.\" $OpenBSD: atomic_dec_int.9,v 1.1 2014/02/03 07:03:04 dlg Exp $
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.\" Copyright (c) 2014 David Gwynne <dlg@openbsd.org>
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.Dd $Mdocdate: February 3 2014 $
.Dt ATOMIC_DEC 9
.Os
.Sh NAME
.Nm atomic_dec_int ,
.Nm atomic_dec_int_nv ,
.Nm atomic_dec_long ,
.Nm atomic_dec_long_nv
.Nd atomic decrement operations
.Sh SYNOPSIS
.In sys/atomic.h
.Ft void
.Fn atomic_dec_int "volatile unsigned int *p"
.Ft unsigned int
.Fn atomic_dec_int_nv "volatile unsigned int *p"
.Ft void
.Fn atomic_dec_long "volatile unsigned long *p "
.Ft unsigned long
.Fn atomic_dec_long_nv "volatile unsigned long *p"
.Sh DESCRIPTION
The atomic_dec set of functions provide an interface for atomically
performing decrement and decrement-and-fetch operations with respect
to interrupts and multiple processors in the system.
.Pp
The value referenced by the pointer
.Fa p
is decremented by 1.
.Sh RETURN VALUES
.Nm atomic_dec_int
and
.Nm atomic_dec_long
perform the decrement without returning any knowledge of the value at the
.Fa p .
.Pp
.Nm atomic_dec_int_nv
and
.Nm atomic_dec_long_nv
return the value at
.Fa p
after the decrement was performed.
.Sh SEE ALSO
.Xr atomic 9 ,
.Xr atomic_add_int 9 ,
.Xr atomic_inc_int 9
.Sh HISTORY
The atomic_add functions first appeared in
.Ox 5.5 .