Don't use __ATOMIC_ACQ_REL on older compilers

Older compilers don't always support __ATOMIC_ACQ_REL, use a lock where
they don't

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
(Merged from https://github.com/openssl/openssl/pull/26747)

diff --git a/crypto/threads_pthread.c b/crypto/threads_pthread.c
index 116603652a15b1b78dd3f6e0bab2a41baa4b156f..4d2e1e125e9c21329f5a60a362310e9519e08815 100644 (file)
--- a/crypto/threads_pthread.c
+++ b/crypto/threads_pthread.c
@@ -90,7 +90,6 @@ __tsan_mutex_post_lock((x), 0, 0)
  * fallback function names.
  */
 typedef void *pvoid;
-typedef struct rcu_cb_item *prcu_cb_item;
 
 # if defined(__GNUC__) && defined(__ATOMIC_ACQUIRE) && !defined(BROKEN_CLANG_ATOMICS) \
     && !defined(USE_ATOMIC_FALLBACKS)
@@ -193,7 +192,6 @@ IMPL_fallback_atomic_store(pvoid)
         return ret;                                                     \
     }
 IMPL_fallback_atomic_exchange_n(uint64_t)
-IMPL_fallback_atomic_exchange_n(prcu_cb_item)
 
 #  define ATOMIC_EXCHANGE_N(t, p, v, o) fallback_atomic_exchange_n_##t(p, v)
 
@@ -583,6 +581,10 @@ void ossl_synchronize_rcu(CRYPTO_RCU_LOCK *lock)
     }
 }
 
+/*
+ * Note: This call assumes its made under the protection of
+ * ossl_rcu_write_lock
+ */
 int ossl_rcu_call(CRYPTO_RCU_LOCK *lock, rcu_cb_fn cb, void *data)
 {
     struct rcu_cb_item *new =
@@ -593,13 +595,9 @@ int ossl_rcu_call(CRYPTO_RCU_LOCK *lock, rcu_cb_fn cb, void *data)
 
     new->data = data;
     new->fn = cb;
-    /*
-     * Use __ATOMIC_ACQ_REL here to indicate that any prior writes to this
-     * list are visible to us prior to reading, and publish the new value
-     * immediately
-     */
-    new->next = ATOMIC_EXCHANGE_N(prcu_cb_item, &lock->cb_items, new,
-                                  __ATOMIC_ACQ_REL);
+
+    new->next = lock->cb_items;
+    lock->cb_items = new;
 
     return 1;
 }

diff --git a/crypto/threads_win.c b/crypto/threads_win.c
index 258b7a59c7746a2ac1c106a0a20a4e8be962c33c..492e940f3eec803528bb20c5e63ba32e89586de1 100644 (file)
--- a/crypto/threads_win.c
+++ b/crypto/threads_win.c
@@ -365,8 +365,10 @@ void ossl_synchronize_rcu(CRYPTO_RCU_LOCK *lock)
     struct rcu_cb_item *cb_items, *tmpcb;
 
     /* before we do anything else, lets grab the cb list */
-    cb_items = InterlockedExchangePointer((void * volatile *)&lock->cb_items,
-                                          NULL);
+    ossl_crypto_mutex_lock(lock->write_lock);
+    cb_items = lock->cb_items;
+    lock->cb_items = NULL;
+    ossl_crypto_mutex_unlock(lock->write_lock);
 
     qp = update_qp(lock, &curr_id);
 
@@ -399,6 +401,9 @@ void ossl_synchronize_rcu(CRYPTO_RCU_LOCK *lock)
 
 }
 
+/*
+ * Note, must be called under the protection of ossl_rcu_write_lock
+ */
 int ossl_rcu_call(CRYPTO_RCU_LOCK *lock, rcu_cb_fn cb, void *data)
 {
     struct rcu_cb_item *new;
@@ -409,8 +414,9 @@ int ossl_rcu_call(CRYPTO_RCU_LOCK *lock, rcu_cb_fn cb, void *data)
     new->data = data;
     new->fn = cb;
 
-    new->next = InterlockedExchangePointer((void * volatile *)&lock->cb_items,
-                                           new);
+    new->next = lock->cb_items;
+    lock->cb_items = new;
+
     return 1;
 }