in  a
                        new value for the variable, returning the
                        old value of the variable in either case.


     atomic_dec(3C)     These functions provide an atomic  decre-
                        ment on a variable.


     atomic_inc(3C)     These functions provide an atomic  incre-
                        ment on a variable.


     atomic_or(3C)      These functions provide an atomic logical
                        'or' of a value to a variable.


     atomic_swap(3C)    These functions provide an atomic swap of
                        a  value  with  a variable, returning the
                        old value of the variable.


ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:





SunOS 5.11          Last change: 12 Aug 2004                    1






Standard C Library Functions                       atomic_ops(3C)



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|


SEE ALSO
     atomic_add(3C),       atomic_and(3C),       atomic_bits(3C),
     atomic_cas(3C),        atomic_dec(3C),       atomic_inc(3C),
     atomic_or(3C),   atomic_swap(3C),   membar_ops(3C),   attri-
     butes(5)

NOTES
     Atomic instructions ensure global visibility of  atomically-
     modified  variables on completion.  In a relaxed store order
     system, this does not guarantee that the visibility of other
     variables  will  be  synchronized with the completion of the
     atomic instruction. If  such  synchronization  is  required,
     memory    barrier    instructions    must   be   used.   See
     membar_ops(3C).


     Atomic instructions can be expensive since they require syn-
     chronization  to  occur at a hardware level. This means they
     should be used with care to  ensure  that  forcing  hardware
     level  synchronization occurs a minimum number of times. For
     example, if you have  several  variables  that  need  to  be
     incremented  as  a  group,  and each needs to be done atomi-
     cally, then do so with a mutex lock protecting all  of  them
     being  incremented  rather  than  using  the  atomic_inc(3C)
     operation on each of them.





















SunOS 5.11          Last change: 12 Aug 2004                    2