Bluetooth: Host: Fix use of local variable as atomic target

In bt_conn_unref(), the local, non shared, variable "old"
is used as an atomic target:

    atomic_val_t old = atomic_dec(&conn->ref);
    conn = NULL;
    bool deallocated = (atomic_get(&old) == 1);

The above call to atomic_get() does not prevent any data race
or value obsolescence.
The resulting additional memory barrier does not seem necessary either.

If pedantic, one could also note that atomic_get() expects
an atomic_t* argument (target), not an atomic_val_t* (value).
This compiles and /works/ just fine since the Zephyr Atomic API defines
both to be the same integer type.
The equivalent C11 code, where _Atomic(T) and T are different types,
wouldn't compile.

Signed-off-by: Christophe Dufaza <[email protected]>

Author: dottspina

subsys/bluetooth/host/conn.c

@@ -1545,14 +1545,15 @@ void bt_conn_unref(struct bt_conn *conn)
 	conn_handle = conn->handle;
 
 	old = atomic_dec(&conn->ref);
-	/* Prevent from accessing connection object */
-	conn = NULL;
-	deallocated = (atomic_get(&old) == 1);
 
 	LOG_DBG("handle %u ref %ld -> %ld", conn_handle, old, (old - 1));
 
 	__ASSERT(old > 0, "Conn reference counter is 0");
 
+	/* Prevent from accessing connection object */
+	conn = NULL;
+	deallocated = ((old - 1) == 0);
+
 	/* Slot has been freed and can be taken. No guarantees are made on requests
 	 * to claim connection object as only the first claim will be served.
 	 */