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      1 /*	$NetBSD: atomic_dec_64_nv_cas.c,v 1.3 2008/04/28 20:22:52 martin Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2007 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Jason R. Thorpe.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include "atomic_op_namespace.h"
     33 
     34 #include <sys/atomic.h>
     35 
     36 #ifdef __HAVE_ATOMIC64_OPS
     37 
     38 uint64_t
     39 atomic_dec_64_nv(volatile uint64_t *addr)
     40 {
     41 	uint64_t old, new;
     42 
     43 	do {
     44 		old = *addr;
     45 		new = old - 1;
     46 	} while (atomic_cas_64(addr, old, new) != old);
     47 
     48 	return (new);
     49 }
     50 
     51 #undef atomic_dec_64_nv
     52 atomic_op_alias(atomic_dec_64_nv,_atomic_dec_64_nv)
     53 
     54 #if defined(_LP64)
     55 #undef atomic_dec_ulong_nv
     56 atomic_op_alias(atomic_dec_ulong_nv,_atomic_dec_64_nv)
     57 __strong_alias(_atomic_dec_ulong_nv,_atomic_dec_64_nv)
     58 
     59 #undef atomic_dec_ptr_nv
     60 atomic_op_alias(atomic_dec_ptr_nv,_atomic_dec_64_nv)
     61 __strong_alias(_atomic_dec_ptr_nv,_atomic_dec_64_nv)
     62 #endif /* _LP64 */
     63 
     64 #endif
     65