From: Neil Horman <nhorman@openssl.org>
Date: Thu, 13 Feb 2025 20:52:16 +0000 (-0500)
Subject: Don't use __ATOMIC_ACQ_REL on older compilers
X-Git-Tag: openssl-3.3.4~169
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=74a52ca9b7934c100a055cf4a67782244568d36b;p=thirdparty%2Fopenssl.git

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)

(cherry picked from commit 7d284560a0624206356d46a948ab3a0b6f670c0e)
---

diff --git a/crypto/threads_pthread.c b/crypto/threads_pthread.c
index 8af2a504a3a..2e2e6121214 100644
--- a/crypto/threads_pthread.c
+++ b/crypto/threads_pthread.c
@@ -68,7 +68,6 @@
  * 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)
@@ -168,7 +167,6 @@ 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)
 
@@ -555,6 +553,10 @@ 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 =
@@ -565,13 +567,9 @@ 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 81fc4e80a00..0c2e5a6ff74 100644
--- a/crypto/threads_win.c
+++ b/crypto/threads_win.c
@@ -312,7 +312,10 @@ 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);
 
@@ -345,6 +348,9 @@ 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;
@@ -357,8 +363,9 @@ int ossl_rcu_call(CRYPTO_RCU_LOCK *lock, rcu_cb_fn cb, void *data)
     new->data = data;
     new->fn = cb;
 
-    InterlockedExchangePointer((void * volatile *)&lock->cb_items, prev);
-    new->next = prev;
+    new->next = lock->cb_items;
+    lock->cb_items = new;
+
     return 1;
 }