Add support for reference counting using C11 atomics
Reviewed-by: Andy Polyakov <appro@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
GH: #1500
diff --git a/include/internal/refcount.h b/include/internal/refcount.h
new file mode 100644
index 0000000..b83e05c
--- /dev/null
+++ b/include/internal/refcount.h
@@ -0,0 +1,65 @@
+/*
+ * Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the OpenSSL license (the "License"). You may not use
+ * this file except in compliance with the License. You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+#ifndef HEADER_INTERNAL_REFCOUNT_H
+# define HEADER_INTERNAL_REFCOUNT_H
+
+# if __STDC_VERSION__ >= 201112L && !defined(__STDC_NO_ATOMICS__)
+# include <stdatomic.h>
+# define HAVE_C11_ATOMICS
+# endif
+
+# if defined(HAVE_C11_ATOMICS) && ATOMIC_INT_LOCK_FREE > 0
+
+# define HAVE_ATOMICS 1
+
+typedef _Atomic int CRYPTO_REF_COUNT;
+
+static ossl_inline int CRYPTO_UP_REF(_Atomic int *val, int *ret, void *lock)
+{
+ *ret = atomic_fetch_add_explicit(val, 1, memory_order_relaxed) + 1;
+ return 1;
+}
+
+static ossl_inline int CRYPTO_DOWN_REF(_Atomic int *val, int *ret, void *lock)
+{
+ *ret = atomic_fetch_sub_explicit(val, 1, memory_order_release) - 1;
+ if (*ret == 0)
+ atomic_thread_fence(memory_order_acquire);
+ return 1;
+}
+
+# elif defined(__GNUC__) && defined(__ATOMIC_RELAXED) && __GCC_ATOMIC_INT_LOCK_FREE > 0
+
+# define HAVE_ATOMICS 1
+
+typedef int CRYPTO_REF_COUNT;
+
+static ossl_inline int CRYPTO_UP_REF(int *val, int *ret, void *lock)
+{
+ *ret = __atomic_fetch_add(val, 1, __ATOMIC_RELAXED) + 1;
+ return 1;
+}
+
+static ossl_inline int CRYPTO_DOWN_REF(int *val, int *ret, void *lock)
+{
+ *ret = __atomic_fetch_sub(val, 1, __ATOMIC_RELEASE) - 1;
+ if (*ret == 0)
+ __atomic_thread_fence(__ATOMIC_ACQUIRE);
+ return 1;
+}
+
+# else
+
+typedef int CRYPTO_REF_COUNT;
+
+# define CRYPTO_UP_REF(val, ret, lock) CRYPTO_atomic_add(val, 1, ret, lock)
+# define CRYPTO_DOWN_REF(val, ret, lock) CRYPTO_atomic_add(val, -1, ret, lock)
+
+# endif
+#endif
