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 * $FreeBSD$ 30 */ 31 32 #ifndef __SYS_REFCOUNT_H__ 33 #define __SYS_REFCOUNT_H__ 34 35 #include <machine/atomic.h> 36 37 #ifdef _KERNEL 38 #include <sys/systm.h> 39 #else 40 #define KASSERT(exp, msg) /* */ 41 #endif 42 43 static __inline void 44 refcount_init(volatile u_int *count, u_int value) 45 { 46 47 *count = value; 48 } 49 50 static __inline void 51 refcount_acquire(volatile u_int *count) 52 { 53 54 atomic_add_acq_int(count, 1); 55 } 56 57 static __inline int 58 refcount_release(volatile u_int *count) 59 { 60 u_int old; 61 62 /* XXX: Should this have a rel membar? */ 63 old = atomic_fetchadd_int(count, -1); 64 KASSERT(old > 0, ("negative refcount %p", count)); 65 return (old == 1); 66 } 67 68 #endif /* ! __SYS_REFCOUNT_H__ */ 69