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.\" $OpenBSD: atomic_swap_uint.9,v 1.6 2014/07/18 10:40:14 dlg Exp $
.\"
.\" Copyright (c) 2014 David Gwynne <dlg@openbsd.org>
.\" All rights reserved.
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: July 18 2014 $
.Dt ATOMIC_SWAP_UINT 9
.Os
.Sh NAME
.Nm atomic_swap_uint ,
.Nm atomic_swap_ulong ,
.Nm atomic_swap_ptr
.Nd atomic swap operations
.Sh SYNOPSIS
.In sys/atomic.h
.Ft unsigned int
.Fn atomic_swap_uint "volatile unsigned int *p" "unsigned int new"
.Ft unsigned long
.Fn atomic_swap_ulong "volatile unsigned long *p" "unsigned long new"
.Ft void *
.Fn atomic_swap_ptr "volatile void *p" "void *new"
.Sh DESCRIPTION
The atomic_swap set of functions provide an interface for atomically
performing swap operations with respect to interrupts and multiple
processors in the system.
.Pp
The value referenced by the pointer
.Fa p
is replaced by the value
.Fa new .
.Sh CONTEXT
.Fn atomic_swap_uint ,
.Fn atomic_swap_ulong ,
and
.Fn atomic_swap_ptr
can all be called during autoconf, from process context, or from interrupt context.
.Sh RETURN VALUES
These functions return the value at
.Fa p
as it was before the swap operation.
.Sh SEE ALSO
.Xr atomic_cas_uint 9
.Sh HISTORY
The atomic_swap functions first appeared in
.Nx 5.0
and
.Ox 5.5 .
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