Possible Atomicity Violations in StreamSession and ThriftSessionManager

I'm developing a tool for atomicity violation detection and I think it have found two atomicity violations in cassandra.

In org.apache.cassandra.streaming.StreamSession there might be an atomicity violation in method addTransferFiles(), lines 310-314:

310:     StreamTransferTask task = transfers.get(cfId);
            if (task == null)
            {
                task = new StreamTransferTask(this, cfId);
314:         transfers.put(cfId, task);
            }

A concurrent thread can insert a transfer with the same uuid creating two StreamTransferTask, and only one get into "transfers".

In org.apache.cassandra.thrift.ThriftSessionManager, a simular situation can occur in method currentSession(), lines 57-61:

57:  ThriftClientState cState = activeSocketSessions.get(socket);
        if (cState == null)
        {
            cState = new ThriftClientState(socket);
51:       activeSocketSessions.put(socket, cState);
        }