NAME

atomic_cas_uint, atomic_cas_ulong, atomic_cas_ptr — atomic compare-and-swap operations

SYNOPSIS

#include <>

unsigned int
atomic_cas_uint(volatile unsigned int *p, unsigned int expected, unsigned int new);

unsigned long
atomic_cas_ulong(volatile unsigned long *p, unsigned long expected, unsigned long new);

void *
atomic_cas_ptr(volatile void *p, void *expected, void *new);

DESCRIPTION

The atomic_cas set of functions provide an interface for atomically performing compare-and-swap operations with respect to interrupts and multiple processors in the system.

The value referenced by the pointer p is compared against expected. If these values are equal then new replaces the value stored at p.

CONTEXT

atomic_cas_uint(), atomic_cas_ulong(), and atomic_cas_ptr() can all be called during autoconf, from process context, or from interrupt context.

RETURN VALUES

These functions return the value at p as it was before the attempt to swap it.

SEE ALSO

atomic_swap_uint(9)

HISTORY

The atomic_cas functions first appeared in NetBSD 5.0 and OpenBSD 5.5.