1 /*
2 * Copyright (c) 2020 François Tigeot <ftigeot@wolfpond.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 unmodified, this list of conditions, and the following
10 * disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27 #ifndef _LINUX_REFCOUNT_H_
28 #define _LINUX_REFCOUNT_H_
29
30 #include <linux/atomic.h>
31 #include <linux/mutex.h>
32 #include <linux/spinlock.h>
33 #include <linux/kernel.h>
34
35 typedef struct refcount_struct {
36 atomic_t refs;
37 } refcount_t;
38
39 #define REFCOUNT_SATURATED (INT_MIN / 2)
40
41 static inline void
refcount_set(refcount_t * r,unsigned int n)42 refcount_set(refcount_t *r, unsigned int n)
43 {
44 atomic_set(&r->refs, n);
45 }
46
47 static inline bool
refcount_dec_and_test(refcount_t * r)48 refcount_dec_and_test(refcount_t *r)
49 {
50 return atomic_dec_and_test(&r->refs);
51 }
52
53 static inline void
refcount_inc(refcount_t * r)54 refcount_inc(refcount_t *r)
55 {
56 int old_value = atomic_fetchadd_int(&r->refs.counter, 1);
57
58 if (old_value <= 0)
59 refcount_set(r, REFCOUNT_SATURATED);
60 }
61
62 #endif /* _LINUX_REFCOUNT_H_ */
63