atomic_ops(3C)															    atomic_ops(3C)

NAME

       atomic_ops - atomic operations

SYNOPSIS

       #include <atomic.h>

       This collection of functions provides atomic memory operations. There are 8 different classes of atomic operations:

       atomic_add(3C)  These functions provide an atomic addition 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 setting and clearing within a variable.

       atomic_cas(3C)  These  functions  provide  an  atomic comparison 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 decrement on a variable.

       atomic_inc(3C)  These functions provide an atomic increment 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.

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Stable			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

       atomic_add(3C), atomic_and(3C), atomic_bits(3C),  atomic_cas(3C),  atomic_dec(3C),  atomic_inc(3C),  atomic_or(3C),  atomic_swap(3C),  mem-
       bar_ops(3C), attributes(5)

       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  synchro-
       nization is required, memory barrier instructions must be used. See membar_ops(3C).

       Atomic  instructions can be expensive. since they require synchronization 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 atomically, 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.

								    12 Aug 2004 						    atomic_ops(3C)