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 #define REFCNTF_WAITING 0x40000000 39 40 void _refcount_wait(volatile u_int *countp, const char *wstr); 41 int _refcount_release_wakeup(volatile u_int *countp); 42 43 static __inline void 44 refcount_init(volatile u_int *countp, u_int value) 45 { 46 *countp = value; 47 } 48 49 static __inline void 50 refcount_acquire(volatile u_int *countp) 51 { 52 atomic_add_acq_int(countp, 1); 53 } 54 55 static __inline int 56 refcount_release(volatile u_int *countp) 57 { 58 return (atomic_fetchadd_int(countp, -1) == 1); 59 } 60 61 /* 62 * Release a refcount and also handle waiters who have (atomically) 63 * set the REFCNTF_WAITING flag. If the flag was set the atomic op 64 * will fail (because the 'old' value we pass it is with the flag 65 * cleared). The atomic op can also fail on a race so the helper 66 * function deals with all cases. 67 * 68 * This function returns TRUE(1) on the last release and FALSE(0) otherwise. 69 */ 70 static __inline int 71 refcount_release_wakeup(volatile u_int *countp) 72 { 73 u_int n = *countp & ~REFCNTF_WAITING; 74 if (!atomic_cmpset_int(countp, n, n - 1)) 75 return(_refcount_release_wakeup(countp)); 76 return(n == 1); 77 } 78 79 /* 80 * Wait for all refs on *countp to go away. 81 * 82 * WARNING! If this function is used then all releases on countp MUST 83 * use refcount_release_wakeup() instead of refcount_release(). 84 */ 85 static __inline void 86 refcount_wait(volatile u_int *countp, const char *wstr) 87 { 88 if (*countp) 89 _refcount_wait(countp, wstr); 90 } 91 92 #endif /* ! __SYS_REFCOUNT_H__ */ 93