CRYPTO_atomic_add(): use acquire release memory order rather than relaxed

For increments, the relaxed model is fine.  For decrements, it's
recommended to use the acquire release model.  We therefore go for the
latter.

Reviewed-by: Andy Polyakov <appro@openssl.org>

diff --git a/crypto/threads_pthread.c b/crypto/threads_pthread.c
index 72ea83892bbe66ca7fe725d4c006d74c1c385d55..9f4ae76bf85d61ec7997841c09049b6c8f5f8189 100644 (file)
--- a/crypto/threads_pthread.c
+++ b/crypto/threads_pthread.c
@@ -109,8 +109,8 @@ int CRYPTO_THREAD_compare_id(CRYPTO_THREAD_ID a, CRYPTO_THREAD_ID b)
 
 int CRYPTO_atomic_add(int *val, int amount, int *ret, CRYPTO_RWLOCK *lock)
 {
 
 int CRYPTO_atomic_add(int *val, int amount, int *ret, CRYPTO_RWLOCK *lock)
 {

-# if defined(__GNUC__) && defined(__ATOMIC_RELAXED)
-    *ret = __atomic_add_fetch(val, amount, __ATOMIC_RELAXED);
+# if defined(__GNUC__) && defined(__ATOMIC_ACQ_REL)
+    *ret = __atomic_add_fetch(val, amount, __ATOMIC_ACQ_REL);

 # else
     if (!CRYPTO_THREAD_write_lock(lock))
         return 0;
 # else
     if (!CRYPTO_THREAD_write_lock(lock))
         return 0;