1 /* 2 * Copyright (c) 2007 The DragonFly Project. All rights reserved. 3 * 4 * This code is derived from software contributed to The DragonFly Project 5 * by Matthew Dillon <dillon@backplane.com> 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in 15 * the documentation and/or other materials provided with the 16 * distribution. 17 * 3. Neither the name of The DragonFly Project nor the names of its 18 * contributors may be used to endorse or promote products derived 19 * from this software without specific, prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * $DragonFly: src/sys/sys/sysref2.h,v 1.2 2007/05/06 19:23:33 dillon Exp $ 35 */ 36 /* 37 * System resource registration, reference counter, and allocation 38 * management subsystem. 39 * 40 * All major system resources use this structure and API to associate 41 * a machine-unique sysref with a major system resource structure, to 42 * reference count that structure, to register the structure and provide 43 * a dictionary lookup feature for remote access, and to provide an 44 * allocation and release backend. 45 */ 46 47 #ifndef _SYS_SYSREF2_H_ 48 #define _SYS_SYSREF2_H_ 49 50 #ifndef _SYS_SYSREF_H_ 51 #include <sys/sysref.h> 52 #endif 53 #ifndef _MACHINE_ATOMIC_H_ 54 #include <machine/atomic.h> 55 #endif 56 57 void _sysref_put(struct sysref *); 58 59 /* 60 * Normally only 1+ transitions can occur. Note that a negative ref count 61 * is used as a marker to indicate that a structure is undergoing deletion 62 * and that temporary refs during the process of deletion may occur. 63 * 64 * The get interface is the primary reference counting interface. 65 */ 66 static __inline 67 void 68 sysref_get(struct sysref *sr) 69 { 70 atomic_add_int(&sr->refcnt, 1); 71 } 72 73 /* 74 * 1->0 transitions, and transitions occuring with negative ref counts, 75 * require special handling. All other transitions can be done with a 76 * trivial locked bus cycle. 77 */ 78 static __inline 79 void 80 sysref_put(struct sysref *sr) 81 { 82 int count = sr->refcnt; 83 84 if (count <= 1 || atomic_cmpset_int(&sr->refcnt, count, count - 1) == 0) 85 _sysref_put(sr); 86 } 87 88 /* 89 * Return true of the object is fully active 90 */ 91 static __inline 92 int 93 sysref_isactive(struct sysref *sr) 94 { 95 return(sr->refcnt > 0); 96 } 97 98 /* 99 * Return true of the object is being deactivated 100 */ 101 static __inline 102 int 103 sysref_isinactive(struct sysref *sr) 104 { 105 return(sr->refcnt <= 0); 106 } 107 108 /* 109 * Return true if we control the last deactivation ref on the object 110 */ 111 static __inline 112 int 113 sysref_islastdeactivation(struct sysref *sr) 114 { 115 return(sr->refcnt == -0x40000000); 116 } 117 118 #ifdef _KERNEL 119 120 void sysref_init(struct sysref *sr, struct sysref_class *); 121 void *sysref_alloc(struct sysref_class *class); 122 void sysref_activate(struct sysref *); 123 124 #endif 125 126 #endif 127