sys/sys/sysref2.h

   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