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Annotation of src/lib/libc/atomic/atomic_cas.3, Revision 1.1

1.1     ! ad          1: .\"    $NetBSD: atomic_cas.3,v 1.3 2008/04/30 13:10:46 martin Exp $
        !             2: .\"
        !             3: .\" Copyright (c) 2007 The NetBSD Foundation, Inc.
        !             4: .\" All rights reserved.
        !             5: .\"
        !             6: .\" This code is derived from software contributed to The NetBSD Foundation
        !             7: .\" by Jason R. Thorpe.
        !             8: .\"
        !             9: .\" Redistribution and use in source and binary forms, with or without
        !            10: .\" modification, are permitted provided that the following conditions
        !            11: .\" are met:
        !            12: .\" 1. Redistributions of source code must retain the above copyright
        !            13: .\" notice, this list of conditions and the following disclaimer.
        !            14: .\" 2. Redistributions in binary form must reproduce the above copyright
        !            15: .\" notice, this list of conditions and the following disclaimer in the
        !            16: .\" documentation and/or other materials provided with the distribution.
        !            17: .\"
        !            18: .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
        !            19: .\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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        !            21: .\" PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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        !            24: .\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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        !            30: .Dd April 11, 2007
        !            31: .Dt ATOMIC_CAS 3
        !            32: .Os
        !            33: .Sh NAME
        !            34: .Nm atomic_cas ,
        !            35: .Nm atomic_cas_32 ,
        !            36: .Nm atomic_cas_uint ,
        !            37: .Nm atomic_cas_ulong ,
        !            38: .Nm atomic_cas_ptr ,
        !            39: .Nm atomic_cas_64
        !            40: .Nd atomic compare-and-swap operations
        !            41: .\" .Sh LIBRARY
        !            42: .\" .Lb libc
        !            43: .Sh SYNOPSIS
        !            44: .In sys/atomic.h
        !            45: .Ft uint32_t
        !            46: .Fn atomic_cas_32 "volatile uint32_t *ptr" "uint32_t old" "uint32_t new"
        !            47: .Ft unsigned int
        !            48: .Fn atomic_cas_uint "volatile unsigned int *ptr" "unsigned int old" \
        !            49:     "unsigned int new"
        !            50: .Ft unsigned long
        !            51: .Fn atomic_cas_ulong "volatile unsigned long *ptr" "unsigned long old" \
        !            52:     "unsigned long new"
        !            53: .Ft void *
        !            54: .Fn atomic_cas_ptr "volatile void *ptr" "void *old" "void *new"
        !            55: .Ft uint64_t
        !            56: .Fn atomic_cas_64 "volatile uint64_t *ptr" "uint64_t old" "uint64_t new"
        !            57: .Sh DESCRIPTION
        !            58: The
        !            59: .Nm atomic_cas
        !            60: family of functions perform a compare-and-swap operation in an atomic fashion.
        !            61: The value of the variable referenced by
        !            62: .Fa ptr
        !            63: is compared against
        !            64: .Fa old .
        !            65: If the values are equal,
        !            66: .Fa new
        !            67: is stored in the variable referenced by
        !            68: .Fa ptr .
        !            69: .Pp
        !            70: The old value of the variable referenced by
        !            71: .Fa ptr
        !            72: is always returned regardless of whether or not the new value was stored.
        !            73: Applications can test for success of the operation by comparing the
        !            74: return value to the value passed as
        !            75: .Fa old ;
        !            76: if they are equal then the new value was stored.
        !            77: .Pp
        !            78: The 64-bit variants of these functions are available only on platforms
        !            79: that can support atomic 64-bit memory access.
        !            80: Applications can check for the availability of 64-bit atomic memory
        !            81: operations by testing if the pre-processor macro
        !            82: .Dv __HAVE_ATOMIC64_OPS
        !            83: is defined.
        !            84: .Sh SEE ALSO
        !            85: .Xr atomic_ops 3
        !            86: .Sh HISTORY
        !            87: The
        !            88: .Nm atomic_cas
        !            89: functions first appeared in
        !            90: .Nx 5.0 .