6f2e733bab
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>
66 lines
2.1 KiB
C
66 lines
2.1 KiB
C
/* 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 */
|