1 /* Copyright (c) 2015, Google Inc.
2 *
3 * Permission to use, copy, modify, and/or distribute this software for any
4 * purpose with or without fee is hereby granted, provided that the above
5 * copyright notice and this permission notice appear in all copies.
6 *
7 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
14
15 #include "internal.h"
16
17
18 #if defined(OPENSSL_C11_ATOMIC)
19
20 #include <assert.h>
21 #include <stdalign.h>
22 #include <stdatomic.h>
23 #include <stdlib.h>
24
25 #include <openssl/type_check.h>
26
27
28 /* See comment above the typedef of CRYPTO_refcount_t about these tests. */
29 static_assert(alignof(CRYPTO_refcount_t) == alignof(_Atomic CRYPTO_refcount_t),
30 "_Atomic alters the needed alignment of a reference count");
31 static_assert(sizeof(CRYPTO_refcount_t) == sizeof(_Atomic CRYPTO_refcount_t),
32 "_Atomic alters the size of a reference count");
33
34 static_assert((CRYPTO_refcount_t)-1 == CRYPTO_REFCOUNT_MAX,
35 "CRYPTO_REFCOUNT_MAX is incorrect");
36
CRYPTO_refcount_inc(CRYPTO_refcount_t * in_count)37 void CRYPTO_refcount_inc(CRYPTO_refcount_t *in_count) {
38 _Atomic CRYPTO_refcount_t *count = (_Atomic CRYPTO_refcount_t *) in_count;
39 uint32_t expected = atomic_load(count);
40
41 while (expected != CRYPTO_REFCOUNT_MAX) {
42 uint32_t new_value = expected + 1;
43 if (atomic_compare_exchange_weak(count, &expected, new_value)) {
44 break;
45 }
46 }
47 }
48
CRYPTO_refcount_dec_and_test_zero(CRYPTO_refcount_t * in_count)49 int CRYPTO_refcount_dec_and_test_zero(CRYPTO_refcount_t *in_count) {
50 _Atomic CRYPTO_refcount_t *count = (_Atomic CRYPTO_refcount_t *)in_count;
51 uint32_t expected = atomic_load(count);
52
53 for (;;) {
54 if (expected == 0) {
55 abort();
56 } else if (expected == CRYPTO_REFCOUNT_MAX) {
57 return 0;
58 } else {
59 const uint32_t new_value = expected - 1;
60 if (atomic_compare_exchange_weak(count, &expected, new_value)) {
61 return new_value == 0;
62 }
63 }
64 }
65 }
66
67 #endif /* OPENSSL_C11_ATOMIC */
68