atomic_ops(9F)						   Kernel Functions for Drivers 					    atomic_ops(9F)

NAME

       atomic_ops - atomic operations

SYNOPSIS

       #include <sys/atomic.h>

DESCRIPTION

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

       atomic_add(9F)	  These functions provide an atomic addition of a signed value to a variable.

       atomic_and(9F)	  These functions provide an atomic logical 'and' of a value to a variable.

       atomic_bits(9F)	  These functions provide atomic bit setting and clearing within a variable.

       atomic_cas(9F)	  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(9F)	  These functions provide an atomic decrement on a variable.

       atomic_inc(9F)	  These functions provide an atomic increment on a variable.

       atomic_or(9F)	  These functions provide an atomic logical 'or' of a value to a variable.

       atomic_swap(9F)	  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 attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Committed 		   |
       +-----------------------------+-----------------------------+

SEE ALSO

       atomic_add(9F), atomic_and(9F), atomic_bits(9F),  atomic_cas(9F),  atomic_dec(9F),  atomic_inc(9F),  atomic_or(9F),  atomic_swap(9F),  mem-
       bar_ops(9F), attributes(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  synchro-
       nization is required, memory barrier instructions must be used. See membar_ops(9F).

       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(9F) operation on each of them.

SunOS 5.11							    28 Mar 2005 						    atomic_ops(9F)