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ATOMIC_ADD_INT(9) Kernel Developer's Manual ATOMIC_ADD_INT(9)

atomic_add_int, atomic_add_int_nv, atomic_add_long, atomic_add_long_nvatomic addition operations

#include <sys/atomic.h>

atomic_add_int(volatile unsigned int *p, unsigned int v);

unsigned int
atomic_add_int_nv(volatile unsigned int *p, unsigned int v);

atomic_add_long(volatile unsigned long *p, unsigned long v);

unsigned long
atomic_add_long_nv(volatile unsigned long *p, unsigned long v);

The atomic_add set of functions provide an interface for atomically performing add and add-and-fetch operations with respect to interrupts and multiple processors in the system.

The value referenced by the pointer p is incremented by the value v.

atomic_add_int(), atomic_add_int_nv(), atomic_add_long(), and atomic_add_long_nv() can all be called during autoconf, from process context, or from interrupt context.

atomic_add_int and atomic_add_long perform the addition without returning any knowledge of the value at p.

atomic_add_int_nv and atomic_add_long_nv return the value at p after the addition was performed.

atomic_inc_int(9), atomic_sub_int(9)

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

February 13, 2014 OpenBSD-current