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(7) for descriptions of the following attributes:
+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Committed |
+--------------------+-----------------+
SEE ALSO
attributes(7),
atomic_add(9F),
atomic_and(9F),
atomic_bits(9F),
atomic_cas(9F),
atomic_dec(9F),
atomic_inc(9F),
atomic_or(9F),
atomic_swap(9F),
membar_ops(9F)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(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.
March 28, 2005 ATOMIC_OPS(9F)
