urcu/ref.h

   1 #ifndef _URCU_REF_H
   2 #define _URCU_REF_H
   3
   4 /*
   5  * Userspace RCU - Reference counting
   6  *
   7  * Copyright (C) 2009 Novell Inc.
   8  * Copyright (C) 2010 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   9  *
  10  * Author: Jan Blunck <jblunck@suse.de>
  11  *
  12  * This program is free software; you can redistribute it and/or modify it
  13  * under the terms of the GNU Lesser General Public License version 2.1 as
  14  * published by the Free  Software Foundation.
  15  */
  16
  17 #include <assert.h>
  18 #include <limits.h>
  19 #include <stdlib.h>
  20 #include <urcu/uatomic.h>
  21
  22 struct urcu_ref {
  23         long refcount; /* ATOMIC */
  24 };
  25
  26 static inline void urcu_ref_set(struct urcu_ref *ref, long val)
  27 {
  28         uatomic_set(&ref->refcount, val);
  29 }
  30
  31 static inline void urcu_ref_init(struct urcu_ref *ref)
  32 {
  33         urcu_ref_set(ref, 1);
  34 }
  35
  36 static inline void urcu_ref_get(struct urcu_ref *ref)
  37 {
  38         long old, _new, res;
  39
  40         old = uatomic_read(&ref->refcount);
  41         for (;;) {
  42                 if (old == LONG_MAX) {
  43                         abort();
  44                 }
  45                 _new = old + 1;
  46                 res = uatomic_cmpxchg(&ref->refcount, old, _new);
  47                 if (res == old) {
  48                         return;
  49                 }
  50                 old = res;
  51         }
  52 }
  53
  54 static inline void urcu_ref_put(struct urcu_ref *ref,
  55                                 void (*release)(struct urcu_ref *))
  56 {
  57         long res = uatomic_sub_return(&ref->refcount, 1);
  58         assert (res >= 0);
  59         if (res == 0)
  60                 release(ref);
  61 }
  62
  63 #endif /* _URCU_REF_H */