diff options
author | Adam Langley <alangley@gmail.com> | 2015-05-15 22:01:29 +0300 |
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committer | Adam Langley <agl@google.com> | 2015-05-20 22:14:59 +0300 |
commit | 6f2e733bab69a5c853a929a96671736458b8d4c1 (patch) | |
tree | efbff366b0b384afc15bc85a6d52868ea8f43078 /crypto/refcount_c11.c | |
parent | daaff93464f79b9f1f06cac39d56125892280ee9 (diff) |
Add infrastructure for reference counts.
OpenSSL has traditionally done reference counting with |int|s and the
|CRYPTO_add| function. Unless a special callback is installed (rare),
this is implemented by doing the reference count operations under a
lock.
This change adds infrastructure for handling reference counts and uses
atomic operations when C11 support is available.
Change-Id: Ia023ce432319efd00f77a7340da27d16ee4b63c3
Reviewed-on: https://boringssl-review.googlesource.com/4771
Reviewed-by: Adam Langley <agl@google.com>
Diffstat (limited to 'crypto/refcount_c11.c')
-rw-r--r-- | crypto/refcount_c11.c | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/crypto/refcount_c11.c b/crypto/refcount_c11.c new file mode 100644 index 00000000..a77473f7 --- /dev/null +++ b/crypto/refcount_c11.c @@ -0,0 +1,65 @@ +/* Copyright (c) 2015, Google Inc. + * + * Permission to use, copy, modify, and/or distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY + * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION + * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN + * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ + +#include "internal.h" + + +#if defined(OPENSSL_C11_ATOMIC) + +#include <assert.h> +#include <stdalign.h> +#include <stdatomic.h> +#include <stdlib.h> + +#include <openssl/type_check.h> + + +/* See comment above the typedef of CRYPTO_refcount_t about these tests. */ +static_assert(alignof(CRYPTO_refcount_t) == alignof(_Atomic CRYPTO_refcount_t), + "_Atomic alters the needed alignment of a reference count"); +static_assert(sizeof(CRYPTO_refcount_t) == sizeof(_Atomic CRYPTO_refcount_t), + "_Atomic alters the size of a reference count"); + +static_assert((CRYPTO_refcount_t)-1 == CRYPTO_REFCOUNT_MAX, + "CRYPTO_REFCOUNT_MAX is incorrect"); + +void CRYPTO_refcount_inc(CRYPTO_refcount_t *count) { + uint32_t expected = atomic_load(count); + + while (expected != CRYPTO_REFCOUNT_MAX) { + uint32_t new_value = expected + 1; + if (atomic_compare_exchange_weak(count, &expected, new_value)) { + break; + } + } +} + +int CRYPTO_refcount_dec_and_test_zero(CRYPTO_refcount_t *count) { + uint32_t expected = atomic_load(count); + + for (;;) { + if (expected == 0) { + abort(); + } else if (expected == CRYPTO_REFCOUNT_MAX) { + return 0; + } else { + const uint32_t new_value = expected - 1; + if (atomic_compare_exchange_weak(count, &expected, new_value)) { + return new_value == 0; + } + } + } +} + +#endif /* OPENSSL_C11_ATOMIC */ |