sys/sys/refcount.h

   1 /*-
   2  * Copyright (c) 2005 John Baldwin <jhb@FreeBSD.org>
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the author nor the names of any co-contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * $FreeBSD: src/sys/sys/refcount.h,v 1.1 2005/09/27 18:01:33 jhb Exp $
  30  * $DragonFly: src/sys/sys/refcount.h,v 1.1 2008/06/26 23:06:52 dillon Exp $
  31  */
  32
  33 #ifndef __SYS_REFCOUNT_H__
  34 #define __SYS_REFCOUNT_H__
  35
  36 #include <machine/atomic.h>
  37
  38 static __inline void
  39 refcount_init(volatile u_int *count, u_int value)
  40 {
  41         *count = value;
  42 }
  43
  44 static __inline void
  45 refcount_acquire(volatile u_int *count)
  46 {
  47         atomic_add_acq_int(count, 1);
  48 }
  49
  50 static __inline int
  51 refcount_release(volatile u_int *count)
  52 {
  53         /* XXX: Should this have a rel membar? */
  54         return (atomic_fetchadd_int(count, -1) == 1);
  55 }
  56
  57 #endif  /* ! __SYS_REFCOUNT_H__ */